Study of the Annealing Effect of Starch/Polyvinyl Alcohol Films Crosslinked with Glutaraldehyde

Effects of PVA and yerba mate extract on extruded films of carboxymethyl cassava starch/PVA blends for antioxidant and mechanically resistant food packaging

Global concerns over environmental damage caused by non-biodegradable single-use packaging have sparked interest in developing biomaterials. The food packaging industry is a major contributor to non-degradable plastic waste. This study investigates the impact of incorporating different concentrations of polyvinyl alcohol (PVA) and yerba mate extract as a natural antioxidant into carboxymethyl cassava starch films to possibly use as active degradable packaging to enhance food shelf life. Films with starch and PVA blends (SP) at different ratios (SP radios of 100:0, 90:10, 80:20 and 70:30) with and without yerba mate extract (Y) were successfully produced through extrusion and thermoforming. The incorporation of up to 20 wt% PVA improved starch extrusion processing and enhanced film transparency. PVA played a crucial role in improving the hydrophobicity, tensile strength and flexibility of the starch films but led to a slight deceleration in their degradation in compost. In contrast, yerba mate extract contributed to better compost degradation of the blend films. Additionally, it provided antioxidant activity, particularly in hydrophilic and lipophilic food simulants, suggesting its potential to extend the shelf life of food products. Starch-PVA blend films with yerba mate extract emerged as a promising alternative for mechanically resistant and active food packaging.

Multivapor-Responsive Controlled Actuation of Starch-Based Soft Actuators

Multivapor-responsive biocompatible soft actuators have immense potential for applications in soft robotics and medical technology. We report fast, fully reversible, and multivapor-responsive controlled actuation of a pure cassava-starch-based film. Notably, this starch-based actuator sustains its actuated state for over 60 min with a continuous supply of water vapor. The durability of the film and repeatability of the actuation performance have been established upon subjecting the film to more than 1400 actuation cycles in the presence of water vapor. The starch-based actuators exhibit intriguing antagonistic actuation characteristics when exposed to different solvent vapors. In particular, they bend upward in response to water vapor and downward when exposed to ethanol vapor. This fascinating behavior opens up new possibilities for controlling the magnitude and direction of actuation by manipulating the ratio of water to ethanol in the binary solution. Additionally, the control of the bending axis of the starch-based actuator, when exposed to water vapor, is achieved by imprinting-orientated patterns on the surface of the starch film. The effect of microstructure, postsynthesis annealing, and pH of the starch solution on the actuation performance of the starch film is studied in detail. Our starch-based actuator can lift 10 times its own weight upon exposure to ethanol vapor. It can generate force ∼4.2 mN upon exposure to water vapor. To illustrate the vast potential of our cassava-starch-based actuators, we have showcased various proof-of-concept applications, ranging from biomimicry to crawling robots, locomotion near perspiring human skin, bidirectional electric switches, ventilation in the presence of toxic vapors, and smart lifting systems. These applications significantly broaden the practical uses of these starch-based actuators in the field of soft robotics.

Autoclave process parameters affecting mechanical and thermomechanical properties of CFRP laminates using response surface methodology

Autoclave curing is a manufacturing process for high-performance parts based on carbon fiber–reinforced polymers (CFRPs) used for large aircraft parts. Today, this manufacturing process is the reference in terms of quality and, therefore, the manufactured parts’ mechanical performance and robustness. However, several parameters can impact the quality of the parts resulting from this process, which requires optimizing key manufacturing parameters. In this study, the effect of autoclave process parameters (i.e., temperature, pressure, and vacuum-pressure) on the glass transition temperature (Tg), laminate compressive modulus (LCM), laminate compressive strength (LCS), and interlaminar shear strength (ILSS) was investigated using three factors, three-level Box–Behnken design (BBD) and response surface methodology (RSM). In addition, the interactions of processing parameters with Tg, LCM, LCS, and ILSS were investigated, making this study an essential investigation for accurately selecting processing parameters. Thus, there is a functionally non-linear relationship between the interaction of the autoclave process parameters. Therefore, these parameters were optimized using RSM with the maximum Tg, LCM, LCS, and ILSS. The optimization and validation of the obtained models were carried out with an average relative error below 3% for all thermomechanical and mechanical properties, indicating that the BBD and optimization were correct. Because of this, the established regression models can accurately predict the Tg, LCM, LCS, and ILSS in autoclaved epoxy/carbon composite laminates.