Starting Formulation Epoxy Adhesive

A starting formulation for epoxy adhesive can vary with the application and the properties you want, but a typical two-component epoxy adhesive follows a recognisable pattern: an epoxy resin component and a hardener component, each with fillers and additives. This practical PDF guide, Starting Formulation Epoxy Adhesive, is for adhesive developers, small manufacturers, startups and entrepreneurs who want a sound base recipe to test and improve. This page walks through the logic of a starting epoxy adhesive formula, how to calculate the mix ratio, how to choose fillers and diluents, how to make, test and adjust a first batch, and how to turn it into a product.

This guide is published by Chemical Formulation Services, the formulation publishing and consultancy business of CFS Formulation Services Ltd in Sheffield, United Kingdom. It is written for people who want to understand the product from the raw material to the finished pack, and it keeps its claims practical rather than promotional.

The two-part structure

Part A, the resin component, contains the epoxy resin, reactive diluent, fillers, thixotropic agent, adhesion promoter and pigment. Part B, the hardener component, contains the amine or polyamide curing agent, accelerator, fillers and pigment of a different colour so mixing can be seen. When A and B are mixed in the right ratio, the amine hydrogens react with the epoxide groups and the adhesive cures into a tough, cross-linked solid. The art of a starting formulation is to set the ratio correctly, then tune viscosity, pot life, strength and flexibility with fillers, diluents and hardener choice.

Epoxy resin component

Epoxy resin

The main component. Liquid diglycidyl ether of bisphenol A (DGEBA) with an epoxy equivalent weight (EEW) of about 185 to 195 is the standard. Bisphenol F resins reduce viscosity and crystallisation. Solid resins, when dissolved or blended, increase tack and heat resistance.

Reactive diluent

Butyl glycidyl ether, C12-C14 alkyl glycidyl ether, or similar, at 5 to 15 parts per hundred of resin, lowers viscosity so the adhesive can be mixed and applied. Too much reduces strength and heat resistance.

Fillers

Calcium carbonate, talc, silica flour, aluminium powder, mica or glass fibre adjust paste consistency, shrinkage, thermal behaviour and cost. A typical starting load is 20 to 60 parts per hundred of resin.

Thixotropic agent

Fumed silica at 2 to 5 parts to prevent sagging on vertical or overhead joints and to stop fillers from settling.

Adhesion promoters and pigments

Epoxy silane at 0.5 to 1 part to improve bonding to glass and metals, and pigment paste for colour.

Hardener component

Hardener

The choice sets the pot life, cure speed, flexibility and chemical resistance. Aliphatic amines like triethylenetetramine (TETA) cure fast with a short pot life and high exotherm. Polyamidoamines cure more slowly, give better flexibility and lower toxicity. Cycloaliphatic amines give improved colour and chemical resistance. Mannich bases and phenalkamines cure at low temperature and in damp conditions.

Accelerator

Tertiary amines such as DMP-30 (2,4,6-tris(dimethylaminomethyl)phenol), small amounts of 1 to 5 parts, or phenolic compounds, shorten gel time.

Fillers and thixotrope in part B

Matching filler content in both parts makes the paste consistency of A and B similar, which makes mixing easier and the ratio simple (such as 1:1 by volume).

Scaling from lab to production

A starting formula proves chemistry; production proves discipline. Moving from 200-gram lab batches to 50 or 500-kilogram batches changes mixing, heating and air entrainment. Use a planetary or dual-axis mixer with vacuum for Part A and Part B, add fillers in steps while watching temperature, and keep a constant mixing time and speed for each batch. Use dry fillers, because moisture from calcium carbonate or talc causes bubbles and can interfere with cure. Fill syringes and cartridges on a controlled line that delivers the right volume ratio, and check the ratio by weighing sample pairs every hour. Retain samples from every batch for comparison if customers report problems.

Packaging format and ratio choices

Packaging drives the choice of ratio. Twin syringes and dual cartridges usually need simple volume ratios of 1:1 or 2:1, so formulators adjust fillers and diluents until the weights give the right volume. Larger kits sold by weight can use ratios like 100:50 or 4:1. Separate tubs allow wider ratios but demand scales or measuring cups. Match ratio and packaging to the user: hobbyists want 1:1 and syringes; workshops can handle 2:1 or weight-based kits; industrial users want pumps and metering equipment with precisely controlled ratios.

Documentation and customer instructions

A clear data sheet turns a recipe into a product. Include working time and cure time at several temperatures, mixing instructions, surface preparation, bond strength on common materials, temperature range, chemical resistance and storage advice. Add simple warnings, such as wearing gloves and avoiding contact with eyes, and an expiry date. Photographs showing correct mixing and application reduce errors. Good documentation reduces complaints and builds the reputation of a small brand quickly.

