New approach for preparation of dry natural rubber nanocomposites through acid-free co-coagulation: Effect of organoclay content

Microstructure and Lamellae Phase of Raw Natural Rubber via Spontaneous Coagulation Assisted by Sugars

Natural rubber (NR) as a renewable biopolymer is often produced by acid coagulation of fresh natural latex collected from Hevea brasiliensis. However, this traditional process is facing a huge economic and environmental challenge. Compared with the acid coagulation, spontaneous or microorganism coagulation is an ecofriendly way to obtain NR with excellent performance. To clarify the influence of different sugars on NR quality, several sugars were used to assist the coagulation process. Influence of different sugars on microstructure and cold crystallization were examined by ¹H NMR, DSC, etc. The results indicated that sugars exhibit different biological activity on terminal components of fresh field latex and can influence the resultant molecular structure and basic properties. Brown sugar exhibits higher metabolic activity and is inclined to decompose the protein and phospholipids crosslinking compared with other sugars. The larger molecular weight of sugar molecule is beneficial for the formation of the stable α lamellae phase and higher overall degree of crystallization.

Enhancement of mechanical properties of natural rubber–clay nanocomposites through incorporation of silanated organoclay into natural rubber latex

In this study, cetyl trimethyl ammonium bromide (CTAB) modified montmorillonite (MMT) which is called as organoclay (OMMT) was mixed with natural rubber, and masterbatches were produced using the acid-free co-coagulation (AFCC) method in the presence of a combined gelling agent, a mixture of CTAB and sodium dodecyl sulfate. The OMMT was further modified by grafting of bis(triethoxysilylpropyl)tetrasulfide as to reduce the surface energy in silanated organoclay (OMMT-S). As expected, the nanocomposites prepared with OMMT-S compared to those with OMMT exhibited greater mechanical properties due to the development of rubber–clay interactions and due to proper dispersion of small clay layers in the rubber matrix combined with the gelling agent. The improvement of elongation at break, hardness and tear strength of the nanocomposites with OMMT/OMMT-S was an added advantage when the nanocomposites are prepared using the AFCC method without having any adverse effect from the combined gelling agent.