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NR/PP thermoplastic vulcanizates: Selection of optimal peroxide type and concentration in relation to mixing conditions
Author(s) -
Thitithammawong A.,
Nakason C.,
Sahakaro K.,
Noordermeer J. W. M.
Publication year - 2007
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.25935
Subject(s) - vulcanization , compression set , peroxide , natural rubber , materials science , polypropylene , thermoplastic , butyl rubber , mixing (physics) , composite material , ultimate tensile strength , thermoplastic elastomer , organic peroxide , elongation , polymer chemistry , polymer , chemistry , chemical engineering , copolymer , organic chemistry , physics , quantum mechanics , engineering
Thermoplastic vulcanizates (TPVs) from natural rubber (NR) and polypropylene (PP) were studied, prepared by dynamic vulcanization during melt mixing, using various peroxides to crosslink the rubber phase. The objective was to find a proper balance between degree of crosslinking of the rubber and degradation of the PP‐phase, and the tendency of the peroxide to form smelly by‐products, in particular acetophenone. Four types of peroxides were investigated: 2,5‐dimethyl‐2,5‐di( tert ‐butyl‐peroxy) hexyne‐3 (DTBPHY), 2,5‐dimethyl‐2,5‐di( tert ‐butyl‐peroxy) hexane (DTBPH), di( tert ‐butylperoxyisopropyl) benzene (DTBPIB), and dicumyl peroxide (DCP), at two mixing temperatures: 160 and 180°C for a 60/40 NR/PP TPV. The maximum and final mixing torques are clearly related to the intrinsic decomposition temperature of the particular peroxide used, where DCP and DTBPIB turn out to be effective at 160°C, whereas the other two require a higher temperature of 180°C. The best mechanical properties, tensile strength, elongation at break and compression set are obtained at lower mixing temperature with DCP and DTBPIB, presumably due to less degradation of the NR and PP. Unfortunately, these two peroxides form more smelly by‐products than DTBPHY and DTBPH. Dependent on the requirements of the pertinent application, a balanced selection needs to be made between the various factors involved to obtain an optimal product performance of these NR/PP TPVs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007