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A good dispersion of silica in a rubber vulcanizate is important as it influences the filler-to-rubber interaction and consequently the final properties. This paper presents an investigation into the morphology of silica-reinforced Natural Rubber (NR) in presence and absence of a silane coupling agent, bis(triethoxysilylpropyl) tetrasulfide (TESPT). Micro-and nano-dispersion morphologies of silica in NR and Deproteinized Natural Rubber (DPNR) are studied by using Atomic Force Microscopy (AFM). Using a special network visualization technique based on Transmission Electron Microscopy (TEM), insight into the silica and rubber interaction in the NR and DPNR is gained. In absence of silane, vacuoles around the silica particles are formed as a result of a weak filler-polymer interaction, while the presence of silane leads to strong filler-to-rubber bonding, which prevents formation of vacuoles.Improvement of the micro-dispersion of silica in the NR and DPNR vulcanizates with the use of TESPT is observed from AFM phase imaging. The correlation between the filler-to-rubber interaction as analyzed by TEM and AFM and bound rubber contents as well as the Payne effect is discussed.

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Modification of natural rubber via epoxidation process increases its compatibility with highly polar filler like silica. In this work, epoxidized natural rubber (ENR) reinforced with silica compound is evaluated for truck tire tread compound. The rheological, physical and dynamic properties as well as the bound rubber content of ENR-silica tread compound are discussed. The results show that ENR-silica compound has high chemically bound rubber indicating the good interaction and bonding between rubber and silica. In addition, the dynamic test shows the ENR-silica vulcanizate exhibit higher Tan delta at 0 °C and lower tan delta at 60 °C as compared to conventional natural rubber-carbon black vulcanizate, which gives indication of higher wet grip and lower rolling resistance of the ENR vulcanizate. The use of ENR reinforced with silica filler in tread compound is a unique combination that offers renewable material for greener tire application.

The thermal history, and in particular the mixing dump temperature, is a parameter of paramount importance in mixing rubber and silica with a silane coupling agent in order to achieve proper silanization of silica and to avoid premature scorch reactions. The influence of the mixing dump temperature on the performance of silica-reinforced natural rubber (NR) is investigated. The investigation also includes the effect of nonrubber constituents, primarily proteins in NR, by using deproteinized natural rubber (DPNR) and synthetic polyisoprene (IR). The vulcanization properties and rubber-to-filler interactions of silica-reinforced NR in the presence and absence of a silane coupling agent are highlighted. With increasing mixing dump temperature, the silanization reaction between silica and silane coupling agent proceeds further. At a sufficiently high dump temperature, filler–filler interactions in the NR–silica compounds are reduced and the silica–rubber interaction improved, as evidenced by a drop in the Payne effect and increment in chemically bound rubber. It is demonstrated that NR and IR compounds mixed until they are above the optimum dump temperature exhibit cure reversion and reduction in tensile properties. On the other hand, DPNR–silica vulcanizates show slightly more constant physical properties.

A reprocessable elastomeric vulcanisate based on Epoxidised Natural Rubber with 50 mol-% epoxide content (ENR-50) was evloved by applying a self-assembled network based on thermochemically exchangeable ester crosslinks to the system. Hydrolysed Maleic Anhydride (HMA) as crosslinking substance in the presence of 1,2-DiMethylImidazole (DMI) as esterification accelerator and Zinc Acetate Dihydrate (ZAD) as transesterification catalyst was employed to generate the exchangeable ester crosslinking system. A sulphur-cured ENR-50 vulcanisate possessing a permanent sulphide crosslinking network was prepared as reference. Based on the results from cure characteristic and chemical structure analyses, the ENR-50 crosslinked with HMA behaves as a dynamic network because of a transesterification reaction catalysed by ZAD, promoting an exchangeable crosslinking network in the system. This dynamic network contributes to an intermolecular rearrangement of the ester crosslinking bonds at elevated temperatures, enabling interfacial self-adhesion and so reprocessability of the vulcanisates. The obtainable vulcanisates can be reprocessed, yielding relatively high retention of mechanical properties compared to their pristine counterpart. The interfacial self-adhesion and reprocessability of the vulcanisates have shown to significantly be improved with a higher loading of ZAD and elevated temperatures. This concept essentially shows a prospect towards developing e.g. novel recyclable and selfhealing systems for elastomers.

