Thermal and mechanical properties and water absorption of guanidine hydrochloride‐modified soy protein (11s)

Thermal and mechanical properties and water absorption of guanidine hydrochloride (GuHCl)‐modified 11S soy protein and molded plastics made from it were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), mechanical tests, and scanning electron microscopy (SEM). The DSC results showed that the denaturation temperature of GuHCl‐modified 11S solutions was higher than that of the control sample and the high concentration GuHCl completely denatured 11S. Nonfreezing water of the modified 11S solution exhibited a minimum value at 0.9M GuHCl. Both DSC and DMA results showed that GuHCl was a plasticizer of 11S and the glass transition temperature of modified 11S plastics decreased with increasing GuHCl concentration. Both the stress and strain of modified 11S plastics reached their highest values at a 0.9 GuHCl concentration. The SEM observations supported these results. A water‐absorption test showed an improvement in the water resistance of 11S plastics with GuHCl modification. The water absorption had a minimum value at 0.9M GuHCl. The interaction between GuHCl molecules and 11S protein was found to have important effects on the thermal and mechanical properties and the water absorption of 11S plastics. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1063–1070, 2000     

Thermal and mechanical properties and water absorption of sodium dodecyl sulfate‐modified soy protein (11S)

The thermal and mechanical properties and water absorption of sodium dodecyl sulfate (SDS)‐modified 11S soy protein and molded plastics made from it were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), mechanical tests, and scanning electron microscopy (SEM). The DSC results showed that both the temperature and enthalpy of thermal denaturation of modified 11S solutions decreased as the SDS concentration increased. Nonfreezing water of the modified 11S solution had a minimum value at 1.0% SDS. The ordered structure of SDS‐modified 11S protein was recovered and/or newly formed during the freeze‐drying process. Both DSC and DMA results showed that SDS was a plasticizer of 11S, and the glass transition temperature of modified 11S plastics decreased with increasing SDS concentration. Both the tensile strength and elongation of modified 11S plastics first decreased and then increased as the SDS concentration increased, and 5.0% SDS‐modified 11S plastic had the highest tensile strength and elongation. The SEM observations supported these results. A water‐absorption test showed a reduction in the water resistance of 11S plastics after SDS modification. The rate of water absorption increased with increasing SDS concentration. The hydrophobic interaction between SDS molecules and 11S protein was found to have important effects on the thermal and mechanical properties and the water absorption of 11S plastics. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 166–175, 2001     

Effects of lignin as a filler on properties of soy protein plastics. II. Alkaline lignin

Blend plastics based on soy protein isolate (SPI) strengthened with alkaline lignin (AL) in the weight ratio of 10:0 to 5:5 were prepared with 40 wt % glycerol as a plasticizer by compression molding. The structure and mechanical properties of the blends were investigated by wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamical mechanical thermal analysis (DMTA), and tensile tests. The results indicated that the introduction of AL could effectively increase the tensile strength and Young's modulus, thermal stability, and elongation of the compositive plastics when the AL content ranged from 10 to 20 parts. Moreover, the blend plastics containing 50 parts AL exhibited maximum tensile strength (1.98 MPa) and much higher than that with the SP–AL0 sheet with AL alone (0.89 MPa). In addition, tests of water absorption proved that the introduction of hydrophobic AL effectively reduced water absorption and, hence, decreased water sensibility. Therefore, AL, a relatively low‐cost filler, plays a major role in enhancing the strength and water resistivity of soy protein plastics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3291–3297, 2003     

Protein Subunit Composition Effects on the Thermal Denaturation at Different Stages During the Soy Protein Isolate Processing and Gelation Profiles of Soy Protein Isolates

