Getting polyurea into standards and specs is one aim of industry body
By Liz White
The Polyurea Development Association - Europe (PDA-Europe) remains focussed on its original brief: to pursue the interests of the European polyurea industry, emphasised the group’s incoming president Romuald Bartczak, general manager of Belgian polyurea systems developer FlexGuard.
Bartzcak said that PDA-Europe made this decision at a board meeting in June, and issued statements to assure members that it was remaining a polyurea grouping.
That decision followed the move by the US PDA to broaden its remit and welcome into its membership “associated technologies such as as PU and hybrids, and also topcoats and primers,” as the US association’s executive director Lou Frank told the recent PDA-Europe meeting. The US group has become “PDA — The Association for high performance elastomeric technologies.”
While Frank said that the “backbone of PDA (in the US) is polyurea,” he noted that the US group is struggling with the same issues that beset the European one, such as the need to increase membership and raise funds.
PDA Europe feels no urge to follow the same route: It is “the leading organisation representing the interests of the European polyurea market,” according to Marc Broekart of Huntsman, chair of PDA-Europe’s membership committee. And, he added, “The way things are going, we might become a global one, who knows?”
Broekaert said that at the first PDA-Europe conference in Brussels in 2006, the group had 55 members. Despite the tough economy of 2008/9, PDA-Europe membership and the business itself are still growing: the association now has 85 members.
At the fifth annual meeting, held 15-16 Nov in The Hague, the Netherlands, PDA-Europe had 100 delegates from 17 countries, said outgoing president Stephan Rheindfleish of Graco.
To develop the European polyurea market, “we target everybody that is or could be working on polyurea applications, that is involved in specification setting and that is responsible for designing applications,” Broekaert noted.
Broekaert stressed that the aims of PDA Europe are to promote market awareness, understanding and acceptance of polyurea technology through education and training, product standards, application guidelines, safety and environmental recommendations.
Standards differ from the US and Europe, Broekaert noted, and PDA-Europe tries to keep in touch with standards bodies and get polyurea recognised in these. As the meeting heard, this is a central task, and a challenging one, as changing standards, directives and norms to include newer, non-traditional materials is a time consuming and difficult task.
Dudley Primeaux, one of the founder members of the US PDA, commented that the US group had never excluded people from the epoxy, polyurethane or hybrids side. But, he noted, these coatings have been around for a lot longer than polyurea, and have many associations already that serve their needs.
Meanwhile, “We in Europe will stick to our original polyurea plan,” stressed Broekaert. “Our mission is quite straightforward, and the original alliance agreement [with the US PDA when the European body was set up] was simple: pure polyurea.”
PDA-Europe is also inclusive in terms of presentations at meetings, but it is only responsible for the polyurea business, and that is where it needs to focus its efforts, he indicated.
Polyurea not for roof waterproofing only
Italian polyurea expert Gianni Farina thinks some aspects of polyurea offer the chance to use it a little differently, while noting that currently, polyurea is used very little in Italy.
Farina described a major project his company, Creazzo-based Veneziani SpA, has carried out to coat 35000-m² of composite façade panels with polyurea. The panels are being used at Milano City Life, a development being built on the site of the former Milan fairgrounds.
This project has nine buildings in four areas, designed by four different architects. Farina worked on the residential buildings designed by award-winning British-Iraqi architect Zahar Hadid, in a project involving panels made from many different elements, steel, aluminium, polyethylene — all connected together and used outside.
These panels make differential movements and Hadid demanded a solution that gave the illusion of a single panel material – but with no cracking.
The solution that Veneziani came up with was special elastic mortars to join the materials, with the panels all covered with a final layer of matt polyurea.
City Life residential areas had all the balconies coated in this way, Farina said.
Cases like this have shown the value of the polyurea, allowing “certain characteristics that you cannot get anywhere else,” Farina added.
“Most Italian specifiers have no idea about polyurea,” he commented, in a separate interview, noting that ideally, consideration of the material needs to be early in a project.
Roofs in Italy are often concrete, with a bitumen waterproofing membrane, topped with another layer of concrete. If people used polyurea, then the design could be altered and much weight saved, Farina explained.
