However, adhesive bonding is a complex chemical process influenced by external environmental conditions, making it essential to conduct thorough testing at multiple levels to maximise the value of adhesives for your specific applications. If you typically use fastener-based joining methods like screws, staples, snaps, and rivets, collaborating closely with adhesive manufacturers is essential to ensure effective solutions.

Why Transition?

There are several compelling reasons to transition from mechanical fasteners and welding to adhesives, including improvements in physical properties, performance, ease of implementation, and aesthetics.

Physical Properties: Adhesives are significantly lighter than most mechanical bonding solutions, reducing overall product weight. They eliminate the risk of rust and corrosion that commonly affect metal fasteners, and specialised adhesive formulations can dampen vibrations effectively, contributing to product longevity. Moreover, some adhesives can conduct heat or electricity, expanding their utility beyond traditional fasteners.

Bonding Performance: Adhesives provide a uniform bond across the entire surface area, unlike spot bonds created by mechanical fasteners. It can create stronger bonds with certain materials, such as plastics, composites, and glass. Some formulations specifically target low-surface-energy (LSE) materials like polypropylene. For example, a recently launched adhesive designed specifically for bonding LSE materials was launched by IPS Adhesives.

Ease of Implementation: Adhesives offer versatility, as they can bond to various materials and shapes, including irregular surfaces and complex geometries. They eliminate the need for drilling, which can weaken the bond and require additional tools, thereby streamlining the assembly process. Unlike welding, which requires skilled labour and often complex machinery, adhesives can be applied with less specialised training, reducing labour costs and the need for highly skilled workers. This is particularly advantageous in industries where skilled welders are increasingly difficult to find, and where automating welding processes with robots requires significant capital investment and ongoing resources for programming and maintenance.

Aesthetics: Adhesives do not leave visible holes, seams, or fasteners, resulting in a cleaner and more aesthetically pleasing product design.

These advantages are among the primary reasons product designers opt for adhesives over mechanical fasteners. However, each application may present unique challenges and requirements, which will become apparent through interactions with adhesive vendors and comprehensive testing.

Testing, Testing

A comprehensive testing process is crucial to fully capitalise on the benefits of transitioning to adhesives. This process typically involves the following steps, though not necessarily in this exact order:

1. Articulate Requirements: Clearly define your preliminary requirements and preferences when working with vendors. These factors could include the type of materials you need to bond, the environmental conditions the adhesive must withstand (like temperature, humidity, or chemical exposure), and any mechanical stresses (such as vibration or impact). Accurate articulation of these needs will guide the selection of appropriate adhesives.

2. Review Vendor Descriptions: Examine vendor statements about the materials their formulations will bond with, including testing results and regulatory certifications.

3. Vendor Tests of Your Samples: Collaborate with vendors to test your samples in their labs, gaining insights into how the adhesive will perform with your specific materials and conditions. The testing plan could involve testing for bond strength, durability, and resistance to environmental factors.

4. Work with Vendors for Field Testing: Conduct field tests at your site under the supervision of an expert from your vendor, a third-party consulting firm, or your staff.

5. Implement for Full Production: Once confident in the adhesive's performance, proceed with full-scale implementation in production.

6. Monitor Performance: Continuously monitor adhesive performance at vendor-recommended intervals to ensure long-term success. Regular inspections and performance evaluations will allow timely intervention before a problem becomes critical.

7. Testing Adhesive and Substrate Layers: Work closely with vendors to address challenges such as varying coatings, formulations, resins, and substrate options. Use real samples to ensure compatibility. While it may be tempting to quickly test samples, this approach can introduce risks. Ensure comprehensive testing for all potential use cases to avoid unexpected failures. Vendors may test your samples in their labs, providing valuable insights and data. However, replicating your exact process requires further testing at your site.

8. Guided Field Testing: Field tests are crucial to validate adhesive performance in real-world conditions. Ensure expert supervision to identify and rectify any issues. Pay attention to application methods, such as cartridge purging, mix ratios, gap thickness, curing times, and target bond areas. Follow vendor instructions precisely for curing times, as premature use can compromise adhesive performance.

9. Technical Modelling and Evaluation Methods: In cases where physical testing is difficult, expensive, or time-consuming, technical modelling and evaluation methods can provide valuable insights. There are tools that can simulate the performance of adhesive bonds under various conditions, allowing you to predict potential failures and optimise bonding strategies without the need for extensive physical testing. Calcbond, for example, enables the calculation of bond strength based on material properties and geometric configurations, providing a reliable estimate of adhesive performance in complex assemblies. By integrating these modelling techniques with physical testing, you can achieve a more comprehensive understanding of adhesive behaviour, reduce the need for costly prototypes, and accelerate the development process.

Conclusion

Comprehensive testing is paramount when transitioning bonding strategies, whether from mechanical fasteners or welding to adhesives, or from a poorly performing adhesive to a more suitable one. The need for thorough analysis and context matching remains vital, regardless of the transition type. Clear articulation of requirements, testing actual materials, and collaborating with vendors in the application context are essential steps. Adhesive manufacturers are eager to demonstrate the value of their products and can provide invaluable support in achieving a seamless transition to a reliable bonding strategy. This strategic shift not only improves product performance but also opens new possibilities in design and engineering. By embracing advanced adhesives and rigorous testing protocols, businesses can unlock new levels of efficiency, innovation, and customer satisfaction.

By: Thomas Race, technical director at IPS Adhesives