Showing papers in "Sen-i Gakkaishi in 1968"

THE STRUCTURE OF SILK FIBROIN-α

Abstract: In the preceding paper the results of electron microscopic examination on the precipitates Fcp and Fcplx are reported. The former was obtained from the aqueous solution of silk fibroin (bombyx mori) hydrolyzed by chymotrypsin, the later being obtained when the former was dissolved in cupri-ethylenediamine and dialyzed. Fcp and Fcplx showed the structures of beta-fibroin and alpha-fibroin, respectively.To examin further the structure of alpha-fibroin, the sedimented mat of Fcp 1x was prepared and submited to the X-ray diffraction measurements.A clear fiber diagram was not obtained from X-ray diffraction pattern of a Fcp 1x mat, but were led to assign the following rectangular unit cell to the alpha-fibroin: a=4.59 A (direction of hydrogen bonding), b=7.20 A, c=9.08 A (fiber axis), This unit cell includes one polypeptide chain and the polypeptide molecule may take a helical conformation of four-fold, where the residue translation should be 2.27 A.X-ray diffraction photographs of the mat of Fcp 1x and thin film adilute (0.1%) solution of regenerated silk fibroin shows long periods beginning with a spacing of 48.2 A as well as the ordinaly periods. At the present moment no definite relationship between the two kinds of the period is found. One plausible explanation would be that the log periods are caused by the globular structure formed by folded molecules.Infrared absoption spectra indicates the existence of beta-structure for the Fcp. In Fcp 1x, no sign of the presence of alpha-helix is detected, but the feature of the spectra is close to that of the random coil structure.

Studies on the dissolution of silk fibroin

Abstract: It is well known that silk fibroin dissolves in the concentrated aqeous solution of neutral salt such as CaCl2 or LiBr. In this study, Some alcohols were added to the CaCl2 solution, and the dissolution of fibroin in the solution was investigated. It was found that the addition of a proper quontity of monohydric alcohol, such as CH3OH and C2H5OH improves the shlubility. C2H5OH is more effectives for the increase sf the solubility than CH3OH under equal molar addition. The addition of dihydric alcohol (C2H4(OH)2) or trihydric alcohol (C3H5(OH)3) decreases the dissolution of silk fibroin.

COMPARISON OF α-FORM SILK FIBROIN WITH MODEL SUBSTANCES

Abstract: The unit cell dimension of α-form silk fibroin was determined. The α-form of β-poly (Ala-Gly) and β-poly (-Ala-Gly-Ser-) synthesized as the model substances are examined for comparison with the α-form silk fibroin.By comparison of, the following values for unit cell of α-form silk are obtained: a=4.45A b=28.0A (fiber axis) c=7.16A. 12 amino acid residues are to be in the unit cell, and so the mean repeating distance of one aminoacid of one amino acid residue is 2.4A.This value indicates that the chain length of amino acid residue in α-form is shorter than that in β-form.

The vapour pressures, heats subimation and associated entropy changes of disperse dyes

Abstract: The vapour pressures, latent heat of sublimation and associated entropy changes of eight anthraquinone derivatives, six diphenylamine derivatives and seven azobenzene derivatives have been measured by the Knudsen's effusion method. The heat of sublimation and associated entropy changes for two main derivatives of anthraqinone and diphenylamine is discussed in terms of molecular structure, based on the assumptions of additive property of energy and exsistence of hydrogen bond, and the following results have been obtained.1. The heat of sublimation for 1:4-diamino- and 1-amino-4-hydroxy-anthra-quinones are 2 and 1.2 Kcal/mol greater than that of anthraquinone respectively.2. The heat of sublimation of 1- and 2-aminoanthraquinones is 3.8 and 11.3 Kcal/mol greater than that of anthraquinone respectively, and an increase of these values is chiefly due to the intermolecular hydrogen bonds.3. The heat of sublimation of 2-nitro- 4-nitro- and 2:4-dinitro-diphenyl amines is 2.2 and 7.8 Kcal/mol greater than that of diphenylamine respectively. and an increase of these values is due to the increase in polarity.4. The heat of sublimation for 4′-amino- and 4′ hydroxy-2:4-dinitrodiphenyl amine is 1.8 and 5.3 Kcal/mol greater than that of 2:4-dinitrodiphenylamine respectively, and an increase of these values is chiefly due to the intermolecular hydrogen bond.

