Synthesis of nano zinc oxide and its effect on the cure characteristic and properties of natural rubber vulcanizates

In this work, nano ZnO was synthesized by a simple method using a polymeric substance as a dispersing agent. Characterization of the synthesized ZnO by XRD and SEM confirmed the ZnO was nanometric in size and had a wurtzite structure. The synthesized nano ZnO was used as an activator for natural rubber vulcanization. Different amount of ZnO, 1, 2 and 3 phr, was investigated in the rubber formulation and compared to convention ZnO at a typical amount (6 phr). The sample with 3 phr nano ZnO showed the lowest curing induction time with the highest (ML-MH) at all studied temperatures. Furthermore, the rubber sample with 3 phr ZnO achieved the best properties, i.e., crosslink density, rebound resilience, and hardness compared to the rubber sample with 6 phr conventional ZnO. Interestingly, the properties of rubber sample with 2 phr nano ZnO were probably equivalent and comparable to that of 6 phr conventional ZnO. Thus, it suggested that the synthesized nano ZnO could replace the convention ZnO as an activator for rubber vulcanization even at a lower amount.

Zinc Complexes with 1,3-Diketones as Activators for Sulfur Vulcanization of Styrene-Butadiene Elastomer Filled with Carbon Black

Zinc oxide nanoparticles (N-ZnO) and zinc complexes with 1,3-diketones of different structures were applied instead of microsized zinc oxide (M-ZnO) to activate the sulfur vulcanization of styrene-butadiene rubber (SBR). The influence of vulcanization activators on the cure characteristics of rubber compounds, as well as crosslink density and functional properties of SBR vulcanizates, such as tensile properties, hardness, damping behavior, thermal stability and resistance to thermo-oxidative aging was explored. Applying N-ZnO allowed to reduce the content of zinc by 40% compared to M-ZnO without detrimental influence on the cure characteristic and performance of SBR composites. The activity of zinc complexes in vulcanization seems to strongly depend on their structure, i.e., availability of zinc to react with curatives. The lower the steric hindrance of the substituents and thus the better the availability of zinc ions, the greater was the activity of the zinc complex and consequently the higher the crosslink density of the vulcanizates. Zinc complexes had no detrimental effect on the time and temperature of SBR vulcanization. Despite lower crosslink density, most vulcanizates with zinc complexes demonstrated similar or improved functional properties in comparison with SBR containing M-ZnO. Most importantly, zinc complexes allowed the content of zinc in SBR compounds to be reduced by approximately 90% compared to M-ZnO.

Optimization of physical and mechanical properties of glycerol - modified natural rubber/starch - filled carbon black composites using two level factorial design

A statistical model was developed in this study to describe cure characteristic, rebound resilience and tensile strength of natural rubber/starch composites which was prepared by using a Haake internal mixer. Response surface methodology (RSM) based on central composite centered design (CCD) was employed to statistically evaluate and optimize the conditions for maximum cure characteristic, rebound resilience and tensile strength and study the significance and interaction of carbon black and glycerol on rebound resilience and tensile strength yield. The experimental runs were carried out according to a 22 full factorial design for the two identified design independent variables, namely, carbon black (X1) and glycerol (X2). With the use of the developed quadratic model equation, a maximum rebound resilience 71% was obtained to be a carbon black loading of 50 phr and glycerol loading of 7 %.

The Blending of EPDM/NR with Maleic Anhydride as Compatibilizer: Comparing the Effect of Accelerators on Cure Characteristic and Mechanical Properties

The blending of ethylene propylene diene monomer/natural rubber (EPDM/NR) needs much attention because of their incompatibility. In this work, the influence of accelerator type on cure characteristics and mechanical properties of 60/40 EPDM/NR blend was investigated. The compounds were prepared by controlling the migration of curative and using maleic anhydride as the compatibilizer. Three types of accelerators were studied: 2,2-dithiobis(benzothiazole) (MBTS), the combination of MBTS and tetramethyl thiuram disulfide (TMTD), and n-tert-butyl-2-benzothiazolesulfenamide (TBBS). The cure characteristic, mechanical properties, and morphology of the composites had been investigated by rheometer, tensile testing machine, hardness durometer and scanning electron microscope (SEM). Blending of EPDM/NR with various accelerator gave different composite characteristics. MBTS, used in single or binary accelerator system, provided good mechanical properties. TBBS gave the longest scorch time, the lowest crosslink density and poor mechanical properties, except tear strength. Binary accelerator, MBTS/TMTD, provided the lowest processing time and the highest cure rate, but not significantly different from MBTS. Binary accelerator gives the best aging resistance and compatibility blend. These results correspond well with SEM micrograph. From the study, it can be concluded that binary accelerator system was the proper accelerator for EPDM/NR blend.

Preparation and Charaterization of Treated BIS [3-(Triethoxysilyl) Propyl] Tetrasulfide (Si-69) -HYBRID CB/PCC Fillers Reinforced NR/SBR Composites: Cure Characteristic, Mooney Viscosity and Cross-Link Density

Hybridization of silanized CB/PCC filler reinforced NR/SBR blends was prepared on a two roll mill. The si-CB/PCC composites were vulcanized via a conventional sulphur system at 180°C. The primary aims of this research are to scrutinize the effects of different concentration of si treated hybrid CB/PCC fillers ranging from 2 wt. % to 10 wt. % on the NR/SBR blends properties towards the curing characteristics, viscosity and crosslink density. In this work, a positive correlation was found between silane content on the hybrid filler surface and NR/SBR blend properties. It was found that at 6% of Si 69 concentration (F4) provided improvement in crosslink density and mooney viscosity properties. Increment of crosslink density in the blends would increase the viscosity and it may be due to the network formation between the treated fillers and rubber molecules. Moreover, the incorporation of treated fillers accelerates the curing process due to the surface activation and hence leads to tightly contact between filler-rubber phases.

Low-molecular-weight styrene–butadiene copolymers (L-SSBR) as processing aids used for silica-filled rubber: Synthesis, functionalization and application

Three different types of low-molecular-weight solution styrene-butadiene rubbers (L-SSBRs) were synthesized by anionic polymerization. Two of them were end-capped with methoxy (M-L-SSBR) and ethoxy (E-L-SSBR) functional groups, respectively, while the other was terminated with alcohol (L-SSBR). The content of functional groups was estimated on the basis of gel permeation chromatography and proton nuclear magnetic resonance analysis. The influence of L-SSBR on the properties of silica-filled SSBR as an alternative for the plasticizing oil was investigated in tyre tread formulation. L-SSBRs of high vinyl content were used in place of part of oil for preparation of compound K1 enriched with linear (L-SSBR) and compound K2 and K3 enriched with two star-like liquid rubbers modified, respectively, with methoxy (M-L-SSBR) and ethoxy (E-L-SSBR) functional groups. Although particular attention was paid to the effect of polar groups on the silica dispersions, cure characteristic, compound viscosity and mechanical properties were also analyzed. Rubber with only treated distillate aromatic extract was used (K5) as the reference.