Seiring dengan kesedaran terhadap kesan rumah hijau dan isu pemanasan global, banyak usaha dilakukan ke arah penghasilan produk yang mesra alam dan boleh dikitar semula. Salah satu subjek yang digemari adalah penggunaan bahan buangan pertanian menjadi produk yang boleh digunapakai. Sekam padi yang dihasilkan daripada pengisar padi semasa proses penghasilan beras, mengandungi tahap silika yang tinggi. Sekam padi mempunyai potensi untuk dijadikan pengisi berdasarkan pada kelebihan daripada segi sumber yang tidak terhad dan kosnya yang murah. Kebanyakan kajian yang terdahulu melibatkan abu sekam padi sebagai pengisi dalam sebatian getah dan komposit. Bagaimanapun, kajian ini lebih menumpukan kepada serbuk sekam padi tanpa membakar sekam tersebut dan digunakan sebagai pengisi dalam sebatian getah. Keberkesanan serbuk sekam padi ini diuji pada sifat reologi dan sifat fizikal dan mekanik bagi sebatian getah. Sekam padi dihancurkan dan ditapis untuk mendapatkan serbuk sekam padi bersaiz 300 m dan 180 m. Komposit getah berisi serbuk sekam padi disediakan menggunakan mesin dua rola bersaiz makmal. Dengan menggunakan sistem pemvulkan konvensional, sifat reologi diuji dengan mesin Monsanto Rheometer. Tahap pengisian ditingkatkan daripada 0 kepada 50 pphr pada sela 10 pphr. Vulkanisat kemudiannya diuji. Penyebaran serbuk sekam padi dalam vulkanisat diuji melalui mikrograf SEM. Sebagai perbandingan, silika digunakan pada 40 dan 50 pphr manakala karbon hitam digunakan pada 50 pphr. Keputusan menunjukkan bahawa sifat fizikal dan mekanikal vulkanisat berisi serbuk sekam padi masih tidak dapat menandingi vulkanisat berisi karbon hitam. Bagaimanapun, terdapat beberapa sifat yang setanding dengan vulkanisat berisi silika. Serbuk sekam padi juga lebih mudah diadun dengan getah jika dibandingkan dengan silika. Kata kunci: Serbuk sekam padi; sebatian getah As the greenhouse effects and global warming issues focus their stand in the fast–changing modern world, more efforts are being done towards manufacturing products, which are environment–friendly and recyclable. One of the favourite subjects is the utilization of agricultural waste into useful value–added product. Rice husk which is generated by the rice mills during rice processing composes mainly organo siliceous material. Together with its abundance supply and attractive price, rice husk has the potential to be used as filler in polymeric materials especially rubber. Most of the previous work done was on burnt rice husk ash as filler for rubber or composite. Consequently, this study will concentrate on utilizing ground rice husk, without burning it as filler in rubber compounding. The effectiveness of ground rice husk is determined by evaluating the rheological behaviour and physical properties of rice husk powder (RHP)–filled rubber vulcanisates. Rice husks were ground and sieved to obtain 300 m and 180 m of RHP. The RHP–filled rubber vulcanisates for both powder sizes were prepared using a laboratory two roll mill. Using a conventional vulcanization system, the cure behaviour was assessed by Monsanto Rheometer. Filler loading was varied from 0 to 50 pphr at 10 pphr interval. The vulcanisates were then tested. The dispersion of RHP in the vulcanisates was evaluated using scanning electron microscopy (SEM) analysis. For comparison purposes, commercial silica was used at 40 and 50 pphr whilst carbon black was used at 50 pphr. The results showed that the physical properties of RHP–filled vulcanisate are still inferior to carbon black–filled vulcanisate but some of the properties are comparable to silica–filled vulcanisate. The RHP also offers processing advantages over silica. Key words: Rice husk powder; rubber compounding