Mono-and multifilaments

For the examinations three different mono- and multifilament PET-yams were used. As seen by the effective temperature two of the fibers (220 dtex multifil and 360 monofil) were heat setted in air at 160°C. The experiments in air and supercritical C02 were carried out in a 400 ml autoclave, the DSC measurements (Differential Scanning Calorimetry) under pressure in a home-made apparatus with an integrated TA-Instruments calorimeter. 

For the formation of polypropylene textiles different techniques were developed. The common method used for the formation of mono- and multifilaments is classical melt spinning. 

Figure 4.4 Weave patterns in woven mono- and multifilament cloths.

Each fabric has its own particular characteristic vtiiich can be used to advantage in the filtration process. Thus the smooth-surfaced mono- and multifilament (high-twist) cloths are particularly suited to the liquid environment, in the separation of sticky, clogging substances such as sludges or colloids. Retention of such small material depends on a rapidly formed surfece layer of particulates in the reported use of monofilament polyamides for effluent treatment plants [Grove Daveloose, 1982]. Apparently in this application, change firom q>un fibre to woven cloth increased the cloth lifetime from 3 months to 2.5 years The adhesive nature of such solids may be modified by treatment with polyelectrolytes. Quite opposite results can also be experienced, however, where the three-dimensional capture characteristics of staple fibre material is the best option. 

The use of the PES mono and multifilament yams allowed the ensuring of the proper level of the physico-mechanical characteristics, resistance to the action of the chmnical agents as part of the liquids, serums and human body blood, maintenance of the product biofunctional properties during implant process, thus contributing to the avoidance of new surgical operations with traumatic effects on human body and psychic. All these elements determined the achieving of a complex product with dimensional stability dominant conferred by the link type and the structure parameters as well as by using... 

Metal(mono)filaments. Mono- and multifilaments completely made of metal (alloys) such as copper, stainless steel, etc. Multifilaments here are often referred to as wires. 

For spinning of the textile PP mono- and multifilaments, the best solution is a laminar crossflow air quench duct with a minimum ratio of air quantity to air velocity. For spinning of fiber staple tows, the crossflowing quench air can be applied for rectangular spinnerets, i.e., inside-to-outside radial quenching, or double-direction turbulence quenching [141]. 

Combined mono and multifilament fabrics are now available with useful additional characteristics. Thus such a material is used on disc filter segments, which is elastic and so will expand during the blow-back stage to help with cake release. New belt press filters and large automatic filter presses have put tremendous demands on the physical properties of the filter fabrics, which are being met by heavy dense monofilament fabrics. 

Spinning and Thermosettlng.i i The mesophase pitch is melt-spun in a mono- or multifilament spinneret, heated to 300 - 450°C and pressurized with inert gas. It is drawn at a speed >120 m/min for a draw ratio of approximately 1000/1 to a diameter of 10 -15 jum. The draw ratio is an important factor in the control of the orientation of the fiber structure the higher the draw, the greater the orientation and uniformity. 

Warp-knitted hernia meshes are used in various shapes and sizes, especially for the treatment of tissue fissures (hernia) or in general to reinforce connective tissue. They are produced mainly from polypropylene, polyester, or PVD mono- or multifilament yarns. 

Stratified structures, or asymmetiic media, have beeu used successfiilly in gas and membrane filtration systems. Woven clofiis combining mono-, multifilament and spun yams, made up in special weaves have been produced [Carleton Heywood, 1983], Thus cloths are available which combine retention efficiency, low pressure drop and depth filtration characteristics of spun fibres with the smooth surfiice features of caloidered monofilaments. Inducing a staple fibre character to a press cloth reduces edge leakage problems, in view of the compressible nature of such fibres. 

Figure 2.6 The face side (filtering surface) of a satin weave mono/multifilament cloth. The warp direction is vertical. The reverse side of the cloth has a rougher texture and both warp and weft yarns are clearly visible (Madison Filter).

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