Comparison of thermoset soy protein resin toughening by natural rubber and epoxidized natural rubber

Fully bio‐based soy protein isolate (SPI) resins were toughened using natural rubber (NR) and epoxidized natural rubber (ENR). Resin compositions containing up to 30 wt % NR or ENR were prepared and characterized for their physical, chemical and mechanical properties. Crosslinking between SPI and ENR was confirmed using ¹H‐NMR and ATR‐FTIR. All SPI/NR resins exhibited two distinctive drops in their modulus at glass transition temperature (T_g ) and degradation temperature (T_d ) at around ?50 and 215 °C, corresponding to major segmental motions of NR and SPI, respectively. SPI/ENR resins showed similar T_g and T_d transitions at slightly higher temperatures. For SPI/ENR specimens the increase in ENR content from 0 to 30 wt % showed major increase in T_g from ?23 to 13 °C as a result of crosslinking between SPI and ENR. The increase in ENR content from 0 to 30 wt % increased the fracture toughness from 0.13 to 1.02 MPa with minimum loss of tensile properties. The results indicated that ENR was not only more effective in toughening SPI than NR but the tensile properties of SPI/ENR were also significantly higher than the corresponding compositions of SPI/NR. SPI/ENR green resin with higher toughness could be used as fully biodegradable thermoset resin in many applications including green composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44665.     

Thermomechanical properties and water uptake capacity of soy protein‐based bioplastics processed by injection molding

The optimization of the processing conditions in the production of soy protein bioplastics by injection molding has been essential in order to develop materials with a great capacity to absorb water while displaying good mechanical properties. Using a 50/50 (wt/wt) soy protein/glycerol mixture, and 40 °C, 500 bar, and 70 °C as reference values for cylinder temperature, injection pressure, and mold temperature, respectively, the effect of those processing parameters over thermomechanical and hydrophilic properties was studied. Processing parameters did not show a great influence over the thermomechanical bending properties within temperatures ranging from ?30 to 130 °C, as most samples displayed a similar response, independently of the parameter studied. On the other hand, when studying tensile and hydrophilic properties, the main effect corresponded to the cylinder and mold temperature values, as pressure did not exert a clear influence when increased from 300 to 900 bar. Samples with a lower water uptake were obtained when processed at higher temperature, as a result of crosslinking promotion. Moreover, a greater extensibility was observed when bioplastics are processed at high mold temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43524.     

Self-healing efficiency of cinnamaldehyde-crosslinked soy protein resins with elongated soy protein microcapsules

Self-healing green thermoset soy protein isolate (SPI) based resins, crosslinked with cinnamaldehyde (CA), were developed. Self-healing was achieved using elongated microcapsules (MCs) as against spherical MCs that have been used in most earlier studies. MCs containing SPI solution as healant within poly(d,l-lactide-co-glycolide) shells were prepared using Water-in-oil-in-water (w/o/w) emulsion solvent evaporation (ESE) technique. Process parameters such as sodium tripolyphosphate (STP) and poly(vinyl alcohol) (PVA) concentrations and stirring speed were optimized to obtain elongated MCs. The average aspect ratio of MCs was over four. SPI resins crosslinked with 10% CA (10%CA-SPI) increased Young's modulus and fracture stress by 54% and 87%, respectively, compared with their noncrosslinked counterpart. The resins containing 15% elongated MCs (15%MC-10%CA-SPI) showed self-healing efficiencies of over 42% in fracture stress and about 35% in toughness recovery, after 24 h of healing. Improvement in self-healing can be attributed to the high aspect ratio of the MCs that increases the probability of MCs being in the path of the microcracks and releasing the healant. Elongated MCs also contain higher amount of healant than spherical ones of same diameter. Self-healing resins and composites can not only help prevent their premature failure but also improve their performance as well as service life and safety.     

