SHAPE FORMING
Microcapsules released by damage
corrosion resistance must leverage some self-healing functionality. Autonomic Materials (AMI) has been researching additives that impart self-healing functionality into protective coatings. These additives are comprised of
microencapsulated healing agents that incorporate polymer precursors, adhesion promoters and corrosion inhibitors. When coatings incorporating these additives are damaged, the microcapsules are ruptured, releasing the healing agent into the site of damage where it polymerises sealing off the damage and restoring the coating’s protective function. Using this approach, AMI has designed additives that have demonstrated the ability to facilitate a reduction in corrosion creep in damaged coatings based on a broad range of chemistries.
FINDING WATERBORNE SOLUTIONS
One game-changing application for AMI’s self-healing technology is the design of high-performance waterborne protective coatings. Industrial waterborne coatings have traditionally exhibited inferior corrosion resistance relative to solventborne versions. However, global regulatory trends limiting the amount of volatile organic compounds (VOCs) in coatings have led to an increase in demand for higher performing industrial waterborne coatings. AMI has demonstrated an epoxy waterborne coating with corrosion resistance surpassing many solventborne coatings while exhibiting a VOC component of less than 50g/L. To demonstrate the benefits of the self-healing functionality in the formulated epoxy waterborne coating, the corrosion performance of a control system excluding the self-healing
Keep your materials in better shape for longer with lower VOCs
functionality, but otherwise identical to the self-healing version was compared to a system incorporating the self-healing low VOC waterborne coating formulation. For both control and self-healing
systems, two coats of the waterborne epoxy were applied at 60-70 microns each to blasted steel panels (SSPC- SP10) followed by a waterborne acrylic top coat, which was also applied at 60-70 microns. After curing at room temperature for a minimum of seven days, panels coated with control and self-healing systems were scribed using 156 micron and 500 micron scribe tools. The samples were then allowed to equilibrate at room temperature for 24 hours followed by exposure to a salt fog (ASTM B1175) for 2,000 hours.
THE RESULTS After 2,000 hours of salt fog exposure, the extent of creep from the scribes were evaluated as described in ASTM 1654.6. The results showed that while the control exhibited average creep
values of 14.2mm and 10.9mm for the 156 micron and 500 micron scribes respectively, the incorporation of the self-healing additive resulted in a reduction in scribe creep of 77% to a value of 3.3mm and 69% to a value of 3.4mm for the 156 micron and 500 micron scribes respectively. Such minimal creep following 2,000 hours of salt fog exposure is rare among the best solventborne coatings and unprecedented for waterborne formulations. Within the context of transportation coating applications, the self- healing epoxy formulation affords three main benefits. Firstly, there’s no trade-off between performance and environmental friendliness, the self-healing coating formulation exhibited more efficient protection of metal substrates relative to many incumbent solventborne coatings while incorporating substantially lower VOCs. Secondly, as there’s almost no odour
and multiple components are not being mixed on site, application is easier. Finally, the formulation offers
multiple avenues for cost savings including longer lasting protection leading to lower maintenance costs, shorter application time for multiple coats due to rapid-drying kinetics; and the elimination of the need to manage solvent waste streams, all important considerations for the transport industry. ●
Scribe test results after 2,000 hours
See
www.autonomicmaterials.com to sign up to the newsletter
www.engineerlive.com 39
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
