Multifilament Effects

Figure 9.13. Radial distribution of molecular orientation in a filament cross-section. 9.1.7 Multifilament Effects...

Although multifilament effects are important, there are few literature reports on this topic mainly because of the complexities associated with accurately describing the heat transfer and dynamics during multifilament spinning. The interested reader is referred to the original works by Yasuda et al. (1978), Ishihara et al. (1989), and Dutta (1987). 

Oligomeric hindered amine light stabilizers are effective thermal antioxidants for polypropylene. Thus 0.1% of A[,Af-bis(2,2,6,6-tetramethyl-4-piperadinyl)-l,6-hexanediamine polymer, with 2,4,6-trichloro-l,3,5-triazine and 2,4,4-trimethyl-2-pentaneainine [70624-18-9] (35) (Fig. 5), protects polypropylene multifilaments against oxidation when exposed at 120°C in a forced-air oven (22) for 47 days. 3,5-Di-/ l -butyl-4-hydroxytoluene [128-37-0] (0.1%) affords protection for only 14 days. 

Multidentate V-heterocyclic ligands, thorium and, 24 767 Multidimensional gas chromatography, 4 617-618 6 433-434 Multidrug resistant bacteria, 18 252 Multi-effect distillation (ME), 26 65—67 Multi-effect vapor-compression submerged-tube desalination plant, 26 70 Multielevation piperacks, 19 515 Multifeed fractionation, 10 616 Multifilamentary superconductor, 23 846 Multifilament sutures, 24 218 threads for, 24 207 Multifilament yarns, 11 177-178 Multifile patent searches, 18 244 Multifunctional aliphatic epoxies, 10 376 Multifunctional coatings, 1 714-716 Multifunctional epoxy resins, 10 367-373, 418, 454... 

ISO 1346 2004 Fibre ropes - Polypropylene split film, monofilament and multifilament (PP2) and polypropylene high tenacity multifilament (PP3) - 3-, 4- and 8-strand ropes ISO 1873-1 1995 Plastics - Polypropylene (PP) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 1873-2 1997 Plastics - Polypropylene (PP) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 3213 1996 Polypropylene (PP) pipes - Effect of time and temperature on expected strength... 

Knowing the deleterious effects of ionising radiations on PTFE, much attention was paid on their effects on PVDF although the latter had been told to behave well under irradiation. As an example, PVDF multifilament yarns can be y irradiated up to the absorption of 80 kGy without any effect on their Young s modulus [38], However, the structure of the polymer was somewhat modified as its energy to break kept constant and even increased by about 50% while the adsorbed dose was less than 8 kGy but decreased for higher adsorbed doses, down to 1/3 of its maximum value (1/2 of its initial value) when the adsorbed dose reached 81 kGy. To avoid these bulky effects, the interest of... 

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. 

Another important attribute of a HALS is its effect on the thermo-oxidative stability of polypropylene multifilaments. This property is important in certain end-use applications where elevated temperature over a period of time is experienced, such as in automobile rear shelf fabrics. The excellent performance of the oligomeric HALS 4 and 6, as determined by 120°C oven aging, is shown in Figure 2. The superior activity of these products may be due not only to their low volatility but also to the presence of a triazine moiety in the structure, which appears to have a positive effect on the thermo-oxidative stability of polypropylene. 

Polyester, nylon and polypropylene are common materials found in monofilament, multifilament and spun materials. Natural fibers such as cotton and wool are found only as spun material. This results in a fuzzy appearance. The effect of the type of yam on cloth performance is shown in Table 1. 

In LTHA and photoaging of PP and LDPE, 35a is a more efficient LTHS than 34 [138]. In combinations of the two HAS, the increase of the relative concentration of 35a improved the observed long-term heat stability effect. In applications, where oligomeric HAS are the principal stabilizers of choice, e.g. in PP fine multifilaments, 1 2 combinations of the two HAS 34 and 35a provide excellent synergism [138], This combination represents the state-of-the-art in the light stabilization of LDPE/L-LDPE/EVA films. 

Fig. 1. Axial currents in the multifilament conductor (a) external field induced hysteresis coupling currents (b) self-field influence on transport currents (c) external field influence on transport currents (d) net current pattern from the combination of effects.

These equatioirs were used in an extensive study of the effect of multifilament characteristics in filtration, including such aspects as t dency to bleed, filtration mode (Chapter 2), [Rushton Hassan, 1980], The basis of this work was the premise that where particles are small enou % enter cloth pores and in the circumstances vdiere yam flow is possible (O > 1), the possibility follows that such particles will follow the filtrate flow into the yams. These particles become embedded within the yams this tends to diminish yam in porosity with W approaching unity. Removal of the particles by back-wadiing becomes difficult, since back-wash will tend to follow the path of least resistance, ie. around the plugged yams. 

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... 

Thomas SN, Hridayanathana C. The effect of natural sunlight on the strength of polyamide 6 multifilament and monofilament fishing net materials. Fish Res 2006 81 (2-3) 326-330. 

Monofilament sutures are considered to be a better choice than multifilament ones in closing contaminated wounds. Multifilament sutures elicit more tissue reactions which may lessen tissue ability to deal with wound infections. They also have a capillary effect which could transport microorganisms from one region of the wound to another. The reason that multifilament sutures generally elicit more tissue reactions than their monofilament counterparts is because inflammatory cells are able to penetrate into the interstitial space within a multifilament suture and invade each filament. Multifilament sutures also have a larger surface area in contact with tissues which should be expected to elicit more tissue reaction. 

Chudoba R, Vorechovsky M, Eckers V and Gries T (2007), Effect of twist, fineness, loading rate and length on tensile behavior of multifilament yarns (a multivariate study) , Text Res J, 77(11), 880-891. 

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