Determination Of Contents Of Micro Antioxidants In Polyolefin And Performance Characteristic

Polyolefin is an important kind of macromolecule material with well performance. However, it was inevitable to suffer from heat, light, oxygen, heavy metal ion or mechanical cut during the courses of synthesis, processing and application, then degradation, discoloration, loss of mechanical properties and even loss of the value were happened. Fundamentally, there are several different approaches to reduce the speed or to prevent the oxidation reaction; the addition of antioxidants is the most convenient and effective way to retard oxidation in polyolefin.It is very important to analyse the prescription of new polyolefin products at home and abroad, as well as to study the contents of antioxidants. But there isn't a common analysis method at present, especially, no exact method for the analysis of small amount of additive.In this thesis, three certain matrixes LLDPEn HDPE and PP in Yangzi petrochemical company were studied. On the basis of all kinds of methods at home and abroad, contents of antioxidants in polyolefin were measured by means of fourier transform infrared spectrometry, the method proposed was accurate, simple and quick. During the course of preparation of sample and suitable solvent commixing methods were selected to mix additives with polyolefin powder. By comparing FTIR spectrograms of additives and matrixes, characteristic peaks of antioxidants were confirmed respectively and some standard curves were plotted. Results showed that the linear relationships between the area of peak and the content of antioxidant were excellent. A virtual means for controlling product quality was provided.It is valuable to investigate the antioxygenic property by measurement of thermal analysis, yellow index (YI), melt flow rate (MFR) and mechanical properties of the multi-extruded LLDPE. During the test of thermal analysis, the oxidative induction time tests were performed on LLDPE samples using a differential scanning calorimeter. From the plot, the appropriate rate was comfirmed between antioxidant Aand B. During the tests of mechanical properties, it was found that the antioxidants had little effect on the yield strength; while there had some effects on the tensile strength, break strength and elongation at break. By measuring the melt flow rate of all the extruded samples after 1st, 3rd and 5th extrusions. Results showed that with the extrusion times increased, a decrease in the MFR was observed. By comparing the five different samples, the 13# was the best one in keeping the processing stability of LLDPE. During the test of YI, with the extrusion times increased, the YI of LLDPE increased apparently, and the 13# sample was the best one in keeping the color stability of LLDPE.