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Effect of a diamine additive on the structure‐property relationships of rim polyurethane elastomers
Author(s) -
Blackwell John,
Quay Jeffrey R.,
Turner Robert B.
Publication year - 1983
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760231505
Subject(s) - materials science , crystallinity , polyol , crystallization , annealing (glass) , composite material , polyurethane , flexural strength , chemical engineering , engineering
Structural and mechanical data have been compared for reaction injection molding (RIM) polyurethanes prepared from uretonimine‐modified diphenylmethane 4,4′‐diisocyanate (MDI), ethylene glycol (EG), and a polyol (a polyether; M n ≃ 5000), in order to investigate the effect of addition of a small amount of a polyetherdiamine (PEDA; M n ≃ 400) to the reaction mixture, A series of specimens containing 18 parts and 30 parts EG, with and without the diamine additive, were examined both as‐prepared and after thermal annealing. The specimens were compared in terms of their x‐ray crystallinity, elongation, flexural modulus, impact strength, and heat‐sag behavior. All of the specimens showed evidence for crystalline hard segments, which are more abundant in the series containing 30 parts EG. The crystallinity is lowest in the as‐prepared specimens without the PEDA additive, and is increased by annealing for 1 hour at 120°C. The as‐prepared specimen with additive has a hard segment crystallinity similar to that of the annealed specimen without additive. These results correlate with the mechanical property data, which improve as a result of annealing and/or the use of a PEDA additive. It is argued that the use of the polyetherdiamine enhances the phase separation and facilitates hard segment crystallization, leading to better heat‐sag behavior. It is significant that the unannealed/with PEDA and annealed/without PEDA specimens have similar properties. Use of PEDA additive improves the green strength and impact strength of molded parts.