Thermoplastic Adhesive Film Research Articles

Development of high-performance hypodermic needle penetration resistance flexible cotton fabric using patterned thermoplastic adhesive film

Injuries caused by needle stick puncture are common and a concern in many industries, such as health services and waste collection. Personal protection against needle stick punctures currently use high-cost materials like high-density polyethylene (HDPE) woven fabric and Kevlar which compromises flexibility. In this paper, a low-cost, easy to produce, needle puncture resistant material is developed. Here, cotton fabric is overlaid by patterned Ethylene-Vinyl Acetate (EVA) based adhesive film and multiple layers are used that increase the needle penetration resistance by up to 478% as compared to a single layer of laminated fabric, while the flexibility decreased by only 12–49 %. Patterns of different shapes (hexagons and hexagons mixed with triangles) and sizes with nominal diameters ranging from 2.6 to 13.5 mm were tested, with the smaller nominal dimensional shapes having a greater flexibility. Patterned hot film had a similar needle penetration resistance as plain hot film but was significantly more flexible. Increasing the number of laminated fabric layers from 1 to 3 resulted in an increase in needle penetration resistance force from 2 N up to 8 N.

Experimental and numerical investigation of thermoplastic honeycomb sandwich structures under bending loading

Sandwich structures have attracted increasing attention in engineering applications due to their lightweight effect and energy absorbing capacity. In the current work, fully-thermoplastic honeycomb sandwich structures with 100% recyclability were developed, which consisted of continuous glass fiber-reinforced polypropylene (PP/GF) face sheets, polypropylene (PP) core and assembled using thermoplastic adhesive films. The experimental tests and numerical analysis were conducted to investigate the bending behavior and energy absorption of PP-based sandwich structures. Firstly, a series of three-point bending experiments were tested and the influences of structural factors on bending behaviors were investigated. The typical deformation modes were explored and the damaged microstructure of face-sheets were observed. Finite element models of the sandwich structures were developed to capture the deformation process, and the simulation results were validated with the experimental data. Afterwards, a multi-objective optimization was performed to seek for the maximum specific energy absorption together with the minimum initial peak force simultaneously. Response surface method was adopted to construct objective response functions and used for the defined optimization problem.

Investigation of joining of continuous glass fibre reinforced polypropylene laminates via fusion bonding and hotmelt adhesive film

As the demand for the lightweight and recyclability in automobile industry increases, continuous fiber reinforced thermoplastics (FRTP) have received extensive attention due to their excellent mechanical properties and fully recoverability. One of the ongoing challenges is to achieve sufficient joint strength in spite of the inertness (i.e. lack of functional groups) of some thermoplastics. In this current work, two joining techniques, including fusion bonding and hotmelt film were applied to bond continuously glass fiber reinforced polypropylene (PP/GF) composites. Firstly, operating procedures during the fusion bonding process of PP/GF laminates were focused and assessed. Tests were carried out to investigate the effects of fusion temperature, ply sequence of PP/GF substrates and fusion depth on lap-shear joint strength. The cross-section microstructure and fracture surface were observed by optical and scanning electron microscopy. Then, the adhesion of bonded PP/GF specimens using thermoplastic adhesive film was further investigated. The lap-joint strength and failure mode was compared with fusion-bonded counterparts. The results suggested that fusion-bonded of PP/GF exhibited higher joint strength while joining with hotmelt adhesive film experienced shorten processing period and lower molding pressure. Therefore, fusion bonding and hotmelt adhesive film provide low-cost, feasibility and recyclable adhesion methods, which are promising for joining of continuous fiber-reinforced thermoplastic composites.

