Epoxidized natural rubber (ENR) was filled with starch and molybdenum disulfide (MoS2) on different ratios. The curing properties and viscoelastic behavior of the composites was tested by rubber processing analyzer, and the morphological structure of the composites samples were characterized by SEM. The mechanical properties, the thermal decomposition behavior, tensile strength, hardness value, friction coefficient, abrasion resistance and swelling ratio were investigated to verify the property improvement of the ENR composites. From the results of all the tests, it can be found that the intermolecular interaction increased with increasing starch content. And the mechanical properties also increased. The possible reason may be the starch could provide the better combination with ENR rubber matrix due to the hydrogen bonding. And with the addition of molybdenum disulfide, the friction coefficient and abrasion resistance properties were improved due to the lubrication of molybdenum disulfide.

Epoxidized natural rubber(ENR)에 전분과 이황화몰리브덴이 다양한 비율로 혼합되었다. 제조된 복합체의 경화 물성과 동적점탄성은 고무 가공 분석기로 측정되었고, 시료의 형태학적 구조는 SEM으로 확인되었다. 기계적 물성, 열분해성, 인장강도, 경도, 마찰계수, 내마모성, 팽윤율도 물성 향상을 확인하기 위하여 조사되었다. 모든 실험 결과에서, 충전제-충전제 상호작용은 전분 함량이 증가함에 따라 향상되었음을 알 수 있었다. 그리고 기계적 물성도 따라 향상되었다. 그 원인은 전분과 ENR 고무 사이에 수소 결합이라는 더 나은 결합의 형성이었다. 또한 이황화몰리브덴의 첨가에 따라, 고무복합에의 윤활성이 증가되어 마찰계수와 내마모성이 개선됨을 알 수 있었다.

Keywords: epoxidized natural rubber, starch, molybdenum disulfide, mechanical properties

Epoxidized natural rubber (ENR) has been introduced as a modified form of natural rubber (NR). As the natural rubber is epoxidized, its chemical and physical properties change according to the extent to which the mole% of modification is introduced.¹ For instance, the glass transition temperature, T_g, is raised, room temperature resilience is reduced, the rubber becomes increasingly more oil resistance and im-pervious to gases, polymer viscosity is increased and the polymer becomes more polar as the degree of epoxidation is increased. Some of these properties are more akin to those of synthetic rubber than NR.² Filled ENR has been a popular research subject due to the versatility of the ENR to accept numerous types of fillers and reinforcement.³ Baker and Gelling⁴ have found that high loading of silica can be incorporated into ENR and significant reinforcements were observed even without the addition of coupling agent. In another study, Nasir et al.,⁵ observed that incorporation of γ-mercaptopropyl-trimethoxysilane (A-189) coupling agent into silica filled ENR has resulted in a significant improvement in the tensile and tear strength of the vulcanizates, due to the form of hydrogen bonding and high hydrophilicity.
It is known that in the case of filled vulcanizates, the efficiency of reinforcement depends on a complex interaction of several fillers related parameters, such as particle size, particle shape, particle dispersion, surface area, surface reactivity, structure of the filler and the bonding quality between the fillers and rubber matrix.⁶
In this research, the –OH groups in starch and the –S groups in molybdenum disulfide provide the polar bonding combination with the ENR, due to the hydrogen bonding effect and other interaction force, the new physical crosslinking had been formed, which could provide the mechanical properties reinforcement for ENR.⁷ After filling with fillers in difference ratio, the vulcanizates were vulcanized during the curing process. Finally, the surface state, TGA, tensile strength, hardness, friction coefficient, abrasion resistance and swelling ratio had been characterized.