Investigation of the thermal properties of Sayote (Sechium edule) fiber loaded starch/PVOH composite blends

The thermal properties of starch/PVOH formulations gelatinized with glycerol, cross-linked with boric acid, incorporated with clay and loaded with 2 wt%, 4 wt%, and 7 wt% sayote fibers were investigated. The FTIR spectra, SEM micrographs, DSC, and TGA results revealed a successful blending in starch/PVOH (50/50) and starch/PVOH (65/35) fomulations with glycerol as plasticizer and boric acid as cross-linking agent. Plasticized and cross-linked starch/PVOH reinforced with clay and varying amounts of sayote fiber suggest more inter- and intra- molecular hydrogen bonding interactions, making the composite more crystalline and thermally stable. The SEM micrographs showed a smoother surface with the addition of boric acid and a more orderly woven surface with 2 wt% sayote fiber loading. DSC thermograms reveal that the formulations were compatible and had good blending interactions, since the experimental enthalpies of melting were higher than their theoretical values. The addition of sayote fiber increased the thermal stability of starch/PVOH composite blends and prevented the re-crystallization of starch. TGA curves showed that the addition of sayote fibers formed stronger blends that delayed the degradation of the composite. The starch/PVOH (50/50) and starch/PVOH (65/35) composite blends were more crystalline and thermally stable at 2 wt% to 4 wt% sayote fiber loading.