Soy Protein Isolate Resin Research Articles

Hybrid green composites using rice straw and jute fabric as reinforcement for soy protein-based resin

In this research, high amounts of the world's most wasted agricultural residue (rice straws) were utilized to produce hybrid green composites. Rice straws (RS) were needle-punched into jute fabric to form hybrid reinforcement mats which were impregnated with a soy protein isolate resin (SPR). Thermoset hybrid composites were produced at three different fiber contents of 40, 50, and 60% by wt. They were characterized for their tensile, flexural, interfacial, fractural, and hygroscopic properties. The hybrid composites with 40% fiber content enhanced Young's modulus (Ey) and ultimate tensile strength (TS) of the pure resin by 200% and 47%, respectively, compared to pure resin. With increasing fiber content, mechanical properties such as Ey, TS, flexural modulus, and flexural strength decreased, indicating insufficient resin volume. Interfacial shear strength values of RS/SPR and Jute/SPR were measured at 2.68 and 4.25 MPa, respectively. The high volumes of low-density RS and higher viscosity of the resin used in the hybrid composites seemed to overwhelm the resin's capacity to effectively wet the fibers. Insufficient wetting and low interfacial shear strength (IFSS) resulted in fiber pull-outs at fracture surfaces. Furthermore, as fiber content increased from 40 to 50 to 60%, moisture absorption increased from 10.4 to 12.9 to 22.6%, respectively. This is in spite of the fact that SPR was the most hydrophilic component of the three constituents. These results suggest that the high volumes of low-density fibers induce structural defects and exhaust the resin's wettability. Overall, the hybrid biodegradable composites had good tensile properties for use in packaging, transportation, housing, and furniture.

Dopamine-Mediated Pre-Crosslinked Cellulose/Polyurethane Block Elastomer for the Preparation of Robust Biocomposites.

The development of micro- and nanofibril cellulose to improve strength while reducing the side effects of toughness and water resistance can benefit integrated polymer performance. Inspired by the interior microstructure of mussel byssus, this paper proposed an efficient means of generating an active block microfibrillated cellulose/polyurethane elastomer using an epoxy monomer as a pre-crosslinked agent with the addition of a poly(dopamine) layer. The block elastomer served as a multifunctional crosslinker, constructing a covalent network and interfacial hydrogen bonding that interlinked the elastomer with a soy protein isolate (SPI) matrix. Compared with the pristine SPI film, the introduction of the block elastomer induced remarkable improvements in tensile strength and toughness (146.7 and 102.1%, respectively). Additionally, the block elastomer was employed to further estimate its reinforcing effect in SPI resin modification, which also exhibited favorable water resistance and adhesion performance. This strategy may provide a new approach for constructing superior elastomers to reinforce applicable biomass composites.

Fabrication and characterization of chitosan coated human hair reinforced phytagel modified soy protein-based green composite

AbstractIn the present investigation, human hair reinforced soy protein isolate (SPI)-based green composites modified with 40 wt.% phytagel and 12.5 wt.% glycerol were developed. Characterization of the prepared composites was done through water absorption, tensile test, scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). Composites having 2 wt.% of human hair fiber gave the optimum results for the tensile test. At 2 wt.% of human hair composition maximum tensile strength 17.23 MPa was obtained whereas the tensile strength of neat SPI was 8.54 MPa. SEM images show the interfacial bonding between human hair fiber and SPI resin and gave the clear explanation of the change in tensile strength and water absorption %. Chitosan coating was applied to fabricated composites to reduce water uptake. Chitosan coated sample showed considerable improvement in tensile strength, water uptake and glass transition temperature.

“Green” bio-thermoset resins derived from soy protein isolate and condensed tannins

The condensed tannins (CTs) have a similar catechol structure compared with mussel protein’s high water resistance structure, thus, CTs was used to mix with soy protein isolate (SPI) to develop a thermoset resin. Different pH condition was applied to catalyze the reaction of CTs and SPI. The chemical structure, thermal degradation behavior, fracture morphology, and physical characteristics of the resulting resins were tested. The resultant resin was applied on plywood fabrication and it wet shear strength was measured. Results showed that, in the acid condition, the catechol structure on B ring was protected and the active sites (C6 and C8) of A-ring reacted with functions and formed a crosslinking network with SPI, which effectively brought catechol into SPI. In the alkaline condition, the catechol structure on B ring of CTs was oxidized and formed an ortho-quinone to crosslink SPI and then formed a denser structure. This crosslinked structure formed by both ways improved the water resistance of the resultant resin, also, the structure led to a better thermostability and created a homogeneous fracture surface of the resin, which further increased the resin’s water resistance. The wet shear strength of the plywood bonded by the ac ST 2.5 and al ST 5 resin reached at 1.07 and 0.95MPa, which was a 75.4% and 55.7% higher than that of SPI resin. The resultant resins had favorable water resistance, suitable viscosity, cost-effective, and easy to handle, which were potential for industry application.

