Rayon Fibers Research Articles

Effect of spinning conditions on physical properties of a composite yarn

This study investigated the effects of spinning conditions such as traveller, twist multiplier, front top roller pressure and hardness on the physical properties of 19.7 tex Polyester/Rayon (P/R) composite yarns. Results showed that a traveller of #1/0, twist multiplier of 2.8, front top roller pressure of 18 kgf and hardness of 70° are the optimum spinning conditions. This combination results in the best mixing of spreaded polyester filaments and drafting rayon fibers in the nip of the front rollers, arranging them in the best dispersion to form a P/R composite yarn with better quality and good blend uniformity. The results also showed that the 19.7‐tex composite yarn spun in this study is superior to the world 5 % for standards of uniformity and hairiness. This indicates that the quality of P/R composite yarn has been remarkably improved.

Color stability and colorant effect on maxillofacial elastomers. Part III: Weathering effect on color

Maxillofacial prostheses are serviceable for approximately 6 months, after which they need to be refabricated because of the deterioration of color and physical properties. This third article in a 3-part series evaluated the color stability of commonly used colorant-elastomer combinations as a result of exposure to weathering. Fifteen specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorants (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no colorant) for a total of 270 specimens (18 groups of 15 specimens). The 15 specimens of each elastomer-colorant combination were separated into 3 test condition groups (control, time passage, and natural weathering) of 5 specimens per test condition group. Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Color and optical density data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among test conditions (control, time passage, and weathering). When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05. Changes in color, as a result of weathering, were noted in many of the colorant-elastomer combinations. Also, color change occurred not only to the colored, but also to uncolored materials over time without exposure to weathering. Clinically, the addition of colorants could have a stabilizing effect on the elastomer color when it is exposed to weathering.

Color stability and colorant effect on maxillofacial elastomers. Part I: Colorant effect on physical properties

The average clinical life span of a maxillofacial prosthesis is approximately 6 months, at which point it needs to be refabricated, mainly because of degradation of the color and physical properties of the prosthesis. This first part of a 3-part study evaluated the effect of coloring agents on the physical properties of maxillofacial elastomers. Five dumbbell-shaped and 5 trouser-shaped specimens were fabricated for each of the combinations of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorants (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants), for a total of 180 specimens. Evaluations of hardness and tear strength were made with the trouser-shaped specimens. Evaluations of the ultimate tensile strength and the percentage elongation were made with the dumbbell-shaped specimens. A within elastomer analysis compared the 6 colorants using a 1-way analysis of variance for each of the 4 physical properties. When significant differences were observed, the Student-Newman-Keuls multiple range test was used to identify differences between groups at a significance level of.05. Physical properties of maxillofacial elastomers were changed by the incorporation of coloring agents. Dry earth pigments, kaolin, and rayon flocking acted as a solid filler without bonding to the Silicone, and artists' oils and liquid cosmetics acted as a liquid phase without bonding to the silicone matrix. No clearly superior colorant-elastomer combination was demonstrated in all the tests in this study.

Color stability and colorant effect on maxillofacial elastomers. Part II: Weathering effect on physical properties

The clinical life of a maxillofacial prosthesis averages about 6 months, before it needs to be refabricated. Degradation of the color and physical properties of the prosthesis are the principle reasons for replacement. This second part of a 3-part in vitro investigation evaluated the change in physical properties of popular colorant-elastomer combinations as a result of weather exposure. Fifteen dumbbell-shaped and 15 trouser-shaped specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorant combinations (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants) for a total of 540 specimens. The 15 dumbbell-shaped and trouser-shaped specimens of each elastomer colorant combination were separated into 5 of each shape among 3 test condition groups (control, time passage, and natural weathering). Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural-weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Evaluations of hardness and tear strength were made on trouser-shaped specimens, and evaluations of the ultimate tensile strength and percentage elongation on dumbbell-shaped specimens. Physical property data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among the test conditions. When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05. Exposure to weathering and time changes of the physical properties of many colorant-elastomer combinations indicated that properties of a clinical prosthesis can change with time. The addition of colorants to the silicones altered the effects of weathering. In addition, the silicones were not as stable as previously assumed.

Cross-Sectional Structure of Composite Yarns

This work investigates the effect of spinning conditions such as traveller, twist multiplier, and front top roller pressure and hardness on the cross-sectional structure of 19.7 tex T/R composite yarns. A traveller of #1 /0, a TM of 2.8, and a front top roller pressure of 18 kg and hardness of 70° are the optimum spinning conditions. This combination results in the best mixing of spread polyester filaments and drafting rayon fibers in the nip of the front rollers, arranged in the best dispersion to form a T/R composite yarn with better quality and good blend uniformity. The results reveal that the 61.5% asymmetrically sided type is the predominant cross-sectional structure of T/R composite yams. However, the fraction of the uniform distribution type increases from 10.0 to 24.5%. indicating that the blend uniformity of T/R composite yams improves remarkably.

