Effect of adding a reactive plasticizer on the mechanical,thermal, and morphology properties of nylon toughened wheat gluten materials

Blends of wheat gluten (WG) with up to 30% aliphatic nylon were prepared by mixing in 70% aqueous ethanol solution at 110 °C in a sealed reactor. After solvent removal and mechanical milling, rigid plaques were compression molded from the powdered blends. The microstructure of the molded plaques was studied via scanning electron microscopy. All compositions showed a phase separated morphology with seemingly poor compatibility between the two components. Up to 10% addition, the nylon was dispersed within the gluten matrix as discrete particles with an average diameter >10 μm. At higher nylon volume fractions there was evidence for the presence of gluten sub‐inclusions within the nylon phases. The dispersion of particles in a blend containing 10% nylon was improved and the particle size was decreased to roughly 5 μm by addition of an epoxy functionalized ethylene glycol oligomer. The additive simultaneously lowered the modulus of the WG matrix and appeared to improve the interfacial bonding between the gluten and the nylon. In cross‐sections of the ternary blends, fine filaments were observed spanning the gluten/nylon phases at the phase boundary. The compression molded plaques continued to exhibit brittle failure in mechanical bending tests characteristic of glassy gluten materials, however, the mechanical toughness was boosted to almost three times that of reference gluten plaques by the combined addition of the nylon and reactive plasticizer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45931.     

Dynamic mechanical analysis of the multiple glass transitions of plasticized wheat gluten biopolymer

Glass transition of thermo‐molded biomaterials made from wheat gluten and its main protein classes is studied by dynamic mechanical analysis (DMA). The materials are plasticized with variable contents of glycerol (30–40 wt %) and water (0–20 wt %). For all materials, three successive relaxation phases are systematically detected. Their positions shift to lower temperature as the plasticizer content of materials increases. Composition in gluten, glycerol and water of each relaxation phase is estimated using the Couchman‐Karasz model. Irrespective of the plasticizer content or composition, the relaxation phases shows rather constant plasticizer volume fractions. The low‐, middle‐, and high relaxation phases include respectively around 30, 60 and 80 vol % of gluten protein. These relaxations are assigned to the segmental motion of the surface amino‐acid side groups, to the collective motion of packed gluten proteins, and to the gain in protein conformational mobility as a 2D network of interacting plasticizer molecules forms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43254.     

Synthesis and properties of cross‐linked polymers from epoxidized rubber seed oil and triethylenetetramine

A series of epoxidized oils were prepared from rubber seed, soybean, jatropha, palm, and coconut oils. The epoxy content varied from 0.03 to 7.4 wt %, in accordance with the degree of unsaturation of the oils (lowest for coconut, highest for rubber seed oil). Bulk polymerization/curing of the epoxidized oils with triethylenetetramine (in the absence of a catalyst) was carried out in a batch setup (1 : 1 molar ratio of epoxide to primary amine groups, 100°C, 100 rpm, 30 min) followed by casting of the mixture in a steel mold (180°C, 200 bar, 21 h) and this resulted in cross‐linked resins. The effect of relevant pressing conditions such as time, temperature, pressure, and molar ratio of the epoxide and primary amine groups was investigated and modeled using multivariable nonlinear regression. Good agreement between experimental data and model were obtained. The rubber seed oil‐derived polymer has a T_g of 11.1°C, a tensile strength of 1.72 MPa, and strain at break of 182%. These values are slightly higher than for commercial epoxidized soybean oil (T_g of 6.9°C, tensile strength of 1.11 MPa, and strain at break of 145.7%). However, the comparison highlights the potential for these novel resins to be used at industrial/commercial level. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42591.     

