FOR UHMW PE
Ultra high molecular weight polyethylene adhesion to dissimilar materials for structural
What is UHMW?
Ultra high molecular weight polyethylene (UHMW) is a tough wear-resistant
plastic with low coefficient of friction, outstanding impact strength
with excellent chemical and moisture resistance
and broad temperature range. Go to this Wikipedia link - UHMW - for a more detailed description.
What are some uses of UHMW?
It is frequently used as a linear bushing in conveyor, bulk material handling, railroad and logging applications. These applications take advantage of the toughness and slippery nature of UHMW...the third most slippery of the plastics only surpassed by some fluoropolymers such as PTFE and FEP (Teflon) and acetal (Delrin), which are much more expensive.
Applications for hose linings take advantage of UHMW's high chemical resistance as well as abrasion resistance. The exceptional water resistance combined with very high impact and abrasion resistance make it particularly useful for skis, skateboards, snow boards, boat bottom liners and boat dock bumpers.
One major Pacific port authority successfully bonded sheets of UHMW to the sides of steel hulled barges, using the RELTEK BONDiT B-45TH to function as bumpers for docking cruise ships and military aircraft carriers.
How do you bond UHMW with an adhesive to dissimilar materials?
Industry producers of UHMW generally report it cannot be bonded without special surface conditioning, due to the high degree of polymer chain alignment and hydrogen pairing on the surface. However, UHMW CAN be bonded to itself and to other substrates without significant preparations (light abrasion is usually recommended) using BONDiTTM brand adhesives manufactured by RELTEK.
With light abrasion some of the paired hydrogen can be broken up to create tertiary hydrogen (connected to a tertiary carbon and not sterically hindered or paired with another adjacent hydrogen) which are chemically active and increase the surface energy. BONDiT B-4x series epoxy products are designed to take advantage of the tertiary hydrogen to form good bonds, producing with a UHMW/Steel lap joint a typical lapshear strength of 350 PSI to 450 PSI (pounds-per-square-inch) depending on curing method.
Among the other substrates which UHMW can be bonded to using BONDiTTM products
are: Delrin, fluoropolymers, rubber, polyethylene, polyolefin, polypropylene, polyurethane, silicone, thermoplastics, thermoset, glass and ceramics, wood, metals, stone, aggregate and concrete.
Corona or flame (plasma) etch is occasionally used to prepare the UHMW surface which
strengthens the bond by reacting surface chains with oxygen to form oxane bonds, significantly increasing the bond strength. BONDiT B-4x series epoxies readily form high strength bonds to the oxide rich substrate. Chemical etching with sulfur trioxide in Freon has also been successfully employed to increase the surface energy of the UHMW, but is a much more complex process compared to flame etching.
Most application do not need such enhancement and work well with just the
B-45TH adhesive on a lightly abraded (#100-120 grit) surface. The need to pretreat
the UHMW by etching occurs in about 15% of the applications. If abrasion is not possible the BONDiT B-46TH has the capability of adhering to the unabraded UHMW surface. It will even bond similarly to untreated Teflon and Delrin.
If you think that your application may require this treatment, please call
at (707) 284-8808 or email us at firstname.lastname@example.org for technical support as this technique
requires some skill and experience. We can provide you with written instructions to guide you through a process for which in our experience there is a high degree of miss information extant within industry.
How do you design with UHMW for Harsh Environments?
are among the few available that as a UHWM adhesive will bond
to itself or other substrates with differing coefficients of
(COE). BONDiTTM products are renowned
for their resistance to harsh environments and for
deployment without debonding. Bonding UHMW to dissimilar materials is a particular problem due to it's very high thermal expansion coefficient--fourteen times that of steel, and among the highest of the engineering plastics--twice that of acetal and polypropylene. As a consequence the adhesive bond joint must be designed to accommodate the expansion/contraction differential between materials to avoid bond failure. The BONDiT B-4X series epoxies are especially designed for that purpose, ranging in elongation (stretch) from 10% to 500%. Adhesive joints designed with these products have been successfully thermal cycled -50°F to+150°F, and even cryogenic temperatures (liquid nitrogen) and as high as 300°F.
Our first product recommendation for bonding UHMW is BONDiTTM B-45TH or BONDiTTM B-482TH.
Our recommendation would change if you are overmolding or if there are other
special adhesive needs.
If overmolding, we would recommend priming the substrate
BONDiTTM A-43. An example would be molding either, thermoplastic polyurethane, two-part urethane rubber or rubbers in general such as EPDM to UHMW.
Or, if exceptional chemical resistance
we would recommend the BONDiTTM B-481 or B-4811.
Abundant engineering support is provided at RELTEK for our customers
Please feel free to call or email us with your questions. Our recommendations are founded in compressive experience. We are willing to share that experience with you to ensure your success—whether or not you become a RELTEK customer, we welcome the opportunity to serve you.
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