Studies on the relationship between orientation mechanism and mechanical properties of oriented polypropylene

Abstract: The thermal expansion of (hk0) lattice spacing of quenched crystal and (040) and (110) lattice spacings of monoclinic crystal, as well as the orientation behavior of crystalline and non-crystalline phases of quenched, semi-annealed and well-annealed specimens of isotactic polypropylene with uniaxial stretching at various temperature, were investigated by means of simultaneous measurements of x-ray diffraction and birefringence.Abrupt change of thermal expansion coefficient of the crystal lattice spacings was found at 48 and 115°C for the quenched and monoclinic crystals, respectively. The former temperature may correspond to the beginning of melting of the quenched crystal, because of unusual value of the coefficient as large as 10×10-4deg-1 for the (hk0) lattice spacing beyond the temperature, while the latter corresponds to a sort of crystal disordering temperature of the monoclinic crystal.For the quenched specimen, the orientation of the quenched crystal (c-axis) and non-crystalline chain segment proceed more prominently at 20°C. than 50 °C. This inferior orientation at 50°C. may be interpreted in terms of partial melting of the quenched crystal, which gives less effective orienation of the crystal and non-crystalline chain segment during stretching. Crystal conversion from quenched to monoclinic system is found for the high-temperature stretching.For the annealed specimens, the orientation behavior of a′- and b- axis of monoclinic crystal, in which the negative orientation of a′-axis is always behind that of b-axis at relatively low degree of stretching and coincide with each other at a relatively high degree of stretching, is quite similar to that of b- and a-axis of polyethylene. This behavior may be interpreted in terms of deformation mechanism of polymer spherulite and disintegration of spherulite texture to the fibre. Upon comparing the orientation behavior at 20°C. with that at 120°C. the negative orienttation of b- and a′-axes proceed more prominently at 20°C, than at 120°C. at relatively low degree of streching, and vice versa at higher degree of stretching. This temperaturee sensitive behavior, especially at the relatively low degree of stretching, is also very similar to that of polyethylene, and may be interpreted in terms of the easiness of crystal slippage along (040) plane due to the abrupt change of interaction betweeen the crystal planes at the crystal disordering temperature.

Asymmetric temperature distrisution of melt-spun filament

Abstract: A numerical method is given for calculating asymmetric temperature distribution to fiber axis within a filament quenched by cross air flow in the course of melt spinning. And the results of numerical calculation shown in Fig. 9 are obtained for a special spinning condition.It is shown that temperature distribution of spinning filament can be obtained by measuring that of a model cylinder being cooled by cross air flow under the condition of eq. (14-2). Interval τm after of cooling in the model test is connected with distance z from spinneret by eq. (13).The structure (birefringence, density) differentiations across the cross-section of polypropylene and polyester spun fibers are measured and related to the asymmetric temperature distribution of spinning filament.

Heat of fusion of isotactic polypropylene crystals in monoclinic form

Abstract: This paper intends to evaluate the heat of fusion of isotactic polypropylene crystals in monoclinic form by thermal analysis and the method of x-ray diffraction. A whole polymer having viscosityaverage molecular weight _??_v=1.93×105 and three fractions (_??_v=1.47×105, 1.75×105 and 6.31×105, respectively), insoluble in boiling n-heptane, were moulded into 0.1mm thick film, and then, annealed at the temperature ranging from 120°C to 165°C by using the descending temperature method in similar manner as that described in the previous paper (K. Kamide, M. Sanada; Chem. High Polymers, Japan, 24, 662 (1967)). Heat of fusion ΔH, x-ray crystallinity Cx and density were measured on the slowly-cooled film after annealing. From the relationships among ΔH, Cx and density, ΔH=ca 33cal/g for crystals with Cx=100% was obtained irrespective of molecular weight and molecular weight distribution, respectively.

On a simple equation of obtaining diffusion coefficient within a fibre in the case of an infinite dyebath

Abstract: There are two equations to evaluate the rate of dyeing from a finite dyebath, one of which is a exponential form A=A∞(1-e-Kt), where A is the percentage of dye adsorbed at a time t, A∞ the equilibrium exhaution and K a velocity constant.In this paper, this equation is expanded to the case of an infinite dyebath, and a simple equation to obtain the diffusion coefficient within a fibre is derived.The equation is:-ln(1-Ct/C∞)=5.85Dt/r2+0.346 where Ct is the amount of dye adsorbed at t, C∞ the amount at the equilibrium, D the diffusion coefficient of dye and r the radius of the fibre.This logarithmic equation agrees with that of the Hill's and also experimental results, provided Ct/C∞>0.5.Applying this equation, C∞ can be calculated from adsorption data at some arbitrary short times with an accuracy which is sufficient for most purposes.

