Soy Protein Plastics Research Articles

Enhanced electrical and dielectric properties of plasticized soy protein bioplastics through incorporation of nanosized carbon black

AbstractConductive soy protein biocomposite plastics with high performance were fabricated with glycerol as plasticizer and nanosized carbon black (CB) as conductive filler. Adopting a pretreatment of the CB nanofiller, its dispersion, and interaction with matrix was improved. The results indicated the existence of strong hydrogen bonding between soy protein matrix and CB fillers, which improved the interfacial bonding. The strong interactions between CB and protein restricted the mobility of protein segments, resulting in a dramatical reinforcing effect for the CB filled composites and enhanced mechanical properties. Besides, the incorporation of CB into soy protein increased the thermal stability as well as the water resistance of the composites. Moreover, a low percolation threshold of 0.76 vol% and fine electrical conductivity were obtained for the bionanocomposites, resulting in improved electromagnetic interference shielding properties. This work provides a simple and green way for the preparation of conductive and electromagnetic interference shielding materials from natural polymers.

Preparation, Characterization and Antibacterial Evaluation of Soy Protein Isolate Biopolymeric Films Loaded with Nalidixic Acid

Glycerol plasticized soy protein isolate (SPI) films at different contents (1 to 5% w/w w.r.t SPI) of nalidixic acid (NA) were fabricated by solution casting method. SPI films and NA incorporated SPI films were structurally and mechanically characterized by Fourier transform infrared spectroscopy (FTIR) and mechanical properties, respectively. Thermomechanical and water uptake studies were also carried out for NA incorporated SPI films. The results from FTIR study indicated the presence of NA in SPI as evidenced by generation of two additional peaks at 1259 cm− 1 and 800 cm− 1 attributed to C–C stretching vibration and the deformation of the heterocyclic aromatic ring, respectively. At 4% NA, the tensile stress and tensile modulus of SPI films increased from 5.18 MPa to 8.57 MPa and 57.14 MPa to 93.90 MPa, respectively. Antibacterial activity of NA incorporated SPI films against E. coli and L. monocytogenes were studied. The antibacterial studies of NA incorporated SPI film showed the clear zone of inhibition against both the bacteria. Docking studies were performed for SPI in order to evaluate their binding affinity with NA and similar type of aromatic acids such as mandelic and benzilic acid with which SPI films have been prepared earlier by our group. After docking, the ligands in form of aromatic acids were evaluated according to their binding energy and the interaction pattern between SPI and aromatic acids. The docking results indicated that nitrogen containing heterocyclic ring moiety remained intact during interaction of SPI and NA. This work will be helpful in fabricating NA incorporated SPI film from the renewable resources with significant antibacterial properties and reasonable mechanical properties.

Intermolecular interactions and microstructure of glycerol-plasticized soy protein materials at molecular and nanometer levels

Glycerol plasticized soy protein is an important kind of biodegradable materials among the possible soy protein systems. Fully realized performance relies on the investigation and understanding of the molecular structure of the plasticized soy protein. However, the relevant research is primarily limited in the microstructure and physical properties of the mixtures with a lack of knowledge on the intermolecular interactions at molecular and nano-scale levels. In this work, intermolecular interaction and molecular motion of soy protein in glycerol plasticized systems were investigated at molecular and nanometer levels. Several techniques including atomic force microscope (AFM), transmission electron microscope (TEM) and 13C solid-state nuclear magnetic resonance (13C NMR), have been effectively employed. Observations from AFM and TEM indicated that the glycerol plasticized soy protein materials were heterogeneous at nanometer scale and there were two important phases existing in the materials, i.e. protein-rich domain and glycerol-rich domain. The protein-rich domain was composed of compact aggregations of pan-like protein while the glycerol-rich domain possessed a loose chain-like structure. Further studies on the interactions between soy protein and glycerol at molecular level using NMR indicated that the strong hydrogen bonds between glycerol and protein molecules was greatly affected by amino acid residues on protein chains. The protein-rich micro-domains were mainly composed of amino acids with long alkane lateral chains or aromatic ring lateral groups, while amino acids with polar groups or short nonpolar lateral groups formed glycerol-rich micro-domains. These results would be beneficial for the development and realization of plasticized soy protein based nanocomposites and blend materials with high performance.

