Development of natural rubber/chloroprene rubber blends for rubber boot production
2004
Varaporn Kajornchaiyakul(Department of Agriculture, Bangkok (Thailand). Rubber Research Institue) | Autcharee Tragarnvaraporn(Chulalongkorn University, Bangkok (Thailand). Faculty of Science) | Shuchart Baramee(Chulalongkorn University, Bangkok (Thailand). Faculty of Science)
STR5/CR and homogenizing agent affected physical properties of the blend. It was found that with increasing CR content the properties of the rubber compounds, i.e. mooney viscosity, scorch time and cure time, increased. The properties both before and after ageing at 100 deg C for 22 h, i.e. specific gravity, modulus, hardness, compression set, oil or grease resistance, ozone resistance and anti-static electricity properties, showed considerable improvement by the increasing of CR while elongation at break decreased and tensile strength slightly increased. With regard to mechanical properties, the rubber appeared to have two glass transition temperatures (Tg) and two tan delta peaks whereas single rubber blend showed only one Tg and one narrower tan delta peak. However, with the addition of homogenizing agent the differences between the two Tg of the blends became smaller. This indicated the homogeneity of the blend was improved and thus its tensile strength was also slightly increased. Comparison of the blend properties with those of the standard specifications of rubber boot revealed that the blend of STR5/CR at 30/70 without homogenizing agent and at 40/60 with homogenizing agent met the standard specifications. Both cases had been prepared, using carbon black (N660) as reinforcing filler, and cured with efficient sulphur vulcanization system. Moreover, the substitution of STR5 for CR resulted in lower cost for normal rubber boot production than using only CR. Blend of 40 percent STR5 costs 82.02 baht/kg while using only CR costs 125.88 baht/kg, thus material cost can be lowered by about 1.53 times. Substitution of 40 percent STR5 in the blend can add the value to STR5 by 25 times.
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