The electric powertrain system installed in electric vehicles uses a battery, an inverter, and a motor. The inverter converts the DC current into three-phase AC current, which is then supplied to the motor for driving power. The miniaturization, higher output, and higher performance of these components will improve the electricity cost of EV. To achieve this, it is important to improve the heat resistance and insulation performance of the functional polymers used in these products. This paper outlines the high-performance polymers that contribute to the high performance of electric powertrain systems.

Multifunctional thiol compounds are used in a various application due to their unique properties. But on the other hand, it is sometimes difficult to control their high reactivity, and which makes their applications limited. Multifunctional secondary thiol compounds introduced in this paper have been reported to be able to increase the pot life of compositions because their reactivity is controlled by the steric hindrance of the methyl groups next to the mercapto groups, and to give cured products with excellent water resistance due to their low water absorption rate. Details of these compounds are reported here.

The glass transition temperature (T_g) and coefficient of thermal expansion (CTE) of cured resin obtained by thereaction of cresol novolac type maleimide resin and bisbenzoxazine with allyl groups were measured. Cured resin obtained under curing conditions of 2 h at 220 ℃ showed a T_g above 350 ℃ and a CTE of 49–52 ppm/K. These values were higher thermal resistance and lower thermal expansion compared to a cured resin using benzoxazine without an allyl group.Reaction analysis using monofunctional model compounds suggested that the cycloaddition products were obtained by the reaction of a benzoxazine degradate with maleimide. The peroxide-catalyzed reaction consumed more allyl groups than the imidazole-catalyzed one, which suggests the peroxide-catalyzed resin has higher cross-linking density.

Thermal properties of 12-different hardwood (Betula maximowicziana) lignophenols (LPs) with 4-alkylphenols, dimethylphenols or naphthols were estimated and evaluated using thermal mechanical analysis (TMA) and thermogravimetry(TGA). Relationships between these thermal properties and chemical structures of grafting phenols determined by FTIR,¹H-NMR and HPLC (SEC) have been investigated. Both glass transition temperatures and thermal stabilities determined by TMA and TGA respectively were different among LPs with 4-alkylphenols, xylenols and naphthols. As length of alkyl chains increased, T_g of LP decreased from 160 ℃ to 120 ℃. Naphthol also increased T_g of LP up to 185 ℃ due to large and planar structures with rich π-interactions. Since xylenols as well as p-cresol showed only small changes in T_g and T_d5. Some dependences of these properties on only grafting phenols were observed. Relationships between free volumes produced by motions and interactions of long alkyl chains and aromatic rings and thermal properties of LP were discussed.

Citric acid-derived trifunctional 5-membered cyclic carbonate (CA-TC) resins were synthesized by allylation, epoxidation, and carbon dioxide insertion to three carboxy groups of a citric acid. The resins were thermally cured with trioxyethylene diamine (TODA), and cured CA-TC/TODA films were prepared. Thermal properties of the cured material were examined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The glass transition temperature (T_g) and 5% weight loss temperature (T_d5) of the cured CA-TC/TODA were determined to be -23.8℃ and 223℃, respectively. These results indicated that the cured material was rubbery at room temperature and easily decomposable at elevated temperature. By tensile testing of the cured film, we found the tensile modulus, tensile strength, and elongation at break were 0.46 MPa, 0.26 MPa, and 0.68, respectively, which shows that the cured material was soft and flexible. Examination of the enzymatic degradation of the cured materials revealed their high degradability by lipase from porcine pancreas and protease from streptomyces griseus.