RadiBond Adhesive bonding for Polymethylmethacrylat (PMMA)
Poly(methyl methacrylate) (PMMA), a transparent thermoplastic material also marketed simply as acrylic, acrylic glass or under trade names such as plexiglass, acrylite, lucite and perspex. The processing of PMMA is possible using most traditional techniques such as injection molding, compression molding, and extrusion. Also casting using resins of PMMA and catalysts is possible. PMMA is generally considered “sticky” however it generally doesn’t bind to metals and other hard surfaces. Read more about PMMA here.
Adhesion of PMMA on Stainless Steel
As mentioned above, PMMA is generally sticky but it does not bind directly to metal surfaces such as stainless steel. With the RadiSurf™ PMMA Adhesion system, we provide a surface coating for metal surfaces, that allows for an extremely strong chemical bonding between the thermoplastic and the metal. The adhesion layer is between 20 and 60 nm in thickness and allows for solvent welding, injection molding, compression molding and extrusion on the metal surfaces. It is generally recommended to post-process the samples with annealing.
Solvent welding of PMMA
The assembly of the RadiSurf™ coated metal surfaces with PMMA is easily done using solvent welding. The most effective solvent for the assembly is dichloromethane. In the video below we show how easily stainless steel samples and PMMA sheets are assembled using solvent welding. After only 10 seconds, the samples are cured enough to handle and after ~60 minutes full strength of the interface is obtained. The strength of the interfaces is in general defined by the strength of the PMMA blend used, as a cohesive fracture is usually observed in breakage.
Over molding of PMMA on metal surfaces
Metal surfaces, such as aluminium, stainless steel or titanium, coated with the RadiSurf™ PMMA Adhesion system can be used in over-molding procedures. From this molding process, PMMA is bonded to the metal surface directly. However, we recommend doing annealing to minimize stress in the samples after molding. As seen in over-molding experiments, it is the PMMA that fails and not the adhesion interface, meaning that the limit of strength is in the material used not the RadiSurf™ PMMA Adhesion system.
Adhesion of PMMA on titanium and other metals for biomedical applications
Our adhesion solution for PMMA is a 20-60 nm thin layer of polymer brushes that is chemically stable, safe and clean. Hence, our solution is especially suitable for medical applications, food contact systems etc. where traditional adhesives may be problematic. With such a thin adhesion layer a uniquely tight interface between the metal and thermoplastic material is obtained, which is beneficial in ensuring that no contaminants can enter the interface between the materials. Our adhesion solution may be ideal for implants, dental applications etc.
Adhesion of PMMA in design applications
With an extremely tight and transparent interface between the acrylic glass and the steel, you obtain unique design possibilities. You can even obtain high levels of adhesion on smoothly polished metal surfaces.
Stability of adhesion layer
The RadiSurf™ PMMA Adhesion system is stable for normal storage conditions and stable metal surface coated with the system can be stored for 2-3 months prior to use without any effect on the strength of the final adhesion.
Kyoko Shimizu, Kristoffer Malmos, Allan Hjarbæk Holm, Steen Uttrup Pedersen, Kim Daasbjerg, and Mogens HingeACS Applied Materials & Interfaces 20146 (23), 21308-21315
RadiBond™ PMMA Performance data
|Pull-out tensile strength|
|Stainless steel (316):|
|RadiBond™ PMMA||7 MPa|
|Non-treated: <||<1 MPa|
|Stainless steel (SS304):|
|RadiBond™ PMMA†||33 MPa|
|Non-treated:||< 1 MPa|
|*Cohesive fracture, †Cohesive fracture, Reason for strength applied before the fracture for the two different tests is due to differing chemistries between thin PMMA films and solid parts, the latter being more brittle.|