Is hot melt adhesive resistant to high temperatures? After curing, the finished product is not afraid of high temperatures and may not peel off

People who make books, magazines, and packaging often worry: “Is this glue resistant to high temperatures? Will it crack when books are exposed to the sun in cars or warehouses without air conditioning in summer?” Let me clarify:At room temperature, EVA hot melt adhesive sticks firmly, but it has a melting point/softening point. Continuous high temperature will soften, reduce adhesion, and in severe cases, it may carbonize, become brittle, or even peel off. It’s not just about getting hot, but don’t use it as a high-temperature resistant adhesive either. Let’s explain the boundaries clearly below for easy judgment based on the scene.

1、 Why are hot melt adhesives afraid of high temperatures (principle of EVA thermoplastic)

• Thermoplasticity determines sensitivity to temperatureEVA (ethylene vinyl acetate copolymer) is a thermoplastic material that undergoes solid-state heating, melting, cooling, and solidification. Its physical state changes with temperature, chemical properties remain unchanged, and it has a defined melting/softening point range. At room temperature (such as 15-26 ℃ in the workshop and daily storage), it is a sturdy adhesive film; Once it continues to exceed its heat resistance limit, the adhesive film will soften, the bonding force will decrease, and the adhesive will open.
• There is also an upper limit to the operating temperatureThe training materials clearly state that the viscosity and wettability of book adhesive are optimal when used at a temperature of 160-180 ℃; If the temperature is too high, it will undergo “thermal decomposition polymerization” → carbonization and become brittle. This not only indicates that the material is sensitive to high temperatures, but also reminds us not to overheat the glue pot for rush work.
• Distinguish from “melting point”The melting point is the temperature at which the product begins to melt when heated, while the heat resistance temperature is the temperature at which the cured product can withstand high environmental conditions for a long time without softening. The user asked ‘high temperature resistance’, referring to the latter – the performance of the finished product in the storage and transportation environment.

2、 Which scenarios should be cautious of high temperatures

• Summer cabin/trunk exposed to direct sunlightThe temperature inside the black car body can be much higher than the ambient temperature under direct sunlight, making it a high-risk scenario for sealing and opening of books, magazines, and cardboard boxes.
• High temperature warehouse without temperature controlEspecially for finished products on the top floor, without air conditioning, and stacked near heat sources, there is a risk of long-term high temperatures.
• Stacking near heat sourcesNext to the heating system, near the drying area, and next to the equipment cooling outlet.
• Distinguish from 2724Lecture 2724: “Choosing summer glue/winter glue (resistant to about -5 ℃~35 ℃) based on usage/storage environment” is a decision-making process for choosing glue; This article discusses how cured products will react at high temperatures and how to prevent glue cracking. It is about the heat resistance and safety of finished products, with different perspectives.

3、 What does high-temperature glue look like (how to identify)

• earlyThe spine/glue layer of the book becomes soft and sticky, and the pages can be easily opened, but the glue surface loses its rigidity.
• seriousThe adhesive layer turns brown (carbonized), becomes brittle, falls off, and shatters at the first touch.
• Distinguish between moisture and adhesive crackingHigh temperature glue opening refers to the phenomenon where the adhesive layer itself is soft and sticky; Moisture induced adhesive opening (see 2791 “Waterproof”) is often caused by the expansion and contraction of paper fibers due to water absorption, resulting in the interface opening first, and the adhesive may not necessarily be soft. First, identify which type it is, and then treat it accordingly.

4、 How to reduce the risk of high temperature

• Storage and transportation temperature controlAvoid exposing the carriage/warehouse to high temperatures, keep away from heat sources, ventilate, and control temperature; The black outer packaging should minimize exposure to sunlight and be transported with insulation/temperature control if necessary.
• Select and explain the working conditions clearlyTell the supplier whether there is a high temperature environment and how long it lasts. Sunlife books/graphics/packaging/pearl cotton glue are matched according to the scene, and there are differences in heat resistance performance,Please refer to the accompanying process card for detailsIn extreme and sustained high temperature scenarios, we will truthfully explain the boundaries of hot melt adhesive and not forcefully replace it.
• Temperature control on the machineThe temperature of the glue pot should be controlled within the recommended range (book glue 160-180 ℃), and should not exceed the temperature limit – this not only prevents heat hazards in the finished product, but also prevents the glue pot from carbonizing and becoming brittle (see 2757/2689).

Sunlife’s positioning: putting heat-resistant boundaries at the forefront

Sunlife focuses on EVA hot melt adhesive and specializes in production lines for books, graphic and text printing, packaging, and pearl cotton. If your working condition is “room temperature storage and transportation, short-term mild heating”, hot melt adhesive is usually very stable; If it is a long-term exposure of the carriage or a high-temperature warehouse without air conditioning, we will truthfully explain the upper limit of heat resistance of the hot melt adhesive and help you choose a more suitable model or add temperature control measures, without exaggerating the temperature resistance.

Frequently Asked Questions

Q: Will the book peel after being exposed to sunlight in the car for a day?

A: Short term mild heat is generally okay; But in summer, the temperature inside the car is very high due to exposure to sunlight (especially in black cars), and there is a risk of prolonged exposure. Try not to keep the finished product in the exposed car.

Q: Is it normal for the spine of a book to become soft in summer without air conditioning in the warehouse?

A: It is normal for the adhesive layer to temporarily soften at high temperatures, but it can often recover its rigidity after cooling down; But if it has already turned brown and fallen (carbonized), it means that it has been damaged due to overheating, and it needs to be checked from both storage and transportation temperature control and machine temperature control.

Q: Is there a hot melt adhesive that is not afraid of high temperatures?

A: EVA itself has an upper limit of heat resistance. When selecting the adhesive, explain the high-temperature working conditions clearly, and Sunlife will match the model according to the scene; Truthfully state the boundaries of extreme high temperature scenarios, and do not bet on “high temperature resistance” as a universal label.

The value of hot melt adhesive is that it adheres quickly and firmly to the right material, and heat resistance is one of its abilities but not its strong point. If you can’t get it on time, give Sunlife the storage and transportation conditions, and match the model and process card according to the purpose, which is more stable than relying on the three words “high temperature resistance”.