水性环氧增强水泥砂浆及其性能研究

利用水性环氧树脂增强水泥砂浆,改善和提高其作为修复材料的力学强度。通过改变水泥与砂的配比、水性环氧树脂添加量、水泥类型、减水剂用量等因素,系统考察了水性环氧树脂对水泥砂浆的综合性能的影响。结果表明,通过水性环氧树脂增强水泥砂浆,其力学强度有数倍的提高,抗压强度可达到近60 MPa,粘结强度达到2.0 MPa。     

具有自修复和形状记忆功能的聚氨酯光敏树脂

利用封端剂的动态可逆特性,设计、制备出含有多处大位阻脲键和结晶性软段的光敏聚氨酯丙烯酸酯(PUTA).光固化后的材料具有较高的弹性、良好的力学性能、自修复性能和形状记忆性能.经热处理修复后,试样的修复效率达70％(拉伸强度3.58?MPa,伸长率250％);软段的结晶转变使材料具有重复塑形以及形状记忆性能,并可在升温后...     

基于多重可逆作用的自修复聚氨酯弹性体的制备及性能

在聚氨酯主链上引入可逆二硫键, 同时使用硼酸构建的硼酸酯键作为可逆交联点, 使聚氨酯内部形成交联网络结构, 制备了一种兼具高强度、 高韧性及高修复效率的自修复聚氨酯弹性体. 红外光谱、 动态力学分析、 力学测试、 电子显微镜及修复测试结果表明, 制备的自修复聚氨酯具有硬而韧的特性, 原样强度高达23.3 MPa, 断裂伸长率可达1177%, 并且修复条件温和, 剪断拼接的试样经60 ℃, 24 h修复后可恢复99%的原样强度, 且该修复过程可重复多次进行. 此外, 该材料还具有多通道修复特性, 通过热修复或水辅助热修复的方式均可实现材料的修复, 并且水辅助热修复速率更快.     

活性氯型丙烯酸酯橡胶的热可逆共价交联

利用热可逆季铵化反应特性,将含叔胺功能基团的聚合物用于活性氯型丙烯酸酯橡胶(ACM)的热可逆共价交联。通过乳液聚合方法合成了丙烯酸丁酯(BA)/4-乙烯基吡啶(4-VP)共聚物交联剂,考察了交联剂用量、模压温度和模压时间对ACM交联程度、力学性能的影响,并通过DSC、变温扭矩测定、热塑再加工成型等方法研究了交联ACM胶样的热可逆性。研究表明,BA-4-VP共聚物交联的炭黑填充ACM胶样拉伸强度可达8.5MPa,并可进行热塑模压成型,再次加工成型后胶样断裂强度增大、伸长率下降。     

环氧大豆油多元醇改性磺酸型水性聚氨酯合成与性能研究

用2-乙基己醇(异辛醇)对环氧大豆油进行开环,生成环氧大豆油多元醇,并利用其对由异佛尔酮二异氰酸酯(IPDI)、聚己内酯二元醇(PCL)和乙二胺基乙磺酸钠(AAS)为主要合成原料的磺酸型水性聚氨酯(SWPU)进行改性,考察了不同多元醇含量对磺酸型水性聚氨酯乳液以及胶膜性能的影响.首先,通过FTIR和1H-NMR证实了环氧大豆油多元醇的合成;然后经过粒径测试、耐水性测试、接触角测试、机械性能测试、TG测试等检测表明:磺酸型水性聚氨酯成功合成,随着多元醇含量的增加,水性聚氨酯乳液粒径逐渐增大;胶膜的吸水率逐渐减小,并趋于平缓;力学性能拉伸强度逐渐增强,而断裂伸长率下降.但当环氧大豆油多元醇添加量过大时,导致最后乳液无法分散,乳化失败.当多元醇含量与PCL质量比为0.2时,胶膜吸水率由50.14%减小至12.27%,接触角为103.3°,拉伸强度由8.16 MPa增至21.77 MPa.通过TG表明,分子结构中多元醇的引入,胶膜的耐热性有明显提高.     

