VDC－MA悬浮共聚树脂分子量及其分布的研究

联用宽分布ＶＤＣ－ＭＡ悬浮共聚物试样的［η］和ＧＰＣ谱图数据，确定了此共聚物在四氢呋喃溶剂中、３０℃下的Ｍａｒｋ－Ｈｏｕｗｉｎｋ常数：Ｋ＝２．５４×１０－２，α＝０．６７５７。进一步研究了单体配比、转化率、引发剂浓度以及聚合温度等因素对于分子量及其分布的影响，并建立了分子量模型。     

沥青感温性指标与沥青组成的灰关联熵分析

沥青的化学组成不同对沥青的物理性能有着不同程度的影响。为了分析这些影响因素的显著性，采用改进的灰关联熵分析法，分析了影响沥青感温性指标的因素，结果表明，这种方法克服了一般灰关联度分析方法的不足，灰熵关联度大小不受分辨系数的影响。影响老化前沥青感温性指标的主要因素是极性芳香分，环烷芳香分，以及中分子尺寸分布和大分子尺寸分布；影响老化后沥青感温性指标的主要因素是沥青的沥青胶体不稳定指数(Ic)和沥青质以及大分子尺寸分布和中分子尺寸分布。     

油田水中聚丙烯酰胺的凝胶色谱法分析

凝胶色谱分析油田水中的ＨＰＡＭ方法已在各油田广泛使用，其淋洗液是ＣＨ３ＯＨ／ＮａＨ２ＰＯ４二元体系，本分析了该体系存在的一些问题，在实际研究的基础上提出了ＮａｓＣｌ单盐淋洗液体系。本报道的以０．２ＭＮａＣｌ为淋洗液的分析体系，能够快速、准确的分析油田的ＨＰＡＭ，解决了目前以ＣＨ３ＯＨ／ＮａＨ２ＰＯ４体系作淋洗液所存在的问题。     

聚碳酸酯的分子量分布与热降解

除了用Ｍｗ，Ｍｎ和Ｍｗ／Ｍｎ表征聚碳酸酯（ＰＣ）分子量大小和分布宽度外，还采用了（Ｍｐ－Ｍ１０）和（Ｍ９０－Ｍｐ）来表征低分子量和高分子量尾端所延伸的宽度，并以两尾端的起始分子量作为参考参数。其中Ｍｐ为分子量微分分布曲线峰位分子量，而Ｍ１０和Ｍ９０则为累积分布曲线中１０％和９０％处的分子量。研究了这些参数与聚碳酸酯热降解的关系，发现除数均分子量外，高低分子量尾端部分与ＰＣ热稳定性关系密切，尤其是低分子量尾端分布状态和起始分子量大小，对ＰＣ热稳定性更为敏感。这与ＰＣ端ＯＨ基相对浓度同ＰＣ热降解率的关系相一致。     

用于水泥沥青砂浆的聚羧酸减水剂的制备

采用聚乙二醇单甲醚(1000、2000)、甲基丙烯酸、阻聚剂、催化剂、引发剂、苯乙烯、丙烯酰胺和对苯乙烯磺酸钠合成了用于水泥沥青砂浆的聚羧酸减水剂.研究了酸醇摩尔比和苯乙烯、丙烯酰胺、对苯乙烯磺酸钠的用量对合成减水剂性能的影响.对聚羧酸减水剂配比进行了优化,进行了中试,制备了CA砂浆样板,并进行性能测试.用GPC对中试聚羧酸减水剂进行了表征.结果表明:大单体的制备及减水剂聚合工艺是可行的.最佳酸醇摩尔比为4.0:1.0,苯乙烯和丙烯酰胺的最佳用量均为3％,对苯乙烯磺酸钠用量以不超过3％为宜.掺该合成聚羧酸减水剂的CA砂浆性能良好,制备的CA砂浆样板基本无缺陷.     

