Polimery 1993, No 3, 120
Influence of temperature (210, 215 and 220°C) and time of thermostating (4–14 min) in the plastometer barrel of the thermoplastic polyurethane elastomer (TPUR) type Desmopan 0144 on its melt flow index (WSP), apparent melt viscosity (r|„) and viscometric molecular weight (Mv) was investigated. The effect of polymer moisture was also studied. It was found that moisture content of 0.20% in polymer accelerated the degradation process of TPUR. This degradation was accompanied by a big decrease in molecular weight (37% to 63%) (even at 210°C), appearance of gas bubbles, foaming of extrudates, and a strong decrease in melt viscosity. This influence was much slighter for dry polymer (moisture content of 0,05%). A correlation was found between temperature (T), thermostating time (t) in the plastometer barrel and viscometric molecular weight (M„) of the TPUR: logMy = A + b • (1/T) + [b2 • (1 /Т) + A2) • logt where: A = 1,980; b = 1367; b2 = 375; A2 = 1,170 — for moist TPUR and A = 3,058; b = 856; b2 = 100; A2 = 0,388 – for dry TPUR.
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