Introduction to composite nonwovens 5 structures that,according to him,cannot be considered as composite structures. For example,a single-layer structure,when combined with activated carbon particles or coated or impregnated with some chemicals for exhibiting additional properties,remains as a single-layer structure,hence cannot be considered as a composite structure.He further added that all the layers of a composite structure need not necessarily be nonwoven,that is,one or more layers could be a woven material or membrane material or plastic material or metal mesh material to provide necessary support to the structure.However,McIntyre (2008)describes composite nonwovens as a marriage of two different technologies in one process line or combination of multiple substrates (combination of different types of nonwovens or combination of nonwoven with another type of fabric like a woven or a film)made on entirely different lines.Examples include nonwovens prepared by employing a multi-beam spunmelt line,nonwovens prepared by bonding air- laid and wet-laid nonwovens or woven fabric and nonwoven fabric,etc.However, Batra and Pourdeyhimi(2012)reported that the nonwoven trade uses the phrase composite'for those nonwovens which are either produced by combining laminates of fibres of different types/species(or fibres blended with particulates), or combining laminates of different fibre species with layers of different fibres produced by employing the same technology or different technologies,to obtain a new unified or integrated structure.It is thus clear that there are many definitions available on composite nonwovens.But,whatever definition is chosen,there are enormous possibilities existing for creation of these materials. 1.2 Classification of composite nonwovens Composite nonwovens can be classified under the aegis of raw materials used and process technologies employed for their creation.According to the materials constituting composite nonwovens,they can be classified as multi-fibre composite nonwoven,multi-filament composite nonwoven,combined fibre and filament composite nonwoven,particulate composite nonwoven,and hybrid composite nonwoven.Needless to say,there are numerous ways to prepare each of these composite nonwovens.They can be prepared by employing multi-forming processes,multi-bonding processes,or a lamination process.Then,according to the manufacturing processes employed,composite nonwovens are classified as multi-formed composite nonwoven,multi-bonded composite nonwoven,and laminated composite nonwovens.All of these classes of composite nonwovens are described below. 1.2.1 Multi-fibre composite nonwovens The multi-fibre composite nonwovens are comprised of fibres of different types or species or characteristics or a combination thereof,where the fibres can be mixed intimately or each layer can add different fibres to the fibreweb.Examples include
Introduction to composite nonwovens 5 structures that, according to him, cannot be considered as composite structures. For example, a single- layer structure, when combined with activated carbon particles or coated or impregnated with some chemicals for exhibiting additional properties, remains as a single- layer structure, hence cannot be considered as a composite structure. He further added that all the layers of a composite structure need not necessarily be nonwoven, that is, one or more layers could be a woven material or membrane material or plastic material or metal mesh material to provide necessary support to the structure. However, McIntyre (2008) describes composite nonwovens as a marriage of two different technologies in one process line or combination of multiple substrates (combination of different types of nonwovens or combination of nonwoven with another type of fabric like a woven or a fi lm) made on entirely different lines. Examples include nonwovens prepared by employing a multi- beam spunmelt line, nonwovens prepared by bonding airlaid and wet- laid nonwovens or woven fabric and nonwoven fabric, etc. However, Batra and Pourdeyhimi (2012) reported that the nonwoven trade uses the phrase ‘composite’ for those nonwovens which are either produced by combining laminates of fi bres of different types/species (or fi bres blended with particulates), or combining laminates of different fi bre species with layers of different fi bres produced by employing the same technology or different technologies, to obtain a new unifi ed or integrated structure. It is thus clear that there are many defi nitions available on composite nonwovens. But, whatever defi nition is chosen, there are enormous possibilities existing for creation of these materials. 