Investigation Of Phospholipids On Mechanical Stability Of Natural Rubber Latex

Natural rubber latex (NRL), biosynthesized by Hevea brasiliensis, is a kind ofmacromolecular emulsion and has been widely used in the manufactures of latex products,such as gloves, catheter, balloons, sponge and so on, due to its excellent properties offilm-formation, wet gel strength and biocompatibility. As one of the important industrial rawmaterials, the good colloidal stability and processability for natural rubber latex is essentialfor its applications. In recent years, with the increase of production output, the quality ofnatural rubber latex in China shows a gradual declining trend with an obvious decrease inmechanical stability which exhibits great effects on the processing performance and thequalities of latex products.To confirm the reasons that the mechanical stability of natural rubber latex declined, thechloroform-methanol mixing solvents was adopted to extract lipids from natural rubber latex.The hydrolyzed products of lipids was then analyzed by GC-MS and had compared with thosefrom phospholipids at similar conditions to analyze the change mechanism of mechanicalstability of natural rubber latex. On this basis, the effects of phospholipids on the mechanicalstability of natural rubber latex, the processing performances and physical properties ofvulcanized natural rubber latex films were investigated, respectively.GC-MS analyses showed that25long fatty acids were extracted from natural rubberlatex and those with higher contents were9,12-octadecadienoic acid, octadecenoic acid,octadecanoic acid, hexadecanoic acid,9,12,15-octadecatrienoic acid, palmitoleic acid,eicosanoic acid and cis-11-eicosenoic acid, respectively. Phospholipids were also hydrolyzedat similar conditions and similar acids, such as hexadecanoic acid, octadecanoic acid,trans-octadecenoic acid, octadecenoic acid,9,12-octadecadienoic acid and9,12,15-octadecatrienoic acid were detected. In addition, the total content of unsaturated fattyacids was higher than that of saturated ones as the pH value and hydrolyzing time increased.The results indicated that the long chain fatty acids released from the hydrolysis ofphospholipids amongst lipids in natural rubber latex can improve the mechanical stability of natural rubber latex gradually.Based on the results, the effect of phospholipids on the mechanical stability wasinvestigated. The mechanical stability of natural rubber latex can be increased by addingphospholipids. In addition, the films of vulcanized natural rubber latex exhibited excellentphysical properties. When temperature was below glass transition temperature, the thermaldegradation temperatures and the storage modulus of vulcanized natural rubber latex filmswere increased by adding phospholipids. The evaluations of the processing performancesdemonstrated that the natural rubber latex can be used to manufacture the tubing steadily byadding phospholipids and both the appearance and mechanical properties of tubing can beimproved.