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1.
木粉/聚乙烯复合材料的等离子体表面处理——等离子体处理时间对复合材料表面特性的影响 总被引:4,自引:1,他引:3
为改善木粉/聚乙烯复合材料的表面粘接性,实现木粉/聚乙烯复合材料的无缝连接,利用低温等离子体处理技术,对木粉/聚乙烯复合材料进行了表面处理.采用接触角测试、傅立叶变换红外光谱分析(FTIR)以及X射线光电子能谱分析(XPS)研究了等离子体处理前后复合材料表面性能的变化.试验结果表明,经等离子体处理后,复合材料表面的接触角减小,表面润湿性得以改善;FTIR分析结果表明,经等离子体处理后,复合材料表面有—OH、—C=O和—O—C=O基团生成;XPS分析表明,经等离子体处理后,复合材料表面含氧基团的含量增加,在较短的时间内表面氧元素含量增加会达到平衡,且生成大量的—O—C=O基团。 相似文献
2.
橡胶木粉填充LLDPE复合材料的结构和力学性能 总被引:6,自引:0,他引:6
用橡胶木粉填充线性低密度聚乙烯(LLDPE),研究了酸、碱溶液预处理木粉的效果和硅烷偶联荆(KH-570)、MMA接枝的天然橡胶胶乳(MGL-30)两种改性剂对橡胶木粉表面改性的效果,以及未粉粒径和填充量等对木粉/LLDPE复合材料力学性能的影响,并用SEM对复合材料拉伸断面的形态结构进行了分析。结果表明:木粉的拉径、木粉填充量和改性荆用量对复合材料的力学性能有较大的影响,经碱溶液预处理再用改性荆改性后的木粉能有效地改善木粉与LLDPE的界面粘结强度,提高橡胶木粉/LLDPE复合材料的力学性能。 相似文献
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《高分子通报》2015,(7)
通过静电纺丝技术制备了聚乙烯醇(PVA)纳米纤维膜,研究了热压处理的条件(温度、压力、时间)对提升PVA纤维膜水稳定性的影响。随着热压温度的增加,PVA纤维膜的水稳定性增强,红外测试显示,不同温度(50℃、100℃、155℃)热压处理,水稳定性增强的机理不同。扫描电镜照片及水稳定性测试表明,与单纯加热处理相比,热压处理可在较低温度下达到较高温度的效果,压力起到了协同作用。热压压力大于4MPa后,纤维膜的水稳定性无明显提升,热压时间对不同温度处理的PVA纤维膜的水稳定性影响有明显差异。综合考虑PVA的性能和水稳定性,最佳热压处理条件为100℃,4MPa,2min。 相似文献
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在转矩流变仪中用熔融接枝法制备马来酸酐(MAH)和苯乙烯(St)接枝聚丙烯(PP)-PP-g-(MAH/St)和PP-g-MAH,将其作为聚丙烯/木粉复合材料的相容剂。 FTIR证实MAH和St单体与PP发生接枝反应。 用SEM和DSC等手段考察两种相容剂对PP/木粉复合材料微观形貌和结晶性能的影响,探索了各种PP/木粉复合材料加工和力学性能不同的内在原因。 SEM显示,PP-g-(MAH/St)改性木粉比PP-g-MAH改性木粉在PP基体中分散性更佳,木粉与PP的界面更加模糊,相容性进一步改善。 DSC结果表明,PP-g-(MAH/St)改性体系可增强木粉对PP的异相成核作用,提高结晶温度和结晶度。 复合材料的加工和力学性能测试结果表明,PP-g-(MAH/St)改性效果明显优于PP-g-MAH。 复合材料的熔体质量流动速率随相容剂用量的增加而逐步下降,PP-g-(MAH/St)改性体系拉伸强度和弯曲强度却逐步上升,并在相容剂用量为4.8 g/100 g PP时达到极值。 此时其拉伸强度达40.62 MPa,分别是未改性体系和PP-g-MAH改性体系的1.29和1.17倍;其弯曲强度达45.72 MPa,分别是未改性体系和PP-g-MAH改性体系的1.23和1.59倍;而无缺口冲击强度却在相容剂用量为3.6 g/100 g PP时达到极值13.35 kJ/m2,分别是未改性体系和PP-g-MAH改性体系的1.62倍和1.42倍。 相似文献
7.