1.2Classifi cation of composite nonwovens Composite nonwovens can be classifi ed under the aegis of raw materials used and process technologies employed for their creation. According to the materials constituting composite nonwovens, they can be classifi ed as multi- fi bre composite nonwoven, multi- fi lament composite nonwoven, combined fi bre and fi lament composite nonwoven, particulate composite nonwoven, and hybrid composite nonwoven. Needless to say, there are numerous ways to prepare each of these composite nonwovens. They can be prepared by employing multi- forming processes, multi- bonding processes, or a lamination process. Then, according to the manufacturing processes employed, composite nonwovens are classifi ed as multi- formed composite nonwoven, multi- bonded composite nonwoven, and laminated composite nonwovens. All of these classes of composite nonwovens are described below. 1.2.1Multi- fi bre composite nonwovens The multi- fi bre composite nonwovens are comprised of fi bres of different types or species or characteristics or a combination thereof, where the fi bres can be mixed intimately or each layer can add different fi bres to the fi breweb. Examples include
6 Composite Nonwoven Materials composite nonwovens comprising of natural and synthetic fibres,composite nonwovens consisting of natural or synthetic fibres of different types or species or characteristics,and composite nonwovens with gradient structures prepared by a combination of a large-fibre-layer to a small-fibre-layer.Figure 1.1 displays a digital volumetric image of a needlepunched nonwoven material consisting of two layers,one made up of finer fibres and the other made up of coarser fibres. Figure 1.2 shows a scanning electron microscopic image ofa composite nonwoven consisting of electrospun nanofibres and meltblown microfibers. It is believed that by combining the characteristics and performance features of different fibres the composite nonwovens are putting a new twist on the versatility, high performance and quality that have come to be expected from nonwovens (Wuagneux,2006).There are several embodiments of such composite nonwoven materials available.In an exemplary embodiment,Liu et al.(2008)termed an electrospun web of poly(L-lactic acid)and poly(vinyl alcohol)as composite nonwoven material.Duello et al.(2010)disclosed a multi-layered composite nonwoven prepared by combining two webs comprising of staple fibres of different finenesses for the use as a fluid filter. Holliday (1990)illustrated composite nonwoven with the help of a practical example where highloft or fibrefill structures with large areas of openness between fibres was impregnated with the micro fibres from the meltblown process.As a result,the meltblown fibres penetrated into the fibrefill structure and a composite nonwoven fabric was thus formed.Jeambar (2009)developed a composite nonwoven fabric prepared by combining two webs,one made up of synthetic fibres and the other made up of natural fibres.Smithies et al.(2008)disclosed a 0.5mm 1.1 Image of a nonwoven fabric comprising finer fibres laid on coarse fibres
6 Composite Nonwoven Materials composite nonwovens comprising of natural and synthetic fi bres, composite nonwovens consisting of natural or synthetic fi bres of different types or species or characteristics, and composite nonwovens with gradient structures prepared by a combination of a large- fi bre-layer to a small- fi bre-layer. Figure 1.1 displays a digital volumetric image of a needlepunched nonwoven material consisting of two layers, one made up of fi ner fi bres and the other made up of coarser fi bres. Figure 1.2 shows a scanning electron microscopic image of a composite nonwoven consisting of electrospun nanofi bres and meltblown microfi bers. It is believed that by combining the characteristics and performance features of different fi bres the composite nonwovens are putting a new twist on the versatility, high performance and quality that have come to be expected from nonwovens (Wuagneux, 2006). There are several embodiments of such composite nonwoven materials available. In an exemplary embodiment, Liu et al. (2008) termed an electrospun web of poly(L-lactic acid) and poly(vinyl alcohol) as composite nonwoven material. Duello et al. (2010) disclosed a multi- layered composite nonwoven prepared by combining two webs comprising of staple fi bres of different fi nenesses for the use as a fl uid fi lter. Holliday (1990) illustrated composite nonwoven with the help of a practical example where highloft or fi brefi ll structures with large areas of openness between fi bres was impregnated with the micro fi bres from the meltblown process. As a result, the meltblown fi bres penetrated into the fi brefi ll structure and a composite nonwoven fabric was thus formed. Jeambar (2009) developed a composite nonwoven fabric prepared by combining two webs, one made up of synthetic fi bres and the other made up of natural fi bres. Smithies et al. (2008) disclosed a 1.1 Image of a nonwoven fabric comprising fi ner fi bres laid on coarse fi bres
