Characterisation of shrinkage in oriented PET films and containers by thermomechanical analysis (TMA)

Effect of crystallinity on the recovery rate of superhydrophobicity in plasma-nanostructured polymers

This study explored the optimum conditions to achieve superhydrophobicity in polyethylene terephthalate (PET) in terms of crystallinity and microstructure. Surface superhydrophobicity was achieved by nanostructures induced by oxygen plasma etching and the recovery process of low surface energy through thermal aging of various PETs; semi-crystalline biaxial PET (B-PET) film, amorphous PET (A-PET) film, and semi-crystalline PET (F-PET) fabric. Under the anisotropic plasma etching, the nanostructures on the B-PET film were the longest, followed by the F-PET fabric, which developed a hierarchical micro/nanostructure, then the A-PET film. During thermal aging at 80 °C near T_g, the plasma-treated A-PET film recovered its superhydrophobicity within 3 h, while the plasma-treated B-PET film did not exhibit superhydrophobicity. At 130 °C, higher than T_g, the plasma-treated B-PET film recovered its superhydrophobicity within 1 h, but the plasma-treated A-PET film became opaque as its nanostructures deformed, decreasing its superhydrophobicity. The plasma-treated F-PET fabric exhibited faster recovery and greater superhydrophobicity than the plasma-treated B-PET film, due to its hierarchical micro/nanostructure. In addition, hydrophobic recovery during thermal aging was proved with a decrease in surface polar groups, lowering the surface energy using XPS analysis. Therefore, by designing the ratio of crystal to amorphous regions and surface micro/nanostructures, one can rapidly fabricate superhydrophobic PETs without additional surface finishing.

This study investigates the influence of molecular properties as well as the macroscopic structure on surface properties.

Development of PLA/EVA Reactive Blends for Heat-Shrinkable Film

Heat-shrinkable films have widely been used for various applications such as shrinkable labels and cap seals. These plastics have generally a short life. The biodegradable polymers can thus be an ideal candidate for such applications. This work aimed to study the stretching and shrinking ratio of poly(lactic acid)/ethylene vinyl acetate through reactive blends system for heat-shrinkable films application. The reactive agents, Joncryl^® and Perkadox were used as in situ compatibilizers. PLA/EVA with 100/0, 97/3, 95/5, 93/7, and 90/10 ratios were prepared in the twin screw extruder. Neat PLA and PLA/EVA films were fabricated by blown film extrusion. The results revealed that the elongation at break of PLA in the TD direction was improved when adding EVA. PLA and EVA film with 0.1 phr of Perkadox was found to be sufficient as evident by FESEM micrograph and DMTA results. The films were stretched and shrunk at a temperature of 70 °C. The percentage of shrinkage of the stretched PLA/EVA reactive blend films, two and three times were, 100%, approximately. On the other hand, the four-times stretched films shrunk less than 100% because of the excessive stretching, which resulted in film breakage and defect.