A Novel Eco-friendly Blood Meal-based Bio-adhesive: Preparation and Performance

In this reported study, a renewable and eco-friendly blood meal-based (BM) bio-adhesive was developed for the plywood fabrication. Polyvinyl alcohol (PVA), sodium dodecyl sulphate (SDS), and triglycidylamine (TGA) were respectively employed as emulsifier, denaturant and crosslinking agent to modify the BM adhesive. Three-ply plywood was manufactured and its wet shear strength was tested. The solid content, residual rate, functional groups, thermal degradation behavior, and cross section micromorphology of the resulting adhesives were characterized in detail. The experimental results showed that PVA prevented the BM agglomeration, SDS unfolded the structure of protein and then TGA reacted with the exposed active groups in the BM protein molecules, forming a cross-linked structure. As a result, the thermal stability of the modified BM adhesive was improved and the cross section of the cured adhesive was more homogeneous, which enhanced the performance of the adhesive. Consequently, the wet shear strength of the plywood bonded by modified BM adhesive markedly increased by 388% to 1.27 MPa. Compared with soy bean meal-based adhesive, a higher protein content and hydrophobic amino acids content of BM are benefit for fabricating high performance bio-based adhesive, which rendered the BM adhesive practical for plywood industrial application.     

Properties of Distillers Grains Composites: A Preliminary Investigation

Interest in renewable biofuel sources has intensified in recent years, leading to greatly increased production of ethanol and its primary coproduct, Distillers Dried Grain with Solubles (DDGS). Consequently, the development of new outlets for DDGS has become crucial to maintaining the economic viability of the industry. In light of these developments, this preliminary study aimed to determine the suitability of DDGS for use as a biofiller in low-cost composites that could be produced by rapid prototyping applications. The effects of DDGS content, particle size, curing temperature, and compression on resulting properties, such as flexural strength, modulus of elasticity, water activity, and color were evaluated for two adhesive bases. The composites formed with phenolic resin glue were found to be greatly superior to glue in terms of mechanical strength and durability: resin-based composites had maximum fiber stresses of 150–380 kPa, while glue composites had values between 6 kPa and 35 kPa; additionally, glue composites experienced relatively rapid microbial growth. In the resin composites, both decreased particle size and increased compression resulted in increased mechanical strength, while a moderate DDGS content was found to increase flexural strength but decrease Young’s modulus. These results indicate that DDGS has the potential to be used in resin glue-based composites to both improve flexural strength and improve potential biodegradability.     

Effects of Sodium Bisulfite on the Physicochemical and Adhesion Properties of Canola Protein Fractions

This study focused on investigating the potential of using canola protein fractions as bio-degradable wood adhesives. Native and sodium bisulfite (NaHSO₃)-modified canola protein fractions isolated successively at different pH values (7.0, 5.5, and 3.5) was used as adhesives. Wood specimens were assembled with adhesives at a pressure of 2?MPa at 150, 170, or 190?°C for 10?min. The adhesion performance of adhesives were evaluated by wet, soak, and dry shear strength. Their physicochemical properties: extractability, electrophoresis profiles, thermal, rheological and morphological properties were also characterized. Results showed that canola protein had the highest protein yield and purity at pH 5.5. Electrophoresis profile proved that NaHSO₃ cleaved the disulfide bonds in canola protein. This could induce extra charges (RS-SO₃ ^?) on the protein surface, leading to the reduced apparent viscosity. Thermal analysis implied that the thermal transition temperature of canola protein decreased with modification of NaHSO₃. Canola protein adhesives showed excellent dry and soak shear strength with 100?% wood cohesive failure in all curing temperatures. The wet adhesion strength of native and modified canola protein fraction adhesives at pH 5.5 and pH 3.5 (3.9?C4.1?MPa) was higher than the fractions at pH 7.0. NaHSO₃ had insignificant effects on the adhesion performance of canola protein adhesives but notably improved the handling and flow-ability properties of canola protein adhesives.     

