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SL1

FUTURE DEVELOPMENTS OF (POLYMERIC) MATERIALS

I. ČATIĆ

To pose a question about future developments of (polymeric) materials means to answer the question of future development of Materials (Polymeric) Technology. The syntagm Materials Technology is a common nominator for Material Technology and Production Technology. Material Technology means the production and application of materials based on achievements of natural sciences: physics, chemistry and even biology. The aim of Material Technology is production of substances or materials with the prescribed production and application properties and the aim of Production Technology making of product with defined geometrical shape and necessary properties during its service life. The main issue in this discussion is whether we can predict the future of Materials Technology. We assume that the answer is positive, based on two analyses, fractal past and the future of general technology and systemic analysis. We use a brief fractal history of general technology to predict the future of two human technologies: biotechnology and technology of non-living things. From the description of natural and artificial technology we can conclude the following. Even if more parts are made by artificial micro-technological and nano-technological processes (level of atoms), in the very far future the products will be mostly of macro geometrical size. Thus, our prediction is that once developed the production process can be only innovatively improved whereas the development of materials can be revolutionary. The revolutionary development of (polymeric) materials means going to level n-1, the subatomic one.

SL2

New polymeric materials: Problems in the performance and durability determination

J. Pospíšil, J. Pilař, Z. Horák

Requirements of customers on properties of polymeric materials have a Janus head: new polymer-based products have to fit expected mechanical and physical properties on one side, and have a suggested long-term performance at specific application environment on the other. Producers offer materials based on a single polymer, polymer blend, filled system, etc. There is a political pressure to enhance the use of materials based on recyclates. All of the systems have a different response to hostile environment. To fulfill conditions of customer requirements, most of the materials must be stabilized. The assessment of changes in material performance due to degradation should be based on methods allowing to correlate laboratory (accelerated) aging results with real lifetime at field conditions and enabling some acceptable approaches to lifetime prediction. The onset of the polymer failure and its long-term development are based on heterogeneous changes in morphology, molecular mass, content of oxygenated structures, efficiency and consumption of stabilizers etc., i.e., on concentration gradients in these changes. This can be observed by methods providing a reasonable correlation of analytical data with material changes. The methods and their combinations allowing to determine with enhanced confidence the heterogeneity of material changes arising in processing, long-term heat aging and weathering are discussed.

Support from the Grant Agency of the Czech Republic (projects 203/02/1243 and 106/04/1118) is acknowledged.

SL3

STRUCTURE-PROPERTIES RELATIONSHIP IN CHLORINATED POLYETHYLENE

K. MAROSSY, A. TÓTH

Chlorinated polyethylene (CPE) is known as the oldest impact modifier of PVC. It is also used in the rubber industry for producing special elastomers by cross-linking.

The chlorination can be carried out in homogenous or heterogeneous technology, or by the combination of mentioned processes.

Our, since 1979 patented technology is realised in aqueous suspension, therefore the reaction isheterogeneous one. The situation is more involved, because the polyethylene (PE) is itself a two-phase system, having crystalline and amorphous regions.

BorsodChem Rt. has three basic types; ONGRO CPE^® 3602N, 3602C, and 4002N.

A random substitution is supposed although a chlorine atom already present on the chain has some directing effect on the further reaction. According to our present knowledge CPE has no crystalline structure of its own only residual crystallinity in the CPE resin originating from unchanged polyethylene chains or segments. Product development requested the structural investigation of CPE, in particular in point of view process conditions. There were used physical methods, DSC, DMA, TSD and X-ray diffraction.

It has been found that the properties of raw material polyethylene are deterministic.

Chlorine distribution (homogenous or blocky) and the amorphous crystalline ratio can be regulated by the chlorination conditions; temperature profile, chlorination rate, etc.

CPE as a halogen containing polymer has limited thermal stability. As the result of our research work a new product range of improved heat stability has been developed.

On the basis of non-uniform chlorine distribution CPE is -technologically compatible with a large number of other polymers. This, so called segment level compatibility makes the CPE an ideal blending or compatibilizing agent in the field of thermoplastic elastomers and polymer alloys, even in recycling technologies.

SL4

Multiscale Characterization of the Dispersion of Clay Particles in Polymer-Clay Nanocomposites

A. Vermogen^a, K. Masenelli-Varlot^a, B. Sixou^a, G. Vigier^a, J. Duchet^b, R. Séguéla^a, J.F.Gérard^b

Polymer Layered Silicate Nanocomposites have drawn a great interest in polymer science these last years. It has clearly been shown that the properties achieved by nanocomposites are often related to their structures and to the states of dispersion of the silicate particles (tactoids) in the polymer matrix. Comprehension of the complex mechanism of dispersion and exfoliation of the clay tactoids is of real interest, since it may allow us to better control the final morphology and the homogeneity of clay nanocomposites, and thus their macroscopic properties. It is important to note that these layered silicate systems cannot be reliably described with Transmission Electron Microscopy or Wide Angle X-Ray Diffraction by themselves. As a consequence, methodologies based on rheological, Nuclear Magnetic Resonance, Small Angle X-ray Scattering and Particle Analysis by Transmission Electron Microscopy have recently been developed.

In this study, we propose a multi-scale characterization of the exfoliation state by Transmission Electron Microscopy and Optical Microscopy followed by Image Analysis. The parameters obtained give a lot of pieces of information and allow a very fine description of the microstructure, other than the over-simple designation as "exfoliated" or "intercalated". The average thicknesses, lengths and aspect ratios of each class of tactoids are measured, as well as their relative proportions and the average distances between two adjacent tactoids.

Complementary experiments by Small Angle X-Ray Scattering also allows us to measure the thickness distribution of the tactoids (less than 50 nm thick). Comparison of the Image Analysis data and the SAXS data show a good convergence of the thickness distribution. This shows that the characterization of the dispersion of clay in these nanocomposites has to be carried out by several complementary techniques and at different scales.

SL5

The role of reactive modifiers in the transition from micro- to nanostructured polymer composites

V. Khunová^a, I. Kelnar^b, C.M. LIauw^c

The paper explores how reactive modification can be applied with substantial effectiveness to both micro and nano-structured melt blended polymer composites. Reactive processing of polymer micro-composites has been studied using nonpolar (polypropylene homopolymer) and polar (polyamide 6) polymer matrix in combination with an untreated montmorillonite (MMT) and a several of organically modified layered silicates (OLS) of differing quarternary ammonium intercalant (Cloisiste 30 B, Cloisite 15 A, Nanomer.30TC, Nanofil 50).

