Glass Fibre Reinforced Filler for Metal, Body & Repair Work

A rust hole, damaged body panel or cracked fibreglass repair needs more than a cosmetic skim.

Soudal Polyfiber is a two-component, glass fibre reinforced polyester filler made for strengthening & repairing damaged areas in metal, polyester, fibreglass & suitable repair surfaces. The reinforcing fibres make it particularly useful for automotive body repairs, rust-damaged sections, small holes & larger repairs where additional strength is needed before sanding & finishing.

Preparing a repair that will later be painted or refinished? Browse Paints, Finishes & Decorating Tools. For scraping, trimming & general preparation work around the repair, explore Hand Tools.

Unlike a flexible joint filler, Polyfiber chemically cures to form a hard, reinforced repair. That distinction matters: it is intended for filling & reinforcing damaged rigid surfaces, not accommodating ongoing joint movement.

What Is Soudal Polyfiber?

Soudal Polyfiber is a glass fibre reinforced polyester putty based on unsaturated polyester resins.

It uses a two-component system:

► A-component – fibre reinforced polyester filler
► B-component – benzoyl peroxide hardener

Once correctly mixed, the components chemically cure to create a hard repair that can be sanded & finished.

The glass fibres are the defining feature. They provide additional reinforcement where the repair needs more body & strength than a fine finishing filler alone.

Soudal Polyfiber is suited to repair work involving:

► Metals
► Polyester
► Fibreglass
► Suitable wooden repair areas
► Automotive body panels
► Boats
► Surfboards
► Rust-damaged sections
► Small holes & dents

The current Industrial Shed collection carries Soudal Polyfiber 1kg, giving trade users a practical quantity for workshop, body repair & maintenance work.

Why Choose Soudal Polyfiber?

Polyfiber sits between the damaged substrate & the finishing stages that follow.

Its purpose isn't simply to hide a defect. It helps fill & reinforce suitable damaged areas so the repair can then be shaped, sanded & prepared for its final finish.

Key characteristics include:

► Glass fibre reinforcement for stronger repair build-up
► Two-component chemical cure
► Fast curing for efficient repair work
► Approximately 5-minute open time under specified conditions
► Sandable after approximately 20–30 minutes, depending on conditions
► Hard cured finish
► Long-lasting adhesion to properly prepared compatible substrates
► Can be applied in multiple thin layers where necessary
► Repair can be sanded & painted after curing
► Suitable for automotive, marine & general repair work

Soudal's technical data lists a cured hardness of approximately 75 Shore D plus a temperature resistance of approximately -30°C to +115°C.

Those figures describe the cured repair material. They don't turn Polyfiber into an elastic sealant or moving-joint compound.

Common Applications

Rust-Damaged Metal

Rust can leave a panel thin, perforated or locally weakened even after loose corrosion has been removed.

Soudal Polyfiber can be used for reinforcing rust-affected parts & repairing small holes in metal.

Preparation is critical.

Remove rust from the repair area then make sure the remaining substrate is:

► Rigid
► Clean
► Dry
► Free from dust
► Free from grease

Smooth surfaces should be rough-ground where appropriate to improve adhesion.

Polyfiber should be bonding to sound prepared material—not loose rust.

Automotive Body Repairs

Polyfiber is part of Soudal's automotive repair range & is suitable for repairing small holes & dents in car body parts.

The fibre reinforcement is particularly useful where the damaged section needs additional build & strength before the finer finishing stages.

Typical work can include:

► Body-panel damage
► Small perforations
► Rust repairs
► Dents
► Damaged metal sections
► Localised body restoration

Once the reinforced repair has cured, it can be sanded before the surface moves into finer filling, priming or painting stages.

Fibreglass & Polyester Repairs

Damage isn't limited to steel.

Soudal specifies Polyfiber for polyester & fibreglass substrates, making it useful for suitable repairs where fibre reinforcement complements the existing material.

Possible applications include:

► Fibreglass components
► Polyester panels
► Cracks
► Small holes
► Damaged edges
► Localised impact damage

Always prepare the substrate correctly & test adhesion where material compatibility is uncertain.

Boat & Surfboard Damage

Soudal also identifies larger damage on boats & surfboards among Polyfiber applications.

These jobs can involve very different constructions, coatings & exposure conditions, so the repair should be assessed as a complete system rather than assuming every boat or board surface is identical.

Confirm the substrate, remove damaged or poorly bonded material & check compatibility before beginning the repair.

Suitable Timber Repairs

Polyfiber can also be used for suitable holes & damaged areas in wood.

The substrate still needs to be rigid, dry, clean & properly prepared.

For timber work where the job is bonding pieces together rather than filling damaged material, browse Soudal Woodworking Adhesives instead.