Improvement of the adhesion of continuously manufactured multi-material joints by application of thermoplastic adhesive film

The development of tailored lightweight solutions is especially required for the support of the structural change from combustion to electric driven vehicles, due to the still challenging weight of the currently used lithium-ion batteries. The manufacturing of tailored multi-material structures consisting of steel and carbon fibre reinforced thermoplastics (CFR-TP) within a continuous roll forming process is a promising approach to combine innovative lightweight design and large-scale production capability.Nevertheless, fusion bonding as joining technology for steel and carbon fibre reinforced thermoplastics within a continuous process is still challenging because of not achieving sufficient joint strength. The application of adhesive films, which can be easily integrated in a roll forming line by coil-coating processes, seems to be promising to increase the adhesion between metal and CFR-TP. Therefore, a thermoplastic adhesive multilayer-film, consisting of functionalized polymers in different thermoplastic layers, is used within this study. The most important challenge consists in the even heating and consolidation of the multi-material structure within the limited joining time in a continuous fusion bonding process.To enable a variation in joining time, the existing test set-up is extended to a reversible, continuous process. The manufactured hybrid specimens as well as high pressure blasted references without adhesive film application are tested mechanically by climbing drum peel test to determine the production-related influence. In addition, micrographs of specimens are evaluated analytically by scanning electron microscopy.The examinations show the significant improvement of adhesion between steel and CFR-TP by application of thermoplastic adhesive multilayer-film. Lower steel temperatures in combination with reversing operation result in peel resistances almost comparable to sequential process.

Evaluation of the air permeability of elastic knitted fabrics and their assemblies

PurposeThe purpose of this paper is to evaluate the air permeability of knitted fabrics containing elastane fibre and their seams applying both the new approach based on fabric thickness measurement at different pressures and standard method.Design/methodology/approachInvestigations were performed with commercially available eight polyester knitted fabrics containing different elastane yarn proportion. Bonded seams were laminated applying the urethane thermoplastic adhesive film of 0.175 mm thickness. Bonds were laminated by heat at 5.6 kPa pressure applying pressing device GTK DEA 25 R at 140°C temperature for 40 s duration. Sewn seams were assembled with 607 covering chain stitch applying 5.0 stitches per cm density and 512 overedge chain stitch applying 5.0 stitches per cm density. Specimens without and with the seams were conditioned in standard atmosphere conditions according to the standard LST EN ISO 139 before air permeability testing according to the standard LST EN ISO 9237. Standard thickness of the investigated knitted fabric was determined according to the standard EN ISO 5084. It is known from literature that the porosity is dominant factor influencing the air permeability of knitted fabrics. Therefore, the assumption was made that due to fabric porosity knitted fabric thickness being measured at different pressures also may differ. Thus, the permeability property may also be related to the difference between fabric’s thicknesses being measured under different pressures which may be applied with different material thickness gauges.FindingsThere was shown that fabric assemblies make the significant influence on the textile permeability to air. The results obtained indicate that the air permeability of the investigated knitted fabrics depends not only on their structure parameters but also on the fabric seam type. Air permeability of the specimens with the seams was lower than one of specimens without the seams. The highest decrease in permeability which ranged from 19.9 per cent up to 60.0 per cent was determined for the bonds. Fabric specimens with 607 covering chain stitch seam were in the second place with regard to the previously considered parameter. And, their permeability was decreased from 0.6 per cent up to 52.6 per cent. Changes in the air permeability of the specimens with 512 overedge chain stitch seam were lowest in the range of investigated assemblies. Based on the determined results, it was concluded that the thickness difference of the specimens with and without seams measured at different pressures is related to fabric porosity which makes the significant influence on the air permeability.Practical implicationsThe samples of investigated fabrics were taken from the two companies which manufactures leisure clothing and sportswear such as skiing or swimming costumes, etc. Thus, the obtained investigation results are significant not only for clothing science but also leads the improvement of clothing quality in fashion industry.Originality/valueAssuring the comfort of the human body is one of the most important functions of clothing, especially of sportswear and leisure wear. Knitted fabrics should not only be elastic, but also have high air permeability for easily transmit of the perspiration from the skin to the atmosphere, thus making the wearer to feel comfortable. In this research, the air permeability of commercially available polyester knitted fabrics containing different amount of elastane was investigated and the influence of fabric assemblies on the air permeability property was evaluated. A new approach based on the fabric thickness measurement at different pressures and the standard methods for the evaluation of air permeability were used.

