Bi-component fibres

GlauB et al. (2013) have reported the development of a PVDF fibre with a conductive core. The melt-spun bi-component fibre consists of a conductive polypropylene core (containing a 10 wt % carbon nanotubes and 2 wt% sodium stearate (NaSt)) covered with a PVDF sheath. The piezoelectric effects are achieved by draw winding, which favours the all-trans p phase formation. 

Abstract Bi-component melt-spinning has been widely applied to produce functional and novel fibres such as hollow fibres, electrically conductive fibres, etc. This chapter details the extrusion of bi-component fibres and discnsses issnes affecting the structure-property of the fibres during the spinning process, interfacial interaction parameters and compatibility of the polymers to be chosen for sheath-core spinning. 

It also details the apphcation areas of bi-component fibres and future directions of research in this field. 

Bi-component fibres can be made from two variants of the same generic fibre (two types of polyester (PES), polyethylene terephthalate (PET), copolyester (coPES), polyacrylonitrile (PAN), polyamide (PA), polyethylene (PE) and polypropylene (PP)). The fibres can also be made from two different polymer compositions, e.g. PET/PA, PA/Spandex, etc. Different types of polymers, such as polyester, polyamides, polystyrene, polyurethane, polyolefines, polylactic acid, co-polyamides and soluble co-polyesters, have been used to spin bi-component fibres. 

Bi-component fibres can be classified into three types ... 

Cross-sectionai conformations of different types of bi-component fibres... 

It is interesting to note the developments in the spinning designs of bi-component spinning. One of the hrst patents in bi-component spinning went to Okamoto from the US Pat. No. 3531368. As seen in Rg. 6.5, the melt-ers 41 and 42 are for two different polymers through metering pumps 61 and 68. IVansfer pipes 57 and 59 transfer dual streams from the left hand pump to the spinneret assembly, from where the bi-component fibres are extruded. 

In another work by Shi et sheath-core type poly (butylene terephthal-ate)/poly(butylene adipate-co-terephthalate) (PBT/PBAT) bi-component fibres were produced by extruding the melts of PBT (intrinsic viscosity of 0.88 dL/g) as the sheath and PBAT (melt volume flow rate of 3-6 mL/10 min) as the core, using two different extrusion systems. The co-axially combined polymer melts were extruded through an annular-type spinneret at a... 

Recently, tricomponent spinning systems have been developed to coextrude three different polymers into each fibre. Interestingly, some bi-component cross-sections have been utilised in spunbond fabrics, in which filaments are extruded directly into a non-woven web without forming fibres as an intermediate product. The precision of polymer control to form the cross-section wiU continue to advance. After persistent research. Hills has been able to produce spin packs capable of stuffing hundreds of islands into each fibre cross-section, which enables the production of submicron microfibres. The future thus lies in further reduction of the ultimate denier of the fibres, improved spinning processes with more control, and exploration of more interesting applications for bi-component fibres with varying polymers and processes. 

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