Comparative Study On The Quality Of Concentrated Natural Rubber Latex Between Native And Imported

Natural rubber latex is a kind of polymer emulsion biosynthesized by Hevea brasiliensis.Due to its excellent properties of wet gel strength,resilience,and film-forming,it is an ideal raw material for the manufacture of gloves,condoms,balloons,urinary catheters and other products.In recent years,compared with imported latex,domestic latex has a large gap in volatile fatty acids,mechanical stability,etc,which makes the latex products prone to uneven molding,bubbles,blasting other issues,affecting the quality of the product and processing technology.Due to the influence of the rubber tree strain,planting climate,field management,processing technology and so on,there are large differences in the quality of concentrated natural rubber latex(CNRL)between native and imported.Therefore,it is of great theoretical and practical significance to deeply discuss the differences in the quality of CNRL.The brand of Baodao and Meilian from Hainan,Guangken-1 from Maoming,Guangken-2 from Yangjiang,Huangchunfa and Sankeshu from Thailand are obtained.And the comparison about the quality of these latex were studied,including the main non-rubber component,rubber particle morphology,molecular chain structure,storage performance,vulcanizate properties and so on.Non-rubber component shows that,compared with imported CNRL,domestic latex has higher content of water soluble substances,while the content of lipids,proteins and acetone solution is lower.The total content of metal ions in domestic latex is relatively high,especially Ca2+,Mg2+ and Zn2+ is respectively 5.37 ?g/g?13.60?g/g?139.97 ?g/g higher than imported latex.Gas Chromatography(GC-MS)analysis that CNRL contains 10 fatty acids,lauric acid,myristic acid,palmitoleic acid,palmitic acid,linoleic acid,oleic acid,stearic acid,cis-11-eicosenoic acid,arachidic acid,maslinic acid,and those with highest content is linoleic acid.The contents of unsaturated and saturated fatty acids of imported latex are higher than native latex.The particle size and morphology of the latex particles are analyzed using Malvern laser particle size analyzer and scanning electron microscope.Particle size distribution indicates that the average particle size of imported latex is slightly larger and it's particle size distribution is narrow.In addition,the stability of imported latex is better,maintain a relatively intact particle morphology and smooth surface integrity,the particle size is relatively uniform.The domestic latex especially the Guangken brand,the phenomenon of aggregation of latex particles is more serious.Compared with domestic latex,the imported latex has a higher gel content and crosslink density.The number-average molecular weight(Mn),weight-average molecular weight(Mw),and z-average molecular weight(Mz)of the imported latex are 1.07×105,1.12 × 105,and 1.14 × 105 higher than of the domestic latex respectively.And the molecular weight distribution is narrower.The average molecular weight of latex produced from Hainan is larger than that from Guangdong,and the molecular weight distribution is narrower.Compared with native CNRL,imported latex preserves better.When the imported latex was stored for 180 days,the volatile fatty acid was kept at 0.04,the viscosity was 23.4 mPa.s,the mechanical stability was maintained at 1033s,and the latex storage stability was excellent.Latex from Hainan has a better preservation effect than from Guangdong.The higher the free calcium,magnesium and volatile fatty acid values in the latex,the lower the mechanical stability of the latex,and the latex stability was worse.Studing on the effect of lauric acid soap amount on the storage effect of latex,the results show that storage effect of the concentrated latex was best with 0.055%lauric acid,the content of free calcium and magnesium decreased by 33.1%,the viscosity decreased by 33.6%,the mechanical stability of the latex was most significantly improved.And the thermal stability was 84s,although there was a decrease,but did not drop much.The mechanical properties analysis of the latex vulcanized film showed that the tensile strength of the imported vulcanized film was 2.54 MPa and 2.95 MPa higher than that of the domestic vulcanized film before and after aging.In summary,the tensile mechanical properties of these vulcanizates are as followed:Huangchunfa>Sankeshu>Baodao brand>Meilian brand>Guangken-1>Guangken-2.Compared with domestic vulcanizates,the crosslink density of imported vulcanizates is higher.Vulcanizates of imported have better heat resistance.