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COMPARISON OF THE EFFICIENCY OF PHOSPHORIC STABILIZERS IN METALLOCENE POLYETHYLENE
E. MALOSCHIK1,2, E. FÖLDES1, Á. JANECSKA3, G. NAGY3, B. PUKÁNSZKY1,2
1 Chemical Research Center, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 17, Hungary
2 Department of Plastics and Rubber Industries, Budapest University of Technology and Economics, 1521 Budapest, P.O. Box 92, Hungary
3 Tisza Chemical Work (TVK), H-3581 Tiszaújváros, P.O. Box 20, Hungary
The synthesis of polyolefins by metallocene catalysts is one of the most recent developments in the plastics industry. Although these new products are more and more widely applied, there are several problems unsolved. One of them is the efficient stabilization of the polymer. In the present work the effectiveness and stabilization mechanism of two additive systems containing the same primary antioxidant with phosphite and phosphonite secondary antioxidants, respectively, were compared in metallocene polyethylene (mPE). Changes in the chemical, physical and rheological properties of the polymer caused by multiple extrusions were determined and related to the chemical transformation of the phosphoric stabilizers.
The number of unsaturated groups representing the weakest points of the polymer was by one order of magnitude lower in the mPE studied than in conventional Phillips type polyethylenes. As a consequence, the stabilizers were more efficient in mPE under the processing conditions.
Quantitative relationship was established between the degree of oxidation of the phosphoric stabilizer and changes in the properties of mPE. During processing, breaking and enlargement of the polymer chains occur simultaneously. The type of the phosphoric stabilizer affects the overall direction of the reactions. The phosphonite antioxidant hinders the recombination of macroradicals more efficiently than the phosphite molecules.
EFFECT OF COMPONENT INTERACTION ON THE PERFORMANCE OF INDUSTRIAL ADDITIVE PACKAGES USED FOR THE STABILIZATION OF PIPES
E. EPACHER1,2, Á. ORBÁN-MESTER3, G. NAGY3, P. STANIEK4, B. PUKÁNSZKY1,2
1Department of Plastics and Rubber Technology,
Budapest University of Technology and
Economics, H-1521 Budapest, P.O.Box 91, Hungary
2Institute of Chemistry, Hungarian Academy of Sciences, H-1525 Budapest, P.O.Box 17, Hungary
3Tiszai Vegyi Kombinát (TVK), H-3581 Tiszaújváros, P.O. Box 20, Hungary
4Clariant Huningue, SU TIM Research Huningue, F-68331 Huningue Cedex, BP 149, France
The service life of polyolefin pipes and the factors influencing it have been the subject of considerable interest for a long time. Such pipes are used in diverse application areas such as water, waste water and sewage pipes, floor, wall and ceiling heating systems, warm and hot water solar systems as well as for natural gas supply [1]. Their guaranteed service life often reaches 50 years. In order to guarantee this long service life, pipes have to be stabilized with appropriate additive packages. Pipes maybe applied at temperatures as high as 105 °C [2]. Under these conditions numerous physical and chemical processes take place, which all influence the lifetime of a pipe. Additives may evaporate, may be leached by the surrounding media or lost by undesired chemical reactions. The detailed study of Gedde and coworkers [3-6] showed that the relative importance of these processes depends on the polymer and also on the conditions of testing or on the type of application. These results clearly indicate that the hydrolytic and chemical stability, solubility and diffusion of the additives are crucial factors in the determination of the lifetime of polyolefin pipes.
The goal of this project was the study of the hydrolytic stability and performance of industrial additive packages for the stabilization of pipes or other products used in contact with water. 25 additive combinations were processed to the corresponding granules and pipes were extruded from them. These packages were composed of hindered phenolic antioxidants and sulfur containing processing stabilizers or a sterically hindered amine (HALS) compound. In the first step of the project both the granules and the pipes were subjected to numerous standard tests and the structure of the polymer was also characterized by its functional group content. The comparison of measured properties proved that the performance of the additives differed drastically, depending on the additive combination used. In some cases the effect of the second component dominated, while in others additive interactions played a more important role. This paper attempts to find a correlation between the chemical composition of the additives and their effect, as well as to identify efficient additive combinations for practical use.
References
THE EFFECT OF PROCESSING CONDITIONS ON MECHANICAL BEHAVIOR AND MORPHOLOGY OF COMPATIBILIZED PP/PS BLENDS
Z. STARÝ, Z. KRULIŠ, M. ŠLOUF, J. HROMÁDKOVÁ
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq.2, 162 06 Prague, Czech Republic
Commingled plastic waste consists mainly of different polyolefins and polystyrenes. Most of these polymers are unfortunately incompatible. The incompatibility between polymeric components is responsible for the poor mechanical properties of the end product. An incorporation of proper compatibilizer reduces interfacial tension, refines blends morphology and therefore leads to an improvement of mechanical properties of the final material. The efficiency of compatibilization is determined by molecular properties of chosen compatibilizer and also by mixing conditions.
An efficient compatibilization system based on the combination of styrene-butadiene block copolymer (SBS) with ethylene-propylene random copolymer (EPM) has been developed for polyolefin/polystyrene blends. Polypropylene/polystyrene blends were prepared under various mixing conditions i.e. temperature, time of mixing and mixing speed. Tensile impact strength was used as the main criterion of compatibilization efficiency. The basic morphological investigation of the selected blends was carried out.
Obtained results show that blends with PP matrix are less sensitive about alteration of speed and time of mixing than blends with PS matrix. Temperature changes lead to the considerable changes of morphology and therefore mechanical properties. The highest toughness was gained by the lowest temperature (170°C).