This study focussed on the evaluation of thermal denaturation at three different stages during soy protein isolation and the effect of subunit composition on the formation of heat-induced soy protein gels. Soy protein isolates (SPI) were prepared from 12 high protein lines, Harovinton variety and 11 derived null-lines which lacked specific glycinin (11S) and β-conglycinin (7S) protein subunits. Protein denaturation during SPI processing was monitored by differential scanning calorimetry (DSC). The results showed that hexane extraction of oil from soybean flours at 23 °C or 105 °C did cause changes in protein conformation. Rheological measurements showed that lines with different subunit compositions and 11S:7S ratio had distinctive gelation temperatures and resulted in gels with different network structures. All lines formed particulate gels at 11% protein. The 11S:7S ratio was not correlated to final stiffness, measured as the storage modulus G′, of SPI gels. Lower gelation temperatures were usually observed for 7S-rich lines. The absence of A3 and the combination of A1, A2 and A4 subunits of 11S fraction may suggest the formation of stiffer gels. A more detailed study of the frequency dependence of G′ for the various networks formed also indicated that differences in subunit composition influenced the network structures.     

Preparation of a new dialdehyde starch derivative and investigation of its thermoplastic properties

In order to obtain thermoplastic starch plastics with improved properties, a novel method of starch modification was developed in this study. Starch derivatives were prepared using the following procedures: pea starch was first oxidized to make dialdehyde starch (DAS) by sodium periodate under mild conditions, and this was then acetalized with glycol to give Gly-ADS. The modified starch was characterized by FT-IR, ¹H-NMR, TG, DSC, and XRD. The TG curves indicated that the thermal stability of Gly-ADS was better than that of DAS. The glass transition temperature of Gly-ADS with 95% carbonyl content (Gly-ADS95) was 97 °C by DSC. Although the intrinsic viscosity of DAS was less than that of pea starch, thermoplastic Gly-ADS (TPGly-ADS) exhibited good mechanical properties. The influence of moisture absorption on the mechanical properties of TPGly-ADS was also investigated. The results showed that TPGly-ADS possesses improved water resistance: the highest moisture absorption of TPGly-ADS95 was about 11%, and the tensile strength and the elongation at break were 18.1–14.6 MPa and 5.3–18%, respectively.     

Thermal properties and adhesion strength of modified soybean storage proteins

Soy proteins have shown great potential for adhesive and resin applications. This investigation characterized the thermal and adhesive properties of the major soy protein components conglycinin (7S) and glycinin (11S) after chemical modification. These globulins were extracted from defatted soy flour, then modified with either sodium hydroxide, sodium dodecyl sulfate (SDS), or urea. Modified 7S, 11S, and mixtures of 7S and 11S at varying ratios were evaluated for gluing strength with cherry veneer plywood and for thermal denaturation using DSC. Adhesive strength and water resistance were significantly improved for all proteins modified with sodium hydroxide. Gluing strength and water resistance were improved for SDS- and ureamodified proteins containing greater portions of 7S globulins. The opposite behavior was observed for proteins containing large amounts of 11S globulins. DSC results showed that the temperatures of denaturation (T _d ) decreased for the proteins modified with sodium hydroxide or urea, whereas the T _d values of proteins modified with SDS were similar to the unmodified proteins. These results suggested that, at the concentrations studied, sodium hydroxide or urea could denature soybean protein more effectively than SDS, resulting in lower protein thermal stability. Soybean proteins with high ratios of 11S had more ordered structures, as evidenced by the high enthalpy values of protein denaturation observed in DSC measurements.     

Effects of moisture content and heat treatment on the physical properties of starch and poly(lactic acid) blends