Compression Molding of Phenolic Resin and Corn-based DDGS Blends

With the rapid growth in the ethanol fuel industry in recent years, considerable research is being devoted to optimizing the use of processing coproducts, such as distillers dried grains with solubles (DDGS), in livestock diets. Because these residues contain high fiber levels, they may be amendable to incorporation into bio-based composites. Thus, the goal of this study was to demonstrate the viability of using corn-based DDGS as a biofiller with phenolic resin, in order to produce a novel biomaterial. DDGS was blended with phenolic resin at 0, 10, 25, 50, 75, and 90%, by weight, and then compression molded at 51 MPa (3.7 tons/in²) and 174 °C (345°F). Molded specimens were then tested for tensile strength. Tensile yield strengths ranged from 32 MPa (4,700 psi) to 7.6 MPa (1,100 psi), while the engineering strain ranged from 0.6% to 1.25%. Results indicate that DDGS concentrations between 25% and 50% retained sufficient mechanical strength and thus represent reasonable inclusion values. Additionally, data were similar to those from other studies that have investigated biofillers. Follow-up studies should quantify the effects of altering molding parameters, including molding pressure, temperature, and time, as well as pretreatment of the DDGS. Additionally, strength of the DDGS composites should be optimized through the use of coupling agents or other additives. Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the United States Department of Agriculture and does not imply approval of a product to the exclusion of others that may be suitable.     

Effects of Preparation Parameters on Properties of Soy Protein-Based Fiberboard

The effects of manufacturing parameters on mechanical properties of medium density fibreboard (MDF) bonded with modified soy protein-based glue were studied to find an appropriate manufacture technology. Physical properties of MDF made with different amount of wax emulsion were measured. Results indicated that water repellent had no obvious influence on physical properties of soy protein-based MDF boards. The fiberboards bonded with soy protein-based glue showed stronger water resistance properties than those bonded with urea–formaldehyde (UF) resins. Furthermore, the soy protein-based MDF boards had good quality [25.2% 24 h soak thickness swell (TS), 29.9 MPa modulus of rupture (MOR), 3130 MPa modulus of elasticity (MOE)], which met requirements of Chinese national standard. Practical processing parameters were obtained by orthogonal experiment, i.e., glue content 8.0%, hot-press temperature 200 °C, and hot-press time 150 s.     

Processing and Physical Properties of Plastics Made from Soy Protein Polyester Blends

Blending soy protein with polyesters using a polyvinyllactam as a compatibilizer successfully made soy protein-based plastics. The polyesters used to produce blends included polycaprolactone (PCL) and Biomax (a commercial biodegradable polyester). The blends were processed by compounding extrusion and injection molding. Blends containing soy protein/Biomax-poly(vinyl alcohol) had tensile strengths ranging from 16–22 MPa, with samples containing larger percentages of the synthetic polymer exhibiting greater strengths. Blends made from soy protein, Biomax, and PCL had tensile strengths ranging from 27–33 MPa. All the blends had high Young's moduli but demonstrated brittle characteristics as evident from their low elongations at break, ranging from 1.8–3.1%. Plastics made from soy protein/polyester blends exhibited low water absorption and had good stability under ambient conditions relative to the plastics made from soy protein alone. Blends made from soy protein flour produced plastics with the lowest water absorption.     

Processing and Characterization of Glycerol-Plasticized Soy Protein Plastics Reinforced with Citric Acid-Modified Starch Nanoparticles

Citric acid-modified starch nanoparticles with an average size of 82 nm were prepared through precipitation from gelatinized starch solution by ethanol and further modification with citric acid. When being incorporated in glycerol-plasticized soy protein plastics, citric acid-modified starch nanoparticles displayed dramatic reinforcing effect. The resulted nanocomposite plastics exhibited improvement in mechanical performance. Also, the water uptake decreased, indicating an increase of water resistance. The modified starch nanoparticles had a good compatibility with soy protein matrix. Possessing a relative hydrophobic surface, the filler would prefer to interact with protein-rich domains in glycerol-plasticized soy protein. The work provided a green approach of biodegradable materials based on naturally occurring biopolymers.     

