by Raffaele Tedesco

Human beings have always strongly felt the lure of open air life especially when they are forced to live in a frantic, chaotic, modern world.
However, the sun can be a danger for things and people. Actually solar radiation must be appropriately shielded to protect objects and ourselves. The sun is not only beneficial light shining on our world and making colours brighter, but it is also ultraviolet radiation, infrared rays which degrade the molecular characteristics of materials, which scorch, which cause skin cancer.
Fabrics have always been used to offer protection against solar radiations, but nowadays it is not enough for the manufactured product to have only a practical function, it should also have an ornamental function and last for a long time without any deterioration in colour, wear and tear resistance and dimensional stability.
Environmental conditions are very aggressive and textiles will have to resist:

• UV radiations
• The sun
• Frost
• Rain
• Sea salt
• Dirt
• Ozone influence
• Micro-organisms
• Polluting chemicals in the atmosphere
• Detergents

It is well-known that acrylic textiles to make awnings, beach umbrellas, boat covers, garden furnishings, car tops are superior to natural fibre like cotton or synthetic fibre like Polyester, Polypropylene or Polyethylene.
However, the above mentioned synthetic fibres sometimes come back on grounds of innovations and improvements to light stability, like Polyester, or to recycling, like Polypropylene.
Certainly fibres obtained through the extrusion of the melted polymer offer the advantage of simplicity and require less investment in spinning plants. Besides, melted polymers can be used to produce continuous filament.
Unfortunately the quality and the performance of products meant for outdoor use are not guaranteed by the simplification of the spinning process.
Therefore the acrylic fibre, and in particular Leacril Out Door HM-Eco by Montefibre, which is the result of a continuous technological development dating back to 40 years ago, is still unrivalled in this field.

Recently manufacturers have launched on the market products made of continuous filament Polyester dyed with dispersed dyestuffs and products made of staple fibre Polypropylene pigmented dyed which contain in weft yarn obtained by blending Polypropylene and Polyethylene.
Polyethylene through thermal treatment melts and makes the final product stiff improving its appearance.

The Montefibre Labs have tested the two above mentioned materials to check any improvements to well-known weak points:

• Strong absorption of the UV radiation from Polyester due to the high presence of aromatic rings causing "cutting" in the molecular weight and, as a result, a strong reduction in the tenacity and an increase in the fragility of the fibre;
• Easy permanent deformation of Polypropylene fabrics under steady load, already at 23°C, due to the low melting point of the Polypropylene (about 165°C) and the easy sliding of the molecular chains up to 15°C below zero.

Charts 1 and 2 show the behaviour of the continuous filament Polyester fabric compared to Leacril OD HM-Eco when it is exposed to artificial sunlight weathering test (ISO 105-B04).
Only after 500 hours' exposure time tenacity and elongation values fall to more than 50% for the Polyester made awning while the same properties remain unchanged for Leacril OD HM-Eco.

Charts 3 and 4 show the stress-strain curves at 23° and 70°C for awnings made of Polypropylene compared to Leacril OD HM-Eco. The elastic modulus, initial slope of the curve, is for Leacril OD HM-Eco 3 times as much as Polypropylene: with the same load the Polypropylene awning shows a deformation three times bigger than Leacril OD HM-Eco.

Creep tests, long time elongation under steady load, made on awnings by applying in the warp direction a load of 13.5 kg on a 2.5 cm wide strip, have shown a final elongation of the Polypropylene fabric three times higher than Leacril OD HM-Eco at 23°C and twice higher at 70°C.

After removing the load, after 24 hours' rest residual deformation is more limited for Leacril OD HM-Eco than Polypropylene as shown in chart 5.

The result of the above tests show the superior performances of Leacril OD HM-Eco referred to the " mechanical characteristics" of the awning fabric.
We would like also to underline another strong point for Leacril OD HM-Eco: the superior light and weathering fastness of the organic pigments in comparison with disperse dyestuffs used in the cone dyeing process of Polyester continuous filament.
What is the result of the investigation carried out?
Fabrics made of fibres recently offered like Polyester in Germany and somewhere else or Polypropylene in Austria and somewhere else are not innovative as it was already well-known.
Therefore if they weren't valid in the past they are still not valid today.
Why save money and have inferior performance and appearance ?
Nowadays the cost of the woven fabric for awnings, outdoor space covers, boat covers, car tops etc.. is only a fraction of the cost of the complex and sophisticated structures which hold up the fabric, leaving apart automatism etc.
As a consequence, choosing reliable, long lasting, high quality fabrics is an investment and means saving for the future.