Modification of vital wheat gluten with phosphoric acid to produce high free swelling capacity

Wheat gluten reacts with phosphoric acid in the presence of urea to produce natural superabsorbent gels. Fourier Transform Infra‐red (FT‐IR) spectroscopy and two‐dimensional gel electrophoresis (2DE) reveal chemical changes from the reaction. Temperatures above 120°C and dry conditions create the opportunity for reaction. FT‐IR analyses confirm the formation of esters, carbamates, and phosphoramides on the gluten samples. 2DE protein composition topographies indicate a shift in the isoelectric point (pI) to lower values along with extensive inter‐protein linkages. A free swelling capacity (FSC) in excess of 85× the mass of the converted gluten is obtainable using a conservative vacuum‐assisted method to recover and quantify the properties of the wet gel. Other methods produce FSC values nearly twice as high. FSC for acid‐treated gluten is lower for solutions containing solutes than the FSC for deionized water. Native gluten produces FSC values that are about 2% of those for treated gluten, but these values are less sensitive to the presence of ionic solutes and increase slightly in the presence of aqueous ethanol up to a mole fraction of 0.25.. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39440.     

Comparative effects of two different crosslinkers on the properties of vegetable oil-based polyurethanes

Thermoset polyurethanes (PUs) were prepared from a polyol derived from castor oil, 4,4′-methylene diphenyl diisocyanate (MDI) and different trifunctional low-molecular-weight crosslinkers, biobased glycerol (Gly) and petroleum-derived trimethylolpropane (TMP). The synthesis was carried out in bulk and without catalyst via one-step polymerization varying the components equivalent weight ratio, Polyol:MDI:Gly and Polyol:MDI:TMP, respectively. The physicochemical, morphological, thermal, dynamic–mechanical, and mechanical properties of the PUs were determined. The success of the reaction between the polyol and MDI was confirmed by Fourier transform infrared spectroscopy. The dynamic–mechanical and the mechanical properties as well as hardness were determined and related to the concentration of the low-molecular-weight crosslinkers utilized (Gly or TMP). However, important differences were observed between the synthesized two series, due to phase separation produced during the curing reaction, which affected more the materials prepared from TMP. Scanning electron microscopy images and dynamic–mechanical results confirmed this difference, related to the reactivity of primary and secondary hydroxyls present in the crosslinkers. Thermogravimetric analysis also showed to be sensible to the different structure of the crosslinkers with TMP leading to more thermally stable samples. Finally, measurements of water contact angle indicated that the surfaces were mostly hydrophobic with minor differences between the samples. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48741.     

Gelatin supports with immobilized laccase as sustainable biocatalysts for water treatment

Millimeter-size beads of gelatin are manufactured by dripping process to give enzyme supports qualified for micropollutants biodegradation in alternative wastewater treatment. The bead diameter is dependent on the tip diameter, the gelatin solution viscosity and the swelling of polymer chains in the collecting bath. Chemical crosslinking was performed with glutaraldehyde using optimal concentration to give mechanical and thermal properties suitable for application in stirred reactor in aqueous medium. Laccases from Trametes versicolor are grafted on the gelatin beads with glutaraldehyde. Sixty percentage of the initial enzymatic activity, evaluated by the oxidation of 2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS) is maintained after 10 successive cycles of reaction. Thermal stability at 60°C of immobilized biocatalysts is improved when compared to free enzymes (45% vs 10% of relative activity after 6 h of incubation). The simplicity of the procedure to form gelatin beads and their properties make them promising bio-based and biodegradable support for enzyme immobilization.     

Novel biocomposites based on wheat gluten and rubber wood sawdust

Rubber wood sawdust (RWS) was used as a reinforcement for wheat gluten based bioplastics. The RWS content was varied from 0, 5, 10, 15–20 wt %. Effects of the RWS content on the morphology, water absorption, mechanical, thermal, and biodegradation properties of the wheat gluten based bioplastic were investigated. An addition of RWS caused an improvement of the tensile strength and water resistance of the wheat gluten based bioplastics. Scanning electron micrograph of the wheat gluten/RWS composites with a 10 wt % of RWS revealed a good dispersion and uniform embedding of the RWS within the wheat gluten matrix. Agglomeration of RWS was observed when the RWS loads were increased (15 and 20 wt %). The biodegradation process of the composites depended on the amount of RWS. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43705.     

