Rubber Solution Adhesives for Wood-to-Wood Bonding

Rubber solutions were prepared and used for bonding wood pieces. The effect of the variation of chlorinated natural rubber (CNR) and phenolformaldehyde (PF) resin in the adhesive solutions on lap shear strength was determined. Natural rubber and neoprene-based adhesive solutions were compared for their lap shear strength. The storage stability of the adhesive prepared was determined. The change in lap shear strength before and after being placed in cold water, hot water, acid, and alkali was tested. The bonding character of these adhesives was compared with different commercially available solution adhesives. The room-temperature aging resistance of wood joints was also determined. In all the studies, the adhesive prepared in the laboratory was found to be superior compared to the commercial adhesives.

Nonlinear analysis of adhesively bonded lap joints considering viscoplasticity in adhesives

This paper presents nonlinear finite element analysis of adhesively bonded joints considering the elastoviscoplastic constitutive model of the adhesive material and the finite rotation of the joint. Though the adherends have been assumed to be linearly elastic, the yielding of the adhesive is represented by a pressure sensitive modified von Mises yield function. The stress-strain relation of the adhesive is represented by the Ramberg-Osgood relation. Geometric nonlinearity due to finite rotation in the joint is accounted for using the Green-Lagrange strain tensor and the second Piola-Kirchhoff stress tensor in a total Lagrangian formulation. Critical time steps have been calculated based on the eigenvalues of the transition matrices of the viscoplastic model of the adhesive. Stability of the viscoplastic solution and time dependent behaviour of the joints are examined. A parametric study has been carried out with particular reference to peel and shear stress along the interface. Critical zones for failure of joints have been identified. The study is of significance in the design of lap joints as well as on the characterization of adhesive strength. (C) 1999 Elsevier Science Ltd. All rights reserved.

Application of modelling for predicting the behaviour of polymers and adhesives in microelectronic and photonic devices

With the growth in computing power, and advances in numerical methods for the solution of partial differential equations, modeling technologies based around computational fluid dynamics, finite element analysis and optimisation are now being widely used by researchers and industry. Polymer and adhesive materials are now being widely used in electronic and photonic devices. This paper will illustrate the use of modeling tools to predict the behaviour of these materials from product assembly to its performance and reliability.

Studies on adhesives for bonding rubber to rubber and rubber to textiles

The primary objective of this investigation has been to develop more efficient and low cost adhesives for bonding various elastomer combinations particularly NR to NR, NR/PB to NR/PB, CR to CR,NR to CR and NR to NBR.A significant achievement of the investigation was the development of solventless and environment friendly solid adhesives for NR to NR and NR/PB to NR/PB particularly for precured retreading. Conventionally used adhesives in this area are mostly NR based adhesive strips in the presence of a dough. The study has shown that an ultra accelerator could be added to the dough just before applying it on the tire which can significantly bring down the retreading time resulting in prolonged tire service and lower energy consumption. Further latex reclaim has been used for the preparation of the solid strip which can reduce the cost considerably.Another significant finding was that by making proper selection of the RF resin, the efficiency and shelflife of the RFL adhesive used for nylon and rayon tire cord dipping can be improved. In the conventionally used RFL adhesive, the resin once prepared has to be added to the latex within 30 minutes and the RFL has to be used after 4 hours maturation time maximum shelf life of the RFL dip solution being 72 hours. In this study a formaldehyde deficient resin was used and hence more flexibility was available for mixing with latex and maturing. It also has a much longer shelf life. In the method suggested in this study, formaldehyde donors were added only in the rubber compound to make up the formaldehyde deficiency in the RFL. The results of this investigation show that the pull through load by employing this method and the conventional method are comparable. This study has also shown that the amount of RF resin with RFL adhesive can be partially replaced by other modifying agents for cost reduction.Cashew nut shell liquid (CNSL) resin can be employed for improving the bonding of dipped nylon and rayon cord with NR.Since CNSL resin cannot be added in the dip solution since it is not soluble in water, it was added in the rubber compound. The amount of wood rosin in the rubber compound can be reduced by using CNSL resin.Another interesting result of the investigation was the use of CR based adhesive modified with chlorinated natural rubber for CR to CR bonding. Addition of chlorinated natural rubber was found to improve sea water resistance of CR based adhesive. In the bonding of a polar rubber like nitrile rubber or polychloroprene rubber to a non polar rubber like natural rubber, an adhesive based on polychloroprene rubber was found to be effective.

Development of Novel Polymer based Adhesives

Novel latex based and solution based adhesives were prepared and evaluated for wood to wood bonding.These adhesive were found to be superior to commercical adhesives like fevicol and dentrite.Novel adhesives were prepared for leather to leather bonding and these were also found to be more efficientt than the polyurethane type and dentrite adhesives used commercially.A novel strip adhesive system employing very low amount of solvents was tried successfully for rubber-to-metal bonding.Further ,a novel adhesive system was investigated successfully for bonding copper coated bead wire and steel cord to rubber by modifying it with chloroprene rubber.

Multi-criteria selection of structural adhesives to bond ABS parts obtained by rapid prototyping

One of the most used methods in rapidprototyping is Fused Deposition Modeling (FDM), which provides components with a reasonable strength in plastic materials such as ABS and has a low environmental impact. However, the FDM process exhibits low levels of surface finishing, difficulty in getting complex and/or small geometries and low consistency in “slim” elements of the parts. Furthermore, “cantilever” elements need large material structures to be supported. The solution of these deficiencies requires a comprehensive review of the three-dimensional part design to enhance advantages and performances of FDM and reduce their constraints. As a key feature of this redesign a novel method of construction by assembling parts with structuraladhesive joints is proposed. These adhesive joints should be designed specifically to fit the plastic substrate and the FDM manufacturing technology. To achieve this, the most suitable structuraladhesiveselection is firstly required. Therefore, the present work analyzes five different families of adhesives (cyanoacrylate, polyurethane, epoxy, acrylic and silicone), and, by means of the application of technical multi-criteria decision analysis based on the analytic hierarchy process (AHP), to select the structuraladhesive that better conjugates mechanical benefits and adaptation to the FDM manufacturing process

An approximate method for the solution of an influence function foil rolling model

Fleck and Johnson (Int. J. Mech. Sci. 29 (1987) 507) and Fleck et al. (Proc. Inst. Mech. Eng. 206 (1992) 119) have developed foil rolling models which allow for large deformations in the roll profile, including the possibility that the rolls flatten completely. However, these models require computationally expensive iterative solution techniques. A new approach to the approximate solution of the Fleck et al. (1992) Influence Function Model has been developed using both analytic and approximation techniques. The numerical difficulties arising from solving an integral equation in the flattened region have been reduced by applying an Inverse Hilbert Transform to get an analytic expression for the pressure. The method described in this paper is applicable to cases where there is or there is not a flat region.