PHOTO-INITIATED INTREACTION OF BROMINATED FLAME RETARDANTS WITH HALS - A MODEL STUDY
K. ANTOŠ1, J. SEDLÁŘ2
1Masaryk University, Brno, Kotlářská 2, Brno, Czech Republic
2Polymer Institute Brno, Tkalcovska 36/2, 656 49 Brno, Czech Republic
Several brominated flame retardants (1,2,3,4,5-pentabromo-6-(pentabromophenoxy)benzene (Decabromodiphenyl ether) (I), 1,2,5,6,9,10-hexabromocyclododecane (II), tris-tribromoneopentyl phosphate (III)) dissolved in aromatic solvent and cyclohexane, resp. have been examined as to their susceptibility to form HBr upon irradiation by UV light emitted from a Xe burner. In the case of I it has been shown that the molecule undergoes photoreduction connected with a successive loss of HBr. The rate of HBr evolution decreases in series I > II >> III. The presence of an electron donor, such as HALS, considerably enhances the rate of photodebromination processes. This observation thus enables to speculate about the involvement a charge-transfer exciplex in the reaction pathway. The influence of solvent character upon the reaction mechanism is also discussed.
PHOTOOXIDATION OF BENZIL GROUPS IN THE PRESENCE OF HAS IN POLYMER MATRICES
CS. KÓSA,a J. MOSNÁČEK, a Š. CHMELA,a I. LUKÁČ,a W.D. HABICHERb, P. HRDLOVIČa
aPolymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 842 36 Bratislava, Slovak Republic, upolkosa savba.sk
bInstitute of Organic Chemistry, Dresden University of Technology, Mommsenstrasse 13, 01062 Dresden, Germany
Benzil (BZ) is an industrially important member of the class of molecules with 1,2-dicarbonyl functionality. It has been utilized in the preparation of photographic materials and polymer resists, and as a photoinitiator in radical polymerizations.1-3
Recently, we reported that BZ free and polymer bounded could be converted almost quantitatively to benzoyl peroxide (BP) upon irradiation (>400 nm; i.e., the long wavelength edge of the n® p * absorption band) in aerated glassy polymer matrices (eq. 1). 2,3,4
This photoperoxidation was chosen as a model reaction for study the mechanism of photostabilisation by HAS. Photoperoxidation of benzil in PS matrix was observed in the presence of 4-hydroxy-2,2,6,6-tetramethyl piperidine (TMP). In the presence of N-oxy 4-hydroxy-2,2,6,6-tetramethyl piperidine (N-oxy) the benzoyl peroxide was not detected. Only very small changes in IR spectra were observed upon irradiation of N-oxy 4-hydroxy-2,2,6,6-tetramethyl piperidine chemically bounded to benzilic group (BZNO) in PS matrix probably due to intramolecular quenching of benzil excited state. The fluorescence quenching of benzil derivative by N-oxy was observed in PMMA. The effective fluorescence quenching of benzil derivative in the presence of N-oxy in 1,1,2-trochloro-trifluoro ethane solution was observed too.
References:
COMBINED HINDERED PHENOL/HAS STABILIZERS ON THE BASIS OF DIISOCYANATES
CS. KÓSA,a Š. CHMELA,a G. THEUMERb, W. D. HABICHERb
aPolymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 842 36 Bratislava, Slovak Republic, upolkosa savba.sk
bInstitute of Organic Chemistry, Dresden University of Technology, Mommsenstrasse 13, 01062 Dresden, Germany
Different additives are used to protect the polymeric materials during their melt processing and against the atmospheric attacks.
The oxidative degradation of polyolefines during melt processing can be inhibited effectively by use of a small quantity of sterically hindered phenols as primary stabilizers. They act as scavengers of the oxygen centered alkoxy radicals. On the other hand they are not able to provide long-term light and heat stability.
The class of Hindered Amine Stabilizers (HAS) is the most effective long-term light and partially heat stabilizers. They act by a multifunctional mechanism.
Mixtures of hindered phenols and hindered amine stabilizers (HAS) are frequently used to prevent the polymer against degradation process. Major problem arising from physical mixture of low molecular-weight stabilizers is their physical loss, uneven distribution in the polymer matrix and poor compatibility. This problem can be solve by application of multifunctional additives with higher molecular weight prepared by connection of two or more stabilizing structures in one molecule. This combination is expected to improve the stabilizing activity by synergistic effect. Utilization of the reaction of isocyanate group of di- (or poly-) isocyanates is a convenient method for the synthesis of multifunctional stabilizers.
Diphenylmethan-4,4’-diizocyanate (MDI), and dicyclohexylmethan-4,4’-diizocyanate (CDI) have been used as linkers for the synthesis of new combined hindered phenol/HAS stabilizers. Symmetrical phenol/phenol and HAS/HAS type stabilizers were prepared too. The photo-stabilization efficiency of synthesized stabilizers has been investigated.
It was found, that the photo-stabilization efficiency depends on the structure of HAS an also on the used diisocyanate. While in the case of MDI derivatives the photo-stabilization efficiency increases in order TMP > ATP > PMP > BATP, in the case of CDI derivatives in order ATP > TMP > BATP > PMP. Derivatives of CDI show for all HASes higher efficiency than the similar derivatives of MDI.
influence of molecular structure on Chemical and physical factors that determine the stabilizing efficiency of hindered amines
L.Yu. Smoliak, N.R. Prokopchuk
Belarusian State Technological University, 13-A Sverdlova str., 220050 Minsk, Republic of Belarus
E-mail: L_Smoliak Yahoo.com
The investigations on mechanism of hindered amines (HA) stabilizing action describe it in general as a manifestation of two groups of factors. The chemical (or ”primary”) aspects of HA-stabilization efficiency are reactions of stable nitroxyl radicals (NRs) which interact with alkyl radicals (R●) and are regenerated in a reaction with alkoxyl radicals (RОО●). The chemistry of the HA and NR activity does not allow to explain a considerable difference in efficiency of stabilizing activity for the substances of this class.
