Abstract
The modification of achira starch a thermoplastic biopolymer is shown. Glycerol and sorbitol, common plasticizers, were used in the molten state with organic acids such as oleic acid and lactic acid obtaining thermodynamically more stable products. The proportion of starch:plasticizer was 70:30, and the acid agent was added in portions from 3%, 6%, and 9% by weight. These mixtures were obtained in a torque rheometer for 10 min at 130 °C. The lactic acid managed to efficiently promote the gelatinization process by increasing the available polar sites towards the surface of the material; as a result, there were lower values in the contact angle, these results were corroborated with the analysis performed by differential scanning calorimetry and X-ray diffraction. The results derived from oscillatory rheological analysis had a viscous behavior in the thermoplastic starch samples and with the presence of acids; this behavior favors the transitions from viscous to elastic. The mixture of sorbitol or glycerol with lactic acid promoted lower values of the loss module, the storage module, and the complex viscosity, which means lower residual energy in the transition of the viscous state to the elastic state; this allows the compounds to be scaled to conventional polymer transformation processes.
Highlights
Nowadays, the use of plastic materials derived from petroleum has generated a negative environmental impact [1,2]; from this reason was born the necessity to use polymers obtained from renewable sources as a great alternative as packaging materials in single-use products, due to their biodegradation or compostability [3,4]
Taking into account the above, it was set at a ratio of 70:30 and only organic acids were varied in order to know the effect on the rheological, surface, and thermal properties that organic acids can cause
The thermoplastic starch (TPS) O-9 mixture resulted in higher values, probably due to an insufficient interaction of oleic acid with the other components, which was visualized by migration of the acid in the final material
Summary
The use of plastic materials derived from petroleum has generated a negative environmental impact [1,2]; from this reason was born the necessity to use polymers obtained from renewable sources as a great alternative as packaging materials in single-use products, due to their biodegradation or compostability [3,4]. Bioplastics and Nova-Institute [5], the global production capacity of bio-based plastic packaging materials will increase by 2022 in 20% (2.45 million tons) [6,7]. Some biopolymers such as cellulose, poly (lactic acid), starch, chitosan, and poly (hydroxyalkanoates) have been modified aiming to develop barriers to various gases, moisture, and even microorganisms [8]. The achira is a plant widely cultivated in different countries of Latin America and Asia [23,24], and it has become a viable resource, mainly in Colombia where there are industrial of starch extraction plants, which has interesting physicochemical properties to develop plastic films [25]
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