The demand for truck–bus radial (TBR) tires with enhanced fuel efficiency has grown in recent years. Many studies have investigated silica-filled natural rubber (NR) compounds to address these needs. However, silica-filled compounds offer inferior abrasion resistance compared to carbon black-filled compounds. Further, the use of NR as a base rubber can hinder silanization and coupling reactions due to interference by proteins and lipids. Improved silica dispersion be achieved without the use of a silane coupling agent by introducing epoxide groups to NR, which serve as silica-affinitive functional groups. Furthermore, the coupling reaction can be promoted by facilitating chemical interaction between the hydroxyl group of silica and the added epoxide groups. Thus, this study evaluated the properties of commercialized NR, ENR-25, and ENR-50 compounds with or without an added silane coupling agent, and the filler–rubber interaction was quantitatively calculated using vulcanizate structure analysis. The increased epoxide content, when the silane coupling agent was not used, improved silica dispersion, abrasion resistance, fuel efficiency, and wet grip. Once a basic level of silica dispersion was secured by using the silane coupling agent, both the abrasion resistance and wet grip improved with increasing epoxide content. Furthermore, the silane coupling agent could be partially replaced by ENR due to the high filler–rubber interaction between the ENR and silica. Therefore, epoxidation shows potential for resolving the issues associated with poor coupling reactions and abrasion resistance in silica-filled NR compounds.

A composite solid propellant which generates high propulsive force in a short time is typically composed of an oxidizer, a metal fuel powder and a binder. Among these, the binder is an important component. The binder maintains the mechanical properties of propellant grains and endures several thermal and mechanical stresses in the engine. Several studies have been reported for the development of energetic propellant binders for increasing the propellant′s propulsive force. While several materials have been studied for the synthesis of energetic prepolymers, a nitramine-group-containing prepolymer is a suitable candidate because these types of prepolymers are less toxic and more cost-effective when compared to the traditional glycidyl azide polymers (GAP) and triazole-based prepolymers. Considering the lack of studies for the binder using a nitramine-group-containing prepolymers, we synthesized a nitramine-group-containing monomer and polymerized a nitramine-group-containing prepolymer. The prepolymer was then used for the preparation of the binder and its thermal and mechanical properties, as well as the effect of the plasticizer, were studied. The binder that was prepared using the prepolymer containing a nitramine-group showed very high elongation, tensile strength. Nitrate-ester (NE)-type plasticizer could reduce the glassy transition temperature (T_g)of the binder successfully. Also, high-energy is released due to the decomposition of the nitramine-group at around 245 °C, thus exhibiting the efficiency of the nitramine-group-containing prepolymer as an excellent energetic binder material.

In this study, we examined the feasibility of using epoxidized liquid isoprene rubber (E-LqIR) as a processing aid for truck and bus radial (TBR) tire treads and investigated the effects of the epoxide content on the wear resistance, fuel efficiency, and resistance to extraction of the E-LqIRs. The results confirmed that, compared to the treated distillate aromatic extract (TDAE) oil, the E-LqIRs could enhance the filler–rubber interactions and reduce the oil migration. However, the consumption of sulfur by the E-LqIRs resulted in a lower crosslink density compared to that of the TDAE oil, and the higher epoxide content decreased the wear resistance and fuel efficiency because of the increased glass-transition temperature (T_g). In contrast, the E-LqIR with a low epoxide content of 6 mol% had no significant effect on the T_g of the final compound and resulted in superior wear resistance and fuel efficiency, compared to those shown by TDAE oil, because of the higher filler–rubber interactions.

In the tire industry, solution styrene butadiene rubber (SSBR), which can introduce a functional group with good reactivity to silica at chain ends, is used to increase rolling resistance performance by considering fuel economy. However, this is not environmentally friendly because SSBR uses an organic solvent for polymerization, and it is difficult to increase its molecular weight. Functionalized emulsion SBR (ESBR) can solve the problems of SSBR. The molecular weight of ESBR molecules can be easily increased in an eco-friendly solvent, i.e., water. A functionalized ESBR introduces a functional group with good reactivity to silica by introducing a third monomer during polymerization. In this field, glycidyl methacrylate (GMA) has been reported to show the best properties as a third monomer. However, for GMA-ESBR, the viscosity is high and processability is disadvantageous. Therefore, we polymerized GMA-ESBR and manufactured silica compounds to clarify the causes of these problems. In addition, wet masterbatch (WMB) technology, which is a new compound manufacturing method, was applied to manufacture the silica compound, and the physical properties are compared with those of a dry masterbatch. The results clarified the problem of GMA-ESBR, which could be solved by using WMB technology.

Tread is an important component that directly affects the performance of passenger car radial (PCR) tires. Styrene-butadiene rubber (SBR) is mainly used for tire tread and it includes solution styrene-butadiene rubber (SSBR) and emulsion styrene-butadiene rubber (ESBR). Although SSBR is mainly used, the manufacturing process for SSBR is more challenging than ESBR, which is environmentally friendly, but has the disadvantage of a broad molecular weight distribution. To overcome this, a reversible addition-fragmentation radical transfer (RAFT) polymerization technique is used in ESBR polymerization. An environmentally friendly RAFT ESBR with a narrow dispersity can be polymerized. Here, carbon black-filled compounds were manufactured while using RAFT ESBR, and their properties were compared to ESBR. The analysis showed a low crosslink density of RAFT ESBR, due to the high polysulfide crosslink structure. We manufactured a carbon black-filled compound with the same crosslink density and structure as the ESBR carbon black-filled compound, and the effect of the dispersity of the base polymer was investigated. RAFT ESBR showed 9% better abrasion resistance and 29% better fuel efficiency than ESBR, according to the analysis of the data. The narrow dispersity can reduce energy loss and positively influence the abrasion resistance and fuel efficiency.

The implementation of vehicle electrification and autonomous driving technologies has recently emphasized the importance of abrasion resistance and fuel efficiency of truck bus radial (TBR) tire treads that undergo high loads and long driving times. In this study, a functionalized liquid butadiene rubber (F-LqBR) was introduced to replace the treated distillate aromatic extracted (TDAE) oil as a way to improve abrasion resistance and fuel efficiency in the TBR tire tread compound and to solve the oil migration. First, radical polymerization was used to synthesize nonfunctionalized LqBR (N-LqBR) and amino-LqBR with an amine group at the chain ends. The synthesized LqBRs were then substituted in place of TDAE oil to manufacture carbon-black-filled natural rubber (NR) compounds and to evaluate their physical properties. The results show that LqBRs improved the migration resistance and enhanced the abrasion resistance by lowering the glass transition temperature (T_g) of the compound. In particular, amino-LqBR improved carbon black dispersion in the rubber matrix through a chemical bond between the functional group of the carbon black surface and the base rubber. In conclusion, amino-LqBR successfully served as a processing aid in a carbon black-filled NR compound while simultaneously enhancing its fuel efficiency and abrasion resistance.