Natural rubber nanocomposites barrier properties

The barrier properties of starch nanocrystals/natural rubber nanocomposites were also investigated [39]. For these systems, the water vapour transmission rate, the diffusion coefficient of oxygen, the permeability coefficient of oxygen and its solubility, were measured. It was observed that the permeabiUty to water vapour, as well as to oxygen, decreased when starch nanocrystals wctc added These effects were ascribed to the platelet-like morphology of the nanocrystals. 

H.N. Azlina, H.A. Sahrim, R. Rozaidi, R. Bahri, Y. Yamamoto, S. Kawahara, Oxygen barrier properties of new thermoplastic natural rubber nanocomposites. Polymer - Plastics Technology and Engineering 50 (15) (2011) 1564—1569. 

Bras, J., Hassan, M.L., Bruzesse, C., Hassan, E.A., El-Wakil, N.A., Dufresne, A., 2010. Mechanical, barrier, and biodegradability properties of bagasse cellulose whiskers reinforced natural rubber nanocomposites. Industrial Crops and Products 32, 627—633. 

Meera, A., Thomas P, S., Thomas, S. Effect of organoclay on the gas barrier properties of natural rubber nanocomposites. Polymer Composites. 2012, 33, 524-531. Majeed, K., Jawaid, M., Hassan, A., AbuBakar, A.,Abdul Khalil, H. P. S., Salema, A. A., Inuwa, I. Potential materials for food packaging from nanoclay/natural fibers filled hybrid composites. Mater Design. 2013,46, 391 10. 

The Nielsen model has been a popular theory, originally used to explain polymer lay nanocomposites. This model is used to describe the tortuosity effect of plate-like particulates of filled rubber polymer composite on the gas permeation. An increase in barrier properties of gas permeation of rubber polymer nanocomposites is a result of the impermeable nature of filler particles which creates a long path of penetrant molecule by directing them around the particle. 

J. Ok Jo, P. Saha, N.G. Kim, C.H. Choi, J.K. Kim, Development of nanocomposite with epoxidized natural rubber and functionalized multiwalled carbon nanotubes for enhanced thermal conductivity and gas barrier property. Materials Design, ISSN 0264-1275 83 (October 15, 2015) 777-785. http //dx.doi.Org/10.1016/j.matdes.2015.06.045. 

The improvement in thermal stability of the nanocomposites compared to the neat EVA/natural rubber is due to the barrier effect and insulating properties of organoclay. The well dispersed plate-like silicate layers form a tortuous path in the polymer matrix which gives a barrier effect and inhibits the diffusion of volatile degradation product from the inside of the polymer matrix. Moreover the well-dispersed silicate layers restrict the movement of polymeric chains, hence reducing the free volume for diffusion of volatile degradation products. Other researchers also confirm that organoclay tends to form a compact char-like residue on the surface of the nanocomposites when it is burnt. This char-like structure is incombustible and acts as an insulator which inhibits heat transfer to the inside of the nanocomposites. At 8 phr... 

Natural rubber (NR)-rectorite nanocomposite was prepared by co-coagulating NR latex and rectorite aqueous suspension. The TEM and XRD were employed to characterize the microstructure of the nanocomposite. The results showed that the nanocomposite exhibited a higher glass transition temperature, lower tan d peak value, and slightly broader glass transition region compared with pure NR. The gas barrier properties of the NR-rectorite nanocomposites were remarkably improved by the introduction of nano scale rectorite because of the increased tortuosity of the diffusive path for a penetrant molecule. The nanocomposites have a unique stress-strain behavior due to the reinforcement and the hindrance of rectorite layers to the tensile crystallization of NR [36]. 

Compared to the vast literature on most of the thermoplastic or thermosetting polymer-clay nanocomposites, reports of rubber-clay nanocomposites are much more limited. Much more research is needed to understand the complex nature of these nanocomposites and to identify the factors that have the most significant influence on their physical, mechanical, thermal, barrier, and dynamic mechanical properties. The several examples of rubber-clay nanocomposite that have been covered in this chapter indicate that to date rubber nanocomposite research has largely concentrated on the natural rubber, ethylene propylene diene rubber, styrene-butadiene rubber, and nitrile rubbers. The main factors found to influence final properties were type of clay and its treatment, clay... 

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