烯丙基化碳纳米管改善丙烯酸酯压敏胶的性能

本文利用γ-甲基丙烯酰氧基丙基三甲氧基硅烷(KH570)对多壁碳纳米管(MWNTs)进行修饰使其表面接枝上烯丙基官能团,与丙烯酸酯类单体进行原位聚合,制备了一种耐高温丙烯酸酯压敏胶(PSA)。 通过傅里叶变换红外光谱仪(FT-IR)、热重分析仪(TGA)和扫描电子显微镜(SEM)表征了MWNTs和丙烯酸酯PSA的结构与性能,探讨了改性MWNTs的质量分数对PSA耐热性能和粘接性能的影响。 结果表明,与未改性的丙烯酸酯PSA相比,当改性MWNTs的质量分数为1.5%时,改性丙烯酸酯PSA的耐热性能和粘接性能最佳,热分解温度从360 ℃提高到了382 ℃,耐热温度从80 ℃提高到了155 ℃,初粘力、持粘力和180°剥离强度分别从2 h和13.66 N/(25 mm)(12号小球)提高到了27 h和17.34 N/(25 mm)(17号小球)。     

表面活性剂对完全液相法制Cu-Zn-Al浆状催化剂结构和性能的影响

采用完全液相法制备了Cu-Zn-Al双功能浆状催化剂, 利用不同类型表面活性剂对其进行了修饰和改性. 通过N2气吸附、XRD和XPS等方法考察了表面活性剂类型对催化剂织构、物相以及表面性质的影响, 采用浆态床反应装置对其合成气一步法制备二甲醚的催化活性进行了评价, 讨论了催化剂结构与性能的关系. 结果表明, 表面活性剂主要是通过与活性金属的作用调节催化剂的表面性质、孔结构、相结构以及晶粒大小, 进而影响催化剂的催化活性; 非离子表面活性剂总体上对催化剂的性能有促进作用, 阳离子表面活性剂和阴离子表面活性剂对催化剂性能存在不利影响; 表面活性剂与活性金属作用的强弱是影响性能的关键.     

三(3-乙炔基苯胺)-苯基硅烷改性含硅芳炔树脂的性能

以苯基三氯硅烷、3-氨基苯乙炔为原料,通过胺解反应合成了三(3-乙炔基苯胺)苯基硅烷(SZTA),并通过傅里叶变换红外光谱(FT-IR)和核磁共振氢谱(1 H-NMR)表征了其结构。随后通过熔融共混的方法制备了不同配比的改性含硅芳炔树脂(PSA/SZTA),借助黏度计、流变仪、差示扫描量热仪(DSC)、电子万能试验机、热重分析仪(TG)等考察了改性树脂的工艺性能、固化特性、弯曲性能、热稳定性能和热解动力学等。结果显示,引入SZTA后,改性PSA树脂的黏度降低62%;改性PSA树脂固化物的弯曲强度最高达到34.6MPa,比未改性的PSA树脂提高了约54%;且改性树脂固化物在N_2中的5%热失重温度(T_(d5))均高于500℃,保持了良好的耐热性能;PSA/SZTA-20固化物的热解表观活化能(Ea)的平均值为249kJ/mol。     

混合改性PAN纳米纤维铁配合物的吸附-催化双功能在有机染料去除中的应用

将静电纺丝法制备的聚丙烯腈(PAN)纳米纤维膜用不同比例的盐酸羟胺和水合肼混合溶液改性,再与Fe3+离子进行配位反应,制备了5种不同表面结构的改性PAN纳米纤维铁配合物;考察了水合肼加入量对纤维铁配合物的制备及对偶氮染料活性红195去除能力的影响.结果表明,随着水合肼加入量的增大,改性PAN纳米纤维的直径减小且其铁配合物表面的铁离子配合量降低;3种混合改性PAN纳米纤维铁配合物均对活性红195具有优良的吸附和光催化降解功能,可通过2种功能之间的协同效应实现快速去除水溶液中染料分子的目的.     

