Reinforcement of natural rubber using silica and zeolite mixed fillers
No Thumbnail Available
Date
2015
Journal Title
Journal ISSN
Volume Title
Publisher
Uva Wellassa University of Sri Lanka
Abstract
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).
Description
Keywords
Mineral Sciences, Materials Sciences, Mineral Resource, Science and Technology, Rubber Technology