Cellulose Orientation, Strength and Cell Wall Development of Cotton Fibres

Abstract

IIP possible effects of thin-walled, or so-called &dquo;immature,&dquo; T fibres on the precisioa of the X-ray method for estimating' the teiixile strength of raw cotton have been studied and are reported in this paper.The materials were obtained., for the most part, from a cotton field of the North Carolina State Experiment Station at Haleigh, during the summer of ] 9~n. Cotton flowers were tagged on the day of opening and the bolls were collected periodically. In the X-ray studies, four different series of samples from Mexican Big I3oll cotton and one each from Hopi and Sea Island cottons have been used. The samples were taken at daily intervals during the period of fibre elongation a,nd until after secondary thickening was initiated and at one to five day interyals iij) to 45 days and a final sample after the bolls opened.Tensile strength, and per cent thin walled fibres were determined on a limited number of samples selected from the several series of the Mexican Big Boll cotton.Measurements of the 002 rings of the X-ra,y diffraction patterns of the fibres containing primary wall only, showed a tendency for preferred orientation of the b-axis of the unit cell, 1:.e.,' the long axis of the cellulose molecules, transverse to the fibre axis. Microscopic studies under polarized light also showed that the cellulose of the primary wall lies transverse to the fibre axis.at University of British Columbia Library on June 30, 2015 trj.sagepub.com Downloaded from 356 As the secondary wall was laid down, the 002 ring of the X-ray diffraction pattern became equally dark throughout, and with continued deposition of cellulose the region of greatest darkening of the ring shifted 90 degrees from that of the primary wall. In one series of samples the patterns showed a gradual change from the condition of transverse arrangement of the cellulose in the primary wall through an intermediate stage to a more parallel arrangement in the secondary wall. The other three series of Mexican Big Boll cotton showed rather abrupt changes; that is, the transverse arrangement was pronounced on one day, whereas on the following day parallel or spiral arl'angemellt was noted.What could be interpreted as random orientation of the cellulose was not observed in any of the six series of samples at any stage of development. The apparent random orientation reported in one series was due to the superimposition of layers of differently oriented cellulose in the primary and secondary walls. The &dquo;wax&dquo; pattern was more prominent than the cellulose pattern during the stage when the cell contained only the primary wall. Preferred orientation, with the long axis of the wax molecules transverse to the fibre axis, was indicated by promiment rings in the wax pattern. These waxy substances were readily extracted from the Mexican Big Boll cotton with alcohol but slowly, if at all, with chloroform or carbon tetrachloride.The cellulose pattern of the primary wall and the wax pattern both disappeared (became too thin to be differeiitiated from the backgroun...

Pectic substance of cotton fibers in relation to growth

“…' From about the 35th day until the boll opened, the content of pectic substance underwent little change, as indicated by the third segment of the curve. This is in agreement with the findings of Berkley [7], who also showed that no significant change in the ratio of thin-to thick-walled fibers occurred during this period-a fact which indicates that no appreciable change in wall thickness is occurring. The upper curve was obtained from uronic acid analysis; the lower curve by isolation of the pectic substance as Its calcium salt.…”

“…The second segment of the curve confirms such an interpretation and further indicates the rate at which the development of the secondary wall proceeds. This interpretation is also in accord with the work of Berkley [7], in which it was shown that in cotton fibers similar to those used in this work, the secondary cell wall underwent a rapid thickening between the 18th and 35th days of growth. An examina-tion of the change in the percentage of cellulose with the age of the fiber further substantiates these views.…”

Microscopic structure of the cotton fiber

“…This change was evident upon examination of the fibers with crossed nicols and a selenite plate, as well as by observation with ordinary light, and is in agreement with the results of the X-ray work of Berkley [18].…”

The Use of Iodine Adsorption as a Measure of Cellulose Fiber Crystallinity

“…Since the green dye has a slower dyeing rate and its molecules are twice as large as those of the red dye [5], the reason the immature fiber dyes green would seem to be greater accessibility or lower crystallinity. The fact that fiber taken from immature bolls and dyed before crystallization takes place [1] dyes green is additional evidence that the immature fibers are of a lower crystallinity order, as measured by the iodine adsorption method.…”