Sarawut Prasertsri

Role of Hydroxyl-Terminated Polybutadiene in Changing Properties of EPDM/ENR Blends

In this research, the effect of hydroxyl-terminated polybutadiene (HTPB) on processability, mechanical properties, thermal aging and oil resistance of 80/20 ethylene-propylene diene rubber/epoxidized natural rubber (EPDM/ENR) blend was investigated. The amount of HTPB used was varied from 0-4 parts per hundred of rubber (phr). The results revealed that addition of HTPB into EPDM/ENR blend decreased the compound viscosity, while scorch time and cure time slightly increased with increasing HTPB content. Furthermore, hardness, tensile and tear strengths of the blend decreased due to the poor dispersion of fillers in the presence of HTPB. After thermal aging treatment, the crosslink density of all EPDM/ENR blends increased leading to increasing in 100% modulus, tensile strength and swelling resistance, as well as reducing in elongation at break. However, it had additional plus features that high resilience with low compression set was achieved in the blend containing 2 phr of HTPB.

Comparison of Reinforcing Efficiency between Calcium Carbonate/Carbon Black and Calcium Carbonate/Silica Hybrid Filled Natural Rubber Composites

The present research aimed to develop natural rubber (NR) hybrid composites reinforced with calcium carbonate/carbon black (CC/CB) and calcium carbonate/silica (CC/SC). The influence of CC/CB and CC/SC with various filler ratios (120/0, 90/5, 60/10, 30/15 and 0/20) on cure characteristics and mechanical properties of the vulcanizates was investigated and their reinforcing efficiency was compared. It has been found that incorporation of CB in the hybrid filler decreases the scorch time and cure time but increases crosslink density, whereas the incorporation of silica showed cure retardation. As CB or SC content increases, stiffness, tensile strength and tear strength increase, while elongation at break and compression set decrease. Scanning electron microscopy studies also reveal poor filler dispersion and poor adhesion between filler particles and matrix in the vulcanizates with increasing in CC content in a weight filler ratio which causes inferior mechanical properties. Incorporation of CB or SC content enhanced the mechanical properties of the vulcanizates, where CC/CB hybrid system exhibited higher reinforcing efficiency compared with CC/SC hybrid system.

Influence of Accelerator/Sulfur Ratio on Mechanical Properties and Thermal Resistance of Natural Rubber Containing Hybrid Fillers

This research investigated the effect of accelerator/sulfur (ACC/S) ratio on mechanical properties and thermal resistance of natural rubber composites containing hybrid fillers. Two hybrid systems of 10/60 carbon black/calcium carbonate (CB/CC) and silica/calcium carbonate (SC/CC) in NR composites were focused and the different ACC/S ratios were 0.40, 0.56, 0.64 and 0.88. The results indicated that the crosslink density, hardness and tear strength of NR vulcanizates increased with increasing ACC/S ratio, whereas compression set decreased. However, tensile strength increased with increasing ACC/S ratio up to 0.64 and then it decreased when the ACC/S ratio is further increased. In addition, the vulcanizates with high ACC/S ratio, which mainly contained monosulfidic and disulfidic linkages, exhibited a greater thermal ageing resistance than that with low ACC/S ratio which contained polysulfidic linkage. Comparing in two hybrid filler systems, the reinforcement performance of CB/CC hybrid-filled is significantly higher for all ACC/S ratios investigated.

Influence of Pyrolytic Carbon Black Prepared from Waste Tires on Mechanical Properties of Natural Rubber Vulcanizates

This research aimed to investigate the possibility of pyrolytic carbon black (PCB) used as filler in natural rubber (NR) and its effect on Mooney viscosity, cure characteristics and mechanical properties compared with commercial carbon black (N774). The results revealed that Mooney viscosity, stiffness and heat build-up tended to increase with increasing both PCB and N774 loading, whereas elongation at break decreased. However, the maximum tensile and tear strengths appeared at the optimum filler loading for both PCB and N774. At similar filler content, PCB-filled NR compounds have higher cure time, heat build-up and thermal resistance. Nevertheless, they exhibited lower Mooney viscosity and mechanical properties compared to N774-filled NR. Finally, it can be concluded that PCB could be utilized as filler in NR compound to act as semi-reinforcing filler and was classified as a filler to reduce costs.

Characterization of Snap-On Calf Nipple Product and Development of its Compound Formulation Based on Natural Rubber

This research aimed to develop the formulation of natural rubber filled with carbon black, silica and calcium carbonate for rubber calf nipple application. The reverse engineering was performed on the calf nipple product to analyze the rubber type and component by using Soxhlet extraction, thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) techniques. Furthermore, mechanical properties were examined to act as benchmark for the rubber compound design. The results showed that rubber component in the nipple product was natural rubber, whereas two filler types revealed as carbon black and calcium carbonate with 10 and 35 of the total weight. In addition, rubber nipple showed the hardness of 46±1 Shore A and tensile strength of 5.3±0.60 MPa. From the investigation of the properties of developed rubber compounds in this work, it was found that the mechanical properties depended on type and content of filler. The required mechanical properties of vulcanizates were achieved at 20 phr of carbon black (N330), 20 phr of silica and 120 phr of calcium carbonate.

Compatibilization Efficiency of Polybutadiene-Grafted Maleic Anhydride in Ethylene-Propylene Diene Rubber/Epoxidized Natural Rubber Blends

This research aims to investigate the efficiency of polybutadiene-grafted maleic anhydride (PB-g-MAH) as the compatibilizer for ethylene-propylene diene rubber and epoxidized natural rubber (EPDM/ENR) blends. PB-g-MAH was varied from 0-10 parts per hundred parts of rubber (phr), and the cure characteristics, mechanical and dynamic properties of 70/30 EPDM/ENR blends with and without compatibilizer were evaluated. It was found that the minimum torque, maximum torque, scorch and cure times of the blends increased after adding PB-g-MAH, whereas cure rate decreased. The morphology of the blend is improved by the addition of PB-g-MAH in small amounts, owing to an improved compatibility of these rubbers confirmed by dynamic mechanical property. The hardness and oil resistance increased with increasing PB-g-MAH content. Of all blends investigated, the blend compatibilized with 2-4 phr of PB-g-MAH shows the optimum mechanical properties and thermal resistance.