Gluing Composites

Bonding composites is a growing market in Ireland. The renewable energy sector, automotive & marine sectors have seen a major leap in the use of adhesives for many critical applications.

There are a range of adhesives suitable for gluing composites. For the strongest and most durable bonds possible, we always recommend some type of surface preparation. Surface preparation techniques will ‘energize’ the surface to enhance wetting and facilitate a greater degree of cross linking on a molecular scale.

There are two key methods of surface preparation for composites, sand paper abrasion or grit blasting, using abrasive media such as silica or alumina.

We recommend abrading & solvent wiping for the materials being bonded.

Remember, with all composite bonding, open time after cleaning is always the enemy. A freshly cleaned surface (abrasion & degreasing) will try to stabilise over time and the desired effect will be lost. The surface will attract water and other contaminants. In addition, adhesive left on the surface for an extended time will be effected by water & carbon dioxide.

Consistent bond line thickness of the adhesive is critical. Without uniform adhesive thickness, the strength of the joint is only as strong as the weakest point. Maintain film thickness using shims, beaded adhesive or structural tapes.

Maintain uniform clamping pressure to achieve optimum adhesive wet-out and fully optomise the bond strength. Avoid pressures in excess of 50 psi as a starved joint may result.

Use fine grain P120 sand paper, emery cloth, steel wool, or grit blasting. Abrade enough just to clean and roughen the surface slightly. After an abrasion treatment, remove all loose particles before applying adhesive. Brush the surface or blow with compressed air, and then degrease to clear away all loose particles and residual oils.

Solvent wiping using cheesecloth damped with solvent. Depending on the materials to be degreased our X35, T160 or T559 may be used. The double wipe method is recommended (wipe with a solvent saturated cloth followed by a wipe with a clean cloth).

Abrading and degreasing is enough surface preparation for all but the most demanding industrial applications. If these materials are being bonded together, a change in the surface properties may be required to get good adhesion. Specifically, these plastics are considered low surface energy materials and altering the surface to increase the surface energy will be required in some cases.

This involves using:

  • Solvent wiping (almost always)
  • X90 plastic primer
  • Scorching the surface
  • Grit blasting
  • Or acid etching the surface

Because all materials are slightly different, please consult the Glue Guru for the most effective way to treat the material for best adhesion glueguru@wipolymers.ie

Chemistry Grading

  • Fair
  • Good
  • Excellent

Material Type

Surface Preparation Required

Adhesive Suggested Chemistry

Acrylonitrile butadiene styrene     (ABS) Degrease with X35. Abrasion may be required with P100 or P150 paper. Degrease again.
  • Two component epoxy
  • Two component polyurethane
  • Two component acrylic, Cyanoacrylate
Acetal Degrease with X35. Abrasion may be required with P100 or P150 paper. Prime with X90.
  • Cyanoacrylate. Very difficult to bond to.
Corian Generally not required
  • Two component acrylic, two component epoxy
Carbon Reinforced Plastic (CRP) Degrease with X35. Abrasion may be required with P100 or P150 paper. Degrease again.
  • Cyanoacrylate
  • Two component epoxy, two component acrylic.
Fibre Reinforced Plastic (FRP) Degrease with T160. Abrasion may be required with P100 or P150 paper. Degrease again.
  • Cyanoacrylate
  • Two component polyurethane, two component acrylic.
Graphite/Carbon Composite Degrease with T160. Abrasion may be required with an emery cloth. Degrease again.
  • Cyanoacrylate
  • Two component acrylic.
Glass Reinforced Plastic (GRP) Degrease with T160. Abrasion may be required with P100 or P150 paper. Degrease again.
  • Cyanoacrylate
  • Two component epoxy, two component polyurethane, two component acrylic.
Liquid Crystal Polymer (LCP) Not required
  • Two component acrylic
  • Two component epoxy
  • Cyanoacrylate, UV cure
Nylon Must be fully dry. Degrease with T160. Abrasion may be required with P150 paper. Degrease again.
  • Two component acrylic, two component polyurethane.
Polyphenylene Oxide (PPO) Degrease with X35. Abrasion may be required with P150 paper. Prime with X90.
  • Cyanoacrylate. Very difficult to bond to
Polytetrafluoroethylene (PTFE) Degrease with X35. Abrasion may be required with P150 paper. Prime with X90.
  • Cyanoacrylate. Very difficult to bond to
Polyether ether ketone (PEEK) Degrease with X35. Abrasion may be required with P150 paper. Prime with X90.
  • Cyanoacrylate. Very difficult to bond to
Phenolic Degrease with T556. Abrasion may be required with P100 or P150 paper. Degrease again.
  • Two component polyurethane
  • Two component acrylic
  • Two component epoxy
Polyester Degrease with T556. Abrasion may be required with P100 or P150 paper. Degrease again.
  • Two component polyurethane
  • Two component acrylic
  • Two component epoxy
Sheet Moulding Compound (SMC) Degrease with T160. Abrasion may be required with P150 paper. Degrease again.
  • Cyanoacrylate
  • Two component polyurethane
  • Two component acrylic, two component epoxy