Biopolymer blended films of poly(butylene succinate)/cyclic olefin copolymer with enhanced mechanical strength for packaging applications

The demand for biodegradable materials is on the rise because humanity is now more concerned about a sustainable lifestyle than ever before. In this regard, we present solution casting synthesized novel biopolymer blended films of poly(butylene succinate)/cyclic olefin copolymer (PBS/COC) for packaging applications. These films were characterized by X-ray diffraction (XRD), Fourier transform infrared microscopy (FTIR), scanning electron microscopy (SEM), universal tensile testing (ASTM D882 standard), and antibacterial Disc diffusion tests using gram-negative Escherichia coli (E.coli) and gram-positive Staphylococcus aureus (S.aureus) bacteria. The XRD and FTIR revealed the type of bonding to be physical in-between the constituent polymers; ensuring the biodegradable nature of their blends, while the thickness of films was found to be <100 μm. The SEM, tensile, and antibacterial testing concluded that 30%PBS with 70%COC by weight blending is the best composition; showing a compact/pin-holes free morphology, the highest strength of 91 MPa, and contact inhibition with E.coli and S.aureus bacteria.     

Toughening of thermoset green zein resin: A comparison between natural rubber-based additives and plasticizers

Zein-based brittle thermoset green resin was toughened using sorbitol, natural rubber fibers (NRF), and epoxidized natural rubber fibers (ENRF). NRF and ENRF were electrospun directly into zein slurry. Chemical, thermal, and mechanical properties of zein resin containing NRF (Zein/NRF) and ENRF (Zein/ENRF) were compared with those of sorbitol-plasticized zein. NRF was found to be immiscible in zein and Zein/NRF resins showed two distinct glass transition temperatures (T _g), whereas Zein/ENRF specimens showed significant increases in both T _g and degradation temperature (T _d) due to crosslinking between zein and epoxidized natural rubber. ENRF was more effective in enhancing fracture toughness of zein than NRF or sorbitol. Increased ENRF loading to 15 wt % showed significant increase in toughness with minimal decreases in strength and Young's modulus. Sorbitol and NRF were unable to improve the toughness of zein resin significantly. Environment-friendly zein/ENRF resin with higher fracture toughness developed in this study would be suitable in many applications including green composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48512.     

Effect of hydrolysis and denaturation of wheat gluten on adhesive bond strength of wood joints

In this study the adhesive bond strength of different wheat gluten modifications and the relationship between molecular weight and adhesive strength was examined. Guanidine hydrochloride and sodium hydroxide were used as denaturation and dispersing agent. Additionally wheat proteins were hydrolyzed by alkaline conditions and enzymes. Effects of different treatments were observed by viscosity measurements and gel electrophoresis. Wood lap joints were prepared with modified proteins and tensile shear strength was tested under dry and wet conditions. In situ hardening of different formulations was analyzed by means of DMA with two‐layered specimens in a three‐point bending test set‐up. Higher solubility had no positive effect on dry bonding strength and wet bonding strength was even reduced. Depending on the degree of hydrolysis, significant improvement of adhesive bond strength was observed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of multi‐branched PDLA additives on the mechanical and thermomechanical properties of blends with PLLA

