Adhesion and adhesion degradation of a pressure sensitive tape on carbon steel

Corrosion protection of carbon steels by organic coatings is dependent on a good adhesion between coating and substrate. In this work the blister test method was used to study the adhesion of a pressure sensitive tape applied on carbon steel. Deionized water was used to pressurize a blister formed by the tape covering a through-hole in the steel substrate. Values of adhesion strength as measured by the strain energy release rate were determined for two different blister pressurization rates or water injection rates. The adhesion strength was higher for the larger injection rate, which is expected for pressure sensitive tape. These values were probably overestimates of the true adhesion strength owing to plastic yielding of the membrane. Resistance to adhesion degradation near coating defects or macroscopic scribes was characterized using a height regulating scanning Kelvin probe on samples exposed to sodium chloride solution or a salt spray environment. Although the tape exhibited good barrier properties to water and ions, cathodic delamination was observed near the scribe after salt spray exposure. Wet/dry cycles were more aggressive than continuous salt spray exposure, since during continuous exposure corrosion products are washed away. It was observed that the oxide layer grows to a larger extent during wet/dry cycles; therefore, acceleration of the delamination process is probably associated with a “wedge effect” of the oxide on the interface.     

High modulus semi-crystalline polymers by solid state rolling

Solid state rolling of semi-crystalline polymers is shown to be an effective method of producing high strength, high modulus tape at acceptable production rates. High density polyethylene tape was produced having a tensile strength exceeding 300 MPa and a tensile modulus of 8.7 GPa at production rates exceeding 8 m/min. A significant factor in producing highly oriented tape by the rolling process is roll temperature. Increasing the roll temperature from 25°C to 125°C not only increases the maximum extent of orientation achievable, but increases the mechanical properties at a given degree of thickness reduction. Internal frictional heat development limited the maximum thickness reduction ratio of polypropylene to 6.6:1. This reduction was reached by rolling at 150°C. The resultant tape had a tensile modulus of 5.1 GPa and a tensile strength of 300 MPa.     

Dynamic mechanical analysis of barium ferrite magnetic tapes with aramid and poly(ethylene naphthalate) substrates

Frequency‐ and temperature‐dependent viscoelastic characteristics of advanced materials used for high‐capacity digital magnetic tapes were analyzed using a custom ultra‐low frequency dynamic mechanical analyzer (ULDMA). The magnetic tapes studied both use barium ferrite (BaFe) magnetic particles. One tape uses an aromatic poly(amide) or aramid substrate, and the other tape uses a poly(ethylene naphthalate) or PEN substrate. ULDMA studies were performed for both types of tape materials using samples cut from reels and the substrates after the front and back coats were removed. Two‐hour experiments were performed at 25, 30, 50, and 70°C temperatures, and four test frequencies were used at each temperature: 0.006, 0.010, 0.033, and 0.065 Hz. Properties determined were the peak strain‐based elastic modulus, E, and the storage modulus, E′, loss modulus, E″, loss tangent, tan(δ), complex modulus, E*, and complex loss, E″/E*, expressed as a percentage. When compared with the PEN tape and substrate materials, the peak elastic modulus, storage modulus, and complex modulus were higher for the aramid materials. Substrates for each material exhibited higher elastic, storage, and complex moduli compared with their respective tapes. Through the complex loss percentage, comparisons were made between the aramid and PEN materials related to their viscoelastic characteristics. Finally, the influence of frequency was shown to have increasing relevance at higher temperatures, with the PEN tape and substrate exhibiting an increase in complex loss modulus in the 50°C range because of the β* secondary transition. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41478.     