In micro-structured composites it has been shown that 1,3-phenylene dimaleimide (BMI) is a very effective reactive interphase modifier for PP and PA 6/MMT. In many examples mechanical properties were significantly improved relative to the respective unmodified composites.

In the second part of presentation the attention will be focused on the use of BMI as an agent for the reactive melt intercalation-exfoliation of OLS. In PP composites, the positive role of BMI in both, the exfoliation of clay platelets and promotion of strong interfacial adhesion together with better filler dispersion was confirmed. In PA6/OMMT nanocomposites BMI enhances mechanical behaviour. especially toughness. It is highly likely that combination of interfacial modification and modification of the bulk matrix are the key factors behind the effectiveness of BMI in this role.

Acknowledgement

The work was supported by the Scientific Grant Agency of the Ministry of Education of Slovak Republic VEGA 1/2110/05 and by the Grant Agency of the Czech Republic (N⁰. 106/03/0679)

SL6

BARRIER PROPERTIES OF POLYMER/LAYERED SILICATE NANOCOMPOSITES: AN EXAMPLE OF SPECIFIC RESULTS

R. WACHE^a,b, M-H. KLOPFFER^a, M. MOAN^b

A lot of current studies deal with the enhancement of physical properties that are achieved with nanocomposites compared to the neat matrix or to conventionally filled polymers systems^1,2. Exfoliation of the clay platelets in the polymer matrix is often considered as the key parameter which will greatly modify the properties. It is true that the smaller the filler is, the larger the interactions are for a given filler fraction. For example, a decrease in the coefficient of permeability has been many times reported^3-6 and this enhancement of the barrier properties have been explained through a tortuous effect because the layered silicates present a very high aspect ratio^7-9. In this case, exfoliation largely affects the apparent shape factor of the particules.

The aim of this work is to show that exfoliation of the clay doesn't necessarily lead to the enhancement of all the properties. The exfoliation of the clay has been proved by various technics such as XRD, TEM and rheological measurements. However the nanocomposite does not exhibit good barrier properties. Several assumptions have been made to explain this phenomen. One of these ideas have been used in simple equations to simulate the barrier properties.

[1] Fukushima Y., Inagaki S. (1987) Synthesis of an intercalated compound of montmorillonite and 6-polyamide. J. of Inclusion Phenomena, 5, p 473-482.

[2] Vaia R.A., Ishii H., Giannelis E.P. (1993) Synthesis and properties of two-dimensional nanostructures by direct intercalation of polymer melts in layered silicates. Chem. Mater., 5, p 1694-1696.

[3] Messersmith P.B., Giannelis E.P. (1995) Synthesis and barrier properties of poly(e-caprolactone)-layered silicate nanocomposites. J. Polym. Sci., Part A, 33, p 1047-1057.

[4] Yano K., Usuki A., Okada A. (1997) Synthesis and properties of polyimide-clay hybrid films. J. Polym. Sci., Part A, 35, p 2289-2294.

[5] Gorrasi G., Tortora M., Vittoria V., Pollet E., Lepoittevin B., Alexandre M., Dubois P. (2003) Vapor properties of polycaprolactone montmorillonite nanocomposites: effect of clay dispersion. Polymer, 44(8), p 2271-2279.

[6] Klopffer M.-H., Waché R., Flaconnèche B., Vinciguerra E., Gonzalez S. (2002) Polymer clay nanocomposites for the enhancement of barrier properties to organic fluids. Proc. Nanocomposites 2002, San Diego.

[7] Nielsen L.E. (1967) Models for the permeability of filled polymer systems. J. Macromol. Sci., 5(A1), p 929-942.

[8] Fredrickson G.H., Bicerano J. (1999) Barrier properties of oriented disk composites. J. Chem. Phys., 110(4), p 2181-2188.

[9] Bharadwaj R.K. (2001) Modeling the barrier properties of polymer-layered silicates nanocomposites. Macromol., 34, p 9189-9192.

SL7

TRENDS IN POLYPYRROLE RESEARCH: CONDUCTIVITY ENHANCEMENT IN RAW MATERIALS AND DISPERSIONS

J. A. POMPOSO, E. OCHOTECO, C. POZO, P. CARRASCO, H. GRANDE, J. RODRIGUEZ

Polypyrrole (PPy) is a well-established material in industrial applications such as through-hole metallization of multilayer printed circuit boards (PCBs) or in military applications such as radar camouflage textiles. Current applications in development for PPy raw materials and dispersions are Electromagnetic Interference (EMI) shielding cans for mobile telecommunications devices and all-plastic circuits for the emerging field of Organic Electronics. For such applications, an enhancement of the electrical conductivity of PPy is the key for industrial success.

In this paper we will show that raw PPy of high conductivity (>150 S/cm) can be obtained in very good yield (>90%) by appropriate selection of both bifunctional additives and reaction conditions to increase the oxidative polymerization rate of pyrrole. The presence of new active centres for the polymerisation is demonstrated by UV measurements. In addition, raw PPy synthesized according to the improved method of synthesis shows good stability of the conductivity upon aging at high temperature (150 ºC) in air.

FIG. 1. Direct metallization of plastics with PPy paints. From left to right: (a) raw ABS, (b) PPy painted ABS, (c) Cu-metallization of PPy painted smooth surface ABS, (d) Cu-metallization of PPy painted rough surface ABS.

Finally, we report new nm in size PPy dispersions obtained by sonochemical synthesis that can be incorporated into conventional plastic paints for direct metallization of plastics (Fig. 1). The conductivity of the new metallization paint developed was 0.4 S/cm with a PPy content of 10 wt %.

SL8

NANOSCALE ELECTROACTIVE COMPOSITE MATERIALS ON THE BASIS OF POROUS POLYMER FILMS

G. ELYASHEVICH, M. SMIRNOV, I. KURYNDIN, I. DMITRIEV

Electroconducting conjugated polymers appear very attractive for use in sensors, actuators and membranes as sensitive components or as matrix for easy modification of specific substrates. Tremendous advances made during the past decade in the chemistry, physics and processing of these polymers provide a broad foundation for future studies and technological application. The future in technology depends on determination of factors responsible for promoting higher conductivity, greater thermal stability and use of composites of conducting polymers with conventional polymers to exploit the most attractive features of each. In these composites the conventional polymer support or matrix provides desired mechanical strength and elasticity, and electroconducting polymer acts as an active component.

