Polymer Testing 5 (1985) 243

Editorial

The paper in this issue (James and Gilder, pp. 269-307) giving comparat ive results for rubber test pieces prepared by moulding, bulling and slitting brings to mind the whole question of when it is appropriate to test laboratory prepared specimens and when it is desirable to test specimens obtained f rom the product.

There is evidence enough that results may be very different in the two cases and indeed common sense tells one that this would be the case. Consequent ly it is reasonable to conclude that in any instance where it is quality or pe r fo rmance of the product which is of interest it is be t ter if the test is made on the product or on test pieces cut f rom it.

It is equally reasonable that this approach is not and cannot always be followed because of the extra t ime and cost involved in producing test pieces and because in many cases it is ext remely difficult, if not impossible, to ei ther obtain suitable test pieces f rom the product because of its geomet ry or devise satisfactory tests on the complete part.

Work has been repor ted on test piece preparat ion techniques and relatively recently a number of miniaturised test pieces have reached the point of being included in test me thod standards. However , it may be quer ied as to whe the r there is scope for fur ther work to devise technically improved and more economical test piece cutt ing/machining techniques and also whe the r sufficient effort has been put into proving reliable and effective test procedures and apparatus for very small test pieces.

Even with the techniques currently known it could be argued that specifications tend to take the easy route and specify the normal s tandard tests on s tandard laboratory test pieces. Certainly a great many appear to have made no effort to ei ther include per formance tests on the product or to select methods and test pieces which would allow s tandard propert ies to be obtained on parts f rom the product . Perhaps then there is a non-technical barrier or de ter ren t to more product testing because of the way many specifications are written.

R. Brown 243

Polymer Testing (5) (1985)---~ Elsevier Applied Science Publishers Ltd, England, 1985. Printed in Northern Ireland