Barrel temperature effects

Bowman [192] conducted a systematic study of the structure-property relations of injection molded polyacetals (polyoxymethylene or POM) and observed correlations between process conditions, structures and mechanical properties. Barrel temperature effects were studied as they are known to influence both microstructure and mechanical properties [193]. Increased barrel temperature was shown to reduce the outer skin layer while increasing the extent of the equiaxed, unoriented core, resulting in a decreased tensile yield strength parallel to the injection direction. 

In the Reclaimator, a high pressure extmder, fiber-free mbber is heated to 175—205°C with oils and other ingredients. High pressure and shear between the mbber mixture and the extmder barrel walls effectively devulcanize the mixture in one to three minutes. In the Lancaster-Banbury method, high temperature, pressure, and shear are appHed to the mbber in a batch process that is otherwise similar to the Reclaimator process. In another high pressure process, scrap mbber is devulcanized at 5.5—6.9 MPa (54—68 atm) for ca five minutes. The product is milled, baled, or pelletized as in other processes. 

The effect of channel depth on solids conveying rate is shown in Fig. 5.26 for screw and barrel temperatures of 75 and 125 °C, respectively, and at a screw speed of 50 rpm. At zero discharge pressure, the solids conveying rates were nearly proportional to the depth of the screw channel (or cross-sectional area perpendicular to the flight). For example, the conveying rates were 91 and 125 kg/h for the 8.89 and 11.1 mm deep screws, respectively. For these screws, the cross-sectional areas perpendicular to the flights were calculated at 420 and 530 mm an area increase of... 

Figure 5.27 The effect of flight radii size on solids conveying rates for a barrel temperature of 75 °C, a screw temperature of 50 °C, and a screw speed of 50 rpm...

Figure 9.9 The effect of the zone 3 and 4 barrel temperature settings on the discharge temperature for the high-rate screw. The rate and screw speed were held constant at 230 kg/h and 58 rpm, respectively...

Pareto effects for L are shown in Figure 2. It was shown that mold temperature (MOLD) had the largest effect on L. Mold temperature had almost twice the effect of barrel temperature (BARREL). These were followed by injection speed (ESfJS) and pack pressure (PACKP). 

Figure 3 shows that a was effected most by mold temperature followed by barrel temperature. Injection speed and pack pressure had the least effect of the significant variables. 

Mold temperature was shown in Figure 4 to have the largest effect on b. Barrel temperature was the only other variable to show significance. 

The Pareto chart for gloss is shown in Figure 5. The largest effect was mold temperature. Barrel temperature was next followed by injection speed, pack pressure and screw speed (SCREWS). 

Increasing the barrel temperature towards the end of the extruder generally increases the conversion, but this temperature rise is limited by the effective temperature range of the initiator. 

Effect of barrel temperature on melting rate when the viscosity is highly temperature sensitive... 

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