Cassava starch composite based films for encapsulated neem: Effect of carboxylated styrene-butadiene rubber coating

The biocomposite was made from the blend of carboxylated styrene-butadiene rubber (CSBR), cassava starch (CS) and cellulose fiber (CF). Coating of the CSBR onto the CSBR/CS/CF biocomposites by immersion method which produced the CSBR-coated CSBR/CS/CF composites with improving the water resistance, moisture content, and moisture absorption. The contact angle of all CSBR coated CSBR/CS/CF composites was similar to 70 degrees and the swelling ratio of sample was similar to 10 % in water medium. The decrease of absorption might be due to the existence of the hydrophobic styrene butadiene rubber (SBR) in the CSBR molecular structure rending the more hydrophobicity to the coated CSBR/CS/CF composite surface. The thickness and percentage weight gain increased as a function of the dry rubber content (DRC) of the CSBR coating. SEM micrographs showed no phase separation between the CSBR/CS/CF composite and CSBR coating layer. However, the tensile value of coated composites decreased when compared with uncoated sample. Also, the highest CSBR coating content provided lowest in degree of contact angle value. This was might be probably due to existing of carboxyl groups in coating layer. These results provided information that the coating concentration was an important factor to the surface and bulk properties of the CSBR/CS/CF composites. After that, the CSBR coating CSBR/CS/CF composites were used to a matrix for encapsulated neem Aza A and results were accept for a good matrix for neem Aza A controlling release and photostability.