期刊
POLYMER DEGRADATION AND STABILITY
卷 96, 期 4, 页码 491-498出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.polymdegradstab.2011.01.018
关键词
Processing; Stability; Multiple extrusion; Polypropylene; Impact; Copolymer; Polymerization
资金
- Czech Ministry of Education, Youth and Sports [MSM 0021630501]
- Czech Grant Agency [104/07/1631]
Three commercially available polypropylene impact-copolymers (ICPP) produced by Innovene (INN), Spheripol (SPH) and Unipol (UNI) technologies were subjected to multiple extrusion using a twin-screw extruder W&P ZSK25 at 220 degrees C. Processing stability and changes in properties induced by extrusion were investigated. The materials were of similar MFR similar to 6 dg/min, similar ethylene contents similar to 7.5 wt. % and the same type and level 1200 ppm of phenol/phosphite stabilizer system was used. Ranking INN < UNI < SPH in processing and long-term (LTHA) stabilities observed was primarily related to the reactivity of catalyst residues rather than to other factors, such as contents of ethylene, quantity of extractables, EPR phase composition, levels of ash or individual elements in it. The mechanically demanding multiple extrusion conditions and consequently different extent of processing degradation, however, induced only minimum changes in morphology and impact strength of the solid ICPP matrix. Thus, regardless of changes in melt-flow properties induced by extrusions, all the three grades even after 5th extrusion at 220 degrees C exhibited Charpy notched impact strength at 23 degrees C only minimally changed. (C) 2011 Elsevier Ltd. All rights reserved.
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