Experimental
2.1. Materials
Concentrated NR latex (High ammonia grade, 0.7%), with
60% dry rubber content was purchased from Thai Rubber
Latex Corporation (Thailand) Public Co. Ltd. (Thailand). Two
grades of silica, precipitated silica (Tokusil233) and fumed
silica (ReolosilQS20), were purchased from Tokuyama
Siam Silica Co., Ltd. (Thailand) and Tokuyama Soda Co., Ltd.
(Japan), respectively. Typical properties of both types of
silica are compared in Table 1. The details of other rubber
chemicals are listed in Table 2. All mixing ingredients were
used as received.