Starch, a hydrophilic renewable polymer, has been used as a filler for environmentally friendly plastics for about 2 decades. Starch granules become swollen and gelatinized when water is added or when they are heated, and water is often used as a plasticizer to obtain desirable product properties. The objective of this research was to characterize blends from starch and poly(lactic acid) (PLA) in the presence of various water contents. The effects of processing procedures on the properties of the blends were also studied. Blends were prepared with a lab‐scale twin‐screw extruder, and tensile bars for mechanical testing were prepared with both compression and injection molding. Thermal and mechanical properties of the blends were analyzed, and the morphology and water absorption of the blends were evaluated. The initial moisture content (MC) of the starch had no significant effects on its mechanical properties but had a significant effect on the water absorption of the blends. The thermal and crystallization properties of PLA in the blend were not affected by MC. The blends prepared by compression molding had higher crystallinities than those prepared by injection molding. However, the blends prepared by injection molding had higher tensile strengths and elongations and lower water absorption values than those made by compression molding. The crystallinities of the blends increased greatly with annealing treatment at the PLA second crystallization temperature (155°C). The decomposition of PLA indicated that PLA was slightly degraded in the presence of water under the processing temperatures used. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3069–3082, 2001     

Effects of molding temperature and pressure on properties of soy protein polymers

Because of the worldwide environmental pollution problem with petroleum polymers, soy protein polymers have been considered as alternatives for biodegradable plastics. The objective of this research was to study the curing behavior of soy protein isolates (SPIs) for that application. The molding variables of temperature, pressure, and time and curing quality factors of tensile strength, strain, and water resistance were evaluated. The maximum stress of 42.9 MPa and maximum strain of 4.61% of the specimen were obtained when SPI was molded at 150°C and 20 MPa for 5 min. The water absorption of the specimen decreased as molding temperature and time increased. Glycerol greatly improved the flexibility of the specimen but decreased its strength. For SPI with 25% glycerol added, the maximum stress and strain of about 12 MPa and 140%, respectively, were achieved when the specimen was molded at 140°C for 5 min. Molding temperature, pressure, and time are major parameters influencing the curing quality of soy protein polymers. At fixed pressure, the molding temperature and time had significant interactive effects on curing quality. At high temperature (e.g., at 150°C) it took about 3 min to reach optimum curing quality; however, at low temperature (120°C) it took about 10 min to reach optimum curing quality. The maximum strength and strain of the cured protein polymer occurred at the molding temperature close to its phase transition temperature or about 40°C below its exothermic temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2595–2602, 1999     

Effects of steaming on soybean proteins and trypsin inhibitors

Steaming of defatted soybean flakes decreases both protein solubility and trypsin inhibitor (TI) activity as measured by nitrogen solubility index (NSI) and TI assay, respectively. NSI can be Iowered from 80–90, in raw flakes, to 10–20 with sufficient steaming. Concurrently, about 90% of TI activity is destroyed. Differential scanning calorimetric (DSC) analysis of raw soy flour demonstrated transition temperatures (T_max) of 58.2, 72.8 and 96.4°C for TI, 7S and 11S proteins, respectively. Lowering the NSI to 42.4 by steaming caused the TI transition to disappear, even though half of the TI activity remained. DSC analysis of steamed soybean flakes revealed that undenatured 7S and 11S storage proteins remain, even when the NSI is decreased to 10.     

Fractionation of Soybean Globulins Using Ca<Superscript>2+</Superscript> and Mg<Superscript>2+</Superscript>: A Comparative Analysis

The substitution of CaCl₂ by MgCl₂ was undertaken in Deak’s two-step process of separating the soybean 11S and 7S globulins, aiming at higher purities and lower phytic acid (PA) contents of recovered protein fractions. The effects of pH and the addition of NaCl were also evaluated. Compared with CaCl₂, MgCl₂ reduced the PA content of the 11S-rich fraction by 63–71% but increased that of the 7S-rich fraction by 14–28%, depending on pH. Correspondingly, more Ca²⁺ was recovered in the 11S-rich fraction, while more Mg²⁺ co-precipitated with the 7S-rich fraction. NaCl increased the purity of the 11S-rich fraction and reduced its PA content, but the purity of the 7S-rich fraction was reduced by using 50–100 mM NaCl. Lowering pHs from 6.4 and 4.8 to 5.6 and 4.0 in the two precipitation steps increased the yield of both fractions. The optimized fractionating procedure was as follows: the 11S-rich fraction was precipitated at pH 5.8 by using 5 mM MgCl_2, 10 mM NaHSO₃ and 20 mM NaCl, followed by the precipitation of the 7S-rich fraction at pH 4.5. The new method provided both fractions with satisfactory protein yields (22% for 11S and 16% for 7S), purities (88% for 11S and 80% for 7S) and PA contents (0.356% for 11S and 0.882% for 7S).     

