Hot melt EVA resin: choosing VA and melt index for adhesives and laminating

How VA and melt index set hot-melt performance

The base polymer gives a hot melt its strength, flexibility and cohesion. Tackifier and wax then tune tack, viscosity and set speed. Within EVA, two numbers do most of the work. The table shows the direction each one pushes, with other things held equal. MI values are at 190°C / 374°F, 2.16 kg.

Directions are general. Values from producer data sheets and guides for specific grades; your formula decides the final result.

Tackifier and wax compatibility

• Rosin esters. Broadly compatible with EVA across the VA range and often used for adhesion to difficult paper and board. Color and odor vary by grade, and hydrogenated types are lighter and more stable.
• Hydrocarbon resins. Aliphatic C5 resins fit lower-VA EVA best. Aromatic-modified, hydrogenated and cycloaliphatic types fit higher VA better. Check the tackifier maker's compatibility chart for the VA you run.
• Terpene and terpene-phenolic resins. Used where polar adhesion or heat resistance matters. The phenolic types suit higher-VA grades.
• Paraffin wax. The low-cost viscosity cutter and set-speed driver. One producer designs its 28% VA series for paraffin blends and its 25% VA series for formulas with more microcrystalline wax.
• Microcrystalline wax. Adds flexibility and some tack and slows set. Often paired with slightly lower-VA EVA.
• Fischer-Tropsch (FT) and polyethylene waxes. Higher melting and sharper setting, for faster set and better heat resistance in packaging hot melts.
• Cloud point. The temperature where a polymer and wax blend turns hazy as it cools. It is a quick screen of compatibility. One producer lists cloud point at 10% polymer in a refined paraffin for each grade.

Typical formula structure by application

No recipes here, just the usual building blocks. Many EVA packaging hot melts start from roughly equal parts polymer, tackifier and wax, plus a small amount of antioxidant, and are tuned from there.

Typical starting points only. Every formulator tunes ratios and grades for its own substrates, equipment and end use.

Application methods and what they need from the resin

EVA often gives moderate wash resistance in textiles. For hot washing and dry cleaning, laminators often switch to copolyamide, copolyester or TPU adhesives.

Brookfield viscosity and resin melt index

Polymer producers quote melt index, measured on the neat resin at 190°C / 374°F, 2.16 kg (ASTM D1238). Adhesive specs quote Brookfield viscosity (ASTM D3236), measured on the finished adhesive at the application temperature, often 177°C / 350°F for packaging and lower for low-temperature formulas. The two are related but not interchangeable.

• Higher MI, lower viscosity. At the same VA, a higher-MI resin gives a thinner melt. One producer lists about 20,600 mPa·s at 190°C / 374°F for a 28% VA, 400 MI grade and about 9,000 mPa·s for a 30% VA, 870 MI grade.
• Very high-flow grades. Some are stated only as melt viscosity. One 27.6% VA grade is listed at about 3,100 mPa·s at 190°C / 374°F.
• The formula dilutes the change. Wax and tackifier make up most of a packaging hot melt, so the finished viscosity moves less than the resin's MI does. It still moves.
• Measure on your formula. When you change resin, compare finished-adhesive viscosity at your pot temperature, not just the resin MI. See melt flow index explained.

Thermal stability, char and acetic acid

• Temperature ceiling. EVA breaks down with heat and time. Producers' hot-melt sheets recommend about 182–199°C / 360–390°F, or keeping the melt below about 210°C / 410°F. One says to avoid melt temperatures above 230°C / 446°F. Use the limit on your grade sheet.
• Acetic acid. Overheated EVA releases acetic acid. It smells like vinegar, corrodes tanks and hoses, and is a sign the polymer is degrading.
• Char, skin and gels. Long pot residence, hot spots and air contact cause darkening, skin on the melt surface and gel particles that clog nozzles. Keep tanks topped up with fresh material and clean them on a schedule.
• Antioxidants. Most hot-melt EVA grades carry some antioxidant, often BHT, and formulators add their own. Ask what the grade contains.
• Pot stability test. Age the adhesive at application temperature and track viscosity, color, skinning and separation over time. ASTM withdrew its heat stability method (D4499) in 2021, but many labs still test this way.
• Alternatives. Where pot stability, color and odor are the main problem, many formulators look at metallocene polyolefins. See metallocene polyolefins.

Food packaging: 21 CFR 175.105 and 177.1350

Adhesives used in food packaging fall under FDA 21 CFR 175.105. Every ingredient must be permitted in that section or another regulation, and the adhesive must be separated from food by a functional barrier or stay within limits. Dry food contact is limited to good manufacturing practice. With fatty and aqueous foods, only trace amounts at seams and laminate edges are allowed. The container label must say "food-packaging adhesive". Copolymers of ethylene and vinyl acetate are among the permitted polymers, and paraffin and FT waxes and many rosin and hydrocarbon tackifiers appear on the list, some with conditions.

The EVA resin itself is covered by 21 CFR 177.1350 when it is used in a food-contact article. That section sets no VA ceiling for plain EVA copolymers (its 11% VA cap applies only to maleic anhydride-grafted EVA) and limits chloroform-soluble extractives to 0.5 mg per square inch under test conditions set by food type and use. It also says that extractives limit does not apply to EVA used in a food-packaging adhesive that complies with 175.105. The producer states compliance for its grade. The formulator is responsible for the finished adhesive. We forward the producer's statement for the grade we supply. See resin compliance documents.

What to put on the RFQ

• Current grade. Producer and grade name from your formula sheet, if you have it.
• VA content. Nominal and the range you accept, with the method (ASTM D5594 or producer method).
• Melt index. Nominal and range at 190°C / 374°F, 2.16 kg (ASTM D1238). For very high-flow grades, add neat-resin melt viscosity if your formula depends on it.
• Application. Method, pot temperature and substrates. This tells us how close a substitute has to be.
• Additives and pellet form. Antioxidant, and whether pellet dusting or an anti-block additive is acceptable. Soft high-VA, high-MI pellets can block in a hot trailer or warehouse, so plan cool storage and first-in, first-out use. See resin shelf life.
• Documents. COA on every lot, FDA statement for the grade if the adhesive goes into food packaging, SDS.
• Quantity and packaging. Order size, yearly use and release pattern. Bags, gaylords or larger. See EVA price per pound for what moves an EVA quote.
• Sample. Ask for a sample from the lot you will receive so you can run viscosity, open time and bond tests first.

Switching between producers' grades

• Match VA and MI first. A 28% VA grade at 800 g/10 min (190°C / 374°F, 2.16 kg) from one producer and a 27.6% or 28% VA grade at 800–850 from another are often workable swaps. See 28% VA EVA grades for the MI ladder and naming.
• Then compare the details. Melting point, antioxidant, pellet additive and how the producer measures MI on high-flow grades.
• Make the adhesive and test. Brookfield viscosity at application temperature, open and set time on your substrate, bond strength, heat and cold resistance, and pot stability.
• Adjust the formula if needed. Small viscosity gaps can often be closed with wax level or by blending two MI grades in the same VA series.
• Keep the paperwork. Update the FDA statement and the spec sheet for your customers when the polymer changes.
• Plan ahead. If a grade is being discontinued or put on allocation, qualify a second source early. See when a grade is discontinued and adhesives and sealants.

Common questions

If your grade is not listed, tell us what you run. We source commodity, engineering and specialty resins.