The second group of factors that can influence on HA stabilizers activity is the physical or ”secondary” aspects of stabilization. According to the physical aspects conception, the stabilizing efficiency depends immediately on the ratio S2/D, where S is the additive solubility in polymer and D is the diffusion coefficient. Three most important requirements to an effective stabilizer from HA class have been inferred: the minimum diffusion, the high solubility and a homogeneous distribution of the stabilizing groups in polymer.
Nevertheless, many aspects of this mechanism including the relationship between the structure of the stabilizer molecule and its efficiency have no profound foundation and are often merely speculative until now.
The experimental testing of efficiency as photo- and thermal stabilizers and measurement of S and D in polymers for a series of HA substances have allowed to clarify some aspects of the influence of chemical and physical factors on the efficiency and their connection with molecular structure. The multiplicity of HA groups in one molecule as well as various substitutions of 2,2,6,6-tetramethylpiperidine determine the concentration of NRs produced from HA.
From our viewpoint, the main reasons for a noticeable difference in efficiency of HA are the secondary aspects (solubility and distribution of HA groups in polymer matrix) both of which clear the way for free the HA-to-NR transformation and their effective action by chemical mechanism.
ELECTRON SPIN RESONANCE IMAGING STUDY OF DEGRADATION PROCESS IN POLYPROPYLENE AND POLYSTYRENE STABILIZED with HINDERED AMINE STABILIZER
A. MAREK, L. KAPRÁLKOVÁ, I. KELNAR, J. POSPÍŠIL, J. PILAŘ
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic
Spatial distribution of radical species generated in HAS-stabilized polypropylene and polystyrene upon exposure in an Atlas Ci3000+ weatherometer was determined by the electron spin resonance imaging (ESRI) technique. Polymer sheets containing 0.5 – 2.0 wt% of Tinuvin 770 HAS stabilizer have been exposed in the weatherometer for an overall time period of more than two months. Cylindrical samples (diameter 3 mm, length 6 mm) were made of the sheets after appropriate time periods of exposition. Time dependence of the spatial distribution of paramagnetic intermediates (nitroxides) of the sacrificial transformation of HAS in the cylinders along the irradiation direction (axial) was measured by ESRI. Significant differences between distributions observed in polypropylene and polystyrene were observed. The data available at present indicate that irradiation and oxygen diffusion affect the degradation process in both polymers in a different way due to their different chemical sensitivity and morphology.
Support from the Grant Agency of the Czech Republic (project 203/02/1243) is acknowledged.
ATMOSPHERIC AGING OF POLY[METHYL(PHENYL)SILYLENE] CONTAINING UV ABSORBERS AND PHOTOANTIOXIDANTS
O. MESZÁROŠ, P. SCHMIDT, J. POSPÍŠIL, S. NEŠPŮREK
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic
Physical properties of polysilylenes are affected by irreversible phototriggered degradation attacking σ-conjugation. To understood the chemistry of the changes arising during photooxidation, poly[methyl(phenyl)silylene] (PMPSi) was exposed in Weather-O-Meter Atlas Ci 3000+ light cycle only. Formation of siloxane, carbonyl and hydroxyl species and drop in Si-Si units was monitored using FTIR spectroscopy. The obtained results indicate complex photochemistry accounting for photolysis and photooxidation. An attempt was done to reduce the oxidative deterioration of PMPSi using selection of UV absorbers, quenchers and photoantioxidants from HAS family. It was found that the UV absorbers acting by ESIPT mechanism protect PMPSi in initial phases of photodeterioration in accordance with Lambert-Beer law. Effect of HAS was rather well expressed in reduction of accumulation of siloxane groups. We assume this effect has been based on curative activity of HAS. After analysis of the mechanisms of degradation of PMPSi and mechanisms of protective effects of UV absorbers and HAS, an optimal combination of the UV absorbers and photoantioxidants was selected. A strong cooperative effect was proved in these combinations. The results indicate that stabilizers generally effective in common thin layer coatings are able to protect also PMPSi, a polymer with specific optoelectronical properties.
MECHANICAL RECYCLING OF UNSATURATED POLYESTER-BASED COMPOSITES
D. PERRIN, L. CLERC, E. LEROY, A. BERGERET, J.M. LOPEZ CUESTA
Ecole des Mines d’Alès, CMGD, 6 avenue de Clavières, 30319 Alès Cedex, France
The objectives of this project are the mechanical recycling of SMC (Sheet Moulding Compounds) parts, made up of unsaturated polyester based composites reinforced with glass fibers and calcium carbonate fillers. Specific fractions were designed by grinding, micronization and separation steps. These fractions have been incorporated into thermoplastics polymers in substitution of glass fibers. Mechanical properties and microstructure observed by image analysis of these composites have been studied.
A former study showed the interest of the introduction in PP and PA-6 of micronized fractions produced in an industrial process of SMC mechanical recycling [1,2].
The present study is related to the optimisation the morphology and composition of SMC fractions, before reincorporating them into PP.
Two main steps were carried out:
Mechanical properties of composites containing recycled fractions and corresponding glass fiber composites are compared.
