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
Study on thickening behavior and dielectric properties of unsaturated polyester 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 thickening mechanism and blending miscibility between unsaturated polyester resin (UPR) and PU are discussed. 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 423 K, 453 K, 473 K, 523 K respectively. The results show that the thickening mechanism is an amino group is formed during the reaction. The compatibility of UPR and PU varies with the amount of PU, mechanical properties of UPR/PU-SMC are excellent when the PU is 36%. 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 is widely used on electrical parts and arc-deflecting covers of AC switch etc.
Free-radical crosslinking copolymerization of styrene/unsaturated polyester resins: 3. Kinetics-gelation mechanism
Abstract Based on the results of integrated analysis given in parts 1 and 2, a kinetics-gelation mechanism of styrene (ST)/unsaturated polyester (UPE) resins is proposed. The curing process can be divided into five stages: induction, microgel formation, transition with or without phase separation, macrogelation and post-gelation. A summary of the experimental results at different stages of ST/UPE resins with ST/UPE molar ratios of 2 and 4 at 40°C is given. The kinetics-gelation mechanism based on the concept of microstructure formation is then discussed.