Modeling the failure of an adhesive layer in a peel test

The failure of an adhesive layer in a 180° peel test is analyzed by the modeling of the peel as an elastica. The adhesive is assumed to fail by a process of cavitation and fibrillation. The resistance of the fibrillated material to deformation gives rise to a rate‐dependent peel force F. Governing equations, which take into account the large deformation of the fibrillated materials, are derived. Numerical solutions are obtained for the special case of a linear, viscous adhesive. Assuming a critical strain failure criterion for the fibrils, we show that the peel rate is inversely proportional to the square root of the adhesive thickness and directly proportional to F^3/4. The connection between the peel test and the tack test is also discussed. The maximum traction on the peel arm is found to be directly proportional to the peel force and inversely proportional to the adhesive thickness. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2277–2291, 2002     

Molecular modeling of interfaces between cellulose crystals and surrounding molecules: Effects of caprolactone surface grafting

A technical problem in cellulosic nanocomposite materials is the weak interaction between hydrophilic cellulose and hydrophobic polymer matrices. One approach to solve this difficulty is to chemically graft monomers of the matrix polymer onto the cellulose surface. An important question is to understand the effect such surface modification has on the interfacial properties. Semi-empirical approaches to estimate work of adhesion based on surface energies do not provide information on specific molecular interactions. Details about these interactions were obtained using molecular dynamics (MD) simulation. Cellulose interfaces with water and caprolactone medium were modeled with different amounts of grafted caprolactone. The modification lead to an increased work of adhesion between the surface and its surrounding medium. Furthermore, the MD simulations showed that the interaction between cellulose, both modified and non-modified, and surrounding medium is dominated by Coulomb interactions, predominantly as hydrogen bonds.     

凝胶改性基底微藻细胞黏附特性及热力学分析

为强化微藻生物膜成膜过程中藻细胞与基底黏附,同时解决藻细胞残留造成的基底重复利用性差的问题,用聚N-异丙基丙烯酰胺(PNIPAAm)温缩型凝胶修饰基底。傅里叶红外光谱分析改性表面化学特性;结合微藻培养温度给出适宜藻细胞黏附的基底浸润特性;通过构建热力学模型,明晰温度对藻细胞与温缩型凝胶改性基底界面作用自由能的影响规律,结果表明,随温度从15℃升高到30℃,藻细胞与改性基底的界面作用自由能变从-39 mJ·m-2变化到-67 mJ·m-2,即黏附能力随温度升高而增强。黏附实验表明,随温度从15℃升高到30℃,温缩型凝胶改性基底的藻细胞黏附密度提高了50%,这与热力学模型预测结果吻合,说明该模型对分析温缩型凝胶改性基底藻细胞黏附有重要指导意义。     

Improvement of interfacial adhesion in PP/PS blends enhanced with supersonic atmosphere plasma spraying surface‐treated carbon fiber

The effects of surface treatment of a carbon fiber (CF) by supersonic atmosphere plasma spraying (SAPS) on the interfacial adhesion behavior and morphology of polypropylene/polystyrene (PP/PS) matrix blends filled CF composites were investigated. Effects of surface treated a commercial CF on mechanical properties are studied. Contact angle was measured to examine the changes in wettability of the CF. The chemical and morphological changes were characterized by using X‐ray photoelectron spectroscopy and scanning electron microscopy. PP/PS/CF composites were fabricated with and without SAPS treatment, and their interlaminar fracture toughnesses were compared. The results showed that the interlaminar shear strength of composites has been greatly improved filled SAPS modification CF. The water contact angle of resin sample decreased 50% after addition of SAPS surface‐treated CF. Scanning electron microscopy results on the fractured surface exhibited PP/PS blends adhered well around the CFs of the SAPS‐treated specimen compared with that of the untreated specimen. This attributed to the CF interlock, and it improves the wetting between fibers and resins. Copyright © 2017 John Wiley & Sons, Ltd.     

