Thermoplastic Urethane Chemical Crosslinking Effects

Abstract

SYNOPSISThis paper reviews the chemical structures and attendant polymer morphology that have been advanced to explain the virtual crosslink (VC) phenomenon in segmented polyurethane elastomers. The different chemical methods employed to produce useful vulcanizates from the classical polyurethane elastomer use-forms (castable liquid, millable gum) through covalent crosslinks (CC) are discussed. And finally, the nature of the polymer property changes occurring when a CC network is superposed on the VC network of a representative thermoplastic poly(ester-urethane) elastomer composition through the use of a free radical curing agent (organic peroxide) is described. The CC-VC network polymer of the subject polyurethane composition proved to have greater resistance to: solvation and its effects, stress relaxation, heat distortion, and compression set, and showed much higher modulus values than the VC network polymer. But the CC-VC network polyurethane also showed less extensibility, tear strength, low temperature flexibility, and flex life. The degrees of these changes are discussed and molecular explanations proposed in some cases.

Poly(hydroxyether of bisphenol A)-block-polydimethylsiloxane alternating block copolymer and its nanostructured blends with epoxy resin

“…During the past year, this approach has been well established in the synthesis of main-chain liquid crystalline polyesters [55,56], electroluminescent polymers [57] and classic polyurethane-based thermoplastic elastomeric materials [58]. The key to apply this approach to synthesize polymers is to utilize an appropriate polymer reaction and to prepare suitable macromers with defined length.…”

A comparative study of the structure–property behavior of highly branched segmented poly(urethane urea) copolymers and their linear analogs

“…Schollenberger and Dinbergs [21] note that the mechanical properties of linear segmented polyurethanes reach a plateau value around hM w i between 100,000 and 200,000 g/mol. The differences in E 0 and tan d responses between the PPO based linear PUU and its highly branched analog also arise due to similar reasons as discussed above.…”

Rigid−Flexible Alternating Block Copolymers That Contain Poly(p-phenylene) Units of Defined Length as the Rigid Blocks

“…[11][12][13][14] This alternating rigidflexible block copolymer strategy is well-established in the synthesis of main-chain liquid crystalline polyesters 15 and poly(urethane)-based thermoplastic elastomeric materials. 16 In this communication, we present the synthesis, characterization, and initial materials properties investigations on soluble rigid-flexible block copolymers composed of conjugated poly(p-phenylene) segments 17 as the rigid blocks.…”