Monocomponent Waterborne Polyurethane Adhesives: Influence of the Crosslinking Agent on Their Properties

To improve the properties of the monocomponent waterborne polyurethane (WPU) adhesives, a series of crosslinked WPU were prepared with trifunctional polyester polyol (P210) as crosslinking agent. The crosslinked WPU dispersions and their films were characterized by conventional methods. The adhesion property of the samples was measured from T-peel test of leather/WPU adhesive/leather joints. Compared with the linear one, the crosslinked WPU exhibited low viscosity, small particle size, and low surface tension. For crosslinked films, the thermal stability, water resistance and mechanical properties were remarkably enhanced. The experimental data of T-peel test indicated that the adhesive strength significantly increased to 4.8 KN/m by crosslinking up to the optimum crosslink index of 1.2 and then showed a small decrease with excess.     

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.     

Observation of adhesive force and energy of adsorbents on rubber substrates by atomic force microscopy

We observed the surface morphology and adhesive interaction of adsorbents on rubber substrates by atomic force microscopy (AFM). The detachment of adsorbents from rubber substrates is an important issue for various machines like home appliances and laundry machine. Since a clean surface of the functioning parts is required, a frequent cleaning process must be developed. In particular, dust and lint have a tendency to bind to the rubber surface of a laundry machine. Several practical methods have been attempted to remove these particles from the surface. Pure water, detergent, sodium hypochlorite (65 °C), and cold water (18 °C) are treated onto artificial dust and lint mixtures on rubber with water fluid by rapid rpm. The dust‐and‐lint adsorbents are investigated by AFM after the treatment, and topographic images and force–distance (F–D) curves were generated for the samples. The roughness, measured as the root mean square, is a key factor to judge the cleaning quality. From the F–D curves, we are able to obtain adhesive energy in addition to adhesive force which will yield qualitative measures of the interactions between the remaining adsorbents and the rubber surface. Considering the values that were measured, hot water with water fluid by rapid rpm offers the best performance when cleaning the surface. The chemical like sodium hypochlorite is good for thinning the materials, but it solidifies them, which is eventually detrimental to proper functioning. Copyright © 2014 John Wiley & Sons, Ltd.     

Preparation of novel,liquid, solvent‐free,polyolefin‐based adhesives

An innovative procedure for functionalization of polyolefins was developed. It was found that synthesized polyolefins end‐capped with trimethoxysilane (silylated polyolefins) are new polyolefin‐based adhesives. To prepare the mentioned materials,1‐octene as a higher α‐olefin was cooligomerized with two linear, nonconjugated dienes (ie, 1,5‐hexadiene and 1,7‐octadiene) by using metallocene catalyst system, Cp₂HfCl₂/MAO, at room temperature. Then, amine‐terminated trimethoxysilane (3‐aminopropyltrimethoxysilane) was reacted with unsaturated bonds of synthesized cooligomers in the presence of palladium(II) acetate. Embedding of the dienes on 1‐octene oligomeric chains was explored by Fourier transform infrared (FTIR), ¹H, and ¹³C‐NMR spectroscopy. On the basis of the results, 1,5‐hexadiene showed both 1‐butene branch and five‐member ring. On the other hand, 1,7‐octadiene was incorporated by 1,2‐addition, forming both 1‐hexene branch and seven‐member ring in the cooligomer backbone. Mole percentage of C?C and cyclic moieties reached to a value of 28.54, 18.59% mol in 1‐octene/1,5‐hexadiene, and 38.04, 6.71% mol in 1‐octene/1,7‐octadiene cooligomers, respectively. Reaction of synthesized cooligomers with 3‐aminopropyltrimethoxysilane was confirmed by FTIR spectroscopy, which yielded targeted adhesives. To study the adhesion properties, resulting adhesives were applied to different substrates. Obtained results demonstrated that tensile shear strength of synthesized adhesives to polar substrates was 2.21% to 2.84% more than nonpolar substrates. Among studied systems, the best performance was achieved by1‐octene/1,7‐octadiene–based adhesive and Al substrate with tensile shear strength of 1.45 N/mm².     

The analysis of adhesive bonds using electromagnetic acoustic transducers

The paper presented here outlines a technique for examining aerospace adhesive bonds using electromagnetic acoustic transducers (EMAT). The main restriction on the use of bonded structures is the lack of a reliable, applicable non-destructive test. Simple acoustic theory shows that a shear wave at normal incidence to an interface should be a more sensitive probe of interfacing coupling than a longitudinal wave. Conventional piezoelectric shear transducers require a very viscous couplant which makes scanning problematic. The EMAT described here consists of a pancake coil, and a permanent magnet behind the coil provides a static magnetic field normal to the surface of the sample and the plane of the coil. The EMATs used have the advantage of generating broadband radially polarized shear waves, while requiring no acoustic couplant. They are also comparable in size to typical piezoelectric transducers. The broadband nature of the transducer gives it a high spatial resolution in the direction of wave propagation. Experiments performed on plate-like samples have successfully detected deliberately constructed defects, while monitoring the adhesive thickness. Defects have been identified using a C-scan technique using a single EMAT in send-receive mode from either side of the bond.     

