Effect of glycerol on thermal and mechanical properties of polyvinyl alcohol/starch blends

Abstract

The paper reports the results of studies on the effect of glycerol content on thermal, mechanical, and dynamic mechanical properties of blends of starch and polyvinyl alcohol (PVA). Degree of crystallinity of the starch/ PVA blends (4 g/4 g ratio) remains almost constant up to 3.78 g of glycerol as determined by differential scanning calorimetry (DSC) and x-ray diffraction studies. At higher loading of glycerol the crystallinity decreases. DTG thermograms revealed occurring of one maximum degradation temperature closer to that of starch in blends containing up to 3.78 g of glycerol. At higher glycerol content there gradually occur two distinct peaks of maximum degradation temperature, one occurring close to that of starch and other occurring close to the PVA peak, indicating phase separation of the blend components. Results of stress-strain studies indicate lowering of tensile properties and energy at break particularly at higher glycerol content (beyond 3.78 g). Dynamic mechanical studies reveal a sharp drop in dynamic modulus at higher glycerol content at all temperatures. The blend with low glycerol content shows transitions of starch, while the blend containing high glycerol content beyond 3.78 g display the transitions due to both starch and PVA.

Preparation and characterization of LDPE/PVA blend films filled with glycerin‐plasticized polyvinyl alcohol

“…Glycerin exhibited characteristic absorption peaks of 3000–3600 cm −1 , which are caused by OH stretching and vibration. Furthermore, the absorption peaks at approximately 2875 and 2927 cm − 1 belong to the symmetric and stretching vibration of CH 2 , whereas the peaks at 1119 and 1030 cm − 1 are due to the wagging vibration of CH . Pure PVA exhibited characteristic absorption peaks at 2956, 2919, and 2852 cm − 1 , which are caused by the CH 2  asymmetric stretching vibration band.…”

Heterogeneity of laser‐irradiated films of polyvinyl alcohol/starch blends: effect of glycerol content

“…Accordingly, the difference in melting points of the non‐radiated and irradiated samples follow the order, SPG1 < SPG3 < SPG5. Earlier Sreekumar et al . reported that increasing amount of glycerol causes a decrease in the stress–strain properties and an increase in heterogeneous nature for the blends.…”

“…It is evident from the table that laser radiation causes an increase in ΔH cry , ΔH fus , T cry and T m of the blends. Incorporation of glycerol causes a decrease in crystallinity due to breakdown of intermolecular hydrogen bonds on plasticization . However, laser radiation leads to plasticizer removal and recovery of crystallinity of PVA.…”

Natural weather ageing of starch/polyvinyl alcohol blend: effect of glycerol content

“…Earlier, Sreekumar et al [25] reported that the thermal properties of the starch/PVA blend decreased with glycerol content. It is interesting to note that an increase in ageing time increases the Δ H fus , Δ H cry , T cry , and T m of the starch/PVA blend.…”