Hydrophilic plasticized biopolymers: Morphological influence on physical properties

Biopolymers such as amylose, when mixed with plasticizers have excellent potential in forming thin films for various food and packaging applications. In this study, the influences of moisture content, plasticizer type and content have been investigated on the physical tensile elongation and crystalline morphology of starch biopolymeric material. Biopolymeric samples prepared with starch and two types of plasticizer with different molecular weights, namely glycerol (Mwt = 92) and xylitol (Mwt = 152), were employed, which also have different numbers of hydroxyl (OH) groups (3 for glycerol and 5 for xylitol). A statistical design of experiments (DoE) was performed on the sample responses (i.e. tensile elongation and crystalline morphology) by varying the moisture content, plasticizer type as well as plasticizer content. Plasticizer type and degree of crystallinity have been found to be insignificantly related. However, the plasticizer content has shown a significant effect on both elongation and crystallinity. A clear B-type pattern (peak at 2θ = ∼ 20°) has been observed in most X-ray diffraction (XRD) results.