Preparation graft copolymers of deproteinised natural rubber latex and high ammonia concentrated natural rubber latices with methyl methacrylate
การเตรียมกราฟต์โคพอลิเมอร์ของน้ำยางธรรมชาติโปรตีนต่ำและน้ำยางข้นชนิดแอมโมเนียสูงด้วยเมทิลเมทาคริเลท
Charoen Nakason, Asst. Prof., D. of Rubber Tech. and Polymer Sci., F. of Sci. and Tech., PSU.
Azizon Kaesaman, D. of Rubber Tech. and Polymer Sci., F. of Sci. and Tech., PSU.
Nikorn Yimwan, B.Sc. Student in Rubber Tech., PSU.
Corresponding e-mail : ncharoen@bunga.pn.psu.ac.th
Grant : Government Budget
Published : Songklanakarin J Sci Technol 2000, 22(4) : 467-476
Key words : deproteinised natural rubber (DPNR), graft copolymer, methyl methacrylate,
high ammonia concentrated natural rubber latex, proteolytic enzyme (Opticlean)
Deproteinised natural rubber latex (DPNR) was prepared by incubation of fresh natural latex with a proteolytic enzyme (Opticlean) in the presence of emulsifier. The amount of protein in terms
of nitrogen content was decreased from the original 0.9% to 0.07%. DPNR was later used to prepare graft copolymer with methyl methacrylate (MMA). The results were compared with graft copolymer prepared from untreated high ammonia concentrated natural rubber latex (HA). It was found that percentage conversion for the reaction using DPNR is higher than that of graft copolymerisation of
high ammonia concentrated natural rubber latex at every mole ratio of natural rubber to MMA (tested on mole ratio of NR:MMA = 95:5, 90:10, 80:20, 70:30 and 60:40, respectively). Grafting efficiency indicates percentage of grafted poly (methyl methacrylate) (PMMA) and grafted natural rubber mo-lecules. It was found that the grafting efficiency decreased with mole ratio of natural rubber to MMA for both types of latex. However, graft copolymerisation of DPNR exhibits higher grafting efficiency. Grafted PMMA was examined by means of extraction and absorption ratio of infrared spectrum at the wave number of 1732 cm-1 to 835 cm-1.The results showed higher PMMA content in graft copolymer of DPNR. Also an increasing trend of PMMA content in graft copolymer was found for graft copoly-merisation of both types of latex. Average particle size of DPNR was arger than that of field natural latex. As may be expected, the particle size of graft copolymer was larger than the starting latex par-ticles. It was also found that particle size of graft copolymer of DPNR is larger than that of its coun-terpart. The difference between the behaviour of DPNR and untreated high ammonia concentrated natural rubber latex was due to the removal of protein. It is believed that protein acts as free radical scavenger. It terminates activity of free radical during the initiating process of graft copolymerisation.
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