双交联网络有机硅弹性体的制备及其自修复性能研究

首先通过水解缩合法制备出了不同巯基含量的无色透明巯基硅油(PDMS-SH),然后通过PDMS-SH与端乙烯基硅油的光诱导点击反应和羧基硅油与氨基硅油的热可逆动态离子交联构建出可逆/不可逆杂化双交联网络,制备出一种可快速UV固化及优异自修复性的有机硅透明弹性体.辐照强度为70 mW/cm~2,Darocur1173加入量为1.0 wt%,―SH/―Vi摩尔比为1.5/1时,巯基-烯点击聚合具有较高的凝胶率、转化率及聚合速率,且固化速率不受离子交联网络的影响.巯基-烯初网络形成后,进一步加热可促进离子网络的形成,提高弹性体力学性能.此外,动态离子交联网络在弹性体中均匀分布.增加离子交联网络可有效降低松弛活化能,有利于应力松弛及动态可逆性,同时热处理工艺有利于动态离子网络的移动及解离-重组过程,从而有利于双网络结构的形成及修复效率的提升.更重要的是,选用巯基硅油DE/15及离子交联网络含量仅15 wt%时,弹性体具有较优力学性能及自修复效率,多次修复后的修复效率仍可高达90%以上,同时快速固化的弹性体具有高达90%以上的可见光透光率.为基于可逆动态离子缔合诱导的快速固化自修复透明有机硅材料提供一种新型可行的制备方法.     

基于动态亚胺键的热固性聚酰亚胺的构建及自修复特性研究

以4,4-六氟异丙基邻苯二甲酸酐与4,4′-二氨基二苯醚为反应原料,合成了一种分子结构中包含双酰亚胺基元的二胺单体,将其与对苯二甲醛及三(2-氨基乙基)胺通过胺-醛缩合反应制备了一种分子主链包含动态亚胺键(—CH=N—)的热固性聚酰亚胺薄膜。该薄膜具有突出的耐热性及高的力学强度,其玻璃化转变温度及热分解温度分别高达224℃和385℃,拉伸强度大于90MPa,拉伸模量为2.16GPa,是目前报道的动态共价高分子的最高值。采用动态机械分析仪研究了该薄膜在不同温度下的应力松弛行为,并由此计算得到亚胺键在该聚酰亚胺骨架中发生可逆键交换反应的活化能为222.7kJ/mol。本文利用了伯胺对亚胺可逆键交换反应的"促进机制",实现了热固性聚酰亚胺薄膜在温和条件下的自修复。该设计思路可望拓展到其它动态共价高分子体系,有望为动态共价高分子的高性能化提供新的研究方向。     

苯乙烯-丙烯酸酯微乳液的合成研究

目前国内外许多专家学者积极研发低污染、低能耗、高性能的胶粘剂,以代替传统的毒性大、成本高、稳定性差的溶剂型胶粘剂[1]。苯乙烯-丙烯酸酯微乳液(苯-丙微乳液)是重要的胶粘剂之一。与常规乳液胶粘剂相比,它具有以下几个特点[2]:(1)是热力学稳定体系,可以自发形成;(2)分子粒     

可用于尾矿库区污染控制的生态修复剂的制备及性能研究

采用种子乳液聚合法,以水性聚氨酯为分散液,醋酸乙烯酯(VAc)、马来酸二丁酯(DBM)、丙烯酸(AA)为主单体,2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为功能单体,成功制备了羧基型共聚乳液,进一步考察了AMPS用量对乳液基本性能的影响,并首次将其用于尾矿库区的生态修复。实验结果表明:当AMPS用量在3%时,该共聚乳液用于尾矿库区固定尾砂的效果最好,且该共聚乳液形成胶膜的拉伸强度与固定尾砂时抗压强度呈现正相关性。另外,通过共聚乳液对尾砂的抗热老化、抗冻耐温、保水性及固定重金属离子稳定性等研究发现,羧基型共聚乳液能够有效实现尾矿库区的污染控制。微生物实验说明,羧基型共聚乳液作为尾矿库区修复剂使用时,具有良好的生态效应。这表明所制备的羧基型共聚乳液能够用于尾矿库区的污染控制与生态修复。     

新型双链表面活性剂DDOBA的合成与高单分散性憎水纳米金的制备

自行设计合成了新颖的苄胺型双链表面活性剂3,4-双十二烷氧基苄胺(DDOBA). 利用DDOBA/正丁醇/正庚烷/甲酸/HAuCl₄·4H₂O自发形成的水/油(W/O)型微乳液作为微反应器, 通过微波辐射下的甲酸还原法成功制备了DDOBA保护的憎水性金纳米粒子, 并通过紫外-可见(UV-Vis)光谱、透射电镜(TEM)、高分辨透射电镜(HR-TEM)和X射线衍射(XRD)等方法进行了表征和分析. 结果显示, DDOBA既可参与形成稳定的W/O型(油包水型)微乳液, 又可作为金纳米粒子的良好保护剂. 在合适的微乳液体系组成范围内, 用本实验方法可以获得高单分散性的憎水性金纳米粒子, 并能在空气/水界面上自动形成大面积短程有序的纳米金二维自组装膜.     