Fabrication and Properties of Acid Treated Carbon Nanotubes Reinforced Soy Protein Nanocomposites

Acid treated multiwalled carbon nanotubes (MWNTs) were incorporated into glycerol plasticized soy protein to form MWNTs/soy protein nanocomposite plastics. The influence of the polar groups grafted on carbon nanotubes by acid treatment on the compatibility would be studied. The results showed that aggregation of carbon nanotubes was reduced by acid treatment and some polar groups were grafted on the nanotubes. The modified MWNTs were dispersed in soy protein matrix homogeneously and exhibited good compatibility with soy protein matrix. The crystalline structure of soy protein was not changed by MWNTs. The mechanical properties were dramatically enhanced through MWNTs incorporation due to the strong hydrogen bonding between them and the homogeneously dispersion of MWNTs in protein matrix, indicating the reinforcing effect of MWNTs in soy protein matrix. The water uptake was reduced and the thermal stability was enhanced by MWNTs incorporation.

Industrial trial of high-quality all green sizes composed of soy-derived protein and glycerol

All-green textile sizes with satisfactory weaving performance and biodegradability were developed from soy protein and glycerol, two major byproducts from soy-based biodiesel production. Polyvinyl alcohol has long dominated textile sizing chemical market due to its excellent sizing performance, despite its non-biodegradability. Efforts have been devoted to replace polyvinyl alcohol for a more sustainable textile industry. Recently, substitute size developed from soy protein after using high amount of petro-based triethanolamine showed acceptable sizing properties. However, triethanolamine was not an eco-friendly additive, due to its petroleum origin and non-biodegradability. In this research, glycerol was used to plasticize soy protein to develop all-green soy size. Glycerol interrupted hydrogen bonds in the soy globulin, allowing them to extend in the films. Resultantly, the soy size films possessed high stretchability and work of rupture. Lab-scale experiments and industrial weaving proved that the all-green soy size had similar or better weaving performance and remarkably better degradability, comparing to polyvinyl alcohol and triethanolamine plasticized soy protein size. For the first time, a possible logarithmic relationship was found between work of rupture of the size film and relative weaving efficiency.

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

ABSTRACTPhthalic 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.

Microstructure and properties of glycerol plasticized soy protein plastics containing castor oil

A series of glycerol-plasticized soy protein plastics containing castor oil were prepared by intensive mixing and hot pressing. The microstructure and properties of the resulting plastics were characterized with scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and mechanical tests. With small amount of castor oil incorporated (glycerol/oil ratio above 8:2), castor oil dispersed in the protein matrix homogeneously. At high concentrations, phase separation occurred. The adding of castor oil led to significant increase of storage modulus as well as glass transition temperatures attributed to glycerol-rich and protein-rich domains. Plastics containing castor oil exhibited improved tensile strength and Young’s modulus under high humidity (75% RH), compared with neat glycerol plasticized protein plastics. Especially, incorporation of low content of castor oil (glycerol/oil ratio=9:1) would result in the simultaneous enhancement of tensile strength, elongation at break and Young’s modulus. Increasing castor oil content also enhanced the thermal stability of the protein plastics.

Processing and properties of soy protein/silica nanocomposites fabricated in situ synthesis

Nanocomposite materials were prepared via glycerol plasticized soy protein as the matrix and in situ fabricated silica as thereinforcing phase. The silica nanoparticles were synthesized in the protein environment by sodium silicate as a precursor. The resulting composites were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), tensile tests, and thermogravimetric analysis (TGA). The results revealed that silica particles were homogeneously dispersed in soy protein matrix at a nanometer scale with low silica addition (lower than 15%). Silica particles exhibited a high adhesion with protein matrix through hydrogen bonding and confined the motions of soy protein segments. The incorporation of silica as a reinforcing agent significantly improved the mechanical properties and thermal stability of soy protein plastics.

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.

Effect of Co-Rotation and Counter-Rotation Extrusion Processing on the Thermal and Mechanical Properties, and Morphology of Plasticized Soy Protein Isolate and Poly(butylene succinate) Blends

Blends of plasticized soy protein isolate (PSPI) and poly(butylenes succinate) (PBS) were prepared in a 70:30 wt.-% ratio via co-rotation (CR) and counter-rotation (CTR) twin-screw extrusion. The novelty in this research suggests that CTR extrusion provides enhanced interfacial adhesion, tensile elongation and prolonged onset (Tonset) and end (Tend) thermal degradation temperatures. The average tensile strain at break showed to be ≈40% higher for PSPI-CTR material and ≈55% higher for PBS:PSPI-CTR (70:30) blends. Both Tonset and Tend for CTR processed PBS:PSPI(70:30) and PSPI were ≈10 °C greater than those of CR. These results suggest that the enhanced shear rate and radial motion associated with CTR allows for better destructurization and blending of PSPI within the PBS matrix, resulting in enhanced structural integrity due to the formation of possible amide and ester linkages. Scanning electron microscopy (SEM) provides further support based on evidence of reduced voids on the surface of all CTR blends