Stereocomplex formation between poly(l ‐lactic acid) (PLLA) and poly(d ‐lactic acid) (PDLA) in the melt state was investigated and altered via the addition of multi‐branched poly(d ‐lactide) (PDLA) additives. Two different multi‐branched PDLA additives, a 3‐arm and 4‐arm star‐shaped polymeric structure, were synthesized as potential heat resistance modifiers and incorporated into PLLA at 5, 10, and 20 (w/w) through melt blending. Mechanical and thermomechanical properties of these blends were compared with linear poly(l ‐lactide) (PLLA) as well as with blends formed by the addition of two linear PDLA analogs that had similar molecular weights to their branched counterparts. Blends with linear PDLA additives exhibited two distinct melting peaks at 170–180°C and 200–250°C which implied that two distinct crystalline domains were present, that of the homopolymer and that of the stereocomplex, the more stable crystalline structure formed by the co‐crystallization of both d ‐ and l ‐lactide enantiomers. In contrast, blends of PLLA with multi‐branched PDLA formed a single broad melting peak indicative of mainly formation of the stereocomplex, behavior which was confirmed by X‐ray diffraction (XRD) analysis. The heat deflection temperature determined by thermal mechanical analysis was improved for all blends compared to neat PLLA, with increases of up to180°C for 20% addition of the 3‐arm PLLA additive. Rheological properties of the blends, as characterized by complex viscosity (η*), remained stable over a wide temperature range. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42858.     

The activation of furfuryl alcohol polymerization by oxygen and its enhanced mechanical properties

The effect of oxygen and additional oxygen providers on furfuryl alcohol polymerization was investigated through chemical analyses and mechanical evaluation. NMR, UV–vis, Fourier transform infrared, and gas chromatography–mass spectrometry (GC–MS) results suggested that atmospheric oxygen and the further addition of an oxygen source functioned as an activator for the entire network polymerization. Interestingly, the construction of a conjugated structure on the furan linear chain, which is key to three-dimensional cross-linking, also appears to be accelerated in the presence of oxygen. Furthermore, the introduction of oxygen providers into the curing system successfully enhanced the mechanical properties of the cured furan resin.     

Building and origin of bio‐based bismaleimide resins with good processability,high thermal,and mechanical properties

Bio‐based high performance thermosetting resins have been urgently required by cutting‐edge fields for meeting sustainable development. A new kind of high performance thermosetting resins (BA‐n) with good processability, high thermal resistance, and mechanical properties was developed based on 4,4′‐bismaleimidodiphenylmethane (BDM) and renewable bis(5‐allyloxy)‐4‐methoxy‐2‐methylphenyl)methane (ABE) from bio‐based lignin derivative. The effect of the molar ratio of allyl to imide (n) on structures and properties of BA resins were systematically researched. BA‐n resins have much better processability, thermal, and mechanical properties than their petroleum‐based counterparts, 2,2′‐diallylbisphenol A‐modified BDM (BD‐n) resins. Compared with BD‐0.86, the best available bismaleimide (BMI) resin, BA‐0.86 not only has 6 h longer process window and 13.7 °C higher glass transition temperature, but also owns the highest flexural strength and modulus among all bio‐based allyl compound‐modified BMI resins reported. The origin behind these attractive performances of BA resins is revealed by discussing the unique crosslinked structure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45947.     

High-performance thermosets with tailored properties derived from multi-arm stared vanillin and carbon fiber composites

Vanillin, a rigid compound can be separated from lignin, is a promising sustainable candidate for industrial and high performance polymers, while synthesis of hexa-epoxies is challenging. Meanwhile, carbon fiber reinforced bio-based polymers combining high performance are more difficult to be achieved because of the contradictions of liquidity and high rigidity in the polymer structure and performance. In this paper, a novel hexa-epoxy functionalized bio-based epoxy resin (HPVIGEP) with a multi-arm star structure, which simultaneously reduced the viscosity and improved thermo-mechanical properties. The rheological behavior analysis results of HPVIGEP indicated that the viscosity was 3406.9 mPa·s at 25°C, which dramatically decreased by 75.8% compared to DGEBA (14,096 mPa·s), leading to excellent processability and adaptability. At the same time, the study on mechanical properties revealed that the cured HPVIGEP manifested 30.6%, 33.7% and 49.0% in higher tensile strength, tensile modulus and storage modulus (30°C) than of cured commercial epoxy, respectively. The tensile strength and flexural strength of carbon fiber composites which were applied HPVIGEP were increased by 9.3% and 10.9%, respectively. In a word, this work provides the promise for the application of environmentally friendly bio-based composite materials.     

