微细化玉米淀粉粒度效应及其流变学行为研究

采用现代粉体机械可制备微细化玉米淀粉。随着淀粉粒度减小,其支链淀粉和直链淀粉糊的特性黏度降低,分子量下降。布拉班德黏度分析表明,微细化玉米淀粉糊化起始温度下降,热糊稳定性增强;在冷却阶段,随着粒度降低,微细化玉米淀粉的凝沉性较原玉米淀粉增强,冷糊稳定性较原玉米淀粉减弱。微细化玉米淀粉糊为非牛顿假塑性流体,其流动性随粒度降低而增加,并显示出一定的粒度效应。     

冷水溶解度对玉米淀粉糊液性质的影响研究

采用乙醇-碱法制备冷水可溶(CWS)玉米淀粉。以糊液表观黏度、糊液粘附强力和糊液透明度为指标对不同冷水溶解度的CWS玉米淀粉的糊液性质进行研究,并与工厂常用的氧化淀粉进行比较分析。目的是研究冷水溶解度对玉米淀粉糊液性质的影响规律,提高玉米淀粉的使用效果。结果表明:随着冷水溶解度的增加,CWS玉米淀粉糊液的表观黏度逐渐减小,对纯棉纱的粘合强力略微下降,透明度及抗老化性能上升。当CWS玉米淀粉的冷水溶解度为95.48%时,淀粉糊液能够克服氧化淀粉在低温环境下粘合强力急剧下降的缺陷。     

围压作用下煤岩材料超声致裂规律研究

当超声波在煤岩固体材料中传播时,受其机械效应,煤岩基质固体颗粒间相互作用。从超声波的机械效应角度结合断裂力学,对围压影响的超声激励破岩机制进行探讨,利用 RFPA2D 岩石破裂过程分析系统对超声激励不同围压下煤岩致裂过程进行了数值试验验证。研究表明：围压降低了煤岩内部裂纹的断裂强度因子,改变裂纹尖端应力场;围压对煤岩破裂具有抑制作用,在相同功率超声作用下,围压越大,超声激励碎岩程度越低;数值实验表明,随着围压增加,超声致裂煤岩影响区域逐渐减小,煤岩破坏形式由低围压下的张拉和剪切破坏共同作用逐渐向高围压下单一剪切破坏过渡。相同有效声压作用下,煤岩破裂过程中主应力随煤岩围压升高而增大。     

超声波对凝固石蜡中微粒分布的影响研究

研究了超声波的凝聚作用和空化作用,对石蜡中的微粒进行了超声处理实验,观察和分析超声处理后的石蜡中微粒的分布状况。实验主要探讨了石蜡中微粒的凝聚与超声处理时间和超声波功率之间的关系,观察对比不同功率和不同超声处理时间下石蜡中微粒的凝聚趋势,并对石蜡样本进行数码照相和金相显微分析,测出颗粒团块大小,以实验数据得出超声处理石蜡微粒凝团效果最好时所对应的超声波功率大小。     

超声波作用下动态闪蒸制备冰浆

本文基于闪蒸理论,设计了一套超声波作用下动态闪蒸制备冰浆的实验装置。研究同一真空度下不同超声波功率、喷射体积流量及不同质量浓度的乙醇添加对冰浆真空动态闪蒸特性的影响。结果表明:与无超声波作用相比,超声波对增大水的闪蒸强度作用明显;体积流量一定时,降温降压速率随超声波功率的增大而增大,较高的超声功率有助于增强水的闪蒸强度,有利于动态制冰;而同一超声功率下随着体积流量的增大最终平衡压力也越高。较大体积流量不利于闪蒸的持续进行;乙醇添加剂能促进溶液降温,质量浓度越高,温度降得越低;质量浓度为5%时,可消除溶液过冷度,更利于产生冰晶。     