One-Step Toughening of Soy Protein Based Green Resin Using Electrospun Epoxidized Natural Rubber Fibers

Epoxidized natural rubber (ENR) fibers (ENRFs) were electrospun to obtain diameters ranging from a few hundred nanometers to a few micrometers by changing the ENR solution concentration. ENRFs were used to toughen soy protein isolate (SPI) based resin. A facile 1-step process was developed for wet electrospinning and blending the ENRFs directly into SPI resin. As the ENR concentration increased from 0.1% to 5%, the surface topography of ENRFs changed from irregular to somewhat bumpy. The average diameter of ENRFs also increased from 250 nm to 17 μm. Increased ENRF (electrospun from 3% concentration) loading from 0 to 20% in SPI resin increased the fracture strain significantly from 1.7 to 18.8% and increased the toughness by a factor of 10. Interestingly, tensile strength and Young’s modulus decreased only slightly compared to the increase in the toughness. Cross-linking between the epoxy groups in ENR and amine and/or carboxylic groups in SPI as well as the high aspect ratio of the ENRFs contributed to i...

Effect of Protein Content in Soy Protein Resins on Their Interfacial Shear Strength with Ramie Fibers

Interfacial shear strength (IFSS) between ramie fiber and soy protein-based resins was investigated using the microbond technique. Three commercially available soy products: soy flour (SF), soy protein concentrate (SPC) and soy protein isolate (SPI) were processed into resins and their IFSS with a single ramie fiber (20–40 μm diameter) was determined. The IFSS increased with the protein content in the resins. The IFSS with SPI which contains 90% protein showed the highest value of 25.7 MPa, while the IFSS with SF which contains 53% protein and 32% carbohydrate showed the lowest value of 9.5 MPa. Effect of sorbitol, used to plasticize the soy resins, on the IFSS was also determined. With increase in sorbitol content, the adhesion strength of ramie fiber to soy protein resins decreased. With 30% sorbitol (on soy protein wt basis), the IFSS with SPI resin decreased by 63% while the IFSS with SPC resin and with SF resin decreased by 56% and 48%, respectively. The results suggest that the low molecular weight carbohydrates present in SF and SPC resins also act as plasticizer. A scanning electron microscope (SEM) and an electron microprobe analyzer (EMPA) were used to characterize the debonded surfaces of the fibers and map the residual resins on the fiber surface after the microbond tests.

Characterization of stearic acid modified soy protein isolate resin and ramie fiber reinforced ‘green’ composites

The effects of stearic acid on the physical, tensile, moisture, thermal and micro-structural properties of the soy protein isolate (SPI)-based resin have been investigated. Fully biodegradable, environment-friendly, unidirectional, ramie fiber reinforced ‘green’ composites were also successfully fabricated using SPI and stearic acid modified SPI (MSPI) resins and characterized for their tensile and flexural properties. The fiber/resin interfacial shear strength was characterized using microbond technique. The mechanical and thermal properties and moisture resistance of the MSPI resin were significantly better than the SPI resin. It was observed that part of the stearic acid crystallized in SPI resin and that the crystallizability was affected by the glycerol added as a plasticizer. The replacement of glycerol with stearic acid did not affect the fiber/resin interfacial interaction. The ramie/MSPI composites showed significantly better mechanical properties compared to ramie/SPI composites. While the Young’s modulus of ramie/MSPI composites was closer to the theoretically calculated values, both composites had lower values than predicted. The ramie fiber/MSPI resin composites may be used as ‘green’ composites for certain indoor applications.