What is inside the Starting Formulation Epoxy Adhesive guide

The guide states that a starting formulation for epoxy adhesive can vary depending on the specific application and desired properties, and presents a starting formulation for a typical two-component epoxy adhesive, beginning with the epoxy resin component and noting that the main component is the epoxy resin, typically derived from bisphenol A. It continues with hardener choice, ratios, mixing and testing.

Calculating the mix ratio

The stoichiometric ratio is based on the amine hydrogen equivalent weight (AHEW) of the hardener and the epoxy equivalent weight (EEW) of the resin. Parts of hardener per hundred parts of resin (phr) equals AHEW divided by EEW, times 100. For example, with a resin of EEW 190 and TETA with AHEW 24.4, phr = 24.4 ÷ 190 × 100 = about 12.8 parts of hardener per 100 parts of resin. With a polyamidoamine of AHEW about 100, phr = 100 ÷ 190 × 100 = about 53 parts. Adding reactive diluent changes the effective EEW of the resin side, so recalculate using the blend’s EEW. Practical formulators then adjust slightly, usually within 90 to 105 percent of stoichiometric, to fine-tune flexibility and cure. If the target is a convenient volume ratio, such as 1:1 or 2:1, dilute the hardener with inert fillers or non-reactive plasticiser to bring the weight and volume ratio to a simple value.

A sample starting recipe (by weight)

• Part A: 100 parts liquid DGEBA resin (EEW 190), 10 parts reactive diluent, 40 parts calcium carbonate, 3 parts fumed silica, 1 part epoxy silane.
• Part B: 55 parts polyamidoamine hardener (AHEW 100), 3 parts DMP-30, 40 parts calcium carbonate, 3 parts fumed silica.

This is only a starting point. Adjust the hardener based on the true EEW of the A side after adding diluent, and test for pot life, cure and strength. Different resins, fillers and hardeners may require different amounts.

Making a first batch

Step 1: Weigh carefully

Use a scale with 0.1 gram accuracy. Weigh Part A components into one container and Part B components into another.

Step 2: Mix each part

Mix resin, diluent and silane, then add fillers in portions and fumed silica last. Use a high-speed disperser or planetary mixer. Mix under vacuum if possible to remove air. Do the same for Part B.

Step 3: Check consistency

Both parts should be smooth pastes of similar consistency, free of lumps.

Step 4: Test mix

Combine small amounts of A and B in the chosen ratio, mix thoroughly for at least a minute, and record pot life, gel time and cure behaviour at room temperature.

Step 5: Bond test pieces

Apply to clean, abraded metal strips, overlap them by a known area, clamp, cure for 24 hours and then 7 days, and test lap shear strength.

Tuning the formula

• Longer pot life: use polyamidoamine, reduce accelerator, smaller batch size.
• Faster cure: use aliphatic amine or add accelerator, warm the work area.
• Lower viscosity: add diluent or reduce filler.
• Flexibility: use polyamide hardener or add flexibiliser.
• Heat resistance: add some novolac resin and use cycloaliphatic amine, with post-cure.
• Water resistance: use Mannich base or phenalkamine hardener and hydrophobic fillers.
• Gap filling: increase fillers and thixotrope.

Testing and quality control

• Viscosity of Part A and Part B.
• Mix ratio accuracy.
• Gel time and pot life at set temperature.
• Hardness (Shore D) and cure progression.
• Lap shear strength on aluminium and steel.
• Peel and impact strength.
• Water and chemical resistance.
• Shelf life of each part.

Troubleshooting

Sticky or soft cure

Wrong ratio, poor mixing or cold temperature. Check calculation and mixing technique.

Weak bond

Poor surface preparation. Clean, abrade and degrease thoroughly.

Bubbles in cured glue

Air from mixing or moisture. Mix slowly, de-gas and keep dry.

Parts separate in the pack

Filler settling. Add more fumed silica or better filler.

Too brittle

Over-crosslinked system. Use flexible hardener or add flexibiliser.

Hardener turns white or cloudy

Amine blush from carbon dioxide and humidity. Keep containers closed.

Safety and regulation

Epoxy resins and amine hardeners are skin sensitisers and irritants, and amines are corrosive. Wear nitrile gloves, eye protection and good ventilation. Avoid skin contact, since sensitisation can be permanent. Label products with hazard pictograms, supply safety data sheets and follow chemical regulations. Do not claim food contact safety or waterproofing beyond tested performance. Dispose of unmixed parts as chemical waste and only dispose of mixed adhesives after curing.

Packaging and business opportunity

Twin syringes of 10 to 50 millilitres for households, tubes and tins for workshops, and bulk kits for industry. Customers include repair shops, hobbyists, boat and car owners, plumbers, model makers and small manufacturers. Offer a quick-set grade, a standard grade and a long working time grade with colour-coded labels. Private-label supply to hardware chains and online brands is common. Clear instructions, bond strength charts and surface preparation advice help customers succeed.

