电极材料对木质素磺酸盐电氧化效果影响的研究

用C、Ti合金和PbO2电极对木质素磺酸盐进行电氧化．结果表明，C和Ti合金作为阳极，氧化能力弱，氧化效果不显著；PbO2电极氧化木质素磺酸钠，效果明显，氧化前后，其IR，UV和1H－NMR谱图发生显著变化，－COOH含量升高，苯环结构被破坏。其数均分子量随氧化电量的增加而有一个上升到降低的过程，说明电氧化过程中聚合与降解反应共存。电氧化能改善木质素横酸盐作为水泥添加剂的分散性能。     

二氧化铅膜电极用于木质素磺酸盐电氧化反应的研究──Ⅱ.电解条件对电氧化过程中脱色反应的影响

用一种新型电极一PbO_2膜电极对木质素磺酸盐溶液进行电氧化反应,研究了溶液pH值、电解电压和电量对电氧化过程中木质素磺酸盐脱色反应的影响。结果表明,当电解电压维持在2．5V左右时能有效地使木质素磺酸盐发生脱色反应,高pH值条件有利于脱色反应的进行,电解电量的增加可提高脱色程度。     

二氧化铅膜电极用于木质素磺酸盐电氧化反应的研究：Ⅱ.电解条件？…

用一种新型电极－ＰｂＯ２膜电极对木质素磺酸盐溶液进行电氧化反应，研究了溶液ｐＨ值，电解电压和电量对电氧化过程中木质素磺酸盐脱色反应的影响。结果表明，当电解电解维持在２．５Ｖ左右时能有效地使木质素磺酸盐发生脱色反应，ｐＨ值条件有利于脱色反应的进行，电解电量的增加可提高脱色程度。     

木质素磺酸盐潜在应用

木质素磺酸盐用丙酮法从木材和荻苇亚硫酸盐制浆废液中分离出，并经SephadexG－50柱进一步纯化，然后测定官能团含量和分子量分布。在H2O2－Fe（Ⅱ）催化作用下，两种浓红液用丙烯酸进行接枝改性得共聚产物，然后作了表面张力试验和对水中难溶性盐如硅酸钙、磷酸氢钙和硫酸钙的分散性试验。结果表明，木材木质素磺酸盐比荻苇木质素磺酸盐分子最高、磺酸基和酚羟基含量高，但羧基含量低。接枝改性前后的样品均有一定的表面活性和分散性。改性后的样品比改性前的样品分散性能明显提高。但不论是改性前的样品还是改性后的样品均显示出木材优于荻苇。     

木质素磺酸盐减水剂改性研究进展

筒述了木质素磺酸盐减水剂的改性方法和性能研究的最新进展.物理改性方法包括木质素磺酸盐的分离提纯和对其分子量进行分级;化学改性方法主要有氧化、磺化、酚化、羟甲基化、曼尼希反应和接枝共聚等;木质素磺酸盐减水剂对水泥凝结时间、强度、水化过程的影响以及在水泥颗粒表面吸附行为是其性能研究的主要方面.最后总结认为,进一步加强改性方...     

落叶松树皮栲胶废渣各组分及其磺化产物的表面活性对比研究

分析了兴安落叶松树皮栲胶废渣的主要化学组分及各组分的磺化产物对木质素磺酸盐的表面活性的作用,发现树皮栲胶废渣制备的木质素磺酸盐表面活性、分散性能和净浆流动度较木材木质素磺酸盐高。表面活性和分散性能好的主要原因是栲胶废渣中可溶单宁和红粉的存在,而具有更好的净浆流动度是因为可溶单宁和酚酸的存在。     

