Multiscale investigation on molecular structure and mechanical properties of thermal‐treated rigid polyurethane foam under high temperature

Abstract

In order to study the relationship between the molecular structure and mechanical properties of rigid polyurethane foam (RPUF) during the mechanical and chemical failure process, the variation of the molecular structure and mechanical properties of RPUF treated in temperature range of 323–473 K were characterized by both theoretical and experimental methods. The molecular structure stability of RPUF varied with thermal treatment temperature was characterized by density functional theory method. The mechanical properties of base material of RPUF were simulated by means of molecular dynamics (MD) simulation. Then the related parameters obtained from the MD simulation were assigned into a representative volume element model of RPUF for the finite element analysis. The results indicated that the vibrational frequencies of isocyanate groups and amino acid ester groups in RPUF molecule increased while the molecular orbital energy gap of RPUF decreased with the increase of treatment temperature. It indicated that the RPUF molecule had high chemical reactivity at high temperature. The results of the multiscale simulation of mechanical properties showed that the defects and voids in RPUF generated under high temperature would grow with the increase of thermal treatment temperature, which intensified the stress concentration in RPUF and decreased the tensile properties of RPUF.

A Review of Research on the Effect of Temperature on the Properties of Polyurethane Foams

“…The chemical reactivity of the reactive groups (isocyanate and carbonyl) in the RPUF substrate molecules was further excited as the heat treatment temperature of the polyurethane foam material increased. This led to macromolecular decomposition, which further makes the weak regions in the foam structure more vulnerable when subjected to external loads, causing more stress concentrations and eventually leading to the mechanical failure of the RPUF [ 100 ]. The process is shown in Figure 6 b.…”

Investigation of the relation between free volume and physico-mechanical performance in rigid polyurethane foam containing turkey feather fibers: Part 2

“…Thus, since such defects affect the chain mobility of the polymers, the external load endurance capacity of the polymeric materials reduces. 36 The decrements in the mechanical performance of polymeric materials due to the random structural defects influencing negatively the chain arrangements were recorded in the our previous studies. 37,38 Depending on that, it can be stated here that, there is a critical free volume limit in order to obtain the improved polymers.…”

Autoclavable, Breathable, and Waterproof Membranes Tailored by Ternary Nanofibers for Reusable Medical Protective Applications

“…As shown in Figure 2h, the tensile stress and elongation results confirmed that the mechanical properties of PU/PES 6/4 and 2/8 improved after sterilization, which was attributed to the molecular migration of PU at high temperatures, thereby leading to the interlink and building stable polymer networks. 36,37 Moreover, Figure 2i displays photographic images of PU/PES membranes before and after sterilization. It should be pointed out that when the PU component was becoming richer, the stability of PU/PES membranes deteriorated the opposite, and the structure of pure PU membranes was all destroyed.…”