Resin Basics: Chemistry and Types

Polymer Families
Pipe relining resins generally fall into three major categories: polyester, vinyl ester, and epoxy. Each type offers unique advantages in terms of chemical resistance, curing times, mechanical strength, and ease of use. However, Epoxy resins generally sit at the top of the list in terms of strength and safety of use:

• Silicate Resins: Can be used with fiberglass sheet for installations outside of domestic use. Although a cheap alternative, this resin is not compatible with traditional felt liners and coatings.
• Polyester Resins: Often used for cost-sensitive projects, polyesters cure relatively quickly and can handle moderate chemical exposures. However, they can be more sensitive to temperature fluctuations and might emit stronger odours due to styrene content.
• Vinyl Ester Resins: Known for excellent chemical resistance—particularly against acids and solvents—vinyl esters bridge the gap between polyester and epoxy. They cure quickly but can be more expensive than polyester systems.
• Epoxy Resins: Often considered the gold standard in pipe relining for their adhesion, zero shrinkage, and superior structural integrity. Epoxies offer excellent bonding to various substrates (cast iron, PVC, earthenware, etc.) and display high tensile and flexural strength once cured.

Resin-Hardener Reaction
Regardless of the polymer family, the resin and hardener (also called a curing agent) undergo an exothermic (heat-producing) chemical reaction. In epoxy systems, for instance, the reaction forms a rigid crosslinked polymer network. This network transforms the resin from a viscous liquid into a solid matrix, reinforcing the structural integrity of the host pipe.

Temperature and Cure Times
Temperature is one of the most critical factors in resin curing:

• Ambient Temperature: Higher ambient temperatures can accelerate the reaction, reducing “pot life” (the workable time before the mix becomes unworkable). In colder conditions, curing slows down significantly.
• Hot Water or Steam Curing: Some relining methods involve circulating hot water or steam to speed up curing, achieving faster turnaround times but requiring precise temperature control.

Mix Ratios
The resin-to-hardener ratio must be precise.

• Under-Curing: Too little hardener can prevent the resin from fully polymerising, leading to a sticky, weak liner.
• Over-Curing: Too much hardener can create excessive heat, causing the resin to cure prematurely or unevenly, and potentially weakening the final product.

Resin Viscosity and Wet-Out
Viscosity determines how easily the resin can saturate (or “wet out”) the liner. If the resin is too thick, it may not fully penetrate the fibres; too thin, and it can drain from the liner before installation. Proper wet-out ensures a homogenous bond within the fibre matrix, a key factor in the liner’s tensile strength and flexibility.

Chemical and Abrasion Resistance
In sewer or stormwater applications, liners may encounter aggressive chemicals (from industrial run-off) and abrasive flows (like sand or debris). Epoxy-based formulations typically excel in chemical resistance, while vinyl ester resins can handle more extreme pH environments. Polyester resins are sufficient for many domestic or light commercial pipes but may degrade faster under harsh conditions.

At No-Dig Depot, our EVOLiNE resin system strikes a balance between manageable work times, strong mechanical properties, and excellent chemical resistance. We’ve optimised it for:

• Zero Shrinkage: Minimises risk of cracks or detachment post-cure.
• Optimised Cure Profiles: Available in different formulations to suit typical Australian temperatures and humidity levels.
• Superior Adhesion: Bonds effectively with multiple substrates (clay, concrete, PVC, cast iron), ensuring a consistent structural upgrade.

Our EVOLiNE range is designed to integrate seamlessly with our EVOLiNE liners, allowing your crew to rely on a complete, compatible system—from the materials used to the curing process itself.

Until recently, calculating the right amounts of resin and hardener could be cumbersome, with project managers often relying on manual formulas prone to errors. Our EVOLiNE Resin Calculator* helps solve that problem by providing instant, accurate estimates.

1. Select Liner Type
   Choose from our EVOLiNE liner options. Each liner has its own thickness, fibre density, and resin absorption characteristics.
2. Select Size
   Specify the liner diameter to account for volumetric differences in resin requirement.
3. Enter Total Metres
   Input the linear metres of liner you plan to impregnate.
4. Click “Calculate”
   Instantly receive recommended quantities of base resin and hardener. This eliminates guesswork, ensuring you won’t waste time or resources.

Benefits of the Calculator:

• Precision: Accurately determines resin/hardener ratios based on liner specifics.
• Time Savings: Reduces manual calculations and potential ordering mistakes.
• Cost Control: Decreases the likelihood of surplus materials.
• Reliability: Consistent ratios help maintain uniform curing properties across your project.

*The results provided by this calculator are estimates based on the data entered. While the tool is designed to give accurate calculations, it is important to note that actual material requirements may vary based on factors such as the environment, application method, and material quality. Always consult with product data sheets to confirm your exact material needs before proceeding with your project.

Thorough Cleaning
Use high-pressure hydro-jetting to remove grease, debris, and roots. A clean pipe interior ensures the resin can form a robust bond without residual contaminants.

Quality Control Checks

• Measure Ambient Conditions: Track temperature and humidity to decide if you need a fast- or slow-curing formulation.
• Mix Carefully: Mix resin and hardener thoroughly following the recommended ratios. Partial mixing can lead to soft spots in the cured liner.

Leak Testing
Once the liner has cured, consider a pressure or leak test to confirm structural integrity. This step ensures that the newly relined pipe meets performance standards before restoring full service.

Common Challenges and How to Overcome Them

• Premature Gelation: If the temperature is too high or the mix ratio is off, the resin can begin curing before it’s fully impregnated or positioned. Mitigation: Keep resin in a cool area and use a slower-curing hardener in warmer conditions.
• Inadequate Cure: Low temperatures or insufficient hardener can result in under-cured liners. Mitigation: Use heat (hot water, steam) or faster-curing catalysts; verify ratios carefully.
• Resin Drainage: If the resin is too low in viscosity or the liner sits for too long, resin may pool at the bottom. Mitigation: Work efficiently, and choose the right liner material for the right job.

Conclusion

Resins are at the core of any trenchless relining project, providing the structure and durability that enable pipes to withstand the demands of modern infrastructure. By choosing the right formulation—and using accurate tools like the EVOLiNE Resin Calculator—you can minimise the risk of failures, reduce material waste, and streamline your crew’s workflow.

At No-Dig Depot, we take pride in supplying the industry with advanced, user-friendly solutions. Our EVOLiNE resin and liner systems are engineered for high performance, and our online calculator takes the hassle out of mixing and measurement. With the right preparation, expert knowledge, and precise ratios, you’ll be well on your way to delivering reliable, long-lasting relining projects.

Ready to see how much resin you need for your next job?
Visit our website to try out the EVOLiNE Resin Calculator and experience a more efficient way to plan your trenchless relining projects. For further guidance on resin selection, equipment, or best practices, contact the No-Dig Depot team—your partner in quality, trenchless solutions.