Introduction to composite nonwovens 7 1.2 SEM image of composite nano-and microfibre nonwoven. composite nonwoven material wherein microfibres were combined with nanofibres for the use in filtration application.Welchel et al.(2000)disclosed a composite nonwoven fabric made up of one layer consisting of wood pulp fibres and another layer comprising of polyolefin staple fibres for the use in absorbent products. Bergholm et al.(2005)disclosed a composite nonwoven fabric for the use as a wet wipe which was formed from fibrous layers bonded together by entanglement of fibres of the first and second outer layers each comprising a mixture of hydrophobic and hydrophilic fibres,as well as an intermediate layer ofhydrophobic fibres sandwiched between the first and the second outer layers. 1.2.2 Multi-filament composite nonwovens The multi-filament composite nonwovens consist of filaments of different types or characteristics or a combination thereof,where each layer adds different filaments to the web.Examples include composite nonwovens prepared by combining two spunbonded layers each consisting of different filaments.There are numerous descriptions available for such structure. Bansal (2006)disclosed a patent of stretchable composite nonwoven which was formed by mechanically needling a crimped spunbond web to an elastomeric spunbond web.Boscolo(2008)invented a hydroentangled composite nonwoven fabric comprising of an absorbent pulp layer sandwiched between two layers of spunbond nonwovens.Ferrira and Rieger(2004)fabricated a composite nonwoven material by combining unpulped vegetable fibre webs with spunbond filaments for the use as thermoformed vehicle interior trim products. Boscolo and Maltese(2009)reported a spunbond nonwoven material made up of a plurality of multi-component filaments which was thermo-bonded with polyolefin-based nonwoven layers in order to make a composite nonwoven
Introduction to composite nonwovens 7 composite nonwoven material wherein microfi bres were combined with nanofi bres for the use in fi ltration application. Welchel et al. (2000) disclosed a composite nonwoven fabric made up of one layer consisting of wood pulp fi bres and another layer comprising of polyolefi n staple fi bres for the use in absorbent products. Bergholm et al. (2005) disclosed a composite nonwoven fabric for the use as a wet wipe which was formed from fi brous layers bonded together by entanglement of fi bres of the fi rst and second outer layers each comprising a mixture of hydrophobic and hydrophilic fi bres, as well as an intermediate layer of hydrophobic fi bres sandwiched between the fi rst and the second outer layers. 1.2.2Multi- fi lament composite nonwovens The multi- fi lament composite nonwovens consist of fi laments of different types or characteristics or a combination thereof, where each layer adds different fi laments to the web. Examples include composite nonwovens prepared by combining two spunbonded layers each consisting of different fi laments. There are numerous descriptions available for such structure. Bansal (2006) disclosed a patent of stretchable composite nonwoven which was formed by mechanically needling a crimped spunbond web to an elastomeric spunbond web. Boscolo (2008) invented a hydroentangled composite nonwoven fabric comprising of an absorbent pulp layer sandwiched between two layers of spunbond nonwovens. Ferrira and Rieger (2004) fabricated a composite nonwoven material by combining unpulped vegetable fi bre webs with spunbond fi laments for the use as thermoformed vehicle interior trim products. Boscolo and Maltese (2009) reported a spunbond nonwoven material made up of a plurality of multi- component fi laments which was thermo- bonded with polyolefi n- based nonwoven layers in order to make a composite nonwoven 1.2 SEM image of composite nano- and microfi bre nonwoven
