Effect of silk protein fibers on properties of thermoplastic rice starch

Biodegradable polymer was prepared as thermoplastic starch (TPS). Due to poor mechanical properties and high water absorption of TPS, thermoplastic rice starch (TPRS) was modified by reinforcing with natural silk protein fibers, as an alternative choice of fiber reinforcement. Different contents and lengths of silk fibers were varied and used as the reinforcement. Internal mixer and compression molding machine were used to mix and shaped the TPRS/silk composites. It was found that stress at maximum load and Young??s modulus of the TPRS/silk composites significantly increased with the incorporation of silk fibers. Water absorption of the TPRS/silk composites was also dropped by the addition of silk fibers. Moreover, thermal degradation temperatures of the TPRS/silk composites shifted to higher temperatures by the inclusion of the silk fibers. Functional group analysis and X-ray diffraction patterns were analyzed by FI-IR and XRD techniques, respectively. Furthermore, color measurement, morphology and biodegradation by soil burial test were carried out for different TPRS/silk composites.     

Influence of the draw ratio on the mechanical properties and electrical conductivity of nanofilled thermoplastic polyurethane fibers

Electrically conducting textile fibers were produced by wet-spinning under various volume fractions using thermoplastic polyurethane (TPU) as a polymer and carbon black (CB), Ag-powder, multi-walled carbon nanotubes (MWCNTs), which are widely used as electrically conducting nanofillers. After applying the fiber to the heat drawing process at different draw ratios, the filler volume fraction, linear density, breaking to strength, and electrical conductivity according to each draw ratio and volume fraction. In addition, scanning electron microscopy (SEM) images were taken. The breaking to strength of the TPU fiber containing the nanofillers increased with increasing draw ratio. At a draw ratio of 2.5, the breaking to strength of the TPU fiber increased by 105 % for neat-TPU, 88 % for CB, 86 % for Ag-powder, and 127 % for MWCNT compared to the undrawn fiber. The breaking to strength of the TPU fiber containing CB decreased gradually with increasing volume fraction, and in case of Ag-powder, it decreased sharply owing to its specific gravity. The electrical conductivity of the TPU fiber containing CB and Ag-powder decreased with increasing draw ratio, but the electrical conductivity of the TPU fiber containing MWCNT increased rapidly after the addition of 1.34 vol. % or over. The moment when the aggregation of MWCNT occurred and its breaking to strength started to decrease was determined to be the percolation threshold of the electrical conductivity. The heat drawing process of the fiber-form material containing the anisotropic electrical conductivity nanofillers make the percolation threshold of the electrical conductivity and the maximum breaking to strength appear at a lower volume fraction. This is effective in the development of a breaking to strength and electrical conductivity.     

Multivalent carboxylic acids to modify the properties of zein

Methods must be developed to improve both the processability and physical properties of zein-based articles. Typical plasticizing agents that improve processability have a negative impact on physical properties at elevated humidities. Continued efforts must be employed to discover improved plasticizers. Carboxylic acids having more than one carboxylic acid moiety have been evaluated in zein melt formulations produced in a torque rheometer. These reagents were effective plasticizers for zein, lowering zein viscosity, and delaying the onset of rapid viscosity increase. These reagents altered viscosity differently than the traditional plasticizers such as triethylene glycol. These additives also lowered the tensile strength (TS) of zein formulations at 50% RH. Surprisingly, TS at 70% RH was higher than that at 50% RH at elevated levels of these additives. NMR analysis of Soxhlet extracted samples showed that these multivalent carboxylic acids do not cross-link the zein under the reaction conditions employed.     

Thermoplastic starch modified during melt processing with organic acids: The effect of molar mass on thermal and mechanical properties

Thermoplastic starch (TPS) was modified with ascorbic acid and citric acid by melt processing of native starch with glycerol as plasticizer in an intensive batch mixer at 160 °C. It was found that the molar mass decreases with acid content and processing time causing the reduction in melting temperature (T_m). As observed by the results of X-ray diffraction and DSC measurements, crystallinity was not changed by the reaction with organic acids. T_m depression with falling molar mass was interpreted on the basis of the effect of concentration of end-chain units, which act as diluents. FTIR did not show any appreciable change in starch chemical compositions, leading to the conclusion that the main changes observed were produced by the variation in molar mass of the material. We demonstrated that it is possible to decrease melt viscosity without the need for more plasticizer thus avoiding side-effects such as an increase in water affinity or relevant changes in the dynamic mechanical properties.     