[1] J.N. Reygrobellet, J.M. Lopez Cuesta, A. Crespy, International Conference on Composite Materials, ICCM 12, Paris, France, 1999
[2] J.N. Reygrobellet, J.M. Lopez Cuesta, A. Crespy, Eurofillers Conference, Lyon, France, 1999
MECHANICALLY RECLAIMED RUBBER
A. KUTA, I. KROUTILOVÁ, V. DUCHÁČEK
Department of Polymers, Institute of Chemical Technology, Prague
Technická 5, 166 28 Praha 6, Czech Republic
Antonin.Kuta vscht.cz
A simple process of rubber recycling is based on mechanical converting of rubber waste into a thermoplastic material via kneading on a laboratory two-roll mill without any additives(1). The rubber”devulcanized” via this mechanical way is able to vulcanize again and to replace a part or raw rubber in compounds. Mechanical properties of final material depend on reclaimed/virgin rubber ratio.
Crushed rubber (from old passenger tyres, particle size from 0.5 to 3 mm) was mechanically kneaded on a laboratory two-roll mill without any additives or with 2 wt.% of an additive (a peptizer, a sulfur donor, a vulcanization accelerator). RPA 2000 (Rubber Process Analyzer) was used for rheological behaviour study of mechanically reclaimed rubber (MRR). Viscoelastic properties of reclaimed rubber depend on the time of its storage after reclaiming. Its flow properties immediately after reclaiming are sufficient for compression moulding.
Sulfur or sulfur with 2-mercaptobenzothiazole were added to MRR to obtain a course of vulcanization close to that of MRR reclaimed in the presence of tetramethylthiuram disulfide. Mechanical properties of vulcanizates containing 100 % MRR were measured and compared with these from 100 % ”pure” MRR, i.e. prepared and cured without any additives: tensile strength 7 – 8 MPa and 3.5 MPa, respectively; elongation at break 150 – 250 % and 215 %, respectively; hardness 64 – 68 Sh A and 56 Sh A, respectively.
(1) Kuta A., Ducháček V.: A Simple Process for Rubber Recycling. Recycling of Polymers, 38th Microsymposium. Summaries of lectures and poster contributions, p. P 5, Prague 1997.
PET RECYCLING BY REACTIVE AND FOAMING EXTRUSION PROCESSES
S. CIBELLI, S. MONTESANO, L. DI MAIO, L. INCARNATO
Department of Chemical and Food Engineering, University of Salerno, Via Ponte don Melillo, 84084 Fisciano (SA), Italy
The recycling of PET is a relatively new and increasingly active area presenting several challenges. In this work polyethylene terephthalate (PET) foams based on recycled material were developed, with the aim of improving the foam extrusion process, as well as that of obtaining a product with favourable cost/performance characteristics. Since the PET foaming process is highly sensitive to resin rheology, chemical modification by chain extension was necessary to improve foamability. The reactive extrusion process was carried out to increase the molecular weight of PET industrial scraps with low intrinsic viscosity (IV = 0.48 dl/g). Pyromellitic dianhydride (PMDA) was used as a chain extender due to its melting point (approx. 283°C) near to that of PET. For the foaming extrusion process, a chemical blowing agent (CBA) was used. The two processes of chain extension and foaming were performed both sequentially and simultaneously. PET foam samples were characterized from a physical and mechanical point of view. Moreover, a morphological analysis was performed using scanning electron microscopy (SEM). Panels for construction, furniture and transportation are all potential applications of extruded foamed PET.
References:
THERMAL DEGRADATION OF RICE HUSK – SCRAP TYRE BLENDS
P.M. STEFANI1, D. GARCÍA2, J. LÓPEZ2, A. JIMÉNEZ3
1Facultad Regional Concepción del Uruguay (UTN), Ing. Pereira, 676, E3264BTD, Concepción del Uruguay, Argentina. e-mail: stefanip frcu.utn.edu.ar
2Universidad Politécnica de Valencia. Depto. Ingeniería Mecanica y Materiales. Paseo del Viaducto, 1, 03801, Alcoy. Spain. e-mail: jlopezm mcm.upv.es
3University of Alicante. Department of Analytical Chemistry. PO Box 99, 03080, Alicante. Spain. e-mail: alfjimenez ua.es
The disposal of used automotive tyres has caused many environmental and economical problems to most countries. Most of the scrap tyres are dumped in open or landfill sites. As known, tyre is made of rubbery materials in the form of Cx Hy with some fibrous materials. It has high volatile and fixed carbon contents with heating value greater than that of coal. But some environmental concern has raised during the last years regarding incineration of tyre rubber (1). Therefore, the proposal of recycling of tyres once used must be seriously considered. Some recent studies have proposed the use of recycled tyre rubber to produce thermoplastic elastomers (2). However, despite promising results, this possibility seems difficult for industrial use as the resulting product is still too expensive. The addition of another waste product for reducing costs seems necessary. We propose the use of rice husk as filler for this purpose(3). Thermal decomposition of rice husk occurs in various steps in the temperature range between 150 and 550°C. This complex process is the result of the overlapping of thermal decomposition of the three major constituents that are common in all lignocellulosic materials, i.e., hemicellulose, lignin and cellulose. Hemicellulose is degraded at temperatures between 150 and 350°C, cellulose from 275 to 380°C and lignin from 250 to 550°C. The degradation process of major constituents of scrap tyres or their combinations is observed at temperatures between 340 and 550°C. For blends, the addition of rice husk (maximum 25%) produces an increase in the weight loss rate. This effect is higher as the amount of rice husk increases. Apparent kinetic parameters were also studied by several isoconversional methods. We observed that the addition of rice husk produces a decrease in apparent activation energy for low conversions (up to 0.6). For higher conversions this decrease was not so clearly observed.
References.
Rapid method for estimation of life-time of recycled polymers
N.R. Prokopchuk, O.Ya. Tolkach, L.Yu. Smoliak
Belarusian State Technological University, 13-A Sverdlova str., 220050 Minsk, Republic of Belarus
E-mail: L_Smoliak Yahoo.com
In spite of the rich world experience in studying polymers degradation in real-life and artificial conditions, the problem of reliable prognostication of their longevity is far from being solved.
