PVAm/淀粉复合物在再生浆中的应用

通过聚丙烯酰胺（PAM）的霍夫曼反应得到的聚乙烯胺（PVAm）与淀粉共混制备PVAm/淀粉复合物。在中性造纸条件下,PVAm/淀粉复合物对再生浆具有显著的助滤和纸张增强作用。当添加量为0.5%（对绝干浆）时,样品SF-1502的纸张干抗张强度增加33.3%,湿抗张强度提高2倍,打浆度降低41.3%。     

N-(2-Hydroxyethyl)formamide as a new plasticizer for thermoplastic starch

N-(2-Hydroxyethyl)formamide (HF) was synthesized efficiently and used as a new plasticizer for corn starch to prepare thermoplastic starch (TPS). The hydrogen bond interaction between HF and starch was proved by Fourier-transform infrared (FT-IR) spectroscopy. Scanning electron microscope (SEM) revealed that starch granules were completely disrupted and a continuous phase was obtained. The crystallinity of corn starch and HF-plasticized TPS (HTPS) were characterized by X-ray diffraction (XRD). The glass transitions of glycerol-plasticized TPS (GTPS) and HTPS were investigated by differential scanning calorimetry (DSC). The water resistance of GTPS was better than that of HTPS. In addition, the flexibility of HTPS was better than that of GTPS at low relative humidity.     

红薯淀粉烷基多糖苷生产的中试研究

用转糖苷法,以红薯淀粉、乙二醇、长链醇为原料,在2000L反应釜中生产了淀粉烷基多糖苷系列产品。工艺条件为m(红薯淀粉)∶m(乙二醇)∶m(长链醇)=1∶4∶1,残压小于9.3kPa,反应温度100～120℃。平均聚合度DP=1.10%,表面张力31.1～35.5mN/m,w(无机盐)<1.0%,w(固型物)>50%,w(活性物)>80%,w(游离脂肪醇)<1%。分析了刮膜除醇及氧化、还原脱色的生产工艺条件对产物的影响。用红外、气相色谱表征了产品。     

利用机械活化木薯淀粉制备淀粉磷酸酯的工艺研究

由于淀粉是一种多晶高聚物,其颗粒中一部分分子排列成疏松的非晶区,另一部分分子则排列成高度有序的结晶区,磷酸盐不易深入到颗粒内部,反应往往只能发生在颗粒表面,导致淀粉反应活性和反应效率较低,难以得到高取代度的产物.今利用自制的搅拌球磨机将普通木薯淀粉进行机械活化预处理,正磷酸盐为酯化剂,尿素为催化剂,干法制备淀粉磷酸酯.探讨了活化时间、磷酸盐用量、pH值、反应温度、反应时间和尿素用量对取代度(DS)和反应效率(RE)的影响,确定了最佳反应条件:活化时间1.5 h,磷酸盐用量12%,pH4.5,反应温度150℃,反应时间2 h,尿素用量2%.研究结果表明:机械活化预处理方法能显著提高木薯淀粉磷酸酯的DS和RE,表明机械活化能有效地提高木薯淀粉的化学反应活性.最佳工艺条件下木薯淀粉磷酸酯的DS和RE为0.0900和0.933.     

Physico‐Mechanical Properties of Biodegradable Starch Nanocomposites

Nanocomposites of cassava starch reinforced with waxy starch nanocrystals were prepared. They showed a 380% increase of the rubbery storage modulus (at 50 °C) and a 40% decrease in the water vapor permeability. X‐ray spectra show that the composite was more amorphous than the neat matrix, which was attributed to higher equilibrium water content in the composites. TGA confirmed this result and its thermal derivative suggested the formation of hydrogen bonding between glycerol and the nanocrystals. The reinforcing effect of starch nanocrystals was attributed to strong filler/matrix interactions due to the hydrogen bonding. The decrease of the permeability suggests that the nanocrystals were well dispersed, with few filler/filler interactions.

