Effect Of Protein Content On The Properties Of Natural Bubber Latex

Natural rubber latex contains not only rubber hydrocarbons and water,but also small amounts of non-rubber components such as protein,lipid,inorganic salt and acetone.Natural rubber latex has excellent comprehensive properties,such as good film forming properties,resilience and mechanical properties.The presence of protein in the latex tends to deterioration of the hygroscopicity,electrical conductivity of the latex product,and some protein bind to immunoglobulin IgE in the serum of a small number of people to induce human allergy.Through the analysis of the effect of protein content on the performance of natural rubber,it has important theoretical and practical significance for the protein content of the best performance of the selected product.In this paper,deproteinized treatment was used to obtain latex with different protein content,and the effect of protein content on the mechanical properties and stability of natural rubber and vulcanized rubber film was analyzed.The deproteinized natural rubber latex with different protein content was prepared by centrifugation and protease hydrolysis of fresh latex.The protein content decreased from 3.88%to 0.06%.The average particle size of the rubber particles increased from 423 nm to 740 nm,the peak particle size gradually increased,and the integrity of the protective layer protein-phospholipid membrane on the surface of the rubber particles was destroyed.Centrifugation and proteolytic hydrolysis effectively reduce the protein distribution on the surface of natural rubber.With the decrease of protein content,The average weight molecular weight of natural rubber decreased by 1.82×105,the molecular weight distribution became wider,the gel content and crosslink density showed a decreasing trend.Latex Zeta potential analysis showed that the absolute value of the zeta potential of the deproteinized natural latex was higher than the absolute value of the zeta potential of the natural latex,and the stability was enhanced by the addition of the stabilizer sodium dodecyl sulfate aqueous solution.When the protein content of natural rubber decreased from 3.88%to 0.06%,the plastic retention index PRI decreased from 77%to 42%,the aging resistance was poor,and the deproteinized rubber was prone to degradation.The loss factor tan8 of natural rubber is higher than the tan? of deproteinized natural rubber.The decrease of protein content leads to the decrease of cross-linking bonds,The cross-linking structure of the rubber segment is destroyed,the mobility of the segments is improved,and the elastic recovery effect of rubber products is gradually reduced.The glass transition temperature was lowered from-61.11? to-61.64 ?.When the protein content decreased from 3.88%to 0.06%,the initial degradation temperature T0 decreased from 351.76? to 346.06?,and the maximum rate degradation temperature Tp decreased from 379.68? to 376.85?,When the protein content is 0.25%,the natural rubber has a glass transition temperature of-62.57?,To of 347.38?,Tp of 377.42?,and has good thermal stability.As the protein content of the vulcanized film decreases,the crosslink density decreases,the mechanical properties of the vulcanized rubber film decrease,and the aging resistance decreases.When the protein content decreased from 3.88%to 0.06%,the tensile strength of the vulcanized film decreased from 27.11 MPa to 17.41 MPa,and the tear strength decreased from 74.86 KN/m to 56.41 KN/m.After aging,the tensile strength decreased from 9.88 MPa to 1.86 MPa,the tear strength decreased from 16.82 KN/m to 11.62 KN/m,T0 decreased from 350.26? to 349.36?,Tp decreased from 376.06? to 374.54?,and the thermal stability decreased.The vulcanized rubber film has a good overall performance when the protein content is 0.25%.