食品新鲜度指示卡基材玉米淀粉膜的 成膜工艺研究

以玉米淀粉为原料,添加适量的增强剂和增塑剂,制作了可作为食品新鲜度指示卡基材的玉米淀粉膜。研究了搅拌速度、超声功率、流延方法等工艺条件,对玉米淀粉膜的外观、力学性能和CO2透气性的影响。结果表明:搅拌速度和超声功率变化对淀粉膜的断裂伸长率影响不大,但搅拌速度和超声功率不足或过高都会降低膜的抗拉伸强度和CO2透气性;单层流延膜的CO2透气性能虽比多层流延膜(双层和三层)的稍差,但其表观性能和力学性能均优于多层流延膜的。在搅拌速度为200r/min,超声功率为(40Hz)100W,且采用单层流延成膜条件下,制得的玉米淀粉膜表观性能较好、CO2透气性较大、力学性能较佳,比较符合以CO2为特征气体的食品新鲜度指示卡基材的要求。     

超声振动对闪光铝颜料填充HDPE复合材料流变行为和性能的影响EI北大核心CSCD

以改进的超声波辅助的转矩流变仪作为聚合物超声处理装备,测量高密度聚乙烯/闪光铝片颜料(HDPE/Al)复合材料的流变行为,并研究超声波强度对HDPE/Al复合材料的流变行为、晶体结构、结晶度和热稳定性的影响。结果表明,超声波能提高HDPE/Al复合材料的流动速率,降低表观剪切黏度与口模压力;超声波强度越大,表观剪切黏度与口模压力的下降越显著,越有利于促进聚合物熔体的流动,当超声波强度为300 W,流变仪转速为5r/min时,表观黏度下降了61%,而口模压力下降了58%;超声处理提高了HDPE/Al复合材料的结晶度并细化了晶体片层的厚度;超声波强度在200W时能够显著提高HDPE/Al复合材料的热稳定性。     

超声振动对闪光铝颜料填充HDPE复合材料流变行为和性能的影响

以改进的超声波辅助的转矩流变仪作为聚合物超声处理装备,测量高密度聚乙烯/闪光铝片颜料(HDPE/Al)复合材料的流变行为,并研究超声波强度对HDPE/Al复合材料的流变行为、晶体结构、结晶度和热稳定性的影响。结果表明,超声波能提高HDPE/Al复合材料的流动速率,降低表观剪切黏度与口模压力;超声波强度越大,表观剪切黏度与口模压力的下降越显著,越有利于促进聚合物熔体的流动,当超声波强度为300 W,流变仪转速为5r/min时,表观黏度下降了61%,而口模压力下降了58%;超声处理提高了HDPE/Al复合材料的结晶度并细化了晶体片层的厚度;超声波强度在200W时能够显著提高HDPE/Al复合材料的热稳定性。     

高流动性、强疏水性淀粉的制备及性能

采用干法改性处理技术对玉米淀粉进行改性处理,制备得到具有高流动性及强疏水性的玉米淀粉。通过活化指数、接触角、流动时间及休止角等指标,对改性前后玉米淀粉的流动性及疏水性进行评价。结果表明,经过改性处理,玉米淀粉由亲水性表面转变为强疏水性表面,并且改性后的玉米淀粉具有了良好的流动性。X射线衍射(XRD)测试结果表明,改性处理并没有改变玉米淀粉的结晶结构,只是改变玉米淀粉的表面性质。     

聚乳酸/热塑性玉米淀粉/SiO_2复合材料的流变性能和力学性能

采用双螺杆挤出机,通过熔融共混制备了热塑性玉米淀粉基纳米二氧化硅(SiO_2)母料和聚乳酸(PLA)/热塑性玉米淀粉/SiO_2复合物,利用转矩流变仪研究了其流变性能。结果表明,热塑性玉米淀粉基纳米SiO_2母料熔体和PLA/热塑性玉米淀粉/SiO_2复合物熔体的非牛顿指数小于1,属假塑性流体。热塑性玉米淀粉基纳米SiO_2母料熔体黏度随纳米SiO_2用量的增大而提高,SiO_2用量为8phr的母料4#熔体黏度对剪切速率的依赖性最强。PLA/热塑性玉米淀粉/SiO_2复合物熔体黏度决定于热塑性玉米淀粉基纳米SiO_2母料中纳米SiO_2用量,可以通过调整母料用量和母料中SiO_2用量,调整复合物的熔体流动。PLA/热塑性玉米淀粉/SiO_2复合物的缺口冲击强度随纳米SiO_2母料份数的增加而增大。     

