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191.
淀粉-醋酸乙酯-甲基丙烯酸甲酯接枝共聚物的合成及生物降解研究 总被引:15,自引:0,他引:15
用硝酸铈铵为引发剂,合成了淀粉 醋酸乙烯酯 甲基丙烯酸甲酯接枝共聚物,用质子核磁共振谱研究了接枝支链的化学组成,用X 射线粉末衍射研究了接枝共聚物的结晶结构变化,分别用实验室酶分解法和室外土壤掩埋法测定了接枝共聚物的生物降解性能,结果说明,仅接枝共聚物中的淀粉部分能被微生物降解,接枝支链部分不能被降解. 相似文献
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194.
以过硫酸铵(NH4)2S2O8为引发剂,失水山犁醇单月桂酸酯(Span-20)为乳化剂,采用反相乳液聚合技术,制得了淀粉-丙烯酸接枝共聚物,研究了反应温度、引发剂浓度、单体浓度、乳化剂浓度、淀粉用量五种因素对反应速率的影响。根据单体的转化率,用线性回归法计算聚合反应速率;然后用作图法确定反应的动力学关系式,并求出反应起始阶段的表观活化能。结果表明,其动力学关系式为:Rp∝[(NH4)2S2O8]0.51[AA]1.18[St]0.81[Span-20]0.62;聚合反应恒速阶段的活化能,在53~68℃范围内为26.00 kJ.mol-1。 相似文献
195.
Biopolymer active packaging is known to have low mechanical strength and highly brittle. Regardless to its disadvantage, polymers from natural sources have attracted serious attention since the non-renewable sources for example petroleum, the major precursor of plastic manufacturing become depleted. Starch-Chitosan for instance is a hybrid film that entirely green as it produced from a renewable material and totally degradable. The addition of chitosan in film packaging able to kill pathogen hence increases the food shelf life. Through nanotechnology advance, nanomaterial can be used for material reinforcement. Nowadays, greener approach could be applied by incorporating natural cellulose nanofiber into the film matrix. Oil palm empty fruit bunch (OPEFB) fiber that rich of cellulose contents could be treated chemically to purify the cellulose in the fiber. Cellulose fiber obtained was cut to a nano-size using acid hydrolysis. Transmission Electron Microscopy (T.E.M) obtained shown the nanofiber size was ranged between 1-100 nm in diameter. Nanocomposite film formulation, was constructed by varying the cellulose nanofiber incorporation between 2-10% per weight of starch. The strength of the films was measured as well as antimicrobial properties. The addition of 2% cellulose nanofiber into the film matrix exhibits high tensile strength with 5.25 Mpa compared to starch-chitosan hybrid film with 3.96 Mpa. However, no significant improvement in tensile strength was distinguished beyond that ratio. Antimicrobial analysis shows that the addition of cellulose nanofiber could increase the inhibition effect towards gram-positive bacteria but not towards gram-negative bacteria. The addition of 2% cellulose nanofiber increased the inhibition diameter towards gram positive bacteria, Bacillus subtilis up to 33%. However, inhibition towards Bacillus subtilis decreased with the incorporation of more cellulose nanofiber. In gram-negative bacteria Escherichia coli, the addition of cellulose nanofiber does not give significant effect to bacterial. In General, the addition of the unique structure of cellulose nanofiber in the starch based polymer system could enhance the mechanical strength of the film and increase the inhibition of the gram positive bacteria. 相似文献
196.
GUO Ze-Bin ZENG Shao-Xiao ZHENG Bao-Dong CHEN Bing-Yan ZENG Shao-Xiao ZHENG Bao-Dong LU Xu ZENG Shao-Xiao ZHENG Bao-Dong 《结构化学》2014,33(4):647-653
Lotus seed starch(15%, w/w) was subjected to ultra-high pressure(UHP) at 500 MPa for 10~60 min. The effects of UHP on the structural, pasting, and thermal properties of starch were investigated using solid-state 13C CP/MAS NMR, differential scanning calorimetry(DSC), HPSEC-MALLS-RI, and a rapid visco analyzer. The 13C CP/MAS NMR results revealed a reduction in the relative crystallinity and peak intensity of the crystalline state with increasing the UHP time. The molecular weight of native starch was 1.433 × 107 Da, which was higher than that of the UHP-treated starch. Viscograms of UHP-treated starch revealed an increase in paste viscosity, peak time, and pasting temperature and a reduction in breakdown and setback viscosity compared to the native starch. Furthermore, the DSC results showed a reduction in gelatinization temperature and gelatinization enthalpy with increasing the UHP time. 相似文献
197.