应用水热热压技术制备了各种USY型分子筛-高岭土的固化成型体,并对其进行物相分析、表面酸性以及对正十五烷裂解的催化性能测定。实验结果表明:USY型分子筛与高岭土的固化体具有较强的B酸中心,而几乎没有L酸中心。135℃下得到的固化体对n-十五烷的裂解活性及汽油转化率都高于未经处理的样品。水热热压固化温度是影响固化体性能的重要条件,可以利用固化体组分的改变及固化条件的控制来调节固化体表面酸性及其催化性能。 相似文献
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选用甲基丙烯酸缩水甘油酯接枝乙烯辛烯共聚物(POE-GMA)和聚乳酸、木粉在Haake转矩流变仪中熔融共混.通过拉伸、冲击、差示扫描量热、扫描电镜等测试方法对共混复合材料的性能进行了研究.结果表明:聚乳酸木塑复合材料的拉伸强度和弯曲性能随POE-GMA添加量的增加而减小;POE-GMA的加入使聚乳酸木塑复合材料的结晶温度下降,结晶度升高;当m(PLA)∶m(WF)∶m(POE-GMA)=80∶20∶20时,复合材料的表面自由能最低,接触角最大,吸水性最低;随着木粉含量的增加,复合材料的起始热降解温度降低,POE-GMA的含量增加对聚乳酸木塑复合材料的起始热降解温度影响不大. 相似文献
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Jasna Simonović Jasna Stevanic Daniela Djikanović Lennart Salmén Ksenija Radotić 《Cellulose (London, England)》2011,18(6):1433-1440
The mechanical and physical properties of wood fibres are dependent on the organisation of their constituent polymers (cellulose,
hemicellulose and lignin). Fourier Transform Infrared (FTIR) microscopy was used to examine the anisotropy of the main wood
polymers in isolated cell wall fragments from branches of maple and Serbian spruce. Polarised FTIR measurements indicated
an anisotropy, i.e. orientation of the cellulose microfibrils that was more or less parallel to the longitudinal axis of the
cell wall. The hemicelluloses, glucomannan and xylan appeared to have a close link to the orientation of the cellulose and,
thus, an orientation more parallel to the axis of the cell wall. An important result is that, in both maple and spruce samples,
lignin was found to be organised in a parallel way in relation to the longitudinal cell wall axis, as well as to the cellulose.
The results show that, despite the different lignin precursors and the different types of hemicelluloses in these two kinds
of wood, lignin has a similar orientation, when it comes to the longitudinal axis of the cell wall. 相似文献
12.
Historical or archaeological wooden objects are generally better conserved in wet environments than in other contexts. Nevertheless, anaerobic erosion bacteria can slowly degrade waterlogged wood, causing a loss of cellulose and hemicellulose and leading to the formation of water-filled cavities. During this process, lignin can also be altered. The result is a porous and fragile structure, poor in polysaccharides and mainly composed of residual lignin, which can easily collapse during drying and needs specific consolidation treatments. For this reason, the chemical characterization of archaeological lignin is of primary importance in the diagnosis and conservation of waterlogged wood artifacts. Current knowledge of the lignin degradation processes in historical and archaeological wood is extremely inadequate. In this study lignin extracted from archaeological waterlogged wood was examined using both Py-GC/MS, NMR spectroscopy and GPC analysis. The samples were collected from the Site of the Ancient Ships of San Rossore (Pisa, Italy), where since 1998 31 shipwrecks, dating from 2nd century BC to 5th century AD, have been discovered. The results, integrated by GPC analysis, highlight the depolymerization of lignin with cleavage of ether bonds, leading to an higher amount of free phenol units in the lignin from archaeological waterlogged wood, compared to sound lignin from reference wood of the same species. 相似文献
13.
Rebecca Hollertz Hans Arwin Bertrand Faure Yujia Zhang Lennart Bergström Lars Wågberg 《Cellulose (London, England)》2013,20(4):1639-1648
We present in this study a quantitative estimate of the dispersive interactions between lignin, hemicellulose and cellulose, which are the dominating components in wood and also extensively used to produce paper and packaging materials. The dielectric properties in the UV-visible region of spin-coated films of pure lignin and glucomannan were determined by spectroscopic ellipsometry. The non-retarded Hamaker constants were estimated from the determined spectral parameters using Lifshitz theory for lignin and glucomannan interacting with cellulose, titania and calcium carbonate in vacuum, water and hexane. The Hamaker constants for the different combinations of cellulose, lignin and glucomannan fall within a relatively narrow range of 35–58 and 8–17 zJ, for the values in vacuum (air) and water, respectively. The estimated Hamaker constants for the interactions of the wood components with TiO2 and CaCO3, common additives in paper, in water range from 3 to 19 zJ, thus being similar in magnitude as the interactions between the wood components themselves. In contrast, the Hamaker constant is essentially zero for glucomannan interacting with calcium carbonate in hexane. The Hamaker constants for lignin, hemicellulose and cellulose determined in this study can provide information regarding the surface interactions important for e.g. adhesion, friction, swelling and wetting in paper processing as well as for the resulting behavior of paper products. 相似文献
14.
