Is it the first time for a newly established factory to purchase hot melt adhesive? Grasp these 5 points firmly and you will never fall into the trap of defective products again

Whether it’s a newly opened or taken over from someone else’s factory, as my first purchase of hot melt adhesive, it’s indeed not as simple as just “buying glue” as I feel in daily life. If the wrong hot melt adhesive is selected, it may lead to the inability to spray the adhesive, bonding failure, and even damage to the equipment. Most of the possible problems are that the produced products are substandard and far from meeting the deliverable effect. Then how should one choose hot melt adhesive?

As a new factory or one that has just taken over, when you are purchasing hot melt adhesive for your factory, don’t rush to memorize all the theories and parameters thoroughly. In fact, it’s not necessary to understand all the theories at once. However, the following five core points are the key to determining the success or failure of your hot melt adhesive purchase. Make sure to clarify these points before signing the contract:

1. Core parameters: Viscosity and softening point
   Viscosity: It determines the fluidity of the adhesive and the difficulty of application. Should we use 2000-3000 mPas adhesive (with good fluidity and suitable for high-speed spraying) or 5000-8000 mPas adhesive (with high viscosity and strong initial adhesion)? It must be compatible with your existing equipment (gear pumps, glue sprayers). The viscosity is too high for the equipment to carry. If it’s too low, it’s prone to flowing and stringing. If you really don’t know how to express it, you can provide the supplier with your own equipment and the relevant parameters of the equipment. Then we can recommend the suitable model of hot melt adhesive for you based on your own machine.

Softening point: Affects temperature resistance. Ordinary packaging (softening point of 80-95℃) may melt and deform when placed in a car compartment in summer. High-temperature resistant applications (100℃+ softening point) are suitable for the automotive and electronics industries. Clarify the final ambient temperature for the use of your product. This is also very important. Clearly, your product needs to be used in a high-temperature environment. If you purchase one with a very low softening point, problems are bound to occur later.

2. Open time and curing time
   Open time: The longest period from when the adhesive is applied to the adherend to when it can be bonded. Manual or slow production lines take 15 to 30 seconds. The high-speed automatic line only takes 1 to 5 seconds. This must be confirmed with the supplier again and again. Under no circumstances should you buy the wrong one. It’s also best to communicate with the supplier. If you buy the wrong one, do you support the exchange? You should know that if you buy the wrong glue, there is a high probability that these situations will occur. Either the glue has dried up and won’t stick at all, or it won’t hold down and all the glue will overflow, resulting in a lot of glue being wasted. The key point is that the final result still couldn’t be adhered to. This not only failed to control the cost well but also increased the workload and raised the cost.

Curing time: How long does it take to hold the pressure after lamination before moving? A few seconds of curing is suitable for high-speed production lines. Suitable for complex-structured parts that can be cured in tens of seconds. This point is also particularly important. If your curing time is too short, it won’t work either. It needs to be perfectly matched with the debugging of your equipment assembly line to be the most suitable. Therefore, when buying hot melt adhesive, you must choose the right one. Don’t just pursue the low price, and even less should you pursue the so-called fast and dry.

Substrate matching and testing first

Be clear about what you stick: paper – paper? Paper – lamination? Non-woven fabric – plastic? Or metal – wood? Hot melt adhesives are classified into EVA type (economical, for bonding paper/non-woven fabric), polyolefin type (for bonding difficult-to-bond plastics such as PP/PE), polyamide type (high-temperature resistant, for bonding metals/nylon), and SBC type (good elasticity, for bonding non-woven fabric). Our main product here is EVA hot melt adhesive. When you purchase, it is recommended that you first buy a small sample to test. If it works well, you can purchase a large quantity and keep it in stock. There will definitely be no problem with this. If you order a few tons of goods right away and find that they do not match your own machine, it will be very troublesome to return the goods. So no matter what, It is essential to conduct a test and use it first. Only when you are satisfied should you choose to purchase in large quantities. The same glue may produce different results, even vastly different, when the equipment is changed, the environmental temperature and humidity are different, or the surface treatment of the substrate is different. When testing the glue, record: room temperature, whether the substrate has been pre-coated, and the equipment temperature setting. These tasks must be recorded manually as much as possible. Do not blindly trust your memory.

Environmental Protection and Safety Compliance

When purchasing hot melt adhesive, it is extremely important to consider its environmental protection attributes and whether it is safe and compliant. The hot melt fertilized egg itself has a 100% solid content and usually has very low VOC. However, some of them still depend on the occasion in which they are used. Generally, the requirements are different. For example, for food contact grade, the production of food boxes, paper cups and straws must have GB 4806.1 or FDA/ food grade certification. Ordinary industrial adhesives contain antioxidants and tackifying resins that may migrate, so this requirement is relatively high. However, if they are used in books, periodicals, outer packaging and other places, the requirements are different.

Then, some hot melt adhesives may have some odors or smoke. For instance, some EVA adhesives may release acetic acid or a slightly pungent smell at high temperatures. Make sure the workshop is well-ventilated and ask for the MSDS. You can purchase with confidence. If you don’t have these items, try not to buy.

Selection of suppliers

Nowadays, suppliers vary greatly in quality, including big brands, small brands, and even non-branded ones. So, how should one choose hot melt adhesives? In fact, choosing a production line that suits your needs and your production requirements is the most suitable. If you are just a small factory and all your cash flow is spent on raw materials, it would be very dangerous. Therefore, it is very important to pursue a brand that suits you. Big brands usually have higher prices. It depends on whether you can afford this cost. Also, you should not choose a brand that is too cheap. There are too many defective products. After calculation, the cost is still very high. So, you must choose a supplier that is close to your own situation. The best approach is to contact 2 to 3 more suppliers when making a purchase, buy some samples and try them out to see which one’s hot melt adhesive is suitable for your equipment and production needs. Even if you have a stable supplier, you should still leave yourself some fallback options. If one day they can’t supply the goods and you happen to have a large order to handle, and you rush to find a supplier, it will be a bit less favorable.

So no matter what the current situation of your factory is, when choosing a supplier, you must select the one that suits you best. There is no uniform standard answer. A supplier that can help you solve problems is a good supplier!