Cassava starch-based superabsorbent polymer was successfully synthesized using a new technology that based on modification of a Haake twin-roll mixer as reactor. The cassava starch was first gelatinized then modified by grafting under external shear stress in the reactor. The torque and temperature curves as a function of time can reflect the variations in the reactor and also offer some information about the copolymerization reaction. The advantages of this system include starch modification can be carried out(1) with high starch concentration,(2) under controlled time and(3) smaller amount of sample(60 g) required. The technology provides useful guides for reactive extrusion. The starch grafted composites were characterized by Fourier transform infrared spectroscopy(FTIR), nuclear magnetic resonance(NMR) and thermal gravimetric analysis(TGA). The TGA was also used for determining the percentage of grafting ratio. The results show that the cassava starch has been successfully grafted with acrylamide then crosslinked by N,N′-methylene-bisacrylamide using this reactor. The ultimate water absorbent capacity of the cassava-based superabsorbent polymer impacted by various pH values illustrated that the acid and basic solutions inhibit the ability of imbibing water. Additionally, gel properties of the cassava-based superabsorbent polymer were investigated. It can be concluded that the structure of cassava gel is stable, while the three dimensional network of cassava-based superabsorbent polymer is rigid but its structure could not resist external force effectively and everlastingly since G′ was decreased with increasing amplitude. 相似文献
198.
The objective of this work was to develop a simple and efficient method to prepare waxy maize starch nanoparticles (SNPs) by hydrochloric acid (HCl) vapor hydrolysis combined with ultrasonication treatment. The size, morphology, thermal property, and crystal structure of the SNPs were systematically studied. HCl treatment introduces a smaller particle diameter of starch particles from 13.73 ± 0.93 μm to 1.52 ± 0.01–8.32 ± 0.63 μm. Further ultrasonication treatment formed SNPs that displayed desirable uniformity and near-perfect spherical and ellipsoidal shapes with a diameter of 150.65 ± 1.91–292.85 ± 0.07 nm. The highest yield of SNPs was 80.5%. Compared with the native starch, the gelatinization enthalpy changes of SNPs significantly decreased from 14.65 ± 1.58 J/g to 7.40 ± 1.27 J/g. Interestingly, the SNPs showed a wider melting temperature range of 22.77 ± 2.35 °C than native starch (10.94 ± 0.87 °C). The relative crystallinity of SNPs decreased to 29.65%, while long-time ultrasonication resulted in amorphization. HCl vapor hydrolysis combined with ultrasonication treatment can be an affordable and accessible method for the efficient large-scale production of SNPs. The SNPs developed by this method will have potential applications in the food, materials, and medicine industries. 相似文献
199.
Finger millet (Eleusine Coracana) is rich in nutrients and minerals. The iron and calcium contents are comparatively higher than other cereal crops. Finger millet also has some antinutrients such as tannins and phytates, that needs to be removed for maximum health benefits. Traditionally, these antinutrients are removed by the hydration process. The conventional hydration process is time cumbersome and often results in poor quality grains. Ultrasonication during hydration of finger millet could reduce the processing time and antinutrient content in finger millet. The ultrasound amplitude, treatment time, and grain to water ratio during hydration were optimized. An ultrasound amplitude of 66%, treatment time of 26 min, and a grain to water ratio of 1:3 resulted in best desirability parameters with a reduction in phytate and tannin contents of the finger millet by 66.98 and 62.83%, respectively. Ultrasonication during hydration increased the water binding capacity and solubility of the finger millet starch. XRD study of the starch isolates confirmed the increased crystallinity of the particles. FESEM of the starch isolates also confirmed that ultrasound-assisted hydration of finger millet resulted in the desired size reduction and homogeneous distribution of starch particles. The optimized ultrasound-assisted hydration could be adopted and scaled up for bulk processing of finger millets. 相似文献
200.
Stéphanie Brouillet-Fourmann Christian Carrot Nathalie Mignard 《Rheologica Acta》2003,42(1-2):110-117
The structural evolution of a maize flour was followed by means of oscillatory shear measurements during heating at a rate
of 10 °C/min in presence of water. These measurements were performed in a special plate and plate vessel designed to prevent
moisture loss. The phenomena of gelatinization and gelation were clearly identified and their connection with the moisture
content also demonstrated. Moreover, the complex mechanisms involved in gelatinization and gelation in native starch were
separated. Softening of the amylose zones, exchange of water and amylose within the starch granules followed by amylopectin
melting leads to the gelation of starch. 相似文献