Drawing of fibres

This stretching, similar to the drawing of fibres, which promotes orientation and crystallite formation, is called biaxial orientation. It gives the film added strength and gas-barrier properties. In some processes, monoaxial (uniaxial) drawing is employed, e.g., polypropylene, which is then slit into thin strips and fabricated into heavy duty sacks, carpet backing, etc. The stenter process is used to make biaxial oriented poly(vinylidene dichloride) ("ding" film), polyester, polyamide and polypropylene films. 

Although some operations in the plastics industry, such as calendering, could be described as stretching processes, the most important application of stretching is usually called drawing (of fibres and films). 

The next major development takes up the idea of the gel layer, and combines this with the tensile drawing of fibres at high temperature, hopefully to give a preparation route which is more acceptable in terms of production rates. We therefore now have a two stage process, in which a fibre of suitable initial structure is first produced, followed by a hot stretching process, and historically two parallel accounts have been given more or less contemporaneously. Smith and Lemstra describe the... 

If the radius, r,of the base decreases by dr, the area decreases by dA = 27rrdr. Hence as separation proceeds, dAjj/dr decreases. Also, Oy is likely to increase, if the local temperature is constant this commonly occurs in the drawing of fibres for textile applications. In addition, elastic energy will be stored in the fibril see above. So, if the system starts out conforming to the inequality, (lb), (i.e., no base peeling) the right side will increase, as the extension, , increases. The result may be a switch to the inequality (la), and, as already noted, the start of base peeling, and the complete interfacial detachment of the fibril at its base. We will examine the inequalities, (la) and (lb), below, with numerical examples. 

The relative importance of these two (opposing) effects depends upon the material, the length and thickness of the specimen, and the test conditions, espiecially the strain rate. The drawing of fibres, film, and sheet in forming operations occurs at very high strain rates. 

Changes in crystallinity on cold drawing of fibres Failure mechanisms in fibre composites Plastic deformation studies in polarised light... 

We deduce from these experiments that once the first high-friction stick has occurred the P.T.F.E. in the contact region is pulled into a direction which favors easy drawing of the polymer chains These adhere to the surface as sliding occurs. The results of (e) suggest that the force to draw out the polymer chains from within the bulk of the specimen is essentially the same as the force required to slide the polymer, now itself oriented, over an oriented film. Thus additional drawing of fibre, i.e. 

Addition of the nanometric powders significantly affected the polymer viscosity (Table 3). The pure polymer fibres could be formed at 244 cP while viscosity of the nanocomposite mixture was over 300 cP. The viscosity in turn determined rate of drawing of fibres from the liquid polymer. 

Glass in the form of fibres is relatively inexpensive and is the principal form of reinforcement used in plastics. The fibres are produced by drawing off continuous strands of glass from an orifice in the base of an electrically heated platinum crucible which contains the molten glass. The earliest successful glass reinforcement had a calcium-alumina borosilicate composition developed... 

Changes of fibre optical properties and thus changes of the analyte can be detected in the ultraviolet (UV), visible (VIS), near infrared (NIR) and middle/far infrared (IR) regions. There are only a few materials sufficiently transparent in the UV region, and among them, the pure silica is uniquely suitable for fibre drawing. From Figure 5 it can be seen that the UV... 

Fig. 15 Initiation of fibre fracture by a crack oriented parallel to the chain direction in a domain. It is proposed that a circular crack with a radius q releases the strain energy in a sphere around the crack with the same radius. Note that in this two-dimensional drawing only the circular crack is shown in perspective...

The muscle is a highly organized tissue, built up of individual cells known as fibres, which are held together by connective tissue. Each muscle fibre consists of a high number of single strands of myofibrils. The myofibrils are again comprised of myofilaments. The myofilaments are divided into thin and thick filaments, which mainly contain two filamentary proteins, actin and myosin, respectively. The myofibrils occupy approximately 80% of the muscle cell volume, and the majority of the water, which makes up about 75% of the muscle, is located in the spaces between thin and thick filaments. A schematic drawing of muscle structure is shown in Fig. 1. 

The motion of the roll over tho plate draws tho rags into a fibrous substance called, as already stated, half-stuff. Experience and care are required In this operation, If it is performed too quickly, or if the rap are cut too short, the paper will be weak, and a peat lose of fibre in future operations will be the consequence. 

The metal ion uptake profiles are shown in Fig. 11.1 for variations of NaCNS concentration (Fig. 11.1a), temperature (Fig. 11.1b) and plasticisation drawing (Fig. 11.1c) of the precipitation bath for Co uptake. Similar curves were obtained with Ni. Table 11.2 shows the data for different parameters related to a fully metallised fibre obtained after metallisation of PAN fibres, produced under different experimental conditions of the precipitation bath. Despite the fact that the uptake profiles are considerably different and the data obtained (diffusion coefficient) confirms this, no remarkable changes are observed in the total amount of metal absorbed by the fibre. This means that saturation for metal uptake is obtained independently of the precipitation bath parameters. The role of these parameters is limited to the rate of metal uptake, and a choice for the optimal value of these parameters should be based on economic reasons first the consumption of chemicals and energy and, secondly, the processing time. Taking these two criteria into account, a NaCNS concentration of about 12%, a temperature of 283 K and a plasticisation drawing of 500% are further used. 

Figure 7.25 One-dimensional imaging with the NMR-MOUSE (a) Single-point imaging sequence for phase-encoding of space, (b) drawing of the NMR-MOUSE with coils for pulsed field gradients, (c) sample of an elastomer sheet with parallel textile fibres and one-dimensional NMR image with the space direction perpendicular to the fiber direction...

Drawings of colloidal structures are usually not to scale. The parts (bubbles, drops, fibres and so on) of a structure typically have dimensions in the range of a micrometre the stabilizing species mostly have dimensions in the range of a nanometre, so a thousand times smaller. Stabilizers only occupy a thin layer near an interface. 

It is not excluded that this mechanism is observed during the formation of fibres from X-500 The authors of this work pointed out that when the fibre was heated to 250-300 °C, its spontaneous elongation took place. Note that to attain higher orientation of a polymer in a fibre, it is necessary not only to transfer it to the liquid crystalline state but also to orient the liquid crystalline domains formed along the axis of the fibre. This orientation of the domain in which the macromolecules have been already mutually ordered requires not too high a draw ratio (the theoretical value must be <2). Indeed, experiments have shown that at the draw ratio of 1.53 to 1,70 the modulus (E) and the tensile strength (a) of the fibre at thermal treatment increase, which can be seen from the table compiled according to the results of this work. 

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