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. 2020 Aug 29;12(9):1959.
doi: 10.3390/polym12091959.

Natural Rubber Latex Foam Reinforced with Micro- and Nanofibrillated Cellulose via Dunlop Method

Sirilak Phomrak  1 , Adun Nimpaiboon  2 , Bi-Min Zhang Newby  3 , Muenduen Phisalaphong  1
Affiliations

Natural Rubber Latex Foam Reinforced with Micro- and Nanofibrillated Cellulose via Dunlop Method

Sirilak Phomrak et al. Polymers (Basel). .

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.

Keywords: Dunlop method; microcellulose; nanocellulose; natural rubber latex foam; reinforcement.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
SEM images of microcellulose fibers from eucalyptus pulp (a) and nanocellulose fibers from BC (b).
Figure 2
Figure 2
XRD patterns of microcellulose (MC) and nanocellulose (NC) powders.
Figure 3
Figure 3
SEM images of surfaces (bottom and top) and cross section views of NRLF composites.
Figure 4
Figure 4
Foam densities of NRLF, NRLF-MC and NRLF-NC.
Figure 5
Figure 5
Crosslink density as a function of (a) cellulose loading content and (b) degree of swelling in toluene. The filled triangles and open circles are for NRLF-NCs and NRLF-MCs, respectively.
Figure 6
Figure 6
Mechanical properties: (a) tensile strength, (b) M100 and (c) elongation at break of NRLF, NRLF-MC and NRLF-NC.
Figure 7
Figure 7
Recovery (%) from the compression test of NRLF, NRLF-MC and NRLF-NC.
Figure 8
Figure 8
Water contact angle on the bottom and top surfaces of NRLF, NRLF-MC and NRLF-NC.
Figure 9
Figure 9
Water uptakes of NRLF, NRLF-MC and NRLF-NC.
Figure 10
Figure 10
TGA (a) and DTG (b) curves for the degradation of NRLF, MC, NC, NRLF-MC and NRLF-NC.
Figure 10
Figure 10
TGA (a) and DTG (b) curves for the degradation of NRLF, MC, NC, NRLF-MC and NRLF-NC.
See this image and copyright information in PMC

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