Product Selection Guide

The most useful question isn't “Which filler is strongest?”

It's “What stage of the repair am I doing?”

Damaged Area Needs Reinforcement

This is where Soudal Polyfiber earns its place.

The glass fibres help reinforce suitable holes, dents & weakened sections while the polyester resin forms the repair body.

Repair Only Needs a Fine Cosmetic Finish

Polyfiber isn't intended to replace every finishing compound.

Soudal recommends finishing the cured Polyfiber repair with Metal Plastic or Metal Plastic Extra Fine before painting or spray painting where the repair requires a finer final surface.

Think of Polyfiber as the reinforced repair layer rather than automatically treating it as the final cosmetic skim.

Surface Is Still Rusty

Don't bury active loose corrosion under filler.

Remove the rust & prepare sound material first. Rough grinding smooth surfaces can also improve adhesion.

Damage Is in a Moving Joint

Choose a different type of product.

Polyfiber cures into a hard polyester repair compound. It isn't a flexible joint sealant intended to repeatedly stretch & compress with building movement.

For flexible sealing applications, browse Soudal Polyurethane Sealant/Adhesives.

You're Repairing Fibreglass

Polyfiber may be suitable because Soudal specifically lists polyester & fibreglass among compatible substrates.

The condition of the laminate still matters. Remove loose, contaminated or unsound material & carry out a preliminary adhesion test where required.

Mixing & Application

Polyfiber moves quickly once the hardener is mixed in, so preparation should happen before mixing starts.

Prepare the Repair Area

Remove rust, grease, dust & poorly bonded material.

The remaining surface should be rigid, clean & dry.

Roughen smooth compatible surfaces where appropriate to improve adhesion.

Mix the Two Components

Soudal specifies mixing approximately 2% B-component hardener with the A-component.

Mix thoroughly until the material is homogeneous.

Poor mixing can leave inconsistent areas within the repair.

Mix Only What You Can Apply

The approximate open time is 5 minutes at 23°C & 55% relative humidity.

Don't prepare a large batch simply because the repair itself is large.

Mix an amount you can place properly within the available working time.

Apply With a Spatula

Apply the mixed filler in a thin layer using a suitable spatula.

If additional build is required, Polyfiber can be applied in several layers rather than trying to create the entire repair in one uncontrolled mass.

Allow the Repair to Cure

Polyfiber is typically sandable after approximately 20–30 minutes, depending on ambient conditions.

Temperature, repair thickness & working conditions can affect the actual timing.

Shape & Finish the Repair

After curing, continue with the appropriate:

► Sanding
► Shaping
► Fine filling
► Surface preparation
► Painting or spray painting

A reinforced repair should be shaped for the finishing system that follows rather than treated as complete simply because the filler has hardened.

Expert Tips

Get Everything Ready Before Adding Hardener

Five minutes disappears quickly when you're still searching for a spatula.

Have the substrate prepared, tools ready & application area organised before mixing the hardener into Polyfiber.

Don't Add Extra Hardener Just to Make It Cure Faster

Use the specified mixing proportion.

Adding more hardener isn't a shortcut for poor working conditions & can interfere with the intended behaviour of the repair compound.

Grind Back to Sound Material

Filler isn't a replacement for solid substrate preparation.

Loose rust, paint, contamination or poorly bonded material underneath the repair can compromise the result regardless of how well the filler itself cures.

Use the Fibre Layer Where the Strength Is Needed

Polyfiber is a reinforced filler.

Build the repair where reinforcement is required then use the appropriate finishing material where a finer cosmetic surface is needed.

Don't Chase a Perfect Paint Finish With Coarse Reinforced Filler

Glass fibres give Polyfiber its reinforcing character, but they also mean the product has a different purpose from a fine finishing putty.

Shape the cured Polyfiber repair then move to the appropriate finishing layer before painting where required.

Watch the Temperature

Soudal specifies an application temperature of approximately 10°C to 25°C.

Working conditions affect open time & cure, so don't assume the same timing on every Australian job simply because the clock says 20 minutes.

Sand Only After the Material Has Cured Enough

Starting too early can drag or damage the repair rather than shape it cleanly.

Use the specified curing guidance as a starting point then assess the actual repair conditions.

Test Unfamiliar Materials

Soudal recommends a preliminary adhesion test.

That's particularly useful when you're dealing with an unknown coating, composite construction or previously repaired component.

Keep Dust & Skin Exposure Under Control

Grinding & sanding repair materials can create dust while the uncured two-component product has its own handling requirements.

Use the controls & protective equipment required by the current product information & Safety Data Sheet. Browse Respiratory Protection & Accessories where suitable respiratory protection is required for the task.

For practical workshop-care advice after sanding, grinding & repair work, read How To Clean Your Gear Without Ruining It.