A new method for polymer materials longevity prognostication has been developed at Belarusian State Technological University under the supervision of prof. Nikolay R. Prokopchuk. This method is based on the following equation:
where t – longevity in days; ED – effective activation energy of thermooxidative degradation, calculated by Broido method on the basis of the TGA data; a and b – empirically determined coefficients.
We have proved (theoretically and experimentally) that an effective activation energy of thermooxidative degradation (ED) can be used as parameter, connected with chemical structure of polymer material on the one hand, and the time of the loss of a polymer item working properties under the influence of polymer degradation on the other. ED is a potential barrier of energy, required for chemical bond rupture. As long as the polymer degradation is a process of accumulation of such ruptures, parameter ED is directly connected with material longevity. Since ED is a part of the equation for longevity, it must be set as a basic parameter for incoming inspection of raw polymer materials. Minimum value of ED is not to be lower than 98-100 kJ/mole for PELD.
The method is suitable both for virgin polymer materials and for polymer wastes destined to be recycled and allows the producer not only to estimate the ‘history’ and quality of polymers (that is most important for recycling) but also to predict their longevity in determined exploitation terms (solar UV, high temperatures, stress).
The method is being considered to be included in the Belarusian state standards for prognostication of polymer pipes and PVC profiles longevity.
THERMAL RECYCLING OF WASTE POLYOLEFINS
N. MISKOLCZIa, L. barthaa, GY. deáka, A. GEIGERa, SZ. BÍRÓa, B. JÓVERb
a University of Veszprém, Department of Hydrocarbon and Coal Processing, Hungary
b MOL, Hungarian Oil and Gas PLC, R&D
Polymer waste can cause increasing environmental problems in the world. The problem of waste material disposal became more and more important from environmental aspects. Chemical recycling is one of the perspective possibilities of the industrial utilization. The volatile liquid fraction produced by a cracking method might be used as synthetic white spirit or diesel fuel, which have low sulfur and nitrogen content and furthermore high cetane index. Waste polyolefins (polyethylene and ethylene-propylene copolymer) were investigated in our research by the use of two techniques: in a batch reactor and a continuous tube reactor.
The cracking reactions were processed at two different temperatures (420 and 450°C in batch case or rather 500 and 550°C in the tube reactor). The products from the tube reactor were distilled into three fractions with different boiling point range and properties. The fraction F1 has properties of a white spirit (40-200°C), and fraction F2 of a diesel fuel (180-350°C). The residue obtained after removal of the lighter hydrocarbons was fraction F3 (350°C-). The residue and liquid together contain 28-32% lighter F1 and heavier F2 fractions after cracking at 500°C opposite the 36-40% at 550°C. On the other side when only the residue was distilled fraction F1 was 3% and fraction F2 10-14%. It means, that the residue contains mainly fraction F1 and the liquid fraction F2. No differences were observed with respect to the polymer wastes types. The main components were C3 and C4 hydrocarbons in the gases, but the amount of them were depended of the polymer type. The olefin content of the fractions and the distribution of the double bonds were determined by IR spectroscopy and I/Br number of the fractions. All liquid fractions had significant -olefin content. The liquid product yields and some properties of them did not change as function of the types of the feed polymers. Liquids produced by both methods had low sulfur and nitrogen content. The ratio of –CH2/–CH3– groups had smaller value in case of ethylene-propylene copolymer waste. The chemical structure of waste polymers could be cause these results, because cracking of EPC resulted more branching molecule structure in liquids.
PYROLYSIS GC-MS STUDIES ON THE THERMAL DEGRADATION OF BIODEGRADABLE POLYMERIC MATERIALS AND BIOCOMPOSITES
R.A. RUSECKAITE1, A. FRAGA1, A. JIMÉNEZ2
1Research Institute of Material Science and Technology (INTEMA), University of Mar del Plata, Juan B. Justo 4302, 7600- Mar del Plata, Argentina.
e-mail: roxana fi.mdp.edu.ar
2University of Alicante. Department of Analytical Chemistry. P.O.Box 99, 03080, Alicante, Spain. e-mail: alfjimenez ua.es
The search of new strategies for manufacturing of products based on plastic materials with high performance properties and real possibilities of biodegradation leads to consider biopolymers and biodegradable synthetic polymers as promising raw materials for some processing operations and uses. However, some problems, such as their high costs and the incomplete information on some of their properties, are inherent to their current use. Among all advantages in the use of biodegradable polymers, the most important is the possibility of biodegradation, which raises considerable interest form the environmental and industrial point of view. Some researchers have recently studied the thermal degradation of these polymers but there are still many efforts to perform for a complete thermal characterization of such materials. Other current research efforts are focused on the determination of pyrolysis products. The main goal of this work is a complete thermal characterization of a series of mixtures based on some biodegradable polymers, such as poly-(-caprolactone) (PCL) and poly-hydroxy-butirate (PHB), with microcrystalline cellulose (MC) and sisal fiber (SF) by pyrolysis coupled to GC-MS, in order to predict the thermal behavior of cellulose derivatives -reinforced biodegradable matrixes. Pyrolysis products were obtained at different temperatures near degradation and their comparison with those products obtained for pure PCL and PHB was carried out. Many of the peaks obtained were considered as superposition of those present in the different components of the biocomposites. However, some interactions can be considered, as differences in pyrograms at different temperatures near degradation can be attributed to the addition of natural fibres to matrix materials.
References.
