An improved hybrid process for natural rubber foam manufacture combining the Dunlop/Blowing/Talalay methods

Abstract

The Dunlop method is well-known for preparing natural rubber foams (NRFs). However, the Talalay method is an alternative that provides a comparably softer and more flexible end product. The current research investigated several hybrid methods for preparing NRFs, Dunlop (DL), Dunlop/Blowing (DB), Dunlop/Talalay (DT), and Dunlop/Blowing/Talalay (DBT). Small- and wide-angle X-ray scattering analysis was utilized to investigate the nano- and macro-scale structures which indicated slight changes in the arrangement of the NR chains from the different methods. Additionally, scanning electron microscopy and X-ray micro-computed tomography were used to study the morphology of the NRFs to understand their mechanical properties better. Notably, the mechanical properties of the DBT samples in the static and dynamic modes were better than NRFs made with the other methods. We hypothesize this is due to the small bubbles in the porous structure of the DBT samples that fused into larger bubbles during the blowing process, leading to a high matrix phase of the NR and a greater foam density. This research proposes an improved hybrid process to prepare NRFs using a combination of the Dunlop, Blowing, and Talalay methods. The DBT sample had 50% better compressive strength (26.1 KPa) and 40% better energy dissipation (2.5 of tan δ) compared to the DL sample (17.8 KPa and 1.8 of tan δ). Moreover, the DBT sample had 132% better compressive strength and 26% higher energy dissipation compared to the DT sample (11.3 KPa and 1.9 of tan δ), making it suitable for use in NR products.