No abstract

Studies show that the mixing process is one of the most critical steps in the rubber processing, which directly affects the performance and service life of rubber products. However, unjustifiable complexity, high processing time, and low mixing quality of the conventional mixing technologies restrict the development of the rubber industry. Aiming at the deficiency of rubber mixing technology at present, the wet mixing technology and continuous mixing technology are complementary to each other, and the continuous wet mixing technology is developed. Then experiments are carried out to evaluate the performance of the proposed method. The obtained experimental results show that the wet mixing and continuous mixing technologies have synergetic effects, thereby simplifying the mixing process and improving the quality and continuity of the mixing process. It is found that the continuous wet mixing technology significantly improves the properties of the rubber compound compared with the conventional dry mixing method. The proposed method not only has reasonable processing properties but also significantly improves the physical, compressive fatigue, degree of dispersion and dynamic mechanical properties of the compound compared with those from the conventional dry mixing process.

Using sodium thiosulfate and hydrochloric acid as the raw materials and a silica aqueous dispersion as the carrier, sulfur is generated in situ by a chemical precipitation method, and an in situ sulfur‐silica/natural rubber (in situ S‐Silica/NR) composite is prepared. The in situ sulfur is characterized, and its effects on the natural rubber composites' cross‐linking density, vulcanization characteristics, mechanical properties, aging properties, dynamic mechanical properties, and Payne effect are studied. The experimental results show that the particle size of in situ sulfur is small, with a maximum of 5 μm, and the cross‐linking ability is stronger than commercial sulfur. Due to the strong surface adsorption force of silica, the interfacial bonding strength is enhanced, and the dispersion of the two components in the rubber matrix is improved. Compared with commercial sulfur‐silica/natural rubber (S‐Silica/NR) composites, the tensile strength is 20.3% higher, the elongation at break is 28.5% higher, and it better retains its aging properties and has a lower rolling resistance. This study provides a theoretical basis for the development of functional rubber vulcanizing agents and the preparation of high‐performance rubber composites.

Butyl rubber (IIR) is widely used in tire inner liners and tubes, vulcanization bladders, and shock absorption materials due to its extremely low air permeability, excellent aging resistance, and good energy absorption. However, its low thermal conductivity affects its performance and the service life of the product, while it also limits its application. Therefore, the preparation of butyl rubber composites with high thermal conductivity is of great significance and practical value. This paper proposes the use of a dry ice expansion pre‐dispersion flocculation method to improve the thermal conductivity of butyl rubber composites by simultaneously doping graphene oxide (GO) and multiwalled carbon nanotube (MWCNTs) in butyl latex. The experimental results of this study show that the dry ice expansion pre‐dispersion method uses the huge volume expansion force of dry ice to break the nanofillers aggregates during sublimation, promote the dispersion of nanofillers, and achieve better modification effects. Moreover, GO and MWCNTs have good synergistic thermal conductivity, which can establish a complete three‐dimensional thermal conductivity network inside the composite. When 5 wt% of GO and 5 wt% of MWCNTs were added, GO/MWCNTs/IIR composites exhibited the highest thermal conductivity, which reached 0.423 W m−1 K−1 at 180°C.

This study proposes that the foaming pre‐dispersion technology is combined with the gas‐phase‐assisted spray technology, and a foaming agent potassium oleate is introduced. The volume expansion power generated by the bubbles promotes the dispersion of the filler. The uniformity of foaming promotes the chemical bridging of potassium oleate between rubber and silica. Then, with a large velocity difference between the compressed air and the emulsion, the gas‐phase‐assisted spray gun refines the emulsion and breaks the filler aggregates. Next, the atomized droplets splash on the surface of the high‐temperature roller, and then deposit on it to achieve instant drying, which reduces the loss of non‐rubber components, thereby improving the preparation efficiency and comprehensive properties of masterbatch. The Payne effect of the composite prepared by the FGS technology is weaker. The tensile strength, elongation at break, and tensile product of the vulcanizate prepared by the FGS technology with 7 phr PO have increased by 9%, 5%, and 15%, respectively, and the aging coefficient is 23% higher than that of the dry mixing.

The drying process of natural rubber latex significantly affects the structure of the raw rubber network and vulcanizate crosslinking network, resulting in various anti-aging performances. In the present study, a microwave generator was used as an efficient source of clean energy; potassium oleate was introduced as a foaming agent to increase the porosity and water loss channel of the latex system. Aiming at dehydrating and drying natural rubber latex efficiently, an aging resistant rubber composite was prepared. Meanwhile, the mechanism of the foaming agent-assisted microwave drying process on the raw rubber network and the cross-linking network was studied. The experimental results show that the prepared rubber using by this process has higher plastic retention and fluidity. Moreover, it contains more non-rubber components (e.g. protein and acetone extract) and better network structure of raw rubber and vulcanized rubber. It is found that applying this process increases the tensile product by 13.5% and the retention rate of the tensile product after aging by 15.3 times. This process is important for the development of the rubber industry in the direction of green environmental protection, energy conservation, and high efficiency.

No abstract

In this study, different processes are performed for the preparation of natural rubber latex (NRL)/silica composites. A novel approach is to use spray sputtering technology combined with in situ method to improve the dispersion of silica in rubber latex matrix and further improve the properties of vulcanizates. Results show that in situ silica in rubber matrix prepared from NH4Cl and Na2SiO3 has better Payen effect than other processes. Meanwhile, when the in situ silica reached 10 phr in the rubber matrix, the dosage can suitably match the dispersion capacity of the spray sputtering process with superior comprehensive mechanical properties. Compared with the traditional precipitation method, the tensile strength and tear strength of the silica/NR composites prepared by spray sputtering technology combined with in situ method were increased by 34.7% and 19.7%.