Vacuum-based picking-up of thin chip from adhesive tape

The reliable picking-up of thin chip using the vacuum sorption determines the success rate of flip chip assemblies from donor tape to receptor substrate. An analytical solution to model the chip–adhesive–tape structure with vacuum loads is introduced to understand the fracture mechanism of chip picking-up. The critical process parameters (the length of bonded region, vacuum strength, and pick-up displacement, etc.) are investigated. Theoretical predictions are used in combination with virtual crack-closure-based finite-element technique to reveal the detaching behavior between the chip and the adhesive tape. The results show that the length of the bonded region should be controlled less than 40% of chip length to eliminate the effects of chip thickness, and the higher vacuum strength acting on the adhesive tape is able to accelerate the detachment of the chip from the adhesive tape. In particular, a process window is proposed to enhance the reliability and efficiency of picking-up for a thin chip.     

Functionalized polymeric membrane with aquaporin using click chemistry for water purification application

A new type of aquaporin‐based biomimetic water purification membrane is fabricated using a propargyl functionalized β‐sheet peptide (FBP1). FBP1 is demonstrated to bind to aquaporin and form a stable protein–peptide complex in aqueous solution, as well as covalently conjugate with azide group. Substrate starting material, polysulfone (PSU), is modified with ～1.05 azide group per repeating unit and casted into a thin film substrate with appropriate pore size structure using non‐solvent induced phase separation technique. Protein–peptide complex then is clicked onto the substrate using an in‐house built circulating system. The successful immobilization is verified by surface chemical composition analysis and surface morphology analysis. The preliminary salt rejection results show salt rejection improvement from 5% of control membrane to 12.5%. We thus demonstrate a promising method to conjugate a thin layer of membrane protein onto polymeric substrate and well maintain the functionality of membrane proteins. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46678.     

Electromagnetic shielding property of laminated carbon fiber tape reinforced thermoplastics

ABSTRACT

Carbon fiber reinforced thermoplastic (CFRTP) has a good electromagnetic shielding property due to its higher conductivity and broad absorption frequency bandwidth while presenting high specific strength and stiffness, their easy process-ability, cost-effectiveness, and recyclability. In the present study, laminated CFRTP made of carbon fiber-polyamide 6 unidirectional tape (UD tape) were fabricated with different laminate configurations and arrangements (unidirectional, bidirectional, and quasi–isotropic) and then were compared with randomly chopped-tape CFRTP. Thereafter, estimated electromagnetic interference shielding effectiveness (EMI-SE) using Simon formalism and flexural properties of CFRTP were evaluated. The result showed a remarkable total EMI-SE of 31–44 dB in the Ultra High Frequency (UHF) range and strongly correlated with the laminate configuration of CFRTP. Whereas, randomly chopped-tape CFRTP has a lower total EMI-SE of 23–27 dB in the same frequency range. In addition, the flexural test result showed the flexural strength and modulus are strongly influenced by the tape layer configuration in the laminated CFRTP. Moreover, microscopy analysis was also conducted to verify the interlaminar structure and fiber-to-fiber contact in the composite. In conclusion, laminated CFRTP made of UD tape can be considered as electromagnetic interference shielding material for both functional and structural applications.     

氮化硅流延膜的制备

流延成型是一种制备高质量陶瓷基片的成型方法.氮化硅是一种高热导率的材料,有望在电子基片领域获得应用.本文利用流延成型制备了具有较好柔韧性和一定强度的氮化硅流延素坯膜.研究了无水乙醇、无水乙醇/丁酮作为溶剂时对浆料粘度的影响.通过优化流延浆料添加剂的各种配比,得出了适合氮化硅粉体(SN-E10)流延的最佳配方.     

Investigation of the glass transition temperature and damping of an acrylic/epoxy bonding tape using the peak damping method

The dynamic properties of a structural tape used for adhesive bonding applications have been measured at different temperatures to determine its glass transition temperature and damping properties. For this purpose, free layer beams consisting of a base layer steel and the tape layer were vibrated using a resonant beam technique with free-free end conditions. To measure the dynamic values (elastic modulus and loss factor) of the tape, the necessary equations were derived and the frequency dependence of the beams was investigated from –55°C to +60°C. Three beams with different layers were tested. Results have shown that as the temperature increases, the elastic modulus of the tape decreases, while the loss factor of the tape increases up to 20°C and then decreases to a constant level. The results from the three beams are in agreement, showing that the glass transition temperature of the tape is about 20°C, which implies viscoelastic properties at room temperature.     