New composite electroactive materials have been elaborated by the formation of conducting polymer layers (polyaniline, polypyrrole) onto polyethylene porous films. Structure of these films may be described as a system of the large lamellar crystals of 40 nm in size disposed parallel to each other with intercrystalline spaces of 10 nm between them. The film contains pores and through flow channels having the sizes from 50 to 500 nm. Conducting phase is prepared by oxidative polymerization of monomer on the surface and in the volume of the film providing composites a surface and volume conductivity. In result of conducting polymer layer deposition on the walls of pores the nanotubes of this polymer connecting two film surfaces are formed inside the pores. Electric, mechanical, membrane-separation and thermodeformational properties of composites are determined by the space continuous phase of conducting polymer inside the porous support.

The work is supported by Russian Foundation of Basic Research (Grant № 04-03-32229), by the Programme for Basic Research, Russian Academy of Sciences, Division of Chemistry and Material Sciences, "Synthesis and Investigations of New Polymer Systems Containing Polyconjugated Polymers and Possessing Semiconducting and Conducting Properties".

SL9

Cold-Plasma Graft polymerization of Organophosphorus materials on polymer surfaces: A New route to flame retard Polymers

C. Jama¹, I. Errifai¹, R. Delobel¹, R. De jaeger² and A. Mazzah²

A major trend in modern fire retardancy of polymers is the reduction and substitution of problematic compounds. One way is the replacement with ecological friendly fire retardants. Analogously, an advanced concept could be formulated for polymeric materials by concentrating the fire retardancy at the interface between pyrolysis zone and gas phase. The materials surface is identified as key position.

It is now well established that exposing polymeric substrates to cold-plasma species represents an unusually convenient and versatile surface-modification and coating technology.

Plasma polymerization of either ethylene glycol methacrylate phosphate or vinyl phosphonic acid results in the formation of layers containing structural unit from monomer species. XPS, ³¹P solid-NMR and ATR-IR spectroscopy indicate the presence of phosphoryl moieties within plasma formed polymer structure. The thermal stability analysis gives evidence that these layers are very thermally stable. The flame retardancy behavior of coated polyamide 6 was enhanced in comparison to virgin, an increase of the limiting oxygen index was evidenced and a V0 rating is obtained using UL 94 test. The increase in term of flame retardancy and thermal stability of coated-PA6 was explained by the formation of a highly cross-linked barrier layer covalently bonded to the substrate.

SL10

A Novel class of hybrid polysaccharide-silica nanocomposite materials fabricated by sol-gel technique

Yu. A. Shchipunov

A developed approach is based on a novel silica precursor that is completely compatible with polysaccharides in aqueous solutions. Their mixing does not cause a phase separation or precipitation. Most of practically important polysaccharides were involved in the synthesis to prepare hydrogels. They had an accelerating and catalytic effects on the sol-gel processing, providing the synthesis at conditions at which it was not took place in the absence of polysaccharides.

Hydrogels, xerogels and aerogels were fabricated to study the properties and structure of nanocomposite materials. It was done with the help of a dynamic rheology, differential scanning calorimetry, scanning electron microscopy and atomic force microscopy. It was found that the polysaccharides served as a template for silica generated in situ by the sol-gel processing. Carbohydrate macromolecules were covered by an inorganic shell owing to silica nucleation and precipitation. Therefore, the hybrid polysaccharide-silica materials consisted usually of cross-linked fibrils that formed a three-dimensional network. This determined the properties of nanocomposites. The polysaccharides made them softer, less rigid and brittle, whereas an increase of silica amount resulted in grow of nanocomposite hardness and brittleness. Such polysaccharides as kappa- and iota-carrageenans, which experience a reversible coil-to-double helix transition with varying the temperature, provided a thermoreversible change in the mechanical properties of hybrid materials around their phase transition temperature.

The structure of nanocomposites was regulated by the polysaccharide type, charge and concentration. As usual mesoporous materials were synthesized. A difference was found for cyclodextrin-containing nanocomposites. These polysaccharides provided the formation of micropores the dimension of which correlated with outer diameter of carbohydrate macromolecules.

It was demonstrated that the developed hybrid polysaccharide-silica nanocomposite materials are ideally suited for the enzyme immobilization and fabrication of biocatalysts. Their main advantage over current techniques lies in that the entrapment conditions are dictated by an enzyme, but not the sol-gel processing. This allowed immobilizing very labile proteins that loose their activity in the solution even at appropriate conditions within few hours. After the entrapment into the hybrid silica matrix, it was active for a few months.

SL11

GLYCOLYSIS OF WASTE POLYURETHANE FOAMS AND ELASTOMERS UNDER VARIOUS REACTION CONDITIONS TO FIND THE ADEQUATE METHOD

M.M. ALAVI NIKJE*¹, M. HAGHSHENAS², A. BAGHERI GARMARUDI², N. BARZANDE³, K. TAHERI³

Since the use of polyurethane is steadily increasing, the demand for enhancing the producing efficiency grows. At the same time higher environmental standards must be met. In order to cope with these initially contradictory requirements, our research and development group has made a big step ahead.

Based on the fact that a huge part of the raw material already becomes waste during the production as i.e. cut offs, remaining in drains and vents of molds…, what is more obvious that just taking exactly this material and the purchase of base material will be reduced while keeping the same production output. In Iran, about 200,000 tons of polyurethane resins are processed in the form of hard, soft, and semi-hard urethane foams, elastomers, and Reaction Injection Moldings (RIM), and are used in various fields. Recently, public awareness of environmental protection have been heightened in all over the world, and under such a situation, studies to develop processes for recycling various kinds of plastics, including polyurethane resins, have been carried out. Waste polyurethane foams and elastomers, with a glycolysis process can be produced as a liquid which contains hydrogen active group and is usable in foam and elastomer formulating. There are so many solvent systems and catalysts to be used in this process. Various catalysts and glycolysis temperatures were employed to find an acceptable result in dissolution time. The polymer / solvent ratio was discussed and the product is analyzed to find the best process condition. The product of progressed reaction was so tested in PU injection machine in order to insure the method and physical properties of produced foams and elastomers was compared to virgin systems.

SL12

CONCURRENCE OF CAVITATION AND SHEAR MECHANISMS IN THE PLASTIC DEFORMATION OF SOLID POLYMERS

Ch. G'SELL

Analysis of plastic behaviour of solid polymer is de facto based on the assumption that physical mechanisms of deformation are isochoric (proceed at constant volume). This is in line with a generally admitted statement that the participation of cavitation mechanisms is globally negligible with respect to shear mechanisms.

This paradigm seems to ignore the recurrent observation of voids in deformed samples (crazes, pores, decohesion, nodule implosion, etc) and even the occurrence of deformation whitening that constitutes an evident of deformation damage visible at naked eye.

The reason of this contradiction is the absence, until a recent past, of simple and quantitative techniques to assess volume changes during deformation of materials. As such, existing methods (variation of Young's modulus, determination of post-mortem density, etc.) are either indirect or lacking precision.

