摘要： 为解决高钢级钢管对三层结构聚乙烯（3LPE）防腐工艺提出的新要求,粉末涂料企业针对性地开发了一系列涂敷温度低于190℃的低温涂敷型环氧粉末（LAT-FBE）。若干型号的LATFBE涂层存在固化转化率大于99%,但玻璃化转变温度差值（ΔTg）却明显小于-2℃的现象,即"ΔTg负向超差"问题。评价涂层固化度的2个指标发生冲突,严重影响LAT-FBE涂层合格与否的准确判定。在理论分析的基础上,对ΔTg负向超差问题进行了实验研究。结果表明:导致ΔTg负向超差的直接原因是涂层Tg3异常升高,其根本原因是LAT-FBE涂层的分子结构处于不稳定状态,分子链段柔性较低,涂层存在较大的内应力。

关键词: 环氧粉末, 低温涂敷, 玻璃化转变温度, ΔTg负向超差

Abstract: In recent years, a series of low application temperature fusion bonded epoxy D(LAT-FBE)powder which can be applied below 190 ℃ has been developed in order to solve the new challenges of 3-layer PE(3LPE ) anticorrosion for high grade steel pipe. Although the conversion degree of some LAT-FBE coatings can meet the requirements of 99%, the difference in the glass transition temperature between two successive thermal analysis scans(AT) is significantly over -2 ℃. which can be defined as AT negative over value"The two indicators evaluating the curing degree of LAT-FBE coating are contrary, and it seriously influences the quality evaluation of LAT-FBE coating. Experimental research based on theoretically analysis for A/, negative over value is made in this paper. The results show that the direct cause of A7. negative over value is abnormally increase of a. The root cause is the unstabl state of LAT-FBE molecular structure, and the molecular chains lack flexibility. the coating shows great internal stress.

Key words: fusion bonded epoxy powder, low application temperature, glass transition temperature, △Tg negative over value