Maillard reaction in Natural Rubber (NR) latex was investigated by treating fresh NR latex with glutaraldehyde (C5H8O2) in amounts of 0, 50, 100, and 200 mmol/kg of latex. Protein cross-linking in fresh NR latex and solid NR was confirmed by using sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and attenuated total reflection infrared (ATR-IR) spectroscopy, respectively. It was found that degree of protein cross-linking in NR increased with increasing C5H8O2concentration. Physical properties of untreated and treated NR substances in terms of gel content, initial Wallace plasticity (P0), plasticity retention index (PRI), Mooney viscosity, and tensile strength were carefully explored. Results clearly showed that the Maillard cross-linking of proteins had remarkable effect on bulk NR properties, that is, solvent resistance, hardness, resistance to oxidation, rheological behavior, and resistance to stretching out.

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Maillard reaction in natural rubber (NR) latex was studied by treating fresh latex with formaldehyde and glutaraldehyde. Volatile fatty acid number of the treated latex could be lower than acceptable limit (< 0.08) for more than 20 days. Attenuated total reflectance infrared spectroscopy and sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed the occurrence of protein crosslinks in the treated latex. NR treated with glutaraldehyde has much higher nitrogen content than NR treated with formaldehyde and untreated NR, respectively. Colloidal stability of rubber particles, represented by pH, zeta potential, viscosity, and particle size distribution information, were unchanged after treating the latex with formaldehyde. Treatment of the fresh latex with glutaraldehyde 100 and 200 mmol/kg of latex led to the aggregation of rubber particles. Interestingly, the Maillard crosslinking of proteins in fresh latex could efficiently promote the transfer of rubber particles from the serum phase into the cream phase during centrifugation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45224.

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In this study, the chitosan and its derivatives were tested for their preservative activities for field natural rubber (NR) latex. A series of chitosans with different molecular weights were obtained by nitrous acid depolymerization. The chemically modified chitosans, Ncarboxymethyl chitosan (NCMCh), N-sulfated chitosan (NSCh), and N-(2-hydroxy)propyl-3-trimethylammonium chitosan chloride (NHTACh), were prepared from high and low-molecular weight chitosans. Preservative activities for field NR latex of these chitosans were investigated based on the measurement of volatile fatty acids (VFA) number of the treated latex. The preservative activities of chitosan increased with decreasing molecular weights. The lowmolecular weight NSCh and NHTACh exhibited good preservative activity for the latex. By the use of low-molecular weight NHTACh in combination with octylphenol poly (ethyleneglycolether) (Nonidet P40), the latex was successfully preserved for more than 1 month in the low-ammonia condition. The results showed an attractive feature to develop the preservative system, which was possible to reduce the concentrations of ammonia and carcinogenic nitrosamine in the NR latex.

Deproteinized natural rubber (DPNR) was made from sodium hydroxymethylglycinate latex (SH-latex) and ammonia latex (NH 3 -latex) by mixing with different forms of ethylenediaminetetraacetic acid (EDTA) in the presence of sodium dodecyl sulfate (SDS). The mixtures were stirred at room temperature followed by centrifugation to separate the denatured proteins. The optimized reaction contained 0.01 wt% ethylenediaminetetraacetic acid tetrasodium (EDTA-4Na) with 1% SDS. The nitrogen contents of the DPNR from SH-latex and NH 3 -latex were reduced to 0.005 wt% and 0.008 wt%, respectively, compared to 0.551 wt% in the starting SH-latex and 0.587 wt% in the NH 3 -latex. SDS-PAGE analysis and FT-IR spectroscopy showed decomposition of latex proteins to peptides of smaller molecular weight. Physical properties of the DPNR rubber were studied. The novel EDTA-4Na treatment is considered an effective deproteinization method with potential application on both ammonia and nonammonia preservative systems.