Advances in Carpet Manufacture

K K Goswami

• Publisher: Woodhead Publishing
• Year: 2017
• ISBN:
  9780081018880
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Advances in Carpet Manufacture, Second Edition, discusses the manufacture of carpets, an industry that has evolved over hundreds of years, also exploring the new changes and developments in textile science and manufacturing technology that occur every day. This updated edition provides revised, expanded and updated coverage of carpet manufacturing processes and applications.

The book begins by reviewing the different types of carpets and their applications, also exploring the structure and properties of carpet materials. Carpet manufacturing techniques are then reviewed, including a new chapter on tufting and yarn manufacturing techniques, and design and manufacture for handmade carpets. Subsequent chapters review the development of carpets with important properties, including new chapters on carpets for acoustics and sound absorption, carpets with increased fire retardancy and those with antimicrobial and soil-resist finishes.

With the variety of topics covered and its international team of contributors, the book offers a valuable and informative reference for technologists in the carpet and associated industries. However, it is also a great resource for researchers and students working in applied textile sciences.

• Presented by an expert editor with many years of experience in both academic textile research and industry
• Provides new research, technologies and other developments in carpet manufacture for academics and developers seeking to update their knowledge
• Includes a strong focus on industry needs and developing areas with market potential

1

Carpet types and requirements

D. Whitefoot CText, FTI, UK

Abstract

This chapter reviews the history of textile floor coverings from prehistoric times up until the present day. It is based almost exclusively upon hands-on experience gained over a working life of 50 years in the carpet industry, rather than being culled from publications. Brief descriptions are included of the main carpet manufacturing processes and of the raw materials used. The subject matter relates in particular to the UK carpet industry but differences in the characteristics of carpets produced in other centres, particularly the USA and continental Europe, are discussed. A tentative glimpse of the future is also the subject of brief speculation.

Keywords

Axminster; Wilton; tufted; wool; cotton; jute; polyamide; polyester; polypropylene; thermal insulation; acoustic insulation; carpet properties; impact upon human health

1.1 The role of textiles in floor coverings

Historically, the first floor coverings were probably animal skins and the earliest floor coverings of textile construction were probably crudely woven textiles made from rushes or grasses. Inevitably, the desire arose to produce floor coverings with a pile of sheep or goat wool to simulate the warmth and comfort of animal skins. Inevitably, no traces of these floor coverings remain.

The oldest known existing carpet is now to be found in the State Hermitage Museum in St Petersburg, having been excavated from a tomb in Southern Siberia and is 2400 years old. It is a pile rug of fine construction with about 3600 tufts/dm².

1.1.1 Residential use

Carpets for residential use are made throughout the world with particularly important centres in the USA and Western Europe. Important centres of carpet manufacture are emerging in the Indian sub-continent and in China. The products made in each of these centres have evolved in different ways and display different characteristics of style. In general terms, US carpets often have a pile of polyamide in patterned and textured loop pile, polyester in longer cut-pile referred to as ‘Saxony’s’ and more budget-conscious constructions with polypropylene pile.

Western Europe makes a proliferation of tight, low pile constructions with polypropylene the dominant fibre and polyamide for the better end of the market, whilst UK manufacturers retain a more traditional approach with wool remaining the dominant pile fibre usually in relatively luxurious cut-pile styles. At present the most characteristic UK carpet style is a hard-twist cut-pile plain carpet with a wool-rich pile fibre blend.

In the UK, which has historically had a large woven carpet capacity, heavily patterned carpet styles have dominated for many years and indeed there has been a desire to develop less labour-intensive, higher-speed manufacturing methods for these styles. Recent trends, influenced by large volumes of less expensive tufted carpets imported largely from Belgium and Holland, and through lifestyle programmes and articles in the media, have seen the former dominance of the patterned carpet disappear in favour of plainer styles which are favoured for modern living. The media advise that patterned carpets are now making a comeback but this is not reflected in major changes in carpet production patterns and may be a case of the media trying to establish a trend.

1.1.2 Commercial use

Carpets intended for commercial use are often subjected to greater concentrations of traffic and need to withstand this. Commercial use is varied and can include offices, retail premises, hotels and leisure centres, casinos, theatres and airports. Carpets for offices, particularly modern open-plan offices and for some larger retail premises, feature hard-wearing dense low loop-pile constructions usually with polyamide pile. The carpet tile has found particular favour for this end-use.

Carpet tiles, frequently available in 50 cm square or 45.7 cm (18 inches) square formats, lend themselves particularly to large multi-floor installations. Of particular importance is the ease with which the tiles, packed into easily handled boxes, can be transported to upper floors. The original carpet tiles were of a simple felt face layer bonded to the tile backing. Styles have developed from these through needled floor coverings, plain loop-pile tufted, plain cut-pile tufted and even patterned constructions, at each stage gaining in style, luxury and sophistication.

The carpet tile is a composite material composed of a textile use surface bonded to a tile backing which must have the basic important properties of dimensional stability, and the ability to lie flat on the floor without doming at the centre or the curling up of tile edges. Installation of early tiles gained added interest by adopting what is called chequer-board installation, where the manufacturing direction (always denoted by an arrow printed or embossed on the back of each tile) is laid at right-angles to the adjacent tile. This not only changed the surface aspect of the entire installation but also disguised (through emphasis) the tile edges. With more sophisticated and luxurious styles this simple or utilitarian effect was less desirable and the requirement arose for a uniform appearance with joints between adjacent tiles as invisible as possible. This is referred to as broadloom or monolithic installation. This demanded carefully cut tiles and was more easily achieved with denser carpet constructions and cut-pile styles.