A comparative study for the behavior of 3D-printed and compression molded PLA/POSS nanocomposites

Because of the biocompatible and nontoxic character of both PLA (polylactide) and POSS (Polyhedral Oligomeric Silsesquioxane) nanoparticles, recently being a significant alternative for biomedical parts; the main purpose of this study was to investigate performance of the 3D-printed PLA/POSS nanocomposites with respect to the compression molded PLA/POSS specimens. Due to the higher uniformity and higher homogeneity in the distribution of POSS nanoparticles in each PLA matrix layer, mechanical tests (tensile, flexural, and toughness) revealed that the improvements in the strength, elastic modulus and fracture toughness values of the 3D-printed specimens were much higher compared to their compression molded counterparts, the benefits starting from 13% increasing up to 78%. It was also observed that there was almost no deterioration in the physical structure and mechanical properties of the 3D-printed specimens, even after keeping them 120 days at 37°C in a physiological solution prepared by using the standard PBS (phosphate buffered saline) tablet.     

Thermosets resins prepared from soybean oil and lignin derivatives with high biocontent,superior thermal properties,and biodegradability

A bio-based monomer, methacrylated vanillyl alcohol (MVA), had been synthesized from vanillyl alcohol with methacrylate anhydride (MAA) via a solvent-free, efficient method. The synthesis of MVA was confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR). It was used to copolymerize with acrylated epoxidized soybean oil (AESO) to prepare a bio-based resin (MVA–AESO). Excess MAA of MVA synthesis was further used to modify AESO with hydroxyl groups, generating (MVA–MAESO) with higher unsaturation degree. Their chemical structure and modification were characterized using ¹³C NMR and Fourier transform infrared analyses. Pure AESO and MVA resins were used to compare with MVA–AESO and MVA–MAESO in terms of their viscosity, curing performance, mechanical, and thermal properties. The synthesized MVA–AESO and MVA–MAESO resins showed much lower viscosities than pure AESO due to the dilution of MVA. In addition, the incorporation of MVA reduced curing temperatures, activation energies which caused MVA–AESO and MVA–MAESO had higher curing degree than pure AESO. With the combination of MVA and modification of MAA, flexible AESO networks exhibited superior flexural properties, storage modulus, glass-transition temperature, and thermal stability. Furthermore, the biodegradation of the formulated bio-based resins were also investigated. Results showed that the addition of monomer and the increase in the content of CC bonds did not significantly affect the biodegradability of AESO, which may be due to the fact that the degradable groups of AESO were not affected. This environmentally friendly, low (volatile organic) resin, prepared by a high efficiency and environmental protection synthetic route, can potentially replace typical petroleum-based thermosets for the production environmentally friendly thermosetting resins. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48827.     

Effect of Ca2+ induced crosslinking on the mechanical and barrier properties of cast alginate films

The use of alginate as a coating material for packaging applications is currently limited due to its difficult processability and high moisture sensitivity. Therefore, this study addresses the crosslinking and scale‐up to a continuous application. Three different crosslinking agents were applied: CaCl₂ with ethylene diamine tetraacetic acid and two low soluble salts (CaHPO₄ and CaCO₃). Those were incorporated by internal setting in an alginate matrix with varying Ca²⁺ concentration ( ) and ratio. With the addition of Ca²⁺, the tensile strength and elongation at break of the cast alginate films increased. This was optimal for a of 0.010–0.015 g (g alginate)^?1 dependent on the crosslinking agent. The decrease in water vapor and oxygen permeability due to crosslinking was independent of the crosslinking agent. However, the optimal aiming to decrease permeability was different for the crosslinking agents: CaHPO₄ showed best results at a of 0.010 g (g alginate)^?1, CaCl₂ at 0.012 g (g alginate)^?1, and CaCO₃ at 0.027 g (g alginate)^?1. Upon all analyzed properties CaHPO₄ was the most promising crosslinking agent for alginate. Moreover, selected alginate formulations were successfully processed in a continuous lacquering plant. The produced two‐layer systems have very low oxygen permeabilities which can be further reduced by crosslinking. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45754.     