High compressive strength of home waste and polyvinyl acetate composites containing silica nanoparticle filler

Simple mixing and hot pressing methods were used to make composites from home waste—in particular, paper and dry leaves—using polyvinyl acetate (PVAc) as an adhesive and silica nanoparticles as filler. The optimum composition for the strongest composites, in terms of compressive strength, had a mass ratio of silica nanoparticles/PVAc/(paper + dry leaves) of 3:80:280. With this mass ratio, a compressive strength of 68.50 MPa was obtained for samples prepared at a pressing temperature of 150°C, pressing pressure of 100 MPa, and pressing time of 20 min. The addition of silica nanoparticles increased the compressive strength by about 50%, compared with composites made without the addition of nanosilica (45.60 MPa). Higher compressive strength was obtained at a higher pressing pressure. At a pressing pressure of 120 MPa, pressing temperature of 150°C, and pressing time of 20 min, a compressive strength of 69.10 MPa was obtained. When the pressing time was increased to 45 min at a pressing pressure of 120 MPa, a compressive strength of 84.37 MPa was measured. A model was also proposed to explain the effects of pressing pressure and pressing time on compressive strength. The model predictions were in good agreement with the experimental data.     

Wet Strength and Water Resistance of Modified Soy Protein Adhesives and Effects of Drying Treatment

Soy protein isolate (SPI) was modified using sodium dodecyl sulfate (SDS) and guanidine hydrochloride (GuHCl). Adhesion performance of the modified SPI on fiberboard was studied. The Water-soluble mass of the modified SPI adhesives was examined following modified ASTM D5570. The SDS-modified SPI containing 91% protein had a water-soluble mass of 1.7%. To be considered a water-resistant adhesive, the water-soluble mass of adhesive should be less than 2%. The wet shear strength test showed 100% cohesive failure within fiberboard, indicating that the modified SPI has good water resistance. The effect of drying treatment on adhesion performance of the SDS-modified SPI on fiberboard was then investigated. Drying treatment significantly affected the final adhesion performance. Shear strength did not change much, but the percentage of cohesive failure within fiberboard increased markedly as drying temperature increased. All the unsoaked, soaked, and wet specimens glued by the adhesives treated at 70° or 90°C had 100% cohesive failure within fiberboard. Viscosity also increased greatly with an increase in drying temperature. This information will be useful in developing low-cost adhesive processing system in the future.     

Viscosity of Soy Protein Plastics Determined by Screw-Driven Capillary Rheometry

Soy protein plastics are a renewable, biodegradable alternative to fossil fuel-based plastic resins. Processing of soy protein plastics using conventional methods (injection molding, extrusion) has met with some success. Viscosities of processable formulations that contain soy protein along with the necessary additives, such as glycerol and cornstarch, have not been reported, but are necessary for extrusion modeling and the design of extrusion dies. Resins consisting of soy protein isolate-cornstarch ratios of 4:1, 3:2, and 2:3 were plasticized with glycerol and soy oil, compounded in a twin screw extruder and adjusted to 10% moisture. The effects on viscosity of added sodium sulfite, a titanate coupling agent and recycling were evaluated using a screw-driven capillary rheometer at shear rates of 100–800/s. The viscosities fit a power-law model and were found to be shear thinning with power-law indices, n, of 0.18–0.46 and consistency indices, m, of 1.1 × 10⁴–1.0 × 10⁵. Power-law indices decreased and consistency indices increased with increasing soy protein-to-cornstarch ratio and in the absence of sodium sulfite. Addition of the titanate coupling agent resulted in increased power-law index and decreased consistency index. Viscosities at a shear rate of 400/s decreased with recycling, except for the 4:1 soy protein isolate to cornstarch formulation, which displayed evidence of wall slip. Power-law indices were unaffected by recycling. Viscosities in the tested shear rate range were comparable to polystyrene and low-density polyethylene indicating soy protein plastics are potential drop-in replacements for commodity resins on conventional plastics processing equipment.     

