Growing global awareness of environmental issues has led to increased research interest in starch-based foams as a biodegradable packaging material. However, limitations such as low foaming ratio and poor water resistance hinder their development and industrial application. This study aimed to address these challenges by investigating the effect of the polyvinyl alcohol (PVA) content and hydrolysis degree on foam properties, providing insight into the intricate interplay between melt viscoelasticity and foam characteristics. The results demonstrated that the foaming behaviors, viscoelastic properties, thermal stabilities and mechanical performances of the foams were significantly improved with increasing hydrolysis degrees of PVA. These enhancements were attributed to hydrogen bonding interactions and intermolecular entanglements between starch and PVA chains. Additionally, the incorporation of PVA resulted in a remarkable reduction in the water absorption capacity (WAC) of the foams. Specifically, the foam containing 20% PVA with a hydrolysis degree of 98% exhibited the lowest WAC of 7.46% at 75% RH, the lowest bulk density of 12.42 kg/m 3 , the highest foaming ratio of 54.66, and the highest porosity of 99.39%. These properties were equivalent to those of commercially available expanded polystyrene (EPS). Furthermore, the addition of 20% PVA yielded the highest compressive strength of 110.58 MPa and the highest recovery of 92.75%, indicating great potential for diverse cushioning applications. Overall, this work highlights the significant potential for wider application of starch-based foams in large-scale industrial settings.
Lei Wang,Dong Li,Yaoting Xue,Siyang Li,Xuxu Yang,Li Li,Tiefeng Li,Zisheng Luo
Mechanical damage during transportation impairs fruit quality. Protecting fragile fruits through packaging is essential. Herein, this paper presents a case study of fresh strawberries embeded in porous hydrogels (PHs) to maintain quality and avoid damage during shelf-life period. The hydrogels were biologically fabricated using alginate networks and soy protein isolates to yield a porous structure. With three times of foaming rate, the PH could dissipate 70%–78% deformation energy in the first loading cycles. It also maintained an energy dissipation rate of 51.52% after 200 loading cycles. The strawberries stored in these PHs exhibited a remarkably better quality than those in other package materials after transportation simulation and free-fall tests, their damage indices were inhibited under 14% (above 36% in control). Additionally, during a two-day shelf-life period, rotten rate of strawberries after transportation simulation and that after free-fall tests were detected as 2.49 ± 1.86% (48.33 ± 5.67% in control) and 13.34 ± 3.76% (94.96 ± 3.76% in control), respectively. Moreover, PHs possessed a high specific heat capacity of 3956 ± 49 J kg −1 K −1 and a low friction coefficient of 0.081 ± 0.003, maintaining a low temperature around the fruit and avoiding fruit abrasion. The PHs were also biodegradable. Therefore, the PHs was considered as promising packaging for maintaining fresh and fragile produce.
危险品化学品经营许可证（带存储）