Lenzing overcomes adversity—for now

After racking up net losses in 1996 and 1997, Austrian rayon fiber producer Lenzing turned in a net profit for the first six months of 1998. Benefiting from a series of restructuring moves made late last year, the company cautiously predicts an overall profitable 1998. But Lenzing tempered its self-congratulation with the warning that it may not be entirely out of the woods. In fact, some industry observers consider Lenzing—which claims to be the world's largest cellulosic fiber maker—a hardship case that still needs a lot of care. The world economic slowdown took its toll on Lenzing early on and continues to adversely affect the company's prospects. When the Asian economic crisis began more than a year ago, Lenzing's Indonesian rayon operations were hard hit because of low selling prices in local currency and the drop in the value of that currency relative to the dollar. The company instituted a cost-control program and wrote ...

Swelling behavior of stimuli-responsive cellulose fibers

Environmental scanning electron microscopy (ESEM) and dynamic contact angle (DCA) measurements showed to be a powerful combination for investigating the swelling behavior of stimuli-responsive cellulose fibers in various environments. The stimuli-responsive fibers were prepared by ozone-induced graft polymerization of acrylic acid onto regenerated cellulose fibers. Atomic force microscopy (AFM) in the tapping mode showed that a smooth polyacrylic acid layer covered the fiber surfaces. X-ray mapping of sodium atoms by EPMA/EDS (electron probe micro analyzer/energy dispersive spectrometer) analysis showed that NaOH-treated grafted polyacrylic acid was evenly distributed, not only at the surface but also in the cross-section of the fiber. By using ESEM, it was possible to vary the humidity around the fibers in a controlled manner and to study a controlled fiber swelling at high magnification. It was observed that the fiber swelling was dependent on the degree of crosslinking of the cellulose-supported hydrogel. Dynamic contact angle measurements using the Wilhelmy plate technique proved to be another technique for studying the swelling behavior of the grafted single fibers. A pH-sensitive swelling, with a perimeter increase from 122 μm at pH 2 to 228 μm at pH 5, was established for the acrylic acid-grafted rayon fibers.

Biological monitoring of workers exposed to carbon disulfide (CS2) in a viscose rayon fibers factory.

The exposure-excretion relationship to carbon disulfide (CS2) vapor in 407 exposed workers was studied during the second half of the working week. Carbon disulfide concentrations were also determined in 50 nonexposed subjects. The geometric mean value for CS2 in urine samples from the latter was: 0.23 microgram/l (95% upper limit = 0.52 microgram/l) when log-normal distribution was assumed. Among the exposed workers, the CS2 level in urine samples collected after the first half shift exceeded the 95% upper limit of nonexposed subjects in every case. The time-weighted average intensity of exposure to CS2 vapor was measured using personal diffusive samplers (in which carbon cloth served as an adsorbent). CS2 concentrations in urine were determined in samples collected at the end of the first half shift from the 407 exposed cases as well as from 50 nonexposed controls. There was a significant correlation (p < 0.0001) between the exposure to CS2 vapor at concentrations of up to 64 mg/m3 and the levels of CS2 measured in the urine samples after four hours of exposure. The correlation indicated that a mean level of 15.5 micrograms CS2/l urine (95% confidence range, 13.8-17.1 micrograms/l) was excreted following an exposure to CS2 at 31 mg/m3 (the current occupational exposure limit).

Biological monitoring of workers exposed to carbon disulfide (CS2) in a viscose rayon fibers factory

Biological monitoring of workers exposed to carbon disulfide (CS2) in a viscose rayon fibers factory

The effect of additives on the mechanical properties of dry-formed fibre networks

The effects of thermal bonding and friction-changing additives on the mechanical properties of dry-formed cellulosic networks have been evaluated. Calcium carbonate particles and a cationic surface active agent were used to change the coefficient of friction of cellulose (Chemothermo mechanical pulps; (CTMP) and rayon fibres. The parameters used to describe the networks were the storage modulus G′0 (measured at low strain amplitudes) and the critical strain γc (at which the network yields) obtained from the dynamic–mechanical measurements and the maximum force Fmax measured with a shear tester. The mechanical properties of the networks were improved as a result of the thermal bonding, which promotes stress transfer through the network structure. The friction-changing additives changed the ability of the fibres in the network to disentangle before the network ruptures. This change was, in the first place, reflected in corresponding changes in the critical strain γc and the maximum strength Fmax of thd dry-formed networks. © 1998 Chapman & Hall

A Study on Solid Structure of Regenerated Cellulose Fibers Related with Fibrillation.

