From kitchenware to vehicles, plastic products have permeated every aspect of our lives and are integral to our day-to-day activities.
Because of their widespread use, manufacturers must be able to efficiently and permanently join plastic components into complete assemblies and that often means using hot melt adhesives.
Hot Melts & Their History
Traditional hot melts are thermoplastic resins. The resins are heated and applied to the substrates. Once it cools, the glue forms a strong bond that holds well under several types of conditions and remains solid at room temperature.
Although manufacturers produce a variety of hot melts, the most popular and best-performing hot melt varieties are ethyl vinyl acetate (EVA), polyamide, polyolefin, and reactive urethane. You can apply them by hand, with an industrial spray gun, by rolling, or by extruding.
Archeologists have found evidence of humans using adhesives over 6000 years ago. The ancient Egyptians used a form of glue to seal the wooden caskets of the pharaohs, but modern adhesive technology did not begin to evolve until about 100 years ago.
A Procter & Gamble (P&G) scientist invented the thermoplastic glue, today known as hot melt, in 1940. P&G scientists wanted something that would seal cereal boxes and stop them from popping open before getting to the consumer.
Manufacturers, particularly packing companies, first began the widespread use of hot melts. Eventually, hot melt technology led to the invention of plastic glue sticks, spray-on products, and various formulations targeting specific bonding for plastics.
Applications
These products have an extensive range of applications in a variety of industries, such as:
- Packaging
- Printing
- Book binding
- Taxidermy
- Textiles, including applique bonding
- Shoe manufacturing
- Wood processing
- Automotive, including interior and exterior finishing work like cushioning, headlights, taillights and wheel covers
- Electronics manufacturing
Hot Melt Additives
Hot melts do not contain water or solvent. The adhesive sets when it loses heat, so the bond literally forms within seconds after applying.
- The polymers in the adhesives provide strength and flexibility.
- Resins provide immediate tack needed for adhesive action. Wax in the adhesive thins it making it easy to apply.
- Antioxidants help protect the adhesive from losing its bonding ability even at elevated temperatures.
- Tackifiers boost the bonding strength.
- Waxes alter the surface properties and reduce the viscosity.
- Fillers, like tackifiers, also increase bond strength, as well as increasing the melting point and viscosity.
What Is Polyethylene?
Plastics can be divided into two main groups: thermoplastics and thermosets. Thermoplastics, like polyethylene (PE), soften easily when heated. Thermosets do not.
Polyethylene is the most common type of plastic used by industries today, but it was not discovered until several years after the first real plastic was invented. Chemically, polyethylene is a synthetic resin with distinctive properties that have made it an invaluable addition to modern life. It is light weight, flexible, chemical resistant, corrosion resistant, and inexpensive to make.
Why Use Hotmelt for Bonding Polyethylene Plastic
Hotmelt has a number of characteristics that make it an excellent choice to bond polyethylene plastic.
Sets Very Quickly
Unlike many other adhesives, hot melt sets quickly. This is particularly important in assembly lines and other types of manufacturing where you need to join two parts quickly and move on to the next step in assembly.
No Mixing
You don’t need to add anything or mix any components together when using hot melt to bond PE plastic. It is a standalone product that does its job without any additional compounds.
Non-Toxic
There is no need for extraordinary precautions when you use hot melt since it is nontoxic. You do not have to follow hazardous material disposal methods or worry about toxic fumes. The product will not harm your employees or consumers.
Bulk Purchasing
It is also a cost-effective method to use in your manufacturing or shipping operations. Because it sets quickly, you can maximize your manufacturing and operational speeds. You can also buy it in bulk to save you time and money.
How to Bond Polyethylene with Hot Melt
To ensure a successful bonding of polyethylene, the bonding surfaces should be dry and clean. There should not be any grease, oil, or dust contamination. The adhesive should also be applied at the appropriate temperature as the temperature of the surrounding environment and the materials involved can affect the adhesive properties. Too high of a temperature retards setting time, while too cold of a temperature results in the adhesive setting before the bonding of the materials.
Applying too much or too little can also adversely affect the bond. Insufficient quantity leads to quicker cooling of the adhesive and improper bonding. Too much adhesive prevents cooling down of the bond prior to completion of compression and leads to a weakened bond.
How to Apply Hot Melt to Polyethylene
Industrial hot melt applicators come in a variety of dispensers. There are pneumatic systems, roll coaters, hand guns, and more. These products have different settings and benefits.
For example, the Astro Packaging SS10 has a melt rate of 8lbs per hour. It’s TC500 temperature controller can handle two hoses and two applicators at a time. The 10lb tank has a cylindrical Teflon-lined drum that eliminates char buildup and helps ensure a constant pump rate.
The Astro Packaging LS10 is perfect for product assembly. Like the SS10, it has a 10lb bulk, Teflon-lined hot melt tank. Fully electric, the LS10 takes about 30-45 minutes to warm up and has a great 8lbs-per-hour melt rate. Weighing only 45lbs, it is easy to move around. It also has a built-in safety feature that will not allow the pump motor to operate until the tank reaches safe operating temperatures.
Best Products for Polyethylene Bonding
We offer several types of products highly effective for bonding polyethylene substrates:
Infinity SuperTAC 500 Glue Sticks
Offering great heat resistance and bonding abilities to a wide range of plastics including PP, PE, PET, and PVC, this product is an ideal adhesive for plastic. It’s also cost effective.
This high-performance APAO hot melt is regularly used in automotive manufacturing and product assembly. It’s bonding abilities are strong and flexible with impeccable temperature resistance at both low and high extremes. With the option of either bead or spray form dispensing and it’s flexible bond, it will give your great impact and vibration resistance.
Henkel manufactured this product specifically for plastics, metals, woods, and leathers that would be exposed to extreme temperatures. It has exceptionally high impact resistance at very low temperatures. It also has excellent shock resistance and carries a UL 94VO rating.
With its long open time, this hot melt allows you to reposition and tweak your product before the adhesive sets permanently. A general-purpose hot melt, it comes in a 35lb case. It can also be sprayable with up to nine minutes of tackiness.
Along with bonding polyethylene, this freezer-grade hot melt has approval under Food and Drug Administration (FDA) regulations for incidental contact with food products. It will also not lose its tack in freezing temperatures and is optimal for fast, short compression times.
Another great Henkel product with low viscosity, this adhesive is great for potting and encapsulating. It is heat and vibration resistance and bonds not only to plastics but also to metals. Due to its fast cure rate and quick dispensing, it makes a great alternative to an epoxy or urethanes.
Ad Tech 297 Sprayable Hot Melt
This product was made for spraying and bonding large areas made of plastic, wood, foam, metal or cardboard. It stays tacky for up to 10 minutes, so you can cover up to 48 square feet without worrying about the bond setting too soon.
Finding the Right Product for Your Polyethylene Bonding
Hot melts function effectively when used to bond polyethylene and other plastics. Because the applications for polyethylene are numerous, there are many types of formulations available for whatever needs you might have.
To get the best results, ask an experienced hot melt retailor for advice and guidance as to what sort of product and applicator will work best for your operations.