Rheological behaviors exhibited by soy protein systems under dynamic aqueous environments

In this study, rheological behaviors of soy protein and soy flour as powders, pastes, and dispersions are characterized over a range of water contents and temperature to understand their processing in adhesives or paints. At ambient temperature, soy protein samples were characterized by low critical strain values (<0.1%), whereas soy flour samples exhibit linear viscoelastic regions >1% strain with 30–90% water content. On heating, the aqueous soy protein and soy flour compositions have complex rheological behaviors due to plasticization by water and the thermal denaturing and crosslinking of protein and carbohydrate with increasing temperature. Below 100 °C, soy protein rheological behaviors were attributable to the glass transition of the 7S and 11S soy globulin fractions, polymer flow, and plasticization by residual moisture. Above 100 °C, the onset of protein crosslinking was observed with this shifting to higher temperatures for samples still dehydrating. With soy flour samples, the residual moisture present above 100 °C similarly increase protein crosslinking to higher temperatures (125–148 °C) for samples with initial water contents of 30–90%. These results provide a basis for understanding why soy systems undergoing heat processing and rapid dehydration will require higher temperature and longer processing time to attain a cured, crosslinked state. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45513.     

Simultaneous plasticization and blending of isolate soy protein with poly[(butylene succinate)‐co‐adipate] by one‐step extrusion process

This article focuses on the preparation of isolated soy protein plasticized by a glycerol and water mixture/poly[(butylene succinate)‐co‐adipate] blends by an original single step extrusion process. Prepared blends were injection‐molded and characterized for their molecular interaction, morphology, rheological, thermal, dynamic mechanical, and mechanical properties. The comparison of these results with those obtained using a more regular two‐step compounding process validates the technical efficiency of this cost‐effective one‐step approach. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46442.     

Thiol-assisted bioinspired deposition of polyurethane onto cellulose as robust elastomer for reinforcing soy protein-based composites

The development of natural fiber-reinforced composites is environmentally friendly and therefore presents great potential; however, these composites are characterized by poor water resistance and interfacial bonding, which therefore limits its practical applications. This study reported a facile and novel approach for the construction of a high-performance microfibrillated cellulose (MFC) elastomer using thiol-functionalized polyurethane (PU-SH) with the assistance of a bioinspired dopamine platform. This elastomer was then employed as a reactive reinforcer to improve soy protein isolated (SPI) adhesive. The surface modification of MFC included the formation of a polydopamine (PDA) layer and Michael addition reactions between PU-SH and PDA, which were characterized by the Fourier-transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy measurements. It was found that the high-functional MFC elastomer served as a reactive cross-linker that gave rise to multiple physical and chemical interactions with the SPI matrix. This resulted in the optimization of the crosslinking system, which ultimately contributed to the solution of the bottleneck issues for natural fiber-reinforced composites. Consequently, the modified SPI-based adhesives notably enhanced the shear strength to 1.38 MPa, displaying a 236.6% increment compared to the unmodified adhesive. This strategy may provide a new insight into the design and preparation of superior natural plant-reinforced composites.     

Effects of fungal decay on properties of mechanical,chemical, and water absorption of wood plastic composites

This study investigated the associations between wood species and fungal resistance, as well as the effects of fungal decay on the properties of mechanical, chemical, and water absorption of wood polypropylene composites (WPCs) filled with white poplar, moso-bamboo, Chinese fir, Ramin, white pine, and rubber wood. Experimental results on weight losses and surface morphology both showed that fungal resistance of WPCs varied significantly with wood fiber species. Chinese fir and rubber wood filled composites separately presented the most and least durability against Coriolus versicolor (white rot) and Poria placenta (brown rot). In addition, fungal decay produced great differences in the properties of mechanical, chemical, and water absorptions between non-decayed and decayed composites. The decayed composites showed lower MOR, tensile strength, and impact strength, as well as higher MOE and water absorptions compared with non-decayed samples. These findings suggest that fungal decay could bring out dramatic influences on various properties of WPCs.     

Mechanical and dimensional performance of poly(lactic acid) 3D-printed parts using thin plate spline interpolation

In additive manufacturing, determining the correct deposition parameters is very important as this can affect the final properties of printed parts. Since there is no agreement on the optimal level of the different printing parameters in reported results, this work evaluated the influences of layer thickness (LT), deposition speed (DS) and printing direction (PD) on tensile properties and dimensional accuracy of poly(lactic acid) 3D parts evaluating the possibility of using thin plate spline interpolation method (TPSIM) of data, a new approach, in determination of optimized fused deposition modeling process parameters. It was observed that the use of low levels of LT (0.10 mm), DS (40 mm/s), and PD (0°) provided parts with higher mechanical strength and dimensional performance. Denser parts showed lower anisotropy effect and, consequently, best tensile properties were obtained. TPSIM was an efficient mathematical analysis and well fitted results of predicted and experimental results.     

