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Nonwovens for Home Textiles
Nonwoven fabric is a fabric-like material made from lengthy fibers, bonded together by chemical, mechanical, heat or solvent treatment. In simple terms, they are textiles made from fibers or threads joined together without weaving. Nonwoven materials classically lack strength unless densified or toughened by a backing. In recent years, nonwovens have become an alternative to polyurethane foam.
Nowadays nonwoven fabrics are mostly used as home furnishing fabrics. Nonwoven fabrics are described as sheet or web structures bonded together by entangling fiber or filaments (and by perforating films) mechanically, thermally or chemically. They are flat, porous sheets that are made directly from separate fibers or from molten plastic or plastic film. They are not made by weaving or knitting and do not require converting the fibers to yarn. Typically, a certain percentage of recycled fabrics and oil-based materials are used in nonwoven fabrics. The percentage of recycled fabrics varies based upon the strength of material needed for the specific use. Conversely, some nonwoven fabrics can be recycled after use, given the proper treatment and facilities. For this reason, some consider nonwovens a more ecological fabric for certain applications, especially in fields and industries where disposable or single use products are important, such as hospitals, schools, nursing homes and luxury accommodations.
Nonwoven fabrics are engineered fabrics that may be a limited life, single-use fabric or a very durable fabric. Nonwoven fabrics provide specific functions such as absorbency, liquid repellence, resilience, stretch, softness, strength, flame retardancy, washability, cushioning, filtering, use as a bacterial barrier and sterility. These properties are often combined to create fabrics suited for specific jobs, while achieving a good balance between product life and cost. They can mimic the appearance, texture and strength of a woven fabric and can be as bulky as the thickest paddings. In combination with other materials they provide a spectrum of products with diverse properties and are used alone or as components of apparel, home furnishings, health care, engineering, industrial and consumer goods.
Types of nonwoven fabrics: Nonwovens, depending on the production process can be divided into:
? Materials produced by physicochemical methods; and
? Mechanically produced materials.
Materials produced by physicochemical methods
Most nonwoven materials, are made by binding fibers with adhesives. The most common glued materials are those based on fibrous cloth (a layer of textile fibers whose weight is 10–1000 gsm and more). The cloth is most often formed mechanically from several layers of combed fibers passing through the dotting drum of a combing machine. Fibrous cloth may be produced by the aerodynamic method in which the fibers are removed from the drum of the combing machine by a stream of air and transferred to a mesh drum (condenser) or a horizontal mesh with a maximum speed of up to 100 m/min, or by water dispersion of the fibers on the mesh of a paper machine.
A fibrous cloth is usually made of cotton, a mixture of viscose and polyamide fibers or the waste products of textile manufacture, including unspun fibers. The most common method of producing bonded nonwoven materials are to impregnate the cloth with a liquid adhesive or spraying/printing the adhesive over the surface of the cloth. Gluing the fibers includes saturate bonding and spray bonding or a latex adhesive is applied to the fibers and then the fabric is dried. The impregnated material is dried and treated in chambers heated by hot air or infrared radiation. The nonwoven materials made in this fashion (at a rate of 50 m/min and more) are used as interlacing and sealing materials, as heat and sound insulation materials for upholstery, bedding and drapery liners.
Melting fibers together can only be accomplished with synthetic, thermoplastic fibers or with a blend of fibers containing thermoplastic fibers or fusable powders. These methods include thermal bonding (heat applied to the web with or without pressure) a carded web, ther-mobonding a spunlaid web with a calendar, thermobonding a melt blown or flash spun web with a calender, thermal bonding a carded or air laid high loft web in an oven.In the hot-pressing process, the fibers are bonded by thermoplastics such as polyamides, polyethylene, and polyvinyl chloride at pressures of up to 2 mega newtons per sq m (MN/m2), or 20 kilograms-force per sq cm (kgf/cm2), at high temperatures, usually on special calenders. The bonding is preceded by thermal treatment of the fiber layer, which contains an adhesive that is applied to the fibrous cloth during its formation or after its formation.
In the spunbonded method, synthetic fibers are formed as they leave the spinnerets of spinning machines and pass through troughs in which they are stretched in an air current; they are then placed on a conveyor belt and form a sheet. The material formed in this way is most often bonded with an adhesive; in some cases the stickiness of the fibers themselves is sufficient.
SPUNBOUND/SPUNLACE
Spunlace nonwoven fabric is produced by depositing extruded, spun filaments onto a collection belt in a uniform random manner followed by bonding the fibres. The fibres are separated during the web laying process by air jets or electrostatic charges. The collecting service is usually perforated to prevent the air stream from deflecting and carrying the fibres in an uncontrolled manner. Bonding imparts strength and integrity to the web by applying heated rolls or hot needles to partially melt the polymer and fuse the fibres together. Since molecular orientation increases the melting point, fibres that are not highly drawn can be used as thermal binding fibres. Polyethelene or random ethylene-propylene copolymers are used as low melting bonding sites.
Spunbound products are employed in carpet backing, geotextiles, and disposable medical/hygiene products, automotive products, civil engineering and packaging products.
The process of Spunbound non-woven production tends to be more economical as the fabric production is combined with the fibre production.
AIRLAID
The process of airlaying is a non-woven web forming process that disperses into a fast moving stream and condenses them onto a moving screen by means of pressure or vacuum.
Airlaid fabrics is mainly composed of woodpulp and has a nature of absorbing well. It can be mixed with a definite proportion of SAP to improve its capabilities of absorbing wet. Airlaid non-woven is also referred to as dry paper non-woven. The nonwoven is made through the airlaying process. Transit the woodpulp into the bundle of airflow to make the fibres disperse and agglomeration on the floating web. Airlaid non-woven is reinforced of web.
Airlaid non-woven products are employed in a number of different products across a wide range of industry’s including; the interlining of clothes, medical and hygiene products, embroidery material and filter material.
DRYLAID
Dry laid webs are mainly produced using staple fibres natural or manmade. Dry laid webs formation mainly consists of 4 steps:
Staple fibre preparation –> Opening, cleaning, mixing & blending –> Carding –> Web laying.
Advantages of Drylaid non-woven production include; The isotropic structure of the web, voluminous webs can be produced and a wide variety of process able fibres such as natural, synthetic, glass, steel and carbon.
Drylaid non-woven products are employed by many products ranging from cosmetic wipes and baby diapers to beverage filtration products.
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