The analysis of materials using Fourier transform infrared (FTIR) spectroscopy has a unique area called the fingerprint region for each compound. However, this area is almost never discussed because of its complexity due to the large number of signals that appear in it. In this work, the fingerprint region analysis of the ethylene–vinyl acetate copolymer (EVA) with different percentages of vinyl acetate (VA) (18%, 28%, 40%) was performed. In comparison with other instrumental techniques, the crystallinity and structural arrangement of the EVA copolymers were determined simply and economically. The crystallinities for EVA18, EVA28 and EVA40 were 24.39%, 6.95% and1.03%, respectively. In terms of structural ordering, the number of linear chains of EVA copolymer decreases as the concentration of VA increases, which favors the reduction of degrees of freedom and the formation of hydrogen bonds.
The chemical modification of starch from physiologically immature bananas (Musa paradisiaca L.) was performed via the in situ polymerization of ϵ‐caprolactone (CL) utilizing ammonium decamolybdate as a catalyst to obtain a starch‐g‐PCL copolymer in one step. The copolymerization conditions were studied by varying the CL/catalyst mass ratio, the reaction temperature, and the reaction time. The final product was characterized using different technical instruments to demonstrate copolymerization. Based on the results, the graft copolymer was successfully synthesized, and the mass yield reached 85.2% at a temperature of 110°C with a DPn(NMR) of 10 and a Mn(NMR) of 1141 Da. The monomer conversion to copolymer followed a power‐law model with a reaction order of 3/2. The thermal properties and crystallinity of the starch and polycaprolactone in the copolymer were affected due to the formation of starch‐g‐PCL clusters.
The synthesis of the graft copolymer starch‐g‐PCL was carried out in a single phase, using molybdenum oxide as a catalyst, at a temperature of 150°C over a period of 24 h. Infrared spectroscopy and nuclear magnetic resonance analyses indicated that the graft copolymer was successfully synthesized, obtaining an 84% conversion yield. The introduction of ethylene glycol to the reaction influences the copolymer synthesis, affecting conversion yields and the physicochemical properties of the resultant copolymer. X‐ray diffraction analysis indicates that the copolymer crystallinity decreases as ethylene glycol concentration increases. An investigation of the thermal properties of the graft copolymer suggested that the decomposition temperature of the copolymer, compared to that of the homopolymer, decreases with exposure to ethylene glycol. Scanning electron microscopy revealed the formation of clusters between the starch granules and the grafted copolymer due to the interaction of the hydroxyl groups of the starch and PCL.
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