Processing and properties of phthalic anhydride modified soy protein/glycerol plasticized soy protein composite films

Phthalic anhydride modified soy protein (PAS)/glycerol plasticized soy protein (GPS) composite films were fabricated by using extrusion and compression‐molding. Modified with phthalic anhydride, the soy protein lost its thermoplastic ability and was used as a filler to reinforce the GPS matrix. Fourier transform infrared spectra, optical transmittance, scanning electron microscope, mechanical tests, water resistance tests, as well as thermo‐gravimetric analysis were carried out to investigate the structure and properties of PAS and the plastic composites. The similar chemical structure of PAS and GPS led to compatibility of the two components resulting in high transparency and enhanced tensile properties of the composites. The water resistance of GPS was also improved by the incorporation of PAS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42221.     

Effect of bagasse content on low frequency acoustic performance of soy oil-based biodegradable foams filled with bagasse and regulation mechanism analysis

Reducing noise by using sound absorption materials is an important approach to lessen the harm of noise pollution. Controlling acoustic performance and analyzing the mechanism of the flexible polyurethane biofoams derived from vegetable oil polyol and filled with agricultural and forestry wastes can provide theoretical guidance in designing the biodegradable energy-saving sound absorbing materials. A series of biofoams were synthesized by using soy oil-based polyol instead of 50 wt% petroleum-based polyol with different content of natural resource bagasse as fillers. The material is characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis to study the morphology, chemical interaction between constituent phases and thermal stability respectively. The effects of bagasse on morphology, mechanical properties, thermal properties, sound absorption coefficient and degradability of biofoams were investigated. Natural resource bagasse can improve the sound absorption coefficient at low frequency region by changing the cell size, opening ratio and cell wall structure of biofoams. The study confirms that it is possible to control and enhance the acoustic performance of the biofoams by adjusting bagasse content for sound absorption materials.     

High bonding strength and boiling water resistance of soy protein‐based adhesives via organosilicon–acrylate microemulsion and epoxy synergistic interfacial enhancement

Boiling water resistance, an important indicator of wood adhesives, represents the capability of adhesives for exterior woodwork applications. However, soy‐based adhesives show poor behaviors in this respect, which limit their applications in outdoor environments. In this article, we report a synergistic modification method of integrating a cocrosslinking system of epoxied polyamideamine‐epichlorohydrin (PAE) and organosilicon–acrylate copolymer latexes (OACLs) to improve soybean meal (SM)‐based adhesive properties. Tailored PAE and OACL SM‐based adhesives demonstrated robust crosslinking structures via multi‐interfacial interactions, where PAE and OACL served as building blocks of an interpenetrating network, which was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The dry‐shear strength, wet‐shear strength, and boiling water strength of the resulting SM‐based adhesives were 1.41 ± 0.13, 1.32 ± 0.17, and 1.20 ± 0.11 MPa, respectively, with 15 wt % OACL loading; these were 41, 45, and 90% increases, respectively, over the SM–PAE adhesive with which we compared them. Most importantly, the excellent boiling water resistance of the adhesives make them practical for exterior plywood. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46061.     

Ultra-flexible PLA-based blends for the manufacturing of biodegradable tamper-evident screw caps by injection molding

