Natural rubber (NR) vulcanizates exhibit good mechanical properties compared to vulcanizates of synthetic rubbers. Incorporation of a conventional filler at higher loadings to NR enhances its modulus, while reduction in tensile strength and elongation. This paper presents a new strategy for development of a NR‐clay nanocomposite with enhanced mechanical properties by incorporation of lower loadings (2–8 phr) of cetyl trimethyl ammonium bromide modified montmorillonite clay (OMMT‐C) under acid‐free environment. The effect of OMMT‐C loading on cure characteristics, rubber‐filler interactions, crosslink density, dynamic mechanical thermal properties, and mechanical properties were evaluated. Incorporation of OMMT‐C accelerated the vulcanization process and enhanced mechanical properties. X‐ray diffraction analysis and scanning electron microscopy images revealed that the formation of intercalated clay structures at lower OMMT‐C loadings, and clay aggregates at higher loadings. A nanocomposite at OMMT‐C loading of 2 phr exhibited the best balanced mechanical properties, and was associated with highest crosslink density and rubber–filler interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46502.

Natural rubber (NR) latex-clay nanocomposite (NRLCN) synthesized with montmorillonite (MMT) clay aqueous dispersion was evaluated for reinforcement and barrier properties. The physio-mechanical properties of the NRLCN were compared with the conventional NR latex composites containing CaCO 3. The NRLCN structure was characterized with X-ray diffraction and scanning electron microscope techniques. The X-ray diffraction data showed that, with a lower concentration of clay, a highly exfoliated clay structure was achieved whilst the clay aggregation gradually resulted in a higher concentration of clay. The crosslink density as computed based on the solvent absorption data of the latex nanocomposite films was increased with the increase of clay concentration. As a result of nanoscale dispersion of the montmorillonite clay and higher crosslink density of the latex nanocomposite films, the resistance to permeation of small molecules through the NRLCN was significantly enhanced in comparison to conventional NR latex-CaCO 3 composites. Solid state mechanical properties of NRLCNs showed a significant reinforcement effect of dispersed clay platelets but without significantly reducing the elastic properties. The higher mechanical properties and improved barrier resistance indicated that NR latex nanocomposites containing montmorillonite clay is a potential replacement for conventional NR latex composites containing CaCO 3 .

A macromolecular coupling agent containing hydrophilic and hydrophobic groups is made to react with precipitated silica. Interfacial interactions between OH groups of silica and COOH groups of macromolecule are found to be created through either hydrogen bonds alone or through hydrogen bonds and covalent bonds. Aqueous dispersions of unmodified and modified silica are prepared and the colloidal stability and particle size distribution of the dispersions are observed. The dispersions at neutral pH are incorporated into vulcanized/unvulcanized natural rubber latex. The formation of hydrogen bonds and/or covalent bonds is studied via FTIR spectroscopy and their contribution in encouraging filler‐rubber interactions is emphasized through mechanical and swelling properties. Uniform distribution and dispersion of modified filler particles throughout the rubber matrix is confirmed by the microstructures of the latex films cast from filler added natural rubber latex. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40380.

In this study the applicability of pressure retarded osmosis power generation was investigated in order to fulfil current electricity demand in Sir Lanka. Pressure retarded osmosis (PRO) process is a renewable and green technology with zero carbon emission to the environment. Salinity gradient through a membrane is the key parameter in osmotic pressure development. Theoretically it is a pressure increment of 26 bar which is equivalent to 270 m high water column for fixed volume of salt water compartment. This hydrostatic pressure can be used to generate electricity by sending pressurized water through a turbine. According to the literature, 1 MW electricity generation requires 1m 3 /s flow of fresh water. Sri Lanka has a great potential to develop this technology as it is surrounded by sea. Subsequently the country is having 103 number of water rich river basins over the country. Currently the electricity demand of the entire country is about 2100MW and it is already being supplied by both hydro and thermal power plant. The country spends an immense amount of money for the thermal power generation in every year. This can be reduced by introducing PRO power generation. Calculations over the PRO power generation reveal that it is possible to generate 7.84% of country energy requirement via some selected river basins through this technology.

Ground Tyre Rubber (GTR) from scrap automotive and truck tyres was blended with Waste Polypropylene (WPP) from injection moulded products to prepare GTR/WPP blends. The blends were prepared in a Haake Rheocord PolyLab System, operating at 180 0 C and 30 rpm for 8 minutes. The degree of crystallinity of the WPP in the GTR/WPP blend was found to be unchanged up to a GTR level of 60 % by weight. Crystalline melting point and re-crystallization temperature showed a significant decrease with GTR content. Optical micrograph of the blends containing up to 60 wt% GTR showed a similar morphology, in which the GTR was dispersed in a continuous WPP phase. The GTR dispersed phase grew in size with GTR content until at 70 wt%, it changed to a continuous phase. However, all blends showed a mixture of cohesive, adhesive and ductile failures. The response to tensile loading ranged from a ductile plastic response with WPP-rich blends to a high extension-rubbery response with GTR-rich blends. Under impact loads, brittle fracture occurred in blends containing up to 40 wt% GTR, with ductile fracture thereafter. Hardness, tensile strength, secant modulus at 7% strain and tear resistance decreased with increase in GTR content, while % elongation at break and impact failure energy increased.

AbstractIn 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.

Ground tyre rubber (GTR) was blended with waste polypropylene (WPP) in nine different compositions to prepare GTR/WPP blends. The blends were prepared in a Haake Rheocord PolyLab system at a temperature of 180 °C and a rotor speed of 30 r/min for 8 min. The processing characteristics of the blends showed an increase in steady-state mixing torque with an increase in GTR content, suggesting an increased diffi culty in processability at GTR loadings above 30 wt.%. Morphological observations of the blends showed two-phase systems. The GTR was dispersed in a continuous WPP matrix in blends containing up to 60 wt.% GTR, and the size of the dispersed GTR agglomerants increased with GTR content. At 70 wt.%, the GTR dispersed phase changed to a continuous phase. Tensile strength, modulus, and tear resistance decreased with GTR content, while the elongation at break and the impact failure energy increased. All these properties remained relatively unchanged at low GTR contents, suggesting that a critical GTR level is required to obtain rubber-like properties in a simple rubber-thermoplastic blend.

An outstanding interest on elimination of nitrosamine generation in traditional sulfur vulcanization systems has led to introduce nitrosamine safe accelerator/s to produce safe natural rubber (NR) vulcanizates. It is an effective way to prevent formation of carcinogenic N-nitroso compounds during manufacture of rubber products. In the present study, behavior of nitrosamine safe binary accelerator system consisting of diisopropyl xanthogen polysulfide (DIXP) with commonly used non-regulated accelerator N-tert-butyl-2-benzothiazole sulfenamide (TBBS) was investigated in efficient sulfur vulcanization of NR. Cure characteristics, physico-mechanical properties and crosslink density of vulcanizates prepared with different combinations of the accelerator system were evaluated and compared with those of individual accelerators. The study reveals that moduli and strength properties of the vulcanizate prepared with DIXP accelerator are inferior to those of the vulcanizate prepared with TBBS accelerator. Nevertheless, optimum cure time of the DIXP compounds is lower in comparison to TBBS compounds. Moreover, progressive replacement of DIXP with TBBS in the accelerator system showed a synergistic effect in regard to cure characteristics and physico-mechanical properties.