Bohlin Rheometer
12 Dec 2011



Bohlin Horizontal Parallel Plate Rheometer

​Bohlin Horizontal Parallel Plate Rheometer

This apparatus is not in routine operation. Please contact us before requesting to use it.

This rheometer is based on a Bohlin VOR Series controlled shear-stress (CSS) plate-plate rheometer, but is in horizontal geometry (i.e. the plates are vertical). The collimated neutron beam passes through the thickness of the sample, not across its diameter or a chord.

The plates, machined from aluminium alloy for neutron transparency, are 1.5mm thick and 60mm in diameter. The plate attached to the motor is actually of slightly larger diameter and slightly dished so that the other plate may just fit inside. This helps prevent less viscous samples from leaking out. The apparatus was designed for studies of molten polymers.

The plate spacing may be varied from contact to several cm, but is typically set to be 1 - 3 mm for in-situ Rheo-SANS measurements. The beam centre can be scanned vertically along the radius of the plates from 26 - 30 mm (where the centre of the plates is 0 mm). However, the neutron beam does need to be collimated to a smaller diameter (6 mm maximum) than is usual which necessarily increases counting times.

The plates may be optionally housed inside a two-part 'clamshell' oven. This is manufactured in mild steel but because this would interfere with the SANS measurements, 25 mm diameter 'beam windows' have been machined away on either side across the join between the two halves of the oven.  These 'windows' have then been faced with 1mm thick aluminium plate. The inside of the oven, except for cut-outs to match the 'beam windows', is lined with 0.25 mm thick gadolinium foil (a potent neutron absorber) and 5 mm thick silica wool (for insulation), held in place by a stainless steel gauze.

Each half of the oven is fitted with a standard quick-release vacuum coupling.  If necessary this permits the oven to be dynamically pumped to reduce oxidation of a sample, but also serves to allow the fitment of ancillary equipment such as a heater or air/inert gas purge.

Temperature control over the range from room temperature to 550 K is possible. In principle a cryogenic gas supply could be used to provide temperature control below room temperature but this has never been tried.

Shear rates range from 0.004 to 3100 s-1. In oscillatory mode frequencies between 0.001 and 20 Hz are possible. The maximum torque is 1000 g cm.

For further information, see J Sharma, SM King, L Bohlin & N Clarke, Nuc. Inst. Meth. Phys. Res. A, (2010), 620, 437-444.