Biodegradable pressure sensitive adhesives produced from vital wheat gluten: Effect of glycerol as plasticizer

Effect of temperature and humidity on mechanical properties and constitutive modeling of pressure-sensitive adhesives

Pressure-sensitive adhesives (PSAs) are crucial for the structural and functional integrity of flexible displays. Investigating the intricate mechanical properties of PSAs can help enhance product quality and performance. This study conducts systematic mechanical tests, including uniaxial tensile, compression, planar shear, and stress relaxation, on PSAs at temperatures ranging from - 25 to 85 ℃ and relative humidity levels from 0 to 90%. Our findings reveal that the Anssari-Benam model accurately describes the hyperelastic behavior of PSA materials under large deformation, outperforming the Ogden model by requiring fewer parameters and better preserving convexity. Moreover the results show that temperature markedly affects PSA properties, particularly near the glass transition temperature (Tg), with lower temperatures leading to decreased elasticity and higher temperatures aiding in stress relaxation. Similarly, humidity impacts PSA behavior, increasing elasticity and decreasing stiffness, especially noticeable in stress relaxation tests. These findings highlight the substantial influence of environmental conditions on the material properties of PSAs and underscore the necessity of understanding both hyperelastic and viscoelastic responses for their application in flexible technologies. This research provides critical insights for the optimal utilization of PSAs in the rapidly evolving field of flexible electronics, including OLED displays.

Biodegradable Fiber-Reinforced Gluten Biocomposites for Replacement of Fossil-Based Plastics

Biocomposites based on wheat gluten and reinforced with carbon fibers were produced in line with the strive to replace fossil-based plastics with microplastic-free alternatives with competing mechanical properties. The materials were first extruded/compounded and then successfully injection molded, making the setup adequate for the current industrial processing of composite plastics. Furthermore, the materials were manufactured at very low extrusion and injection temperatures (70 and 140 °C, respectively), saving energy compared to the compounding of commodity plastics. The sole addition of 10 vol % fibers increased yield strength and stiffness by a factor of 2-4 with good adhesion to the protein. The biocomposites were also shown to be biodegradable, lixiviating into innocuous molecules for nature, which is the next step in the development of sustainable bioplastics. The results show that an industrial protein coproduct reinforced with strong fibers can be processed using common plastic processing techniques. The enhanced mechanical performance of the reinforced protein-based matrix herein also contributes to research addressing the production of safe materials with properties matching those of traditional fossil-based plastics.

Effects of polyols with different hydroxyl numbers on the structure and properties of starch straws

To study the relationship between the number of hydroxyl groups of polyols and the plasticizing effect, the effects of different polyols including ethylene glycol, glycerol, erythritol, xylitol and sorbitol on the structure and properties of corn starch straws were analyzed and compared. The results showed that the addition of plasticizer significantly improved the performance of starch straws, which greatly improved the mechanical properties, water absorption rate (WAR) and thermal stability. However, there was no linear relationship between the plasticizing effect on starch straws and the number of hydroxyl groups in plasticizers. Fourier transform infrared (FTIR) results showed that erythritol formed the strongest intermolecular interaction with starch. Starch straws with erythritol (S-ERY) had the highest bending force (Fb = 25.78 N) and the lowest WAR. Starch straws with glycerol (S-GLY) showed the lowest relative crystallinity (RC = 12.87 %) and the highest temperature of the maximum degradation (Tdmax = 302.1 °C). In addition, after storing for 180 days, S-GLY showed higher modulus of elasticity in bending (Eb = 4.26 N/cm) and a uniform surface.