E. Jakab, G. Varhegyi, O. Faix, J.Anal.Appl.Pyrolysis., 56 (2000) 273.
Y. Matsuzawa, M. Ayabe, J. Nishino, Polym. Deg. & Stabil., 71 (2001) 435
R. A. Ruseckaite, A. Jiménez, Polym. Deg. & Stabil. (2003), in press
Study of stability of rubber bitumens
A. Geiger1, Sz. Bíró1, L. Bartha1. Gy. Deák1, E. Fantó2, N. Miskolczi1
1University of Veszprém, Department of Hydrocarbon and Coal Processing, Veszprém, Hungary
2MOL Hungarian Oil and Gas PLC, R&D, Százhalombatta, Hungary
The separation of the rubber and bitumen pahses in the rubberbitumen asphalting could generally cause problems both in the dry or wet technologies. Because of the difference of the density between the rubber and bitumen the almost dissoluted phases often can be separated.
This is a disadvantageous property in road construction, thus strict requirements are standed against the storage stability of modified bitumens.
In our research rubber-bitumen compositions were prepared in two technological steps, using different antisetting additives. In the first step at 180-230 oC crumb rubber and in some cases dispersants were added to the base bitumen. The next step of the batch type technology was a high shear mixing.
The effect of the additives (observing the economy), and properties of rubberbitumen samples after storage were studied. The properties of these compositions were compared to rubberbitumens prepared without dispersant. After the measurement of storage stability, viscosity and softening points of the lower and upper parts of the samples were determined. It was demonstrated by both of the softening points and dynamic viscosities (135 oC), that stable, non settling rubberbitumen could only be formed by usind these additives. The optimed concentration level of an antisetting additive for rubberbitumens were determined in the concentration intervall of 0-3 m/m %.
RHEOLOGICAL STUDY OF RUBBER CONTAINING BITUMINOUS COMPOSITIONS
SZ. BÍRÓa, A. GEIGERa, R. PERLAKIb, L. BARTHAa, GY. DEÁKa, E. FANTÓc, N. MISKOLCZIa
aUniversity of Veszprém, Department of Hydrocarbon and Coal Processing, Veszprém, Hungary
bÁKMI KHT, Veszprém, Hungary
cMOL Hungarian Oil and Gas PLC, R&D, Százhalombatta, Hungary
In the last ten years the study of the rheological properties of bitumens has got more importance than the classical standard test methods. By these measurements the prediction of the behaviour of practical use became more realistic than ever before.
The viscoelastic, non-newtonian properties of bitumens can be described by a lof of parameters and their analysis.
Thus there are possibilities to analyse the rheological properties of the bitumens both below and above the softening point. The study of the properties above the softening point is important because of laying asphalt, and below the softening point because of apshaltmechanics.
Rubber-bitumen compositions were prepared by a new method from various raw materials, and their flow properties were studied.
The effect of different bitumens was determined. The viscosity of the compositions proved, that the rubber modified bitumens were applicable at 135oC, and at 180 oC they were pumpable.
The relaxation results were well characterized by the Burgers rheological model that also proves, that the rubberbitumens have viscoelastic properties.
The proportios samples had the same dependence on temperature and frequency, differences were experinced only in inflexibility.
It was found, that the ratio of the base bitumens has a major effect on the properties of rubberbitumens for paving.
Corrosion resistance of both filled and reinforced vulcanizates based on KRASOL LBD
P. RYBYŠAR, J. VRAŠTIL, M. VEČEŘA, L. PROKŮPEK
Department of Polymers, Institute of Polymeric Materials, University of Pardubice, nám. Čs. Legií 565, CZ-530 10 Pardubice, Czech Republic
Crosslinked liquid polybutadienes have excellent electrical insulation properties.
Used materials for this work are based on low molecular weight polybutadiene rubber KRASOL LBD 3000 (made by Kaučuk Kralupy, a. s.), with isocyanate end groups.
The resins were prepared by reaction with glycerol as a bonding agent and sulphur as a vulcanizing agent. Before vulcanization the rubber was filled with powdered fillers (carbon black, limestone, two types of titanium dioxide), and E-glass reinforcements (woven fabric V301 and non-woven fabric Vlies70).
These resins were tested for chemical resistance in followed environments: demineralized water; 40% wt. water NaOH solution; 30% wt. water H2S04 solution; 50% wt. water C2H5OH solution.
Changes in weight, hardness, and modulus in bend were measured after defined time in each environment. The resulting properties of tested materials were good elasticity, good resistance against chemicals (water solutions of acids and hydroxides). On the other hand faster diffusion of ethanol solution into filled resin caused much greater decreases of studied properties.
POLYMER SURFACE TENSION AT STABILITY LIMIT
J. JŮZA
Department of Polymer Materials, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic
The temperature ranges of the published surface tension data are restricted for various reasons given by authors' interest, apparatus, and measured materials. Surface tension data are seldom published for the temperatures, when the polymer is not chemically stable, although most authors know them very well. Nevertheless, the knowledge of surface tensions for materials that degrade or decompose might be often interesting, even if their composition is not known and defined.
The behaviour of surface tension is affected by different processes, which change properties determining surface tension such as molar mass, density, cohesive energy and polarity. As it can be seen from relationships predicting surface tension [1-3], degradation and depolymerization should generally lead to a decrease in surface tension, whereas crosslinking or formation of polar products tends to increase the surface tension. Considering measurements using the pendant drop method, an intermediate result, the ratio of the surface tension to the drop density (γ/ρ), is more reliable and available even if density is unknown. Since n>1 in the McLeod equation, also γ/ρ should increase with increasing density. γ/ρ increases with the chain length if the chain is sufficiently long and if monomer and polymer surface tension differ sufficiently, which is usually true.
As to materials measured in recent years, most polyethylene, polypropylene, and polystyrene samples kept a nearly linear (with inconclusive deflection) dependence of surface tension on temperature, although some of them markedly changed their appearance turning brown. Polyethylene Liten BB 29 could not be measured due to the non-droplike shapes formation above 200 °C. The behaviour of maleinized liquid rubbers Krasol suggests possible crosslinking above 160 °C.