PhMI-St-AN耐热改性剂的合成及与PVC的共混发泡

采用悬浮共聚合法制备N-苯基马来酰亚胺-苯乙烯-丙烯腈(PhMI-St-AN)三元共聚物耐热改性剂,将其与聚氯乙烯(PVC)共混通过模压发泡制备了PVC/PhMI-St-AN泡沫塑料。借助傅里叶变换红外光谱、差示扫描量热分析等手段对PhMI-St-AN三元共聚物进行了表征,研究了共聚物组成对三元共聚物玻璃化转变温度(Tg)及其与PVC相容性的影响,考察了PVC/PhMI-St-AN泡沫塑料的热尺寸稳定性和吸水性。结果表明,PhMI-St-AN具有良好的耐热性能,其Tg随PhMI含量的增加而提高,PhMI-St-AN三元共聚物提高了PVC/PhMI-St-AN泡沫塑料的热尺寸稳定性,降低了吸水率。     

Processable high Tg high strength fluorinated new poly(arylene ether)s containing imido aryl group

A series of poly(arylene ether)s ( 7a–7f ) were successfully synthesized by aromatic nucleophilic substitution reactions of imidoaryl biphenol (5), 4,9‐bis‐(4‐hydroxy‐phenyl)‐2‐phenyl‐benzo[f]isoindole‐1,3‐dione with six different trifluoromethyl substituted bisfluoro monomers ( 6a–6f ). The weight‐average molar masses of the polymers were up to 280 kD as measured by GPC. These poly(arylene ether)s exhibited glass transition temperatures up to 361°C in DSC. These polymers showed very high thermal stability up to 558°C for 10% weight loss under synthetic air in TGA. Except 7d–7f, remaining polymers 7a–7c were soluble in a wide range of organic solvents. Transparent thin films of these polymers cast from DCM or NMP exhibited tensile strengths up to 75 MPa and elongation at break up to 41% depending on their exact repeating unit structures. These poly(arylene ether)s showed cut‐off wavelength in between 400 and 450 nm except 7d and water absorption were in the range of 0.4 to 0.6%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Oilseed Meal Based Plastics from Plasticized, Hot Pressed Crambe abyssinica and Brassica carinata Residuals

With the increased use of plant oils as sustainable feedstocks, industrial oilseed meal from Crambe abyssinica (crambe) and Brassica carinata (carinata) can become a potential source for oilseed meal based plastics. In this study, crambe and carinata oilseed meal plastics were produced with 10–30 % glycerol and compression molding at 100–180 °C. Size exclusion HPLC was used to relate tensile properties to changes in protein solubility and molecular weight distribution. By combining glycerol and thermal processing, increased flexibility has been observed compared to previous work on unplasticized oilseed meal. Tensile results varied from a brittle crambe based material (10 % glycerol, 130 °C), Young’s modulus 240 MPa, strain at maximum stress of 2 %, to a soft and flexible carinata based material (30 % glycerol, 100 °C), Young’s modulus 6.5 MPa, strain at maximum stress of 13 %. Strength and stiffness development with increasing molding temperature is in agreement with the protein profiles obtained. Thus, the highest mechanical parameters were obtained at the protein solubility minimum at 140 °C. Higher temperatures caused protein degradation, increasing the level of low molecular weight extractable proteins. In carinata based materials the strain at maximum stress decreased as the protein aggregation developed. Results presented indicate that both crambe and carinata oilseed meal based materials can have their properties modulated through thermal treatment and the addition of plasticizers.     