Variation of MUF and PMUF resins mass fractions during preparation

The variation of molecular mass distribution with the progress of the reaction was studied for the following: (i) sequential‐type melamine–urea–formaldehyde (MUF) resin formulations in which the sequence of addition of chemicals follows well‐defined species reactivity principles; (ii) a nonsequential MUF formulation in which simultaneous melamine and urea competition for formaldehyde yields a MF resin cocondensed with small amounts of urea. This resin became soaked with reacted and unreacted monomeric urea species. (iii) A PMUF resin, namely a MUF resin with a small proportion of phenol (7.8% by weight on melamine and urea) cocondensed with the main MUF fraction. All the formulations used were industrial resins formulations in current use. Development and variation of molecular mass fractions, from which performance and other useful resin parameters depend, have been found to depend on the type of resin formulation used for these type of aminoplastic resins. The two very different MUF resin formulations yielded different variations in molecular mass fractions during the progress of the reaction and during the so‐called ambient temperature “maturing” of the resin. The PMUF resin also showed both similar and different fractions present during manufacturing and during short term ageing at ambient temperature. While similarities in recurrent fractions and in trends are common to all the three different formulations, differences between them are also clearly observed. A major proportion of the reaction of some of the aminoplastic resins examined also occurs on ageing (i.e.“maturing” of the resin at ambient temperature), this appearing to be an essential phase of the resin preparation process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4842–4855, 2006     

Functionality distribution and crosslink density of hydroxyl-terminated polybutadiene

A novel approach is proposed for estimating the average molecular weight between crosslinks (M?_c) from the functionality distribution of hydroxyl-terminated polybutadiene ( HTPB ). The functionality distribution of four free-radically polymerised HTPB prepolymers of varying hydroxyl content and molecular weight was determined by a combination of preparative and analytical gel permeation chromatography. The gumstock properties of the samples cured with stoichiometric amounts of toluene diisocyanate were not correlatable with the relative amounts of difunctional chain extender and multifunctional crosslinker present, unlike the case of HTPB with similar hydroxyl content and molecular weight. However, the mechanical properties and sol content could be correlated with the average molecular weight between crosslink sites, M?_c, of the cured polymer. The M?_c values derived by our method compare well with those of classical methods, and the observed differences are attributed to segmental entanglement. These M?_c values give consistently good correlation with all the gumstock properties, confirming the validity of our approach and the soundness of the techniques developed for the determination of the functionality distribution of HTPB .     

基于广义预测的双电机同步控制

为减小多电机运动过程中的同步误差,提出了基于广义预测控制的两轴同步控制算法,其基本思想是在二次性能指标中加入同步误差的影响,使得该性能指标对单轴的跟踪误差、控制增量以及两轴之间的同步误差同时进行有限时段内的在线滚动优化,所得到的控制规律包含了两轴之间的交叉耦合作用,克服了单个电机受到扰动时两轴不能精确同步的问题,且该算法对系统的建模精度要求较低,在线滚动优化对负载扰动、随机噪声有很好的抑制作用。Matlab仿真实验结果表明,该控制算法能获得良好的单轴跟踪精度、两轴同步精度以及抗干扰能力。     

一种改进的广义预测控制算法

为了解决广义预测控制(GPC)算法本身计算量大以及无法兼顾快速性和超调的问题,提出了一种改进的广义预测控制算法。首先介绍了广义预测控制的基本算法和一种新型算法,包括算法的基本理论和优缺点,然后经过一定的数学分析,提出了一种改进算法,最后对3种算法进行了Matlab仿真,以比较静态误差。实验结果表明,该改进算法不仅能大大减少计算量,而且能很好地抑制超调,同时兼顾了快速性。     

Characterization of enzyme‐deproteinized skim rubber

Skim natural rubber latex is a protein‐rich byproduct obtained during the centrifugal concentration of natural rubber latex. Skim latex has a very low dry rubber content (4–8%), and the rubber particles are smaller in size. It has a higher proportion of nonrubber solids, which are mostly proteinaceous in nature. It is difficult to coagulate, and it takes more processing time. The proteins in skim latex can be decomposed by proteolytic enzymes. This article discusses the use of stabilized liquid papain from the papaya plant (Carica papaya) for deproteinization followed by creaming for quick and easy coagulation of skim latex. The technological properties and aging characteristics of the deproteinized skim rubber are compared with those of conventionally prepared skim rubber and block rubber. The deproteinized skim rubber showed enhanced quality parameters. Particle size analysis revealed that deproteinization and creaming of the skim latex did not markedly change the particle size. Gel permeation chromatography showed a reduction in the quantity of fatty acids after deproteinization and creaming, which was reflected in the improvement of the aging characteristics in comparison with the control sample. Vulcanizates prepared with the deproteinized skim rubber had higher resilience, lower heat buildup, lower compression set, and good tensile strength and elongation at break in comparison with conventionally prepared skim rubber, and the properties were almost comparable to those of block rubber. The improvement in the mechanical properties and aging characteristics could be attributed to the reduction of the protein content, the partial removal of unsaturated fatty acids, and the removal of metal ions that were pro‐oxidants during the deproteinization and creaming process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009