Effects of oil palm trunk biochar on the thermal stability and acoustic properties of specialty natural rubber latex foam

Specialty natural rubber (SpNR) latex foam is a natural-based acoustic foam material, that can substitute conventional synthetic foams to control noise pollution in buildings and in the transportation industry. However, the thermal stability of SpNR latex foam must be improved to meet the required safety criteria for buildings. The goal of the study is to investigate the feasibility of oil palm trunk biochar (OPTB) as a flame-retardant ingredient in two types of SpNR latex foam: deproteinized natural rubber latex foam and epoxidized natural rubber latex foam. The effects of different levels of OPTB loading (8 phr, 16 phr, and 24 phr) on the thermal stability and acoustic properties of OPTB/SpNR latex foam composites were examined. Thermogravimetric analysis indicates that the OPTB has excellent flame-retardant characteristics. The addition of OPTB to SpNR latex foam decreased the thermal decomposition rate of SpNR latex foam but was still insufficient to meet the building fire rating requirements. This study also found that the addition of OPTB to SpNR latex foam increased sound transmission loss but decreased the sound absorption coefficient values. Owing to the fact that OPTB is cheaper than SpNR latex, the addition of OPTB to SpNR latex foam could lead to cost savings in the production of the acoustic foam material. Additionally, this study contributes to sustainable material development by converting OPTB, a by-product from oil palm plantations into value-added products, which is in line with global environmental aspirations.