不同类型紫胶的红外光谱鉴别

Identification of Different Lac with Infrared Spectrum

利用傅里叶红外光谱分别对紫胶原胶、漂白紫胶、掺有松香的紫胶、接枝共聚紫胶进行了鉴别研究。结果表明 :紫胶原胶和掺有松香的紫胶 ,红外光谱较为相似 ,只要根据 35 0 0～ 2 5 0 0cm-1之间吸收峰的位置和峰形、170 0cm-1附近CO振动峰的不同 ,以及 12 0 0～ 14 0 0cm-1之间松香的特征峰、其他振动峰的数目和位置的变化即可将它们区分开来 ;而漂白紫胶和接枝共聚紫胶是经过化学处理的改性紫胶 ,接枝共聚紫胶是在漂白紫胶的基础上 ,采用高锰酸钾为引发剂 ,接枝甲基丙烯酸甲脂制取的接枝共聚物 ,所以它们的区别主要是 :170 0cm-1附近CO振动峰的变化、15 5 8cm-1出现一个尖锐的小峰 ,6 81cm-1出现一个中等强度的峰 ,以及 115 1cm-1分裂为两个小峰。实践证明 ,红外光谱法比传统的鉴别法科学、省时。

Fourier infrared spectrum was used to differentiate raw lac, bleached las and lac mixed with resin. The results indicate Thai the infrared spectra of raw lac and lac mixed with resin are similar, so the authors can differentiate them by the following items: (1) the position and the shape of absorbing peak between 3 500 and 2 500 cm(-1), (2) the difference of the vibration peak at 1700 cm(-1) for C=O, (3) characteristic peak between 1200 and 1400 cm(-1), (4) the number of peaks and the change in the position of peak. But with bleached and graft copolymerization lacs the properties have been changed by chemical processing. Graft copolymerization of lac is made from methyl-acrylic acid-methy fat by using potassium permanganate as stimulant. Their main differences are: the change of vibration peak of 1700 cm(-1) for C=O, a sharp small peak at 1558 cm(-1), a peak with middle strength at 681 cm(-1), and spliting to two small peaks at 1151 cm(-1). The experiment shows that the method of infrared spectrum is more scientific and effective than traditional method.