Thanks to a novel system recently developed in Nancy (VidéoTraction), we are now capable to access during a tensile test to : i) axial true stress / axial true strain curves at constant true strain rate and ii) volume strain / axial true strain. Furthermore, all above variables are determined in real time in the same representative volume element of the tensile sample, precisely at the centre of the neck.

It is showed in many cases (HDPE, LDPE, PP, PA6, PCL, PLA, PET, PETG, filled polymers, blends, etc.) that the overall dilatation measured with the VidéoTraction system very important. Also, in specific materials (HDPE), it was proved that the dilatation is in line with the proportion of voids measured by electron microscopy from interrupted tests.

Not only this approach gives access to the cavitation kinetics (that is very active in many cases), but also the volume strain data are used to derive the intrinsic behaviour of the polymer, i.e. the behaviour exhibited by the solid ligaments between voids. This information constitutes the basis of reliable simulations run with finite-element codes to predict the response of real polymers parts subjected to complex strain paths. Over all, it opens the way to a fundamentally new vision of plastic deformation in polymers.

SL13

ASPECTS OF TIME- AND TEMPERATURE-DEPENDENT IMPACT FRACTURE FOR POLYMER MATERIALS

R. LACH, W. GRELLMANN

Fracture in polymers as a typical non-linear viscoelastic process implies several aspects of time- and temperature dependence, such as correlations between fracture mechanics parameters and molecular relaxation processes for unstable fracture, as well as the intrinsic time dependence of stable fracture itself.

For a high number of polymers clear evidences of correlations between local maxima found in the temperature dependence of the impact fracture toughness and the mechanical loss factor (tan δ from DMA) have been observed. Non-linear–viscoelastic fracture processes are characterized by the same Arrhenius-type activation energies as deformation in the linear response range despite different deformation amplitudes. Furthermore, a simple relationship between the strength of relaxation processes (the magnitude of maxima in tan δ) and the magnitude of the local toughness maxima has been found.

In the literature, some information is available for the kinetics of stable crack propagation at creep and high-speed loading but not for that at moderate impact loading. The outcome of an extensive analyses of the crack-tip opening displacement (CTOD) rate and the crack speed as a function of stable crack growth, that has been made for a high number of polymer materials having different molecular architectures and compositions, is an adequate description of the fracture process: (i) The CTOD rate is a measure of the rate sensibility of stable fracture process only depending on “matrix” deformation delivers insight into micro-mechanics and activation mechanisms of the fracture process. (ii) The stable crack propagation can be understood as a 3-phase process including crack-tip blunting/ crack initiation, non-stationary stable crack growth and steady-state stable crack growth (an equilibrium state). The last is characterized by constant CTOD rate and crack speed. (iii) Steady-state stable crack propagation can be described as a kinetic phenomenon.

SL14

THE APPLICATION OF MICROFOCUS SYNCHROTRON RADIATION X‑RAY SCATTERING TO STUDY FRACTURE MECHANISMS IN POLYOLEFINS

N.E. ZAFEIROPOULOS^a, R.J. DAVIES^b, K. SCHNEIDER^a, S. TRABELSI^a, J. RIEGER^c, C. RIEKEL^b, M. STAMM^a

The fracture properties of polymers are one of the key parameters that define their service life and limit their applications. One of the most interesting and important questions is how the molecular architecture and the structure of polymers at nano- length scales influence their fracture properties. X-ray scattering is a powerful means of probing bulk structures at the nanometer scale. It can therefore provide a wealth of information relating to such structure-property relationships. However, traditional x-ray sources are able to produce x-ray beams with large beamspot sizes, thus, leading to an averaging over a large area of the samples under study. Synchrotron sources are able to overcome this drawback, since they offer a much higher photon flux, thus, allowing beamspot sizes in the order of few μm, and subsequently high spatial resolution. In the present study, synchrotron radiation microfocus small and wide angle X-ray scattering is used to investigate the fracture mechanisms ahead of a crack tip in situ with the application of load, and the damage area ahead and around the crack tip post mortem, in isotactic polypropylene and high density polyethylene samples of different thermal histories. The results revealed that significant cavitation develops in the damage area at the plastically deformed region beyond the crack tip, and inside the damage zone rod and platelet-shaped cracks/voids are formed (as revealed by SAXS), accompanied by martensitic crystal transformations (as revealed by WAXS).

SL15

DETERMINATION OF LIMITING PHYSICAL AND MECHANICAL PROPERTIES OF SEMICRYSTALLINE POLYMERS

J. KRATOCHVÍLA^a, D. VAREČKOVÁ^b, J. KUČERA^a

The relationship between solid-phase content and structure and properties of different polypropylene grades was studied. The absolute value of solid-phase content and its time dependence was determined by the pulsed ¹H-NMR method at temperature 23°C. The solid-phase content values were correlated with absolute values of degree of crystallinity, evaluated by standard methods: density, DSC, and X-ray diffraction. Measurement temperature of 23°C was applied, because this temperature is generally used as standard for conditioning and measurement of standard physical and mechanical properties.

The absolute value of solid-phase content was compared with a long-term time-dependent measurement of crystallinity on different morphological forms of polypropylene (pellets, powder, injection-moulded specimens, and hot pressed films). Polypropylene samples with different molecular weight and stereoregularity were prepared, including totally atactic and highly isotactic materials. The atactic PP of low molecular weight was used as a totally liquid polymer phase. The measurement was performed on a broad variety of materials; such as on commercial PP products and polymers synthesised in laboratory reactors. Evaluation of tensile and flexural properties of selected materials confirmed a linear correlation between the modulus of elasticity and the solid-phase content with the ageing time. The values of physical and mechanical properties extrapolated to 100 % solid-phase content were defined as the limiting physical and mechanical properties. These limiting physical and mechanical properties were specified as material parameters of semi-crystalline polymers. The results were interpreted in terms of secondary crystallization of polypropylene.

SL16

COMPATIBILIZATION OF POLYMER BLENDS: ADVANCES, PROBLEMS AND CHALLENGES

I. FORTELNÝ

Most polymer pairs are incompatible, i.e. their blends show rough phase structure and bad mechanical properties. They can be successfully compatibilized with premade or reactivelly formed block or graft copolymers having blocks identical, miscible or compatible with compatibilized polymer chains. More difficult is compatibilization of multicomponent polymer blends. This problem is topical not only of development of new materials but also of material recycling of mixed, e.g. municipal, plastic waste.

