Understanding Polyamide Hot Melt
Seeking a solution for a hard-to-bond material? Need a super-strong bond that will hold up to challenging conditions? Polyamide hot melt may be your answer.
Polyamides are able to create a strong bond between several different types of substrates, including paper, wood and metal as well as plastics like treated polypropylene and polyethylene, ABS and vinyl. Some types of polyamides can even adhere PVC, which can be difficult to bond reliably.
How do polyamides form such tight bonds? It's related to the chemical bonds that form between the polymer chains and hydrogen. These internal hydrogen bonds stay strong almost to the point where they melt. Other types of hot melt adhesives lack these strong hydrogen bonds.
In many applications, polyamide hot melts offer an ideal blend of strength, flexibility, resistance to oils and chemicals and ease of use.
When Is Polyamide Hot Melt a Good Choice?
When mechanical strength of a bond is a top consideration, polyamide hot melt is a superior choice compared to other polymers. Additional benefits include:
- Work for a wide range of temperatures. The bond polyamides form holds up to extreme temperatures -- anywhere from -76 to 266 degrees F.
- Flexible open time. Depending on which type you choose, polyamides can be open for 2 seconds to 2 minutes without impacting the bond.
- Resistant to grease and oil. They can be used in many applications, including automotive and mechanical, where they would come into contact with
- Resistant to chemicals. Mild acids and alkalis won't cause the bond to fail.
- Oxygen barrier. The dried polyamide keeps oxygen from getting through, which can be useful to protect electronics and prevent oxidation.
- Environmentally friendly. Some polyamides are made from natural materials like castor or rape seed oil and are not petroleum based.
- Reduced flammability. Some applications require adhesives that won't catch fire easily.
- Quick setting. You won't have to wait for a long time for polyamides to set or cure; they typically bond in seconds or minutes.
- No mixing required. Polyamides come ready to use.
- Low odor. Many adhesives require the use of special fume hoods to reduce odor, but polyamides are not strong smelling and can be used in both residential and industrial settings.
- Range of colors available. Polyamide glue sticks come in several colors if you need to blend the adhesive color with the substrates you're bonding.
For some manufacturing settings, these features make polyamides a great substitute for adhesives like epoxies or acrylics that usually cost more.
What Industries are Polyamides Typically Used In?
These features make polyamide hot melts especially desirable for a variety of industries. A few examples:
- Woodworking. Polyamides can fill knots and adhere wood. Furniture building is a related application where polyamide hot melts are used. For both the hobbyist and the commercial woodworker, polyamides like our 7718 Knot Filling Glue 10 Stick Packs can be used for this purpose.
- Low pressure molding. Polyamides can encapsulate sensitive electronics and protect against oxygen, debris and vibration. Overtec 5 FR Molding Resin Hot Melt Sticks are especially good for low pressure molding use.
- Automotive. Because the bonds can pass temperature tests required in the industry and they resist oil and grease, polyamides are often used in the automotive industry.
- Electrical. The low flammability and high melting point of polyamide hot melts make them popular in electrical applications.
Many other general manufacturing industries that require adhesives to work in a varied range of temperatures and form an extremely reliable mechanical bond also use polyamide hot melts. For a good general polyamide hot melt glue stick if you're not sure exactly what you need, look into Ad Tech 700 Polyamide Hot Melt.
We also carry several types of polyamide hot melts in bulk to save you money.
Are There Disadvantages of Using Polyamide Hot Melt Adhesives?
There are some drawbacks to using polyamide hot melts; these are important to consider when you're choosing the right hot melt adhesive for your application. Primarily, polyamide shouldn't be exposed to air during shipment or storage because they can absorb moisture from the atmosphere. The excess moisture can cause the adhesive to foam as it evaporates during the melting process, which can cause bubbles in the adhesive; this can weaken the bond.
Here are related issues that may keep polyamides from being the best solution for your needs.
- Many polyamides are difficult to run in a bulk tank. Most tanks won't keep out oxygen or moisture, which can impact the effectiveness of the adhesive.
- They have a shorter shelf life than other hot melt adhesives. Typically, you can only store them for 1 year before they lose effectiveness. Other hot melts can be stored indefinitely.
- They require careful storage. Containers should be foil sealed to keep air and moisture out. If you have a partially used container, you can't just casually cover it and use it later. Any resin you have remaining should be kept in an airtight container that is housed in a cool, dry space and used as soon as possible.
For applications where you will not be concerned about using a bulk tank or storing your adhesives, polyamide hot melts may work perfectly for your needs. Do note that while polyamides are less expensive than epoxies and urethanes that can form tight adhesive bonds, they will cost more than traditional EVA glue sticks.
If you have questions about the right hot melt adhesive for your application, or if you'd like to find out more about glue guns that are compatible with polyamide hot melts, contact our experts.