Properties and phase separation of reaction injection molded and solution polymerized polyureas as a function of hard block content

Abstract

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.

Microdispersive interfacial mixing in fast polymerizations

“…Gel permeation chromatographic analysis of an isolated product layer (Machuga, 1988) formed at a D2000-MDI interface indicated a weight-average molecular weight of about 16,000 and a polydispersity of 4. These values, similar to those obtained in RIM samples (Willkomm et al, 1988), suggest a fairly high degree of conversion in the interfacial region and thus fine, small-scale mixing of reactant species.…”

Synthesis and Characterization of New Polyurea Elastomers by Sol/Gel Chemistry

“…[26] The spray technology was not developed until the 1990s, [27,28] following the reaction injection molding technique. [29][30][31] In both techniques, the two components are processed using specialized industrial equipment at high pressure and mixed either i) directly prior to surface coating, or, ii) in a mold cavity to obtain coatings, membranes or various different shapes. Elastomeric systems based on polyurea chemistry have been formulated to produce high performance, rapid curing coatings and caulks.…”

“…[29,[33][34] In this paper, the synthesis of a new kind of polyurea elastomer by sol-gel chemistry is presented, where the reactivity of the amino-terminated polymers is reduced by the capping of the amines by reaction with ketones. This process allows control of the gelation time from seconds to minutes or hours.…”

Power‐aware provisioning of virtual machines for real‐time Cloud services

“…Because of this fast reaction, polyureas can be used in sprayable systems for coatings 26. The spray technology was not developed until the 1990s,27, 28 following the reaction injection molding technique 29–31…”