改性木质素磺酸盐GCL2-D1的缓蚀机理

采用凝胶渗透色谱、化学滴定法、紫外差示光谱法、环境扫描电镜、交流阻抗谱、俄歇能谱等方法研究了改性前后木质素磺酸盐的结构特征和缓蚀性能,揭示了缓蚀作用机理。改性后木质素磺酸盐的分子量从11048提高到29381,磺酸基含量从9.04%提高到11.2%,羧基含量从5.81%提高到15.84%,在溶液中的构型由球状变为直链状,在金属表面吸附膜层S、Ca、C含量均增加,表明改性木质素磺酸盐在金属表面吸附点增多,吸附量增大。电化学测试结果表明改性木质素磺酸盐（简称GCL2-D1）属于混合抑制型缓蚀剂,腐蚀介质中掺加100 mg•L^-1GCL2-D1能使腐蚀过程电荷传递电阻从564 Ω增加至20680 Ω,金属/溶液界面电容从2.84 mF降低至0.041 mF,说明改性后的木质素磺酸盐能够在金属表面形成致密的膜层,从而抑制金属腐蚀。     

二氧化铅膜电极用于木质素磺酸盐电氧化反应的研究：Ⅰ.电解条？…

用一种新型电级－ＰｂＯ２膜电极作阳极对木质素磺酸盐溶液进行电氧化反应，研究中发现在电氧化过程中木质素磺酸盐除发生分子链断裂之外，芳香环开环反应也很显著。研究了溶液ｐＨ值，电解电压及电量对芳香环开环反应的影响。结果表明，高ｐＨ值条件对芳香环开环反应有利，这种条件下电压维持在３．０Ｖ左右具有良好的开环效果，电解电量的增加可提高芳香环开环的程度。     

木质素光催化氧化的产物分析及机理浅析

使用GC(气相色谱)-MS(质谱)联用仪对木质素光催化氧化的产物进行分析,从中检出了香兰素、愈创木基丙酮、愈创木基乙酸、1-羟基-3-愈创木基丙酮等具有较高价值的化合物。在木质素的光催化氧化降解反应中,氧化降解和交联并存,两者是一对竞争反应。木质素的氧化可以经愈创木基丙酮和1-羟基-3-愈创木基丙酮、愈创木基乙醇、愈创木基乙酸而获得香兰素,然后继续氧化成分子量更小的化合物,直至变成水和CO2。愈创木基乙醇的氧化是氧化过程的控制反应。氧化与交联的并存,使得反应过程中木质素的平均分子量呈现出先增大后减小的趋势,相应地分子量分布是先变窄后变宽,而峰值分子量则持续增加。同时交联反应的存在也降低了木质素氧化生成小分子产物的效率,而且反应时间越长,小分子化合物产率越低。     

二氧化铅膜电极用于木质素磺酸盐电氧化反应的研究──Ⅰ.电解条件对电氧化过程中芳香环开环反应的影响

用一种新型电极—PbO2膜电极作阳极对本质素磺酸盐溶液进行电氧化反应,研究中发现在电氧化过程中木质素磺酸盐除发生分子链断裂之外,芳香环开环反应也很显著。研究了溶液pH值、电解电压及电量对芳香环开环反应的影响。结果表明,高pH值条件对芳香环开环反应有利,这种条件下电压维持在3．0V左右具有良好的开环效果,电解电量的增加可提高芳香环开环的程度。     

不同分子量麦草碱木素性能及其对LPF胶性能的影响

应用超滤分级方法,将麦草碱木素分成3种不同分子量范围的级分。分析表明：随着分子量的降低,麦草碱木素的甲氧基含量降低,酚羟基含量升高,其反应活性随之升高;同时,羧基含量降低,其溶液表面活性升高。进一步实验结果表明,随着麦草碱木素分子量的降低,LPF胶的胶黏强度升高,游离甲醛含量和黏度降低,综合性能提高。     

The effect of molecular weight on the cross section and properties of polyacrylonitrile precursor and resulting carbon fiber

In this study, we investigated the effect of molecular weight in the range 1.65?4.29 × 10⁵ (M _w) on the cross section, surface, thermal, and mechanical properties of polyacrylonitrile (PAN) precursor and its resulting carbon fiber. From the results, it can be seen that the molecular weight, with the same solid content of polymer, changes from 1.65 × 10⁵ to 4.29 × 10⁵ and the cross section of PAN precursor changes from a circular shape with no notable grooves surface to a been shape with a surface containing deep and straight grooves. PAN precursor with higher molecular weight has a higher onset of exothermic temperature and a higher peak temperature, but has a higher aromatization index (AI value) due to its thin and flat cross section, which causes rapid cyclization during oxidation. An increase in molecular weight results in an increase in crystal size and preferred orientation and a decrease in average pore diameter. This decrease can improve the mechanical properties of PAN precursor and its resulting carbon fiber.     