Mono-material in the manufacturing of oil-based plastic bottles has been so far not considered because of the poor flexibility of polyethylene terephthalate (PET). The undercuts of PET caps (i.e., the threads of the screw caps) would be torn-off during the ejection step of the injection/compression molding processes that are commonly used to fabricate them. In this respect, the present work deals with the design and development of innovative biodegradable polyester-based blends with high flexibility, intended for the manufacturing of screw-cap, being this element the most critical in the implementation of the complete bottle. The blend is based on polylactic acid and it is tailored for injection molding of tamper-evident screw plastic caps by the addition of another biodegradable polyester, that is, polybutylene adipate-co-terephthalate. The effect of the addition of a barrier agent, polyvinyl alcohol, on the overall behavior of the blends was also studied in the perspective of the implementation of caps featuring barrier properties against water vapor and oxygen. The same material could be, however, easily tailored for the fabrication of the bottle body and printed label to get to the mono-material bottle. Twin-screw corotating extrusion of the compound, injection molding of the plastic material for the fabrication of the screw caps, and evaluation of the thermophysical and mechanical properties of the screw caps are hereinafter discussed. The biodegradable polyester-based blends are found to be suitable for injection molding of the tamper-evident screw caps, exhibiting adequate flexibility during ejection from the mold. The screw caps can also boast appreciable mechanical strength and impact resistance as well as good thermal stability.     

Reducing and stabilizing the viscosity of natural rubber by using sugars: Interference of the Maillard reaction between proteins and sugars

This work is an extension of previous work elucidating the reduction and stabilization of solid natural rubber (NR) viscosity by using sugars. Various amounts of glucose, fructose, sucrose, and maltose were incorporated into fresh NR (FNR), deproteinized NR (DPNR), and synthetic polyisoprene (IR) latexes. The results revealed that all sugars cannot decrease the Mooney viscosity of FNR, while only monosaccharides, that is, glucose and fructose, can significantly decrease the Mooney viscosity of both DPNR and IR by way of a lubrication mechanism. The proteins in FNR can diminish the capability of glucose and fructose to decrease the Mooney viscosity. Furthermore, glucose was found to reduce the occurrence of storage hardening in DPNR by interacting with polar groups of phospholipids at the rubber chain ends. Measurements of browning intensity as well as analysis of Maillard reaction products together with the NR protein–glucose model compound were utilized to confirm that the reduction and stabilization of the viscosity of NR using monosaccharides were interfered by the Maillard reaction between the proteins in NR and the monosaccharides.     

Effect of montmorillonite clay addition on the morphological and physical properties of Jatropha curcas L. and Glycine max L. protein concentrate films

Protein concentrates from jatropha (JPC) and soy seeds (SPC) were obtained by solubilization and acid precipitation of proteins. JPC and SPC films were prepared by the casting method, using two different montmorillonite (MMT) clay concentrations and plasticized with glycerol. Film properties were evaluated by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, thermogravimetric analysis, tensile properties, water retention, and water vapor transmission rate (WVRT). Typical tactoid microcomposite structures were found to be heterogeneously dispersed in the films containing MMT. A small XRD peak was found in films with MMT. Slight improvements in thermal stability and tensile strength were observed in the films with MMT. Reductions in water retention and WVRT were obtained when MMT was added into the films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44459.     

Protein‐based bioplastics and their antibacterial potential

The use of conventional petroleum‐based plastics in many applications poses the risk of contamination, potentially causing infection when used in medical applications, and contamination when used in food packaging. Nontraditional materials such as protein are being examined for their potential use in the production of bioplastics for applications that require uncontaminated materials. The proteins of albumin, soy, and whey provide possible sources of raw material for bioplastic production, as they have already been utilized in the area of edible films and low‐stress applications. We conducted this study to investigate the thermal, viscoelastic, and antibacterial properties of the albumin, soy, and whey bioplastics with the use of three plasticizers—water, glycerol, and natural rubber latex (NRL). Bacillus subtilis and Escherichia coli were utilized as Gram (+) and Gram (?) species, respectively, for antimicrobial analysis. Albumin and whey bioplastics exhibited similar thermal and viscoelastic properties, whereas soy bioplastics had varied viscoelastic properties based on the plasticizer used. In terms of antibacterial activity, the albumin–glycerol and whey–glycerol were the best bioplastics, as no bacterial growth was observed on the plastics after 24 h of inoculation. In terms of the future impact of this research, the aim will be to scale up production of the bioplastics for use in food packaging as well as biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41931.     

