聚乙烯醇(PVA)在热处理作用下会逐渐发生侧基脱除、断链、环化等复杂的副反应.通过阶段性热处理方法,可望在减少副反应的同时在分子主链上生成双键,从而得到类似聚乙炔的共轭聚合物.文中以PVA1799为原料,通过阶段性加热法,利用在线红外技术,研究了PVA在氮气气氛下不同温度热处理后的结构变化.热处理温度范围为30~330℃,在150℃,180℃,210℃,240℃,270℃,300℃和330℃每个温度点停留30 min.研究发现,PVA的熔点为210℃,在240℃开始发生结构变化,并在分子主链生成双键和羰基.当温度超过300℃,有少量二氧化碳(CO2)放出,开始出现更为复杂的副反应.
The elimination of side groups,chain scission,cyclization and other complicated reactions can occur gradually in poly (vinyl alcohol) (PVA) when heated.Through stage heat treatment,it' s hopeful to reduce side reactions and produce double bonds in PVA macromolecule,which is a proper method for preparing the conjugated polymers such as polyacetylene.In this paper,the structure changes of PVA1799 under stage heat treatment were studied by on-line FT-IR technology.The temperature range was from 30 ℃ to 330 ℃ and the sample were held for 30 min at 150 ℃,180 ℃,210 ℃,240 ℃,270 ℃,300 ℃ and 330 ℃.It is found that the melting point of PVA is 210 ℃.The initial structure change of PVA takes place at 240 ℃ resulting in the accumulation of carbonyl groups and double bonds in PVA molecules.When the temperature is more than 300 ℃,it is observed that a small amount of carbon dioxide is produced meaning more complicated side reactions begin to appear.
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