It is frequently assumed that the compatibilization efficiency of copolymers is given by their molecular structure and molecular structure of basic components of a blend. Recent experimental results have shown that, besides of molecular structure, the compatibilization efficiency depends also on the volume ratio of the blend basic components and mixing and processing conditions. It seems that the localization and supermolecular structure of a compatibilizer in polymer blends cannot be predicted, at least for systems where copolymer blocks are shorter than chains of basic blend components, from considerations of equilibrium thermodynamics.

On the other hand, it was found that correlation between localization of different copolymers in a blend can lead to the situation that a mixture of these copolymers is better compatibilizer than any of the copolymers (e.g. a mixture of styrene-butadiene block copolymers (SB) with ethylenepropylene elastomers (EPR) in some polyolefin/polystyrene (PO/PS) blends). Cooperative effect of SB/EPR compatibilizer and substituted diamines on improvement of morphology and mechanical properties of PO/PS blends was detected. Application of this compatibilization procedure enhances toughness of the recyclates of municipal plastic waste to a level of virgin polyolefins.

Formulation of rules for prediction of the localization of a copolymer in blends at steady mixing is a challenge for future.

SL17

IN SITU COMPATIBILIZATION OF PS/EPDM BLENDS VIA ULTRASONIC EXTRUSION

R. SLEZÁK^a, B. HAUSNEROVÁ^a, J. LI^b, S. GUO^b

Majority of polymers are immiscible due to unfavourable thermodynamical conditions. This paper presents a novel and progressive compatibilization method, where ultrasonic oscillations are applied onto PS/EPDM blends during extrusion in order to improve their interfacial adhesion. Emphasis was given on the effect of the ultrasonic radiation on mechanical properties, phase morphology and rheological response of the blend. As mechanical tests revealed, impact-strength of the PS/EPDM rises at first with increasing ultrasonic intensity indicating improved interactions between both phases. However, slight decrease of blend's toughness was observed at very high ultrasonic intensity, indicating prevail of degradation process over compatibilization effect. Presence of above mentioned competitive processes occuring during introduction of ultrasound into the mixture of PS and EPDM melts was further confirmed by dynamical rheological measurements. Complex viscosity of the irradiated blend was found to be higher in comparison with the untreated extrudate, but it decreased again with longer time of irradiation and increasing intensity. Concerning phase morphology, SEM analysis showed that ultrasonic oscillations cause size reduction of tough EPDM particles distributed in the brittle PS matrix. Precise control of ultrasound's parameters as intensity or time of treatment leads to efficient enhancement of interfacial adhesion of the PS/EPDM blends.

SL18

SCIENTIFIC ASPECTS OF MECHANICAL RECYCLING OF POLYMERIC WASTES

V. VERNEY, S. COMMEREUC

In the cycle of life of a polymeric material, the first stage is the synthesis of the macromolecule which controls for a great part its final properties. Once processed, the polymeric material becomes a manufactured article with a specific function. This article will have a use life during which the necessary property will have to be preserved within preset limits to ensure the reliability of the structure. During its use and according to the stresses applied, the material will degrade and its performance will deteriorate. At the end of life, the object becomes a waste and its matter can return in a new cycle of life on condition it conserves a certain level of properties. From there, a new cycle can start again.

Building is by volume the second market sector of plastics following the packaging sector. Each year the demolition sites generate approximately fifty million tons of waste. A very significant share relates to non hazardous wastes and the plastic amount contained in it is closed to the million tons. In 1992, PVC accounted for 55% of plastics in building materials and the tendency is still envisaged to increase. Currently in France, one window out of two is made of PVC and in 1997 3.180.000 windows were installed. These facts precise the extent of the problem. It is thus necessary to find ways of valorization for plastic wastes of this sector and in particular for PVC scraps whose recycling is problematic taking into consideration environmental considerations.

We will present the interest of a scientific approach in the case of the mechanical recycling of plastic waste. This scientific approach is based on two concepts:

• quantification of the initial state of degradation of the material
• impact of the processing operations specific to recycling

The methodology employed is based on the study of the molecular evolution which consists in coupling chemical and physical evolutions at various scales of analysis. Thus, chemical titrations of reactive species or specific groups are carrried out mainly through spectroscopic investigation. In parallel, physical evolution is monitored with the help of dynamic spectrometric techniques such as melt viscoelasticity, modulated differential scanning calorimetry, electron paramagnetic resonance. Our objective is to mimimize the cumulative impact of each recycling operations (grinding, washing, processing,...) to obtain a new material with a high level of properties. This approach will be exemplified with PP (car bumpers, battery ), PVC (windows profiles), or PET/PC (soft-drink bottles) mechanical recycling with theaim to reprocess a new material qualified for a building application.

Acknowledgements : This research has been supported by Ademe (Agence De l'Environnement et de la Maitrise de l'Energie) and CSTB (Centre Scientifique et Technique du Batiment).

SL19

MULTISCALE RHEOLOGICAL MODELLING

M. GRMELA

Responses of complex fluids to external forces (e.g. imposed flows) are now routinely measured on several levels (e.g. stresses observed in classical rheological measurements and microstructure observed in optical, slow neutron and NMR observations). Multiscale (multilevel) models are needed to organize and interpret results of such measurements. Is there a universal framework for such models (i.e. a framework playing the same or similar role as, for example, the framework of local conservation laws plays in classical hydrodynamics)? Such framework, based on the requirement that solutions of the governing equations agree with experimentally observed approach to the thermodynamic description, has been identified. The time evolution of classical hydrodynamic fields and other fields chosen to describe the microstructure is seen in the framework as a continuous sequence of Legendre transformations. The framework provides a pivotal point about which construction of the governing equations, expressing our microscopic insight into the complex fluids under consideration, can be organized. The framework has been originally identified as a common structure of well established (i.e. successfully tested with experimental observations) macroscopic, mesoscopic and microscopic theories (like e.g. Boltzmann kinetic theory and classical hydrodynamics). In this talk we illustrate the framework in the context of rheological modelling of suspensions and in molecular simultations.

SL20

NANOCOMPOSITES OF POLY(ε-CAPROLACTANE) WITH LAYERED SILICATES: EFFECT OF THE STRUCTURE ON DEGRADATION

D. KUBIES, J. KOTEK, J. BALDRIAN, J. KOVÁŘOVÁ, M. ŠLOUF, F. RYPÁČEK

In the present work, we studied feasibility to prepare PCL nanocomposites with the intercalated and exfoliated structure using silicate masterbatches. The effect of the silicate on mechanical properties and degradation was evaluated.

