Abstract:
A serin type Proteolytic Enzyme (PE) was used as a substitute for traditionally used
papain which has no reliable supply at present in the local market, for the manufacture of
Deproteinized Crepe Rubber (DPCR). Field latex was coagulated by different PE
dosages varying from 1 to 4 ml with 1 ml intervals per litre of the diluted field latex at
10% DRC and matured for 72 hours. The control sample was coagulated within 24 hours
using 1% formic acid and all coagula were converted into pale crepe form. The impact of
the maturation period (24-72 hours) on raw rubber properties was also studied using the
selected sample which meets the lowest Nitrogen Content (NC) among all the candidate
samples. Raw rubber properties, curing characteristics, and physicomechanical properties
of all the vulcanizates were studied. All enzyme-treated samples showed lower NC (0.10-
0.14%w/w) than the control (0.31%w/w). It was noticed that the increase of PE volume
and maturation period reduced the NC in the samples. Raw rubber properties of the
enzyme-treated samples with a 72-hour maturation period have complied with the
required specifications of DPCR except for the Plastic Retention Index (PRI). It was
found a reduction of PRI and ash content while increasing in Po values with the increment
of PE dosage and maturation period. However, the enzyme treatment (4ml/liter) with a
24-hour maturation period was able to achieve the slightly higher PRI value (63.3%) than
the recommended value (60%) for both control and DPNR. It was found that curing time
(T90) of the control sample was higher than the enzyme-treated samples and the control
sample showed better tensile strength than the enzyme-treated samples due to the protein
reinforcement effect and higher crosslink density. Overall, it could be concluded that the
selected enzyme has the potential to use it for manufacturing DPCR.
Keywords: Deproteinized crepe rubber, Nitrogen Content, Maturation period, Raw rubber
properties