It is well known that the Cupro®, Polynosic and organic solvent span rayons, such as Tencel®, and Lyoce® fibers are easy to fibrillate. The Rayon fiber is difficult to fibrillate. We developed fibrillation-resistant Cupro(CUPRO2) by means of a new spinning method. In this study, we attempted to compare the solid structures of CUPRO2, Cupro (CUPROl), Rayon(RAYON) and Lyocel (LYOCEL) in order to discover the factors governing the fibrillation. To this end, WAXD, Dynamic viscoelastic analysis, and CP/MASS13 CNMR analysis were carried out. The measured fibrillation resistance grade was as follows: RAYON (95)>CUPRO2 (75)>CUPRO1 (40)>LYOCEL (10). Crystallinity index, degree of crystallite orientation, and apparent crystallite size estimated for the (1_??_0) plane decreased with increasing fibrillation resistance grade. The peak temperatures of α1 and α2 dispersion (Tmaxα1, Tmaxα2) measured from the mechanical loss tangent-temperature curve increased in order of the fibrillation resistance grade, that is to say, the inter-and intra-molecular hydrogen bonding seemed to increase with increasing fibrillation resistance grade. It may be concluded.that the fibrillation characteristic is greatly influenced by the degree and strength of inter-and intra-molecular hydrogen bonding in the amorphous region at the surface of the microfibril.

Rheological characterization of dry-formed networks of rayon fibres

The viscoelastic properties of low-density dry-formed fibre networks have been evaluated by dynamic mechanical measurements in shear. The fibres used were rayon fibres of different diameters (13, 30 and 60 μm) and lengths (2, 4 and 6 mm). The effects of network density and grammage on the viscoelastic properties of the network were demonstrated. An important objective of this study was to assess relations between mechanical properties and fibre or network characteristics. The primary mechanical parameters used to describe the networks were the storage modulus G0′ measured at very low imposed strain amplitudes (in the linear region) and the critical strain γC at which the network yields significantly. It was noted that if the network is to be able to withstand high deformations it should exhibit a high value Of γC, which in turn, is promoted by a short free segment length between fibre crossings and a large number of contact points per fibre in the network. Long and thin fibres provide an advantage in this context. The modulus G0′ appeared to be related to the ratio of the free segment length to the fibre diameter. A lower value of this ratio corresponds to a higher G0′ value and an improved load transfer through the network structure. The networks studied here should in general be regarded as weak compared with other types of networks, e.g. paper.

Effect of cloacal plugging on microbial recovery from partially processed broilers

Experiments were performed to test the contribution of bacteria contained in the intestinal tract of broilers at the beginning of processing to counts on the exterior of modified New York-dressed carcasses. Thirty-two birds were processed for each of seven replications. Within each replication, batches of four birds were electrocuted, scalded, and picked, with batches alternating between treatment and control groups. Treated birds were cloacally plugged with rayon fiber tampons prior to electrocution to prevent escape of intestinal contents during scalding and picking. Control birds were processed in the same manner, except that cloacal plugs were inserted immediately after defeathering to reduce escape of intestinal contents during sampling. Gram-negative enteric bacteria and Campylobacter spp. were enumerated on carcasses by whole carcass rinse procedure and in cecal contents. Counts were converted to log10 and subjected to analysis of variance. Cecal levels of Gram-negative enterics were significantly higher for plugged birds, but there was not a significant difference between levels of cecal Campylobacter spp. between treatment groups. Plugging before electrocution resulted in significantly lower levels (2.5 vs 3.0 log10 cfu/mL) of Campylobacter spp. and Gram-negative enteric bacteria (3.0 vs 3.4 log10 cfu/mL) in carcass rinses of treatment birds than in those of controls. All carcasses were positive for Gram-negative enterics. Cloacal plugging resulted in significantly lower incidence of Campylobacter spp. carcass contamination as determined by chi-square. Intestinal carriage of both campylobacters and Gram-negative enteric bacteria appears to influence the microbial quality of the carcass during processing.

