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Rheometers for Uniaxial Extension

There have been many reports of techniques for measuring the response of a melt to uniaxial stretching during the past forty years, but we will mention here only those currently in use. [Pg.392]

We will see that these are usually limited to use at strain rates well below 10 s . In order to reach higher rates, the drawdown of an extruded filament (melt spinning) and the converging flow at the entrance to a capillary have been used to determine apparent extensional viscosities. [Pg.392]

Sketch showing the principle of operation of the rotary clamp invented by Meissner [189], The clamps consist of pairsofgearsthat rotate in opposite directions to stretch the portion of the cylindrical sample between them. The length of stretched sample is constant with time as is the velocity at each clamp.The sample is either immersed in or floated on an oil bath. If there is no slip between the clamps, this arrangement generates uniform uniaxial extension. [Pg.393]

Torque shaft Bearings Chassis Master drum Sample Securing clamps Slave drum Bearings Intermeshing gears Drive shaft [Pg.395]

The Mtinstedt tensile rheometer (MTR) is an end-separation device in which the sample is stretched vertically in a cylindrical oil bath [ 199]. This is an improved version of the universal extensional rheometer described by Mtinstedt etal. [177]. The basic idea is illustrated in Fig. 10.23. The specimen is fastened by an adhesive to small metal plates, one of which is attached to a force transducer at the bottom of the bath, and the other is coupled to a pull rod that is vertically displaced by a toothed belt driven by a motor. This instrument has been used for a number of important studies [ 158,191 ]. The MTR can reach strain rates of 5 s and can be used for creep measurements. The temperature is limited to about 220 °C because of the physical properties of the silicone oil used to fill the bath. [Pg.396]


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