Study on Anti-tracking Properties of Unsaturated Polyester Resin SMC
A method of thickening hydroxyl-terminated unsaturated polyester with polyurethane (PU) that comes from the reaction between diisocyanate compounds and polyglycol is introduced, and the effect of PU prepolymer on the anti-arc properties of the sheet molding compounds (SMC) is studied according to the standard of ASTM, the electric strength is tested in the transformer oil under 423K, 453K, 473K, 523K respectively. The anti-tracking properties of UP-SMC were developed when Al(OH)3  and diisocyanate compounds were filled in UP-SMC. The microstructure of UP-SMC struck by electric arc was observed by means of SEM (Scanning Electron Microscopy). The results show that UP-SMC samples with no anti-tracking modification have some part of ablation and charring while the modified sample are with the low electric rot. The arc breakdown time would increase with the usage of PU. The SMC thickened by PU shows good aging resistance as well as anti-arc properties, it will be widely used on electrical parts and arc-deflecting cover of AC switch etc
Thickening behaviour and shrinkage control of low profile unsaturated polyester resins
The rheological and morphological changes of a low shrink unsaturated polyester resin during thickening and curing were investigated. The behaviour of low profile additive (LPA) could be modified by adding a thermo-breakable functional group to its molecule. The thickening reaction of the modified LPA with MDI was much faster than that of LPA with MgO, and the viscosity was stable for 3 months. Because of the thermo-decomposition of the thermo-breakable functional group, the thickened mixture of LPA-M with MDI lost its viscosity greatly at elevated temperatures. The unthickened LPA and thickened LPA-M/MDI samples showed clear phase separation, large internal surface areas and good shrinkage control. The thickened LPA/MDI samples showed little phase separation, very small internal surface area, and poor shrinkage control. The thickened LPA/MgO samples showed some phase separation and good shrinkage control at high moulding temperature. At low moulding temperatures, both phase separation and shrinkage control were poor.
An anionic shell shields a cationic core allowing for uptake and release of polyelectrolytes within core-shell responsive microgels.
To realize carriers for drug delivery, cationic containers are required for anionic guests. Nevertheless, the toxicity of cationic carriers limits their practical use. In this study, we investigate a model system of polyampholyte N-isopropylacrylamide (NIPAM)-based microgels with a cationic core and an anionic shell to study whether the presence of a negative shell allows the cationic core to be shielded while still enabling the uptake and release of the anionic guest polyelectrolytes. These microgels are loaded with polystyrene sulfonate of different molecular weights to investigate the influence of their chain length on the uptake and release process. By means of small-angle neutron scattering, we evaluate the spatial distribution of polystyrene sulfonate within the microgels. The guest molecules are located in different parts of the core-shell microgels depending on their size. By combining these scattering results with UV-vis spectroscopy, electrophoretic mobility and potentiometric titrations we gain complementary results to investigate the uptake and release process of polyelectrolytes in polyampholyte core-shell microgels. Moreover, Brownian molecular dynamic simulations are performed to compare the experimental and theoretical results of this model. Our findings demonstrate that the presence of a shell still enables efficient uptake of guest molecules into the cationic core. These anionic guest molecules can be released through an anionic shell. Furthermore, the presence of a shell enhances the stability of the microgel-polyelectrolyte complexes with respect to the cationic precursor microgel alone.