How to Bond Polypropylene?

Polypropylene (PP) is a polymer that is frequently used as plastic. It has a wide range of use, from consumer items to military technologies, and is considered very adaptable.

You will find lots of materials that bond up quickly. But polypropylene is not one of them. Therefore you might often ask this question, “What may PP be bonded with?” Why is it so difficult to bind polypropylene? I’ve tried to answer these questions in this polypropylene adhesive blog for your consideration.

Why Is Polypropylene bonding so difficult?

The bonding of polypropylene is a highly challenging process. Although plastics provide numerous benefits for the user, yet one significant drawback is their exceptionally low density and hence very low surface tension, particularly when compared to metals.

Does anything stick to polypropylene?

The wetting behavior is also quite different, and polypropylene’s low surface energy and poor wettability make bonding difficult. In fact, the latter ensures liquid simply flows off instead of staying in place, especially those with high viscosities. This applies to paints and adhesives in addition to water. You can simply compare this with lotus effect.

The water drop test, incidentally, may be used to evaluate a material’s surface tension. Applying water or, alternatively, ink to the surface. It will be a low-energy outer surface if the liquid shrinks rather than totally soaking the surface.

So, the most important question now is:

purple plasma string

    What will bond polypropylene?

    Before we discuss the top strategies and advice for glue-based polypropylene bonding, there are a few things to keep in mind.

    Polypropylene is bonded by manufacturers using three major techniques.

    • Plastic welding
    • Mechanical Approach
    • Adhesives

      Let’s find out about them in detail.

      Plastic Welding

      Only two polymers can be joined together by plastic welding. For the two plastic surfaces to fuse together, they must first be heated (so they melt), clamped together, and given a proper time to dry.


      • Its execution is simple
      • It creates a solid relationship


      • It can be quite challenging to weld plastics in small places
      • Plastics might deteriorate during the welding process as well

      Mechanical Method

      It refers to securing plastics with bolts, rivets, or screws. Installing a fastener is as easy as measuring and marking the location, drilling a hole, then screwing or bolting the fastening into place.


      • It is very easy
      • Economically viable


      • Making a hole in the plastic may make it less durable


      Bonding to PP is now more effective than ever because of improvements in adhesive chemistry and surface preparation methods.

      It should be considered that choosing the best PP glue and performing the best surface pretreatment are very important.

      pink plasma thread

      What options are there for surface pretreatment?

      • Physical surface treatments
      • Chemical pretreatment
      • Mechanical pretreatment

      Physical surface treatments

      Physical surface treatment is sometimes referred to as plasma, corona, or flame treatment. It includes cleaning and chemically changing the substrate surface by exposing it to extremely energetic charges or other ionic species.

      Chemical pretreatment

      Chemical pretreatment is not a very expensive technique, but it must be done properly. It entails coating the surface of the plastic with chemicals like a primer etc.

      Mechanical pretreatment

      Mechanical pretreatment is normally a time-consuming process but not nearly as complex to execute. It entails “roughing up” the surface of the plastic.

      pink plasma thread

      Frequently Asked Questions on Polypropylene

      Here are some common questions about polypropylene.

      How to guide for bonding polypropylene with a special adhesive (step by step)

      Do you know that specific adhesives have been created to bind PP? They frequently have good adhesion, flexibility, and temperature resistance and are totally PP-based.

      Use one of the designated adhesives to bind PP successfully. Here are a few important tips for your help.

      • Always scrub the substrates’ exteriors
      • You should always use hot glue for bonding purposes. In general, stronger bonds result from hotter glue
      • Always use a high-output glue gun to ensure that a consistent amount of glue is applied
      • Quickly put the pieces together
      • Quickly compress the parts to increase the binding strength

        While bonding polypropylene, it’s crucial to apply enough adhesive at the right temperature and bring the substrates together as quickly as possible to maximize bond strength. For consistently strong bonding, it is highly advised to use a glue gun with high output and good quality.

        Note: The most crucial thing to keep in mind is to make sure the adhesive has lower surface energy than polypropylene. Any adhesive you are considering must thus have a surface energy of less than 29 mJ/m2.

        What are Different Polypropylene bonding types?

        Polypropylene is bonded by manufacturers using four important techniques.

        • Welding
        • The use of mechanical fasteners
        • Adhesives
        • Use methods to pretreat the plastics’ surface before applying glue