A study about the structure of vulcanized natural rubber/styrene butadiene rubber blends and the glass transition behavior

Physical Properties and Biodegradability Evaluation of Vulcanized Epoxidized Natural Rubber/Thermoplastic Potato Starch Blends

The sustainable material-thermoplastic potato starch (TPS)-was blended with modified natural rubber-epoxidized natural rubber (ENR). The poor mechanical properties of the ENR/TPS blends limited the application. Sulfur vulcanization is a common and economical method to improve the mechanical properties in the rubber industry. To fully understand the relationship between vulcanization systems and ENR/TPS blends and the sustainability of the developed material, the effects of a vulcanization accelerator (N-cyclohexylbenzothiazole-2-sulphenamide (CBS), 2-mercaptobenzothiazole (MBT), N-tert-butylbenzothiazole-2-sulphenamide (TBBS)) and a system type (conventional vulcanization (CV), semi-efficient vulcanization (SEV) and efficient vulcanization (EV)) on curing characteristics, mechanical and thermal properties, water absorption and biodegradability were systematically evaluated. The results indicate that vulcanization significantly improves the mechanical properties of ENR/TPS blends. The performance optimization of the CBS-CV vulcanization system is the best for improving the mechanical properties and reducing the water absorption. The CBS-CV curing system makes ENR/TPS less biodegradable (12-56% of mass loss) than other accelerators and systems. TBBS-CV makes the material more biodegradable (18-66% of mass loss). The low rubber content enables the rapid biodegradation of the vulcanized blend. This has implications for research on sustainable materials. The material can be applied for eco-friendly packaging and agricultural films, etc. The investigation on performance by using common accelerators and systems provides ideas for industries and research.

Effect of Morphology/Structure on the Phase Behavior and Nonlinear Rheological Properties of NR/SBR Blends

The evolution of the morphology/structure and the nonlinear viscoelasticity of rubber blends under large amounts of strain are key scientific issues for the design and manufacture of rubber blends. The rheological responses of natural rubber/styrene-butadiene rubber (NR/SBR) blends are traced over a wide range of blend compositions to gain an insight into the effect of blend morphology on their nonlinear viscoelasticity. We also prepare NR + SBR physical blends without melt mixing to distinguish the contributions of composition and blend morphology to the viscoelastic response. The microscopic heterogeneous gel-like structure of NR/SBR blends may remarkably weaken their strain softening and improve their modulus hysteretic recovery under large strain, which may be attributed to the heterogeneous microscopic deformation for the NR and SBR phases. Furthermore, additional elastic contribution resulted from the increasing interfacial energy of domain deformation. This may provide some new insights into the effect of blend morphology on the Payne effect of rubber blends.

CHANGES IN THE MECHANICAL, MICRO-, AND NANO-STRUCTURAL PROPERTIES OF REINFORCED VULCANIZED NATURAL RUBBER COMPOUNDS: THEIR DEPENDENCE ON THE SiO2/CB RATIO

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Preparation and Characterization of Rubber Blends for Industrial Tire Tread Fabrication

The physico-mechanical properties of variable rubber blends including epoxide natural rubber (ENR), polybutadiene rubber (BR), and solution polymerized styrene-butadiene rubber (SBR) filled with silanized silica and carbon black mixtures were explored. The tensile, hardness, resilience, abrasion, and fatigue behavior were investigated. An optimized composition involving 30 phr of ENR and 70 phr SBR filled with mixtures of carbon blacks and silanized silica was proposed to be a suitable composition for the future development of green passenger truck tires, with low rolling resistance (fuel saving ability), high wear resistance, and desired fatigue failure properties.

Phase Morphology of NR/SBR Blends: Effect of Curing Temperature and Curing Time

The morphology of natural rubber/styrene–butadiene rubber blends (NR/SBR) was characterized by atomic force microscopy (AFM), with regard to curing temperature and curing time. The changes in blend morphology were directly visualized by AFM which confirmed the results of indirect experiments like differential scanning calorimetry (DSC). Comparing the phase morphologies at different curing temperatures indicated that the domain size of SBR increases with temperature at lower curing temperatures, but domain growing stops at the latest scorch time. This effect is explained by longer scorch times at low curing temperatures which facilitate phase separation, while the short scorch times at higher temperatures meant that the coalescence of SBR phases was hindered by cross-linking between polymer chains.

Prediction of the glass transition temperature and design of phase diagrams of butadiene rubber and styrene-butadiene rubber via molecular dynamics simulations

To prevent car accidents, it is important to evaluate the thermal stability of tire rubbers, such as natural rubber (NR), butadiene rubber (BR), and styrene-butadiene rubber (SBR). Controlling the glass transition temperature (T_g) is the main factor for obtaining desirable thermal stability. Here, we developed an optimized equation for the prediction of the T_g of the various rubber systems using molecular dynamics (MD) simulations. We modeled a random copolymer system, blended monomers, and calculated the T_g of butadiene isomers in each composition. From these results, we designed the T_g contour of ternary cis-trans-vinyl butadiene and derived an equation of T_g for the ternary system. Moreover, we developed an equation to evaluate the pseudo-ternary T_g of quaternary SBR and plotted it. Our results present a novel way of predicting the T_g of ternary BR and quaternary SBR, which is critical for rational tire design with optimized thermal and mechanical stability.

Influence of poly(methyl methacrylate) grafted multiwalled carbon nanotubes on the mechanical and thermal properties of natural rubber nanocomposites

In this study, we describe the preparation and characterization of natural rubber nanocomposites filled with poly (methyl methacrylate) grafted multiwalled carbon nanotube. The use of various filler loadings (1, 2, 3, and 5 wt %) and melt blending method was employed. From the results, nanocomposite with 1 phr filler loading showed the optimal tensile strength of 4.92 MaP, while that of the carbon black N330 filled natural rubber with similar filler loading found to be 2.48 MaP. The nanocomposite with optimal tensile strength exhibited a good filler dispersion in the natural rubber matrix, which was depicted by the field emission scanning electron microscopy images. The thermal degradation temperature of the vulcanized neat natural rubber composite was increased from 380℃ to 462℃ with 1 phr filler loading. The polymer modified multiwalled carbon nanotube improved the mechanical and thermal properties of natural rubber, suggesting its potential as reinforcement filler in rubber industry.

Chitosan-graft-poly(n-butyl acrylate) copolymer: Synthesis and characterization of a natural/synthetic hybrid material

Two chitosan polymers with different deacetylation degree and molecular weight were subjected to grafting reactions with the aim to enhance the properties of these bio-based materials. Specifically, n-butyl acrylate in different proportions was grafted onto two different deacetylation degree (DD%) chitosan using radical initiation in a surfactant free emulsion system. Infrared spectroscopy was used to confirm grafting and products grafting percentage and efficiency were evaluated against acrylate/chitosan ratio and DD%. Thermal and structural properties and the behavior against water of the raw and grafted biopolymers were studied using several experimental techniques: differential scanning calorimetry, transmission electron microscopy, dynamic light scattering, water swelling, contact angle and positron annihilation lifetime spectroscopy. The influence of the grafting process on the morphological and physicochemical properties of the prepared natural/synthetic hybrid materials is discussed.