Evaluation of the emulsifying properties of some cationic starches

Different cationic potato, maize, and waxy maize starches were evaluated for their emulsifying properties. Emulsions were prepared using 20% (w/w) arachidic oil and 80% (w/w) water. Emulsions with the cationic starches as emulsifier in a concentration ranging from 1% to 5% (w/w) were prepared and characterized by droplet size and viscosity measurements, and the stability was evaluated visually and by electrical conductance measurements. None of the cationic potato, waxy maize starches, and maize starches with a low degree of substitution (DS) showed adequate emulsifying properties. Emulsions prepared using non-pregelatinized (C ☆ bond 05914, 2% and 5% w/w; C ☆ bond 05907, 5% w/w) and pregelatinized (C ☆ bond 12504, 5% w/w) cationic maize starches with high-DS were visually stable. The initial mean droplet volume diameter of the emulsions prepared with these cationic starches in a 5% (w/w) concentration was similar and ranged from 2.40 to 2.84 μm however, there was an important difference in droplet size distribution. The droplet size distribution of the emulsions prepared using the non-pregelatinized high-DS cationic starches was markedly narrower than in the case of the emulsions prepared using the pregelatinized high-DS cationic starches. The droplet size of the emulsions remained almost constant during 120 days of storage. Visual inspection and electrical conductance measurements showed that these emulsions were stable for at least 120 days.     

微波辐射对高链玉米淀粉热性质的影响

采用微波对30%水分含量的高链玉米淀粉进行处理。结果表明,微波处理降低了淀粉的膨胀度和溶解度、冻溶稳定性以及焓值,提高了糊化转变温度及转变温度范围。高链玉米淀粉经处理后糊化起始温度升高、黏度降低,黏度曲线由C型变为D型。以上表明在淀粉颗粒内无定型区和结晶区的直链淀粉与直链淀粉、直链淀粉与支链淀粉发生交互作用,产生了新的不同稳定性的结晶体,从而导致微波淀粉内部更加有序的结晶排列。     

Crosslinked Starch as Sustained Release Agent

Different types of crosslinked starches and pregelatinized-crosslinked starches were evaluated for their use as hydrophilic matrices. Some fundamental properties of these chemically modified starches, e.g. granule swelling power and viscosity of the dispersion in function of pH and ionic strength, were studied. Dissolution tests and the rate and amount of water uptake were evaluated on tablets containing theophylline and modified starch (40/60 w/w), compressed on an instrumented tablet press at three different pressures (50,200 and 300 MPa.). Theophylline releasing profiles were determined using the paddle system at a rotational speed of 50 rpm Water, simulated gastric fluid, and simulated intestinal fluid were used as dissolution media. Crosslinked starches showed a poor swelling power and dispersion viscosity in comparison to pregelatinized starch and pregelatinized-crosslinked starches. The pregelatinized-crosslinked starches developed less swelling power than the pregelatinized starch, but they showed higher dispersion viscosity than the pregelatinized starch. The viscosity of all starch dispersions was not affected by ionic strength. An alkaline pH dramatically increased the dispersion viscosity of pregelatinized starch and pregelatinized-crosslinked starches. Drug dissolution rate was lower for tablets containing pregelatinized starch than for tablets containing pregelatinized-crosslinked starches. This phenomenon can be related to the rate and amount of water uptake. The dissolution rate seemed not to be influenced by the compression force nor by the composition of the dissolution media. The results indicate that crosslinked starches, either pregelatinized or not, are not suitable as sustained release agents.     

Fast and controlled release of triamcinolone acetonide from extrusion-spheronization pellets based on mixtures of native starch with dextrin or waxy maize starch

Pellets composed chiefly of inexpensive starches allow modulation of the rate of release of the poorly soluble drug triamcinolone acetonide in media of pH 1.2-6.8. Wheat- or maize-starch-based pellets with 20% of white dextrin release the drug in vitro almost completely within 20 min, while maize-starch-based pellets with 5-35% of waxy maize starch sustain gradual release over periods of 9-12 hr or longer when prepared using appropriate amounts of granulation fluid.     

