Evaluation of the oxidative stability of multiextruded polypropylene as assessed by physicomechanical testing and simultaneous differential scanning calorimetry-chemiluminescence

Citation
Pk. Fearon et al., Evaluation of the oxidative stability of multiextruded polypropylene as assessed by physicomechanical testing and simultaneous differential scanning calorimetry-chemiluminescence, J APPL POLY, 79(4), 2001, pp. 733-741
Citations number
31
Categorie Soggetti
Organic Chemistry/Polymer Science","Material Science & Engineering
Journal title
JOURNAL OF APPLIED POLYMER SCIENCE
ISSN journal
00218995 → ACNP
Volume
79
Issue
4
Year of publication
2001
Pages
733 - 741
Database
ISI
SICI code
0021-8995(20010124)79:4<733:EOTOSO>2.0.ZU;2-3
Abstract
Common physicomechanical tests comprising impact strength, the melt flow in dex (MFI), and the yellowness index (YI) were used to study the thermooxida tive stability of polypropylene (PP) following multipass extrusion. Differe ntial scanning calorimetry (DSC) coupled with chemiluminescence (CL) monito ring was also used to assess the stability. Three PP formulations were stud ied: ii) PP-1 containing 0.050% w/w of the phenolic antioxidant Irganox 101 0(TM), (ii) PP-2 containing 0.028% w/w Irganox 1010, 0.056% w/w of the phos phite costabilizer Irgafos 168(TM) and 0.014% w/w of the lactone processing stabilizer HP 136(TM), and (iii) PP-3 containing 0.050% w/w Irganox 1010 a nd 0.100% w/w of the phosphite Ultranox 641(TM). All formulations contained 0.045% w/w of the hydrotalcite acid scavenger DHT-4A(TM). The results sugg est that physicomechanical tests cannot reliably detect the small differenc e in the stability between PP-2 and PP-3 but can detect the larger differen ce between these and the less stable PP-1. The oxidative induction time (OI T) determined by CL monitoring(i.e., CL-OIT) is consistent with the OIT det ermined by DSC but has better reliability. The CL-OIT data suggest that PP- 3 has superior oxidative stability to PP-2 in the early stages of multipass extrusion. However, PP-2 exhibits a better resistance to yellowing. A corr elation between the CL-OIT data and each of the MFI and YI data was found. (C) 2000 John Wiley & Sons, Inc.