Factors in Molding CELLULOSE DEIRIVATIVES E'
rliGINEERING applications for cellulose derive tive plastics &re expanding for wartime uses. Changes in plastic iomulations to meet these new requirements have new i t a t o d modification of molding techniques ior such materials. As an approach to determining the effect of variations in molding, it was decided to study the varied strain patterns produced in heevy molded tostpieeesmade under different molding conditions. It is widely believed that the properties of molded tbermoolssties. eaveciallv with r e a d
Swain in wanalucent eelluloae acetate injeetion-molded or sheet-stock plastics eppears related to plastics temperatures, pressures mold (or chase) tempuatures, retea of filling mold (injection), and solvent content (sheet stock). Strain pattern- as evidenced by placing the molded piece8 between crossed Polamid films have bpn photographed. High temperature and pressures pmduee pieces of minimum strain pattern, closest mold reproduetion, and heaviest weight. Lor rate of filling mold aids in forming bubble-free pi-. Side gating is more dative than comer gating in producing pieces relatively free of strain. S o l v e n t wntent in block prior to baking, baking temperature, and cooling pressure are oritid factors in achieving strain-free eellulose wetate ebeet atock.
W . 0. Bracken and F. E. Piech HERCULES WWDER COMPANY. PARUN. N. I.
-the sample being placed between tho &wiving plates. MATERIALS AND EQUIPMENT
injection molding..' A PM-and an FM type (56.0% combined acetie mid) were uaed in the sheeter WOC-. Basic formulations. m p i
