Investigation of a new reactant for fluorinated polymer surface treatments with atmospheric pressure glow plasma to improve the adhesive strength

Poly(tetrafluoroethylene-co-perfluoro [alkyl vinyl ether]) (PFA) and polytetrafluoroethylene (PTFE) films were treated by three kinds of atmospheric pressure glow plasmas: an untreated sample was treated by He plasma or trimethoxyborane (TMB)/H2/He plasma, and a TMB-absorbed sample was treated by H2/He plasma. TMB was a new reactant for the treatment, to increase the films’ adhesive strength with an epoxy glue. These films were also treated by a wet method using a sodium solution (Tetra-Etch compound) and such films were used as the control samples. The peel strength values of the controls of PFA and PTFE were 3.5 and 9.5 N cm−1, respectively. The adhesive strengths of all plasma-treated PFAs were stronger than those of untreated one. Especially, the peel strength of the TMB/H2/He plasma-treated PFA showed the maximum value of 4.5 N cm−1, which was bigger than that of the control one. The adhesive strength of the TMB/H2/He plasma-treated PTFE films also showed the maximum peel strength, 7.9 N cm−1, but this value did not exceed that of the control PTFE. Such results suggested that the TMB/H2/He plasma had the advantage of providing better adhesive improvement of those polymers, especially PFA than the wet method could provide. The results of XPS and SEM indicated that TMB actively removed fluorine atoms from the polymer surface. Therefore, boron compounds are effective for the improvement of the adhesive strength between the fluorinated polymer and the epoxy glue.