This contribution illustrates the surface behaviour of some polymers at temperatures, when they are no longer stable.
Acknowledgement: The data used were acquired in the frame of projects C4050601 (Grant Agency of Academy of Sciences of the Czech Republic) and IBS4050008 (Academy of Sciences of the Czech Republic)
[1] Wu S.: Polymer Interface and Adhesion. M. Dekker 1982.
[2] Roe R.J.: J. Phys. Chem. 72, 2013 (1968).
[3] LeGrand D.G., Gaines G.L., Jr.: J. Colloid Interface Sci. 31,162 (1969).
LOW-CROSSLINKED ALKYL METHACRYLATES - SUPERABSORBENTS FOR NONPOLAR LIQUIDS
J. HRADIL, J. KOVÁŘOVÁ
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, CZ-162 06 Praha 6, Czech Republic
Superabsorbents for water media imbibers, expanda polymers are widely used. Hydrophobic superabsorbents, which absorb a high quantity of non-polar or medium-polar organic compounds, have not been so often investigated. Nevertheless, they are important for decontamination of spills of dangerous liquids such as oil, kerosene, or organic solvents.
Bead size copolymers and terpolymers of butyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, styrene, 3(4)-methylstyrene, or 4-tert.-butylstyrene, crosslinked with divinylbenzene or ethylene dimethacrylate (0.1-5 wt.%) were prepared by suspension radical polymerization . Polymerization yield is affected by the chemical composition, crosslinking degree, and by the monomer/water phase ratio. The polymer particle size characterized by mean particle size, polydispersity and cumulative and differential distributions is affected not only by the intensity of stirring, but also by the type of monomers used and concentration of suspension stabilizer.
The imbibing properties of prepared polymers were studied on sorption of 1,2-dichloroethane and toluene. They on the chemical nature of used monomers, on degree of crosslinking and on polymer particle size. In polymer imbibing, compared with polymer swelling, the amount of imbibing liquid in the interstitial between particles is enhanced. Therefore, depending on the surface tension, also the particle diameter is important for maximum imbibing. Polymer imbibing capacities reach values of 22 - 23 ml toluene/g. The imbibing capacity for 1,2-dichloroethane and toluene is similar. The chemical nature of the polymers is reflected in interaction parameter and in their glass transition states. The glass transition temperature gives information on mobility of polymer chains. Sometimes literature recommends, for sorption of non-polar liquids, materials with the glass transition temperature Tg lower than 0 °C, sometimes higher than 27 °C. A Terpolymer of butyl methacrylate-3(4)-methylstyrene-divinylbenzene, which have a rather good imbibing properties, has the Tg 51 °C. The Tg of the prepared samples increases in the order: BuA<BuMeAMeSt<BuMeABuSt<BuSt.
The authors acknowledge the Grant Agency of Czech Republic for financial support (grant No 104/03/0680).
REPROCESSING OF AGED POLYMERS: EFFECT OF AGING CONDITIONS ON THE RESULTING PROPERTIES
S. LUZURIAGAa, J. KOVÁŘOVÁb, I. FORTELNÝb
a Department of Macromolecular Chemistry, Faculty of Natural Sciences, Masaryk University, Kotlářská 2, CZ 611 37 Brno, Czech Republic
bInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovského nám. 2, CZ- 162 06 Praha 6, Czech Republic
HDPE, LDPE, PP and HIPS, which form a major part of commingled plastics waste, were exposed to two different accelerated aging processes: thermo- and photo-oxidation.
Polymer samples were oven aged at 100 °C for varying periods of time or UV irradiated in a Weatherometer at l = 340nm, prior to their reprocessing (Brabender plasticorder at 190° C/60rpm during 10 min). The torque for each sample was recorded.
Chemical changes and changes in mechanical properties accompanying the gradual degradation of individual polymers under study were monitored and evaluated (DSC, FTIR, colorimetry, MFI, torque, impact tensile strength).
According to our results, LDPE and HIPS are more susceptible to thermo-oxidation than HDPE and PP, whereas, on the contrary, HDPE and PP are affected to a greater extend by UV exposure. In HDPE scission and branching reactions compete both in thermo- and photo-degradation processes. In case of LDPE scission prevails over branching during thermo-oxidation, whereas photo-oxidation of the same sample leads predominantly to branching. Scission reaction was also predominant for PP during thermo-oxidation, and it took place even faster during UV exposure. In case of HIPS photo-degradation of PS matrix is accompanied by crosslinking of the polybutadiene component at the same time.
The tensile impact strength deterioration observed for all samples, with exception of HIPS, resulted mainly from the change in Mw and molecular weight distribution rather than from a gain in crystallinity. The observed changes of MFI correlate well with changes in mechanical properties of the studied polymers. The abrupt rheological deterioration of LDPE at reprocessing after one week of thermal exposure was suppressed by re-stabilization.
Financial support from the Academy of Sciences of the Czech Republic, Grant Number AV-S4050008 is gratefully acknowledged
CHEMILUMINESCENCE DURING POLYMER OXIDATION
P.K. FEARONa, S.W BIGGERB, N.C. BILLINGHAMa
aSchool of Chemistry, Physics and Environmental Sciences, University of Sussex,
Brighton BN2 9QJ United Kingdom.
bSchool of Life Sciences and Technology, F008, Victoria University of Technology, PO Box 14428, Melbourne, 8001 Australia
Although the chemiluminescence (CL) technique has been widely accepted as an adequate measure of the extent of oxidation in polymeric materials, there has been much discussion as to the chemical source of this luminescence. [Zlatkevich 1985] Since degradation of polymers takes place under the influence of oxygen and at elevated temperatures, the oxidative process will proceed through free radical interactions. Given the size of these molecules and the complexity of the interacting reactions, investigation of any of the proposed mechanisms is quite difficult. We have used carbonyl index and oxygen uptake methods to compare those results with standard CL data obtained from oxidising polymer.