Firstly, PCL/Cloisite 30B masterbatches with the intercalated or exfoliated structure were prepared by polymerization of e-caprolactone in presence of the montmorillonite Cloisite 30B. Secondly, PCL nanocomposites were prepared by melt blending of homopolymer PCL with Closite 30B or PCL masterbatches. The morphology of PCL nanocomposites (intercalated or exfoliated) corresponded with strucutre of the used masterbatch.

The increase in Young modulus with the increasing silicate content was predominantly caused by the inorganic phase and also supported by the contribution of the low-molecular weight (LMW) PCL fraction coming from the masterbatch to the total degree of crystallinity. On the contrary, the increase in yield stress was affected mainly by the LMW PCL. All nanocomposites exhibited typically ductile behavior with strain at break exceeding 500 %.

The samples were degraded in the phosphate buffer at 37 °C. It has been observed that up to 6 months of degradation, the Young modulus and yield stress increased with the increasing degradation time. For longer degradation time, both characteristics tended to decrease. These trends were more pronounced for PCL/masterbatch systems with the highest silicate content. At the same time, the strain-at-break values of these nanocomposites were markedly reduced to 10 % after 6 month exposition. This significant drop in ductility was not observed for the other samples. Observed evolution of mechanical behavior reflected the nanocomposite structure and changes in the nanocomposite composition during degradation.

Acknowledgement

The financial support of our work by grant No. KJB4050309 from the Grant Agency of Academy of Science of the Czech Republic is gratefully acknowledged.

SL 21

NOVEL APPROACH FOR THE INTERPRETATION OF X-RAY SCATTERING DATA FROM LAYERED SYSTEMS

M.Y. GELFER^A, C. BURGER^A, P. NAWANI^A, B.S. HSIAO^A, B. CHU^A, M. SI^B, M. RAFAILOVICH^B

X-ray scattering is one of the most popular techniques for the investigation of nanocomposites formed by organically modified layered silicates and thermoplastic polymers. Suggestions about compatibility between polymer matrix and organoclays fillers are often made based on the effect that mixing with a polymer has on the magnitude of the interlayer spacing (d-spacing) in organoclays. Usually, an increase in average d-spacing resulting from mixing with polymer is attributed to the good compatibility between polymer and nanofiller, leading to the intercalation of layered systems by polymer molecules. An exfoliation of layered structures should result in a suppression of the interference peak leading to a form factor shaped appearance of the scattering curve with its maximum at zero scattering angle.

It is common among researchers to determine the average d-spacing from the reciprocal position of first intense scattering_. maximum. However, our experimental data and results of calculations and simulations show that the complex character of periodicity and quasi-periodicity (interstratification) often encountered in organoclays and composites can result in significant errors when d-spacings are determined by a naïve straightforward application of Bragg's law. For instance, polymodal layer thickness distributions encountered in cloisite^® organoclays can result in significant shifts of scattering maxima from those suggested by Bragg's law and non-equidistant spacings of higher orders. Strong correlation between thicknesses of neighbouring layers observed in Somasif^® systems causes appearance of additional scattering maxima located around s₀=0.5/d. Thermal degradation of surfactant layers may result in a weakening or even disappearance of SAXS traces in absence of exfoliation of layered structures. Stacking disorder ranging from moderate stacking faults to complete turbostraticity present in many clay minerals causes an asymmetric and possibly modulated shape of the intra-layer (hk) reflections

We suggest a simple yet effective analytic (i.e. closed form) approach for the interpretation of SAXS and WAXD patterns from layered materials with stacking faults. The proposed approach is based on a generalization of Hermans' 1D paracrystalline model. It allows to calculate approximate scattering curves for layered systems using a small number of physically meaningful parameters like average layer thicknesses, parameters of layer thickness distributions, type of crystalline lattice in silicate layers, relative displacements of layers from an ideally periodic positions.

SL 22

POLYMERIC MATERIALS MODIFIED WITH SILICA NANOPARTICLES: PREPARATION AND APPLICATIONS

Y.L. LIU

Silica nanoparticles have showed great usage in formation of nanocomposites with various polymeric materials. To improve the interfacial compatibility, the used silica nanoparticles needs some modifications of incorporating organic moieties onto the surface silica particles. In this work, a novel method of modification on silica particles is presented. This modification approach provides a convenient way to introduce various functional groups onto the surface of silica nanoparticles. The functionlizaed silica particles are used as additives, reactive co-monomers, and cross-linking agents to from various polymer-silica nanocomposites with different polymers in different ways. The utilized polymers include epoxy, methylmethacrylate (MMA), chitosan, polydimethylsiloxane (PDMS), and polymer electrolyte. Adding silica in such polymers and formation of nanocomposites significantly improved some properties of the polymers for their specified applications. For examples, PMMA-silica nanocomposites form extra-planar thin film for hard coatings, PDMS-silica nanocomposites show altered degradation patterns and thermal stability, chitosan-silica nanocomposites provide extra free volume to result in high flux in pervaporation dehydration of water-alcohol solution, and polyelectrolyte-silica nanocomposite exhibit low methanol crossover and improved mechanical property to enhance its performance of using as a proton exchange membrane in direct methanol fuel cells. This presentation would discuss these materials and applications in detail basing on the attractive results and performances.

SL 23

Adhesive strength on polymer surfaces

A. Kopczynska, G.W. Ehrenstein,

The phenomenon of surface plays an important role in a lot of technical processes like e.g. multi-component injection moulding, varnishing and adherence. Wetting and adhesive strength are also connected to the phenomenon of surface tension. The knowledge of surface tension of components enables the evaluation of e.g. their adhesion.

For the measurement of the surface tension of liquids, there are a lot of methods like e.g. ring, Wilhelmy plate, pendant and sessile drop. From the measurements with these methods, surface tension can be directly determined. In contrary, the surface tension of solid polymers can only be measured indirectly by means of the contact angle (advancing and receding contact angles, Fig. 1) between the drop of a test liquid and the surface of the material. To calculate the surface tension from the measurement of these angles, different equations are used, e.g. Neumann, Wu, as well as Owens and Wendt. Due to the technical (non-ideal) surfaces of polymers, thee is a big difference between the advancing and receding contact angles - the contact angle hysteresis.

Different methods are presented that can be used to determine the surface tension of polymers in solid and liquid states.

Results of the overall surface tension as well as of its polar and disperse fractions are presented (epoxy and polyester resin), referring to the solid as well as the liquid state of the material. The effect of temperature on the surface tension of polymers is investigated. From the measurements, one can find out the exact surface tension of the polymers in the solid state. Furthermore, the influence of the surface tension of the polymers and the adhesive on the adhesive strength is studied.

