Study On The Structure And Properties Of Casein Modified Polyacrylonitrile Fibers

The fiber forming polymer of milk protein fibers is firstly made from the graft polymerization,or blends of casein and PAN(polyacrylonitrile)and then the fibers are formed by wet-spinning. The milk protein fiber has attracted much attentions since coming out. The composition and structure,mechanical properties,dyeing properties, heat resistance,acid resistance and alkaline resistance of the milk protein fiber were studied in details in this thesis.At the same time,the performance of the blended knitted fabric was also analysised.First of all,the result of the amino acid analysis indicated that the milk protein fiber contains 17 kinds of amino acids,which accounted for 24.86%of the whole quality of the fiber.Among the amino acids the neutral amino acids occupies 40.90%,the alkaline and acidic amino acids occupies 28.34%and 26.80%respectively,besides all those above,the amino acids in the milk protein fiber include 1.82%of cystine and 2.14% of methionine.The results of the Infrared spectra showed that the milk protein fiber is made up of casein and acrylonitrile.The X-ray diffraction analysis showed that the milk protein fiber is a semicrystalline fiber and there are both the crystalline and amorphous region in its structure of aggregating state.The crystallinity and the crystallinity orientation is 45.22%and 72.10%respectively.From SEM it can be seen that the cross-sectional shape of the milk protein fiber is pretty much the circular, and there were lots of small microporous and irregular grooves in its surface.Secondly,the breaking tenacity of the ZCA is 4.0cN/dtex which is 1.4 times of the HCA,1.3 times of the cotton and twice of the wool. While the elongation at break of the ZCA is about 25%,which is 20% lower than that of the HCA.Both the breaking tenacity of the two fibers decreased in wet condition,especially the HCA,the loss of the breaking tenacity is up to 42.90%.The dynamic and static friction coefficient of the ZCA were as high as 0.44 and 0.49 respectively.The mass specific resistance of the milk protein fiber is 10⁹-10¹¹Î©g/cm² which is between natural fibers and most of the synthetic fibers,so the electrostatic is quite serious,and the milk protein fiber has a low crimp ratio and crimp recovery.After treated for 8h in 50℃and 130℃,the breaking tenacity decreased 8.52%and 27.75%respectively.From the TG analysis it could be seen that the thermal stability of the milk protein is weaker than the PAN fiber in the low temperature.The thermal cracking of the fiber began from 220℃and the temperature of the maximum rate of thermal cracking was about 318.5℃.The percentage of the weight loss was about 51.73%at the end of the testing.DSC analysis showed that there were endothermic sidesteps in the scope of 50℃～110℃and 210℃～293℃in the ZCA,but the contrast,there was an exothermic peak for the Shanxi fibers during 210℃～293℃.The acid resistance of the fiber was better than that of the alkali resistance.After treated in Sulfuric solution with the concentration of 6mol/L for 90 min,the breaking tenacity decreased by 29.27%;while deal with Sodium hydroxide solution with the same concentration for the same time the breaking tenacity decreased by 48.78%.Then,the fiber was dyed through one-bath two-step process of pH indication changing method and the dye used was Cibacron red and X-RG yellow activity dye.The result proved that this process could increase the dyeing rate and fixing rate of the fiber color.The dyeing rate and fixing rate could improved by 23%and 33%respectively,Sodium carbonate content should be 10g/L～20g/L,the best time is 50 min,and the temperature should not higher than 90℃.Finally,the performance of the milk protein fibers-cotton blended knitting fabrics was tested and the results showed that the fabric had a good performance of drapability,permeability and warm property, moderate strength,and relatively poor of wear-resistant,anti-pilling performance,washed dimensional stability and wrinkle resistant.