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The composite films of sago starch were prepared by incorporation of various amount of kaolinite (K) and kaolinite intercalated by dimethyl sulfoxide (DMSO) (KD) via solution blending method in order to reduce the water vapor transmission and enhance mechanical properties of starch based films. The kaolinite intercalation by DMSO and the composite films were characterized by using X‐ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscope techniques. The result showed that well‐dispersed kaolinite layers were delaminated in the starch matrix attesting to intercalate and exfoliate composite films. The effect of kaolinite content on the water vapor transmission and tensile properties of the composite films was investigated. The water vapor transmission of the starch film (neat starch film ca. 0.132 g.cm3/h) decreased with the addition of K and KD to the starch. It was also observed that the maximum tensile strength (5.18 MPa) was attained for the composite film with 4% by weight of clay content. The improvement in the tensile strength and modulus of starch‐based composites was due to the strong interfacial interaction between matrix and kaolinite clay, correlating to the change of morphology of the starch composite films as revealed by scanning electron microscopy.

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Bentonite clay was used as a reinforcing and compatibilizing filler for natural rubber/polystyrene (NR/PS) blend via latex blending process. The reinforcing and compatibilizing performance of bentonite clay in the NR/PS blends were evaluated. The improvement of the mechanical properties of NR/PS blends with the weight ratios of 90/10, 80/20, and 70/30 was found with the addition of 3 and 5 parts per hundred rubber (phr) clay. The characterization by using Fourier transform infrared spectroscopy and X‐ray diffraction (XRD) gave the evidence that the silicate layer was intercalated by NR and PS molecular chains. The morphology of tensile fracture surface by scanning electron microscope showed the separated phase boundaries of PS and NR blend and gradual disappearance with the bentonite content. This could be implied that the bentonite contributes to the compatibilization between PS and NR. The compatibilization action of the bentonite clay was also reflected by the shift of glass transition temperature (Tg) of NR to higher temperatures than those of the blends. These results suggested that the tensile and tear properties of the blends were controlled by compatibility between NR and PS. The most enhanced properties of blends were found with the addition of 3 phr bentonite clay. POLYM. ENG. SCI., 54:1436–1443, 2014. © 2013 Society of Plastics Engineers