氢键作用驱动原花青素构筑水基抗菌黏合剂北大核心CSCD

水下黏合剂在生物医学和工程应用领域的需求越来越大。然而,目前报道的大多数水下黏合剂的制备方法中通常需要复杂的化学偶联或修饰,以及昂贵的构筑基元。本文利用低成本的葡萄籽提取物原花青素(PA)和商业化的聚乙二醇寡聚物(PEG)为构筑基元,发展了一种简单且经济的水下黏合剂的构筑策略,实现了在氢键作用下诱导仿生黏合剂生成。此黏合剂既可以在水上又可以在水下黏附不同材质的基底,且可重复使用。此外,易于制备的PA/PEG黏合剂也具有良好的抗菌活性和生物相容性。由于PA/PEG黏合剂具有制备简单、广谱黏附性、可循环使用和抗菌性等优点,将在医疗器械和制药应用中得到广泛应用。     

Bioinspired Design Provides High‐Strength Benzoxazine Structural Adhesives

A synthetic strategy to incorporate catechol functional groups into benzoxazine thermoset monomers was developed, leading to a family of bioinspired small‐molecule resins and main‐chain polybenzoxazines derived from biologically available phenols. Lap‐shear adhesive testing revealed a polybenzoxazine derivative with greater than 5 times improved shear strength on aluminum substrates compared to a widely studied commercial benzoxazine resin. Derivative synthesis identified the catechol moiety as an important design feature in the adhesive performance and curing behavior of this bioinspired thermoset. Favorable mechanical properties comparable to commercial resin were maintained, and glass transition temperature and char yield under nitrogen were improved. Blending of monomers with bioinspired main‐chain polybenzoxazine derivatives provided formulations with enhanced shear adhesive strengths up to 16 MPa, while alloying with commercial core–shell particle‐toughened epoxy resins led to shear strengths exceeding 20 MPa. These results highlight the utility of bioinspired design and the use of biomolecules in the preparation of high‐performance thermoset resins and adhesives with potential utility in transportation and aerospace industries and applications in advanced composites synthesis.     

Synthesis and Characterization of a Novel High-Temperature Structural Adhesive Based on MDA-BAPP-BTDA Co-Polyimide

A series of polyimide(PI) adhesives were synthesized from 2,2'-Bis [4-(4-aminophenoxy)phenyl] propane(BAPP), 4,4'-Diaminodiphenylmethane (MDA) and 3,3',4,4'-Benzophenonetetracarboxylic acid dianhydride (BTDA) via a two-step process. PI adhesives with different BAPP content were characterized in regard to their structure, thermal stability, mechanical properties and adhesive performance. Results showed that these PIs had excellent thermal stability, whose glass transition temperature (Tg) were around 300°C. While, superior dynamic mechanical behavior was observed, and the maximum loss factor declined with the increase of BAPP content. Single-lap shear strength of over 15.58 MPa at room temperature was obtained, and it remained high even at the temperature of 350°C. Factors that could affect bonding strength of these PI adhesives such as molar ratio of the diamine monomers, surface roughness of adherends and curing processes were investigated.     

A reversible water-based electrostatic adhesive

Commercial adhesives typically fall into two categories: structural or pressure sensitive. Structural glues rely on covalent bonds formed during curing and provide high tensile strength whilst pressure-sensitive adhesives use physical bonding to provide weaker adhesion, but with considerable convenience for the user. Here, a new class of adhesive is presented that is also reversible, with a bond strength intermediate between those of pressure-sensitive and structural adhesives. Complementary water-based formulations incorporating oppositely charged polyelectrolytes form electrostatic bonds that may be reversed through immersion in a low or high pH aqueous environment. This electrostatic adhesive has the advantageous property that it exhibits good adhesion to low-energy surfaces such as polypropylene. Furthermore, it is produced by the emulsion copolymerization of commodity materials, styrene and butyl acrylate, which makes it inexpensive and opens the possibility of industrial production. Bio-based materials have been also integrated into the formulations to further increase sustainability. Moreover, unlike other water-based glues, adhesion does not significantly degrade in humid environments. Because such electrostatic adhesives do not require mechanical detachment, they are appropriate for the large-scale recycling of, e.g., bottle labels or food packaging. The adhesive is also suitable for dismantling components in areas as varied as automotive parts and electronics.     

A bonded–riveted technique of fabrication and machine maintenance using hot-melt adhesives

Results of mechanical tests of bonded–riveted joints using two types of adhesives represented by epoxy adhesive and hot-melt adhesives derived from ethylene vinyl acetate are given. Removal time of bonded–riveted joints is evaluated and elastic characteristics of the employed adhesive materials are measured. It is shown that the use of hot-melt adhesives is more processable, because it provides the removal of riveted connections in short period without mechanical damages.     