     

Designing Starch‐Based Nanospheres to Make Hydrogels with High Mechanical Strength

A robust method to prepare hydrogels with high mechanical strength is presented. Core/shell nanospheres with derivatizable allyl groups in the shell were first prepared. Starch‐based nanospheres were used as crosslinker to prepare polyacrylamide hydrogels. The starch‐based nanospheres were bridged by acrylamide to form crosslink points in the hydrogel network. They possess an extremely high mechanical strength. The results show that starch‐based nanosphere hydrogels can sustain strengths of 10.34 MPa, which is 60 times greater than for a normal hydrogel. The mechanical properties of SNH can be tailored by varying the content of SN. This approach offered a new way of making functional hydrogel with biodegradable component as a substitute for tissue.

     

Biodegradable composites based on starch/EVOH/glycerol blends and coconut fibers

Unripe coconut fibers were used as fillers in a biodegradable polymer matrix of starch/ethylene vinyl alcohol (EVOH)/glycerol. The effects of fiber content on the mechanical, thermal, and structural properties were evaluated. The addition of coconut fiber into starch/EVOH/glycerol blends reduced the ductile behavior of the matrix by making the composites more brittle. At low fiber content, blends were more flexible, with higher tensile strength than at higher fiber levels. The temperature at the maximum degradation rate slightly shifted to lower values as fiber content increased. Comparing blends with and without fibers, there was no drastic change in melt temperature of the matrix with increase of fiber content, indicating that fibers did not lead to significant changes in crystalline structure. The micrographs of the tensile fractured specimens showed a large number of holes resulting from fiber pull‐out from the matrix, indicating poor adhesion between fiber and matrix. Although starch alone degraded readily, starch/EVOH/glycerol blends exhibited much slower degradation in compost. Composites produced 24.4–28.8% less CO₂ compared with starch in a closed‐circuit respirometer. Addition of increasing amount of fiber in starch/EVOH/glycerol composite had no impact on its biodegradation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermoforming starch‐graft‐polycaprolactone biocomposites via one‐pot microwave assisted ring opening polymerization

A thermoformable starch‐graft‐polycaprolactone biocomposite was prepared by initiating ring‐open polymerization of caprolactone monomer onto starch under microwave irradiation. In this case, the thermoplastic and hydrophobic modification of starch could be realized by one‐pot grafting PCL, where the grafted PCL chains acted as the “plasticizing” tails of thermoforming and as the hydrophobic species of water‐resistance. The resultant biocomposites were injection‐molded as the sheets and their structure and properties were investigated by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, contact angle measurement, and tensile testing. In this case, the grafted PCL chains entangled each other, and hence contributed to the strength and elongation of biocomposites. This work provided a simple strategy of one‐pot thermoplastic and hydrophobic modification of starch, and may be applied in a continuous process of modification, compounding, and molding. Meanwhile, the resultant biocomposites containing starch are believed to have a great potential application as an environment‐friendly and/or biomedical material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

机械活化木薯淀粉氧化产物软化硬水能力的研究

采用搅拌球磨机对木薯淀粉进行机械活化,以不同活化时间的木薯淀粉为原料,CuSO4为催化剂,H2O2为氧化剂干法制备氧化淀粉,并以钙离子配位能力为评价指标,分别考察羧基含量、pH值、温度、钙离子浓度、配合时间等因素对木薯氧化淀粉软化硬水能力的影响。实验结果表明,机械活化对木薯氧化淀粉软化硬水的能力有显著的影响。由活化60 min的木薯淀粉制得的氧化淀粉当羧基含量为0.49%及0.84%时,在体系pH 10、温度30°C、钙离子浓度4 mmol/L、配合时间20 min的条件下钙离子的配合量分别为106.7 mg/g及136.70 mg/g,而在相同条件下,由原木薯淀粉制得的氧化淀粉当羧基含量为0.49%时,钙离子的配合量仅为48.0 mg/g。     

减水剂淀粉磺酸酯的研究

以玉米淀粉为基本原料,氯磺酸为磺化剂,可以合成淀粉磺酸酯。重点讨论了淀粉与磺化剂的配比、反应温度、反应时间和溶剂等因素对磺化反应的影响。得到合成最优条件为：淀粉（g）与磺化剂（mL）的配为0.4、反应温度为室温（20℃）、反应时间为2h,反应的溶剂为二氯甲烷。并对其作为减水剂的性能进行了检测,质量分数为0.3％时测得的水泥净浆减水率和3d、28d砂浆强度等各项指标均达到高效减水剂的国标要求。