Fast and Controlled Release of Triamcinolone Acetonide from Extrusion-Spheronization Pellets Based on Mixtures of Native Starch with Dextrin or Waxy Maize Starch

Pellets composed chiefly of inexpensive starches allow modulation of the rate of release of the poorly soluble drug triamcinolone acetonide in media of pH 1.2–6.8. Wheat- or maize-starch-based pellets with 20% of white dextrin release the drug in vitro almost completely within 20 min, while maize-starch-based pellets with 5–35% of waxy maize starch sustain gradual release over periods of 9–12 hr or longer when prepared using appropriate amounts of granulation fluid.     

Manufacture and research of TPS/PE biocomposites properties

In this paper the process of native starch preparing for modification by extrusion and manufacture of biocomposites is presented. The first aim of this study was to determine the mixing and granulating condition of native starch to obtain granulated native starch. For mixing and granulation of native starch Intensive Mixer manufactured by Maschinenfabrik Gustav Eirich was used. Mixing and granulation in a single process is a new method of preparation of powders for other processing. The main task of granulation is the elimination of dust emissions and the increase in density of powders. Granules are easy for dosage and more handy for transport and storage than powders, which is important from a technological point of view.The second aim of this study was to manufacture TPS/PE biocomposites. At first thermal modification of waxy maize starch was carried out with the use of a co-rotating twin screw extruder. During extrusion native starches have been deprived of their crystallinity and the obtained starch (TPS) has fully amorphous structure. XRD analysis revealed that semi crystalline phase of native starch after extrusion disappeared. During extrusion crystal structure of native starch is transformed into amorphous structure of thermoplastic starch (TPS), which was confirmed by XRD analysis.Reactive extrusion of obtained thermoplastic starch and high density polyethylene (HDPE) in the presence of polyethylene-grafted maleic anhydride (PE-g-MA) was done. To modify properties of TPS/PE blend polycaprolactone (PCL) was added in amount of 5 and 10 wt.%. The mass flow rate, static mechanical properties, thermal properties and morphology of obtained biocomposites were examined. The results show that the increased amount of TPS caused an increase in tensile strength and modulus of elasticity of prepared biocomposites. Addition of PCL to TPS/PE blends decreased tensile strength and modulus of elasticity. Moreover, higher amount of TPS and PCL in TPS/PE blends caused decrease of the elongation at break. On the other hand, using of PE-g-MA in TPS/PE blends cause increasing phase compatibility, which was confirmed by mechanical properties and morphology measurements.Biocomposites filled with higher TPS content (45 and 60 wt.%) possess lower resistance to hydrolytic degradation, which cause decrease of mechanical properties.It was found that higher amount of TPS in TPS/PE blends have small effect on mass flow rate and thermal properties estimated by differential scanning calorimetry (i.e. melting temperature, degree of crystallinity, melting enthalpy). This phenomenon have significant influence on processing of obtained biocomposites.     

Evaluation of the material and tablet formation properties of modified forms of Dioscorea starches

Starches obtained from four different Dioscorea species—namely, White yam (Dioscorea rotundata), Bitter yam (Dioscorea dumetorum), Chinese yam (Dioscorea oppositifolia), and Water yam (Dioscorea alata)—were modified by cross-linking, hydroxypropylation, and dual modification—cross-linking followed by hydroxypropylation. The physicochemical, material, and tablet properties of the modified starches were investigated with the aim of understanding their properties to determine their potential use for different applications. The tablet formation properties were assessed using 3D modeling, the Heckel equation, and force-displacement profiles. The analyzed tablet properties were elastic recovery, compactibility, and disintegration. The result indicates that the modifications generally increased the swelling power for all the starches in the rank order hydroxypropyl > hydroxypropylated cross-linked > cross-linked (CL) while the solubility did not show a clear-cut pattern. This indicates that hydroxypropylation generally showed the strongest effects on swelling. Furthermore, hydroxypropylation improved the hot water swelling of the CL starches. The modifications did not cause any detectable morphological change in the starch granules shape or size although slight rupture was observed in some granules. CL starch had the lowest water sorption capacity and hydroxypropylation increased the sorption capacity of the CL starches. The material property results indicate that hydroxypropylation and cross-linking did not significantly improve the flowability and compressibility but improved bonding, which resulted in an increased compaction and higher tablet crushing force even though they all disintegrated rapidly. Thus, the modified Dioscorea starches showed potentials for development as new excipients in solid dosage form design, and they could be useful as disintegrants or for Soft tableting.     