浸渍用酚醛树脂的合成研究

采用优化工艺聚合得到的PF树脂的固含量为51.1%.数均分子量(-mn)和重均分子量为(-mw)分别为267和331,分子量主要分布在200～400之间,分散指数为1.24,表面张力较小且变化平缓,具有较好的渗透性能,同时,游离酚和游离醛的含量低.     

Surface segregation of polyethylene in low‐density polyethylene/ethylene–propylene–diene rubber blends: Aspects of component structure

Aspects of the molecular weight and its distribution, the branching of low‐density polyethylene (LDPE), and the molecular composition of the ethylene–propylene–diene rubber (EPDM) matrix are presented in this article in terms of their influence on the surface segregation of polyethylene (PE) in elastomer/plastomer blends. All of the PEs studied, despite different weight‐average molecular weights and degrees of branching, segregated to the surface of the LDPE/EPDM blends. Atomic force microscopy pictures demonstrated defective crystalline structures on the surface of the blends, which together with a decrease in the degrees of their bulk crystallinity and a simultaneous increase in their melting temperatures, pointed to a low molecular weight and a defective fraction of PE taking part in the surface segregation. The extent of segregation depended on the molecular structure of the EPDM matrix, which determined the miscibility of the components on a segmental level. The higher the ethylene monomer content in EPDM was, the lower was the PE content in the surface layer of the blends. The composition and structure of the surface layer was responsible for its lower hardness in comparison with the bulk of the blends studied. The surface gradient of the mechanical properties depended on the physicochemical characteristics of the components and the blend composition, which created the possibility of tailoring the LDPE/EPDM blends to dedicated applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 625–633, 2006     

Influence of temperature,molecular weight,and molecular weight dispersity on the surface tension of polystyrene,polypropylene, and polyethylene. II. Theoretical

Experimental data for the surface tension of polystyrenes of different molecular weights (3400–200,000) and different molecular weight dispersities (1–3) and of different polyolefins are compared with the predictions of the Patterson–Rastogi and Dee–Sauer cell theories, which infer the surface tension from pressure–volume–temperature (PVT) data. PVT data for these polymers were obtained from the literature and experimentally and are fitted to the Flory–Orwoll–Vrij equation of state. Both theories predict that the surface tension will decrease linearly with increasing temperature and increase with molecular weight, thereby corroborating the experimental data. However, both theories underestimate the entropy change in the surface formation per unit area at a constant volume for low molecular weight and polydisperse systems and underestimate the effect of molecular weight dispersity on surface tension. Both theories feature two parameters, m and b, that quantify the enthalpic and entropic contributions to surface tension. The theoretical predictions are fitted to the experimental data for monodisperse polystyrene (with a molecular weight above the molecular weight of entanglement), polypropylene, and linear low‐density polyethylene to quantify the enthalpic contribution to surface tension. b is then evaluated as a function of molecular weight and molecular weight dispersity and is found to decrease with increasing molecular weight and to increase with increasing molecular weight dispersity, showing that end‐group excess at the surface has some effect on surface tension. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2201–2212, 2002     

Development of potentially degradable materials for marine applications. II. Polypropylene-starch blends

The effect of exposure of unstabilized polypropylene-starch blends, with or without a metal catalyst (e.g., cobalt (III) acetylacetonate), autooxidant (e.g., fatty acid), and a metal containing plasticizer (e.g., aluminum stearate) to the marine environment was studied for about six weeks at two different locations in New Jersey. Starch tends to absorb water. Unstabilized polypropylene degrades significantly during processin in air, as indicated by melt index values. Thus, for blends of unstabilized polypropylene-starch (no additives), prepared under controlled conditions and exposed to plain seawater, there seems to be no microbial activity or chemical degradation, as indicated by no surface erosion and practically no change in molecular weight and tensile properties. However, for unstabilized polypropylene starch blends containing metal catalyst, auto-oxidant, or plasticizer exposed under soft mud, surface erosion due to microbial activity is evident. In addition, chemical degradation due to the presence of degradative additives has been confirmed, as observed by a decrease in molecular weight and tensile properties. Changes in thermal characteristics of these blends after exposure to the marine environment have been studied.     

