Review article
Sustainable development of natural rubber and its environmentally friendly composites

https://doi.org/10.1016/j.cogsc.2021.100446Get rights and content

Natural rubber (NR) is well known as renewable biobased polymer that has been widely used in a wide variety of applications ranging from ordinary household to aerospace products. To meet the complete concept of green growth and sustainable development, the uses of nontoxic chemicals and green fillers alternating to conventional fillers are necessary to be concerned. In this article, we provide up-to-date information on the sustainable development of NR including NR latex production with low ammonia/nonammonia system and the usage of effective curing activator and biobased processing oil. Moreover, the issue of the environmentally friendly green NR composites is described here with using renewable biomass organic fillers derived from plants and animals such as cellulose and chitin.

Introduction

Natural rubber (NR) has been used in human life since 1600 BC. It is made from a milky white liquid called latex oozing from certain plants. There are more than 2500 types of tree that produce the sap, but commercially over 99 percent of the latex for rubber production is derived from the Hevea brasiliensis tree, or the aptly named rubber tree. Over the years, many synthetic rubbers have been successfully polymerized. Although these man-made petroleum sourced rubbers have innumerable advantages, their disadvantages are no less such as having low mechanical strength and release of carbon dioxide during their production, thus seriously leading the world to global warming. To overcome this, recently many attempts try to enhance the consumption of NR. However, to achieve sustainable development it is necessary to consider the drawbacks of NR in the whole supply chain and address the drawbacks. This article combines a range of issues that contribute to NRs and their environmentally friendly composites as green rubber technology [1].

Section snippets

Low ammonia/nonammonia system for NR latex preservation

NR latex can be obtained by tapping the rubber tree. About 35–40 %w/w of field NR latex is the solid part, whereas the rest is the aqueous part. The solid component consists not only of the rubber part having linear cis 1,4-polyisoprene in the form of separately spherical particles but also nonrubber parts including mainly carbohydrates, proteins, and lipids in an aqueous serum phase. Generally, the rubber particles are stabilized in the aqueous phase due to the adsorbed proteins and

Effective ZnO-based curing activator

ZnO acts as an activator for the accelerated sulfur vulcanization. In fact, the one that reacts with the accelerator is Zn2+. According to European Council Directive 2004/73/EC, the reduction and elimination of zinc level in the environment has become an important task because of its toxic effect on aquatic organisms. The release of zinc from the rubber product into the environment can happen in several different ways. The vast majority of cases are from wearing off of automotive tires.

Biobased processing oil

NR having very high molecular weight becomes highly viscous during a melt mixing process. Moreover, to achieve the satisfaction in the mechanical properties, a large amount of filler such as carbon black/or silica is usually compounded, leading to an increase of the viscosity of the NR. To loosen the viscosity, one approach is the addition of processing aids. Practically, the commercial processing aids are petroleum-based oils including paraffinic, naphthenic, and aromatic oils. The most

Environmentally friendly green natural rubber composites

NR has attractive properties of toughness, high impact, and tear strength, high resilience, low hysteresis, and good formation [28]. However, in the rubber industries, fillers (especially reinforcing fillers) are necessarily used to achieve the appropriate characteristics for a variety of the commercial applications. As such reinforcing fillers, nonrenewable inorganic minerals such as CB, silica, calcium carbonate, and clay are known as the conventional reinforcing fillers in NR processing [29,

Conclusion

Despite the emergence of various synthetic rubbers, NR still gains much attention from the rubber industry because of issues on environmentally friendly material, sustainable resource, and some excellent properties. This article summarizes the several meaningful solutions to achieve the sustainable development of green NR technology, including the harmless and potential preservative system for the NR latex, effective ZnO activator for sulfur vulcanization, biobased processing aids, and

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors would like to thank CEP-GAICCE, Faculty of Science, Chulalongkorn University for financial support.

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