硝酸改性活性炭上氧/氮官能团对脱汞性能的促进作用

采用硝酸氧化手段对活性炭进行了表面处理, 并在固定床反应器上测试了其脱除单质汞的性能. 研究表明, 在模拟烟气中硝酸改性活性炭能有效脱除单质汞. 采用元素分析、Brunauer-Emmett-Teller (BET)比表面积、扫描电子显微镜(SEM)、拉曼(Raman)光谱、Boehm滴定、程序升温脱附(TPD)和X射线光电子能谱(XPS)等手段研究了活性炭表面官能团对其脱汞性能的影响. 结果表明: 硝酸氧化处理能同时增加活性炭表面含氧官能团和含氮官能团的含量. 与改性活性炭的物理性质相比, 其化学性质对脱汞性能的影响更大, 单质汞主要被改性活性炭氧化为HgO而去除. 在脱汞反应中, 羰基、酯基和酸酐等含氧官能团可能是活性吸附位点, 反应后这些官能团被还原为羟基或者醚基; 而吡咯等含氮官能团可能是活性催化位点. 此外, 基于上述表征结果提出了硝酸改性活性炭表面官能团的脱汞机制.     

烷基化改性壳聚糖制备条件对酚类化合物吸附的影响

采用脂肪醛与壳聚糖反应生成Schiff's碱,再用NaBH4还原制备了N-烷基化壳聚糖衍生物. 用元素分析测定了其取代度. 考察了不同烷基化条件对庚醛改性壳聚糖取代度和吸附性能的影响. 结果表明,反应时间、醛/壳聚糖配比和反应温度等因素影响烷基化壳聚糖的取代度. 在n(醛)∶ n(壳聚糖)=4∶ 1、反应温度为100 ℃和反应时间为8 h条件下,庚醛改性壳聚糖的取代度趋于最大值,取代度的增加有利于改性壳聚糖对2,4-二氯酚的吸附. 不同链长脂肪醛改性壳聚糖对酚的吸附影响结果表明,随着烷基化链长的增加,改性壳聚糖产物对酚的吸附量增加,但链长超过7个C时,吸附量反而下降.庚醛改性壳聚糖的吸附效果最好.     

超疏水多孔硅的制备及表面稳定性

在加热条件下采用氢化硅烷化反应对多孔硅表面进行改性, 通过扫描电子显微镜、 红外光谱及元素分析等手段表征了多孔硅改性前后的结构和组成, 研究了不同反应时间对其性能的影响. 结果表明, 反应3 h后制得了超疏水表面的多孔硅, 其在碱性及空气环境中具有良好的稳定性.     

Ga、Zn改性方法对HZSM-5催化剂丙烯芳构化性能的影响

以浸渍法和水热合成法对ZSM-5分子筛进行Ga、Zn改性,制得不同酸性的分子筛催化剂。采用XRD、SEM、NH3-TPD和XPS等表征手段,研究考察了Ga、Zn和不同引入方法对催化剂的孔结构、骨架结构特性和表面酸性的影响,并以丙烯芳构化为模型反应,考察了Ga、Zn改性对ZSM-5催化剂烯烃芳构化催化性能的影响。研究结果表明,Ga、Zn改性对催化剂形貌影响较小,但能明显改变催化剂的表面酸性和烯烃芳构化性能。Zn改性能降低催化剂的酸性,而Ga改性与其引入的方式有关,浸渍法引入催化剂的中强酸位略有下降,而水热合成法引入则显著增加了催化剂的总酸量。Ga、Zn改性均提高了芳构化反应的活性和芳烃选择性,并抑制催化剂表面积炭。     

功能化聚丙烯腈纤维促进有机反应的研究进展

聚丙烯腈纤维(PANF)具有出色的机械强度、耐化学性和良好的热稳定性,而且易于进行改性.在聚丙烯腈纺丝原液中加入添加剂或功能单体,或对PANF进行热处理等方法可以实现物理改性.而PANF的化学表面改性包括胺化、酰胺化、氧化、还原、交联、水解、酸处理和化学枝接等方法,表面改性给PANF带来许多特殊官能团,使其可以进一步被用作有机物、有机配体、酶以及过渡金属的载体.通过负载催化活性位点从而得到具有催化活性的功能化PANF.近年功能化PANF作为非均相催化剂被广泛应用于有机合成领域,综述了功能化PANF催化剂在有机反应中的研究成果与进展,包括缩合反应、偶联反应、加成反应、氧化还原反应及多组分一锅法反应等.介绍了纤维催化剂的合成及结构,讨论了催化性能,分析了可能的催化机理,为开发更优的功能化PANF做铺垫.     