Preliminary Studies on Converting Agricultural Waste into Biodegradable Plastics – Part III: Sawdust

Summary Hardwood sawdust was derivatized either by carboxymethylation, glutaration, maleiation, phthallation, or succination in order to produce anionic materials suitable for complexation with soy protein isolate. Blending each derivative with soy protein isolate resulted in instant precipitation of gels. Infrared spectroscopy and differential scanning calorimetry suggested that each derivative formed a complex with protein. Reaction products could be dried into pellets exhibiting tensile strengths between 0.9–2.4 MPa, suggested that these materials could be promising candidates for biodegradable structural materials.     

Bioabsorbable soy protein plastic composites: Effect of polyphosphate fillers on water absorption and mechanical properties

The use of synthetic and natural bioabsorbable plastics has been severely limited due to their low stiffness and strength properties as well as their strong tendency to absorb moisture. This research focused on the development of bioabsorbable polyphosphate filler/soy protein plastic composites with enhanced stiffness, strength, and water resistance. Bioabsorbable polyphosphate fillers, biodegradable soy protein isolate, plasticizer, and adhesion promoter were homogenized and compression-molded. Physical, mechanical, and water absorption testing was performed on the molded specimens. Results showed improvements in stiffness, strength, and water resistance with increasing polyphosphate filler content up to 20% by weight. Application of a coupling agent produced further mechanical property enhancements and a dramatic improvement in water resistance, interpreted by an interfacial chemical bonding model. Examination of the fracture surfaces of the materials revealed that the addition of the polyphosphate fillers changed the failure mode from brittle to pseudo-ductile. These results suggest that these materials are suitable for many load-bearing applications in both humid and dry environments where current soy protein plastics are not usable.     

The Use of Interfacial Blend to Increase the Adhesion Properties of Natural Rubber/Polyvinylalcohol Multilayer Using Electron Beam Irradiation

Multilayers of natural rubber (NR) and polyvinylalcohol (PVA) were processed by casting natural rubber latex (NRL) then PVA with varying layer thickness. Adhesion between NR and PVA was found to be very poor, as determined with the peel method. The films of interfacial blend were composed of NRL and PVA having different ratios as a layer between NR/PVA layer, possessing good adhesion and exhibited one mechanical phase in tensile-elongation at break tests. The result of adhesion was confirmed by thermogravimetric analysis and scanning electron microscopy study. Also, adhesion was too strong for delamination at the interface when the unit of three layers NR/blend/PVA was irradiated at 25 kGy. To probe the effect of the adhesion difference on mechanical behavior and deformation of NR/blend/PVA layers at dry and wet conditions, the peel strength was examined as a function of layer thickness and aging time. The results indicated that the interfacial blend, irradiation process and film thickness were the key parameters affecting adhesion of NR/PVA layer.     

Characterization of Sorghum Bran/Recycled Low Density Polyethylene for the Manufacturing of Polymer Composites

The objective of the study was to investigate the suitability of using sorghum bran in recycled low density polyethylene (R-LDPE) composites manufacturing. In response to the disposal of environmental problematic agricultural and polymer waste, composite sheets using recycled low density polyethylene and sorghum bran of different loadings (5, 10, 15 and 20 wt%) were prepared by melt compounding and compression molding. The effects of sorghum bran loadings on the mechanical, thermal, water absorption, swelling and crystalline properties of the composites were determined. Characterization of composites was carried out using X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermo gravimetric (TGA/DTG) and mechanical analyses. It was found that increasing fiber loadings resulted to increased moduli and tensile strength while hardness was decreased. XRD indicated that fiber addition to R-LDPE did not change characteristic peak position. DSC results showed that the R-LDPE had significantly larger peak heat flow during cooling run than the blank R-LDPE, showing higher crystallization rates for R-LDPE. The results obtained confirmed that sorghum bran particles showed some potential as a good reinforcement in polymer matrix composites and indicate its thermal stability for possibly future composite applications.     