Effect of thermal history on properties of block-copolyetheresters with poly(tetramethylene 2,6-naphthalenedicarboxylate) segments

The effect of compression molding on the thermal transitions and crystalline properties of block-copolyetheresters with hard segments of poly(tetramethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were investigated by differential scanning calorimetry (DSC), X-ray diffraction, thermal stimulated current (TSC), and dynamic mechanical analysis (DMA). The X-ray diffraction patterns of compression molded samples of the block-copolymers were considerably different from those of the corresponding samples with slow-cooling history. After compression molding, the diffraction peaks were changed completely indicating a different crystalline structure for the polyester segments, and the diffraction peaks became sharper indicating a higher crystallinity. The DSC results also showed that the melting point and crystallinity of the polyester segments were increased after compression molding. The glass transition temperatures of the polyether soft phase and polyester hard phase also were determined by DSC, TSC, and DMA separately with consistent data and were found to be dependent on the content of polyether segments and the molecular weight of the poly(tetramethylene ether)glycol (PTMEG) used. A γ-transition was observed by TSC and DMA and seemed to be independent of the composition and the thermal history. The glass transition temperatures of the polyether soft phase and the polyester hard phase of the block-copolymers derived from PTMEG 650 and PTMEG 1000 shifted to a lower temperature after compression molding possibly because of the partial miscibility between the comprising segments in these two series. The abrupt drop in log G′ in the temperature range of −10–15°C for the block-copolymers derived from PTMEG 2000 was caused by the melting of the polyether segments and indicated that the crystalline properties of the polyether segments could affect their mechanical properties. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1441–1449, 1999     

Monitoring of Carbon Fiber/Polyamide Composites Processing by Rheological and Thermal Analyses

The use of continuous carbon fiber reinforced thermoplastic composites in the aerospace and automotive fields has increased due to their high performance. The hot compression molding process for the manufacture of the composites has attracted much interest due mainly to the high rate of production and quality of the finished parts. This work involves the use of rheological and thermal analyses for the optimization of the processing parameters related to the manufacture of carbon fabric/polyamide 6 and 6/6 by hot compression molding. The results show that the most adequate processing temperatures to be used in the hot compression molding are 250°C and 290°C for polyamides 6 and 6/6, respectively. The loss moduli value (G″) from DMA increased with the increment of the carbon fiber content in the glass transition temperatures, due to the reinforcement contribution. Therefore, the glass transition temperatures of all samples remained constant. The use of the established parameters based on the DSC, DMA, and rheological analyses favored the manufacture of composites with a homogeneous distribution of reinforcement and matrix as observed through optical microscopy analyses.     

Properties of molded soy protein isolate plastics

Thermal property of soy protein isolates (SPI) was studied with differential scanning calorimetry and thermogravimetric analysis. The weight loss of pure SPI is about 300°C. The glass transition temperature (T_g) is above 200°C. The best molding temperature of glycerin plasticized SPI plastics were then given. It is between 125 and 140°C. Subsequently the special property of molded SPI plastics was investigated. Results show that the atmosphere humidity affects the mechanical property and thermal property of SPI plastics. With the increasing humidity, the tensile strength decreases. While the elongation at breakage and peak area of the differential scanning calorimetry curve increases. At high temperature even at 140°C the molding temperature SPI plastics still have tensile strength though it decreases with the increasing test temperature while elongation at breakage increases. Dynamic mechanic thermal analysis test show that the storage modulus decreases with the rising temperature. The mechanical loss peak appears at lower temperature with the increasing amount of glycerin content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Plasticization of soy protein polymer by polyol-based plasticizers

Soy protein isolate (SPI) was mixed with four polyol-based plasticizers and molded into plastics using a hot press. The plasticized SPI powder was evaluated for denaturation temperatures and denaturation enthalpies. The SPI plastics were studied for mechanical properties, glass transition temperatures, storage modulus, morphology, and water absorption. Thermal properties of the SPI plastics with propylene glycol were depressed to the largest degree, and the plastics with glycerol showed the largest strain at break, whereas plastics with 1,3-butanediol gave the highest tensile strength. The morphology of the fractured surface on the SPI plastics changed from brittle fracture for the unplasticized SPI to ductile fracture for the plasticized SPI. Water absorption of all the plasticized SPI plastics was lower than that of the unplasticized SPI plastics.     