Correlating the adhesion of an acrylic coating to the physico-mechanical behavior of a polypropylene substrate

In this study, the adhesion strength of an acrylic coating onto a polypropylene (PP) based substrate was studied. The adhesion strength of the PP containing various wt% of oxidized wax was found to be dependent on the surface free energy of the substrate. To this end, the geometric mean and the acid-base approaches were used to estimate the surface free energy, both of which shown to exist a direct relation between surface hydrophilicity and the content of the oxidized wax. The viscoelastic behavior of the adherend also contributed to the coating adhesion. The viscoelastic response of the blends was investigated using dynamic mechanical thermal analysis (DMTA) and universal testing machine (UTM) for the bulk properties of the substrate and a depth sensing indentation technique for its near-surface, respectively. Bulk and near-surface moduli were decreased as a result of incorporation of wax additive into PP matrix. These were attributed to the homogeneous distribution of low molecular weight wax chains in the polymeric matrix and hence their impact on substrate integrity. The DMTA analysis showed a single phase matrix for all blends. Using a linear trend line, the adhesion test results revealed a good correlation to surface free energy calculations compared with the substrate modulus. The weaker effect of substrate modulus on surface adhesion was ascribed to the substrate plasticity and/or development of internal stresses in the coating layer. However, the glass transition temperature of the coating suggested that the internal stresses in coating layer were responsible to relax prior to conducting adhesion measurement.     

Comparative behavior of PVA/PAN and PVA/PES composite pervaporation membranes in the pervaporative dehydration of caprolactam

Flat‐sheet composite membranes were developed by the traditional phase inversion technique using poly;(vinyl alcohol) (PVA). PVA composite pervaporation (PV) membranes were prepared with crosslinked PVA selective layer and porous polyacrylonitrile (PAN) and polyether sulfone (PES) substrate layer material as supports for separating heat sensitivity substance ε‐caprolactam (CPL) from CPL/water mixtures. Glutaraldehyde was used as crosslinking agent. The effect of the composition of glutaraldehyde on membrane stability and structure were investigated. The operating parameters, such as feed concentration and operating temperature, remarkably affected PV performance of the composite membranes. The composite membranes with PVA casted on PAN (PVA/PAN) showed superior PV performance than that casted on PES (PVA/PES). This study has also shown that the type of porous support plays an important role in the PV performance. As a result, this work has presented the information needed of the behavior of PV membranes for dehydration applications of industrial caprolactam. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4005–4011, 2007     

Evaluation of pressure-sensitive tape adhesion and backing directionality by excimer laser methods

The effects of 248 nm KrF excimer laser irradiation on a pressure-sensitive adhesive tape bonded to a glass substrate were investigated as a possible method to evaluate the quality of adhesion, as well as the directionality induced during manufacture. The model pressure-sensitive tape consisted of biaxially-oriented polypropylene (PP) tape coated with a hot-melt rubber resin. Analysis of the front-shot experiments, which were performed by irradiation through the PP backing, allowed correlation between the excimer laser irradiation-induced detachment and the peel adhesion strength. For this purpose, peel tests were performed before and after laser shots. The directionality induced during manufacture resulted in a more ablated area in the strength direction than in the transverse direction when the bonded tapes were irradiated with an elliptically-shaped laser beam above the ablation threshold. A correlation was found between the detachment bubbles created by irradiation below the ablation threshold and their respective peel adhesion values, which allows us to evaluate the quality of adhesion for pressure-sensitive tapes. Thus, a method to evaluate the quality of adhesion using an excimer laser is proposed based on the findings of this work.     