The carbonyl index has been used to monitor the extent of degradation in unstabilised polypropylene. The resulting profiles were fitted to their corresponding chemiluminescence curves. It was found that, in agreement with theory, the carbonyl index followed the integrated CL curve at all temperatures investigated, thus lending support to the Russell mechanism. These results conflict sharply with recently published results [Blakey 2001], which had reported a better fit to the non-integrated intensity profile. It was shown that care must be taken when analysing CL data and it is suggested that analysis should be confined (restricted) to that region which lies before the peak maximum for the luminescence.
Oxygen uptake yielded unambiguous OIts which followed the expected trend over the entire temperature range tested. It was shown that comparisons of the O2 data to the integrated CL is sensitive to the point of termination of the analysis. There was a strong correlation between O2 uptake and ΣCL especially in the early oxidation period. The absorption of O2 per photon emitted has been calculated and found to be temperature dependent. This raises the question as to whether changes in the kinetic chain length with temperature or a temperature dependence of the quantum yield or indeed a combination of both are contributing to this phenomenon.
References:
(1) Zlatkevich, L. In Polymer Stabilisation and Degradation; Klemchuk, P., Ed.; American Chemical Society: Washington, DC, 1985; Vol. 280.
(2) Blakey, I.; George, G. A. Macromolecules 2001, 34, 1873-1880.
COMMENTS ON THE REPRODUCIBILITY OF CHEMILUMINESCENCE TESTING
P.K. FEARONa, L. MATISOVA RYCHLAb, J. RYCHLYb, S.W. BIGGERc,
N.C. BILLINGHAMa
aSchool of Chemistry, Physics and Environmental Sciences, University of Sussex,
Brighton BN2 9QJ United Kingdom
bSlovak Academy of Sciences, Stefanikova 49, 814 38 Bratislava, Slovakia
cSchool of Life Sciences and Technology, F008, Victoria University of Technology, PO Box 14428, Melbourne, 8001 Australia
Recent advances in light collection techniques and the use of innovative analytical software have made facile collection and analysis of the chemiluminescence (CL) emitted from oxidising polymers possible. [Billingham, 1985] In practice the typical experiment involves heating a sample either isothermally or dynamically under regulated gas flow and strict thermostatic conditions in a light-excluded oven. Therefore, the apparatus specifications necessary for the successful measurement of the CL from an oxidising polymer are relatively straightforward. The fundamental requirements are an accurate thermostatic plate, a light-tight sample chamber, a sensitive light detector and an accurate counting device. [ Kohler, 1998 ]
The increase in the number of publications that present CL data reflects the increasing acceptance of the technique among researchers. These data are always presented on the assumption that a measurement taken in one institution directly corresponds to one which has been obtained at another. In the absence of an industry standard this cannot be taken for granted. It is therefore important to determine to what extent results can be carried forward from instrument to instrument and equally from institution to institution. [Rychla, 1995]
To this end data collected using a Mettler chemiluminescence instrument at Sussex University were compared to data obtained by running the same polymers under similar conditions on a different type of CL instrument, a Lumipol-2 at the Slovak Academie Vied in Bratislava.
An excellent correlation was found for these inter-laboratory experiments.
References:
(1) Billingham, N.C.; O'Keefe, E.S. Advances in the stabilization and controlled degradation of Polymers, Lucerne 1985; Technomic Publishing Basel; 1-8.
(2) Kohler, D.R.; Krohnke, C. Polym. Deg. Stab. 1998, 62, 165 -173.
(3) Matisova-Rychla, L.; Rychly, J.; Verdu, J.; Csomorova, K. Polym. Deg. Stab. 1995, 49, 51-55
Yu-Zhong Wang, Ke-Ke Yang, Xiu-Li Wang
Biodegradable aliphatic polyesters
Abstract not supplied
Qian Zhou, Yao Zheng, Yu-Zhong Wang
Catalytic degradation of mixed polyolefin plastics into pyrolytic
oil via composite catalysts
Abstract not supplied
RECYCLING OF POLYCARBONATE CAR HEADLIGHT LENSES
J. RYBNICEKa, J. STEIDLa, Z. KORINEK
aCzech Technical University in Prague, Faculty of Mechanical Engineering, Department of Materials Engineering, Karlovo nam. 13, 121 35 Prague 2, Czech Republic
The impact of the coating on reprocessed polycarbonate was studied in an attempt to evaluate the re-usability of the scrap generated during the production of headlight lenses. The evaluation was based on changes in the fracture behaviour and toughness of polycarbonate. The parameters employed were dynamic strain release rate Gd,i, and the Izod impact test. Fracture surfaces were observed by scanning electron microscopy (SEM). Thermal and rheological analysis were also performed. It was found that the reprocessed polycarbonate without coating retains its properties well. The coating creates non-homogeneously dispersed particles, which act as stress concentrators causing slight embrittlement of the material. The coating substantially decreases the Izod notched impact strength, but according to linear elastic fracture mechanics (LEFM), only slightly reduces the fracture energy Gd,i of the reprocessed material. TGA analysis showed a rapid weight loss of the coating at elevated temperatures, which can lead to an undesirable impact on the environment during processing. Yellowing of the material was also observed.
Key words: polycarbonate, reprocessing, polyurethane acrylate silicon-modified coating, fracture energy, dynamic strain release rate, toughness, rheology, fractography.
Y. Kann
Chemiluminiscence study of the stabilization of PVC
Abstract not supplied