Studies on the decomposition of aminoanthraquinone disperse dyes by irradiation of light in various organic solvents

Abstract: The purified aminoanthraquinone disperse dyes, such as 1-amino-, 2-amino-, 1, 4-diamino-, 1, 5-diamino-, 1, 4-bismethylamino- and 1, 4-bisbutylaminoanthraquinone, were exposed to the irradiation of xenon arc lamp in various organic solvents, and the changes of their spectra were measured.The rate of fading reaction was accerelated markedly by the substitution of hydrogen atom of amino group by methyl or n-butyl group. By exposing of the dyes to the light a new absorption band in visible region was not developed in benzene, acetone and t-butylalcohol, but remarkably developed in ethyl alcohol, isopropyl alcohol and n-propyl alcohol at the blue side (λmax; 500 and 460mμ). The same band was observed by the reduction of the dyes with sodium hydrosulfite. Both the photochemical product and the chemical reduction product from aminoanthraquinones had the same Rf value (0.48).These facts show that the fading reactions of the dyes in alcohol having α-hydrogen atom are photoreductive, and the intermediates can be assigned to the corresponding anthrahydroquinones.

On the affinity, heat of solution and heat of dyeing of disperse dyes from organic solvents

Abstract: In order to know dyeing properties and the mechanism of disperse dyes in three different solvents, measurements of the solubilities of disperse dyes in octane, n-buthylalcohol, and water and pertition coefficients from these solutions, have been made at the temperatures of 80°, 90° and 100°C. Affinities, heat of dyeing and heat of solution have been derived. From these values, the absolute heat of association of the dyes with the PET-substrate (ΔHabs) has been estimated, and the following results have been obtained.1. The greater the values of solubility, the smaller the values of affinity irrescective of solvents.2. The higher the values of inorganicity/organicity of dyes, the greater the solubilities of dyes in water, but the smaller in the case of octane.3. It is suggested from the values of ΔHabs (23_??_35 Kcal/mol) that dispersion force between aromatic nucleus of PET molecule and aromatic or anthraquinone nucleus of dye molecule makes a considerable part of contribution to the dye-PET interaction, and additionally, dipole-dipole interaction or hydrogen bond makes a contribution to interaction.

Studies on the dyeing properties of nylon 6 fiber

Abstract: The adsorption of dye (1) (Acid Red 18) and dye (2) (Direct Blue 71) on to Nylon 6 fiber in equilibrium under different pH range of dye solution was investigated.Above mentioned Nylon 6 fibers consist of three kind of fibers which include 9.5×10-5 mol, 5.4×10-5 mol and 2.5×10-5 mol of amino end group per lgram of fiber respectively.The dyeing was carried out at 90°C and at 2.0_??_10.5 pH value.The following resulted; The adsorption of dye (1) and dye (2) onto Nylon6 fibers is dependent on the amount of amino end group, but the degree of adsorption of dye (1) is different from dye (2). In the former the degree is larger than that of the latter and the adsorption of dye (1) is nearly equal to the content of amino end group, on the other hand the adsorption of dye (2) had far low equilibrium value.Isotherm of dye (1) showed a typical Langmuir's curve and that of dye (2) showed H-type curve at pH value 3.5These facts may be explained as follows; the nonpolar force contributed to the dyeing mechanism of dye (2) to the main part of the adsorption of dye (1) is attributable to the salt-linkage and that of dye (2) is to the hydrogen bond orvan der Waal's force. But it is not clear that the reason for low adsorption of dye (2) is due to a large molecular weight or not.