Fig. 1: Contact angle water/polystyrene (left: advancing angle, right: receding angle)

SL 24

TOUGHENING OF CARBON FIBER/EPOXY COMPOSITE BY THE EPOXY-POLYSULFONE SEMI-INTERPENETRATING POLYMER NETWORKS WITH MORPHOLOGY SPECTRUM

N.G. YUN^a, Y.G. WON^a, S.C. KIM^b*

Fracture toughness of epoxy composite with polysulfone(PSf) to form morphology spectrum was investigated. The epoxy resin was based on diglycidyl ether of bisphenol-A(DGEBA type) and diaminodiphenylsulfone(DDS). 1K carbon fabric was used as the reinforcing material. The morphology spectrum which has gradual change of the morphological feature resulting from the concentration gradient of PSf in the composite can be obtained by inserting the PSf film and by spraying particles in carbon fiber reinforced epoxy prepreg before cure. The relative rate of the dissolution and diffusion of the PSf in the epoxy determine the concentration gradient of the PSf. As the concentration of the PSf increases, the morphology changes from sea-island to nodular structure. The fracture toughness of the composite with 20 wt % PSf film was 2.7 times higher than that of the unmodified composite and with 21 wt % large size particles was 2.2 times higher than that of the unmodified composite. This result was ascribed to the plastic deformation of the continuous PSf rich phase in the semi-IPN having morphology spectrum.

SL 25

RADIATION MODIFICATIONS IN POLYMERS

T. ZAHARESCU

Ionizing radiation exposure represents a suitable alternative for polymer processing, the procedure of the work is the academic research for structural change promotion, or an accelerated testing method for material characterisation. The scientific results of radiation chemistry of polymers are immediately transferred onto the large scale in economical activities. The background of industrial applications is the cleavage of weaker bonds followed by the recombination of free radicals or by the grafting of molecular fragments on stable macromolecule chains. The performances of final products depend on the absorbed doses the dose rate, the material formulation and the service conditions under which they operate. The polymers that are crosslinked by irradiation with high energy particles (especially, accelerated electrons or gamma rays) present improved characteristics, such as mechanical properties, electrical and thermal properties, chemical strength against degradation and dissolution, because three dimensional network is grown up during irradiation. The durability of radiation processed polymers determined by various procedures (IR spectroscopy, chemiluminescence, oxygen uptake and so on) is sensibly higher than the initial material. In addition, the irradiation of polymer blends produces new materials, which behave different than the original components. The radiochemically degraded polymers generates materials for a large range of applications due to the mitigation of molecular weight even up to monomers (for example, cellulose). The large areas of usage for radiation degraded polymers is related to their compatibility with other materials.

References

• R. L. Clough, "High energy radiation and polymers. A review of commercial processes and emerging applications", Nucl. Instrum. Meth., B 185 (2001) 8.
• L. Sanche, "Irradiation of organic and polymer films with low energy electrons", Nucl. Instrum. Meth., B 208 (2001) 4.
• G. Burillo, R. Clough, T. Czvikovsky, O. Güven, A. Le Möel, W. Liu, A. Singh, J. Yang, T. Zaharescu, "Polymer Recycling, Potential Application of Radiation Technology, Radiat. Phys. Chem,, 64 (2002) 41.

SL 26

POLYOXYMETHYLENE WITH REDUCED FORMALDEHYDE EMISSION

L. TOKARZ^a, J. CIEŚLAK^a, J. STASIŃSKI^a

Polyoxymethylene (POM) is a constructional polymer having very good mechanical and chemical properties that give it wide practical applications.

The most important advantages of polyacetals are hardness, toughness, good dimensional stability, good thermal stability (- 40^°C ÷ + 110^°C), and resistance to many organic solvents.

Because of these advantages POM has many applications. It is used for precision technical products such as: gears, fancy goods, holders and parts of electric machines, produced by injection moulding as well as for profiles production by extrusion. These advantages make POM desirable material for the automotive industry as well as electronic and electrotechnical industry.

Besides these various applications the range of POM's utility seems widen. One of the most important directions is to obtain POM with reduced formaldehyde emission for toys production. In this situation, we - in Polyacetal Group of ICRI - checked some substances in the reactive extrusion process in ZE-25-33D Berstorff extruder so the results showed in this paper concerned chemical modification by the application of odor-reducingadditives. The additives were added to standard polymer TARNOFORM® (MFR = 9 g/10 min). The substances added are: succinimide, magnesium hydroxide and some others incorporated individually. The following properties of POM products obtained in the presence of new additives were determined: melt flow rate, the content of the unstable fraction, thermal stability and the measure of formaldehyde surface emission.

The results we obtained are good and are in agreement with ours expectations.

SL 27

A PERSPECTIVE BIODEGRADABLE POLYMER SYSTEM: POLY(p-DIOXANONE)-BASED BIODEGRADABLE POLYMERS

Y.Z. WANG

Poly(p-dioxanone), PPDO, is a well-known aliphatic polyester having good physical properties and bio-compatibility, and has been used to make monofilament sutures with good tenacity and knotting[1]. However, PPDO has not attracted the interests of researchers who are engaged in the research of ecomaterials due to its high cost and un-affirmed environmental degradability until recent years. Our research group has invented a novel technique to synthesize the monomer, p-dioxanone, of PPDO with a very low cost, and therefore made the cost of PPDO decrease remarkably. On the other hand, Nishida et al. [2,3] has found many kinds of microorganisms in natural environments, which can degrade PPDO. Therefore, PPDO-based biodegradable polymers will find their uses not only in biomedical materials but also in environmentally friendly materials. In this presentation, a short review on the recent progress in PPDO-based biodegradable polymers will be presented, and an emphasis will be put on the results obtained in our research group, which mainly include the following aspects: 1) the synthesis of PPDO with higher molecular weights via various methods such as using chain-extenders, new catalyst and initiator systems; 2) PPDO copolymers and blends with other biodegradable polymers such as poly(ε-caprolactone), polylactide, poly(ethylene succinate), poly(butylene succinate), poly(vinyl alcohol), poly(ethylene glycol) and starch; 3) PPDO/MMT nanocomposites. The research results show that the above biodegradable PPDO-based polymer system behaves good performance and will be perspective in its applications in both ecomaterials and biomedical materials.

Acknowledgment: This work was supported financially by the Key Project of International Cooperation (Contract No. 2004DFA04700), and the High Tech R&D Program of China (Contract No. 2002AA322030).

