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A series of amine terminated polypropylene oxide based thermoplastic polyureas with hard segment contents of 30%. 50%, and 70 percent were synthesized via solution polymerization and reaction injection molding (RIM). Amine terminated polypropylene oxide (PPO-NH2) of M, = 2000 was used as the soft segment and 4.4'-diphenylmethanediisocyanate (MDI) extended with diethyltoluenediamine (DETDA) a s the hard segment. These polyureas are linear, amorphous, and phase separated. Polymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical spectroscopy (DMS), small angle X-ray scattering (SAXS), and tensile testing. RIM polyureas had significantly lower molecular weights than solution polymerized polyureas. but their mechanical properties did not suffer. RIM polyureas have poorer phase separation than solution polyureas as evidenced by DSC, DMS, and SAXS, especially a t high hard segment levels. SAXS shows phase separation levels of up to 100 percent for low hard segment polyureas and down to 10 percent for high hard segment RIM polyurea. DSC found no evidence of a hard segment glass transition, and the evidence from DMS was inconclusive. In addition to polymer characterization, demolding behavior was studied. The 30 percent hard segment was always tough and elastomeric, while the 70 percent hard segment was always very brittle. The 50 percent hard segment showed the greatest variation in properties, ranging from very brittle to very tough as mold temperature and in-mold time were increased. Demold brittleness is explained by the presence of low molecular weight DETDA/MDI oligomers on demolding, which continue to react on aging.

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SYNOPSISA series of copolyureas containing 50% by weight hard segment have been formed by RIM. The hard segment structure was systematically varied to investigate the effects of urea group density, hard segment crosslinking, relative reaction rates, and to compare the properties of aromatic and aliphatic hard segment materials. In each case the soft segment was based on a 2000 molecular weight polyether diamine. The RIM materials formed ranged from flexible elastomers to brittle plastics depending on composition and were characterized by SAXS, DSC, DMA, tensile stress-strain and fracture mechanics studies. SAXS, DSC, and DMA showed that microphase separation had occurred to give materials with a nonequilibrium morphology. DMA and tensile stress-strain studies showed the small strain properties to be very sensitive to the volume fraction of glassy material whereas the ultimate properties were dependent on chemical structure of the hard segment. Fracture properties were determined using the single-edge notch technique. In most cases ductile failure occurred with G, > 2.5 k J m-* and the fracture surfaces showed gross yielding and tearing. In the case of the copolyurea with the highest urea group content, brittle fracture occurred with G, = 0.06 kJ m-'.

AbstractsFrom a technical viewpoint there are two choices. Firstly, a drop-in replacement for CFC-11, requiring no fundamental changes in terms of polyurethane foam processing; HCFC-141b, in this case, is a potential intermediate blowing agent. The second choice is to use blowing agents with boiling points below room temperature, referred to in this paper as Low Boiling Blowing Agents, or LBBAs. This option introduces some processing complications, but potential transitional materials such as HCFC-22 and HCFC-142b are readily available. This paper reports on ICI Polyurethanes' Research and Technology developments with a novel technology based on these HCFCs. The technology results in foams with reduced thermal conductivities compared to foams blown with reduced CFC-11 systems. Different aspects of the technology, including thermal conductivity performance, energy consumption data and relevant physical properties are discussed.Measurements of apparent thermal conductivity for specimens of rigid polyisocyanurate (PIR) foam cut from a commercial insulation product and aged in air at 60 ° C and different humidities are presented. Eight specimens, nominally 600 by 600 mm, were prepared from two boards (1.2 by 2.4 by 0.05 m) of rigid PIR foam blown with trichlorofluoromethane (CC13F) and having permeable organic-inorganic facers. Facers and excess foam were removed by sanding the specimens to a thickness of 27.9 f 0.1 mm. Four specimens were placed in ambient conditions of 22 ° C and 40% relative humidity (RH). The remaining four specimens were each placed in one of the following environments: (1) 60°C and < 10% RH; (2) 60 ° C and 40% RH; (3) 60 ° C and 60% RH; and, (4) 60 ° C and 75% RH. Measurements of apparent thermal conductivity were conducted at 24 ° C and a temperature difference of 22 ° C using a heat-flow-meter apparatus conforming to ASTM Test Method C 518. Measurements were conducted for a period of 357 days at approximately 50-day intervals. Aging curves of specimen mass, volume, density, and thermal conductivity for rigid PIR foam are presented, and implications of changes in these properties are discussed in the paper. Supplemental measurements using Fourier transform infrared spectroscopy and scanning electron microscopy are also described in the paper.