The structural changes of undrawn polyethylene threphthalate fibers by ageing

Abstract: The aging effect on the fine structure has been investigated of the undrawn PET fiber melt spun by means of differential thermal analysis (DTA), dilatometry, density, birefringence, load-extension and dynamic mechanical measurements.The results obtained on the aged sample are as follows:1. An endothermic peak in DTA apears at a lower temperature than T_??_, which suggests that a destruction of the fine structure originated by aging is producted at the very temperature.2. An abrupt extraordinary voluminal expansion in dilatometry is observed in response to the temperature where the endothermic peak in DTA curve appears. It may be related to the volumeric relaxation which occurs in aging.3. Necking stress increases with aging time and an yield point appears in a further drawing after the necking. It suggests the formation of stronger intermolecular bonds by aging.4. A very small increase is observed in density. The results (1), (2) and (3) suggest that this small increase in density is due to the increase in the density of amorphous region but not due to the crystallization.5. The location of β absorption maximum of mechanical tan δ shifts to the side of a lower temperature, which means that the local mode motion of COO groups is made easier by ageing. Birefringence decreases as the ageing time increases.From these results the effect of aging on the fine structure of PET is considered to be explained as follows:The volumeric relaxation is produced in an amorphous region, accompanying the increase in the intermolecular bonding energy. On the other hand, the decrease in restraint of a molecular chain accompanied by the volumeric relaxation gives a favorable effect on the local mode motion and shifts the β absorption maximum of tan δ.

A thoretical consideration on the fluorescence method for the study of molecular motion and transitions in polymers

Abstract: The principle of the fluorescence method for the study of rotary diffusion is reviewed briefly. Then, from the fundamental equations, a few modified relationships which are important for the practical use are derived.Discussions are made on the distribution of relaxation time, and the rectangular distribution function of relaxation time is introduced. The mean relaxation time (ρG) is discussed as a function of the degree of polarization of fluorescence (P) or the quantum yield of fluorescence (φ).From these observations it is to be concluded that too small a value of activation energy may be obtained, if the equations of uni-relaxation time are applied to the system having comparatively wide distribution of relaxation time.

Crystallization of regenerated silk fibroin (bombyx mori) from its aqueous solution

Abstract: Silk fibroin was regenerated from a concentrated lithium bromide solution. Conditions for the crystallization of the silk fibroin from its aqueous solution were investigated by means of optical rotatory dispersion and X-ray diffractometry.The conformation of the silk fibroin was confirmed as coiled when regenerated at different temperatures (40_??_100°C). The silk fibroin showed the α-form structure when cast and dried at temperatures lower than 40°C, and the β-form structure when cast and dried at 40°C or over. No concentration (of silk fibroin) effect was observed.By extruding very viscous solution of 15% fibroin through a tepered nozzle, a thread of silk fibroin was obtained. This, however, showed no birefringence, indicating an unoriented structure.

Stadies on the dissolation of silk fibroin

Abstract: It is well known that silk fibroin dissolves in the concentrated aqueous solution of neutral salts. In this study, the process of the solubility was investigated from the view point of the fine structure of silk fibroin. The following results were obtained on the dissolution in the CaCl2-H2O solution.(1) The maximum solucility of silk fibroin is given under the condition CaCl2:H2O=1:8(mol).(2) The apparent activation energy obtained from the Arrhenius equation is about 27kcal/mol.(3) When silk fibroin is dissolved by CaCl2-H2O solution under the proper condition, first the amorphous part is dissolved, then the semicrystalline, and finally the crystalline region.

On the spherulites of silk fibroin

Abstract: On the formation of spherulites in silk fibroin gel obtained from fresh silk gland, the conditions for crystallization such as pH and temperature and the structure of the spherulites resulted under these conditions were examined.1. Spherulites of silk fibroin were observed at temperatures lower than 50°C and the range of pH from 3.0 to 10 except in pH 5.0. This prohibition of spherulites formation at pH 5.0 may be consistent with the fact the pH is about 5.0 in the living silk gland where the crystallization is not permissible.2. Silk fibroin spherulites is confirmed to be α-form structure by X-ray diffractometry.Surface structure of spherulites is similar to that of many other linear polymers under electron microscope.The needle crystals which are often found in silk fibroin film coincide with β-form structure of silk fibroin.

Molecular motion and transitions in various types of polyamides studied by the fluorescence method

Abstract: Microbrownian motion in polyamide chains is studied by the fluorescence method. In the first place, the validity of the estimation of molecular motion is studied. The relaxation properties of fluorescent polyamide (diamino stilbene-conjugate or DAS-conjugate in contraction) are compared with those of the usual nylon-6 in which free fluorescent dye (auramine-O or diacetylamino stilbene) is dispersed. In the dilute solution they give different relaxation times and the apparent activation energies. However, in the concentrated solution and especially in solids, either sample gives almost the same relaxation time and apparent activation energy.Then, in the next place, the molecular motion and the transition in various types of bulk polyamide are studied using auramine-O as a probe. Transition temperature varies almost linearly with CED of the material, and the extrapolation to polymethylene gives the limiting value much higher than the glass transition temperature of polyethylene. Apparent activation energy also depends on CED.Other properties such as dynamic modulus and X-ray parameters are compared with the fluorescence parameter. The effects of water on the relaxtion properties is also studied.The mechanism of the transition is discussed on the basis of these experimental studies.

