Extrusion rheometers

Extrusion reactions, aromatic system formation by, 21 148 Extrusion rheometers, 21 730-731 Exudate gums, 13 61, 63t Exudation, from TNT, 10 734 Ex-works prices, 15 37 Exxal 6... 

Jastrzebski, Z.D., Entrance effects and wall effects in an extrusion rheometer during the flow of concentrated suspensions, Industrial and Engineering Chemistry, 6, No. 3,pp. 445-54(1967). 

To evaluate extensively the processability of PVC/EPR and to compare it with that of PVC having roughly the same molecular weight, we carried out a set of measurements by a capillary extrusion rheometer and Brabender plastograph. Other runs were carried out by an industrial size extruder. 

The compounds we examined in extrusion rheometer and in plastograph had the same recipe as that adopted for determining the physical-mechanical characteristics. However, extrusions were carried out with rigid compounds having an industrial recipe suitable for pipes and sections. Gelation of the dry blend, obtained by turbomixer (10 minutes at 1800 rpm, max. temp. 100°C) was carried out by two-roll mill for 10 minutes at 180°C the blank sheets were mechanically granulated. 

The flow properties by extrusion rheometer MCR type (11) were determined at 180° and 200°C in the shear rate range of 1.76 to 1760 sec"1. 

Viscometers can be divided into rotational instruments and axial flow instruments. Rotational instruments include concentric cylinder (cup and bob), cone and plate and parallel disc viscometers, while axial flow instruments include capillary, slit and extrusion rheometers. 

Consistency of fats is commonly determined with the cone penetrometer, as specified in the Official and Tentative Methods of the American Oil Chemists Society (Method Cc 16-60). Other methods that have frequently been employed involve extrusion they include the extrusion attachment to the shear press (Vasic and deMan 1967), an extrusion rheometer used with the Instron universal testing machine (Scherr and Witt-nauer 1967), and the FIRA-NIRD extruder (Prentice 1954). 

Table IV shows the viscosity characteristics of these systems under high shear rates. The Severs extrusion rheometer, an efflux type instru-...

Severs extrusion rheometer, viscosity (cP) vs. shear rate (sec-1). 

Figure 10. High shear rate viscosity characteristics of formulations I, II, and III from Table II (Serves extrusion rheometer)...

Ogorzalek (II) has studied in detail the effect of shear rate on the viscosity of organosols. His data for low shear (Brookfield) and high shear (Extrusion Rheometer) viscosity characteristics using alcohols as diluents are shown in Figures 36 and 37. 

Dynamic Extrusion Rheometer T, Value The dynamic extrusion rheometer values ( processing temperature) were determined in the proprietary BFGoodrich Research dynamic extrusion rheometer17 according to the established procedure. 

Allen and Rides, NPL Report CMMT(A)9. Intercomparison of extrudate swell measurements using extrusion rheometers for a polyethylene melt. Jan. 1996. 

Perhaps the most important factor to a process engineer in predicting extrusion or molding behavior is melt viscosity. Several methods are used to obtain the viscosity of polymer solutions and melts experimentally as a function of shear rate [19]. Instruments for making such measurements must necessarily accomplish two things (1) the fluid must be sheared at measurable rates, and (2) the stress developed must be known. Two kinds of instruments having simple geometry and wide use a rotational viscometer and capillary or extrusion rheometer. 

Pressure-driven piston cylinder capillary viscometers, ie, extrusion rheometers (Fig. 22), are used primarily to measure the melt viscosity of pol5uners and other viscous materials (20,51,53-55). A reservoir is connected to a capillary tube, and molten polymer or another material is extruded through the capillary by means of a piston to which a constant force is applied. Viscosity can be determined from the volumetric flow rate and the pressure drop along the capillary. The basic method and test conditions for a number of thermoplastics are described in ASTM D1238. Melt viscoelasticity can influence the results (190). 

A number of instruments are based on the extrusion principle, including sUt flow and normal capillary flow (Table 6). These instruments are useful when large numbers of quality control or other melt viscosity test measurements are needed for batches of a single material or similar materials. When melt viscosities of a wide range of materials must be measured, rotational viscometers are preferable. Extrusion rheometers have been applied to other materials with some success with adhesives and coatings (8,191). 

The majority of published work on extrusion behaviour deals with compounded stock. Those papers reporting work on raw rubbers have usually been on the use of capillary rheometers to determine extrusion properties at higher shear rates than are possible with Mooney viscometers. Capillary rheometers are, in principle, quite simple to use, and the application of electronic, minicomputer and laser technology has reduced the operation and data analysis to a routine task. There are no standard ASTM or other test procedures, but under a specific set of conditions, once a material is characterized, the data can be used as standard for comparison of all subsequent batches. It is readily possible to characterize a raw rubber by an extrusion experiment to determine the viscosity/shear rate curve, extrudate swell, and stress relaxation.Both Sezna and Karg have shown how the Monsanto Processability Tester (MPT), a modified, computerized extrusion rheometer, can be used in predicting mixing behaviour. The MPT (shown schematically in Fig. 7) is a most versatile instrument. It has a larger than conventional barrel for minimal pressure drop in the barrel, a pressure transducer at the entrance to the orifice, a microprocessor system, and a laser device for... 

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