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Abstract
Preliminary Study on the Preparation of Latex Foam Rubber
from Graft Copolymer of Deproteinised Natural Rubber and Methyl Methacrylate
Deproteinised natural rubber (DPNR) latex was prepared
by incubation of fresh field natural rubber latex with a proteolytic enzyme
in the presence of an emulsifier The nitrogen content was decreased from
0.9% (in the fresh field natural rubber latex) to 0.07% (in the DPNR). A
graft copolymer of the deproteinised natural rubber latex and poly(methyl
methacrylate) (PMMA) was then synthesised using tert. butylhydroperoxide
and tetraethylene pentamine as a redox initiator. The presence of grafted
PMMA in the natural rubber molecules was confirmed using FTIR. Intense absorption
peaks at 1732 cm-1 (-C=O stretch) and 1140 cm-1 (-C-O
stretch) were observed. It was also found that the quantity of grafted PMMA
increased with the increase in the level of MMA used in the grafting reaction.
The graft copolymer latex was later compounded and processed into a latex
foam rubber. Results showed that the latex of graft copolymer blended with
high ammonia concentrated latices provided high quality latex foam rubber.
This included surface appearance and physical properties, such as hardness,
compression set and density. It was also found that hardness, compression
set and density of the latex foam rubber increased with the increase in
the level of graft copolymer in compounding formulation. Furthermore, at
the same blend ratio, the properties increased with the increase in the
level of methyl methacrylate used in the grafting reaction.

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