G/flex is a toughened two-part epoxy designed for bonds and repairs that benefit from greater toughness and the ability to accommodate movement. It is useful for many wood, metal and fibreglass jobs and can bond selected plastics when the exact preparation procedure is followed.
Toughened does not mean soft, universal or preparation-free. Identify the substrate, remove damage and contamination, prepare the surface and test difficult plastics before relying on the repair.
Quick answer
Use G/flex where impact, vibration, dissimilar materials or difficult substrates make a brittle bond undesirable. Mix at the exact ratio, wet the prepared surfaces, maintain an adequate bond line and allow the full cure required for service.
What you need to know
- Use the neat adhesive for close-fitting joints and thicken only with an approved filler when a gap requires it.
- Flame treatment for polyethylene is a precise surface treatment, not an attempt to melt the plastic.
- Structural repairs still need sound geometry and adequate bonded area.
- Surface preparation is material-specific.
Tools and materials
- G/flex resin and hardener or pre-thickened version
- Accurate measuring and mixing tools
- Abrasives and approved cleaners
- Approved filler if needed
- Clamps and release protection
- Test coupons for difficult plastics
- Required PPE
Step-by-step method
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Assess the repair
Identify the material and how the joint is loaded. Remove cracked, oxidized or delaminated material. Increase bonded area or add reinforcement when the geometry demands it.
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Dry-fit and plan
Align the pieces, choose clamp locations and protect surfaces from accidental bonding. Confirm that the joint can retain a controlled adhesive thickness.
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Prepare the substrate
Clean and abrade wood, metal and fibreglass as specified. For polyethylene or other low-surface-energy plastics, use only the manufacturer’s approved treatment and test it.
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Measure and mix
Dispense equal parts only when the exact product instructions call for a 1:1 mix. Blend until uniform, scraping the sides and bottom.
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Wet out and fill
Apply a thin coat to both prepared surfaces. Add approved filler to a separate portion when the joint needs gap filling or a fillet, then apply without trapping air.
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Clamp moderately
Bring the parts into alignment and maintain contact. Do not squeeze the joint dry. Remove excess and shape fillets while the epoxy is workable.
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Cure and verify
Maintain the required temperature and support. Before full service, inspect the bond and test a representative coupon when the substrate or preparation is uncertain.
Watch the demonstration
The video is supporting material. Follow the current product instructions and safety data sheet for the products in your shop.
Common mistakes
- Assuming it bonds every plastic without treatment
- Flame-treating near solvents or flammables
- Melting or scorching plastic during treatment
- Over-clamping
- Using the repair to compensate for inadequate joint geometry
- Loading before full cure
Safety
Read the current resin, hardener and filler labels, technical data sheets and safety data sheets before opening the containers.
Wear splash-resistant eye protection and chemical-resistant gloves selected for the product. Keep epoxy off your skin; repeated exposure can lead to sensitization.
Provide ventilation appropriate to the job and product. Sand only fully cured material, control dust at the tool and wear suitable respiratory protection where the risk assessment requires it.
Mix only the quantity you can apply within the stated working time. Epoxy cures faster and produces more heat when left in a deep mixing pot.
Frequently asked questions
Is G/flex flexible after cure?
It is a toughened structural epoxy with greater ability to handle movement and impact than conventional rigid epoxies. It is not a soft elastomeric sealant.
Can it bond polyethylene?
It can bond certain polyethylene surfaces when the exact abrasion and flame-treatment procedure is followed. Test the actual grade and service condition.
Should I add filler?
Only when the joint needs gap filling, filleting or another property provided by an approved filler. Mix resin and hardener completely before adding filler.
Can I use it below the waterline?
Check the current product instructions and the whole coating system. Submersion, UV exposure and antifouling compatibility must all be considered.
Get the right materials for the job
Tell our team what you are making and how the finished part will be used.
Shop WEST SYSTEM G/flex epoxyAsk our technical teamSources and further reading
This guide provides general educational information. Products, substrates and working conditions vary. Follow the current technical data sheet, package directions and safety data sheet for every material you use. Structural, code-regulated or safety-critical work may require a qualified professional.