Impregnation mode in wood plastic composite 总被引:1,自引:0,他引:1
M. Mozaffar Husain Mubarak A. Khan M. Azam Ali K.M. Idriss Ali A.I. Mustafa 《Radiation Physics and Chemistry》1996,48(6):781-786
Bulk monomer MMA was impregnated into simul, a fuel wood of Bangladesh, under vacuum and under normal temperature and pressure conditions in order to compare the mode of impregnation and its effect on various characteristic parameters of wood plastic composites. Methanol (MeOH) was used as the swelling solvent with methylmethacrylate (MMA) at MMA: MeOH = 70:30, v/v. Impregnation of the bulk monomer was very high under vacuum compared to that at normal condition; but the difference of grafting of MMA to the wood cellulose under these two impregnating conditions was much lower as compared to that of the uptakes of impregnating solution MMA + MeOH under these two modes of impregnation. Incorporation of additives to MMA + MeOH has substantially enhanced grafting, tensile strength, bending strength and compression strength of thcomposite of such an extent that there is virtually very little difference between vacuum impregnation and normal impregnation. Considering the available data it is suggested that the impregnation under normal condition is preferable beacuse different substrates of various sizes and shapes can be suitably impregnated under normal condition while vacuum impregnation has several limitations in this respect. 相似文献
15.
Slawomir Borysiak 《Journal of Thermal Analysis and Calorimetry》2013,113(1):281-289
Results of the hitherto research work on alkalisation of lignocellulosic materials have been much divergent. In view of the above, the subject of this study is mercerization of cellulose from pine wood. This choice of the subject permitted observation of transformation of cellulose I to cellulose II with no participation of other components of lignocellulosic materials. According to X-ray results, during mercerization the isolated cellulose was easily (completely) transformed into cellulose II variety, while the pine wood was converted more slowly to cellulose II polymorphs. Therefore, it could be concluded that the presence of lignin and hemicelluloses in wood prevented the transformation from cellulose I to II. The main objective of this research was to establish the effect of cellulose varieties on the nucleation ability of different fillers by using differential scanning calorimetry (DSC) and polarizing microscopy. The nucleating effect of the fillers occurs only in the presence of cellulose I variety. In contrast, the presence of cellulose II variety seems to practically eliminate the nucleating effect of the fillers. Moreover, nucleation of the mercerized wood (mixture of cellulose I and II) can be also observed, but this effect is not strong. It should be emphasised that as yet no correlation has been reported between the quantitative composition of cellulose polymorphic forms (appearing not only in wood, but in cellulose isolated from wood as well) and the nucleation ability of lignocellulosic fillers. 相似文献
16.
Hatem Abushammala Hubert Hettegger Markus Bacher Philipp Korntner Antje Potthast Thomas Rosenau Marie-Pierre Laborie 《Cellulose (London, England)》2017,24(7):2767-2774
Cellulose acetylation has been reported as a side reaction of cellulose treatment with the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) (Karatzos et al. in Cellulose 19:307–312, 2012) and other 1,3-dialkylimidazolium acetate ionic liquids. 1-Acetylimidazole (AcIm), an [EMIm][OAc] impurity, has been found to be the actual acetylating agent (Zweckmair et al. in Cellulose 22:3583–3596, 2015), and the degree of acetylation was relatively low, below a DS of approx. 0.1%. Higher degrees of cellulose acetylation (DS > 10%) have been observed when the entire wood was mixed with [EMIm][OAc] instead of cellulosic pulp only (Abushammala et al. in Carbohydr Polym 134:609–616, 2015). In this paper, we explore the impact of wood constituents, mainly lignin, on cellulose acetylation using AcIm. The results demonstrate that lignin itself can be readily acetylated upon mixing with AcIm, and—noteworthy—that lignin presence significantly accelerates cellulose acetylation. The initial rate of cellulose acetylation by AcIm increased from 1.8 to 4.7%/h when only 1% of lignin, based on cellulose mass, was added. A mechanistic study employing cellulose and lignin model compounds showed lignin to be more susceptible to acetylation than cellulose and to act as an intermediate acetyl group source for further cellulose acetylation in a catalytic scenario. 相似文献
17.