超疏水低粘着铜表面制备及其防覆冰性能

用喷砂处理在铜片表面形成微米级丘陵状凹坑,再用表面氧化处理在铜片表面制备菊花花瓣状CuO纳米片.通过喷砂-表面氧化处理在铜片表面成功构建了微米-纳米复合结构,这种表面氟化后与水滴的接触角高达161°,滚动角低至1°,显示出优异的超疏水性和很低的粘着性.低温下,这种表面与水滴间的热量交换较小,水滴不易凝结,有效地提高了抗结霜性.抗结霜性良好的超疏水铜有望在热交换器或低温运行设备等领域获得应用,这种简便的超疏水铜表面的制备方法也给其它工程材料超疏水表面的工业化制备提供了一个思路.     

第一原理分子动力学研究类金刚石薄膜的结合强度与摩擦性能

金刚石(110)表面具有不同方向上抛光速率的强烈不对称的特征,用第一性原理全能量平面波赝势方法模拟研究了类金刚石薄膜表面的结合强度与摩擦性能,确定了相互作用模型以及排斥力作用范围,研究了范德华排斥力在摩擦表面上的分布,研究结果表明,摩擦表层感受到的力在〈001〉和〈110〉2个方向上表现明显不同,而且〈110〉方向上摩擦力一直高于〈001〉方向上的摩擦力.     

Surface adhesion properties of graphene and graphene oxide studied by colloid-probe atomic force microscopy

Surface adhesion properties are important to various applications of graphene-based materials. Atomic force microscopy is powerful to study the adhesion properties of samples by measuring the forces on the colloidal sphere tip as it approaches and retracts from the surface. In this paper we have measured the adhesion force between the colloid probe and the surface of graphene (graphene oxide) nanosheet. The results revealed that the adhesion force on graphene and graphene oxide surface were 66.3 and 170.6 nN, respectively. It was found the adhesion force was mainly determined by the water meniscus, which was related to the surface contact angle of samples.     

Theoretical analysis on capillary adhesion of microsized plates with a substrate

The stiction of a thin plate induced by the capillary force has attracted much attention in the broad range of applications. A novel method is presented to calculate the capillary adhesion problem of the plate through analytical method. The expressions of the surface energy, the strain energy and the total potential energy of the plate-substrate system have been analyzed and delineated. By means of continuum mechanics and the principle of minimum potential energy, the governing equation of the plate with an arbitrary shape and the corresponding transversality boundary condition due to the moving bound have been derived. Then the critical adhesion radius of the circular plate has been solved according to the supplementary transversality condition. Thus the deflections of the plates are analytically calculated with different critical adhesion radii. The results may be beneficial to the engineering application and the micro/nanomeasurement.     

Synthesis and Characterization of New Adhesion Promoter for Grafting Conducting Polymer on Oxide Substrate

For grafting polypyrrole layers on oxidic substrates, the synthesis and characterization of a new adhesion promoter 11‐(pyrrol‐3‐yl) undecyl trimethoxysilane (PyTMS) were described in this article. The oxidation potential of PyTMS was determined by cyclic voltammetry. The grafting behavior of such an adhesion promoter on oxidized surface and chemical deposition of polypyrrole over the modified oxidized surface were studied. The adsorbed layer on the oxidized substrates thus formed was determined by both contact angle measurements and X‐ray photoelectron spectroscopy. Chemical polymerization of terminal pyrrole moieties on such substrates yielded adhesive polypyrrole films, and SEM image showed that the morphology of the polypyrrole films was influenced by the experimental conditions.     

EFFECT OF HEAD SHAPE ON THE ADHESION CAPABILITY OF MUSHROOM-LIKE BIOLOGICAL ADHESIVE STRUCTURES

Theoretical studies have been extensively performed to reveal the mechanism of the biological adhesive structure with a flat head.However,most biological adhesive structures have a big head.Here we investigate the effect of the head shape on the adhesion capability of a mushroomlike adhesion structure based on a finite element model.We show that a mushroom-like head produces significant adhesion enhancement.We investigate also the effect of the elastic modulus of the adhesive structure on the adhesion.Our results are consistent with existing experimental results.