Effect of crosslinking on mechanical and viscoelastic properties of semiinterpenetrating polymer networks composed of poly(vinyl chloride) and isocyanate crosslinked networks

Abstract

Semiinterpenetrating polymer networks (SIPNs) of PVC/isocyanate/polytriol were prepared by premixing small (150 m dia.) porous (30% voids) unplasticized PVC particles, 10% by weight of isocyanate, and a triol at different OH/NCO mol ratios. Three types of isocyanates (methylene bis-phenyl diisocyanate (MDI), oligomeric MDI isocyanates (PAPI), and toluene diisocyanate (TDI) prepolymer/polytriol) were used. Two-roll milling was followed by hot-press curing. The tensile, flexural, and impact strengths increased when small amounts of crosslinked isocyanate networks were created in PVC. The isocyanate/polyol hydroxyl stoichiometry was varied, and the effects of crosslinking on the tensile, impact, and flexural strengths of PVC/isocyanate/ triol SIPNs were examined. The strength increments were greater when the OH/NCO mole ratio went from 0 to 0.25, than when it went from 0.25 to 1.0. In many cases, increasing OH/NCO mol ratio from 0.5 to 1.0 decreased tensile, impact, and flexural strengths. Both PAPI and MDI (30% NCO content) gave bigger improvements in the these mechanical strengths than the TDI (only 9.7% NCO). These SIPN blends exhibited lower tan ␦ peak temperatures and a single distinct loss modulus, EЉ, peak values at lower temperatures than those of PVC that had been exposed to the same processing temperatures. Substantial amounts of isocyanate networks exist in SIPN phases according to DMTA studies. The OH/NCO ratio did not generally correlate with the decreases in the glass transition temperatures in these three sets of blends.

Fabrication and characterization of gelatin‐based biocompatible porous composite scaffold for bone tissue engineering

“…Hence, thermal stability of the composite scaffold was found to be increased after crosslinking. It was also revealed that the highest degradation temperature increased in the sequence of GP, CGP, GPCT, CGPCT which was the same as that of their crystallinity, implying thermal stability of the films was improved by their crystalline domains and hydrogen bonding interactions 34…”

Semi-interpenetrating polymer networks based on polyurethane and poly(2-hydroxyethyl methacrylate): Dielectric study of relaxation behavior

“…The curing rate of monomers is critical as it can prevent and/or limit the phase separation of the system [16]. By controlling the kinetics of both polymerization reaction and microphase separation, it is possible to prepare IPNs with dispersed phase domains ranging from a few tens of nanometers to a few micrometers [17][18][19][20].…”

Blend Films of Waterborne Polyurethane-Carboxymethylated Guar Gum Crosslinked by Ca2+

“…The weight loss at 400-600 ºC was believed to be caused by oxidation and degradation 39 . The pure WPU film exhibited one weight loss step in the course of thermal degradation and the initial thermal decomposition occurred on 357 ºC and then, decomposed to give greatest weight loss in 380 ºC, which may be caused mainly by the breaking of urethane bonds 40 . The thermo-gravimetric trace of CMGG revealed that decomposition of CMGG was a single step degradation process, which decomposition started at 247 ºC and proceeded at a faster rate up to 290 ºC.…”