Reference

1. Yang, K. K.; Wang, X. L.; Wang, Y. Z. J. Macromol. Sci. Polym. Rev. 2002, C42(3), 373-398.

2. Nishida, H.; Konno, M.; Ikeda, A.; Tokiwa, Y. Polym. Degrad. Stab. 2000, 68, 205-217.

3. Nishida, H.; Konno, M.; Tokiwa, Y. Polym. Degrad. Stab. 2000, 68, 271-280.

SL 28

FUNCTIONAL POLYMERS TO REMOVE METAL IONS

B. L. RIVAS

Polymers containing metals have emerged as a new generation of material with tremendous potential in fields like superconducting materials, ultra-high strength materials, liquid crystals, catalysts, and biocompatible polymers. The structures of some polymer-metal ion complexes have been reported in the literature.

Insoluble polymeric supports are widely investigated and applied for metal recovery from dilute solutions. There are different natural and synthetic products that show ion-exchange properties. The organic resins are by far the most important ion exchangers. The main advantages are high chemical and mechanical stability, high ion-exchange capacity and ion-exchange rate. Another advantage is the possibility of selecting the fixed ligand groups and the degree of cross-linking.

The separation methods based on membrane process are among the most promising techniques for enrichment of various species from solutions [1-3]. Thus, a number of soluble and hydrophilic polymers have been prepared through addition polymerization and by functionalizing various polymers, and found to be suitable for the separation and enrichment of metal ions in conjunction with membrane filtration. Membrane filtration allows easily the separation of metal ions bound to soluble polymers from non-bound metals. This method is known as the liquid-phase polymer-based retention (LPR) technique. Applications of water-soluble polymers to the homogeneous enrichment or selective separation of various metal ions from dilute solutions have been reported.

Water-soluble polymer materials are commercially available or can be synthesized by different routes.

The polymers, prior to being used in the LPR technique, are fractionated by the same method using different membranes of known molecular weight exclusion limit. Thus purified, they are then lyophilized and characterized. For LPR experiments, the highest molecular weight fractions are normally used in combination with a low molecular weight exclusion limit membranes to ensure no macromolecule exits the ultrafiltration cell. Metal ions with high interaction rates with the polymer are retained by the polymer, which is not able to pass through the ultrafiltration membrane, while other ions are eluted through the membrane.

Acknowledgements. The author thanks to FONDECYT (Grant No 1030669) the financial support.

[1] Spivakov BYa, Geckeler K, Bayer E. Nature, 315, 313 (1985).

[2] Rivas BL., Geckeler KE, Adv. Polym. Sci. 102, 171, (1992).

[3] Rivas BL, Pereira ED, Moreno-Villoslada I, Progr. Polym. Sci., 28,173 (2003).

SL 29

NOVEL TWEEZERS FOR THROMBUS SAMPLES IN BLOOD VESSELS USING PIEZOELECTRIC POLYLACTIC ACID FIBERS

Y. TAJITSU

As polymers which exhibit high-tensile piezoelectricity, ferroelectric polymers such as polyvinylidene fluoride (PVDF) are well-known. Poly-l-lactic acid (PLLA) has recently attracted attention as a polymer which exhibits a high shear piezoelectric constant. In this study, we fabricated PLLA fiber samples by high-speed spinning. We focused on a PLLA fiber and report on the measurement of its piezoelectric characteristics. Finally, on the basis of our results, we demonstrated that PLLA fibres can grasp and extract objects like tweezers. The following results were obtained. The purpose of this study is to control the piezoelectric motion of the PLLA fiber similar to a piezoelectric actuator. To this end, an effective method of applying an electric field in a direction perpendicular to the PLLA fiber axis must be devised. By controlling the temperature of the surface of the PLLA fiber, we succeeded in forming four symmetrical electrodes with having a 100 m2 area by vacuum deposition. We clamped one end of the electroded PLLA fiber to the cell. Then, we applied AC voltage to the PLLA fiber. Lastly, we observed the vibration motion of the free end of the PLLA fiber which was opposite to the clamped end of the PLLA fiber. The vibration amplitude of the free end of the PLLA fiber was about 100 mm under the applied AC voltage of 130 V with a frequency of 18 Hz. We speculated that the shear strain locally generated by the electric field finally caused the bending of the whole PLLA fiber. For the elementary demonstration, we set up a pair of PLLA fibers, with diameters of 100 mm each, like tweezers. A silica bead with a diameter of 120 mm was placed in a vessel. We attempted to grasp the bead by applying AC voltage to the pair of PLLA fibers. In the second stage, we attempted to remove the bead from the vessel after grasping it firmly. In the next demonstration, on the basis of the above experimental results, we adopt a more realistic model, as follows. Here, we assumed that a thrombosis in blood vessels occurred and attempted to remove the thrombosis from the affected area. In order to perform this very delicate operation under a microscope using the PLLA fiber tweezers, we developed a new experimental system. We set up a pair of PLLA fibers, each with a diameter of 40 mm, in the form of tweezers. A thrombosis sample with a diameter of 300 mm was placed in a vessel. Using this system, we tried to excise the affected area. We attempted to grasp the thrombosis sample by applying ac voltage to the pair of PLLA fibers. We recorded a video movie of the test demonstration using a CCD video camera. All stages proceeded well in this study. On the basis of these experimental results, we consider that there is a high possibility of using the PLLA fibers for various applications.

SL 30

RECENT AND CURRENT TRENDS IN COMMODITY/SPECIALTY POLYMERS RELATIONSHIP

V. DUCHÁČEK

In the second half of the outgoing century, polymeric materials have been a major facilitator of technical progress, which has been the basis for many elements of our standard of living today. Polymer consumption looks back at an impressive growth. The increase over the years has been fairly steady, with only minor dips during the two oil crises, and will continue into the 21^st century because of the growing world population and global striving for a higher standard of living. Looking at the polymer development in the 21^st century, we can see the continuation of good product availability and changes in terms of globalisation and restructuring.

A forecast is always risky and often likely to be wrong, as the two independent forecasts of plastics manufacture development for the mid-1990s made in mid-1970 demonstrates. Why did the prognoses miss the real development significantly? The development parallels the theory of evolution. Engineering and process development gave commodity plastics a significant cost advantage, allowing them to defend their position. Product development led to an evolutionary property optimisation to meet the over-increasing requirements of the market. Commodity plastics grew over-proportionally and left little room for the expensive speciality plastics.

In spite of steady continued growth, the polymers business is highly cyclic. This cyclical tendency is, to a large extent, self- inflicted by polymers manufacturers: concern about potential loss in the market share forces suppliers to invest in ever-larger capacities.

The interaction of process, product, and market developments indicates that established (commodity) polymers will continue to grow well. Against the line of them, it is going to be difficult for new (speciality) polymers to establish themselves in a group of well-positioned polymers.

The support of the Ministry of Education, Youth, and Sports of the Czech Republic (through the research grant MSM 6046137302) is gratefully acknowledged.