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61.
Phenol degradation was carried out in acidic aqueous solution on different crystal structures of PbO2 surfaces at room temperature. Phenol, benzoquinone and maleic acid concentrations were monitored during the electrolysis process. It was determined that β surfaces have higher performance than surfaces on phenol degradation. Then, the effect of crystallinities of pure β-PbO2 surfaces was investigated and found that higher crystallinity increased the efficiency of the phenol degradation process. 相似文献
62.
Hans-Peter Fink Peter Weigel Johannes Ganster Rainer Rihm Jürgen Puls Herbert Sixta Juan Carlos Parajo 《Cellulose (London, England)》2004,11(1):85-98
The supermolecular structure of dissolving pulps produced from hardwood by the organosolv processes Acetosolv, Formacell, and Milox was characterized by physical methods (TEM, WAXS, SAXS, NMR) and compared with conventional Sulfite and standard commercial dissolving pulps. The suitability of the pulps for the NMMO technology was tested by spinning fibres and blowing films, whose structural and mechanical properties have also been determined. With TEM it was shown that the TCF-bleached organosolv pulps have only the primary (Formacell), the primary and S1 (Milox), or mainly the S1 (Acetosolv) layers exposed to the surface, whereas Sulfite pulping exposes the S2 cell wall layer. Especially for Milox and Acetosolv Eucalyptus wood pulps, a reduced degree of crystallinity was found, both with WAXS and NMR. The SAXS results indicate a lower pore intersection length for the new pulps as compared to conventional pulps. Unbleached organosolv pulps show a lower crystallinity, very low pore intersection lengths, and an average crystallite shape different from their bleached counterparts. The dissolution behaviour in NMMO and the processability of the bleached organosolv pulps was satisfactory so far. Fibres and films could be produced with structural and mechanical properties comparable with conventional Sulfite and standard commercial dissolving pulp products. However, unbleached organosolv pulps did not meet the requirements of the NMMO process. 相似文献
63.
聚环氧乙烷为支链的两亲共聚物的表征及性能 总被引:5,自引:0,他引:5
用端基带有甲基丙烯酸酯的聚环氧乙烷大分子单体(PEO—MA)分别与小分子单体苯乙烯(S)、甲基丙烯酸甲酯(MMA)、丙烯酸甲酯(MA)溶液自由基共聚合得到了三种具有不同主链结构的以聚环氧乙烷(PEO)为支链的两亲接枝嵌段共聚物(分别简写为:PS─g─PEO,PMMA─g─PEO,PMA─g─PEO).用GPC、IR、1H─NMR、WAXD和DSC对其结构进行了表征.研究了接校共聚物的结晶性能、乳化性能以及在Williamson反应中相转移催化作用.结果表明,不同主链结构有不同的结晶度,并随支链PEO含量的增加,分子量的增大而提高;其乳化体积和相转移催化反应的转化率均随着共聚物浓度的增加、支链PEO含量的增人而增大,随支链PEO分子量的提高而减小. 相似文献
64.
本文研究了PBT结晶的熔化行为及非晶性组分PSF的加入对PBT结晶度及熔化行为的影响。结果表明:PBT结晶熔化时的DSC双峰图为多重熔化行为而非多晶型的结果;PSF的加入对PBT结晶度影响不大,但对多重熔化行为有明显影响。此乃PSF无定形组分加入后,使PBT结晶速率减慢而形成更完善的PBT结晶之缘故。 相似文献
65.
66.
Mechanochemical pretreatment of hardwood cellulose was conducted by our self-designed pan-mill equipment which has an unique
and smart structure and can exert strong shear forces and pressure on materials in between and break them down. The structure
transformations, including particle size, powder morphology, molecular structure, crystalline structure during milling were
investigated by Laser Diffraction Particle Size Analyzer, SEM, FT-IR and WAXD, respectively. Compared with standard method
of ball-milling, the pan-mill shows a much higher efficiency in mechanochemical pretreatment of hardwood cellulose. The average
particle size reduced to 21 μm and the specific surface area increased to 0.8 m2/g after 40 milling cycles. Mechanical milling also led to collapse of hydrogen bonds and reduction of crystallinity. The
crystallinity index of cellulose powder decreased from its original 65 to 22, after milling for 40 cycles. Thermal analysis
and solubility testing illustrated that pan-milled cellulose has lower thermal stability and higher solubility in aqueous
alkali. 相似文献
67.
热处理对聚噻吩结构性质的影响 总被引:1,自引:0,他引:1
用WAXS、FTIR、TGA方法研究了在氮气和空气中热处理聚噻吩(PT)某些结构性质.氯仿不溶分子量较高样品(PT_2)热稳定性高于氯仿可溶低分子量样品(PT_1).PT_2在氮气中380℃热处理30分钟,结晶度和相干长度都明显增加,可获得多于11个结晶衍射线.PT_1只能在较低温度下热处理,晶性无明显改善.结晶度低分子量大的样品,有利于掺杂进行.掺杂后得到较高的导电率.给出了热处理及掺杂前后的FTIR谱的解释与归属,热处理后688、831-833cm~(-1)明显减弱;经掺杂后出现了五个新吸收带:1016-1024、1105-1110、1196-1201、1323和1632cm~(-1). 相似文献
68.
69.
Poly(?-caprolactone-co-β-butyrolactone) (PCLBL)-based polyurethane (PCLBL-PU) was synthesized and its tensile properties and hydrolytic degradability were investigated in an attempt to improve the degradability of poly(?-caprolactone)-based polyurethane (PCL-PU). PCLBL was synthesized by the ring-opening polymerization of ?-caprolactone (CL) and β-butyrolactone (BL) with stannous octoate as a catalyst. The introduction of a small amount of BL units significantly decreased the crystallinity of PCLBL. The crystallinity of the soft segment of PCLBL-PU also decreased with increasing BL content, and thus its hydrolytic degradation rate was dramatically increased. PCLBL-PU polymerized with PCLBL containing 5.7 mol% of BL units showed very similar tensile properties to PCL-PU, but its hydrolytic degradation rate increased by 100% at 45 °C. 相似文献
70.
取代聚苯胺的聚集态结构 总被引:3,自引:0,他引:3
环取代基及掺杂对聚苯胺分子链结构产生影响的同时也对大分子聚集态结构产生影响.通过对聚合物膜的XRD、SEM研究,表明在所合成的环取代聚苯胺衍生物中,聚合物的结晶性依POT(聚邻甲苯胺)、PDMAn(聚 2,5 二甲氧基苯胺)、PmClAn(聚间氯苯胺)顺序增加;与本征态的比较,质子酸掺杂后聚合物的结晶性有所提高.POT基本上表现出了非晶聚合物的性质; PDMAn具有同质多晶的结构特征,但结晶度较低; PmClAn表现出了典型高分子晶体性质,符合单斜晶系的特征(晶胞参数为a=0.679 nm, b=2.304 nm, c=0.5734 nm, α=90°, β=100.9°, γ=90°).采用HyperChem程序包中的MM+分子力学方法对1H NMR和XRD实验结果进行结构优化,确定了苯式结构/醌式结构为3/2的PmClAn大分子链的构象. 相似文献