Clamped apparatus, working

For the above scales, eye protection should be worn and work should be undertaken in a standard fume-cupboard behind a well-anchored polycarbonate screen. It is advisable to wear a protective apron and hand protection whether leather gauntlets or tongs should be used will be dictated by circumstances. Such measures are recommended but it should be ensured that they do not precipitate a hazard as a result of loss of tactile sensitivity (e.g. dropping a flask, overtightening clamps, exerting excessive pressure when assembling apparatus). The material of gloves needs consideration. (PVC but not rubber is suitable for tert-butyl peroxide.)... 

Good clamps for holding glass apparatus in position are essential to the scientist. Also, in many of the operations described in this book the glass-working scientist will need to hold the glass tubes in position with clamps. 

Round-bottom or pear-shaped reaction flasks are preferred, but note that stirring with the usual type of magnetic flea is not possible in pear-shaped flasks. The flasks can have multiple necks so that the apparatus can be configured for temperature measurement, addition of solids or liquids, mechanical stirring and inert atmosphere work (p. 125). No matter which arrangement of components is used, always clamp the reaction flask at the neck and keep the heaviest components (such as an addition funnel containing another chemical) vertically above the flask. A condenser will still function at 30° from vertical and it is not very heavy. 

Buckley and McCrum have recently published work on the anisotropy of creep obtained using a tensile creep apparatus based on precision measurement of clamp displacement. Creep strains up to a maximum of 0 1% were used. The creep compliance was subject to error limits of 5% but the scatter of points on a given creep curve was always less than 0-5% provided creep was terminated after 60 s below room temperature or after 180 s above room temperature. Details of the apparatus have not yet been published. 

Inflation of a sheet clamped over a circular hole suffers the same difficulty. More work has been done with this method (see Dealy, 1982). Inflation has been done with both liquid and gas. The stress and deformation equations are treated in Chapter 1, Exercise 1.10.8, andby Dealy (1982). The results can give the biaxial viscosity function and e up to 2 has been achieved (Rhi-Sausi and Dealy, 1981 Yang and Dealy, 1987). But results so far have been limited to relatively low extension rates. The method requires photography and a somewhat complex apparatus. Inflation tests, however, are similar to the vacuum forming process for making shaped plastic items (Schmidt and Carley, 1975 DeVries and Bonnebat, 1976). Thus there is motivation to continue this work. 

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