聚L-乳酸/啶虫脒控制释放农药体系的研究

Study on Controlled-release Pesticides of Poly(L-lactic acid)/Acetamiprid

以三氯甲烷为溶剂,制备聚乳酸(PLLA)和啶虫脒混合溶液,脱除溶剂后制备成PLLA/啶虫脒缓释农药。采用红外光谱法、差示扫描量热法和偏光显微镜法等方法对其进行表征研究。试验结果表明,在PLLA/啶虫脒共混物中,啶虫脒与PLLA具有较强的相互作用和较好的相容性。PLLA/啶虫脒共混物的组成对PLLA结晶与啶虫脒结晶均有影响。PLLA结晶成核速度随着啶虫脒含量的增加而降低,且结晶缺陷增多,结晶熔融温度逐步降低。当共混物中的啶虫脒质量分数低于10%时,啶虫脒不能形成结晶,而当啶虫脒用量大于20%时,啶虫脒可形成结晶,且结晶熔融温度随着其用量的增加而升高。在啶虫脒质量分数为20%,PLLA/啶虫脒共混物的DSC曲线在90℃附近出现新熔融峰,该峰随着啶虫脒的增加而增强,且温度下降。啶虫脒和PLLA的DSC曲线上均不存在该峰,这可能是PLLA与啶虫脒的相互作用所形成的新次级结构而引起。

Poly(L-lactic acid)(PLLA) and acetamiprid were respectively dissolved in chloroform to prepare mixture solution.Then blend film of PLLA/acetamiprid was prepared by solvent evaporation method from mixture solutions.Fourier transform infrared spectrometry,differential scanning calorimetry and polarized optical microscopy were utilized to detect these blends.All results show that there is strong interaction between acetamiprid and PLLA,the two components have good compatibility.With increasing acetamiprid contents,crystallization nucleation rates of PLLA decrease,while the imperfections of PLLA crystal increase too,the melting temperature of PLLA decreases.While the content of acetamiprid in PLLA/acetamiprid less than 10%,there is no acetamiprid crystallixation;while the content more than 20%,acetamiprid crystallization can form,and the crystallization melting temprature increases with increaing acetamiprid content.Moreover there is a new melting peak on DSC curves of PLLA/acetamiprid blends when acetamiprid content is 20%.There is no peak on DSC curves of PLLA and acetamiprid,the peak strengthens with the increasing of acetamiprid content,and melting temprature decreases.which may be caused by PLLA secondary structure due to the interaction between PLLA and acetamiprid.