SynopsisThe aqueous solution properties of alkylene oxide polymers and copolymers are related t o their interaction with water. In an attempt to better understand this behavior, differential scanning calorimetry has been employed to measure phase changes and water binding in solutions of polyethylene glycol (PEG), polypropylene glycol (PPG), and a 50/50 random copolymer of ethylene oxide and propylene oxide. PEG (mn = 3510) forms a crystalline eutectic with water at 0.48 weight fraction of polymer. The liquidus curve for water can be fit accurately using the Flory-Huggins expression for solute activity with an interaction parameter of 0.05. PPG and the random copolymer do not crystallize and thus do not form a crystalline eutectic. Based on decreases in the heat of fusion of free water with added polymer, PEG binds more water than the copolymer which binds more water than PPG. The estimated hydration numbers per polymer segment are 1.5 for PPG, 2.3 for the copolymer, and 2.7 for PEG.

SynopsisA series of polyether-based thermoplastic polyurethanes, varying in hard-segment content between 20 and 80 wt. %, was prepared using an (oxypropylene-oxyethylene) diol of mn = 2000 as the soft segment and 4,4'-diphenylmethane diisocyanate extended with 1,4-butanediol as the hard segment. Physical-mechanical, dynamic-mechanical, and specific heat (DSC) data are used to elucidate the mechanical and morphological behavior of these materials. The polyurethanes varied from soft elastomeric (continuous soft phase) to high-modulus plastic (continuous hard phase) and showed changes in their tensile properties a t about 60% hard-segment content, possibly due to phase inversion.

The production and use of slow recovery “viscoelastic” polyurethane foams have increased rapidly over the past few years. Their unique performance characteristics, which include shape conformance, vibration and sound damping, and energy and shock absorption, make these the foams of choice for many diverse applications such as pillows, mattress toppers, automotive trim, sports and medical equipment, and ergonomic cushions and pads. These diverse applications require a wide range of foam grades with tailored performance properties. New polyol and formulating technology is being developed to meet the increased demands for improved processing, wider grade latitude and improved performance properties of viscoelastic foam. This paper reports the results of systematic experimental design studies that were conducted in the laboratory to help develop this technology. A key advance is the development of polyol compositions that enable the production of high quality, soft viscoelastic foams at 100 index and above. This eliminates processing inconsistencies associated with low index foaming, and yields foams with superior performance characteristics such as improved compression sets, reduced discoloration, and finer cell structure with improved feel. The design studies also identified formulating routes to optimize key foam performance features such as low resilience, slow but complete recovery, maintenance of slow recovery characteristics with use, reduced temperature sensitivity, good airflow, and good strength properties. The results of machine foam studies will be presented along with additional foam performance results.

A series of polyether-based thermoplastic polyurethanes, varying in soft segment molecular weight and hard segment content was prepared and studied. Poly(oxypropyleneoxyethylene) diols of M n of 1000, 2000, 3000, and 4000 were the soft segment polyols. The hard segment, 4,4'-diphenylmethane diisocyanate (MDI) extended with 1,4-butanediol (BDO), and also the soft segment content were varied from 20 to 80 weight percent. Physical-mechanical, thermal (DSC) and dynamic-mechanical property data are used to elucidate the mechanical and morphological behavior of these polymers. Two distinct phases are detected in most of the polymers. The Tg of the amorphous soft phase decreases with increasing polyether molecular weight and is relatively unaffected by soft segment content except at very low levels (≼ 30%). Hard segments apparently separate into ordered structures which melt between 150 and 220°C. The melting points and the heats of fusion generally increase with hard segment content and soft segment M n . Soft segment molecular weight also has a significant influence on the mechanical properties of the polymers. In general, the ambient flexural moduli and the dynamic moduli (E') increase with increasing soft segment M n and the modulus/temperature curve is flattened.

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