Mixture design to develop biodegradable sheets with high levels of starch and polyvinyl alcohol

Abstract

A mixture design was used to analyse the effects of polyvinyl alcohol (PVA) on glycerolplasticised cassava starch sheets obtained by flat extrusion from a twin-screw extruder. PVA was the main component that improved the properties of the sheets, and glycerol presented the opposite effect. The properties ranging: tensile strength (0.22-1.5 MPa), Young's modulus (0.45-7.29 MPa), elongation at break (59-111%), puncture resistance (10-107 N/mm), puncture elongation (5.64-10.13 mm), crystallinity index (17-21%) and water vapour permeability (3.39-7.40 Â 10 À5 g m À1 day À1 kPa À1 ) for the sheets. Scanning electron microscopy showed good compatibility between the components of the blend because the resultant materials were continuous and cohesive and did not exhibit phase separation. The sheets were not significantly different from others, based on XRD and FTIR analyses, consistent with the literature. PVA was able to improve the mechanical and barrier properties of starch-based sheets.

Polyvinyl alcohol (PVA) molecular weight and extrusion temperature in starch/PVA biodegradable sheets

“…The biodegradables sheets of all formulations presented similar diffractograms (Figure 3), with a sharp peak at 19.9°, and an overlapped peaks at 17.7° and 23.5°, similar to observed by Zanela et al [8] , and a diffraction peak at 40.6°. Das et al [21] produced starch:PVA film and they attributed the 19.6° peak to the ordered arrangement of PVA chains in the material, and the 17.7° peak was attributed to plasticized starch, but this peak had little intensity, and it was overlapped by the peak at 19.9°.…”

“…The PVA used by the authors was similar to S540, and the tensile strength was higher, and the elongation was lower than those obtained in this study. These differences can be attributed to the PVA concentration in the films, because according to Zanela et al [8] the concentration of PVA was the main factor for increasing the tensile strength, elongation at break and Young modulus of cassava starch/PVA biodegradable sheets.…”

“…Zanela et al [8] obtained WVP values ranging from 3.0 to 8.56 x10 -10 g.m -1 .s -1 .kPa -1 for cassava starch/PVA (S203) sheets using glycerol as plasticizer and PVA ranging from 7.5 to 22.5 wt%. The authors observed that glycerol was the main factor for WVP increasing due to its plasticizer properties.…”

“…Zanela et al [8] produced extruded sheets based on different proportions of starch, PVA and glycerol through a mixture design. The authors observed that all formulations were homogeneous, without visible cracks by SEM, demonstrating a good miscibility between both polymers, and with the increasing, the level of PVA present in the blends, the mechanical and barrier properties of the sheets were increased.…”

Synergism Effect of Surfactant and Inorganic Salt on the Properties of Starch/Poly(Vinyl Alcohol) Film

“…Moreover, PVA was a synthetic biodegradable polymer. Starch/PVA films have been widely studied for their potential applications in packaging and agricultural areas …”