Study of local stress, morphology, and liquid-crystal alignment on buffed polyimide surfaces

The magnitude of local stress applied to a polymer surface in the buffing process, which is a critical method to uniformly align liquid crystals for displays, has been evaluated from the polarizing optical microscopic investigation of nematic liquid crystals in contact with polyimide surfaces which were suitably buffed in order to visualize the individual tracks of the buffing rayon fibers. The estimated magnitude of local stress is most likely to be far greater than the yield stress of the polymer film, thereby causing permanent molecular orientation along the buffing direction. The surfaces of poly(amic acid) and cured polyimide films, subjected to different buffing and cure profiles, have been examined by atomic force microscopy. The ability of these buffed polymer surfaces to align nematic and chiral smectic C (ferroelectric) liquid crystals were also investigated. These studies show that the presence of microgrooves on buffed polymer surfaces is not necessary for alignment of liquid crystals. The contribution of polymer molecules from the buffing fibers, deposited and oriented on the polyimide surfaces during buffing, can also be ruled out. Rather, it is concluded that the liquid-crystal alignment is mainly caused by the anisotropic interactions between liquid-crystal molecules and the polymer segments oriented through plastic deformation, with little contribution from frictional heating. For the alignment of smectics, both the degree of order and mechanical properties of polyimide films are found to be important factors.

Modification of cotton, rayon and silk fibers by radiation induced graft co-polymerization

Methylmethacrylate (MMA) has been grafted onto cotton, rayon and silk yarns by irradiation with 60Co gamma source in the presence of methanol used as swelling solvent at different proportions with the bulk monomer MMA. The highest grafting occurred with silk (35%) followed by rayon (22%) and the least grafting was with cotton yarn (17%). Dose rate 200 krad/h was found to yield the best results at a total dose of 500 krad. Incorporation of minute amount (1%, v/v) of an system enhanced both grafting and tensile strength of the grafted yarn. It appears that the coadditive plays a better role in the grafting process for enhancing tensile strength. Water uptake and equilibrium moisture content of the grafted yarns were determined.

繊維の表面処理による高機能化 環境対応型繊維

繊維の表面処理による高機能化 環境対応型繊維

A morphological examination of ceric ion and preirradiation acrylic acid‐grafted rayon fibers

AbstractUsing the ceric ion and preirradiation methods, acrylic acid was grafted to rayon. The fiber used was large denier (50) continuous filament, particularly suited for examining changes in morphology and properties. The grafted fiber was given decrystallization treatments involving ZnCl2 and NaOH. Optimization studies conducted to seek maximum graft with minimum homopolymer formation has been published elsewhere.1 Also published earlier were the results of changes in mechanical and physical properties of the fiber resulting from the grafting and decrystallization treatments.2 Presented in this article are the results on the effects of these treatments on the structure and the morphology of the fiber. The structural features examined were the molecular orientation, crystallinity and crystalline orientation, and the surface morphology. Based on the results of this study and those of the earlier2, it was possible to develop and propose a model of fiber structure that fits the present fiber. © 1994 John Wiley &amp; Sons, Inc.

Effects of carbon fibers on the transcrystalline interphase in poly(phenylene sulfide) of different molecular weights

Composite films of different molecular weight poly(phenylene sulfide) (PPS) and three types of carbon fibers (Pitch, PAN, and Rayon-based fibers) have been studied by optical microscopy and wide-angle X-ray diffraction. Transcrystallization of growing spherulites on carbon fibers is found under all thermal conditions of growth on Rayon and Pitch-based carbon fibers for all types of matrices. For composite films with PAN carbon fibers transcrystallization of growing spherulites is not uniform and sometimes is not found at all. Existence of b axial orientation of twisted lamellae for transcrystalline zone of PPS is demonstrated by X-ray diffraction technique and compared with orientation of the stretched sample. The new induction time quantitative approach is applied to the transcrystalline growth of PPS spherulites on the surface of carbon fibers. The interfacial free energy difference for fiber/crystallite and heterogeneities/ crystallite systems in the melt that is defined from growth and nucleation stud...

Adhesion characteristics of oxygen plasma-treated rayon fibers

The effect of oxygen plasma treatment of fiber on the adhesion between regenerated cellulose fiber and polyethylene (PE) was investigated using the single-fiber fragmentation test. In addition to allowing the determination of the interfacial shear strength, the fragmentation test provided a great deal of useful information on shear stress transfer and failure mechanisms in the systems. It was found that oxygen plasma treatment considerably enhanced the interfacial adhesion, as established by both the shear strength values that were measured and the birefringence patterns observed. The influence of the duration of treatment on adhesion was studied and found to be a very important parameter. The roles of surface chemistry, surface energetics, and surface topography of fiber in the interaction balance were investigated using electron spectroscopy for chemical analysis (ESCA), contact angle measurements, and scanning electron microscopy (SEM). It was seen that neither the plasma-induced changes in the surface energetics nor those in the surface topography could have exerted a positive effect on adhesion. Instead, the improved adhesion was ascribed to covalent bonds formed between the fiber and the matrix, as hydroperoxides, which were created on the fiber surface by the plasma treatment, decomposed during the fabrication of single-fiber specimens.

差別化レーヨンとその改質の一例

差別化レーヨンとその改質の一例