Polyurethanes were prepared from pure 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butane diol (BDO) or 1,2-ethane diol (EDO) and α,ω-hydroxyl poly(propylene oxide) (PPO) by reaction injection moulding (RIM). Hard segment (MDI + BDO or EDO) level was 45-50 wt%. The PPO had about 20% ethylene oxide copolymerized in at the chain ends to provide 80% primary OH end groups. Mn was varied from 2000 to 4000. Dibutyl tin dilaurate catalyst and mould temperature were varied. Dynamic mechanical, wide-angle X-ray, differential scanning calorimeter, molecular weight and tensile elongation measurements were made on the RIM polyurethanes. At low reaction rates (low catalyst or temperature) highly crystalline, well phase separated but low molecular weight polymers were produced. At high catalyst or temperature levels more poorly phase separated but high molecular weight, tough polymers resulted. Higher Mn PPO gave better phase separation and EDO gave higher melting temperatures. Preventing hard segment crystallinity by substituting asymmetric MDI or glycols resulted in phase compatibility.
Bibliographical noteFunding Information:
This work was supported by Industry University Cooperative funding from the National Science Foundation, Grant NSF-CPE-8118-232, the General Motors Corporation and the Union Carbide Corporation. The authors are also indebted to Drs D. Spence and J. Ferrarini from Rubicon Chemicals, R. Lloyd from Texaco Chemicals, J. O'Connors from Olin Corp. and R. Gerkin and L. Lawler from Union Carbide for providing us with the raw chemicals used in this work. Invaluable assistance by K. Dulin, J. Horns and J. Andrews in sample preparation and characterization is acknowledged. One of the authors (R.E.C.) would also like to thank the 3M Company for fellowship support through this project.
- crystalline hard segments
- molecular weight
- phase separation
- polymerization rate
- reaction injection moulding