Characterization of Phytagel® modified soy protein isolate resin and unidirectional flax yarn reinforced “green” composites

The mechanical properties and moisture resistance of the soy protein isolate (SPI) resin and flax yarn reinforced composites were improved significantly by incorporation of a poly-carboxylic acid based modifier, Phytagel®. SPI and Phytagel® were blended to form an interpenetrating network-like cross-linked complex. This complex showed significantly improved tensile and moisture properties as well as higher thermal stability as compared to the unmodified SPI resin. The incorporation of Phytagel® (40% w/w of SPI powder) in SPI resin and subsequent lowering of the amount of glycerol (from 30% to 12.5%) led to an overall 10-fold increase in the tensile fracture stress and a nine-fold increase in the Young's moduli of the SPI resin along with a seven-fold decrease in fracture strain. The dynamic mechanical properties such as storage and loss modulus of the modified resin increased and the glass transition temperature also increased by about 56°C. The unidirectional flax yarn reinforced composites were made using two modified resins with 20% and 40% Phytagel® contents. Both resins contained 12.5% glycerol. The composites fabricated using resin containing 20% Phytagel® showed significantly higher tensile and flexural moduli as well as fracture stress in the axial direction than the composites with resin containing 40% Phytagel®, which was higher than the SPI resin based composites. POLYM. COMPOS., 26:647–659, 2005. © 2005 Society of Plastics Engineers

Effect of soy protein isolate resin modifications on their biodegradation in a compost medium

This study presents the effect of Phytagel ® and stearic acid modification of soy protein isolate (SPI) based ‘green’ resins on their biodegradation in composting environment. The composting process was monitored for up to 10 weeks and the degradation of the resins was characterized by weight loss, attenuated total reflectance infrared spectroscopy, differential scanning calorimetry and sol–gel analysis. The changes in the resin surface topography and microstructure during composting were also characterized using scanning electron microscopy (SEM). The gel fraction in SPI resin reduced significantly as a function of composting time indicating its fast degradation within 21 days. The stearic acid modified SPI resin (SAM-SPI) degraded at a slower rate than the SPI resin and Phytagel ® modified SPI (PM-SPI) resin degraded at the slowest rate. Based on the spectroscopic analysis and differential scanning calorimetric studies, it was found that stearic acid was among the main residue in the case of SAM-SPI resin after composting and Phytagel ® in the case of PM-SPI resin. The results of this study suggest that the biodegradation and hence, the service life of the SPI based resins can be controlled by changing the concentration of stearic acid or Phytagel ® in the SPI resin.

Thermal and mechanical properties of environment-friendly ‘green’ plastics from stearic acid modified-soy protein isolate

Most plastics, at present, are petroleum-based and do not degrade over many decades under normal environmental conditions. As a result, efforts towards developing environment-friendly and biodegradable ‘green’ plastics for various commercial applications have gained significant momentum in recent years. Soy protein isolate (SPI)-based ‘green’ plastics have been shown to suffer from high moisture sensitivity and low strength. These properties have limited their use in most commercial applications. They are also difficult to process into sheets without any plasticizer. The commonly used plasticizer, glycerol, tends to leach out over time producing time-dependent properties, which is highly undesirable for commercial applications. The objectives of the current research are to reduce the moisture sensitivity and simultaneously improve the tensile properties of SPI by incorporation of stearic acid without affecting its biodegradability. The effect of stearic acid and glycerol on the tensile and thermal properties of SPI has been characterized using various techniques to determine the interaction mechanisms between stearic acid and soy protein. Mechanical properties were characterized using Instron tensile tester. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD) techniques have been used to determine the effects of stearic acid and glycerol on the surface chemistry, thermal transitions and thermal degradation of the stearic acid modified SPI plastic (resin). The tensile test results show that Young’s modulus increased on increasing the stearic acid content, reaching the maximum value at about 25% (by weight of SPI powder) stearic acid. Further increase in stearic acid content from 25 to 30% led to a reduction in Young’s modulus. The moisture content, fracture stress, strain, and energy at break decreased steadily on increasing the stearic acid from 0 to 30% for SPI containing 30% glycerol. At 25% stearic acid content, the modulus and the fracture stress increased significantly, whereas the fracture strain, energy at break and the moisture content decreased on reducing glycerol content. Scanning electron microscopy photomicrographs of fractured surfaces showed a layered structure for stearic acid modified-SPI resin. TGA measurements showed that the thermal degradation of stearic acid modified-SPI resin initiated at higher temperature than the SPI resin. DSC scans indicated that stearic acid modified-SPI resin had a small degree of crystallinity, which was confirmed by X-ray diffraction patterns. Modifying SPI resin with stearic acid has been successful in obtaining better tensile and thermal properties as well as reduced moisture sensitivity without any processing problems.