耐热环氧聚氨酯复合涂层的制备与表征

Preparation and characterization of thermal-resistant epoxy-polyurethane composite coatings

通过苯甲酸改性酚醛环氧树脂得到了含羟基的酚醛环氧树脂,再经固化剂甲苯二异氰酸酯三聚体和邻苯二甲酸酐固化后,得到了耐热的环氧聚氨酯复合涂层。通过改变苯甲酸改性酚醛环氧树脂的开环率,研究了在聚氨酯体系中引入酚醛环氧树脂的量对其耐热性能的影响。以傅里叶变换红外光谱研究了苯甲酸改性酚醛环氧树脂及其固化过程,以热重分析研究了酚醛环氧改性聚氨酯(MPU)的热稳定性,测试了涂层性能。结果表明,酚醛环氧的引入显著提高了聚氨酯的耐热性,各开环率的酚醛环氧改性聚氨酯涂层的起始分解温度不低于350°C(比传统丙烯酸聚氨酯高约30°C),转折温度高于380°C,终止温度高于430°C,涂层硬度达3H以上,都有较好的耐水、耐酸和耐碱性能。涂层的柔韧性、耐冲击性、硬度、附着力等随开环率的不同而变化。因此,可以通过调整开环率来达到预期的涂层性能指标。但当开环率大于40%时,涂膜附着力变差。

A hydroxy-containing novolac epoxy resin was obtained from bisphenol A epoxy resin after modification by benzoic acid, and then cured with toluene diisocyanate trimer and phthalic anhydride as curing agents to form a thermal resistant epoxy-polyurethane composite coating. The effect of the amount of novolac epoxy resin introduced to polyurethane system on the thermal resistance of coating was studied by changing the ring-opening rate of benzoic acid- modified novolac epoxy resin. The benzoic acid-modified novolac epoxy resin and its curing reaction were studied by Fourier-transform infrared spectroscopy. The thermal stability of the novolac epoxy-modified polyurethane （MPU） was studied by thermogravimetric analysis, and the coating performances were tested. The results showed that the thermal resistance of polyurethane is significantly improved by introducing the novolac epoxy resin. The novolac epoxymodified polyurethane coatings （MPUs） with various ringopening rates have an initial decomposition temperature over 350℃ （higher than that of the traditional acrylic polyurethane by 30℃）, a transition temperature over 380℃, and an final decomposition temperature over 430℃. The hardness of the coatings with good resistance to water, acid and alkali is up to 3H. The prospective coating performance indexes can be achieved by adjusting the ring-opening rate, because the flexibility, impact resistance, hardness and adhesion of the coating changes with the difference of ringopening rate. The adhesion of the coating becomes poor when the ring-opening rate is above 40%.