BS EN ISO 1600:1999 pdf free.Plastics – Cellulose acetate – Determination of light absorption of moulded specimens produced using different periods of heating.
BS EN ISO 1600 specifies a method for the determination of light absorption of cellulose acetate, employing test specimens taken from two mouldings which have been produced using different periods of heating.
The aim is to provide quantitative measurements which are compatible with visual judgements of yellowness and lightness, and of changes in these properties after moulding. The determinations are carried out on cellulose acetate in plasticized form rather than in solution, since a more reliable guide is thereby obtained to the performance of cellulose acetate in plastics materials.
This method minimizes the effects of haze or imperfections in the specimens.
This method is intended for cellulose acetate having an acetic acid yield of 54 % ± 2,5 %. It may also be applicable to other transparent plastics which are not strongly coloured and which can he moulded under the specified conditions.
3 Principle
The absorption of visible light by cellulose acetate is normally greatest at the blue end of the visible spectrum, and decreases continuously across the spectrum to the red end. Therefore two measurements of absorption, one at the red end and one at the blue end, are sufficient to characterize the absorption of light by the material.
For the determination of the initial optical density, specimens given the smallest practicable amount of heating are used. The optical densities are measured for blue light and for red light using specified colour filters, and the optical density at 25 mm thickness is calculated as the “initial light absorption”.
The ‘light absorption after further heating” is obtained by similar measurements on further specimens prepared using a longer period of heating during moulding.
5 Apparatus
Ordinary laboratory apparatus, plus the following:
5.1 Hyd raulic press, capable of exerting a pressure of at least 8 MN/rn2 on the moulding surface, with means of heating to 200 °C and with water cooling.
5.2 Mould (see Figure 1 for a suitable type), with polished surfaces substantially flat and parallel, to produce mouldings of thickness within the range 1,5 mm to 5 mm. A particular thickness within this range may be specified.BS EN ISO 1600 pdf download.