The Effect of PMMA on Volume Shrinkage of Unsaturated Polyester (UP) Resin

The reaction between unsaturated polyester (UP) resin and styrene (St) (UP//St system)is a free-radical chain-growth cross-linking copolymerization. The free radical copolymerization of unsaturated polyester resin and styrene monomer create a three dimensional network which cause to create about (7-10%) shrinkage. Volume shrinkage causes warping, wavy surfaces, internal voids and cracks. This requires post-mold processing to improve surfacefinish..Adding thermoplastic polymers namely, low profile additives (LPAs) have been found to be highly effective in controlling shrinkage.In this study, the effect of PMMA on Volume Shrinkage of Unsaturated Polyester (UP) Resin was investigated using density measurement method. .It was found that the addition of low profile additives (PMMA) show that the volumetric shrinkage Of the unsaturated polyester UP resins decreases.. The compatibility of PMMA and resin compound is more dependent on molecular weight of low profile additive. The samples with lower molecular weight of PMMA and higher cured temperature cause more effect on shrinkage control in UP/St system

کلیدواژه ها:

Unsaturated polyester resin ، Shrinkage control ، Low profile additives (PMMA)