How to join plastics together without welding: the alternatives
How to join plastics together without welding? As people who work with plastics know, ultrasonic welding is the most common and widely used technology for joining plastic polymers together. In Italy, it is estimated that there are least 12 thousand ultrasonic welding groups, used to produce packaging, components for the automotive world and the drug industry, for the production of electronic devices, and so on. However, it should be noted that, in recent years, companies have begun to be dissatisfied with the results achieved with plastic welding: a survey conducted by MS Ultrasonic Technology Group in 2018 showed that 48% of Italian companies consider the welding process as one not performing adequately. In 2011, and therefore only 7 years before that, the dissatisfaction rate topped at 27%. So, it’s clear how useful it can be to find alternatives to join together plastics without welding: let’s have a look at the possible solutions.
The types of plastic and the study
Even before considering how to combine plastics without the need to use ultrasonic welding, it is important to note that this technology truly works only for fixing thermoplastic polymers, that is, those polymers which can be melted and shaped several times. In the case of thermosetting materials – those that cannot change shape when heated – it is necessary to identify other fastening solutions. And this is just the beginning: to find the ideal technology for plastic fastening you need to take into account several factors each time, such as the type of plastic used (PVC, PA, PS, PET, PMMA, PE, PP, POM, UF, NR, NBR, BR, PF, and so on), the flexural modulus, the rate of thermal expansion, the level of resistance to be achieved, and so on. It is, thus, clear that it is evaluating which the best solution for gluing plastics is must be done on a case-by-case basis.
How to join plastics without welding: rivets
Certainly, a common alternative to plastic welding is rivets, as riveting itself is presented as a conceptually simple method. It’s enough to drill the plastic surfaces which must be joined and then operate the riveting machine. But, be careful: the rivets ensure the sealing of the fastening only on the exact points where the rivets are actually positioned, and require drilling, affecting, in any case, the final aesthetic result. It should also be kept in mind that rivets can weaken composite fibre.
Fastening plastic without welding: bushings
In addition to rivets, it is possible to consider the use of screws and threaded or self-tapping bushings, or even expansion ones. In this case, it will be enough to have the tools necessary to make the holes required, and then tighten the bushings, keeping in mind, however, that this method has all the disadvantages already outlined for rivets.
How to join plastics without welding: structural adhesives and double-sided adhesives
When the aesthetic obstacles of rivets and bushings ought to be avoided, and higher strength is needed, when weakening composite fibre should be circumvented, when welding or brazing operations involve excessive heat, when the sealing shouldn’t add extra weight and the thickness is very minimal, when avoiding any drilling, and so on. Structural adhesives and high-performance double-sided adhesive tapes are excellent alternatives to welding in these situations. These are fastening systems for practically invisible plastics, specialized for different plastic surfaces each time. Consider, for instance 3M VHB LSE-110WF’s high-performance double-sided tape: it is an acrylic adhesive designed specifically to join plastics, great for fastening PET, ABS, PC, PIO, PVC, PU, PMMA, PVA, PS, EVA, PP, TPE, TPO and, therefore, very difficult substrates as well, without the need for any primers. And again, strength is assured indoors as well as outdoors, even between different materials. And this is just one of the possibilities to combine plastics without welding in the field of adhesives!