Plasticator channels

The exit region of a die used to extrude a plastic channel section is 10 mm long and has the dimensions shown below. If the chaimel is being extruded at the rate of 3 m/min. calculate the power absorbed in the die exit, and the dimensions of the extrudate as it emerges from the die. The flow curves in Fig. 5.3 may be used. 

Plastic channels could also be fabricated by the hot wire-imprinting method. A channel was imprinted on a piece of Vivak (copolyester) by a nichrome wire (50 pm dia.). It was clamped between the plastic and a glass slide (see Figure 2.21), and the assembly was heated at 80°C for 15 min. Then a perpendicular channel was similarly imprinted on a second piece of Vivak. The two pieces were then sealed at 75°C for 25 min (note that the two channels are not coplanar )[1011]. The channels were filled with water for storage [204,685]. 

The reinforced window frame channel, eg, the large Russian RM channel (109) and the smaller Russian U25B channel (110), is essentially a window frame channel inside a plastic box which serves as the pressure vessel and main stmctural member. It combines some features of both window frame and plastic box constmction. Frames can be segmented, although with some difficulty, for fault power control. This constmction is difficult to disassemble for inspection and/or refurbishment. 

Environmental Impact of Ambient Ozone. Ozone can be toxic to plants, animals, and fish. The lethal dose, LD q, for albino mice is 3.8 ppmv for a 4-h exposure (156) the 96-h LC q for striped bass, channel catfish, and rainbow trout is 80, 30, and 9.3 ppb, respectively. Small, natural, and anthropogenic atmospheric ozone concentrations can increase the weathering and aging of materials such as plastics, paint, textiles, and mbber. For example, mbber is degraded by reaction of ozone with carbon—carbon double bonds of the mbber polymer, requiring the addition of aromatic amines as ozone scavengers (see Antioxidants Antiozonants). An ozone decomposing polymer (noXon) has been developed that destroys ozone in air or water (157). 

Fig. 3. (a) Channel with block of molten plastic (b) channel with moved block of molten plastic arrow indicates direction of material movement (15). 

Cartridges are inserted in series into plastic or stainless-steel tubular pressure housings of square cross section (Fig. 14). Feed flows parallel to the leaf surface. A permeate fitting secures each cartridge to the housing wall, which allows permeate egress and faciUtates sealing between concentrate, atmosphere, and permeate channels. 

Compaction of the filter bed over time will result in gas channeling and pressure-drop increases. This can be avoided by adding large, rigid particles such as plastic spheres, ceramics, or wood/bark chips to provide additional support to the filter substrate. 

T] = viscosity of the plastic L = length of channel Q = volume flow rate R = radius of channel... 

An extruder is coupled to a die, the output of which is given by (KP/ij) where P is the pressure drop across the die, i] is the visco.sity of the plastic and is a constant. What are the optimum values of screw helix angle and channel depth to give maximum output from the extruder. 

To add to this picture it should be realised that so far only the viscous component of behaviour has been referred to. Since plastics are viscoelastic there will also be an elastic component which will influence the behaviour of the fluid. This means that there will be a shear modulus, G, and, if the channel section is not uniform, a tensile modulus, , to consider. If yr and er are the recoverable shear and tensile strains respectively then... 

A power law plastic is injected into a circular section channel using a constant pressure, P. Derive an expression for the flow length assuming that... 

These methods rely on temperature changes, alternation of channel dimensions and flow rates, to produce foamed articles of a required structure, which is important for manufacturing foamed and foam-filled articles made of plastics, as well as for equipment design in this sphere. 

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