Measuring extruder

Table 13.5 Piant-Measured Extruder Performance with the New Pumping Screw...

Various measured quantities such as pressure, torque Brabender measuring extruder, Haake ESM Average to high, subject to instrument High Simulation of the extmsion process... 

The extruder simulation model (ESM) was developed by Handle GmbH. The theoretical fundamental principles and examples for application of the ESM are described in detail in various articles published by Laenger [17]. This model is based on measurements obtained from a special laboratory version measuring extruder of 80 mm barrel diameter. 

A variety of methods are available to measure extrudate thickness. The methods can be broadly classified into contacting and non-contacting techniques. The contacting thickness measurement techniques are generally simple and inexpensive however, the contact of the transducer with the extrudate can adversely affect the extrudate surface quality. In cases where the requirements for surface quality are very high, non-contacting thickness measurement is generally preferred. 

A tape measure can be used to measure distances from about 20 cm up to several meters. Dial calipers are useful for closely measuring extruded products, dimensions of the extruder screws, extrusion tooling, etc. A stopwatch is an indispensable tool for measuring screw speed, line speed, blender calibration, etc. A scale can be used to measure the output of an extruder. A small voltmeter is very useful in making sure that voltage and resistance levels of various components are at their required values. A millivolt source can be used for verifying thermocouple inputs and to check controller response and line continuity. 

Dealy (1982) reviews the experimental methods used to measure extrudate or die swell. Typically the ratio of equilibrium extrudate diameter D, to die diameter 2R is measured... 

Table 10-2 Form for recording measurements on an extruded pipe...

In a molded polymer blend, the surface morphology results from variations in composition between the surface and the bulk. Static SIMS was used to semiquan-titatively provide information on the surface chemistry on a polycarbonate (PC)/polybutylene terephthalate (PBT) blend. Samples of pure PC, pure PBT, and PC/PBT blends of known composition were prepared and analyzed using static SIMS. Fn ment peaks characteristic of the PC and PBT materials were identified. By measuring the SIMS intensities of these characteristic peaks from the PC/PBT blends, a typical working curve between secondary ion intensity and polymer blend composition was determined. A static SIMS analysis of the extruded surface of a blended polymer was performed. The peak intensities could then be compared with the known samples in the working curve to provide information about the relative amounts of PC and PBT on the actual surface. 

Unlike other water-soluble resins the poly(ethylene oxide)s may be injection moulded, extruded and calendered without difficulty. The viscosity is highly dependent on shear rate and to a lesser extent on temperature. Processing temperatures in the range 90-130°C may be used for polymers with an intrinsic viscosity of about 2.5. (The intrinsic viscosity is used as a measure of molecular weight.)... 

In addition, if the swelling of the extrudate is measured in each of these two tests then the swelling ratio using the long die will be Bsr and the swelling ratio using the short die will be Ber (see Section 5.6). Using equation (5.44) and (5.47) this enables the shear and tensile components of the recoverable strains to be calculated and from them the shear and tensile moduli. 

In preliminary tests, melt mixed blends of PP and LCP were processed at six different temperatures (Tcyi 230, 240, 250, 260, 270, and 280°C) with a Brabender Plasti-Corder PLE 651 laboratory single-screw extruder. The measured melt temperatures were about 10°C higher than the cylinder temperatures (Tcyi). The objective was to study the influence of temperature on the size and shape of the dispersed LCP phase. Two different polypropylenes were used to ascertain the effect of the viscosity of the matrix on the final morphology. Different draw ratios were obtained by varying the speed of the take-up machine. 

The melt flow index describes the viscosity of a solid plastic. It is the weight in grams of a polymer extruded through a defined orifice at a specified time. The melt viscosity and the melt flow index can measure the extent of polymerization. A polymer with a high melt flow index has a low melt viscosity, a lower molecular weight, and usually a lower impact tensile strength. 

L. L. Blyler and T. K. Kwei [39] proposed the direct opposite (to 4). In their reasoning, they proceeded from the known and generally acceptable Doolittle equation, which puts liquid viscosity in exponential dependence on the inverse value of the free volume of the latter. According to [39], gas has a volume of its own, the value of which it contributes to the free volume of the polymer when it dissolves therein as a result, viscosity falls. The theoretical formula obtained by the authors was experimentally confirmed in the same work. The authors measured pressure values at the entrance of cylindrical capillaries, through which melts of both pure polyethylene, and polyethylene with gas dissolved in it, extruded at a constant rate. 

Anisotropic material In an anisotropic material the properties vary, depending on the direction in which they are measured. There are various degrees of anisotropy, using different terms such as orthotropic or unidirectional, bidirectional, heterogeneous, and so on (Fig. 3-19). For example, cast plastics or metals tend to be reasonably isotropic. However, plastics that are extruded, injection molded, and rolled plastics and metals tend to develop an orientation in the processing flow direction (machined direction). Thus, they have different properties in the machine and transverse directions, particularly in the case of extruded or rolled materials (plastics, steels, etc.). 

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