The chemistry and kinetic behavior of Cu-Cr-As/B wood preservatives. I. Fixation of chromium on wood
A. Pizzi 《Journal of polymer science. Part A, Polymer chemistry》1981,19(12):3093-3121
The kinetic behavior of CrO3 in its reaction with wood has been elucidated. Various reactions take place between CrO3 and the lignin and cellulose in wood. CrO3 reacts with cellulose in a two-step reaction: the first step is an adsorption of CrVI onto the cellulose to form CrVI/cellulose activated complexes. The second step is a CrVI → CrIII reduction taking place on the cellulose surface. The CrIII formed is only physically adsorbed to the cellulose or very weakly bound as small amounts of CrIII can be released into the reaction medium. The CrVI adsorbed by cellulose appears mainly to be reduced to CrIII. The reaction of CrVI with lignin has been shown to be the composition of the three successive reaction of Cr2O72?, HCrO4?, and CrO42? with the guaiacyl units of lignin. Insoluble and stable CrVI/lignin complexes in which chromium maintains its hexavalent oxidation state are formed. Rate constants and energies of activation for all the reactions have been determined. The fixation of CrO3-derived compounds on wood has been explained as the combination of the various reactions investigated. The results indicate that 60% of Cr is fixed irreversibly to the lignin of wood as CrVI and 40% is weakly bound, probably just precipitated, on the cellulose surface as CrIII of which small amounts can be released in a water medium. The complex CrVI and CrIII species forming complexes with the guaiacyl units have been identified. 相似文献
18.
A. Pizzi 《Journal of polymer science. Part A, Polymer chemistry》1982,20(3):707-724
The kinetic behavior of a Cr6+/Cu2+ system in its reaction with wood has been elucidated. The same reactions with carbohydrates and lignin of wood for CrVI alone are still present. Approximately 20% of the copper is fixed to the guaiacyl units of lignin in the form of copper chromate; the remaining copper forms complexes with cellulose and mainly with the guaiacyl units of lignin. The CrVI/lignin guaiacyl unit complexes already found for the treatment of wood with CrO3 are still the main CrVI complexes formed. Copper chromate is present as [Cu(H2O)2(guaiacol)]CrO4(guaiacol) complexes, and CuCrO4 bridges between different guaiacyl units of the lignin network appear to be likely. Substantial interference of the Cu2+ ions in the second-zone reactions of CrVI with wood occurs. The amount of CrVI and CrIII fixed onto lignin and cellulose compares well with experimental values. Rate constants, energies of activation, and Arrhenius equations of the various reactions have been obtained. The amount of Cu2+ interference in the reaction has also been calculated. 相似文献
19.
Amin Ibrahim Philip B. Oldham Terrance E. Conners Tor P. Schultz 《Microchemical Journal》1997,56(3):393-402
FT-Raman spectroscopy is used for the rapid measurement of wood pulp lignin. A total of 23 western softwood pulp samples with known kappa numbers (10–38) are used. Each sample is divided into three portions and scanned separately. The integrated area of the lignin band at approximately 1600 cm−1is ratioed against the integrated area of the cellulose bands in the 1200–1010 cm−1region and correlated to known kappa numbers. The measured ratios behave linearly with the kappa number (r= 0.99) and can be reproducibly determined with an error of approximately 2% or less. The data are presented and discussed in view of the potential for at-line analysis of lignin associated with chemical delignification of wood pulp. 相似文献
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Klaus Fischer 《Macromolecular Symposia》1987,12(1):303-322
The effect of high-energy radiation on wood and cellulose was investigated. By irradiation of beech wood, changes in lignin, in carbohydrates and in wood structure take place. Furthermore, new lignin carbohydrate complexes are formed. A way is shown to prevent undesirable reactions. Irradiated pulp possesses a lower degree of polymerization and a higher accessibility for chemical reactions. Processing irradiated pulp to viscose fibres will be more efficient. 相似文献