Delamination toughness of ultra high molecular weight polyethylene (UHMWPE) composites

Ultra high molecular weight polyethylene (UHMWPE) fibre reinforced composites are an important group of material for armours solutions, where their unique combination of properties could be utilized. A commonly observed failure mode in this kind of unidirectional laminated composites under impact ballistic is delamination between the composite layers. In the present study, an investigation on the delamination toughness behaviour exhibited by UHMWPE composites laminated was made. The interlaminar Mode II critical strain energy release rates of (UHMWPE) fibre reinforced composites were characterized using the End Notch Flexural (ENF) test. Critical strain energy release rate was obtained from the load – deflection test data using the beam theory expression. It was found that the energy release rate of the composite exhibited a very low value of around 60J/m 2 using a moulding pressure of approximately 1200 psi. In order to analyse the delamination resistance of composite, the effects of changing the manufacture process variables and the use of a thermoplastic adhesive film in the composites were investigated. The composite laminates were produced by hot compressing moulding using a film-stacking procedure. It was found that the damage resistance of the UHMWPE composite was influenced by the manufacture method, which affects the Mode II interlaminar fracture toughness and the ballistic response of composites.

Design and structural testing of smart composite structures with embedded conductive thermoplastic film

The ongoing research and development of cost effective technology for remotely queried sensors for health and usage monitoring of composite structures has lead to the application of electrically conductive thermoplastic adhesive films. This paper intends to provide an in depth overview of a newly developed technology for the design and manufacturing of smart structures by introducing the application of electrically conductive thermoplastic adhesive films. The current technology is discussed and compared with this newly developed technology. It is shown that the structural aspects of this new technology are advantageous to the concept of smart structures as a whole. Fabrication and manufacturing techniques for this new technology is discussed, including the suitability of the process for automation. Specifically, standard tensile testing of the manufactured composite coupons with embedded thermoplastic conductive adhesive films have performed and compared to the test results from copper embedded coupons. The effect of embedded thermoplastic stripes on stiffness as well as strength of the parent laminated structure is evaluated and discussed. Furthermore, fatigue testing was performed at various ultimate failure strength percentiles to determine some degree of the fatigue life of the composite and the embedded conductive and insulting films. The conductive thermoplastic films are found to be structurally superior to copper when embedded in a composite structure, but the electrical conductivity is not as good as copper or other metallic conductors.

Environmentally Friendly Dry Thermoplastic Adhesive Films and Webs for Industrial Bonding Applications

Since the mid-1980s in many industrialised countries, a growing number of environmental laws and regulations governing workplaces have seriously eroded the share of solvent-borne adhesive systems, set more and more stringent conditions on the use of water-based adhesives, and are about to severely restrict the flame bonding process. This environmental driving force (together with processing advantages) has been promoting and accelerating the use of dry thermoplastic adhe sives. This article presents the characteristics of the dry thermoplastic adhesive films and webs made by SARNATECH-XIRO Ltd., their processing methods, and their fields of application.

Evaluation of polyimide films as adhesives

A commercially available LARC-TPI film and an experimentally prepared film of LARC-TPI with 5 mol pct of 4,4-prime-oxydianiline (ODA), designated as LARC-TPI/ODA, were evaluated as thermoplastic adhesive films for bonding Ti-6Al-4V. Lap shear strength was used to evaluate the materials as adhesives. They were characterized after fracture by determining the glass transition temperature, T(g). The mode of failure is also reported. Thermal exposure at 240 C for 500 and 1000 h and a 72-h water-boil were conducted on lap shear specimens prepared with the two adhesive films. Lap shear tests were conducted at room temperature, 177 C, 204 C, and 232 C before and after exposures.