纳米TiO_2表面有机化改性的研究

本文依次采用2,4-甲苯二异氰酸酯(TDI)和丙烯酸羟乙酯(HEA)对纳米TiO2表面进行有机化改性,通过FT-IR、激光粒度分析和分散性测试表征其表面的结构并对改性前后的性能进行了比较.结果表明,TDI- HEA与TiO2表面的羟基发生了反应,表面化学键接的TDI-HEA量在40℃较20℃高,并随TDI-HEA/TiO2摩尔比的增大迅速增加,当摩尔比达0.4时趋于平缓,达到10.46%.在非极性有机溶剂中,改性后的TiO2分散性较未改性时有了明显的提高.     

Molecular and nanoscale factors governing pressure‐sensitive adhesion strength of viscoelastic polymers

Pressure‐sensitive adhesives (PSAs) are finding increasing applications in various areas of industry and medicine. PSAs are a special class of viscoelastic polymers that form strong adhesive joints with substrates of varying chemical nature under application of light external bonding pressures (1–10 Pa) over short periods of time (1–5 s). To be a PSA, a polymer should possess both high fluidity under applied bonding pressure, to form good adhesive contact, and high cohesive strength and elasticity, which are necessary for resistance to debonding stresses and for dissipation of mechanical energy at the stage of adhesive bond failure under detaching force. For rational design of novel PSAs, molecular insight into mechanisms of their adhesive behavior is necessary. As shown in this review, strength of PSA adhesive joints is controlled by a combination of diffusion, viscoelastic, and relaxation mechanisms. At the molecular level, strong adhesion is the result of a narrow balance between two generally conflicting properties: high cohesive strength and large free volume. These conflicting properties are difficult to combine in a single polymer material. Individually, high cohesive interaction energy and large free volume are necessary but insufficient prerequisites for PSA strength. Evident correlations are observed between the adhesive bond strengths of different PSAs, and their relaxation behaviors are described by longer relaxation times. Innovative PSAs with tailored properties can be produced by physical mixing of nonadhesive long‐ and short‐chain linear parent polymers, with groups at the two ends of the short chains complementary to the functional groups in the recurring units of the long chains. Although chemical composition and molecular structure of such innovative adhesives are unrelated to those of conventional PSAs, their mechanical properties and adhesive behaviors obey the same general laws, such as the Dahlquist's criterion of tack. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Influence of thermal reactive crosslinking agents on the tack,peel adhesion,and shear strength of acrylic pressure-sensitive adhesives

In recent decades, the basic technology of pressure-sensitive adhesive (PSA) acrylics has developed into a sophisticated science. The main properties of acrylic PSAs such as tack, peel adhesion, and shear strength are determined to a large extent by the kind and quantity of crosslinking agents added to the synthesized PSAs. In order to improve their adhesive (tack, peel adhesion) and cohesive (shear strength) properties, a wide range of amino resin thermal crosslinkers are tested. An acrylic PSA based on 2-ethylhexylacrylate, n-butyl acrylate, and acrylic acid was synthesized by performing a radical polymerization in ethyl acetate. After the addition of amino resins to the acrylic PSA and carrying out thermally initiated crosslinking processes to prepare one-sided self-adhesive tapes, their properties were assessed.     

Radiation-thermal crosslinking of polytetrafluoroethylene

The formation of a three-dimensional network in polytetrafluoroethylene (PTFE) exposed to ionizing radiation at temperatures above the crystallite melting temperature—a phenomenon that has been revealed and studied in the last decade—is considered. A change in the structure and properties of PTFE during its radiation-thermal modification under the specified conditions was analyzed. It was shown that such modification imparts to PTFE a set of additional valuable properties including an enhanced modulus and breaking strength, a low creep, a high wear resistance, enhansed radiation resistance and transparency, thus opening new frontiers for practical application of this polymer.     

