淀粉结晶度计算的新方法

分析X射线衍射仪的不同衍射角范围、步长及扫描速率等测试因素对淀粉的X射线衍射图谱的影响;使用MDI Jade 软件采用两种方法实现淀粉结晶度的计算。结果表明：当设置衍射角范围为4～60°,步长为0.02°,扫描速率为10°/min时,分析测试结果较好;测试衍射角范围取4～30°之间时,计算结晶度的主观性因素影响相对减小,可快速、简便、可靠的计算结晶度大小,测得玉米、马铃薯、木薯淀粉相对结晶度分别为26.7%、18.4%和26.5%。     

MDI市场概况及工艺进展(待续)

详细介绍了MDI的国内外市场概况.工业上MDI是通过液相光气化法生产的,当前对该工艺的改进均是同绕节省能耗开展的,主要改进措施包括气相光气化工艺和氧去阴极化(ODC)技术.在工业化生产中,综合效果是通过一体化实现的.     

改性MDI催化剂的选择

在实际生产过程中,为便于MDI的储存、运输以及操作,降低生产成本,提高产品质量,需要对其进行改性。安全、稳定、快速地改性MDI的关键在于改性MDI催化剂的选择。     

二胺固化MDI型聚氨酯弹性体

采用聚四氢呋喃二醇（PTMG）和二苯基甲烷二异氰酸酯（MDI）合成预聚物,经3,3’-二氯-4,4’-二苯基甲烷二胺（MOCA）扩链合成了聚氨酯弹性体,测定了其物理性能和高温性能。结果表明,该体系弹性体具有良好的物理机械性能,尤其是其高温性能更加突出,120℃时撕裂强度保持率可达40％,用该体系制得的矿用磨盘,使用寿命是甲苯二异氰酸酯（TDI）体系的3倍以上,显示出良好的应用前景。     

聚合MDI改性BMC研究

以聚合MDI作为增稠剂改性团状模塑料(BMC),考察了聚合MDI用量增稠不饱和聚酯树脂(UP)和聚合MDI增稠不同质量比的不饱和聚酯树脂(UP)/环氧乙烯基树脂(VE)的混杂树脂对BMC物理性能的影响。结果表明,聚合MDI的加入能改善BMC的物理性能,聚合MDI增稠VE时,当质量分数为6%时,BMC的拉伸、弯曲和冲击强度均达到最大,收缩率最小;聚合MDI增稠UP/VE混杂树脂时,UP/VE质量比在25/45到35/35时,能获得最小的收缩率和力学性能。     

Construction of functional aliphatic polycarbonates for biomedical applications

Aliphatic polycarbonates are one important kind of biodegradable polymers and have been commonly used as integral components of engineered tissues, medical devices and drug delivery systems. As far as the biomedical application is concerned, traditional aliphatic polycarbonates usually suffer from the strong hydrophobicity, deficient functionality, and insufficient compatibility with cell/organs. Consequently, the application is quite limited in scope. Due to the imparted appealing properties, aliphatic polycarbonates bearing specifically designed functional/reactive groups attract great interest from researchers in the recent years. The present review outlines the development up to date concerning the design and biomedical application of functional aliphatic polycarbonates, with an emphasis on their ring-opening (co)polymerization preparation.     

我国麦秸板的研究现状及其存在的问题

介绍了我国麦秸板的研究现状,分析了麦秸板在生产过程中存在的问题,在此基础上,提出了一些建议和想法.     

Preparation and rheological studies on the solvent based acrylic pressure sensitive adhesives with different crosslinking density

On the basis of synthesis of a series of solvent based acrylic pressure sensitive adhesives (PSAs) with different crosslinking density, the thermal and rheological properties were characterized. T_g values were increased after crosslinked with MDI, and the thermal stability was also improved. Rheological studies were performed via frequency sweep, amplitude sweep, temperature sweep patterns, respectively. The creep recovery properties were also researched. In this way, it was proved that the linear viscoelastic (LVE) range was elongated as the feeding MDI increased, the elastic modulus (G′) of the acrylic PSAs was obviously increased after crosslinked with MDI whereas hardly making any change to the viscous modulus (G″). In the frequency sweep pattern, the PSAs samples behave as pseudoplastic non-Newtonian fluid; and zero shear viscosity increased as the feeding MDI mass ratio was increased, after discussing the cross-over frequency (?^?) and the relaxation time t_R, it can be concluded that the addition of MDI would make for the improvement of the elasticity of the PSAs; in the temperature sweep pattern, it could be seen that the cross-over temperatures (where G″=G′) were 34 and 70 °C for the samples crosslinked with 0 wt% and 0.1 wt% MDI, respectively. When the mass ratio of MDI fed was higher than 0.1 wt%, even though the temperature increased to 120 °C, the samples remained elastic (G′>G″). In the creep recovery test, it was noteworthy that as the feeding ratio of MDI was increased, the creep recovery properties of the acrylic PSAs were substantially improved. And for the same sample, as the applied constant stress increased from 200 to 1000 Pa, the recoverable proportion of the materials was principally not changed in that all the experiments were carried out within the linear viscoelastic range of the samples. And the sample crosslinked with 0.5 wt% MDI shows the highest 180° peel stress.     

高回弹、低密度环保泡沫用改性MDI的合成及其对制品性能的影响

采用低不饱和度、高相对分子质量、高活性聚醚多元醇,反应型增硬剂,反应型开孔剂和MDI型异氰酸酯为原料,研制出一种用于制备高回弹、低密度环保型泡沫的改性MDI,解决了当前改性MDI的模塑泡密度难以低于45kg/m3的技术问题。此改性MDI制备的高回弹泡沫在保证制品良好回弹性和硬度的前提下,密度最低可以降至38kg/m3。     

MDI生产技术及市场

综述了国内外MDI生产技术及发展,分析了国内外生产,需求及市场,指出了MDI作为聚氨酯工业的主要原料,具有广阔的市场前景,并提出了合理化建议。