生物胶对动物支气管的粘合作用

目的：通过3种生物胶对动物支气管的粘合作用的比较，以了解不同生物胶对支气管的粘合作用。方法：通过观察生物胶对离体动物肺组织的粘合作用。气囊导管注入生物胶对活体兔支气管的封堵作用及对导管的影响，以了解不同生物胶的特性，结果：WAB生物胶作用差，纤维蛋白封闭剂5min时粘合力为50pbsi,而且不会对导管有明显的粘合作用。而血管栓塞剂（NBCA）5min后粘合作用为70pbsi，但导管易与肺及支气管粘合。结论：纤维蛋白封闭剂适合于支气管内介入治疗。     

胶粘剂对石英音叉剪切力控距的影响

粘接音叉和光纤探针的胶粘剂对由石英音叉和光纤探针构成剪切力控距体系的品质因数有明显的影响。通过对比不同胶粘剂的物理特性 ,选择了适合于粘接音叉和光纤探针的胶粘剂。研究发现 ,室温快速固化环氧树脂胶粘剂HY 91 4 ,GHJ光学用环氧型胶粘剂 (Opticalepoxy)和 50 2胶能满足实验要求。理论分析指出 ,对于同样的音叉和光纤探针来说 ,胶粘剂的密度和用量是影响音叉 探针体系品质因数的主要因素     

Flexible,adhesive, strain-sensitive,and skin-matchable hydrogel strain sensors for human motion and handwritten signal monitoring

Flexible hydrogel strain sensors have made great progress in medical applications, human motion detection, and human-machine interactions. However, the design of hydrogels to realize the synergistic responses of excellent mechanical properties, robust adhesion, and stable sensing is still a highly challenging task. Herein, we report a multifunctional hydrogel (PAMT hydrogel) by crosslinking acrylic acid (AA), 2-methacryloyloxyethyl phosphorylcholine (MPC) and tannic acid (TA) to form a polymer network via a simple one-pot free radical polymerization. Among them, the dynamic bonding with hydrogen bonding between PAA chains and TA significantly improved the stretch ability of the hydrogels (700%), and the abundant catechol groups on TA endowed the hydrogels with strong and stable adhesion properties (the adhesion strength to glass reached 248 N m⁻¹). When applied to human skin, the hydrogel can be easily peeled off without leaving any residue. Furthermore, the strain sensor assembled using PAMT hydrogel could not only effectively detect the movement in different parts of the human body, but also be used for precise handwritten recognition and electric skin of silicone prosthetic hand. Due to the addition of MPC and TA, the conductive hydrogel has good biocompatibility and no harm to human body. Therefore, PAMT hydrogel has opened up a new vision for the development of intelligent detection and bionic intelligent robots.     

多次溶剂萃取-气相色谱/串联质谱法测定热熔胶中的多环芳烃

建立了热熔胶中16种多环芳烃( PAHs)的多次溶剂萃取-气相色谱/串联质谱测定方法。详细研究了样品的萃取条件、净化条件和气相色谱/串联质谱测定条件,并与气相色谱-质谱法进行了对比。样品以10 mL正己烷为萃取溶剂,于60℃超声萃取20 min,萃取液依次经冷冻后离心、二甲基亚砜萃取2次、正己烷反萃取2次进行净化,得到的净化液以气相色谱/串联质谱法多反应监测( MRM)模式进行检测。本方法的线性相关系数( R2)均大于0.9969,检出限为1.0~10μg/kg,精密度小于6.3%,16种PAHs的加标回收率为80.4%~117.6%。考察了串联质谱检测的基质效应,发现基质效应不明显。本方法检出限优于气相色谱-质谱法(23~94μg/kg),并能增加定性和定量分析的准确性。本方法灵敏、准确可靠,满足热熔胶中PAHs测试要求。     

Bio-based removable pressure-sensitive adhesives derived from carboxyl-terminated polyricinoleate and epoxidized soybean oil

A novel kind of fully bio-based PSAs we re obtained through the curing reaction between two components derived from the plant oils:carboxyl-terminated polyricinoleate(PRA) fro m the castor oil and epoxidized soybean oil(ESO).The get content,glass transition temperature(Tg),rheological behavior,tensile strength,creep resistance and 180° peel strength of the PSAs were feasibly tailored by adjusting the component ratio of ESO to PRA.At low cross-linking level,the PSAs behaved like a viscous liquid and did not possess enough cohesiveness to sustain the mechanical stress during peeling,The PSAs cross-linked at or near the optimal stoichiometric conditions displayed an adhesive(interfacial) failure between the substrate and the adhesive layer,which were associated with the lowest adhesion levels.The PSAs with the dosage amount of ESO ranging from 10.20 wt% were tacky and flexible,which exhibited 1800 peel strength ranging from 0.4～2.3 N/cm;and could be easily removed without any residues on the adherend.The process for the preparation of the fully bio-based PSAs was environmentally friendly without using any orga nic solve nt or other toxic chemical,herein showing the great potential as sustainable materials.