自然光和紫外光照条件下膜材红外光谱变化

可降解树脂包膜控释肥是目前肥料领域的研究热点之一。研究从可降解包膜材料实际施用环境着手，采用傅里叶衰减全反射红外光谱技术(ATR-FTIR)，表征包膜肥料膜材自然光和紫外光照条件的降解差异，通过对聚乙烯/疏水纳米二氧化钛、聚乙烯/亲水纳米二氧化钛和纯聚乙烯包膜的谱图来研究膜材在光照前后的结构变化特征，进而对膜材的降解行为做出判断。结果表明，在紫外光和自然光分别照射下，包膜降解过程中的官能团种类没有因光催化剂的加入而受到影响，而光催化剂的加入对官能团的变化程度有显著影响，依次为：聚乙烯/疏水纳米二氧化钛复合包膜>聚乙烯/亲水纳米二氧化钛复合包膜>纯聚乙烯包膜。另外，不同照射光源对包膜的分子结构的影响有所区别。自然光条件照射的降解过程中，包膜的聚乙烯碳链上在形成氢过氧化物的同时发生了交联反应生成含醚键的物质，接着继续氧化生成含羰基的化合物，最终羰基的存在促进包膜的进一步分解;紫外光条件照射下，光照产生的活性氧物种局部浓度大，攻击聚合物碳链的能力强，聚乙烯长链烷基断裂很快氧化生成含有羰基基团的中间产物。紫外光条件的照射实验未能全面反映包膜在自然光条件下的降解行为。

Infrared Spectrum Studies of Coatings under Irradiation of Sunlight and Ultraviolet

Degradable resin-coated controlled release fertilizer is one of the hottest current research focuses in the field of fertiliz-er.In terms of practical application,the photodegradability characteristics of three kinds of coatings including polyethylene/hy-drophilic nano-TiO2 composite,polyethylene/hydrophilic nano-TiO2 composite and pure polyethylene were analyzed under irradi-ation of sunlight and ultraviolet by ATR-FTIR,which was aimed to know their degradation behaviors under two conditions.The result showed that under irradiation of sunlight and ultraviolet,the type of functional group was not changed with the addition of the photo-catalyst,but the photo-catalyst j ust had an effect on intensity of functional groups.The trend was polyethylene/hy-drophobic nano-TiO2 composite>polyethylene/hydrophilic nano-TiO2 composite>pure polyethylene.Furthermore,sunlight and ultraviolet had different effects on molecular structures of coatings.Under irradiation of sunlight,crosslinking reaction took place and ether bond was generated among the carbon chain of polyethylene except for the form of hydroperoxides.Then,carbon chain continued being oxidized to form carbonyl group.The existence of carbonyl group promoted the further degradation of coatings;under irradiation of ultraviolet,high local concentrations of reactive oxygen species were produced and the ability to at-tack the carbon chain of polymer was strong.Thus,the long alkyl chain of polyethylene was quickly oxidized to form intermedi-ate products containing carbonyl groups.However,the irradiation experiment of ultraviolet didn’t fully reveal the degradation behavior of coatings.