An issue in getting polyurea accepted is, of course, that specifiers are wary of non-standard materials, he commented.
Farina said the façade project is nearly finished now, and he is working on some other façades for projects in Rome and Venice.
Italy is the home of bitumen /polymer membranes, he commented. In 2009, it made 110 million m² of waterproof bitumen membranes, and less than 400 000-m² of polyurea, so there is an opportunity there.
One area where polyurea is more efficient is for refurbishing old roofs, especially where there is a lot of equipment which any coating has to be laid around. Spraying is much simpler than laying membranes under these conditions.
Polyurea is more effective and costs less in these circumstances, Farina said.
Also for solar panels which need a 20-year life, traditional systems only last 10 years, and maintenance is very complex. Here 3-4 mm of polyurea, which lasts for 15-20 years, is an interesting option.
Farina said he would like PDA-Europe to develop a code of practice for applicators. In Italy, there are only ten well-known applicators (and maybe 10 000 for bitumen) he said. Farina’s company has signed agreements with seven applicators. As a result they get better insurance deals, of ten years duration for complete projects, with the insurance companies inspecting and auditing projects.
Farina described other Italian projects, coating bridge decks, an old sewer duct and various flooring projects – including a successful one for a winery.
Slip sliding away
In the US, a lot of water parks have slides, some a few metres long for children and some “very challenging and much longer ones,” said Bayer MaterialScience llc’s Steven Reinstadtler.
The 1990s saw many of these parks spring up, and Reinstadtler said, “Over time, the gel coat has worn with use.” The slides are starting to age and the gel coat is wearing away, leaving the composite underneath with the possibility of exposing the fibre layer. The owners are worried about their liability from any injuries this could cause, Reinstadtler explained.
Decorative gel coats can be polyester, vinyl ester, epoxy, PU and now polyurea, and are used to cover what is often a rather ugly composite surface, and give a nice finish, said Reinstadtler.
Typical uses are in Disney theme parks where there are a lot of decorative facades. Gel coats can also be used for the very big surfaces on wind turbine blades, which can be made out of epoxy/glass fibre composites, with the gel coat added as an in-mould coating.
For the slides, the park owners “need attractive repair rapidly.” They “need to take it down and put it back within hours,” and cannot do this with a traditional gelcoat, Reinstadtler commented. Also, the parks need to keep operating during application, so they want a system with no odour and low VOCs, he added.
Top coats are subjected to water, sun and chlorine, and need good colour retention despite amines and salts in the water, said Reinstadtler.
“Owners also desire less cracking,” as the inflatable tubes used as craft on these slides can cause a lot of flexing of the slide body on curves, of 2-4 percent resulting in a type of “spider-web cracking,” Reinstadtler said.
As well as ease of use, faster cure, more flexibility and low odour, applicators also need good cold-weather cure since some parks are in regions with cold winters, and that is when repairs are done, Reinstadtler said.
Reinstadtler described polyaspartic coatings as pure polyurea types, traditionally used as a thin film — applied in a single layer. They offer fast return to service and good properties.
Polyaspartic’s abrasion resistance is excellent, but it is still a very hard coating, Reinstadtler pointed out. The benefit of this for slides is that it allows the right amount of slip: softer coatings such as more traditional polyureas are not so hard, so they “gave more grip and stopped the fun,” Reinstadtler said.
On the other hand, “you don’t want to make it too fast, as that’s too dangerous, so you need balanced surface properties,” he explained.
In terms of weathering, polyaspartic systems offer very high gloss, which is retained even after 3500 hours exposure, even at high chlorine levels, Reinstadtler said.
Polyaspartics also have extremely good impact resistance, despite their low elongation. Their chemical resistance is good — not crucial in water slides, but of value in other uses.
The coatings are spray applied, and users need to form a relatively thin fllm — thinner than a typical polyurea.
Reinstadtler noted that for indoor parks which usually run all year, repairs need to be done in sections overnight, so the slide can be put back in use next day, with no interruption of service.
Polyaspartics have very desirable properties for these uses, including weatherability, less odour and VOCs, good resistance to chipping, abrasion and marring, and also fast return to service, Reinstadtler concluded.
