In the manufacture of pieces with composite materials of reinforced plastics, unsaturated polyester resin (UPR) constitute 39 % of the total of thermosets resins used globally due to the low cost and versatility of use in different applications.<br/>A common UPR is composed of unsaturated polyester (UP) and styrene (ST) as reactive solvent. UPR is a liquid solution that presents one phase, that during curing present UP-ST copolymerization forming a heterogeneous structure. Curing mechanism suggests the generation of microgels rich in UP and with higher crosslinking density than the surrounding phase rich in ST.<br/>It was found that there is a strong relationship between phase distribution of the fully cured UPR and both thermal stability and dynamic mechanical properties, measured by TGA and DMA, respectively. The changes of phase distribution were achieved changing UP-ST miscibility of the liquid resin. Changes in the curing mechanism and kinetics with curing temperature were verified by DSC. Morphologies of the internal surfaces were analyzed by AFM. It was also found that more homogeneous nanostructures with smaller nodules presented higher storage modulus and higher T<sub>g</sub> of each phase of the typical biphasic structure of a thermosetting UPR.

Effects of changes in phase distribution of neat unsaturated polyester resin on both thermal stability and dynamic-mechanical properties

ACS Spring Meeting 2021

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