Antioxidant packaging development and optimization using agroindustrial wastes

The increasing use of non-biodegradable materials and the difficulty in recycling most of the available packaging have been pushing the development of biodegradable packaging. In this study, the potential uses of agroindustrial wastes to produce biodegradable films with antioxidant capacity were investigated. Starch films were produced by casting method using bran from jaboticaba peel, mango peel, and broccoli stalk. The influence of the concentration or type of bran in the properties of the films was evaluated through a central composite design. The results were analyzed by response surface and desirability function. Except for elongation and water solubility, the fitted equations were predictive in all studied properties. The films prepared from a higher concentration of mango peel exhibited better antioxidant capacity, while the broccoli stalk had no significant effect on antioxidant properties. The optimal formulation of the film (2.8% of jaboticaba peel and 20.0% of mango peel) and their predicted response variables (0.8 MPa for tensile strength, 40.0 MPa for Young's modulus, 4.5 mg/ml for IC₅₀, and 41.6% for inhibition percentage) were defined according to the results. The optimization was satisfactory and the film presented high antioxidant capacity and moderate mechanical properties, proving to be an alternative to replace plastic packaging.     

Surface and degradation properties of thermoplastic blends from albumin and zein‐based plastics

The use of traditional petroleum‐based thermoplastics in food packaging applications pose an environmental hazard, as their lack of biodegradability creates waste that environmental systems are unable to cope with. To address this issue, the investigation of surface, biodegradation, and water solubility properties of the albumin and zein thermoplastic blends plasticized with glycerol and mixed with varying amounts of low‐density polyethylene (LDPE) is conducted. When subjected to soil burial, albumin as a bioplastic completely biodegrades within two months, while a zein‐based bioplastic is more resilient to attacks from microbes within the soil (4.34% of intial mass remains). If albumin and zein proteins are used in the production of thermoplastics in tandem with LDPE, it could be possible to produce a plastic that will naturally biodegrade over time, decreasing the environmental impact of the use of thermoplastics in medical and food packaging applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44646.     

Physico‐chemical,thermal, and mechanical approaches for the characterization of solubilized and solid state chitosans

This study was conducted on the both solid and solubilized chitosans to propose an approach for the physico‐chemical, thermal and mechanical characterizations of this polysaccharide. The polysaccharide used was a 90% deacetylated chitosan having a molecular weight of 98.4 kDa. The flow property of chitosan solutions was evaluated revealing a shear‐thinning behavior. The thermal characterization was carried out by studying heat specific capacity, glass transition temperature, and thermal conductivity on chitosan dried specimens (solid state). Their T_g were measured by DSC and confirmed by DMA at 102 and 122°C depending on concentrations of initial chitosan solutions. The mechanical characterization was conducted by analyzing Young modulus, tensile strength, and elongation at break of chitosan specimens. They exhibited a higher elongation at break and a lower tensile strength when made from high concentrated chitosan solution (9% w/v). Differences in mechanical behavior of specimens were explained by differences of crystallinity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41257.     

The effect of poly(ethylene glycol) as plasticizer in blends of poly(lactic acid) and poly(butylene succinate)

The effect of polyethylene glycol (PEG) on the mechanical and thermal properties of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends was examined. Overall, it was found that PEG acted as an effective plasticizer for the PLA phase in these microphase‐separated blends, increasing the elongation at break in all blends and decreasing the T_g of the PLA phase. Significant effects on other properties were also observed. The tensile strength and Young's modulus both decreased with increasing PEG content in the blends. In contrast, the elongation at break increased with the addition of PEG, suggesting that PEG acted as a plasticizer in the polymer blends. Scanning electron microscope images showed that the fracture mode of PLA changed from brittle to ductile with the addition of PEG in the polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43044.     

Mechanical and thermal properties of poly(butylene succinate)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) biodegradable blends

Biodegradable polymer blends of poly(butylene succinate) (PBS) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) were prepared with different compositions. The mechanical properties of the blends were studied through tensile testing and dynamic mechanical thermal analysis. The dependence of the elastic modulus and strength data on the blend composition was modeled on the basis of the equivalent box model. The fitting parameters indicated complete immiscibility between PBS and PHBV and a moderate adhesion level between them. The immiscibility of the parent phases was also evidenced by scanning electron observation of the prepared blends. The thermal properties of the blends were studied through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results showed an enhancement of the crystallization behavior of PBS after it was blended with PHBV, whereas the thermal stability of PBS was reduced in the blends, as shown by the TGA thermograms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42815.