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Scott Bader has added two new Crestomer grades to its structural adhesives range, which are primarily aimed at structurally bonding smaller sized FRP components and improving productivity.
Crestomer Advantage 10 in 380 ml cartridges has a 50% shorter fixture time of only 70 minutes compared with Advantage 30. Crestomer 1150PA, available in 25 kg kegs and 200 kg drums for use with dispensing equipment, has a 50% shorter fixture time of 5 hours compared with Crestomer 1152PA, which is an established grade with Lloyds, DNV and RINA marine approvals.
According to Scott Bader, switching to these new grades has benefited mid-volume OEMs such as boat and speciality vehicle builders, as well as companies providing FRP repair services, since it is possible to move assembled structures much more quickly due to the significantly shorter fixture time.
Crestomer structural adhesives are based on urethane acrylate technology. Originally developed for bonding GRP and marine ply substrates, with suitable surface preparation they can also be used to bond aluminium and stainless steel parts. All grades are said to be highly thixotropic and so do not sag during application on vertical surfaces, with good gap filling capabilities. Crestomer adhesives are reported to provide excellent adhesion in a wide variety of demanding end use applications, with bond lines maintaining high toughness, fatigue and impact strength properties under load.
The new Advantage 10 grade is now the fastest curing adhesive in Crestomer range, with a 10 minute working time and 70 minutes fixture time. It has an opaque white colour and can be used for structural bonding and gap filling up to 15 mm. Crestomer Advantage 10, like Advantage 30 (working time 30 minutes), is supplied pre-accelerated in a 380 ml co-axial cartridge which fits most standard manual or pneumatic hand guns. The cartridge format and rapid fixture time is ideal for bonding by hand in confined access areas.
According to Scott Bader, the typical maximum tensile strength achieved is 20 MPa with a tensile modulus of 920 MPa and elongation of > 85% using the BS EN ISO 527-2 test method. Lap shear bond joint strengths, tested to ISO 4587, in the case of marine ply and FRP, are limited by the weaker substrates which both fail before the Crestomer adhesive.
Crestomer 1150PA is purple/brown coloured thixotropic gel, also supplied pre-accelerated as a two part adhesive system which uses a 50:1 mix ratio by volume and weight (v/w). The recommended hardener is Butanox M50 or equivalent MEKP catalyst, added at 2% v/w. It has a working time (at 25oC) of only 50 minutes and a fixture time of 5 hours. Mechanical properties and bond strength are not compromised, with typical values of 23-26 MPa for maximum tensile strength, 1000 MPa tensile modulus and 100% elongation at break (according to BS EN ISO 572-2).
Crestomer 1150PA can be applied by hand with a spatula or from a bulk dispensing unit with a gun, and is used for bonding and gap filling applications up to 15 mm thick. The 1150PA grade is suitable for bonding ‘green’ FRP laminates, but also balsa and foam core materials, wood, and some metals. It can also be used for bonding composite diesel tanks, contour joints, and to build up damaged areas in sections of an FRP component, so is ideal for use in MRO (maintenance, repair and overhaul) applications.
“We are continuing to strategically focus on growing our Adhesives business globally for the long term,” says Jon Stowell, Global Head of Adhesives and Tooling for Scott Bader. “In addition to using our in-house R&D resources to develop new, more rapidly bonding grades of both our urethane acrylate Crestomer and primer-less MMA Crestabond adhesives ranges, we recently also made a capital investment of over £400k to add another mixer to our adhesives production facility in the UK. The additional mixer has increased production capacity by around 50%, which is needed to cope with the continued growth in sales over the last five years, and forecasted customer order levels in 2017 and beyond.”
Image provided by Scott Bader/Maverick Boat Group
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