For bonding small components, cyanoacrylate super-glue is possibly the best option. These adhesives come in a range of viscosities form high viscosity gel type products to water thin wicking grades, very commonly used in the craft & hobby sector. Our X60 cyanoacrylate adhesive finds particular use in bonding many plastics.

For structural bonding of plastics and in particular composites, either structural methacrylate or structural epoxy products are used. These can be either 10:1 mixing ratio or 1:1 mixing ratio.  Methacrylate adhesives for bonding plastics & composites are at the core of. These adhesives offer excellent resistant properties to fatigue, peel & shear and environmental resistance.

For bonding large composite parts any of the Scigrip 1:1 or 10: 1mixing ratio products are suitable. These adhesives give a working time of 12 minutes to 130 minutes and they are used where the glue line or where good gap filling is required. These products are typically used to bond composite parts such as turbine blades, composite doors and in the boat building / repair sector. An emerging market for our products is the renewable energy market. Scigrip SG300  has established itself in the marine and turbine blade sector. These adhesives are also suitable for bonding Fibre Reinforced plastics (FRP), ABS, Vinyl Ester, polyester and epoxy. Scigrip SG5000 is the excellent all-rounder where maximum shear strength is a prerequisite.

Bonding medium size substrates, particularly polycarbonate, ABS or GRP, Scigrip SG300  or Scigrip SG600  is suggested where a non sag glue-line is needed. These are thixotropic two component methacrylate adhesives with extremely high shear & peel strength. These products have non slump characteristics and an excellent flow property which gives excellent gunability. It has excellent resistance to humidity, fuels and oils.

Bonding medium size to small composite parts may be achieved with the use of our X10 or X15 two component 1:1 mix ratio methacrylate adhesives. This adhesive finds extensive use in bonding composite materials such as Corian®.

Bonding in the marine sector is the territory of Scigrip SG100. This adhesive is bright white and is available in two working times, 14 minute and 40 minute.

Bonding low energy plastics such as Polyethylene, polypropylene, PVC, Thermoplastic Olefins as best accomplished with Scigrip PPX5 is the Ultimate Plastic Bonder. This adhesive will also work with bonding exotic plastics to dissimilar substrates.

X95 is a steel filled epoxy glue, designed specifically for use in the metal & composite bonding & filling sector. The product is typically used to fill gaps & cracks in most rigid composite plastics.

The selection of the correct adhesive depends on the materials being bonded, and in particular the working times & fixture times available in the manufacturing environment.

To achieve optimum plastic & composite bonding, it is important to abrade the surface, clean the surface to remove debris, use the correct adhesive, maintain the adhesive film thickness, provide constant & uniform clamping pressure, cure the adhesive under the correct conditions.