Techniques and considerations for nanoindentation measurements of polymer thin film constitutive properties

Modulus and yield strength determinations from nanoindentation experiments of thin poly(methyl methacrylate) (PMMA) polymer films have been investigated. The modulus was calculated from flat punch theory and showed a large effect of the substrate, hydrostatic pressure, and surface topography. Substrate corrections were possible in some cases but often resulted in erroneous or negative values due to large penetration depths with respect to the film thickness and differences in the stiffness of the coating and substrate. Hydrostatic pressures up to 600 MPa were exerted by a conical and cube corner indenter tip and influenced the modulus and yield strength measurements. Due to the non-linear deformation behavior of the PMMA films, however, hydrostatic pressure corrections tended to underestimate the modulus. The yield strength was measured based on Tabor's approximation using the unloading curve and was compared with measurements using plastic zone predictions and compression test data. Yield strength calculations from plastic zone images were lower in every case than those calculated from compliance, showing the viscoelastic nature of the material.     

Formation of functional polyethersulfone electrospun membrane for water purification by mixed solvent and oxidation processes

Most water-based filtration applications of electrospun nanofibrous membranes require the substrate to possess suitable strength, wettability and permeability, where the size, inter-fiber adhesion and hydrophilicity of electrospun nanofiber must be carefully controlled in order to meet these criteria. In this study, we demonstrate the fabrication of high quality polyethersulfone (PES) nanofibrous membranes that are particularly useful for water purification. Two treatments were illustrated that can significantly improve the mechanical property and hydrophilicity of the PES membrane without compromising its porosity and water permeance. The first treatment involves the use of mixed solvents (DMF/NMP), containing a high vapor pressure component (NMP), where the mechanical properties (e.g. modulus and strength) of the membrane are improved by solvent-induced fusion of inter-fiber junction points. The second method involves the short time oxidation treatment with a strong oxidant (ammonium persulfate), where the hydrophilicity of the membrane is greatly increased.     

Tensile stress–strain behaviour of a structural bonding tape

The tensile properties of a pressure-sensitive adhesive tape which can be cured to impart structural performance have been measured at different temperatures using quasi-static tests. In order to assess the linear viscoelastic behaviour of the tape, results from the vibrating beam technique are also presented. Bulk specimens and non-contacting extensometers were found to be suitable for tensile measurements on such a flexible adhesive. The results show that the strength of the tape is not as high as, and that its behaviour is very different from, traditional structural adhesives, but its high strain-to-failure with an adequate strength offers exciting possibilities for structural joints.     

Effect of clay orientation on the tensile modulus of polypropylene-nanoclay composites

We present an experimental investigation of the effect of clay orientation, as produced by melt extrusion, on the tensile modulus of compatibilized and uncompatibilized syndiotactic polypropylene nanoclay composites. The orientation of the clay tactoids in extruded tape samples was quantified using 2D X-ray diffraction data. It was found that in the case of the tapes made from compatibilized nanocomposites the orientation of the clay tactoids increased with extrusion shear rate, while in the case of tapes extruded from uncompatibilized hybrids the clay orientation was independent of the shear rate. Tensile modulus of the extruded tapes along the flow direction was measured and was found to correlate well with the average orientation of the clay tactoids. In the case of the compatibilized hybrids the modulus increased with the extrusion shear rate until a saturation value, whereas for the uncompatibilized hybrids the modulus was nearly independent of the shear rate. Semi-quantitative predictions of the effect of clay orientation on the tensile modulus of the compatibilized tape samples were obtained using a micromechanical model.     

The use of an interleaved film for optimising the properties of hot compacted polyethylene single polymer composites

It is shown that the incorporation of interleaved films has major advantages for the production of polyethylene single polymer composites by the process of selective melting (termed hot compaction). The key issue is to choose a compaction temperature which melts the minimum amount of the original oriented elements whilst achieving acceptable bonding within the compacted structure. Utilising an interleaved film, excellent interlayer peel strengths can be achieved at lower compaction temperatures giving greater retention of the oriented fraction of the original fibres or tapes and a wider processing window. For example, using a very high modulus, ultra-high molecular weight, polyethylene tape, together with an interleaved film, resulted in an in-plane modulus of 25 GPa, an in-plane strength of 500 MPa, and an interlayer strength of >10 N/10 mm. These are amongst the highest values reported for a single polymer composite. Other important factors have been investigated including fabric weave style and whether it is better to use fibres or tapes as the oriented reinforcement.     

