Browsing by Author "Dilhan, L. W. S."

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    Reinforcement of natural rubber using silica and zeolite mixed fillers
    (Uva Wellassa University of Sri Lanka, 2015) Dilhan, L. W. S.; Rathnayake, R. M. M. D.; Jayasuriya, C.K.
    Among the main ingredients added in the compounding process of Natural Rubber (NR), fillers play a major role. The purpose of adding fillers into the rubber matrix is 2-fold: to reduce the production cost or to give reinforcement. (Blackley, 1997). A reinforcing filler would increase the mechanical properties such as tensile strength, elongation at break, and tear resistance of the rubber vulcanizate. Increasing the area of contact between rubber matrix and filler particles, and increasing the degree of bonding between the two phases seem to be the most important factors in providing the strong reinforcement effect (Treloar, 2005). The current research is focused on a combination of two fillers, namely silica and zeolite, to provide a reinforcing effect on NR. Silica is in general widely used for reinforcement of NR. On the other hand, zeolites were considered due to their unique porous structure which would enhance the area of contact between the phases. Methodology Materials Double Centrifuged Natural Rubber Latex (DCL) with 60% dry rubber content (stabilized with ammonia) provided by Dipped Product Industries in Sri Lanka was used in the preparation of the samples. Mineral samples, Silica and Zeolite were purchased from Glorchem, Colombo. The agent, Zincmercaptobenzothiozole (ZMBT), Zincdiethyldithiocarbamate (ZDDC), Diphenylguanidine (DPG), etc) were of commercial grades. Procedure The samples were prepared using NR latex compound formulation used for glove manufacture. The mineral samples were ground using “TEMA mill” and were sieved to get the particle sizes in the range of (45 – 60) µm. A stabilized natural rubber was obtained by adding potassium laurate (20%) and KOH (10%, 2.50 g) to natural rubber latex (60%, 167 mL). ZnO (1.00 g), Zincdiethyldithiocarbamate (0.20 g), Zincmercaptobenzothiozole (1.00 g), Diphenylguanidine (1.20 g), antioxidant (1.50 g), dispersing agent (0.20 g) and Sulphur (1.40 g) were ground together using a mortar and a pestle. The ground mixture was dissolved in distilled water (8.30 mL) using a magnetic stirrer to obtain the dispersion. The stabilized NR solution and the dispersion were mixed together and distilled water was added to dilute the total dry rubber content of the solution up to 40%. This sample was labelled as “NR” and was used as the control sample. The amount of mineral needed to make up 1%, 2%, 3%, 4% and 5% of the final weight of the sample was calculated and added to the dispersion. In this research, two series of samples were prepared: first series was prepared by adding silica as the mineral and was labeled “Sil” and the second series was prepared by adding a 1:1 mixture of Silica and Zeolite as the mineral and was labeled “Mix”. Calculated amounts of sieved minerals were added to both series. The solutions (NR, Sil and Mix) were then filtered and poured into small glass tanks, covered and left overnight to dry. The samples were then cured for 3.5 min at 120 °C using the hot box oven (Gallencamp). The entire procedure was triplicated. The mechanical property analysis was based on tensile and tear strength. The samples with optimum mineral percentages showing the best tensile and tear properties were subjected to the structure determination by Fourier Transformed Infrared (FTIR) analysis and thermal properties by thermogravimetric analysis (TGA).