Effects of pigeon pea and plantain starches on the compressional, mechanical, and disintegration properties of paracetamol tablets

A study has been made of the effects of pigeon pea starch obtained from the plant Cajanus cajan (L) Millisp. (family Fabaceae) and plantain starch obtained from the unripe fruit of Musa paradisiaca L. (family Musaceae) on the compressional, mechanical, and disintegration properties of paracetamol tablets in comparison with official corn starch BP. Analysis of compressional properties was done by using density measurements, and the Heckel and Kawakita equations, whereas the mechanical properties of the tablets were evaluated by using tensile strength (T--a measure of bond strength) and brittle fracture index (BFI--a measure of lamination tendency). The ranking for the mean yield pressure, P(y), for the formulations containing the different starches was generally corn < pigeon pea < plantain starch while the ranking for P(k), an inverse measure of the amount of plasticity, was pigeon pea < plantain < corn starch, which indicated that formulations containing corn starch generally exhibited the fastest onset of plastic deformation, whereas those formulations containing pigeon pea starch exhibited the highest amount of plastic deformation during tableting. The tensile strength of the tablets increased with increase in concentration of the starches while the Brittle Fracture Index decreased. The ranking for T was pigeon pea > plantain > corn starch while the ranking for BFI was corn > plantain > pigeon pea starch. The bonding capacity of the formulations was in general agreement with the tensile strength results. The disintegration time (DT) of the formulation increased with concentration of plantain and corn starches but decreased with concentration of pigeon pea starch. The general ranking of DT values was plantain < pigeon pea < corn starch. Notably, formulations containing pigeon pea starch exhibited the highest bond strength and lowest brittleness, suggesting the usefulness of pigeon pea starch in producing strong tablets with minimal lamination tendency. Plantain starch, on the other hand, would be more useful where faster disintegration of tablet is desired. The results show that the starches could be useful in various formulations depending on the intended use of the tablets with the implication that the experimental starches can be developed for commercial purposes.     

Resistant starch as a carrier for oral colon-targeting drug matrix system

In this study, a novel tablet of protein drug matrix for colon targeting was developed using resistant starch as a carrier prepared by pre-gelatinization and cross-linking of starch. The effects of pre-gelatinization and cross-linking on the swelling and enzymatic degradation of maize starch as well as the release rate of drug from the matrix tablets were examined. Cross-linked pre-gelatinized maize starches were prepared by double modification of pre-gelatinization and cross-linked with POCl₃, and bovine serum albumin was used as a model drug. For in vitro drug release assays, the resistant starch matrix tablets were incubated in simulated gastric fluid, simulated intestinal fluid and simulated colonic fluid, respectively. The content of resistant starch and swelling property of maize starch were increased by pre-gelatinization and cross-linking, which retarded its enzymatic degradation. Drug release studies have shown that the matrix tablets of cross-linked pre-gelatinized maize starch could delivery the drug to the colon. These results indicate that the resistant starch carrier prepared by pre-gelatinization and cross-linking can be used for a potential drug delivery carrier for colon-targeting drug matrix delivery system.     

铝/钢异种金属的超声振动强化搅拌摩擦焊接工艺

采用新型超声振动强化搅拌摩擦焊接工艺实现了6061-T6铝合金以及QP980高强钢的搭接焊, 对比分析了有无超声作用下, 接头的宏观形貌、微观组织和拉伸剪切性能, 同时研究了超声振动对焊接载荷的影响。结果表明: 焊接前对母材施加超声振动, 可以起到软化母材的作用, 促进了材料的塑性流动, 扩大了铝/钢界面区和焊核区, 使更多的钢颗粒随搅拌针旋转进入铝合金侧, 在界面区边缘形成钩状结构, 进而提高了接头的失效载荷; 超声改变了FSW接头断裂位置和断口形貌, 提高了接头力学性能, 在本实验工艺参数范围内, 接头最大的平均失效载荷为4.99 kN; 当焊接速度为90 mm/min, 下压量为0.1 mm时, 施加超声振动使接头的平均失效载荷提高了0.98 kN, 拉剪性能提升28.24%;施加超声振动后轴向力F_z、搅拌头扭矩M_t和主轴输出功率分别下降2.46%, 6.44%和4.59%。