Effects On The Ozonolysis Of Butadiene Rubber And Simple Vulcanized Butadiene Rubber In The Presence Of Ethanol

In this dissertation, the ozonolysis of 1,4-cis-polybutadiene (Butadiene Rubber, BR) and simple vulcanized butadiene rubber (SVBR) were studied. The study involved into three processes.1. The ozonolysis of BR was investigated in two different kinds of CHCl3 solution, one was without ethanol, and the other was with ethanol in different concentrations. The comparison involved two aspects, one was the degree and reaction rate of ozonolysis of BR by means of Gel Permeation Chromatography (GPC), the other was the types and relative contents of functional groups of ozonolysis products which were studied by means of Fourier Transform Infrared Spectroscopy (FTIR) and 'H-NMR.In the absence of ethanol, ozonolysis processed only when the concentration of ozone was high. The ozonolysis of BR was uneven and gave products with a bimodal distribution of molecular weight in the GPC. The number average molecular weight (Mn) of products with larger Mn decreased first and then increased, while the Mn of products with smaller Mn reduced to a constant value. In the case of BR reacted with ozone for long time, side reactions took place to give some insoluble white floc gel.And in the presence of ethanol, reduction of molecular weight occurred most noticeably in the first minute of ozonolysis to give products with a bimodal distribution of molecular weight and then more gradually. After 30min of ozonolysis, the Mn falled to less than 800 and the molecular weight distribution became close to unimodal again. There were no floc gel emerged during the process of ozonolysis. The efficiency of ozonolysis dropped with the increase of ethanol concentration, the ozonolysis efficiency was higher than that of no ethanol. However, when the concentration of ethanol was high, the ozonolysis efficiency was lower than that of no ethanol at the early age of ozonolysis but higher than that of no ethanol at the later stage of ozonolysis.Examining the products of ozonolysis at various times by FTIR spectroscopy and 1H-NMR, it turned out the products of ozonolysis with ethanol and without ethanol was nearly the same. And the functional groups contained carbonyls (aldehydes and/or carboxyls), ozonide, hydroxyl and/or hydroperoxide.2. The ozonolysis of SVBR with and without of ethanol were compared. In the absence of ethanol, SVBR could not be fully ozonolysed, white floc gel appeared and increased with the reaction went on. In the presence of ethanol, SVBR could be totally ozonolysed. GPC curves showed that the ozonolysis was a very fast reaction; the peak molecular weight of soluble products was around 560 and stayed unchanged during the whole ozonolysis process. Using FTIR to study the functional groups of soluble products, it turned out that the main groups of ozonolysed SVBR with and without ethanol were nearly the same, which were hydroxyls, carbonyls (aldehydes and carboxyls) and ozonides.3. The reduction of ozonolysed SVBR with sodium borohydride (NaBH4) was investigated. The curves of reduced products in the GPC spectrum coincided with that of tetrahydrofuran, this showed that the main products of ozonolysed SVBR were small molecules. Using the FTIR and 1H-NMR to characterize the change of functional groups after reduction, it turned out that the peaks of carbonyls (aldehydes and carboxyls) and ozonides in FTIR and'H-NMR spectra disappeared, while the peaks of hydroxyls increased significantly. It could be explained that all the ozonides were reduced to hydroxyls and the products of reduced ozonolysed BR were 1,4-butanediol with little aldehydes.