LPA Performance in Low Temperature SMC/BMC Molding

摘要

Unsaturated polyester (UP) resins with low profile additives (LPA) used in sheet molding compounds (SMC) and bulk molding compounds (BMC) are thickened for easy to handle and good fiber carrying characteristics. There are two basic thickening methods: alkaline earth oxides (e.g. MgO) to form ionic bonds or diisocyanate compounds to form covalent urethane linkages with UP and LPA molecules. Both of them have disadvantages - MgO has difficulty in thickening control that the compound viscosity keeps on increasing after maturation, while diisocyanate compounds form the covalent bonds which cannot break during molding and in turn reduce the shrinkage control ability of LPA. It would be desirable to develop new methods or materials without these disadvantages.