Biodegradable plastic made from soybean products. II. Effects of cross-linking and cellulose incorporation on mechanical properties and water absorption

Soy isolate was treated with formaldehyde and glyoxal at 1.0, 2.5, and 5.0% (w/w isolate) and with adipic and acetic anhydrides. The materials were then compression-molded into plastic tensile bars and tested for tensile and yield strength, percentage elongation, Young's modulus, and water absorption. Treatment with 5% formaldehyde increased the tensile strength significantly, to 4.9 kg/mm², compared with the untreated sample (3.7 kg/mm²). The yield strength increased slightly, to 0.68 kg/mm². Elongation was significantly less after treatment with formaldehyde. Young's modulus increased after treatment and leveled off at 174 kg/mm². Water absorption decreased as the formaldehyde concentration increased. Treatment with either glyoxal or adipic/acetic anhydride had a detrimental effect on the mechanical properties of the plastic specimens. Water absorption was decreased by glyoxal treatment but was not affected by adipic/acetic anhydride treatment. Long-fiber (lf), short-fiber (sf), and microcrystalline (mc) cellulose were incorporated into soy isolate at various levels. Cellulose addition decreased the percentage elongation and increased the rigidity of the plastic. All three cellulose additions increased Young's modulus. The tensile strength increased with the addition of sf-cellulose to soy isolate; lf-cellulose decreased the tensile strength, whereas the incorporation of mc-cellulose did not have a significant effect. The yield strength increased slightly with the addition of sf-cellulose and was less affected by the addition of lf- or mc-cellulose. All three types of cellulose slightly decreased water absorption at ca. 15% content.Journal Paper No. J-15563 of the Iowa Agriculture and Home Economics Experiment Station, Ames; Project No. 2863.     

Tensile Strength, Elongation, Hardness, and Tensile and Flexural Moduli of PLA Filled with Glycerol-Plasticized DDGS

Rapid growth of the biofuel industry is generating large amounts of coproducts such as distillers dried grains with solubles (DDGS) from ethanol production and glycerol from biodiesel. Currently these coproducts are undervalued, but they have application in the plastics industry as property modifiers. The objective of this research effort is to quantify the effects on mechanical properties of adding DDGS and glycerol to polylactic acid (PLA). The methodology was to physically mix DDGS, as filler, with PLA pellets and injection mold the blends into test bars using glycerol as a plasticizer. The bars were subject to mechanical testing procedures to obtain tensile strength, tensile and flexural moduli, elongation to break, and surface hardness of blends from 0 to 90?%, by weight, of plasticized filler. Blends were typically relatively brittle with little or no yielding prior to fracture, and the addition of glycerol enabled molding of blends with high levels of DDGS but did not increase strength. Any presence of filler decreased the tensile strength of the PLA, and 20?C30?% filler reduced strength by 60?%. The 35?C50?% filled PLA had about one-fifth the value for pure PLA; at 60?C65?% filler level, about 10?% tensile strength remained; and over 80?% filler, 95?% of the strength was lost. Over 20?% filler, the tensile modulus decreased. The 35?% plasticized, filled blend yielded about one-half the stiffness as the pure PLA case; flexural modulus trended in the same manner but demonstrated a greater loss of stiffness. Most blends had less than 3?% elongation to break while surface hardness measurements indicated that up to 60?% filler reduced Shore D hardness by less than 20?%. The tensile strength and modulus data are consistent with the findings of other researchers and indicate that the type of filler and amount and sequence of plasticization are secondary effects, and the total PLA displaced is the dominant factor in determining the mechanical strength of the PLA and DDGS blends. Up to 65?% plasticized DDGS filler can be injection molded, and sufficient mechanical strength exists to create a variety of products. Such a novel material provides higher-value utilization of the biofuel coproducts of glycerol and DDGS and maintains the biodegradable and biocompatible nature of PLA.     

