Rubber‐modified epoxies. I. Transitions and morphology

Abstract

SynopsisA variety of different morphologies, and therefore mechanical properties, can be obtained from a single rubber-modified epoxy formulation. The volume fraction, domain size, and the number of particles of phase-separated rubber are determined by the competing effects of incompatibility, rate of nucleation and domain growth, and the quenching of morphological development by gelation. These factors can be varied by the butadiene/acrylonitrile ratio of the reactive rubber, the temperature of cure, and the gelation time. These ideas have been exploited to control the development of morphology of these amorphous systems. Phase separation was investigated by electron microscopy, viscometry, and dynamic mechanical analysis.

Rubber-modified epoxy resins cured with piperidine

“…During cure, phase separation of the rubber occurs as a result of the increase in molecular weight, which reduces the compatibility of the rubber with the epoxy system. Thus, a microstructure of rubbery particles in a matrix of cured epoxy is obtained [4,5].…”

“…There have been many studies on epoxy resins using amines as curing agents [1][2][3][4][5][6][7][8]. The diglycidyl ether of bisphenol-A (DGEBA) cured with piperidine (PP) and modified with CTBN has been used as a model for studying microstructure and fracture be haviour [4,9,JO].…”

“…The diglycidyl ether of bisphenol-A (DGEBA) cured with piperidine (PP) and modified with CTBN has been used as a model for studying microstructure and fracture be haviour [4,9,JO]. This system has two peculiar fea tures: piperidine causes an athermal cure of the epoxy resin and the cure time with this amine is relatively long (several tens of hours).…”

“…This system has two peculiar fea tures: piperidine causes an athermal cure of the epoxy resin and the cure time with this amine is relatively long (several tens of hours). Even though several conditions for cure have been tried, using different temperatures and times of curing at constant PP content [4,10], the temperature and cure times were selected in such a way that they do not allow a systematic discussion of the effects of both variables on the curing of the epoxy. In effect, the low tempera ture cures provided the highest T 8 for the samples.…”

Elastomer-Modified Epoxy Resins in Coatings Applications

“…Such topics as morphology in the cured and uncured state, transitions from toughening to flexibilization, viscoelastic effects, equilibrium physical properties and phase struc ture are available to the investigator (12)(13)(14)(15)(16)(17) …”