Innovative British paintmaker, HMG Paints of Manchester, has developed a first-class solar reflective coating for Royal Mail double-deck trailers, being built by commercial vehicle bodywork specialist, The Cartwright Group of Altrincham. Based on a specially modified version of HMG's A211 clear acrylic polyurethane paint, it incorporates special interference pigments, which permit a high transmission of natural light, while limiting levels of solar rdiation.

Applied to the clear fibreglass roofs of trailers used for distributing and sorting mail, it ensures a cooler, more comfortable working environment for staff carried inside and, unlike whitewash or other shading systems, does not reduce visibility.

HMG's Translucent Solar Reflective (TSR) modified coating was developed in partnership with Cartwright for this particular purpose, although the paint technology is equally relevant to architectural, domestic and horticultural applications, such as skylights, glass walls, conservatories and greenhouses. TSR has now been successfully applied to a fleet of 140 Royal Mail trailers, with another batch currently under construction, and has proved superior in performance and durability to conventional treatments, with an expected eight years to first maintenance.

HMG has also developed a technically-advanced thermal coating for the aluminium walls, again to counteract heat build-up, and additionally supplied all the bodywork finishing systems for these distinctive red trailers. One of the UK's leading designers and manufacturers of commercial vehicle bodywork, the Cartwright Group provides many of the country's best-known names with progressive and cost-effective transport solutions. It has developed an extensive range of double-deck trailer configurations to suit various logistical and loading configurations, at the same time enabling operators to maximise the quantity of pallets, containers and roll cages carried and reduce the number of journeys required.

Some double-deckers, like the 13.6m long, tri-axle, straightframe trailers built exclusively for Royal Mail, incorporate a hydraulically-powered moving deck for the faster loading of product. To help reduce the trailer's unladen weight and admit natural daylight, the Royal Mail double-deck trailer incorporates a lightweight GRP roof, but the operators who work inside, sorting the mail and parcels, complained that conditions were sometimes too warm, while the trailer walls also heated up in bright sunshine.

Classic shading solutions, like whitewash and absorption pigmented paint, would have removed the overhead heat element, but reduce the visible light also, so Cartwright's Paintshop Manager, Ian Teal, consulted long-term supplier HMG Paints, regarding a solution that would combine high light transmission with low solar heating.

HMG's technical department developed a formulation incorporating multi-layer interference pigments, which give a high transmission of photosynthetic active light (PAR), but a low transmission of near infrared light (NIR) to keep heat out. This was incorporated into HMG's high performance A211 acrylic polyurethane, without any other pigmentation that would compromise light transmission. The resultant modified coating is applied by spray gun, to give an even coverage, requires a wet film thickness of 40-50 microns, to deliver the desired properties, and its translucent finish has excellent durability and abrasion-resistance.

Having satisfied Cartwright's and Royal Mail's performance requirements with TSR, HMG then developed a thermal insulation paint for the trailer walls, to re-emit solar energy and prevent the metal becoming hot to the touch. A modified HMG alkyd coating, aluminium in colour, it incorporates hollow ceramic microspheres, each containing a vacuum, which create a reflective barrier against radiant energy; these reduce the amount of solar heat conducted through the metal trailer walls, at the same time minimising moisture condensation. The painted surface dries to a tightly packed layer of microspheres, which is highly resistant to corrosion, abrasion, mould and mildew.

"HMG Paints provides a good service and the support we have from their technical people is excellent," says Ian Teal. "We presented them with a technical challenge and together we arrived at innovative coatings solutions that are both cost effective and easy to apply in volume production."