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Brno, Czech Republic

Tochacek J.,Brno University of Technology | Vratnickova Z.,Polymer Institute Brno
Polymer Testing | Year: 2014

Correlation of accelerated ageing data with that of outdoor exposure was carried out based on the comparison of total UV radiation energy (TUVR) needed for degradation of the PP - homopolymer, random copolymer (TOT C2 = 3.2 wt.%) and impact copolymer (TOT C2 = 5.4 wt.%) compression moulded 0.5 mm films. Films were stabilized with 1000 ppm butylated hydroxytoluene (BHT), no UV stabilizer was used. Accelerated ageing was realized in a Q-Sun Xe-1 exposure chamber using a filtered xenon light source and a dry cycle. Weathering was carried out at Brno exposure site, representing the typical mid-European climate. Accelerated ageing was carried out at temperatures of 40, 50, 60 and 70 °C. In accelerated ageing, both the onset of carbonyl index (CI) increase and the point of reaching the same relative increase in CI as due to weathering were used as measures of polymer degradation. For induction periods attained at different temperatures, TUVR energies were calculated accordingly and compared to that of 6 months outdoor exposure. It was found that if TUVR of both types of ageing is to be directly compared, accelerated ageing should be carried out at temperatures of 32-36 °C. Under such conditions, the same amount of TUVR energy induces the same extent of polymer deterioration in both types of ageing and may, therefore, be used for a reliable service life-time prediction. © 2014 Elsevier Ltd. All rights reserved. Source

Smolna K.,Institute of Chemical Technology Prague | Gregor T.,University of West Bohemia | Buran Z.,Polymer Institute Brno | Kosek J.,University of West Bohemia
Macromolecular Materials and Engineering | Year: 2016

This paper reconstructs the principle of rubber incorporation in high impact poly(propylene) (hiPP) particles. The detailed information about the pores and rubber distribution inside and on the surface of hiPP particles is obtained by micro-computed tomography and atomic force microscopy. The strong effect of homopolymer origin on hiPP particle morphology and rubber distribution is demonstrated. To obtain the most homogeneous rubber distribution, the low homopolymer porosity is required. The initial particle porosity has a negligible effect on the thickness of the rubber layer on the particle surface at the medium rubber content. The rubber forms not only along the iPP primary particles and directly or close to the pores but also on or close to the particle surface rather than it flows there. The evidence for these claims is based on the systematic investigation in dependence on EPR content, homopolymer particle porosity (prepared by different catalysts) and antistatic agent deactivating catalyst close to particle surface. Based on the systematical mapping of hiPP morphology by micro-CT and atomic force microscopy, the new concept of rubber incorporation in high impact poly(propylene) particles is introduced. The rubber formation directly on or close to the particle surface is confirmed for the first time here. The effect of homopolymer porosity, rubber content, and antistatic additives on the rubber distribution is discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Source

Androsch R.,Martin Luther University of Halle Wittenberg | Monami A.,Merseburg University of Applied Sciences | Kucera J.,Polymer Institute Brno
Journal of Crystal Growth | Year: 2014

The effect of addition of 0.1 wt% phosphate-ester based alpha-phase nucleating agent on the crystallization of a random propylene-based copolymer with 3.9 mol% ethylene has been investigated by fast scanning chip calorimetry (FSC). Main purpose of the work was the evaluation of the effect of the nucleating agent on the bimodal temperature dependence of the crystallization rate of propylene-based polymers caused by a change of the nucleation mechanism from heterogeneous to homogeneous nucleation on lowering the temperature to below about 60°C. Presence of the nucleation agent in the copolymer of the present study accelerates crystallization only in the high-temperature range of predominant heterogeneous nucleation, but does not affect the crystallization rate in the low-temperature range of homogeneous nucleation. The observed decrease of the minimum crystallization half-time due to the addition of the nucleation agent, from 0.2 s in case of the unmodified copolymer to 0.04 s in case of the copolymer containing the nucleating agent, is paralleled by an increase of the critical cooling rate required to inhibit crystallization on continuous cooling to below the glass transition temperature from 102 to 103 K s-1. The study is completed by an analysis of the effect of addition of the nucleation agent on the spherulitic superstructure. © 2014 Elsevier B.V. All rights reserved. Source

Rybnikar F.,Tomas Bata University in Zlin | Kaszonyiova M.,Tomas Bata University in Zlin | Cermak R.,Tomas Bata University in Zlin | Habrova V.,Polymer Institute Brno | Obadal M.,Borealis
Journal of Applied Polymer Science | Year: 2013

This study focuses on the structure, morphology, and properties of linear polyethylene (PE) profiles manufactured by continuous extrusion. High level of chain orientation was achieved using specific flow and processing conditions. An extrusion die with semihyperbolic convergency was used to generate high percentage of elongational flow and chain extension. Simultaneously, high extrusion pressure and relatively low melt temperature led to flow-induced crystallization of PE extended chains. The structure of PE tapes consists of crystal aggregates with different level of orientation and crystallinity. © 2012 Wiley Periodicals, Inc. Source

Jakubicek J.,Tomas Bata University in Zlin | Hribova M.,Tomas Bata University in Zlin | Kucera J.,Polymer Institute Brno | Kubisova M.,Tomas Bata University in Zlin
Manufacturing Technology | Year: 2016

The homopolymer of the isotactic polypropylene (iPP) and the random copolymer of the isotactic polypropyleneand 3% ethylene (iPPE) were used in this study. Isotactic polypropylene can be prepared in α, β and γ morphologicalphases depending on its crystallization conditions. The phase β content has a strong influence on mechanical,optical and thermal properties. The samples with nucleating agents (NA) α and β were used. Various processparameters were used to prepare melted samples: two thicknesses and three different cooling regimes. Wide-angleX-ray scattering (WAXD) and scanning electron microscopy (SEM) were used to investigate the phase structure.The results show that iPP without nucleation agents (4mm, <1°C /min) has the highest crystallinity (83.7%). Thesample of iPP with β-NA (4mm, <1°C /min) has the highest phase β (61.3%); the slower cooling regime and thehigher thickness increased the crystallinity (73.3%). iPPE with β-NA (0.4mm, 15°C /min) has the lower amount ofthe phase β (33.8%); the higher thickness and slower cooling regime decreased the amount of the phase β (7.1%)however the crystalline content of iPPE (63.7%) is increased. © 2016 Published by Manufacturing Technology. Source

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