Structure and Properties of Soy Protein Plastics with ε-Caprolactone/Glycerol as Binary Plasticizers

We successfully prepared a series of soy protein isolate (SPI) plastics with e-caprolactone (CL)/glycerol binary plasticizers via extrusion and compression-molding. The chemical reactions among SPI, CL, and glycerol as well as the influence of CL/glycerol content on the microstructure, thermal degradation, and mechanical properties have been investigated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis-Fourier transform infrared spectroscopy (TGA-FTIR), and mechanical tests. The results of FTIR, SEM, DSC, and DMTA revealed that CL reacted with protein and glycerol molecules under high-temperature, high-shear, and high-pressure conditions. When the CL content was low (less than 25 wt %), the CL added to the protein matrix was dispersed mainly in the glycerol-rich domains and reacted with glycerol. However, at a higher concentration, the CL predominated in ...

Structure and properties of soy protein films plasticized with hydroxyamine

AbstractTwo kinds of transparent films of soy protein were successfully prepared by plasticizing with diethanolamine (DEA) and triethanolamin (TEA). The films were hot pressed at 140°C and 20 MPa, and characterized with Fourier transform infrared spectroscopy, scanning electron microscope, ultraviolet–visible spectrometer, differential scanning calorimetry (DSC), thermogravimetric analysis, and tensile testing. The results indicated that films with triethanolamine plasticizers possessed better optical transmittance (more than 80% at 800 nm) than those with diethanolamine and glycerol. All of the sheets exhibited only one Tg in DSC curves. Moreover, the soy protein plastics with TEA had higher thermal stability and mechanical properties, as well as lower water uptake than those with DEA and glycerol, as a result of the strong interaction between TEA and protein molecules. The soy protein materials will be promising for the application in the fields of package and container, substituting for the nongreen polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Properties of soy protein isolate/poly(vinyl alcohol) blend “green” films: Compatibility, mechanical properties, and thermal stability

AbstractBlend films from nature soy protein isolates (SPI) and synthetical poly(vinyl alcohol) (PVA) compatibilized by glycerol were successfully fabricated by a solution‐casting method in this study. Properties of compatibility, mechanical properties, and thermal stability of SPI/PVA films were investigated based on the effect of the PVA concentration. XRD tests confirm that the SPI/PVA films were partially crystalline materials with peaks of 2θ = 20°. And, the addition of glycerol will insert the crystalline structure and destroy the blend microstructure of SPI/PVA. Differential scanning calorimetry (DSC) tests show that SPI/PVA blend polymers have a single glass transition temperature (Tg) between 80 and 115.0°C, which indicate that SPI and PVA have good compatibility. The tension tests show that SPI/PVA films exhibit both higher tensile strength (σb) and percentage elongation at break point (P.E.B.). Thermogravimetric analysis (TGA) and water solubility tests show that SPI/PVA blend polymer has more stable stability than pure SPI. All the results reflect that SPI/PVA/glycerol blend film provides a convenient and promising way to prepare soy protein plastics for practical application. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Structure and properties of starch nanocrystal‐reinforced soy protein plastics

AbstractPea starch nanocrystals (StNs) were incorporated into a soy protein isolate (SPI) matrix to produce a class of full‐biodegradable nanocomposites. The StN with low loading level (2 wt%) showed a predominant reinforcing function, resulting in an enhancement in strength and Young's modulus. This was attributed to uniform dispersion of StN in the amorphous region of the SPI matrix, as well as maintaining stress of the rigid StN and transfer of stress mediated by interfacial interaction between the active StN surface and the SPI matrix. As a result, the nanocomposite containing 2 wt% StN had the maximum strength and Young's modulus in all the materials. With an increase in StN content, the number and the size of StN domains simultaneously increased due to a strong self‐aggregation tendency of StN. It lowered the effective active StN surface for interaction with the SPI matrix and destroyed the ordered structure in the SPI matrix, resulting in a gradual decrease of strength and Young's modulus. The introduction of relatively hydrophilic StN did not cause an obvious decrease of water resistance for any of the nanocomposites. The water uptake behavior of all the nanocomposites similar to that of neat SPI material was attributed mainly to the strong interfacial interaction between the StN filler and the SPI matrix. POLYM. COMPOS., 2009. Published by the 2008 Society of Plastics Engineers

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.