Explore related guides in the Industrial Adhesive Formulations, Resin Manufacturing, Construction Chemicals and Plastics Products categories, and see Room Temperature Epoxy Adhesive Formulation, , Epoxy-anhydride Adhesive Formula, , and Clear Epoxy Resin Formulation.

Getting started

Choose a standard DGEBA resin and a polyamidoamine hardener. Calculate the ratio, make a 200-gram test batch of each part, and bond aluminium test strips. Measure pot life, cure time and lap shear strength, adjust fillers and diluent, and document the final recipe. Then scale up and prepare packaging and labels.

How to get the best results from this guide

Treat the guide as a tested starting point rather than a finished factory. Begin with a small trial batch in the laboratory or on a bench, using the exact raw materials you plan to buy, and record every weight, temperature, mixing time and observation. Compare the result with the quality checks in the guide, change only one thing at a time, and keep a note of what each change did. Once a small batch is consistently good, repeat it several times, then scale up in stages, because mixing, heating and cooling behave differently in larger vessels. Keep retained samples of every batch, write simple standard operating procedures for your team, and build relationships with two suppliers for each key raw material. Finally, check the labelling, safety and product rules in the country where you will sell, and ask a qualified person to review your process. This careful, documented approach is what turns a good formulation into a reliable product and a trusted brand.

Who should buy this guide?

The guide is written for practical readers. It suits manufacturers who want to add a new product to an existing plant, startups choosing their first product, private-label brands that need to understand what they are buying, technical staff who must set specifications and train operators, and consultants and students who want a structured, plain-language reference. It is less suitable for anyone looking for a quick shortcut or a guarantee, because every formulation still needs testing with your own materials, equipment and local rules. If you are unsure whether it matches your project, send a short question through the contact page before you order, and we will tell you honestly whether it fits.

What is inside the Starting Formulation Epoxy Adhesive guide

Every Product Making Guide in our shop follows the same structure so you know where to look. This guide includes the product formula, the ingredients and materials, the procedure and preparations, the industrial requirements and the technical specifications. In practice you receive:

1. The formulation, written so you can follow it at the bench and scale it up.
2. Ingredients and materials, with the job of each material and advice on grades and suppliers.
3. The manufacturing procedure, including order of addition, mixing and preparations.
4. Industrial requirements, covering equipment, space and packaging.
5. Technical specifications, describing what a good finished product should look like and how it should behave.
6. Troubleshooting for the faults that makers meet most often.
7. Business guidance, to help you take the product from the bench to the market.

These Product Making Guides of chemical formulations and formulas are for manufacturers, startups and entrepreneurs. Every guide contains industrially tested, practical formulations. Anyone who buys a guide can make the product by following its step-by-step instructions. Raw materials vary between suppliers, so always confirm your results with a small trial batch before scaling up.

Who stands behind this guide?

Chemical Formulation Services is the trading name of CFS Formulation Services Ltd, registered in England and Wales under company number 16678503, with its office at Unit F, Winston Business Park, Churchill Way, Sheffield S35 2PS. The business was founded by George Enrick and publishes formulation manuals, technical guides and industry reports. You can check our details on the Companies House register, read about us, or contact us with any question before you order.

A written formulation cannot replace testing with your own raw materials, equipment and climate, and we say so plainly. What the guide does give you is a tested, structured starting point that can save you months of trial and error. Our terms and conditions explain what a purchase from us covers.

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Frequently asked questions about starting formulation epoxy adhesive

What is the Starting Formulation Epoxy Adhesive guide?

It is a digital PDF Product Making Guide to building a two-part epoxy adhesive from a base recipe, including mix ratio calculation, fillers, hardeners, testing and tuning.

How do you calculate the epoxy hardener ratio?

Parts of hardener per 100 parts resin equals the amine hydrogen equivalent weight divided by the epoxy equivalent weight, times 100.

Why add fumed silica?

It prevents sagging and filler settling by giving thixotropic behaviour.

How can pot life be extended?

Use a slower hardener such as polyamidoamine and reduce accelerator.

What causes amine blush?

Carbon dioxide and moisture reacting with amine on the surface. Keep containers closed and cure in dry air.

How do I receive the guide?

You receive an instant PDF download after payment is confirmed. For money exchanges, email your payment slip to Info@chemicalformulationservices.com and the link is emailed after we confirm it.

Is the payment refundable?

All payments are nonrefundable because the product is an instant digital download. See the refund policy for details.

Can you help with a custom formulation?

CFS Formulation Services Ltd offers formulation and product development consultancy. Send a short brief through the Contact page.

Last reviewed: November 2026. This page is general information about a digital product. It is not a safety data sheet or professional advice, and any formulation should be tested and reviewed by a qualified person before commercial use.