mixing system, such as a THINKY mixer, which can mix and degas materials in seconds to minutes in sealed containers, from volumes as small as 0.5ml to large production scales. Planetary mixers are particularly useful when mixing adhesives that do not statically mix or dispense well through a nozzle, such as a thick paste, or when mixing materials of highly different viscosities. Planetary mixers also enable mixing and bubble removal to be carried out simultaneously. The cure time of two part structural
adhesives can vary from a few minutes up to a few days. Cure takes place at room temperature, and can be sometimes accelerated with heat. While the adhesive is curing, the manufacturer will typically rack up the parts until they are ready to be passed to the next stage of the process (until they reach handling strength). Adhesives with shorter fixturing times
can improve throughput and reduce work in progress. A structural adhesive selector guide can advise on the cure time of each material, as well as its work time.
Most adhesives can be used safely very easily, due to packaging and dispensing technology
that limits the need for direct contact with the material. Once cured, adhesives pose no health and safety risk, but while uncured it is important that manufacturers follow instructions on the warning label and material safety data sheet, particularly on exposure and PPE. As with any chemical, there are health and
safety considerations relating to REACH/ROSH regulations, which can impact how the materials are handled. Users should be mindful of changes and update their risk assessments accordingly. One recent change from REACH applies to two-part PU adhesives with a total monomeric diisocyanate concentration of 0.1% — all users must be trained and certified in their handling. A positive side effect is that as health
and safety has become more of a priority for industry, manufacturers have developed less hazardous adhesives, without a reduction in performance. For example, the REACH requirement for training on diisocyanates has led to manufacturers developing polyurethane adhesives that are under the threshold of the legislation and pose a reduced health and safety risk, such as Point-One PU structural adhesives, which are based on micro-emission technology. Many manufacturers have also developed
adhesives that carry fewer hazard warnings, such as Born2Bond Structural. This two-part hybrid cyanoacrylate adhesive repositions the chemistry into the structural adhesive category, which has historically been limited by temperature resistance and overall bond strength.
Building a process for a two-part structural adhesive is a complex task, with many factors at play. Many manufacturers find success by engaging early with an adhesives partner who can supply both the materials and the application technology, and make recommendations on both process efficiency and health and safety. It can suggest relevant technologies that might overcome any challenges for each stage, and make recommendations for products that bring specific benefits. An adhesives partner can advise on how the
process could be scaled in the future, such as with dispensing multiplication or automation. A partner can also ensure an incremental improvement approach that builds up to full automation in a cost effective way.
45
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
