Adhesion enhancement of polymer surfaces by atmospheric plasma treatment

Abstract

An atmospheric pressure non-equilibrium plasma (APNEP) developed in the UK by EA Technology Ltd is currently being investigated in collaboration with the University of Surrey. Of the many applications of surface modification that can be induced using plasmas, adhesion enhancement is one of the most commercially important. In this paper, we illustrate the use of an atmospheric plasma to enhance the adhesion characteristics of low-density polyethylene (LDPE) and poly(ethylene terephthalate) (PET). The polymers were treated in the remote afterglow region of an atmospheric pressure plasma to avoid the thermal effects that can cause degradation for thermally sensitive materials when placed in direct contact with the plasma. Reactive (oxygen containing) and inert (oxygen free) atmospheric plasmas rapidly impart adhesion enhancement by a factor of two to ten as measured by 180° peel tests. However, extended exposure to the atmospheric plasma does not impart additional adhesion enhancement as the surface is ablated revealing the underlying polymer with poor adhesive characteristics. In contrast, vacuum plasma treated LDPE and PET show increased adhesion with extended plasma treatment. An adhesion enhancement in excess of two to three orders of magnitude was found to be achievable for vacuum plasma treatment times greater than 10 min.

Improvement of wettability and absorbancy of textile using atmospheric pressure dielectric barrier discharge

“…1 Despite these properties, they are often unsuitable for use due to their low surface free energy, leading to poor wettability and poor adhesion. 2 By modifying the surface of the these polymeric fibers, surface roughness is increased and moisture absorption is decreased making them more attractive. 3 Over the years, several methods have been developed to modify the polymer surface for improved adhesion, wettability, printability, dye uptake, and other technologically important characteristics using various techniques like wet chemical treatment, mechanical abrasion, flame treatment, biological treatment, sonification using nano particles, plasma processing, etc.…”

Surface characterization of plasma‐modified polyethylene by contact angle experiments and ATR‐FTIR spectroscopy

“…[1] However, despite these excellent characteristics, PE is often unsuitable for use due to its low surface free energy, leading to poor wettability and poor adhesion. [2] For optimum adhesion, the surface free energy of the polymer should be larger than that of the material to be bonded with. Similarly, for effective wetting by a liquid, the surface free energy should exceed the surface tension of the liquid.…”

Effect of Atmospheric Pressure Plasma Modification on Polyimide and Adhesive Joining with Titanium

“…Finally, the total surface energy 'c S ' was estimated by adding c S P and c S D as given in Eq. [2]:…”

“…Adhesive bonding is replacing conventional joining methods such as riveting, welding, and mechanical fastening in a variety of applications because of better fatigue performance and high strengthto-weight ratio. [1,2] Mechanical joining results in stress concentration and reduces the overall load carrying capacity of the structure. [3] An adhesive joint can distribute the applied load over the entire bonded area with more uniform stress distribution and is suitable for joining dissimilar materials with low manufacturing cost.…”