Characterization of Environmentally Friendly Polymers by Inverse Gas Chromatography: I Amylopectin

Amylopectin, as a potato starch based polymer, with a molecular weight of six million gram/mol was characterized using the Inverse Gas Chromatography Method (IGC). DSC method was also used to measure the glass and melting temperatures. Both DSC and IGC agreed well on a T_g of 105°C and T_m of 160–166°C. Nineteen solutes (solvents) were injected onto a chromatographic column containing amylopectin. These solutes revealed the interaction of alkanes with AP, and the wettability and water intake of AP. Alkanes showed exothermic values of interaction parameters which were increased as the temperature increased and as the number of carbons in the alkane series decreased. Retention diagrams of these solutes in a temperature range of 80–200°C revealed two zones, crystalline and amorphous. T_g and T_m were measured using these zones which complimented the DSC values. The two zones were used to calculate the degree of crystallinity below the melting temperature which ranged from 85% at 104°C to 0% at 161°C. The dispersive component of the surface energy of amylopectin was measured using alkanes which ranged from 25.35 mJ/m² at 80°C to 8.47 mJ/m² at 200°C. This is attributed to the weak crystalline surface of AP at 80°C and when the surface melted at 160°C the surface energy decreased due to the thermal expansion of the surface.