⊙ Composite Nonwoven Materials fabric,particularly suitable for hygiene application.Ferencz(2002)developed a composite nonwoven fabric comprising one or more fine denier spunbond layers and one or more barrier layers.Newkirk et al.(2002)disclosed a composite nonwoven fabric with areas of different basis weights prepared by combining different layers of spunbond nonwovens for the use in hygiene products. 1.2.3 Combined fibre and filament composite nonwovens These composite nonwovens consist of a combination of fibres and filaments such that one layer can add fibres and another layer can add filaments.Examples are SMS/SMMS/SSMMMSS composite nonwovens where relatively small but weak meltblown(M)fibres are sandwiched between large and strong spunbond (S) filaments.Figure 1.3 displays a scanning electron microscopic image of an SMS nonwoven.There are several descriptions available for fibre and filament combined composite nonwovens. Brock and Meitner(1977)of Kimberly Clark disclosed the first patent on SMS structure.Damaghi et al.(2010)disclosed a composite nonwoven consisting of at least one nonwoven layer of staple fibres and an SMS web layer for the use as a wipe.Rudisill et al.(2003)developed a composite nonwoven fabric by including spunbonded filaments and meltblown fibres.Quantrille and Zimmerman(1995) described a composite nonwoven fabric that combined a fibrous layer consisting of staple fibres and an elastic layer comprised of filaments in such a way that it showed low extensibility in machine direction but substantial elastic properties in cross-machine direction.Angelini and Haley (2006)developed a composite nonwoven material by combining a wet-laid layer of staple fibres and a 1.3 Image of composite SMS nonwoven
8 Composite Nonwoven Materials fabric, particularly suitable for hygiene application. Ferencz (2002) developed a composite nonwoven fabric comprising one or more fi ne denier spunbond layers and one or more barrier layers. Newkirk et al. (2002) disclosed a composite nonwoven fabric with areas of different basis weights prepared by combining different layers of spunbond nonwovens for the use in hygiene products. 1.2.3Combined fi bre and fi lament composite nonwovens These composite nonwovens consist of a combination of fi bres and fi laments such that one layer can add fi bres and another layer can add fi laments. Examples are SMS/SMMS/SSMMMSS composite nonwovens where relatively small but weak meltblown (M) fi bres are sandwiched between large and strong spunbond (S) fi laments. Figure 1.3 displays a scanning electron microscopic image of an SMS nonwoven. There are several descriptions available for fi bre and fi lament combined composite nonwovens. Brock and Meitner (1977) of Kimberly Clark disclosed the fi rst patent on SMS structure. Damaghi et al. (2010) disclosed a composite nonwoven consisting of at least one nonwoven layer of staple fi bres and an SMS web layer for the use as a wipe. Rudisill et al. (2003) developed a composite nonwoven fabric by including spunbonded fi laments and meltblown fi bres. Quantrille and Zimmerman (1995) described a composite nonwoven fabric that combined a fi brous layer consisting of staple fi bres and an elastic layer comprised of fi laments in such a way that it showed low extensibility in machine direction but substantial elastic properties in cross- machine direction. Angelini and Haley (2006) developed a composite nonwoven material by combining a wet- laid layer of staple fi bres and a 1.3 Image of composite SMS nonwoven
Introduction to composite nonwovens 9 spunbond layer of continuous filaments.Homonoff et al.(1992)described a hydroentangled composite nonwoven fabric comprising of a combination of spunbond web consisting of continuous synthetic filaments and wet-laid wood pulp fibrous web consisting of staple fibres. Jones and Lim (2010),in an exemplary embodiment,disclosed a composite nonwoven material comprised of nanofibres and spunbonded filaments for the use in filtration applications.Bonneh (2006)developed a composite structure consisting of a spunlaid continuous filament layer and a meltblown staple fibre layer,which,upon subjected to water jet treatment,resulted in the breaking of meltblown fibres and caused the broken ends to extend through the spunlaid layer,thus forming a composite nonwoven fabric for use in absorbent products. Smithies et al.(2010)disclosed a patent on composite nonwoven material that included a nanofibre layer deposited onto a spunbond layer consisting of continuous filaments for the use in air filtration application. Everhart et al.(1994)filed a patent on high pulp content composite nonwoven fabric which was prepared by hydroentanglement of a pulp fibre layer to a continuous filament substrate.Griesbach et al.