การผลิตโฟมยางธรรมชาติโดยใช้ไมโครบับเบิล

Abstract

Dunlop and Talalay are well-known methods for natural rubber latex foam production. In Thailand, Dunlop process is mainly used for the manufacture of thick- molded latex foam products such as pillows, cushions, and mattresses, while Talalay is not popular due to complicated and expensive method. Nevertheless, the products produced from Talalay technique show better flexibility and mechanical properties than Donlop products. This is because they have better cell structure and pore-size distribution as compared to the Dunlop ones. Microbubbles are widely used in many applications such as wastewater treatment, fish farming, and particle size separation. However, up to date, there is no application in the field of latex foam production. In this research, therefore, microbubbles are applied to fabricate natural rubber foams by flowing air through a porous diffuser with different flow rates. The effects of diffuser's pore size (P2, P3, P4) and air flow rate (20, 50, 100 ml/min) on microstructure and physical properties of the as-prepared rubber foams were investigated in comparison with those of the Dunlop foams. The results show that air microbubbles could be effectively used to fabricated natural latex foam with an exceptional microstructure of spherical cell shape with crack-free interconnected network structure. In contrast, Dunlop foams provided irregular cell shape with partially interconnected network and non-uniform cell size distribution. Pore size of the diffuser and the flow rate affected strongly cell size of the bubbled foams and hence physical properties of the foams. Large pore size of the diffuser led to a large cell size of the foam. Similarly, the cell size increased significantly with the increased air flow rate. Density of the bubbled foams decreased with the increased flow rates. The compression set percentage decreased with the decreased flow rate. The hardness index pointed out that all the bubbled foams produced were classified as a soft latex with a value of less than 100 newtons.