Unfilled Natural Rubber Compounds Containing Bio-Oil Cured with Different Curing Systems: A Comparative Study

Area of Science:

• Polymer Science
• Materials Science
• Sustainable Materials

Background:

• Natural rubber compounds are essential in various industries.
• Investigating sustainable alternatives to petroleum-based oils is crucial.
• Bio-oils offer a potential renewable resource for rubber compounding.

Purpose of the Study:

• To evaluate the effects of palm oil and soybean oil on natural rubber properties.
• To compare bio-oil performance in peroxide and sulfur curing systems.
• To understand the relationship between crosslink density and rubber compound properties.

Main Methods:

• Unfilled natural rubber compounds with bio-oils (palm, soybean) and distillate aromatic extract (DAE) were prepared.
• Compounds were cured using peroxide and sulfur systems.
• Vulcanization characteristics, crosslink density, and mechanical properties (modulus, tensile strength, elongation at break, compression set) were measured.

Main Results:

• Bio-oils did not significantly alter peroxide vulcanization but accelerated sulfur vulcanization.
• Bio-oils led to lower crosslink density in both systems.
• Increased crosslink density correlated with higher modulus, tensile strength, and hardness, and lower elongation at break and compression set.
• Bio-oil compounds exhibited lower modulus, tensile strength, and hardness, but higher elongation at break and compression set compared to DAE.
• Sulfur-cured bio-oil compounds showed less property deterioration than peroxide-cured ones.

Conclusions:

• Bio-oils significantly impact natural rubber's crosslink density and mechanical properties.
• The choice of curing system (peroxide vs. sulfur) influences bio-oil performance.
• Bio-oils present a viable, albeit property-modifying, alternative in rubber formulations, with sulfur curing offering better property retention.