What is polypropylene?
Polypropylene (PP) is a lightweight, tough thermoplastic widely used for industrial applications. Polypropylene is valued for its excellent chemical resistance, low moisture absorption, high fatigue resistance and cost effectiveness, making it ideal for demanding applications.
Challenges with bonding polypropylene.
Bonding polypropylene presents a unique challenge due to its low surface energy, which prevents most adhesives from properly wetting the surface. As a result, polypropylene has traditionally been considered difficult or impossible to bond in many applications. Manufacturers and fabricators have therefore relied on mechanical fastening methods such as rivets, hardware, ultrasonic welding, plastic welding and snap fits.
While these methods can be effective, they come with clear trade-offs. They are time consuming to design and assemble, add bulk and weight to finished parts, increase labour and tooling costs, introduce visible hardware and can create localised stress points that lead to fatigue or cracking over time.
NEXTITE has developed industrial adhesive solutions specifically engineered to bond polypropylene to itself and dissimilar substrates. With the correct surface preparation, polypropylene can be reliably bonded using advanced industrial adhesives such as methacrylates or cyanoacrylates (in combination with a primer).
Adhesive selection is application specific and depends on factors including bond strength, cure speed, environmental and chemical exposure, flexibility and impact resistance.
Which adhesives can bond polypropylene?
Methacrylates (MMA) – NEXTITE AB206
NEXTITE AB206 is a two-part methyl methacrylate adhesive designed to structurally bond hard-to-glue plastics like polypropylene and polyethylene without primers and minimal surface preparation. It delivers strong, chemical-resistant bonds to polyolefin’s, other plastics, metals and composites. Making it ideal for automotive, plastic assembly and industrial applications it is also ideal for bonding dissimilar surfaces.
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Strengths |
Structural adhesive, multi material bonding, toughened, some gap filling, widely used in industry manufacturing and repair work, good chemical resistance |
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Limitations |
Long cure time, not best for aesthetic bonding although possible |
Instant Adhesives (Cyanoacrylates) – NEXTITE SP901 Polyolefin Primer + Various NEXTITE Instant Adhesives
NEXTITE SP 901 is a surface primer for making polyolefins and other low surface energy materials suitable for bonding with NEXTITE Instant Adhesives. It is suitable to prime the notoriously difficult to bond surfaces such as polyethylene, polypropylene and polytetrafluoroethylene (PTFE). NEXTITE SP 901 works well with all our cyanoacrylate adhesives especially the faster fixture time ones.
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Strengths |
Fast fixture, high shear strength, no mixing (single part), high strength even on small bond areas, aesthetic bond line possible |
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Limitations |
Limited gap filling capacity <0.15mm, Low peel strength, Low Impact Strength |
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Most Suitable |
NEXTITE 501 and 506 surface insensitive, fast curing variants provide the best results. Although, all NEXTITE Instant Adhesives can be used with NEXTITE SP901. |
What Industries is polypropylene used in?
In manufacturing, polypropylene is widely used for its toughness and chemical resistance. It is lightweight, durable and fatigue resistant, making it suitable for demanding industrial environments. Polypropylene can be cut, machined and thermoformed; however bonding PP requires specialised industrial adhesives due to its low surface energy.
Common uses of material
- Polypropylene is used in many applications including:
- Automotive components
- Industrial tanks, ducting and piping systems
- Medical and laboratory equipment
- Consumer products
Challenges with this material
- Very low surface energy, making it difficult to bond
- Requires surface treatment
- Limited adhesive options compared to higher surface energy plastics
- Adhesive selection is critical for long term durability
Properties of Polypropylene
- Surface Energy: 29 mJ / m²
- Temperature Resistance: -20°C to 85°C
- Softening Point: 110°C
Surface Preparation
Proper surface preparation is critical to achieving a strong and reliable bond when working with polypropylene. Begin by lightly wiping the bonding area with NEXTITE PROPREP Surface Preparation Cleaner. This removes surface contaminants including dust, oils and residual adhesive that can interfere with bond strength. Allow the cleaner to fully evaporate before applying any adhesive or primer.
Summary
Choosing the best industrial adhesive to bond polypropylene comes down to understanding the application requirements and performance required from the joint.
If you would like to speak to our expert team about your next project, please contact us for tailored advice and product recommendations to suit your application.