The peel strength of glued Stanyl parts depends on:
- The moisture
content of the Stanyl parts: dry as molded parts give higher peel strengths
than conditioned parts
- Environmental conditions (chemical attack),
size and kind of loading, size of the gap between the mating parts.
-
The application of a pretreatment: peel strengths measured on parts which are
not pretreated, are in the range of 3-4 MPa, while pretreatment shifts this
range to 10-17 Mpa.
Applicable pretreatments are:
•Abrading the surface with medium grit (80-150) emery paper or grit blasting
(especially effective for polyurethanes and acrylates)
•Etching the
surface (3 minutes at 20ºC) with a mixture of sulphuric acid (90%), potassium
dichromate (4%) and water (6%)
•Priming the surface by means of a
mixture of resorcinol, ethanol and p-toluene sulfonacid, a nitrilphenol based
solution or by means of a resin based on resorcin formaldehyde
•Plasma
or UV/ozone pretreatment (especially effective in combination with glues based
on epoxies)
The adhesive forms the weakest link in a glued Stanyl component due to the
lower temperature resistance of the adhesive. Consequently, adhesive bonding
is not a preferred joining technique for Stanyl. More stable systems can be
realized by using welding techniques or mechanical fasteners.
Arnite (PBT and PET)
Ethylcyanacrylate, methacrylatelastomer, ethyl, methyl, polyurethane, epoxy
and silicone type adhesives are suitable for Arnite PBT
and PET. Hot melt adhesives can also be applied. The area to be joined should
be lightly roughened and free of grease. The adhesion strength obtained,
however, will be below the specified product strength.
Arnitel (TPE)
Good bonding results can be achieved on Arnitel
components with polyurethane adhesives. Normally two-component systems are
used, with isocyanate or di-isocyanate hardeners.
Laminating Arnitel (e.g. to fabric) can be done with a TPU (thermoplastic
polyurethane) hot melt adhesive. The high temperature during melting of the
adhesive activates the hardener in the hot melt.
Xantar (PC), Xantar C (PC + ABS) and Stapron E (PC + PET)
A variety of adhesive types can be used for bonding Xantar
PC and PC-blends: epoxy, urethane, cyano-acrylic, acrylic, methacrylic,
silicone and hot melt. UV-transparent grades can also be bonded with UV-cure
types. Being amorphous materials, Xantar and PC-blends are relatively
sensitive to stress cracking induced by solvents, or to degradation due to
specific chemical substances like amines. The best results are achieved with
solventless adhesives.
Reactive adhesives make it possible to bond Xantar to many other materials.
The application of reactive adhesives is simple and fast compared to adhesive
solvents and the requirements to accurately align the joint areas are not as
high. Reactive adhesives with elastic properties after curing are used in the
automotive industry (e.g. for gluing lenses of transparent PC to metallized
surfaces or to opaque PC).
Reactive adhesives for Xantar based on epoxy resin must be free of low
molecular weight amines. Polymeric amino amides can be used as hardeners. The
possible reaction of residual amino groups with Xantar must be avoided by
ensuring that the amino groups react completely with the epoxy groups.
Two-component and one-component polyurethane adhesives have also proven
successful in joining PC, but they must be free of solvents and amines.
Silicone adhesives are particularly suitable as joint-gap-filler systems (e.g.
for glazing of industrial and greenhouse windows).
Cyano-acrylic adhesives, should be used only to bond stress-free parts that
will not be subjected to hydrolytic loads during use.
Mild surface abrasion (sanding) may improve adhesion by providing an increase
in both surface area and the potential for mechanical coupling.
