Mohammad Reza Rohani - Department of Chemical Engineering, Payam Noor University, Tehran, Iran

During curing unsaturated polyester (UP) resin, a high polymerization shrinkage (about ۷-۱۰%) is created by free radical copolymerization of unsaturated polyester resin and styrene monomer. The volume shrinkage causes warping, wavy surfaces, internal voids and cracks. Anti-shrinkage is essential to the UP resin and the composite materials of UPR matrix. Thermoplastic materials as low profile additives (LPAs) have been found very effective in controlling volume shrinkage of cured UP resins. The morphology changing during cure and phase separation, thermal expansion and micro void formation, plays major role of LPAs which provide ability to eliminate shrinkage but affect in many mechanical properties because of increasing volume fraction of microvoid and decreasing the final degree of cure which can lead to weak mechanical properties.By adding LPA in UP resin, the resin is called low profile unsaturated polyester. This study tries to explain the effect of morphology changes during cure on mechanical properties for cured low profile unsaturated polyester resin

Unsaturated polyester resin, Low profile additives (LPAs), shrinkage, morphology, mechanical properties