Abstract
Natural rubber latex foam (NRLF) was reinforced with micro- and nanofibrillated cellulose at a loading content of 5–20 parts per hundred of rubber (phr) via the Dunlop process. Cellulose powder from eucalyptus pulp and bacterial cellulose (BC) was used as a microcellulose (MC) and nanocellulose (NC) reinforcing agent, respectively. NRLF, NRLF-MC, and NRLF-NC exhibited interconnected macroporous structures with a high porosity and a low-density. The composite foams contained pores with sizes in a range of 10–500 µm. As compared to MC, NC had a better dispersion inside the NRLF matrix and showed a higher adhesion to the NRLF matrix, resulting in a greater reinforcement. The most increased tensile strengths for MC and NC incorporated NRLF were found to be 0.43 MPa (1.4-fold increase) and 0.73 MPa (2.4-fold increase), respectively, by reinforcing NRLF with 5 phr MC and 15 phr NC, whereas the elongation at break was slightly reduced. Compression testing showed that the recovery percentage was improved to 34.9% (1.3-fold increase) by reinforcement with 15 phr NC, whereas no significant improvement in the recovery percentage was observed with MC. Both NRLF-MC and NRLF-NC presented hydrophobic surfaces and good thermal stability up to 300 °C. Due to their highly porous structure, after a prolong immersion in water, NRLF composites had high water uptake abilities. According to their properties, the composite foams could be further modified for use as green absorption or supporting materials.
Highlights
Cellular rubber, or natural rubber latex foam (NRLF), has long been considered as an economical material with advantageous properties, such as light weight, buoyancy, cushioning performance, thermal and acoustic insulation, inertness, high porosity, robust micro/nanostructures and good aging properties [1,2]
The particle size of NC powder was considerably larger than the diameter of bacterial nanocellulose (BC) fiber, which could be due to the agglomeration of BC fibers during the drying nanocellulose (BC) fiber, which could be due to the agglomeration of BC fibers during the drying process
modulus at 100% elongation (M100) were obtained by reinforcing NRLF with NC at 15 phr, which were 1.7 and 2.0 times, respectively, To compare reinforcing efficiency between MC and NC, the highest values of tensile strength the maximum values obtained from reinforcing NRLF with MC
Summary
Natural rubber latex foam (NRLF), has long been considered as an economical material with advantageous properties, such as light weight, buoyancy, cushioning performance, thermal and acoustic insulation, inertness, high porosity, robust micro/nanostructures and good aging properties [1,2]. The Dunlop process is a main NRLF manufacturing method invented by E.A. Murphy in the late 1920s for manufacturing latex from the sap of rubber trees. Murphy in the late 1920s for manufacturing latex from the sap of rubber trees In this process, natural rubber latex (NRL) is compounded with vulcanizing agents and whipped into froth by an assistance of a foaming agent. A delayed-action gelling agent such as sodium silicofluoride (SSF) is added into the fluid foam and subsequently injected into a mold. The fluid foam is allowed to be gelled into solid foam at ambient temperature and baked in a vulcanization oven. After the foam is baked, it is removed from the mold, washed, and heated a second time to remove moisture from the final product.
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