Bonding Plastics: The Basics
From our kitchenware to our vehicles, plastic products have permeated every aspect of our lives and are integral to our day-to-day activities. There are two plastics that come up again and again as being extremely difficult to bond to. Polypropylene (PP) and Polyethylene (PE) are the two "problem children" in adhesive bonding applications everywhere. At Gluegun.com we take pride in being your go-to glue-guru. This means we have something for every application — even PE and PP.
What are Polypropylene and Polyethylene?
Polypropylene — Also Known as PP
Given its versatility and outstanding performance, polypropylene appears as a mind-boggling array of products that span just about every industry or field of interest imaginable and is rapidly becoming the preferred material of today's manufacturing processes.
Polypropylene is a thermoplastic polymer used in a wide variety of applications. Polypropylene is the second-most widely produced commodity plastic (after polyethylene) and it is often used in packaging and labeling. Make sure to check out our Complete Guide to Bonding Plastics and Plastic Glue. It is specifically beneficial in manufacturing due to its particularly durable and chemically resistant nature.
Polyethylene — Also Known as PE, HDPE or LDPE
Polyethylene is a lightweight, durable thermoplastic with a variable crystalline structure. It is one of the most widely produced plastics in the world. Polyethylene is considered a "thermoplastic" it is classified this way due to the way it responds to heat. Thermoplastic materials become liquid at their melting point. A useful attribute of thermoplastics is that they can be heated to their melting point, cooled, and reheated again without significant degradation. Instead of burning, thermoplastics like polyethylene liquefy.
Where are Polypropylene and Polyethylene Used?
Some of the most common uses of polypropylene and polyethylene are:
- Flexible and Rigid Packaging
- Fashion and Sports Industry (think tote bags and duffle bags)
- Medical Applications
- Consumer Products
- Automotive Industry
In summary, PP and PE are more sustainable plastic than their peers. It comes with plenty of structural, chemical, and physical advantages, costs very little to produce, and it is easy to find it in many aspects of everyday life.
Why are Polypropylene and Polyethylene So Difficult to Bond?
PP and PE are known for being difficult to bond due to its low surface energy. This characteristic has traditionally made it difficult for an adhesive to wet the surface and make a good bond. Instead, the adhesive has beaded up on the surfaces, rather than penetrating it.
However, advances in adhesive chemistries and surface preparation techniques have made bonding to polypropylene more possible than in the past. For example, certain surfaces can be pre-treated with techniques such as flame and plasma treatments. Additionally, new adhesive formulations are being developed that can adjust to low surface energy with or without surface preparation.
SuperTAC 500 — Hot Melt Adhesive for Difficult Substrates
The hot melt product we recommend for bonding PP and PE is Infinity Bond SuperTAC 500. SuperTAC 500 is specifically designed for bonding to Polypropylene and is a high-performance adhesive that is incredibly resistant to heat as well as working well in low temperatures. SuperTAC 500 works great in manufacturing settings such as automotive and textiles and also eliminates the need for any pre-treatment, solving a significant problem often associated with the bonding of Polypropylene.
SuperTAC 500 is a great low-cost solution for bonding difficult substrates like Polypropylene. Hot melt adhesives like SuperTAC 500 will provide a strong, non-permanent bond at an affordable cost. If you are looking for something a bit stronger we recommend MMA 500.
MMA 500 — Permanent Bonds for Polypropylene & Polyethylene
Infinity Bond MMA 500 is a permanent solution for difficult substrates. MMA 500 is a very unique two-part adhesive that bonds difficult plastics like Polyethylene (PE) and Polypropylene (PP) better than almost anything on the market. Infinity Bond MMA 500 is a 1:1 two-part adhesive that requires a cartridge gun and static mixer for dispensing.
Like most Methacrylate MMA adhesives, little to no surface prep is required before applying the MMA 500. It has a 4-5 minute open time and will create a permanent bond with chemical adhesion even to difficult plastics.
Testing for Success
Because PP and PE are so difficult we always recommend testing the adhesive with your substrate beforehand. Manufacturing can be different from product to product, success will depend on your substrates and what you are expecting from a bond. Testing the adhesive ahead of time will be the best solution to finding the best bond for your needs. Contact us today to see if you are eligible for a free sample.
We Are Here to Help
If you are interested in the benefits that Polypropylene offers in durability and chemical resistance and you are looking for the best method for bonding it, we have you covered. SuperTAC 500 offers many benefits in its ability to bond to an otherwise resistant material as well as being fast setting, non-toxic, and not needing mixing and don't forget — cost effective! MMA 500 is hands-down the best product if you need something a little stronger. MMA 500 will provide a structural bond to even the toughest substrates. Contact us today with questions about your application or your next product. We look forward to changing the way you look at polypropylene.