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This study examined the relative adhesion difference between untreated Rulon®
J and plasma treated Rulon® J.
It appears that plasma surface modification of Rulon® based
polymers is a viable way to enhance adhesion prior to bond-up, lamination, or
over-molding. This study observed approximately a 117% increase in lap shear
bond strength after plasma treatment.
Rulon® is an engineered tetrafluoroethylene polymer mixed with
other proprietary materials. Since a portion of the Rulon® material
is a fluorocarbon polymer, it is difficult to achieve good lap shear bond
strength without some method of surface treatment. Sodium naphthalene ammonia
dips or liquid etching of fluorocarbons are effective ways to enhance the
adhesion of fluorocarbon polymers. But, these highly caustic and toxic methods
are dangerous and can be difficult to control. Moreover, the resulting surface
of a dipped surface is discolored to brown or black.
Plasma surface modification is as effective as this dip method yet it is
environmentally friendly, safe, controllable and repeatable without
discoloration. Plasma is a quasineutral cloud of ion, electrons, and radicals.
The diffuse cloud produces the chemistry on the surface of materials
that is unique, providing wettable or adherent surfaces on materials that are
otherwise inert.
The Rulon® J samples in this study were subjected to a specific
plasma gas mixture to induce an adherent surface for a structural epoxy
adhesive.
The results are as follows:
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|
Untreated Rulon® J |
Treated Rulon® J |
| Contact Angle |
110° |
80° |
| Pull Strength |
45.9 psi |
100.0 psi |
Extension |
1.23 inch
| 6.35 inch |
It is important to note that the maximum pull strength of the treated sample
was compromised by the deformation of the test specimen (see figure 1).
In summary, it is difficult to achieve strong lap shear bond strengths on
fluoropolymers. Traditional surface preparation methods are dangerous and
discolor the material. By using plasma surface modification, the bond strength
has improved by approximately 117%, without discoloration.
For more information on surface modifications of plastics, elastomers and other
products available from TriStar Plastics Corp., call us at 1-800-TRISTAR or
visit our website at tstar.com.
We've created "The
TriStar Advantage" with you in mind.
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Surface Modification Brochure
