抄録
The fibrous cellulose triacetate which is made by the vapour phase acetylation, has almost 100mol% acetylation degree and its film or fiber is brittle due to the crystallinity and molecular symmetry. In order to improve this defect, the primary acetate should be ripened introducing somemol% OH group usually.
The brittleness could be improved by fibrous mixed esterification in vapour phase i. e. acetylation-propionylation or acetylation-butyrylation of cellulose.
In order to measure the brittleness, Sakurada-Tsuji's impact tester of pendulum type was used and influences of acetylation degree, draw ratio or heat-treatment of the acetate film upon its impact strength were investigated.
Tensile strength, ultimate elongation, yield value, Young's modulus, toughness and resilience were obtained from the SS-curves of unfractionated or fractionated triacetate, ripened acetate and mixed ester films, and influences of draw ratio, acetylation degree or _??_ upon the mechanical. properties were investigated.
(1) Log of impact rupture energy obtained is linear-proportional to impact velocity, the height and inclination of the straight line are related to the brittleness of the film.
(2) Tensile strength, Young's modulus, yield value, toughness of unfractionated triacetate film increase with draw ratio and ultimate elongation decrease, and resilience is almost invariable.
(3) Tensile strength, ultimate elongation, yield value, toughness of fractionated triacetate film increase with _??_, Young's modulus and resilience decrease.
(4) Tensile strength, Young's modulus, yield value and resilience of ripened acetate or mixed ester films increase with acetylation degree, ultimate elongation and toughness decrease.