Photoelastic Stress Analysis of Bonded Lap Shear Joints Having Thermoplastic Adherends

The effects of substrate stiffness and modulus on joint strength and stress distribution were investigated for a series of nylon substrates bonded with an epoxy adhesive. Substrate stiffness and modulus were controlled by the level of glass filler in the resin. Single lap shear samples having both identical (“self-bonded”) and dissimilar (“cross-bonded”) substrates were investigated. For the self-bonded samples, lap shear strength was found to increase with increasing substrate modulus and stiffness. The strengths of the cross-bonded samples were intermediate to the strengths of the corresponding self-bonded samples. Photoelastic techniques were used to observe stress patterns in the lap joints during testing. One type of stress pattern was observed for all self-bonded samples regardless of substrate stiffness. Two patterns, one for the stiff substrate and one for the more flexible substrate, were observed for cross-bonded samples. The photoelastic analysis agreed qualitatively with predictions of stress distributions based on linear elastic and linear elastic/perfectly plastic theoretical models.     

Mechanical Properties of Gd‐CeO2 Electrolyte for SOFC Prepared by Aqueous Tape Casting

Mechanical properties of gadolinium‐doped ceria (Ce_0.9Gd_0.1O_1.95, 10GDC) green tape prepared by aqueous‐based tape casting process were characterized by tensile test and shear punch test (SPT). SPT was found to be a useful method for characterizing mechanical properties of green tapes. Microstructures and mechanical properties such as flexural modulus, bending strength, and microhardness of tapes sintered at 1,300–1,500 °C have been evaluated. Indentation fracture toughness was also determined by the method of Palmqvist cracks at different applied loads for tapes sintered at 1,500 °C. Grain size measurements showed that excessive grain growth occurred during sintering despite using 10GDC nanopowders as the starting material. However, mechanical properties of sintered tapes improved by increasing sintering temperature and the results are comparable with those reported for 10GDC in literature.     

纳米微晶纤维素增强羟丙基纤维素复合膜的力学性能和透光度的研究

采用酸碱处理竹原纤维并辅以超声分散制备纳米微晶纤维素（NCC）,采用溶液浇铸/水分挥发的成型方法制备了纳米微晶纤维素增强羟丙基纤维素（HPC）全纤维素纳米复合膜.研究了NCC/HPC复合膜的力学性能、透光度以及热稳定性.随着纳米微晶纤维素含量的增加,复合膜的拉伸强度、拉伸模量、储能模量和热稳定性逐渐增大,与纯羟丙基纤维素膜相比,当纳米微晶纤维素质量分数为60％时,纳米复合膜的拉伸强度提高了8.5倍,拉伸模量提高了3.9倍,储能模量提高了3.7倍,而NCC/HPC复合膜的透光度没有出现明显的下降.     

Assessment and prediction of drying shrinkage cracking in bonded mortar overlays

Restrained drying shrinkage cracking was investigated on composite beams consisting of substrate concrete and bonded mortar overlays, and compared to the performance of the same mortars when subjected to the ring test. Stress development and cracking in the composite specimens were analytically modeled and predicted based on the measurement of relevant time-dependent material properties such as drying shrinkage, elastic modulus, tensile relaxation and tensile strength. Overlay cracking in the composite beams could be very well predicted with the analytical model. The ring test provided a useful qualitative comparison of the cracking performance of the mortars. The duration of curing was found to only have a minor influence on crack development. This was ascribed to the fact that prolonged curing has a beneficial effect on tensile strength at the onset of stress development, but is in the same time not beneficial to the values of tensile relaxation and elastic modulus.