In recent years sophisticated designs in loop-pile constructions have enabled tiles to be installed without regard for alignment of manufacturing direction and which do not show colour variations from pile shading.

Patterned carpet tiles must be either totally random or carefully engineered to fit design repeat(s) into the tile dimension. Simple tufted carpet designs achieved with stitch displacement devices appeared initially attractive but the failure of the design repeat dimension, often quite small, to fit exactly into the tile dimension created an effect, colloquially known as ‘zippering’, to occur at tile edges which may be more or less acceptable to the end user. Sophisticated larger repeat designs, sometimes achieved using a woven carpet use surface, or a printed design exactly registered to the tile dimension were inevitably introduced. These included corporate logos which could be inset into plain or lightly patterned areas. The ability of the carpet tile to be easily cut in any direction without fraying lent itself to the creation of particularly large logo installations by carefully creating shapes of different colours and assembling them on the floor.

For the hotel, theatre and airport markets the heavily patterned woven carpet remains important on a global scale. The property of heavily patterned carpets to disguise the inevitable effects of concentrated wear and soiling is extremely important for these end uses and the use of wool-rich pile significantly reduces dangers resulting from burns and scorches from dropped cigarettes.

1.1.3 Carpet properties

Aesthetics

Carpets are available in a wide variety of styles, textures, designs and colours which the skilled interior designer can use to create a stylish interior suited to the activity conducted in the carpeted area. In the home, carpet helps to provide a warm and comfortable environment away from the harsh realities of the everyday world. In commercial buildings carpet helps to make a statement about the enterprise and creates an environment conducive to efficiency.

Thermal insulation

Carpets are excellent thermal insulators, a property that is enhanced further by a good underlay. With conventional heating systems the insulation properties of carpet and underlay can significantly reduce heat loss through the floor. Depending upon construction and specification carpet may have a thermal insulation varying between about 0.1 m²K/W and 0.3 m²K/W.

In the case of under-floor heating, however, the apparently excellent thermal insulation properties of the carpet do not excessively impair the efficiency of the heating system. It is believed that this is a function of the fact that in an under-floor heating situation the carpet becomes the heat transmitter to the airspace above. However, excessively thick and luxurious carpets, particularly when installed on a thick felt underlay, can be expected to slow the rate of transfer of heat from floor surface to airspace to an unacceptable level.

Within the EU the thermal insulation properties of carpet are determined according to ISO 8302 Thermal insulation – determination of the steady-state thermal resistance and related properties – Guarded hot plate apparatus. In the UK the thermal insulation value of carpets has been measured according to BS 4745 (Togmeter) test, but this is no longer considered to provide a reliable guide since it has been determined that compared with actual usage this ‘overstates’ the thermal resistance by a considerable margin.

Acoustic insulation

Changes in lifestyle in recent years, in which smooth floors, particularly wood and laminate floor coverings, have gained in popularity, have demonstrated to the public just how noisy an uncarpeted room can be. Carpeting is one of the most effective ways of reducing noise and the best carpets can provide acoustic insulation to the same level as dedicated acoustic insulation materials.

There are three ways in which carpet can provide acoustic insulation. Possibly the most important of these is impact sound absorption. This is concerned with the way in which sound of say a footfall or a dropped object is transmitted into the room below. The pile of a carpet significantly reduces the energy of the impact and has the effect of converting a sharp high frequency sound into a low frequency thud which has significantly less impact on the ear.

Impact sound absorption is measured according to ISO 717-2 using a tapping box device to generate the noise which drops small hammers onto a floor surface at different frequencies and measuring the sound generated in a room below, all under controlled standard conditions. Comparison of the generated sound through the bare floor with that through the carpeted floor, as a decibel ratio, can be used to evaluate the impact sound absorption properties of floor coverings.

Airborne sound reduction is also measured according to standard method. The test method is described in BS EN 20354 and the Sound Absorption Class may be derived from this according to BS EN ISO 11654. The test method involves a purpose-built reverberation chamber which has three loudspeakers which generate sound at different frequencies in the range 250–4000 Hz and five microphones per loudspeaker. The test is conducted with the floor carpeted and the result compared with the figures taken with the floor bare.

The sound reduction coefficient is calculated taking into account area of carpet, dimensions of the test chamber, etc., and is the average of the reduction in reverberation times at each frequency band. A sound reduction coefficient of 1 would be a perfect insulator and 0 would represent a perfect reflector. The more luxurious carpets will have a sound reduction coefficient as high as 0.5–0.7, equivalent to acoustic ceiling tiles and sufficient to comply with the UK Building Regulations for circulation areas in public buildings.

Safety

The textile surface of a carpet and its three-dimensional structure make carpet a particularly safe surface on which to walk. The carpet surface will have excellent slip resistance and will offer a soft, forgiving surface should falls occur.

From 1 January 2007 carpets sold throughout the EU are required to comply with the health, safety and energy saving...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• 1: Carpet types and requirements
• 2: Structure and properties of carpet fibres and yarns
• 3: Advances in carpet weaving
• 4: Recycling carpet materials
• 5: Developments in wool carpet manufacture
• 6: Developments in textile sports surfaces
• 7: Reducing static electricity in carpets
• 8: The acoustic and thermal properties of carpeted floors
• 9: Finishing of carpets for value addition
• 10: Developments in handmade carpets: Introduction
• 11: Developments in handmade carpets: Design and manufacture
• 12: Developments in the thermal processing of carpets
• 13: Carpets from buyer's viewpoint
• 14: Processing and finishing in carpet
• 15: Carpet cleaning and maintenance
• 16: Carpet wear performance
• 17: Classification of carpets
• 18: Performance measurement and management of handmade carpet industry
• Index