Liquid and Pressure-Sensitive Adhesives Based on Cassava Starch and Gelatin Capsule Residue: Green Alternatives for the Packaging Industry

Natural polymer-based adhesives are green alternatives, necessary to reduce the problems impacted by synthetic adhesives. Starch and gelatin have extraordinary potential for the synthesis of biobased adhesives. Citric acid (CA), a natural acid, induces the crosslinking and hydrolyzing of both gelatin and starch. In this sense, this work deals with the use of gelatin capsule residues as a promising material to produce biobased adhesives in combination with cassava starch in the presence of different CA concentrations characterizing their mechanical, physicochemical and microstructural properties. Depending on CA concentration, formulations adjusted to different applications can be obtained such as liquid and pressure-sensitive adhesive films. The inclusion of CA allows us not only to improve the applicability of the system since it modifies the flowability of the adhesives as evidenced by the observed changes in the viscosity (from 158.3 to 90.3 for formulations with 20 and 80% CA, respectively). In addition, mechanical profiles showed that the inclusion of CA increased the adhesive bond strength (from 2230.7 to 2638.7 for formulations with 20 and 80% CA, respectively). Structural modifications induced by CA in adhesive formulations were highlighted by ATR-FTIR analysis.

Fabrication and evaluation of vitamin doped Zno/AgNPs nanocomposite based wheat gluten films: a promising findings for burn wound treatment

Burn wound treatment remains a significant issue in wound care management especially when multidrug resistant bacterial infection and accumulation are present. Delayed wound healing is mostly due to ineffectiveness of commercially available wound dressings that protects the wound but less efficient in healing perspective. Therefore, nano-based wound dressing might be efficient solution for wound healing management. The present study reports the fabrication and evaluation of zinc oxide (ZnO) or silver nanoparticles (Ag NPs) capped with vitamin A or E nanocomposite that were incorporated in wheat gluten (WG) films. The chemical structure, phase purity, and morphological features confirmed the successful coating of NPs by vitamins A and E and their interaction with WG during film casting. The maximum swelling response was observed by NPs vitamin composite WG films than control films while slow release of vitamins and NPs from films was observed up to 24 h. WG films either carrying ZnO or Ag NPs, and vitamin A or E demonstrated significant antioxidant and antibacterial potential. The NPs-vitamin composite loaded WG films showed wound contraction within 14 days during in vivo burn wound healing experiments on mice model. The rates of wound healing, re-epithelialization, collagen deposition with fibroblast regeneration, adipocytes, and hair follicle development were observed through visual and histopathological examination. The study reveals that vitamin A or E doped ZnO or Ag NPs fabricated in WG can be efficiently used against burn wounds due to their physiochemical and biological properties. Furthermore the biocompatible nature and biodegradable potential make the films more prone to mankind maneuver for initial protection and healing remedy.

Versatile wheat gluten: functional properties and application in the food-related industry

Gluten is a key component that allows wheat flour to form a dough, and it is also a byproduct of the production of wheat starch. As a commercial product, wheat gluten is increasingly used in the food-related industry because of its versatile functional properties and wide range of sources. Wheat gluten is manufactured industrially on a large scale through the Martin process and batter process and variants thereof. Gliadin and glutenin impart cohesiveness and elasticity properties, respectively, to wheat gluten. The formation of gluten networks and polymers depends mainly on covalent bonds (disulfide bonds) and noncovalent bonds (ionic bonds, hydrogen bonds, and hydrophobic interactions). The multifunctional properties (viscoelasticity, gelation, foamability, etc.) of wheat gluten are shown by rehydration and other processing techniques. Wheat gluten has been widely used in wheat-based products, food auxiliary agents, food packaging, encapsulation and release of food functional ingredients, food adsorption and heat insulation materials, special purpose foods, and versatile applications. In the future, wheat gluten protein will be used as an important raw material to participate in the development and preparation of various food and degradable materials, and the application potential of wheat gluten in food-related industries will be massive. This review summarizes the main manufacturing processes, composition, and structure of gluten protein, and the various functional properties that support its application in the food and related industries.

Fabrication of Conductive, Adhesive, and Stretchable Agarose-Based Hydrogels for a Wearable Biosensor

Herein, a strategy is proposed to prepare a conductive, self-adhesive, and stretchable agarose gel with the merits of distinct heat resistance, freeze resistance, and long-term moisture retention. To endow the gels with conductivity, monodisperse carbon nanotubes modified by polydopamine are introduced into the gel networks, which promote both conductivity and mechanical strength of the gels. Meanwhile, further addition of glycerol enhances excellent stretchability as well as heating/freezing tolerability and moisture retention of the gels. A wearable biosensor based on the gel is fabricated to record body motions precisely with good biocompatibility, which benefits the development of smart wearable devices.