Gupta, V D

Prakash, Anand

English

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X -R A Y  STUDY OF CRYSTALLITE ORIENTATION IN AGAVE AMERICANAANAND PRAKASH a n d  V T). GdPTAPjivsics D ei’ABTmunt, University or Allahabad, A llahabad {Heceivcd, May 20, 11)00)Plato VIABSTRACT. I<’ollo\viiip Iho melliotj oullmod by r . H tTomuiuh tind oihms, a (jfiuin- titaiivD study of rrystallito orionUiiion m ugavo uuioi'idanii Obro umlor vhuohh ]»Iiysj(ia] coiidi- tiouh IS caniod oul. Jt is Ibimd that unlik<' many ol-luu c’cIJuIosl* fibic-s, tJir ononlaliuii of tlio L'l’ysiallitos Jii agavo unioi-icami Hlu)^ vs improvomont on Iioaliuont wilh NaOU- 'Plus is asvnl)od to (hr removal of some iritoiorystnllino constituenls.-Because of thoir textile importance cellulose fibres of diflerciit kinds and origin arc probably the most extensively investigated ol all the natural materials. They arc known to oeenr as Natural, Bast and Leal fibres. The determination of crystallite orientation in a particular type of leaf fibre-agave ameiicana forms the subject matter of the prosiMit investigationThe problem of eryslalbtc oriciilation in fibres is not oidy of theoretical interest but also ol practical imx»oriance as many of tboir jibysical and chemical properties arc correlated with jt. A quantitative investigation of the problem has been attempted by iSisson and (hark (UI3I1), Berkley (1931)), H. Kosemanu (1937) and Hermans and Rermaus (19d6) 3'he problem has lieen stuflicd both from X-ray and optical metliods. The X-ray method is more nsetul because (qitical methods furnish information merely as to the average orientation of the entire fibrous substanee, M^ hercas the X-ray method gives orientation of only the crystallite components. Tt is in ihis restricted sensi; ol orientation that a quanti­tative estimation by means of X-ray methods is made.The intensity distribution along an X-ray iuter%eucc c,irclc Irom a poly- cvystalline specimen in Avliich crystallites are oriented in some way, oflers a pos­sibility to investigate the orientation properties ol the material. This was first pointed out and the foundations for such investigation w'ere laid by Polanyi (1921). Since that time a very large number of orientation investigation has been jiublished dealing with inorganic and organic materials of crystalline and seim-cryBtalline nature. Following Hermans, and Hermans, the orientation factor is determined by the equation34/ . - I +  ain%)299(I)300 Amnd Prahash and V. D. Guptawhere and ^ 2  angular distances along the equator for two paratropicinterferences arising from planes approximately at right angles to each other. In taking averages along the arcs we assign weights G{^) cos and 0{fi) cos ^ 2  the value of ^  according to the shape of the intensity distribution I  =  G{fi). Thus ^ J /c o s ^ d y / 'However, since in those cases where (lOl), (021) overlap the intensity curve for (101) alone can not he doterrained, the following formula is used instead of (1)u  =  1.245 1.72 Sin^ yff -  2.06where /< is the angle along the (101)—(021) circle relating to the total intensity of two overlapj)ing interferences. This is based on K — 0.83 !'E X P E R I M E N T A LRaw leaves of agave americana were retted as usual and the fibres obtained where thoroughly washed, dried and combed to ensure parallelism. Filtered CuK!j, radiation from a Seifert’s scaled tube working at 38 KV, and 18 inA was used with a specimen to film distance of 5 cm. and the specimen size, exposure time and photographic technique were standardised as far as possible. The photo­meter used was Moll’s recording type The film was cut into a circular disc of 4.5 cm diameter and it was mounted on a rotatable holder fixed to the stage of the microphotometer so that the rotation which could be made in stops of 2'’ arc took place about the centre of the photograph. At each setting the film was scanned radially by traversing the holder. Since the films were of low photo­graphic density it was assumed in the calculations that the X-ray intensity was proportional to blackening and was thus linearly related to the logarithm of the intensity of transmitted light. The results obtained arc given in Table I.TABLE ISuiiiple Sin"/3i SiniijSj f xNativB Fibro .041 .Oflfi .aryWhen treated with 18%NaOH  and dried without ten.sion .026 .0406 . 0 0Treated with 1B% NaOH and dried under tension .016 .014 .96Native fibre boiled with 2%HjjS04 band mercerised with 18% NaOH — 0.75DISCUSSIONAgave americana fibres are stiff, bright and comparatively thicker than jute in the native form. On treatment with caustic soda solution the strength1 AKASH & GUPTAIndian Journal of Physics, Vol. XXXIV, No, 7PLATE VI(h)0) (d)Fig. 1, X -ray photogiaph  of the fibre (a) Native fibic(bi T ieatcd  with 17% N aO H , washed and dried w ithout tension(c) Same as above when dned  under tension(d) Dolled with 2% H 2SO4 and thenmei censed .X-Ray Study of Crystallite Orientation, etc. 301of the fibre gradually decreases which is evidently due to the removal of ligiiiu and other intercrystalline materials which may also be responsible for an ineomploto morcerisation. This is clearly seen from the X-ray photograph of the fibre treated with 18% NaOH (Plate VI). The photograph is a mixed one. Tlic partial reconversion of the cellulose to tlie native modification can as well he ascribed to the formation of crosslinks between cellulose chains in the neighbourhood of tli^ e crystallites and thus creating a disposition in favour of the ret urn i;0 the' original configuration after swelling. This seems to be supported by tJie fact that the degree of moroerisation is more pronounced in a sample which us boiJetl with 2% HaSOi before being mercerised because it loosens the crosslinks. There is, however, also the possibility of the removal of some intejvrystallino constituents which effect meroerisation. Another iiitereBting obscrvalkm made about agave aniericana is that the crystallites are better oriented as a result of the treatment ivith NaOH. This may again be due to the removal of those mtercrys- talline materials which iniiicdo the rotation and alignment of the crystallites. Ht)%vevcr when the fibre is first boiled with and then mercerised, the orien­tation decreases. This shows that the damage done on treatment faroutwanghs the improvement in orientation when NaOH alone is employed.A detailed study of agave aniericana from the scattering of X-rays at small angles and by employing the tdchnicjues of oloctron microscopy is also being made and woll bo shortly reported.A C K N O W  L  E D Cl M E N T SThe authors are extremely grateful to Prof. K. Bauerjee, D.Se,, F.N 1., for his constant encouragement and guidance throughout the progress of this work. One of the authors (A.P.) is also thankful to the Council of Scientitic and Industrial Research for the financial aid.R E E E K E N CE SBerkley, E. E., 1939, T extile , R en ea rch  J o u r n a l , 9, 33r).Hosomann, 11., 1937, S^. P h y s i k .  C h e m .f  179A, 356.Hermans, J. J., Hermans, V .  H ., et a l . , 1946, Jier. T r a v . C fn m ., 65 427, Polanyi, M.. 1921, Z .  P h y s i k . ,  7, 149.Sisson, W . A. and Clark, O. L.,1933, I n d .  J£iig. C h e m ., A n a l .  E d . 5, 296.

X-Ray Study of Crystallite Orientation in Agave Americana

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X-Ray Study of Crystallite Orientation in Agave Americana

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