Effects of plasticizer on the mechanical properties of kenaf/starch bio-composites

Research and development of biodegradable bio-composite can replacement the synthetic polymer materials, which is used for automobile interior materials, finishing materials of air conditioner and refrigerator. To develop both components as biodegradable bio-composite, this research used natural polymer starch as matrix and kenaf fiber as a filler. Various plasticizer(polyvinyl alcohol, polyethylene glycol, glycerol) were added and examined the mechanical properties of the kenaf/starch bio-composites according to these plasticizer. The kenaf bast which cultivated in Korea was retted with 2 % NaOH solution. The plasticizer weighting 10 % of that of matrix was added. kenaf/starch composites were molded with hot press for 30 minutes at 130 °C and 3,500 PSI molding condition. The mechanical properties such as tensile strength, elongation, and young modulus of the kenaf/starch composites were measured. Also, we measured the SEM cross-section images in order to investigate interfacial adhesion properties of fractured surfaces. The order of strength size of composites were G (12.42 MPa) > PVA (9.72 MPa) > PEG (4.73 MPa) samples respectively. The tensile strength of PEG sample is lower than the control sample (5.40 MPa).     

压力喷雾干燥系统在速溶茶粉生产中的应用

以CGYP01—500型立式压力喷雾干燥系统在速溶茶粉生产中的应用为例,介绍目前国内喷雾干燥系统的选择、确定、应用及生产中常见问题的处理。速溶茶粉密度小、易吸潮,单级滤袋或旋风捕粉的压力喷雾干燥系统在速溶茶粉生产中尚存在不足,两级捕粉式的压力喷雾干燥系统在速溶茶粉生产中应用效果较好。     

Preparation and characterization of cellulose nanofiber reinforced thermoplastic starch composites

In the present study, cellulose nanofibers composite films were manufactured based on thermoplastic starch. Nanofibers were extracted from rice straw employing a developed chemo-mechanical method. In the chemical step, almost all of non-cellulosic components were removed and a white pulp of cellulose microfibers was obtained. Then, a diluted suspension of fibers was ultrasonicated to destruct intermolecular hydrogen bonds achieving nanofibers networks. Afterward, bio-nanocomposites were prepared by film casting. In order to study the effect of nanofibers content on the composite properties, the mechanical and dynamic mechanical properties, morphology, humidity absorption, and transparency of films were investigated. The yield strength and Young modulus of nanocomposites were satisfactorily enhanced compared to the pure thermoplastic starch film. The glass transition temperature of films was shifted to higher temperatures by increasing nanofibers contents. The uniform dispersion of the nanofibers was investigated using SEM images. The humidity absorption resistance of films was significantly enhanced by using 10 wt% cellulose nanofibers. The transparency of the nanocomposites was reduced compared to the pure starch films.     

Enhanced mechanical and thermal properties of carbon fiber composites with polyamide and thermoplastic polyurethane blends

In this article, we demonstrated the preparation of carbon-fiber-reinforced composites using a polyamide 6 (PA6)/thermoplastic polyurethane (TPU) blend, in which the addition of TPU resulted in superior mechanical performances and increased thermal stability. According to various characterization techniques, these results are attributed to an enhanced adhesion and a homogeneous dispersion of long-carbon-fibers (LCFs) with TPU sizing in blended polymer matrix. Above all, dynamic-mechanical thermal analysis (DMTA) measurements clearly show that the dynamic storage modulus (E') of the blend composites is increased by threefold with temperature ranges below and above the glass transition temperature. The presence of LCFs in TPU systems induces effective fiber orientation, exhibiting simultaneous improvements in the tensile strength, flexural strength, and thermal stability.     