Molecular confomations of silk fibroin in silk gland

Abstract: Molecular conformation of the coagulated fibroin in silk gland was studied by means of X-ray diffractometry and infrared spectrometry. It was ascertained by the infrared dichroism the coagulated silk fibroin in posterior gland has the parallel β form. However most of the fibroin in posterior gland appears in random coil. The α-β transition occurs at the anterior part of posterior division. Neither α-helical structure nor cross-β- structure was seen in the fibroin molecules of this middle division. The structure of α-form of silk fibroin is similar to polyglycine II with its hydrogen bonds projected out perpendicularly to the polypeptide chain.From these structures, it may be expected that α--β transformation in silk fibroin molecules occurs easily without serious rearrangement of the hydrogen bond. The X-ray powder diagrams of silk fibroin in anterior division indicate β-form structure.It may be considered that the α-form structure of silk fibroin molecules are broken to form partly β-form while passing through the anterior silkgland.

Studies on the bamboo dissolving pulp

Abstract: Using the X-ray diffractometer, crystallinity index (Cr. I.) was measured on the bomboo dissolving pulp as well as linter and wood pulps. Crystallinity index, proposed by L. Segal, changed a little according to the extent of prehydorlysis and sulfate cooking, however, Cr. I. of the bamboo pulp was nearly exual to those of wood pulps.The bamboo pulp was treated with 8-18% NaOH solutions in the same way as with linter and wood pulps and regenerated with acetic acid solution. The degree of mercerization of the samples was determined quantitatively by the X-ray diffractometer using standard mixture samples of linter and its mercerized pulp. The bamboo pulp does not mercerize so easily as wood pulps, though not so hard as with linter pulp. Mercerization is retarped with temperature. This was observed on the bamboo and wood pulp, when these pulps were treated with 14% NaOH solution.The difference of behavior at mercerization between the bamboo and wood pulps with nearly equal degree of crystalligation was supposedly due to in the fine structure, especially in the lateral order.The charactaristic behavior of bamboo in mercerization should be considered our practical preparation of alkali-cellulose for viscose.

Improved dyeing of vinylon by introduction of functional groups to oxidated vinylon

Abstract: In the previous study on sulfo-acetalization of vinylon and the dyeing of the acetalized vinylon, it was pointed out that vinylon treated with sulfuric acid was dyed with basic dyes. This effect may be due to the bonding sulfuric acid, for it has tendency to adhere to C-C double bond or carbonyl group in polyvinylalcohol. It was assumed from this that the addition of sodium bisulfite to the double bond or carbonyl group originated with oxidation of vinylon may be effective for introducing acid groups to polyvinylalcohol.The treatment of oxidized vinylon with sodium bisulfite was found to be very practicable for dyeing with basic dyes. In the case of amino-group-introduced-vinylon the same circumstance was observed for dyeing with acid dyes.Bromine or potassium bichromate is very effective as an oxidizing agent. The latter is less efficient in oxidizing than the former. Vinylon oxidized with bromine was treated with sodium bisulfite and then dyed with some basic dyes. The dyed goods have good fastness against light such as acrylic fiber. The vinylon oxidated with potassium bichromate was treated with ammonia or mono-ethanolamine and then dyed with metal-complex, sulfide or Indanthren dyes. The dyed goods have remarkable advantages in the high yields of colours and good washing fastness.Foundamental formula of those reactions are as follows:

The effects of tension in heat setting of nylon 6 fibers

Abstract: The effects of the tension in heat setting on the fine structure were studied for nylon 6 fiber. The fine structure is much affected by tension, especially the degree of molecular orientation of amorphous region. The following facts were observed.The tension in heat setting of nylon 6 fibers has no considerable effect on the degree of crystallinity, whereas it exerts influence on the amorphous region.Wide angle X-ray diffraction shows a little change in crystallite orientation after heat setting even though much shrinkage occurs.In the phenol solution of equal concentration, the fibers which the shrink during heat seting swell along fiber axis, though the extended fibers shrink. By this swelling properties, it suggested that some of the molecules in the amorphous region change from the elongated to the folded conformation when the heat is set under zero tension.The diffusion velocity of dye in fiber becomes very low by tension in heat setting, though the saturated amount of dye at equilibrium does not change greatly. The orientation of molecule in amorphous region is increased remarkably by the tension in the heat set. And the diffusion coefficient of dye in fiber has linear relation to the orientation factor of molecule in the amorphous region.The tension given in heat setting has very important bearing upon the dye-ability. These results indicate that it is very important to keep tensile condition exact for heat setting process of nylon 6 fiber.