含噁嗪环硅烷偶联剂对石英纤维/含硅芳炔复合材料性能的影响

从石英纤维(QF)、含硅芳炔树脂(PSA)分子结构特点出发,设计并合成了一种含有噁嗪环和端炔的新型硅烷偶联剂(BCA),并以BCA改善QF/PSA复合材料的界面性能。采用差示扫描量热分析(DSC)、红外光谱分析(FT-IR)、X-射线电子能谱(XPS)及扫描电镜(SEM)等测试手段表征了BCA与QF/PSA复合材料的相互作用和界面改性效果。结果表明:BCA能够分别与PSA和QF形成良好的化学键合,改善复合材料的界面黏结;经w=2.0%的BCA处理后,QF/PSA复合材料的层间剪切强度、弯曲强度分别较未处理前提高了69.1%和68.8%。     

压敏胶粘剂组成、结构及性能的研究进展

压敏胶粘剂是一种柔性可塑性固体物质，由于其具有良好的耐候、耐热、耐油性以及机械强度好等优点，正得到越来越多的应用。介绍了不同种类压敏胶的组成、结构和性能的研究进展。     

Research progress in toughening modification of poly(lactic acid)

Renewable poly(lactic acid) (PLA) exhibits high strength and stiffness. PLA is fully biodegradable and has received great interest. However, the inherent brittleness of PLA largely impedes its wide applications. In this article, the recent progress in PLA toughening using various routes including plasticization, copolymerization, and melt blending with flexible polymers, was reviewed in detail. PLA toughening, particularly modification of impact toughness through melt blending, was emphasized in this review. Reactive blending was shown to be especially effective in achieving high impact strength. The relationship between composition, morphology, and mechanical properties were summarized. Toughening mechanisms were also discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011.     

高强高模单丝纤维模量测定的修正

当测定具有高强度和高模量单丝纤维的力学性能时，应力传感系统将受到很大的拉力，并产生相应的形变。微小的形变与被测高模量样品的形变相比，已达到不可忽略的程度。本文提出模量修正的原理和求算方法，在测定高强高模单丝纤维的模量时，可对仪器的应力传感系统给出相应的模量修正系数，从而得到真实的弹性模量值。本修正方法能作为单丝力学性能测试标准的补充。     

苯并唑类聚合物近期的研究概况(上)

较全面地综述最近几年国内外关于苯并唑类聚合物的化学改性,结构特性和分子模拟的工作,及其在分子复合材料中的近期应用情况,其中上篇主要讲述苯并唑类聚合物的基本性质和近期在化学改性上的研究。     

Tack properties of pressure‐sensitive adhesives

Relevant experiments are essential to clearly understand the role of various molecular (chemical structure, surface energy, composition), experimental (contact time, contact pressure, temperature) or topological (sample roughness and thickness) parameters, on the tack properties of pressure sensitive adhesives (PSA). The “mechano‐optical tack tester” (MOTT) is a novel device that we have developed to provide accurate measurements of both the contact area and the tack strength. The MOTT is designed to apply controlled contact pressures by mean of a quartz prism probe, for determined contact times, onto the surface of PSA samples. The probe is then pulled up at controlled rates while the tearing force (tack strength) and the contact area are plotted versus time. The tack energy is then calculated. Using the MOTT, the influence of various parameters (contact pressure, contact area, sample thickness, …) on the tack properties of PSA samples has been studied. The main result lies in the strong dependence of the tack energy on the sample thickness. This points out that the release energy is close to the interface rather than in the bulk of the PSA films, and is a function of the contact area. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1201–1208, 2000     

Influence of Particle Nucleation in Pressure Sensitive Adhesive Properties: Miniemulsion versus Emulsion Polymerization

Miniemulsion polymerization is a promising approach to produce and tailor pressure sensitive adhesives (PSAs). In this paper, a systematic comparison of the adhesive properties of latexes produced by miniemulsion and conventional emulsion polymerization is presented. Specifically, the influence of the total surfactant concentration, chain transfer agent concentration and chemical composition on the final adhesive properties of the polymer 2-ethyl hexyl acrylate/methyl methacrylate/acrylic acid was discerned using a 2³ factorial design for each polymerization method. In addition to the adhesive properties (i.e., loop tack, peel strength and shear strength), molecular weight distribution, particle size distribution (PSD) and glass transition temperature were analyzed. The results show that under the conditions used in this work, it is possible to produce PSAs using miniemulsion polymerization, a process wherein monomer droplet nucleation is the dominant particle nucleation mechanism. The use of a miniemulsion polymerization process, as opposed to the conventional emulsion technique, produced several differences such as larger particles sizes and narrower molecular weight distributions. Focusing on the PSA films that exhibited adhesive rather than cohesive failure, the PSA films generated via miniemulsion polymerization displayed higher values of loop tack and peel strength compared to those produced via conventional emulsion polymerization. Shear strength results were strongly dependent on the amount of gel content and sol molecular weight for both cases.