Influence of citric acid and water on thermoplastic wheat flour/poly(lactic acid) blends. I: Thermal, mechanical and morphological properties

Wheat flour was plasticized with glycerol and compounded with poly(lactic acid) in a one-step twin-screw extrusion process in the presence of citric acid with or without extra water. The influence of these additives on process parameters and thermal, mechanical and morphological properties of injected samples from the prepared blends, was then studied.Citric acid acted as a compatibilizer by promoting depolymerization of both starch and PLA. For an extrusion without extra water, the amount of citric acid (2 parts for 75 parts of flour, 25 parts of PLA and 15 parts of glycerol) has to be limited to avoid mechanical properties degradation. Water, added during the extrusion, improved the whole process, minimizing PLA depolymerization, favoring starch plasticization by citric acid and thus improving phases repartition.     

高浓度大豆生防芽孢杆菌粉剂喷雾干燥微胶囊化工艺研究

确定了微胶囊材料麦芽糊精和阿拉伯胶与大豆生防芽孢杆菌AF67具有良好的生物相容性.应用正交试验确定了生防菌喷雾干燥过程中影响菌粉收率、存活率、含水量的主要因素,并建立多元指数模型.模型确定的最佳工艺条件为:进风温度170℃,进料速度10ml/min,芯材与填充荆配比为1:8,固型物含量25%,活菌数达2.1×1010cfu/g.经验证,该数学模型具有可靠性.     

Comparative investigation of molded thickness and surface density on the structures and mechanical properties of lightweight reinforced thermoplastic composites

Lightweight reinforced thermoplastic (LWRT) is a newly developed porous material. The low density, high rigidity, design flexibility and sound absorption of LWRT facilitate its application in the automotive industry. Fibers are bonded with a matrix and air is imported by deconsolidation, which is not only economical but also environmentally friendly. In this work, film stacking and non-woven methods were employed as the impregnation techniques to manufacture LWRT. The molded thickness and surface density of LWRT were varied to study their influences on the structures and mechanical properties. Different lengths of fibers in LWRT were selected and 7 % PP-g-MAH was added to the matrix and compared with unmodified matrix. The mechanical properties decreased with the increase in molded thickness and the decrease in surface density. With higher fiber length, the strength and stiffness increased, while the toughness exhibited a maximum value at 80 mm fiber length. The strength and stiffness of LWRT were also enhanced when 7 % PP-g-MAH was added.     

Properties of dry film lubricants prepared by spray application of aqueous starch–oil composites

Aqueous dispersions of starch–soybean oil (SBO) and starch–jojoba oil (JO) composites, prepared by excess steam jet cooking, form effective dry film lubricants when applied as thick coatings to metal surfaces by a doctor blade. This application method necessitates long drying times, is wasteful, requires the addition of sucrose to promote composite adhesion to the metal surface, and restricts the substrate geometry to planar surfaces. These issues represent important barriers to the commercialization of this aqueous biobased dry film lubricant technology. We now report an air-assisted spray method that uses readily available spray equipment to apply aqueous starch–oil composite dispersions as thin coatings (0.15–2.0 mg/cm²) to metal surfaces quickly and efficiently. Aqueous dispersions of waxy maize starch–oil composites containing either SBO, JO or hexadecane (HD), having 0.020–31.7 wt% oil relative to starch, were applied by air-assisted spraying and could be dried to the touch in approximately 30 s. Additionally, sucrose was found unnecessary for adhesion of the sprayed coatings. Tribological ball-on-flat testing of metal specimens spray coated with starch–SBO, –JO, and –HD composites showed the thin films of starch–SBO and –JO performed better at reducing the coefficient of friction (COF) than the starch–hexadecane composites. A low COF ranging between 0.027 and 0.044 was obtained for the starch–SBO and –JO composites containing 4–5 wt% oil relative to starch. Above 4–5 wt% oil loadings, no further COF reductions were realized. Further results revealed that micrometer-sized oil droplets embedded within the dried starch matrix of the composite film are delivered “on demand”. It appears that when pressure is applied to the dry film lubricant, the starch matrix ruptures and releases the entrained oil to the friction surface.     