An expensive lesson
Thick film polymer coatings are used a lot in potable water, and despite the myth that polyurea cannot be immersed in water, “I will tell you that polyurea systems properly formulated will work well in immersion situations,” said Dudley Primeax, owner of US polyurea consultancy Primeaux Associates llc.
Primeaux was talking about a potable water project in Australia. Water company Veolia decided to build the Bundamba Advanced Water Treatment Plant in Queensland, to the northeast of Brisbane, following Australia’s severe drought in the mid 2000s.
Primeaux. who has just joined US company VersaFlex as education and development director, said the Australian facility was based on micro-filtration reverse osmosis, and was designed to handle 233 million litres a day.
Initial lining work was completed in December 2007, for two tanks each of 1.9 million litres capacity, with a lining area of 900 m².
The system chosen was an aromatic based pure polyurea, for a fast-cure elastomeric thick film, applied using plural-component air-purge spray guns.
Primeaux said the project was completed in December 2007, and all seemed fine. But when Veolia filled the tanks with water in December 2008, they leaked, which was attributed to pinholes in the polyurea.
“The contractor and applicator went out to do what I call ‘cow-patty’ repairs,” Primeaux remarked. In effect, they simply wiped the surface with N-methylpyrrolidone and applied polyurea patches, he said.
Later these patches started falling off and getting caught in the pumps and then in the $2000 value reverse-osmosis equipment.
Veolia decided to shut the plant down and investigate, “which is when I got involved,” Primeaux said.
Primeaux found that the surface preparation of the concrete had been poor with the incorrect parge material used.
The surface had not been brush blasted, just dusted down with low-pressure air. In some cases, paint was still present on the concrete before coating.
The engineers considered spot repairs to the patches, but then “came to their senses,” said Primeaux and decided to completely remove the polyurea and coat the tanks again.
Removing the existing PUA liner was “actually very easy,” Primeaux said.
After abrasive blasting the concrete surface, the contractors vacuumed the concrete, before applying the neat epoxy primer by roller.
Next they applied aggregate-filled epoxy for bughole filling, and finally a 2-mm thick polyurea layer, and achieved adhesion values of better than 3.4 MPa.
Primeaux stressed that this repair work followed all the standard procedures for work methods, job safety and inspection and testing.
As Primeaux commented, this was a good project but “contractors need to follow specifications.”
Later in 2009 the plant was back in service with no leaks, providing an “expensive lesson for the contractor,” he concluded.
Multi-storey car park floors
“Why must parking decks be renewed?” asked Cees Moorman of BASF, describing a project for a high-rise parking area in a city centre, which had a bitumen waterproofing membrane that was cracked. On top of the bitumen layer was a layer of sand, with stone tiles over that.
Moorman said leaks will cause steel corrosion and that will damage the concrete. Not only does this look awful, the concrete will eventually be destroyed and the multi-storey car park will have to be demolished, he warned.
Instead of removing all the stone tiles to repair the bitumen -- a very expensive and time-consuming task, Moorman proposed a method to cover this parking deck with polyurea.
This part of the deck, total area 7500 m² had a lot of leaks in the bitumen membrane, which is located underneath the top layer of tiles.
The team cleaned the stone surface with hot water, and filled any gaps between the blocks with sand and epoxy. Then they laid a new polyurea layer on top to form a coating and oversprayed again, as a new membrane
The spraying also filled any gap between the walls and floors to provide a continuous surface.
On the fifth floor the construction was a bitumen layer on top of a concrete base, and this was also sprayed with a polyurea, with good adhesion between the bitumen and polyurea.
The 2.5 mm thick polyurea coating had: 425 percent elongation, hardness of Shore D 40, tear strength 21 N/mm².
Adhesion to the concrete was 3.5 N/mm², and to the bitumen was 2.5 N/mm².
In a discussion after his presentation, Moorman said the car park had a lot of leaks and this overspray route avoided the very high cost of removing the floor and replacing it.
One delegate noted that in Germany, the approach in such a case would be to remove all corrosion of rebars, since unless these are checked, there may be hidden problems.
Moorman replied that the contractors found all the places where there was evidence of corrosion and took the concrete off with a hammer. Where the steel was at all corroded, it was cleaned, resanded and repaired.