Abstract
The studies on effects of thermal treatments on physical properties of the cellulosic fibers were continued to investigate effects of water on the physical properties of thermally treated cellulosic samples described in Part 1, since the participation of water can not be ignored.
Investigations were successively carried out by observing tensile strength, elongation and swelling volume of the cellulosic samples thermally treated and followed by conditioning at 98 % RH to compare with those conditioned at 65% RH for an overall observation of combined effects of heat and water on tensile strength and elongation of cellulosic fibers.
In higher humidities, thermally treated cotton showed a remarkable increase in tensile strength as well as in elongation because of a synergic effect of hydrogen bonds newly formed in the amorphous region by the thermal treatment and water molecules absorbed also in the amorphous region resulting in the formation of high order structure of cotton fiber.
While in the case of viscose rayon, the water molecule gives a decrease in tensile strength but the thermal treatment contributes to increase in tensile strength to some extent through reduction of water content brought about by hydrogen bonds formed by the thermal treatment and left unbroken even after conditioning in any high humidity.
In lower humidities on the other hand, contribution to increase in tensile strength is dominated by hydrogen bonds newly formed by heating, therefore, viscose rayon showed a considerable increase in tensile strength only if the water content is kept low, while cotton showed a reduction of increase in tensile strength without an aid of water.
Furthermore, polynosic showed an intermediate behavior between cotton and viscose rayon in addition to similarities to both cotton and viscose rayon, but a typical behavior of polynosic is a markedly large reduction of tensile strength observed at 200°C and higher probably because of thermal and chemical degradations of the fiber.
In most cases, elongation showed a correlation with tensile strength.
