Evaluation of thermal insulation and mechanical properties of waste rubber/natural rubber composite

Abstract

The influences of waste rubber loading on mechanical and thermal conductivity properties were investigated for NR composite. An experimental investigation was carried out to obtain low cost construction material with desirable mechanical and thermal insulation properties. Natural rubber was loaded with different concentrations of waste rubber (200, 400, 600, 800, and 1000) phr. The addition of waste rubber leads to a slight increase in thermal conductivity values of composites but it still lies around range of thermal insulating materials. Also addition of waste rubber leads to improvement of mechanical properties of composites. The crosslink density of NR composite increases with the increase of waste rubber loading until 600 phr and after that it decreases due to the stronger the rubber–filler interaction. This leads to the decrease of the swelling index that has the opposite trend of crosslink density. So, the sample with 600 phr waste rubber is considered the optimum concentration from the swelling measurement. Filler loading results in pronounced increase in the tensile modulus and decease in the elongation at fracture which reflects the reinforcement effect of the filler. The yield stress increases with waste rubber loading increment. This delays the permanent disruption of matrix morphology. So, the optimum concentration which is 600 phr waste rubber loading agrees with the swelling and mechanical measurements which has desirable thermal insulation and high mechanical properties and decreases the cost of materials to 82% of the NR cost.