Composite materials of thermoplastic starch and fibers from the ethanol-water fractionation of bagasse

The aim of this study was to evaluate the potential of the fibrous material obtained from ethanol-water fractionation of bagasse as reinforcement of thermoplastic starches in order to improve their mechanical properties. The composites were elaborated using matrices of corn and cassava starches plasticized with 30 wt% glycerin. The mixtures (0, 5, 10 and 15 wt% bagasse fiber) were elaborated in a rheometer at 150 °C. The mixtures obtained were pressed on a hot plate press at 155 °C. The test specimens were obtained according to ASTM D638. Tensile tests, moisture absorption tests for 24 days (20-23 °C and 53% RH, ASTM E104), and dynamic-mechanical analyses (DMA) in tensile mode were carried out. Images by scanning electron microscopy (SEM) and X-ray diffraction were obtained. Fibers (10 wt% bagasse fiber) increased tensile strength by 44% and 47% compared to corn and cassava starches, respectively. The reinforcement (15 wt% bagasse fiber) increased more than fourfold the elastic modulus on starch matrices. The storage modulus at 30 °C (E_30 °C′) increased as the bagasse fiber content increased, following the trend of tensile elastic modulus. The results indicate that these fibers have potential applications in the development of biodegradable composite materials.     

Properties of thermoplastic starch from cassava bagasse and cassava starch and their blends with poly (lactic acid)

Cassava bagasse is an inexpensive and broadly available waste byproduct from cassava starch production. It contains roughly 50% cassava starch along with mostly fiber and could be a valuable feedstock for various bioproducts. Cassava bagasse and cassava starch were used in this study to make fiber-reinforced thermoplastic starch (TPS_B and TPS_I, respectively). In addition, blends of poly (lactic acid) and TPS_I (20%) and TPS_B (5, 10, 15, 20%) were prepared as a means of producing low cost composite materials with good performance. The TPS and PLA blends were prepared by extrusion and their morphological, mechanical, spectral, and thermal properties were evaluated. The results showed the feasibility of obtaining thermoplastic starches from cassava bagasse. The presence of fiber in the bagasse acted as reinforcement in the TPS matrix and increased the maximum tensile strength (0.60 MPa) and the tensile modulus (41.6 MPa) compared to cassava starch TPS (0.40 and 2.04 MPa, respectively). As expected, blending TPS with PLA reduced the tensile strength (55.4 MPa) and modulus (2.4 GPa) of neat PLA. At higher TPS_B content (20%) the maximum strength (19.9 MPa) and tensile modulus (1.7 GPa) were reduced about 64% and 32%, respectively, compared to the PLA matrix. In comparison, the tensile strength (16.7) and modulus (1.2 GPa) of PLA blends made with TPS_I were reduced 70% and 51% respectively. The fiber from the cassava bagasse was considered a filler since no increase in tensile strength of PLA/TPS blends was observed. The TPS_I (33.1%) had higher elongation to break compared to both TPS_B (4.9%) and PLA (2.6%). The elongation to break increased from 2.6% to 14.5% by blending TPS_I with PLA. In contrast, elongation to break decreased slightly by blending TPS_B with PLA. Thermal analysis indicated there was some low level of interaction between PLA and TPS. In PLA/TPS_B blends, the TPS_B increased the crystallinity of the PLA component compared to neat PLA. The fiber component of TPS_B appeared to have a nucleating effect favoring PLA crystallization.     

Comparative study on sizing properties of amphoteric starch and phosphorylated starch for warp sizing

By varying the ratios of N-(3-chloro-2-hydroxypropl) trimethylammonium chloride and orthophosphate to starch, a series of amphoteric starch with different degree of substitution (DS) were prepared for evaluating sizing effect of amphoteric starch for cotton warps. The amphoteric starch contained quaternary ammonium and phosphate groups simultaneously, and was set to electric neutrality by varying relative quantity of anionic and cationic groups in order to prevent adverse effects of negative and positive charges. The influence of amphoteric modification of starch on the adhesion to cotton fibers was assessed by measuring tensile strength and work-to-break of slightly sized cotton roving and comparing the adhesion of amphoteric starch with those of phosphorylated one. Comparison on mechanical performances of amphoteric starch film over phosphorylated one was evaluated in terms of tensile strength, breaking extension and wear loss of starch film. The properties such as increase in tensile strength, loss in elasticity, abrasion resistance, and hairiness of cotton yarns sized with amphoteric starch were evaluated through control tests by the comparison with those of phosphorylated one. When zeta potential of amphoteric starch was set close to zero, the adhesion increased and the properties of sized yarns enhanced as the modification level increased. The amphoteric starch was evidently superior to phosphorylated one in improving the quality of sized cotton yarns. The amphoteric starch with neutral zeta potential and DS levels of 0.02–0.03 for quaternary ammonium groups and phosphate ones, respectively, could be applied to size cotton warp yarns for the improvement of yarn quality.     