Ways of strengthening biodegradable soy‐dreg plastics

Biodegradable plastics (GSD) based on soy dreg (SD) were prepared by compression‐molding, with glycerol as the plasticizer and glutaraldehyde (GA) as the cross‐linker. The structure and properties of the GSD sheets were investigated by Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), scanning electron microscope (SEM), and tensile test methods. The results indicate that when GA content was 6.8%, the tensile strength (σ_b) of the sheet reached the maximum value of 14.5 MPa. Moreover, the strength and water resistance of the sheets coated with castor‐oil‐based polyurethane/nitrochitosan interpenetrating network (IPN) coating were significantly enhanced to 24.6 MPa in the dry state and 9.8 MPa in the wet state. Simultaneously, the test of biodegradability of the GSD sheet in a mineral salts medium containing microorganisms and agar proved that GSD could be fully biodegradable. This work has provided a novel way to utilize low‐cost SD to prepare biodegradable plastics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 422–427, 2003     

A Study on Subunit Groups of Soybean Protein Extracts under SDS-PAGE

Protein extracts of 640 soybean cultivars and landraces, mainly from China and a few from the US, were analyzed for their components and subunits based on distribution patterns of bands with varying molecular weights (MW) under SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). The number and molecular weight of the bands in SDS-PAGE varied among materials and showed a tendency of continuous distribution. Accordingly, the SDS-PAGE patterns of the soybean protein extracts were divided into two regions: the region of bands with MW < 44 KDa and that with MW ≥ 44 KDa. The first region containing mainly 11S proteins was divided into four parts, called subunit groups, i.e. 11S-1 (14.4–22 KDa), 11S-2 (22–26 KDa), 11S-3 (26–34 KDa) and 11S-4 (34–44 KDa). The second region containing mainly 7S protein was divided into six subunit groups, i.e. 7S-1 (44–49 KDa), 7S-2 (49–55 KDa), 7S-3 (55–67 KDa), 7S-4 (67–73 KDa), 7S-5 (73–82 KDa) and 7S-6 (82–91 KDa). The sum of relative contents of 11S-1–11S-4 was obtained as the relative content of 11S protein, those of 7S-1–7S-6 as that of 7S protein, and therefore, the 11S/7S ratio obtained. The proposed criteria were demonstrated to be simple, stable and feasible. Among the 640 tested materials, 39 lacked 11S-1 but none lacked the other 11S subunit groups, while deficiencies existed in all the six subunit groups of 7S, indicating a great potential for the genetic variation of protein components and subunits for breeding for the improvement of protein qualities.     

Investigation on odd‐odd nylons based on undecanedioic acid: 1. Synthesis and characterization

A series of odd‐odd polyamides were prepared through step‐heating melt‐polycondensation of undecanedioic acid with various diamines. The synthesized nylons were characterized comprehensively by means of elemental analysis, fourier‐transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), Raman spectra, intrinsic viscosity, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The intrinsic viscosities of the prepared polyamides except nylon 3 11 are 0.70 to 0.87 dl g^?1. The melting temperatures of the odd‐odd nylons range from 182 to 209 °C. In addition, the thermal mechanical properties of nylons 5 11, 7 11, 9 11 and 11 11 were analyzed using dynamic mechanical analysis (DMA). Nylon 3 11 could not undergo DMA due to its low molecular weight. The glass transition temperatures obtained from DMA are in the range 22–39 °C. Copyright © 2004 Society of Chemical Industry