• Performance is achieved through the combination of choice of materials used in the pile and backing, manufacturing methods, dyeing technologies and a number of chemical additives which are required to achieve or enhance required performance standards such as soil and stain repellence.
• The most important aspects of performance are resistance to wear and change in appearance in any given location.
Standards and tests for carpet tiles
• There are a number of UK standards applicable to carpets - the more important ones are discussed at www.greenspec.co.uk/html/durability/carpets.html
Tests and measurements
Wearing - there is a strong correlation between wearing and the pile mass - expressed in g/m2
Resistance to exceptional wear - compression and heavy focused footfall can be simulated by a number of tests such as the Vetterman Drum Test, the Castor Chair Test and the Static Loading Test (which replicates the effect of furniture on the carpet). The tests look for pile recovery after compression and the absence of holes due to wear and the results are generally expressed in pass or fail terms.
Electrical resistance - important for carpeting around computer equipment where a build-up of static can be damaging. Resistance to static build up in synthetic piles is normally achieved by built-in permanent conductive fibre. Results are often expressed in kv ratings and/or a pass ‘walk-on test’ sometimes described as the IBM/ICL standard
Dimensional stability - resistance to dimensional variation due to the effects of water and heat conditions - is an essential attribute of carpet tiles and differentiates them, in performance terms, from sheet or broadloom carpeting. The Aachen test (BS EN 986:1995) was developed to standardise and assess the intrinsic dimensional stability of the carpet tile without the aid of adhesives.
Acoustic properties - a standard test method is available to assess this, comprising of a measurement in decibels of the noise created by a series of hammer blows on the carpet.
Volatile Organic Compounds (VOCs)
• New carpets come with characteristic smells. These smells arise from the organic compounds used in carpet materials, the underlay and backing and the adhesives used to install them.
• Carpets will create emissions particularly during their installation but these can continue over their lifetime depending on the manufacturing materials and the environment in which it is used. Some of these long-term emissions may be of concern as potential toxins such as styrene, formaldehyde and xylene which can be present and harmful at extremely low levels.
• There are differing international standards for acceptable VOC emissions but in Europe these are normally assessed by Field and Laboratory Emission Cell testing which is compliant with EN13419. The USA has an Indoor Air Qualityﬂ’Green Label’ (http://bit.ly/RIZf), scheme for compliant products which is regularly reviewed and updated as new data on toxicity is obtained and innovative analytical techniques for the detection of organic compounds at very low levels are developed.
The appearance of a carpet after use is a major contributory factor in decisions to replace prematurely. On average, carpets are replace after only 7 years. Through understanding the factors affecting longevity and careful specification, the working life can be extended.
Dyeing of carpets
Preserving the colour-fastness of a carpet after subjecting it to cleaning, sunlight and abrasion is key to avoiding its becoming drab in appearance. By identifying the correct dye and process, the visual effects of ageing can be much reduced.
There continues to be concern about pollution resulting from most dyeing processes, particularly to the rivers. Designers should check that a manufacturer’s pollution control is satisfactory.
• Most modern dyes can produce acceptable results in the short term.
• The current most advanced dyeing method is 'Solution dyeing' - which is routinely guaranteed to allow fibres to retain their colouring for many years.
- Pigment is added to yam pellets prior to extrusion
- Colouring is spread throughout the material rather than just on the surface (think beetroot v radish)
- Solution dyeing eliminates most of the concern with pollution as it eliminates the water-borne dyeing methods necessary with batch dying procedures
• The inclusion of recycled material in yarn can affect the dyeing qualities and often darker shades will contain higher recycled content than lighter options.
• Maintenance is expensive - typically 3x the cost of the initial purchase.
• A regular cleaning regime is vital to the long-term performance of a carpet
• The main tool should be a vacuum cleaner, which should include an agitator to dislodge particulate matter and dust.
• Frequent deep-cleaning should be part of the maintenance plan - omitting it will increase the likelihood of early replacement.
Treatments for appearance retention
Nylon and wool and mixtures of both are susceptible to soil and staining and need additives to improve this. Polypropylene has a natural stain repellence but does not have the wear characteristics looked for in many installations.
• Sealants are factory-applied.
• The coating of fibres with chemical sealant results in short-term protection - but the sealants wash away in the longer term as well as sometimes aggravating the soiling through entrapment.
• The most traditional sealants are based on long-chain fluoropolymers which will be banned in Europe from 2011 following concerns about possible toxicity.
• There is still no satisfying solution to long-term protection - however the long-chain fluoropolymers are being replaced by short-chain fluoropolymers which are held to be less toxic.
In certain locations and conditions, carpets will be subject to the growth of bacteria, fungus and moulds, particularly in poorly maintained areas where food particles and liquids may be spilled.
• Anti-micorbial treatments are offered as non-standard options and are usually appropriate for clinical areas or where food is served or consumed.
• Traditionally, carpets have been treated with compounds including tributyltin oxide (TBT) such as 'Ultrafresh' - but concerns in recent years about toxicity (http://bit.ly/9v1luw ) have prompted a move by some manufacturers towards substitution with less toxic alternatives.
• 'Intersept' by Interface: generally non-toxic in application - but care is needed in handling and disposal (Australian Government Dept of Health report at http://bit.ly/d0N29Z )
• 'AlphaSan' by Milliken: a recent innovation involving the use of nano-silver - which appears to be safe.
There is a migration from the alledgedly toxic Antimony trioxide commonly used as a fire retardant to Aluminium Trihydrate (Aluminium Hydroxide)
• Antimony trioxide Sb2O3 - concerns include: production of chlorides on combustion and Persistant Organic Pollutants (POPs); Antimony trioxide is listed on safety data sheets (eg http://bit.ly/aCUS3x ) as a suspected carcinogen. (ref: Sabina C. Grund, Kunibert Hanusch, Hans J. Breunig, Hans Uwe Wolf ‘Antimony and Antimony Compounds’ in Ullmann's Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim.)
• Aluminium Trihydrate (aluminium hydroxide also a common indigestion remedy) - reported as non-toxic by safety data sheets (http://bit.ly/9WTH1Z ). However extraction and processing of aluminium is very energy intensive.
Impacts of imports and transportation
• Most of the yarn and much of the carpet available in the UK is transported from overseas.
• LCA data suggests that transport energy represents relatively little of the embodied energy - most of the energy is used in extraction and processing of raw materials.
How forthcoming legislation will change the industry
REACH is a new European Union regulation concerning the Registration, Evaluation, Authorisation and restriction of Chemicals. It came into force on 1st June 2007 and replaces a number of European Directives and Regulations with a single system. The regulation will require extensive toxicity testing of some common chemicals. It is expected that up to 25% of them will be removed from the market including:
• PVC softeners (some phthalate esters)
• Chlorinated fire retardants
Not unlike any other sector of the construction industry, truth is trampled into the dust in the rush to join the environmental bandwagon. Carpet manufacturers websites and literature abound with claims about how important the environment is and how they care for it through the carpets they make. Product inventories are rich with names carrying the prefix ‘eco’ which appears to be de-rigeur throughout all industries as a way of appealing to green sensibilities. Needless-to-say, the specifier should treat each claim with a healthy scepticism.
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