Adhesive bond strength tests butt joints

Different methods have been devised to test the bondability of the treated plastic. The specimen can be joined in different ways butt joint, disk joint, and lap shear. An adhesive layer or film is applied to the treated surface, which is then placed against the substrate and heated in a press or oven. The substrate could be a duplicate of the plastic itself. Table 14.1 gives the bond values of fiuoroplastics before and after etching, obtained by the lap shear test method. Bond strengths of the treated surfaces of PTFE, PVF, and ECTFE are larger than that of the untreated surfaces by an order of magnitude or more. 

A comparison of the effect of the two treatments on butt joint strengths with an epoxy adhesive is shown in Fig. 9. For test temperatures less than the Tg of the adhesive, joints made with grit blasted adherends have higher strengths. Bond strengths with either type of adherend are enhanced if an additional chemical etching treatment is used (see later). 

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