宽峰或双峰分布两段聚合聚乙烯树脂性能研究

用两段淤浆聚合工艺合成了具有宽峰或双峰相对分子质量分布的高密度聚乙烯（HDPE）／（乙烯／丁烯-1）共聚树脂的反应釜共混聚合物。随着丁烯-1用量的增加，共混物的密度、熔点、结晶度、拉伸屈服应力减小，而断裂伸长率增加。随着高相对分子质量共聚物的含量增加，熔点、密度、结晶度减小，相对分子质量分布的双峰特性也更明显。通过调整两段聚合物的熔体流动速率、两段聚合物之比来控制相对分子质量大小及其分布。控制第一段小分子数目，增加第二段相对分子质量或减小密度可获得最大耐环境应力开裂性能。     

How Does the Preparation of Rye Porridge Affect Molecular Weight Distribution of Extractable Dietary Fibers?

Extractable dietary fiber (DF) plays an important role in nutrition. This study on porridge making with whole grain rye investigated the effect of rest time of flour slurries at room temperature before cooking and amount of flour and salt in the recipe on the content of DF components and molecular weight distribution of extractable fructan, mixed linkage (1→3)(1→4)-β-d-glucan (β-glucan) and arabinoxylan (AX) in the porridge. The content of total DF was increased (from about 20% to 23% of dry matter) during porridge making due to formation of insoluble resistant starch. A small but significant increase in the extractability of β-glucan (P = 0.016) and AX (P = 0.002) due to rest time was also noted. The molecular weight of extractable fructan and AX remained stable during porridge making. However, incubation of the rye flour slurries at increased temperature resulted in a significant decrease in extractable AX molecular weight. The molecular weight of extractable β-glucan decreased greatly during a rest time before cooking, most likely by the action of endogenous enzymes. The amount of salt and flour used in the recipe had small but significant effects on the molecular weight of β-glucan. These results show that whole grain rye porridge made without a rest time before cooking contains extractable DF components maintaining high molecular weights. High molecular weight is most likely of nutritional importance.     

偏氯乙烯-氯乙烯悬浮共聚树脂的分子质量及分布

在5L聚合釜中合成了偏氯乙烯(VDC)-氯乙烯(VC)悬浮共聚树脂，研究了聚合温度、转化率、单体配比和助剂对分子质量及分布的影响．结果表明，共聚树脂的分子质量与聚合温度的关系符合Arrhenius方程，其综合活化能为-32．877kJ／mol；聚合物的特性黏数在高转化率阶段基本不变；分子质量随着单体配比中VC含量的增加而降低、分子质量分布也有一定的波动；聚合前加入助剂对共聚树脂的分子质量及分布影响不大。     

Effect of oven aging on polypropylene

Injection-molded tensile bars of unstabilized polypropylene were oven aged at 90°C. After an induction period, tensile elongation decreased catastrophically. During the induction period no evidence of oxidation was observed by infrared reflectance; however, a definite surface etching was noted by electron microscopy. Differential scanning calorimetry measurements indicated that, for samples aged beyond the induction time, oxidative degradation caused a decrease in the melting temperature of polypropylene. Toluene immersion was used to remove selectively material from the surface of tensile bars aged for various times. Using this technique, changes in melting behavior were observed for partially aged polypropylene even prior to the catastrophic decrease in tensile elongation. Similarly, oxidation products and a reduction in molecular weight were detected for the dissolved surface layer during the apparent induction time. Results indicate that molecular weight measurement is the most sensitive indicator of oxidative degradation during the induction period.