POLYETHYLENE AS A PACKAGING MATERIAL i'Experiments were then carried in which polyethylene sacs were with water, with air-free water with oil, and the los•-in weight volume changes were determined storage. at various tempera- It was found that the volume :rease was the same when ordinary. was employed as when air-free was used the presence of air in the closed sac does not arise air dissolved in the water. On 'other hand, oil caused no swelling at a temperature of 60 ø C. the premise was that the •Swdhng was due to migration of air d: bearing in mind that carbon •i]]i'•ox•de, as so often w•th other plastic •'•materials, diffuses at a rate contra• •':A•C•,!ø: the nomal rate of diffusion as laid by Graham, sacs •ere •led filtered lime water and stored uahous conditions. It was •e•ed •ha• the •x•en• of sweHin• similar to •hat when wa•er alone used bu• it was no•ed tha• fhe surface of fhe polyethylene covered •fh a whi•e deposi• was subsequenfiy identified calci• carbonate. I• was also tha• •he loss in wei•h• was a function of •he in•se in and was •ea•er the hi•her •pera•ure. A further in•eres•- n• obse•afio, was made that if a sac was completely filled with air-free wa•er and s•ored, a bubble of soon made its appearance. The loss in weight and the increase volume of polyethylene sacs con- taining a reverse emulsion were com- pared with bags made with polyvinyl chloride and "Pliofilm" (the "Pho, film" being rubber chloride of Ameri- can origin). The values obtained are given in Table I. It will be seen that with sacs made of p01yvinyl chloride there is a loss in weight but this is not accom- panied by an increase but rather by a slight decrease in volume. In the case of "Pliofilm," there is again a loss in weight accentuated by an increase in temperature and a loks in ' volume. Comparative figures for the polyethylene sacs show that both the loss in weight and the increas• in- volume are, at ordinary temperatures, small. On the other hand, at 37 ø C.: the loss in weight is significant and this, is accompanied by a large., increase in the volume. It should be' remarked that the change in weight and the increase in volume of polyethylene sacs is a straight-line curve, at any rate up to the point when the sac is about to burst. It should be remarked here that in all cases there was some evidence of oiliness on the outside of the sacs ß which was accentuated at 37 ø C. Of the three varieties of film, "Profilm" showed probably the least greasiness, polyvinyl chloride a slightly gr,eater amount and poly- ethylene sufficient to bring about greasing of any absorbent material with which it came in contact., The films used in the above experiments were ordinary commer- cial ones and were of yawing thick- nesses. For example, the "Pliofilm" was 2'5 x 10 'a in., the polyethylene 165

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 5 x 10 '• in. and the polyvinyl chloride 15 x 10 '* in. in thickness. Because of this variation, it is not possible to-make too close a com- parison between the different plastics, but the significance of the results lies in the fact that it is only the polyethylene sacs which show any increase in volume, i.e., diffusion of air into the sac. TABLE I Changes in Weight and Volume of Plastic Sacs containing Water-in-oil Emulsion when stored at various Temperatures • Weight after sto'rage [ Volume after storage Type and • (weeks) (weeks) thickness of '• 0 2 4 6 i 8 0 I 2 4 6 8 film øC gm. gm. gm. gm. gm. c.c. c.c. c.c. c.c. c.c. P.V.C. 20 94-2 93.8 93.0 92.4 91-4 100 100 100 100 99 15 x 10 '* in. 87.3 87-0 86-1 85.4 84.4 94 94 94 94 . .91 ß 37 100.6 97:0 94.5 92.7 90.9 I09 110 110 105 105 . 95'0 92-1 90.2 87.6 85-9 101 103 102 99 100 _. __. Pliofilm 20 110-8 112.1 111-2 110.5 109.2 133 133 133 130 130 2'5 X 10" in. 121'5 120'9 119-0 119'0 117'9 137 137 137 137 137•i • 116'1 115'7 114'4 113'7 112'8 157 157 157 157 151 : 37 125'2 122'9 120'5 117'9 114-2 153 153 150 150 134'9 130'5 128'0 124'8 120'7 153 153 150 150 14•i!!: -- --. Polyethylene 20 75.0 75.2 74-3 73-7 74.0 82 80 88 5 X 10-' in. .,:. 69.1 68-9 67.4 67-4 67-0 75 74 76 78 63.6 63.4 62.0 61-6 62-8 72 70 72 74 37 60.1 58.5 57.5 57.0 56-3 72 '80 90 100 •:: 78-6 78-0 76.5 76-0 74-2 85 94 105 110 ! 74 3 73-9 72.4 71.3 70.3 80 85 96 100 166