Modification of Soy Protein Plastic with Functional Monomer with Reactive Extrusion

Chemical modification of soy protein with monomers such as maleic anhydride, glycidyl methacrylate and styrene was accomplished using reactive extrusion technology. Thermal and mechanical properties of the modified soy protein plastics were characterized with differential scanning calorimetry (DSC), a dynamic mechanical analyzer (DMA) and a United Testing System load frame. It was found that the denaturation temperature and the glass transition temperature of soy protein plastic changed. In addition, the tensile properties of modified soy protein plastic improved. Attenuated total reflection Fourier transform infrared (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure of modified soy proteins. A suggestion of the interaction between soy protein and functional group in functional polymers is given. Through the in-situ interaction between the polymer and soy protein plastic, the mechanical properties of the soy protein plastic can be adjusted and controlled.

The Effect of Cornstarch Levels on the Surface Quality of Extruded Soy Protein Plastic

The ratio of soy protein isolate to cornstarch was studied in the extrusion of four different formulations of soy protein plastic in order to qualitatively examine the surface quality upon extrusion.Levels of glycerol and moisture were constant across all samples, and no other additives were used in the mixtures.Mixtures were made using a planetary mixer, and then extruded using a single-screw extruder equipped with a 10.16 centimeter sheeting die with a 0.152-centimeter opening.The surface of the extruded plastic became smoother with increasing starch content, but the processability became too difficult with very high starch levels.

Influence of different amides as plasticizer on the properties of soy protein plastics

AbstractA series of amide‐plasticized soy protein isolate materials were prepared by hot compression‐molding techniques at 140°C and 20 MPa. The plasticizing efficiency of amides was in the order of formamide > acetamide > acrylamide resulting from scanning electron microscopy, optical transmittance and differential scanning calorimetry. The results from torque rheology indicated that flowability and processability could be improved by adding amide as plasticizers. All of the sheets showed single glass transition temperature obtained by differential scanning calorimetry, indicating good compatibility between amide and soy protein. The water uptake of the plastics sheets and effects of moisture content on the thermal and mechanical properties were also investigated. The glass transition temperature and tensile strength decreased with an increase of moisture content in sheets. Formamide was considered as the best plasticizer of three amides because of the higher plasticizing efficiency and water resistance of SFm sheets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Soy protein plastics reinforced and toughened by SiO2 nanoparticles

AbstractThe nano‐SiO2 particles were compounded into soy protein isolated (SPI) matrix to produce a series of reinforcing nanocomposite sheets by compression‐molding. Except for the expected increase of strength and modulus, the elongation was also enhanced when the nano‐SiO2 content was lower than 8 wt %. Moreover, two nanocomposite materials were recommended: the one is a nanocomposite containing 4 wt % nano‐SiO2 with the highest strength and enhanced elongation, the other is a reinforced material with the best elongation filled by 8 wt % nano‐SiO2. The increase of nano‐SiO2 content produced many kinds of distributions in SPI matrix, such as single nanosphere, ∼ 100 nm nanocluster, interconnected network structure and great domain. Such structures strongly affected the mechanical performances of nanocomposite materials. The simultaneous enhancement of strength and elongation was related to homogeneous dispersion of nanoclusters while aggregated great domains severely decreased elongation in spite of obvious reinforcing effect. However, the reinforced materials with high loading of inorganic filler should be paid attention and have economic value to some extent in practical application. With the changes of nano‐SiO2 distribution, the structures of SPI matrix changed as well. After adding a mall amount of nano‐SiO2, the damage of glycerol plasticization to ordered structure of SPI was reduced. But as nano‐SiO2 content increased, the SPI microphase was separated from nano‐SiO2 domains. Furthermore, the condition of simultaneous reinforcing and toughening was put forward: the moderate aggregation of nano‐SiO2 as well as all kinds of strong interfacial interactions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Effect of coal filler on the properties of soy protein plastics

AbstractThe influence of ultrafine coal filler (UFC) content on tensile properties, water absorption, and biodegradability of soy protein plastics were investigated. The addition of UFC in the soy protein plastics, with different content of glycerol as a plasticizer, was at different ratio varying from 10:0 to 6:4. Blend sheets of the soy protein composites were prepared by the compression molding processing. The results show that, with 23.08 wt % glycerol, the tensile strength and elongation at break for the soy protein sheet with coal filler (range from 5 to 30 parts) can be enhanced as compared with nonfilled soy protein plastics. Water resistance of the soy protein plastics improves with the increase in UFC content. The derivative thermogravimetry (DTG) curves indicate a double‐stage degradation process for defatted soy flour (SPF), while three‐stage degradation process for soy plastics and the soy protein composites. FT‐IR, XPS, and SEM were applied to study the interfacial interaction between coal macromolecules and soy protein molecules in UFC filled soy protein plastics. The results demonstrated that there is strong interfacial interaction in the soy protein plastics caused by the compression molding processing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3134–3143, 2006