Regeneration of cellulose from liquid sulfur dioxide solution and some properties of the regenerated cellulose

Abstract: In the previous paper, it was reported on the preparation of cellulose liquid sulfur dioxide solution in the presence of secondary or tertiary amines. In the present work, cellulose is regenerated from cellulose-triethylamine-liquid sulfur dioxide solution in a form of the model filament under various conditions. Some properties of these filaments were investigated comparing with those of viscose model filaments.Clear and uniform filament was obtained by dry spinning in cooled atmosphere or wet spinning using cooled methanol (-10°C) as coagulating and regenerating bath. Meanwhile, in the case of wet spinning using acetone or NaCl-HCl aqueous solution (-10°C), cellulose was regenerated as milky white and non-uniform filament. From the above observations, it is clear that phat physical conditions such as the elimination of sulfur dioxide in the coagulating bath have an extremely great effect on the characteristics of these filaments.The characteristics of the fine structure of the model filaments were studied by X-ray diffraction water and Iodine sorption methods. From these examinations, it is recognized that the filament regenerated in methanol or acetone is highly accessible (crystallinity: 12_??_18%, accessibility: 89_??_93%. calculated from water sorption data), and the X-ray diffraction pattern is similar to that of amorphous cellulose, while the filament regenerated in water is less accessible than the filaments regenerated in methanol or acetone (crystallinity: about 26%, accessibility: about 86%). Therefore, it is confirmed that the regenerated cellulose from liquid sulfur dioxide solution is more amorphous comparing with viscose model filament (crystallinity: about 34%, accessibility: about 81%).These fresh filaments are also anisotropical for the shrinkage (the degree of shrinkage to the cross direction for fibre axis: 50_??_60%, longitudinal direction: 26_??_37%). While cellulose is coagulated by the elimination of sulfur dioxide, the cellulose gel may shrink to the cross direction for fibre axis, and consequently these filaments may have the above anisotropical property.

Studies on the relationship between orientation mechanism and mechanical properties of oriented polypropylene. (8) interpretation of orientation behavior of polypropylene crystals during uniaxial stretching of bulk polymer in terms of spherulite deformation mechanism

Abstract: The orientation behavior of crystallites during uniaxial stretching and its recovery behavior during heat-treatment without tension for highly isotactic as well as lowly isotactic polypropylenes, are interpreted in terms of a spherutlite deformation mechanism modified from that proposed by Sasaguri, Yamada and Stein.Four deformation parameters characterizing the spherulite deformation mechanism, i. e., fraction of the folded-chain type crystal within crystal lamella at undeformed state, easiness of crystal transition from folded-chain type to fringed-micellar type and that from fringed-miceller type to folded-chain type, and easiness of lamella detwisting, showed reasonable changes with degree of tacticity of the polymer, conditions of annealing and stretching of the bulk polymers.The prefered orientation recovery of crystal c-and b-axis than a′-axis during heat-treatment of stretched bulk polymer without tension, may be interepreted in terms of almost reversible deformation recovery of the spherulite and that of lamella detwisting, but irreversible crystal transitions between fringed-micellar tye and folded-chain type.

An analysis of loop formation process on weft-knitting machine by means of knitting force

Abstract: In this paper, the effects of input yarn tension and shape of stitch cam on the loop formation process by latch needles, are analyzed by the knitting force. Experiments were performed using 5 kinds of stitch cam shown in Fig.1, changing the input yarn tension from 2 to 16g. Results obtained are as follows:1) The length of yarn knitted into the loop depends upon the robbing back and upon the yarn elongation in the knitting zone. The yarn elongation must not be ignored even in the cam system where the cam system where the robbing back occurs.2) The robbing back occurs in the region of loops which are held by one or two needles just passed the knitting point. The region differes depending upon the properties of the yarn used.3) The wider the region and the larger the knitting force (the input yarn tension), the greater is the amount of yarn robbed by one needle from another.4) The robbing back is affected by the variation of the frictional behavior of needles, which causes the vertical streaks in the knitted fabric.