Studies on reinforcing effect of industrial nano silica in chloroprene vulcanizates containing carboxy-terminated liquid natural rubber

Maleic anhydride was chemically attached to depolymerized natural rubber, and the product was named as carboxy-terminated liquid natural rubber (CTNR). The CTNR can act as a potential plasticizer in chloroprene (CR) vulcanizates. This paper describes the use of commercial nano silica (NS) as a promising cost-effective filler, which can enhance the tensile properties and ageing resistance of the CR vulcanizates incorporated with CTNR (CR-CTNR). The enhancement in properties may be attributed to the increased bound-rubber content owing to the large surface area of the nano-sized filler. The characteristics of the NS-filled CR vulcanizates containing CTNR (NS CR-CTNR) were compared with those containing amorphous silica. The NS CR-CTNR vulcanizates showed superior ageing and oil resistance due to the finer rubber filler interaction modified by ionic cross linking.

ORIGIN OF ENERGETIC ELASTICITY AND ENTROPIC ELASTICITY OF NATURAL RUBBER WITH NANODIAMOND NANOMATRIX STRUCTURE

ABSTRACT The origin of energetic elasticity in conjunction with the entropic elasticity for natural rubber with a nanodiamond nanomatrix structure was investigated in terms of bound rubber formed between nanodiamonds, based on the interaction between natural rubber and nanodiamonds inside the nanomatrix. The natural rubber with a nanodiamond nanomatrix structure was prepared by reacting nanodiamonds with deproteinized natural rubber in the presence of tert-butylhydroperoxide/tetraethylenepentamine at 30 °C in the latex stage followed by drying. Morphology of the products was observed by two-dimensional and three-dimensional transmission electron microscopies. The effect of bound rubber on the mechanical properties of the products was investigated by measurements of the dynamic mechanical properties and differential scanning calorimetry. The contribution of bound rubber was estimated by combining the Takayanagi equation and modified Guth–Gold equation. A significant increase in complex modulus was attributed to the effect of the bound rubber.

MODIFICATION OF MIXTURES BASED ON ETHYLENEPROPYLENE RUBBER AND SILICON ACID FILLER

The aim of the work was to study the effect of bis-(triethoxysilylpropyl)-tetrasulfide (TESPT) mixed with carbon black N330 in a ratio of 1:1, as a technical product OFS 6945 on the structure and properties of rubber mixtures and rubbers based on ethylene propylene rubber of the brand Vistalon 2504N and silica filler (KKN) of the brand Rosil-175, taken at a dosage of 30 wt. h. per 100 wt.h. rubber. The content of TESPT was 0.035, 0.050 and 0.070 mmol / 100 g of rubber. A group of vulcanizing agents included sulphur, thiuram, captax, zinc oxide and technical stearin. Rubber mixtures were prepared on rollers Lb 320 160/160. Organosilane was injected into rubber at the same time as Rosil-175. The homogeneity of the filler distribution in the finished mixtures was evaluated based on the results of testing samples on the RPA-2000 vibrorheometer. Vulcanization characteristics were determined using an MDR-2000 device. The structure of mixtures and rubbers was studied by the method of equal swelling of samples in toluene. It is shown that with the increasing content of TESPT, the proportion of bound rubber in a three-component mixture of the rubber – filler – organosilane increases due to the formation of interfacial connections. The uniformity of distribution of silica fillers in rubber matrix also increases. Workability of the mixtures on roller equipment improves. The rate of cross-linking in the core period and the degree of cross-linking of macromolecules at the same time curing increase as well. As a result, the elastic-strength properties of rubbers determined in the static test mode are improved, the best complex of which is provided with an organosilane content of 0.050 mmol/100 g of rubber.

Mechanical properties and dissipation energy of carbon black/rubber composites

The effects of carbon black on the properties of rubber composites were studied in order to explore their value in producing low rolling resistance truck tires. Carbon black with different grades, N330 (coarser grade of 26–30 nm) and N220 (finer grade of 20–25 nm), was used as a reinforcing agent of natural rubber. The effects of different ratios of carbon black N330 at 40, 45, 50 and 55 parts per hundred rubber (phr) and N220 at 30, 35, 40 and 50 phr were investigated. Rubber composites with N220 had greater rubber/carbon black interaction than those with N330. The Mooney viscosity of rubber composite increased when the carbon black ratio increased. After vulcanisation of rubber, the samples were characterised by dynamic mechanical analysis, tensile strength and heat build-up. The results showed that the strength of rubber composites increased with increasing carbon black ratios. Interestingly, at the same bound rubber level, rubber composites with N220 presented lower dissipation energy, heat build-up and better mechanical properties than those with N330. This study indicated that reinforcement with an optimum amount of carbon black N220 would improve several desirable characteristics of rubber composites when used in low rolling resistance truck tires.

Vulcanizate Structures of SBR Compounds with Silica and Carbon Black Binary Filler Systems at Different Curing Temperatures

The tire industry has shown an increasing demand for the reduction in rolling resistance. Efforts have been made to improve the viscoelastic properties of tire compounds and reduce the weight of tires through optimization of the vulcanizate structure, which has become extremely complex. In this study, vulcanizates using carbon black and silica as binary fillers were prepared at various curing temperatures. Vulcanizate structures with respect to curing temperature were classified according to the chemical crosslink density by sulfur, carbon black bound rubber (i.e., physical crosslink due to carbon black), and silica-silane–rubber network. All properties exhibited a decreasing trend under the application of high curing temperatures, and the decrease in the crosslink density per unit content of filler with an increase in curing temperature was shown to be greater in carbon black than in silica. Mechanical and viscoelastic properties were also measured to evaluate the impact that the compound variates have on tire tread performance. These results serve as a guideline for determining the content and filler type and for setting the cure condition during the design of actual compound formulations to increase the crosslink density of rubber while retaining the necessary mechanical and viscoelastic properties for practical application.