Injection Molded Biocomposites from Soy Protein Based Bioplastic and Short Industrial Hemp Fiber

Biocomposites from soy based bioplastic and chopped industrial hemp fiber were fabricated using twin-screw extrusion and injection molding process. Soy based bioplastics were prepared through cooking with plasticizer and blending with biodegradable poly(ester amide). Mechanical, thermal properties and fracture surface morphology of the “green”/biocomposites were evaluated with universal testing system (UTS), dynamic mechanical analysis (DMA), Environmental Scanning Electron Microscopy (ESEM). It was found that the tensile strength and modulus, flexural strength and modulus, impact strength and heat deflection temperature of industrial hemp fiber reinforced biocomposites significantly improved. The fracture surfaces showed no signs of matrix on the fiber surface suggesting poor interfacial adhesion.     

Tannic acid as a novel and green leaching reagent for cobalt and lithium recycling from spent lithium-ion batteries

Tannic acid–acetic acid is proposed as novel and green chemicals for cobalt and lithium recycling from spent lithium-ion batteries through a leaching process. The synergism of both acids was documented through batch and continuous studies. Tannic acid promotes cobalt dissolution by reducing insoluble Co³⁺ into soluble Co²⁺, while acetic acid is critical to improve the dissolution and stabilize the metals in the pregnant leach solution. Based on batch studies, the optimum conditions for metal recovery at room temperature are acetic acid 1 M, tannic acid 20 g/L, pulp density 20 g/L, and stirring speed 250 rpm (94% cobalt and 99% lithium recovery). The kinetic study shows that increasing temperature to 80 °C improves cobalt and lithium recovery from 65 to 90% (cobalt) and from 80 to 99% (lithium) within 4 h at sub-optimum condition (tannic acid 10 g/L). Kinetic modeling suggests the leaching process was endothermic, and high activation energy indicates a surface chemical process. For other metals, the pattern of manganese and nickel recovery trend follows the cobalt recovery trend. Copper recovery was negatively affected by tannic acid. Iron recovery was limited due to the weak acidic condition of pregnant leach solution, which is beneficial to improve leaching selectivity.

     

Improving Water Resistance of Soy-Based Adhesive by Vegetable Tannin

In this research tannic acid was used to prepare soy-based adhesives for making plywood and fiber board. The different resin formulations were analyzed by Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and its derivative as a function of temperature (DTG) and Fourier Transform Infra-red (FTIR) spectroscopy. The results showed that the addition of tannic acid to soy-based adhesive decreased soy-based adhesive viscosity and its pH. The DSC analysis showed that the denaturation temperature of soy-based adhesives decrease by adding tannic acid. The TGA and DTG curves showed that the thermal degradation of soy flour starts above 146 °C. The FTIR spectroscopy results also showed that the soy flour amino acids appeared to react well with tannic acid. Furthermore, delamination and shear strength test results showed the good water resistance of plywood bonded with soy-based tannic acid-modified adhesive. The mechanical and physical properties such as MOR, MOE, IB, and water resistance of fiberboard were improved, by adding tannic acid to the soy-based adhesive.     

Study on Biodegradable Starch/OMMT Nanocomposites for Packaging Applications

The thermoplastic starch (TPS) and nanocomposite(TPS/OMMT) was prepared with 15% carbamide, 15% ethanolamine and different contents of organic activated montmorillonite (OMMT) by twin-screw extruder with a 130 °C barrel temperature. Fourier transforms infrared spectroscopy and wide angle X-ray diffraction shown that the alkylamine in dodecyl benzyl dimethyl ammonium bromide could react with MMT via cation exchange reaction. After treated, the d(001)space distance of MMT increased from 1.5 to 1.7 nm. Scanning electron microscope revealed that the lower contents of OMMT could disperse well in the matrixes of TPS. The carbamide, ethanolamine and the OMMT could destroy the crystallization behavior of starch, but only the OMMT restrained this behavior for long-term storing. Mechanical properties investigation indicated that the tensile strength and modulus of TPS/OMMT nanocomposites were better than those of TPS, while the elongation at break was descended with the increasing of OMMT contents. When the content of OMMT was 4%, the tensile strength and modulus of TPS was improved from 4.2 and 42 MPa to 6.0 and 76 MPa, respectively.