Mechanical properties, gas permeability and cut growth behaviour of natural rubber vulcanizates: Influence of clay types and clay/carbon black ratios

Published Date
Polymer Testing
August 2012, Vol.31(5):645–653, doi:10.1016/j.polymertesting.2012.04.001
Material properties

Author 

• Nittaya Rattanasom ^a,b,c,,
• Sarawut Prasertsri ^a

• aDepartment of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
• bInstitute of Molecular Biosciences, Mahidol University, Salaya, Nakhonpathom 73170, Thailand
• cCentre for Rubber Research and Technology, Centre of Excellence of the Faculty of Science, Mahidol University, Nakhonpathom 73170, Thailand

Received 22 February 2012. Accepted 2 April 2012. Available online 7 April 2012. 

Abstract

The properties as well as cut growth behaviour of natural rubber (NR) vulcanizates filled with different mineral clay types, namely devolite and calcined, were studied. The effect of partial replacement of clays with carbon black on the properties was also elucidated while the hardness level of the vulcanizates was kept constant. It is found that 2 phr of devolite clay or calcined clay can be replaced by 1 phr of carbon black (N330) to maintain the hardness value. At similar hardness, the cure retardation and resilience of the samples tend to reduce when decreasing the clay/carbon black ratio while torque difference, strength and thermal ageing resistance show the opposite trend. Compared to devolite clay, calcined clay gives NR vulcanizates with lower gas barrier property as well as scorch and cure time, but higher crosslink density, modulus, tear strength and cut tensile strength. The results also reveal that the cut growth behaviour of the vulcanizate changes from a simple lateral growth to oblique crack with partial replacement of the clay with carbon black, corresponding to its higher cut tensile strength.

Keywords

Natural rubber

Clay/carbon black ratio

Mechanical properties

Gas permeability

Cut growth behaviour

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  Corresponding author. Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand. Tel.: +66 2441 9816x1137; fax: +66 2441 0511.

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