Effect of bone ash fillers on mechanical and thermal properties of biobased epoxy nanocomposites

In this study, the fabrication and characterization of bone ash filled biobased epoxy resin (Super SAP 100/1000, contains 37% biobased carbon content) nanocomposites are presented. Biosource bone ash was modified by size reduction and surface modification processes using a combination of ball milling and sonochemical techniques and characterized using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The modified bone ash particles were incorporated into biobased epoxy with noncontact mixing process. The as-fabricated nanocomposites were characterized using various thermal and mechanical analyses. The nanocomposites showed significant improvement in flexural strength (41.25%) and modulus (34.56%) for 2 wt% filler loading. Dynamic mechanical analysis (DMA) results showed improvement in both storage modulus and loss modulus. Additionally, DMA results showed a slight reduction in glass transition temperature which also complies with differential scanning calorimetry results. Thermomechanical analysis results showed a reduction in the coefficient of thermal expansion. Thermogravimetric analysis results showed improved thermal stability at both onset of degradation and the major degradation. These enhanced thermal and mechanical performances of the epoxy nanocomposites allows them to be suitable for lightweight aerospace, automotive, and biomedical applications.     

Study on the effect of woven sisal fiber mat on mechanical and viscoelastic properties of petroleum based epoxy and bioresin modified toughened epoxy network

Sisal fiber reinforced biocomposites are developed using both unmodified petrol based epoxy and bioresin modified epoxy as base matrix. Two bioresins, epoxidized soybean oil and epoxy methyl soyate (EMS) are used to modify the epoxy matrix for effective toughening and subsequently two layers of sisal fiber mat are incorporated to improve the mechanical and thermomechanical properties. Higher strength and modulus of the EMS modified epoxy composites reveals good interfacial bonding of matrix with the fibers. Fracture toughness parameters K_IC and G_IC are determined and found to be enhanced significantly. Notched impact strength is found to be higher for unmodified epoxy composite, whereas elongation at break is found to be much higher for modified epoxy blend. Dynamic mechanical analysis shows an improvement in the storage modulus for bioresin toughened composites on the account stiffness imparted by fibers. Loss modulus is found to be higher for EMS modified epoxy composite because of strong fiber–matrix interfacial bonding. Loss tangent curves show a strong influence of bioresin on damping behavior of epoxy composite. Strong fiber–matrix interface is found in modified epoxy composite by scanning electron microscopic analysis. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42699.     

A study of mechanical properties of biobased epoxy network: Effect of addition of epoxidized soybean oil and poly(furfuryl alcohol)

A novel biobased thermoset interpenetrating network was introduced in this study. Epoxidized soybean oil (ESO) and poly(furfuryl alcohol) (PFA) were added to a commercial biobased epoxy resin. It was hypothesized that addition of ESO and PFA can decrease brittleness of bioepoxy resin and also increase biobased content. Mechanical properties of samples were evaluated using tensile and impact test. It was found that the addition of ESO and PFA increased notched Izod impact energy by 76.6%. This significant increase was related to incorporation of long flexible chains of ESO into the matrix. Hybridization of ESO and PFA in bioepoxy reduced tensile strength (around 70%), tensile modulus (around 90%), and glass transition temperature in comparison to neat bioepoxy. Tensile strength and modulus of hybridized system can be further improved by addition of natural fibers and the resultant composite may be considered as a good candidate for applications in which damping properties are important. Crosslink density was calculated using dynamic mechanical analysis and a decrease in crosslink density was observed in hybridized system. PFA domains were observed in the matrix using atomic force microscopy in peak force quantitative nano‐mechanical mode and it revealed inhomogeneity in the crosslinked structure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44352.