Sulfur prevulcanized NR latex, along with the ingredients,
were procured from Rubber Research Institute
of India (Kottayam, Kerala, India). This concentrated,
high-ammonia (1%) NR latex contained 60%
dry rubber. For prevulcanization, this latex was mixed
with the ingredients listed in Table I under slow stirring.
The compounded latex was then heated to 70°C
in a water bath with low stirring for 4 h. The prevulcanized
latex obtained was cooled to room temperature
and the initial ammonia content was restored by
adding ammonia solution. The NR latex was then
stored in tight plastic bottles until use.
PUR latex (Impranil DLP-R) containing 50% polyester-
based polyurethane was supplied by Bayer (Leverkusen,
Germany).