Effect of a diamine additive on the structure-property relationships of rim polyurethane elastomers

✍ Scribed by John Blackwell; Jeffrey R. Quay; Robert B. Turner

• Publisher: Society for Plastic Engineers
• Year: 1983
• Tongue: English
• Weight: 387 KB
• Volume: 23
• Category: Article
• ISSN: 0032-3888
• DOI: 10.1002/pen.760231505

✦ Synopsis

Abstract

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.