(1996)described a composite nonwoven fabric prepared by hydroentanglement of two filamentous web layers and a cellulosic layer containing cellulosic fibres.Vuillaume and Noelle (2007)disclosed an invention on a composite nonwoven fabric prepared by hydroentangling a cellulosic fibre layer sandwiched between two webs of spunbonded filaments.Stralin et al.(2011)reported a hydroentangled integrated composite nonwoven material including a mixture of randomized continuous filaments and synthetic staple fibres.Duncan et al.(2003)disclosed a composite nonwoven fabric manufactured by joining a fibrous web that was comprised of wood fibres or a mixture of wood fibres and synthetic fibres to a spunlaid nonwoven by means of hydroentaglement. In a US patent entitled 'composite nonwoven fabrics',Gessner and Trimble (1998)described a composite nonwoven fabric prepared by laminating two oxidatively degraded spunbond nonwoven webs of thermoplastic filaments to a meltblown web of microfibres,thus forming a spunbond/meltblown/spunbond composite nonwoven fabric for numerous applications,including medical garments and disposable absorbent products.Stranqvist (2005)disclosed an invention ofhydroentangled composite nonwoven material prepared by combining layers of continuous filaments,synthetic staple fibres and natural fibres. 1.2.4 Particulate composite nonwovens The particulate composite nonwovens are prepared by embedding particulate matters into nonwoven structures.The particulate matters of interest are activated carbon,super absorbent powders,metal ions,biocides,antimicrobials,abrasive particles,preservative agents,wetting chemicals,etc.Examples include composite nonwoven with immobilized particulate matter,composite nonwoven with one
Introduction to composite nonwovens 9 spunbond layer of continuous fi laments. Homonoff et al. (1992) described a hydroentangled composite nonwoven fabric comprising of a combination of spunbond web consisting of continuous synthetic fi laments and wet- laid wood pulp fi brous web consisting of staple fi bres. Jones and Lim (2010), in an exemplary embodiment, disclosed a composite nonwoven material comprised of nanofi bres and spunbonded fi laments for the use in fi ltration applications. Bonneh (2006) developed a composite structure consisting of a spunlaid continuous fi lament layer and a meltblown staple fi bre layer, which, upon subjected to water jet treatment, resulted in the breaking of meltblown fi bres and caused the broken ends to extend through the spunlaid layer, thus forming a composite nonwoven fabric for use in absorbent products. Smithies et al. (2010) disclosed a patent on composite nonwoven material that included a nanofi bre layer deposited onto a spunbond layer consisting of continuous fi laments for the use in air fi ltration application. Everhart et al. (1994) fi led a patent on high pulp content composite nonwoven fabric which was prepared by hydroentanglement of a pulp fi bre layer to a continuous fi lament substrate. Griesbach et al. (1996) described a composite nonwoven fabric prepared by hydroentanglement of two fi lamentous web layers and a cellulosic layer containing cellulosic fi bres. Vuillaume and Noelle (2007) disclosed an invention on a composite nonwoven fabric prepared by hydroentangling a cellulosic fi bre layer sandwiched between two webs of spunbonded fi laments. Stralin et al. (2011) reported a hydroentangled integrated composite nonwoven material including a mixture of randomized continuous fi laments and synthetic staple fi bres. Duncan et al. (2003) disclosed a composite nonwoven fabric manufactured by joining a fi brous web that was comprised of wood fi bres or a mixture of wood fi bres and synthetic fi bres to a spunlaid nonwoven by means of hydroentaglement. In a US patent entitled ‘composite nonwoven fabrics’, Gessner and Trimble (1998) described a composite nonwoven fabric prepared by laminating two oxidatively degraded spunbond nonwoven webs of thermoplastic fi laments to a meltblown web of microfi bres, thus forming a spunbond/meltblown/spunbond composite nonwoven fabric for numerous applications, including medical garments and disposable absorbent products. Stranqvist (2005) disclosed an invention of hydroentangled composite nonwoven material prepared by combining layers of continuous fi laments, synthetic staple fi bres and natural fi bres. 1.2.4 Particulate composite nonwovens The particulate composite nonwovens are prepared by embedding particulate matters into nonwoven structures. The particulate matters of interest are activated carbon, super absorbent powders, metal ions, biocides, antimicrobials, abrasive particles, preservative agents, wetting chemicals, etc. Examples include composite nonwoven with immobilized particulate matter, composite nonwoven with one