Temperature memory effect and its stability revealed via differential scanning calorimetry in ethylene-vinyl acetate within glass transition range

Utilization of By-Products from Livestock: Study on the Mechanical and Thermal Properties of Biodegradable Containers Made with Pork Skin Gelatin Polymer

This study aimed to develop a biodegradable container made of pork gelatin. Gelatin was extracted from pork skin by hot water at 80 °C, and containers were prepared by adding eggshell powder (20%) as a pore agent, and walnut powder (0.08 wt%; PEW1, 0.14 wt%; PEW2) to improve hardness. The blends were molded for each experiment and dried at 30 °C for 24 h, at 40 °C for 16 h, and at 121 °C for 16 h. The containers were analyzed with respect to morphological (SEM; scanning electron microscope), mechanical (tensile strain and stress), and thermal (DSA; differential scanning calorimetry and TGA; thermogravimetric analysis) properties, as well as biodegradability. SEM investigation showed a smoother surface for PEW1 than for PEW2. The tensile stress of PEW2 (37.86 MPa) was significantly higher than that of PEW1 (28.40 MPa), and the melting enthalpies were 137.60 J/g (PEW1) and 309.60 J/g (PEW2). TGA showed similar properties, but PEW2 contained more lignin; therefore, its decomposition temperature was higher. The PEW1 and PEW2 containers were completely biodegraded after approximately 7 and 11 weeks, respectively. Walnut shell powder increased the hardness, but slowed the biodegradation process. The applications of this biodegradable container are short-lived products such as food packaging.

Heating/Solvent Responsive Shape-Memory Polymers for Implant Biomedical Devices in Minimally Invasive Surgery: Current Status and Challenge

This review is about the fundamentals and practical issues in applying both heating and solvent responsive shape memory polymers (SMPs) for implant biomedical devices via minimally invasive surgery. After revealing the general requirements in the design of biomedical devices based on SMPs and the fundamentals for the shape-memory effect in SMPs, the underlying mechanisms, characterization methods, and several representative biomedical applications, including vascular stents, tissue scaffolds, occlusion devices, drug delivery systems, and the current R&D status of them, are discussed. The new opportunities arising from emerging technologies, such as 3D printing, and new materials, such as vitrimer, are also highlighted. Finally, the major challenge that limits the practical clinical applications of SMPs at present is addressed.

A Brief Review of the Shape Memory Phenomena in Polymers and Their Typical Sensor Applications

In this brief review, an introduction of the underlying mechanisms for the shape memory effect (SME) and various shape memory phenomena in polymers is presented first. After that, a summary of typical applications in sensors based on either heating or wetting activated shape recovery using largely commercial engineering polymers, which are programmed by means of in-plane pre-deformation (load applied in the length/width direction) or out-of-plane pre-deformation (load applied in the thickness direction), is presented. As demonstrated by a number of examples, many low-cost engineering polymers are well suited to, for instance, anti-counterfeit and over-heating/wetting monitoring applications via visual sensation and/or tactual sensation, and many existing technologies and products (e.g., holography, 3D printing, nano-imprinting, electro-spinning, lenticular lens, Fresnel lens, QR/bar code, Moiré pattern, FRID, structural coloring, etc.) can be integrated with the shape memory feature.