Effects of gamma irradiation on starch granule structure and physicochemical properties of brown rice starch

In the present research effects of gamma irradiation (5–20 kGy) on the physicochemical, antioxidant and thermal properties of brown rice starch were studied. Scanning electron microscopy displayed mostly polyhedral shapes with no surface fractures. XRD displayed characteristic A type pattern and decrease in per cent crystallinity (22.53–20.41%) was observed as the dose increased from 5 to 20 kGy. DPPH % inhibition and FRAP values were increased in a dose dependent manner. Pasting properties (peak, final and setback viscosity) decreased with irradiation. Pasting temperature also significantly decreased with irradiation for all the irradiated starches. The transition temperatures, enthalpy of gelatinization, pH and apparent amylose content of starch decreased significantly with increase in irradiation dose.     

Influence of fibre contents on mechanical and thermal properties of roselle fibre reinforced polyurethane composites

The aim of this paper is to study the effect of fibre content on mechanical and morphological properties and thermal stability of roselle fibres (RFs) reinforced polyurethane (TPU) composites. The RF/TPU composites were prepared at difference fibre contents; 10, 20, 30, 40 and 50 wt% by melt mixed mixer and hot press at 170 °C. Mechanical (tensile, flexural and impact strength) and Thermogravimetric analysis (TGA) properties of RF/TPU composites were measured according to ASTM standard. Obtained results indicated that effect of fibre contents display improved tensile and flexural and impact strength properties. RF/TPU composites show the best mechanical and thermal properties at 40 wt% roselle fibre content. Scanning electron microscopy (SEM) micrograph of fractured tensile sample of the roselle composite revealed good fibre/matrix bonding. TGA showed that RF/TPU with difference fibre contents had improved thermal stability.     

Physical properties of cryomilled rice starch

Cryomilling of rice starch was evaluated as a non-chemical way to modify starch structure and properties. Cryomilling in a liquid nitrogen bath (63–77.2 K) was done to Quest (10.80% amylose) and Pelde (20.75% amylose) rice starch at five different time frames (0, 15, 30, 45, and 60 min). The viscosity of the cryomilled rice starch decreased significantly (p < 0.05) with increasing milling duration, including peak viscosity, hot-paste viscosity, cold-paste viscosity, breakdown, and consistency. Increasing milling time significantly increased (p < 0.05) water solubility index and water absorption index. Infra-red spectroscopy and X-ray diffraction crystallography both showed that the crystallinity of the cryomilled starch decreased with increasing milling time. Differential scanning calorimetry (DSC) analyses showed that after 60 min cryomilling there was partial loss of crystallinity (86% for Quest and 91% for Pelde) of both cryomilled starches. The cryomilling process modified the rice starch by causing a loss of crystallinity, that reduced its pasting temperature and increased water absorption, and by fragmentation of starch (probably the amylopectin fraction) that reduced the viscosity and increased solubility.     

Influence of variety and year of wheat cultivation on the chemical composition of starch and properties of glucose hydrolysates

The effect of chemical composition of starch samples derived from selected wheat cultivars harvested in different years (lipid content, amylose–lipid complex (AML) content, amylose concentration and the degree of starch damage) on physicochemical properties of glucose syrups produced from these starches was determined. It was found that glucose syrups obtained from the same wheat cultivar but harvested in different years displayed different physicochemical attributes such as concentration of reducing compounds, rate of filtration and coefficients of colour and transparency. Besides, the analyses showed that AML changed their form from amorphous to crystalline during enzymatic starch liquefaction by α-amylase. This in turn rendered starch less susceptible to enzymatic digestion and affected physicochemical features of glucose syrups. Presented results provide evidence that not only the total concentration of lipids and AML but also the AML polymorph present in starch hydrolysates (on completion of starch liquefaction) have an impact on quality of glucose syrups.