Reprocessible Triketoenamine-Based Vitrimers with Closed-Loop Recyclability

Development of thermosets that can be repeatedly recycled via both chemical route (closed-loop) and thermo-mechanical process is attractive and remains an imperative task. In this work, we reported a triketoenamine based dynamic covalent network derived from 2,4,6-triformylphloroglucinol and secondary amines. The resulting triketoenamine based network does not have intramolecular hydrogen bonds, thus reducing its π-electron delocalization, lowering the stability of the tautomer structure, and enabling its dynamic feature. By virtue of the highly reversible bond exchange, this novel dynamic covalent bond enables the easy construction of highly crosslinked and chemically reprocessable networks from commercially available monomers. The as-made polymer monoliths exhibit high mechanical properties (tensile strength of 79.4 MPa and Young's modulus of 571.4 MPa) and can undergo a monomer-network-monomer (yields up to 90 %) recycling mediated by an aqueous solution, with the new-generation polymer capable of restoring the material strength to its original state. In addition, owing to its dynamic nature, a catalyst-free and low-temperature reprogrammable covalent adaptable network (vitrimer) was achieved. The design concept reported herein can be applied to the development of other novel vitrimers with high repressibility and recyclability, and sheds light on future design of sustainable polymers with minimal environmental impact.     

Cold fast setting epoxy adhesive VK-93

A developed epoxy adhesive, which meets the requirements of the operational repair of aeronautical equipment, components, and aggregates, as well as repairs under field conditions, is presented. The adhesive combines rather high pot life (～40 min), which enables surfaces with large areas to be bonded, as well as high hardening velocity at normal temperature upon reaching the initial level of adhesive joints of no less than 7.0 MPa (after 5 h of hardening) and a maximal level of strength of no less than 17.5 MPa (after 24 h of hardening). These characteristics of the adhesive serve to substantially improve the technical and economic efficiency of bonding operations.     

Diffusive Adhesives for Water-Rich Materials: Strong and Tunable Adhesion Beyond the Interface

It is notoriously difficult to adhere water-rich materials, such as hydrogels and biological tissues. Existing adhesives usually suffer from weak and nonadjustable adhesion strength, in part because the contact between the adhesive and substrate is largely restrained to the adhesive/substrate interface. In this study, we have attempted to overcome this shortcoming by developing a class of diffusive adhesives (DAs) that can extend adhesion deep into the substrate to maximize the adhesive/substrate contact. The DAs consist of hydrogel matrices and preloaded water-soluble monomers and crosslinkers that can diffuse extensively into the water-rich substrates after adhesive/substrate contact. Polymerization and crosslinking of the monomers are then triggered leading to a bridging network that interpenetrates the DA and substrate skeletons and topologically binds them together. This kind of adhesion, in the absence of adhesive/substrate covalent bonding, is of high strength and toughness, comparable to those of the best-performing natural and artificial adhesives. More importantly, we can precisely tune the adhesion strength on demand by manipulating the diffusion profile. It is envisioned that the DA family could be extended to include a large pool of hydrogel matrices and monomers, and that they could be particularly useful in biological and medical applications.     

Effects of Alcell Lignin Methylolation and Lignin Adding Stage on Lignin-Based Phenolic Adhesives

To investigate the effects of lignin methylolation and lignin adding stage on the resulted lignin-based phenolic adhesives, Alcell lignin activated with NaOH (AL) or methylolation (ML) was integrated into the phenolic adhesives system by replacing phenol at various adhesive synthesis stages or directly co-polymerizing with phenolic adhesives. Lignin integration into phenolic adhesives greatly increased the viscosity of the resultant adhesives, regardless of lignin methylolation or adding stage. ML introduction at the second stage of adhesive synthesis led to much bigger viscosity than ML or AL introduction into phenolic adhesives at any other stages. Lignin methylolation and lignin adding stage did not affect the thermal stability of lignin based phenolic adhesives, even though lignin-based adhesives were less thermally stable than NPF. Typical three-stage degradation characteristics were also observed on all the lignin-based phenolic adhesives. Three-ply plywoods can be successfully laminated with lignin based adhesives, and it was interesting that after 3 h of cooking in boiling water, the plywoods specimens bonded with lignin-based phenolic adhesives displayed higher bonding strength than the corresponding dry strength obtained after direct conditioning at 20 °C and 65% RH. Compared with NPF, lignin introduction significantly reduced the bonding strength of lignin based phenolic adhesives when applied for plywood lamination. However, no significant variation of bonding strength was detected among the lignin based phenolic adhesives, regardless of lignin methylolation or adding stages.     

Hot-melt adhesives

The manufacturing and physical properties of hot-melt adhesives are briefly reviewed. The effect of surface roughness on the adhesive properties of hot-melt seals have been studied based on the example of the technique for repairing automotive batteries.