Green Natural Rubber Composites Reinforced with Black/White Rice Husk Ashes: Effects of Reinforcing Agent on Film's Mechanical and Dielectric Properties.

Praewpakun Sintharm,Muenduen Phisalaphong

doi:10.3390/polym13060882

Abstract

Green natural rubber (NR) composites reinforced with black rice husk ash (BRHA)/white rice husk ash (WRHA), using alginate as a thickening and dispersing agent and crosslinking by CaCl2, was developed to improve mechanical, chemical and dielectric properties of NR-based films by using a latex aqueous microdispersion process. A maximum of 100 per hundred rubbers (phr) of rice husk ashes (RHAs) could be integrated in NR matrix without phase separation. Mechanical properties of the composite films were considerably enhanced, compared to the neat NR film. The composite films reinforced with WRHA demonstrated relatively better mechanical properties than those reinforced with BRHA, whereas the composites filled with BRHA demonstrated higher elongation at break. The crosslinking by CaCl2 improved the film tensile strength but lowered the film elasticity. The reinforcement strongly improved chemical resistance of the composite films in toluene. The films are biodegradable in soil, with weight loss of 7.6–18.3% of the initial dry weight after 3 months. Dielectric constant and dielectric loss factors of the composite films were enhanced with RHAs loading. According to the obtained properties, the composites offer potential for further development as stretchable conductive substrate or semiconducting polymer films for electronic applications.

Highlights

In recent years, biopolymers have attracted considerable interest for their potential to reduce consumption of fossil resources and nonbiodegradable polymers in order to reduce plastic pollution
The present study demonstrates that the t1e2nosfi2le0 strength of uncured natural rubber (NR) composites increases with increasing black rice husk ash (BRHA) and white rice husk ash (WRHA) loading, and that the maximum tensile strength was obtained at BRHA/WRHA loading of 100 psthrer.nTghthe wreassuoltbstianidneicdataet tBhRaHt tAhe/WlatReHx aAquloeaoduisngmoicfr1o0d0isppherr.sTiohne prerosuceltsssiwnditihcadteistpheartstinhge alagteenxtaiqsuseuoituasblme ifcorrocdoismpperossiioten pprreopcaersastiwonithtodaiscphieervsienhgoamgoengteniseosuusitadbislepefrosriocnomofpRosHitAe pfirlleeprasriantiNonRtomaacthriixe.vSeohdoimumogaelngeionuastediisspseuristaiobnleoffoRrHthAe fiulsleerassina NdiRspmerastirnixg. aSgoedniut min atlhgiissnyasteteims s,ubiteacbaluesfeoritthceaunseimasparodvisepeRrHsinAg adgisepnetrisniothnisasnydstermed,ubceecafuilsleerit-fciallneriminptreorvaectRioHnAs
BRHA/WRHA-filled uncured NR composites were successfully prepared via a latex aqueous microdispersion process with the use of sodium alginate as a dispersing agent

Summary

Introduction

Biopolymers have attracted considerable interest for their potential to reduce consumption of fossil resources and nonbiodegradable polymers in order to reduce plastic pollution. Recent research has focused on improving properties of biopolymer composites, including starch-based materials, cellulose-derived polymers, bacterial polyesters and natural rubber composites. The NR prices have been unstable for several years, because of oversupply from major rubber producing countries, a weak global economy and cheaper synthetic rubbers for replacement natural rubber [3]. NR often has its chemical structure modified by a vulcanization process and reinforced by adding fillers to improve its properties [5]. Carbon black and silica are synthetic fillers that are commonly used as reinforcing fillers in the rubber industry Both carbon black and silica are added into an NR matrix in order to improve the mechanical and thermal properties of NR composites. The major problem of this type of reinforcement is the poor dispersion and agglomeration of fillers in the NR matrix, which limits the loading content of fillers

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Conclusion