Enzymatic modification of polyacrylonitrile and cellulose acetate fibres for textile and other applications

T. Matamá , A. Cavaco-Paulo , in Advances in Fabric Biotechnology, 2010

v.ii.2 Side chains from cellulose acetate equally enzymatic substrates

Acetate fibres are defined as manufactured fibres by the Federal Merchandise Commission of the United states, in which the fibre-forming substance is cellulose acetate (Needles, 1986). Cellulose acetates are classified as derivative cellulose fibres, every bit distinct from rayon and lyocell, which are regenerated cellulose fibres, the chemical composition of cellulose acetate beingness not cellulose but an ester of cellulose (Collier and Tortora, 2001). Each anhydroglucose repeating unit of cellulose (Fig. five.4) has three hydroxyl groups located at the positions ii, 3 and half dozen (La Nieve, 2007). These sites are available for acetylation to produce the acetate fibres. The degree of acetyl-ation or commutation (DS) is the boilerplate number of acetylated positions per anhydroglucose unit. Commercial cellulose triacetate (CTA) has a DS of 2.91–2.96 whereas cellulose acetate has a DS of ≈   two.4 (La Nieve, 2007). Therefore, the denomination of cellulose acetate fibres is used to refer to all commercial acetylated cellulose fibres, but it is also the common proper name for the cellulose acetate fibre with a DS ≈ 2.4. To avoid misinterpretations, throughout this text, the name cellulose acetate will be used to refer to both types of fibres whereas cellulose diacetate (CDA) volition exist used to refer the acetate with a DS of ≈   2.iv.

5.four. Chemical structure of the anhydroglucose repeating unit of measurement of cellulose.

Cellulose acetates are produced from loftier-quality cellulose, such as cotton fiber linters and wood pulps, with an α-cellulose content in a higher place 95% (Saka and Matsumura, 2004). The most usually used commercial acetylation procedure is the acetic acid system where acetic acrid serves every bit solvent for the cellulose acetylation and acerb anhydride and sulfuric acid as catalysts (La Nieve, 2007).

Acetate fibres are soft and cool, accept silk-like aesthetics and skillful curtain, and they can be hands blended with other fibres like silk, rayon, nylon, cotton and polyester (Constabulary, 2004). The moisture regains for CDA and CTA are vi.5% and iii.5%, respectively (Steinmann, 1998; La Nieve, 2007). The CDA has a moisture regain close to the value 7% of natural cotton yarn, whereas the CTA has a lower value but all the same higher than the commercial synthetic fibres. Their unique attributes remain desirable and they are responsible for the survival of acetate production in the competitive marketplace of man-made fibres. Another aspect that is gaining importance is the fact that cellulose acetate fibres are environmental friendly compared with the major synthetic fibres.

Whereas cellulose, either from cotton linters or wood pulp, is highly crystalline, dry-spun cellulose acetates prove very low crystalline order owing to the exchange of the hydroxyl groups by acetyl groups and consequent disruption of the original cellulose construction (La Nieve, 2007). In both CTA and CDA, hydrogen bonding between cellulose chains is substantially decreased and the bulky acetyl group prevents the close packing of cellulose chains (Needles, 1986). The van der Waals forces are the major associative forces between the polymer chains, and their lower magnitude is the reason for cellulose acetate being considerably weaker than cellulose fibres. Both CDA and CTA have a very low strength and their chemical stability is poor (Steinmann, 1998; Collier and Tortora, 2001). They are attacked by a number of organic solvents capable of dissolving esters, strong acids and bases, which result in saponification of acetyl groups. For these reasons, the physical and/or chemical modification of these fibres is of very express apply.

Some methods were adult to ameliorate the strength, abrasion resistance and dimension stability of acetate fibres, in particular of CDA (Steinmann, 1998). Ane arroyo was to apply polymer additives to the CDA spin dope. Several were tested simply, unless their concentration was below 5%, the phase compatibility was poor (Steinmann, 1998). To better the compatibility, some polymers were grafted onto CDA. In the case of acrylonitrile, the graft copolymer increased the compatibility of PAN and cellulose acetate and the resulting fibres had improved thermal and chemical stabilities (Steinmann, 1998). The effect of crosslinking agents was also investigated on CDA, though the improved properties were still not equal to those of estrus-treated CTA (Steinmann, 1998).

Piece of work on the modification of cellulose acetate with enzymes has been done in the context of its biodegradation (Puls et al., 2004). Figure 5.v summarizes the primary reactions expected to occur during the biodegradation of cellulose acetate with special emphasis on the deacetylation reaction. The degradation of cellulose and hemicellulose is naturally carried out by microorganisms and requires the concerted action of many enzymes for their complete destruction. Among those carbohydrate-active enzymes, there is the group of carbohydrate esterases (EC iii.1) that hydrolyse the ester linkage of polysaccharides substitutents. This group is a potential supplier of biotechnological tools to hydrolyse the cellulose acetate fibres in a controlled manner, creating hydroxyl groups at the fibre surface that, besides imparting hydrophilicity, tin can be subsequently modified.

5.5. Principal reactions occurring during biodegradation of cellulose acetate.

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The structure of homo-made cellulosic fibres

J. Ganster , H.-P. Fink , in Handbook of Textile Fibre Structure: Natural, Regenerated, Inorganic and Specialist Fibres, 2009

6.5.2 Crystallinity, crystallite dimensions and orientation

Crystallinities of CA fibres spun in our laboratory and determined by the above-mentioned Ruland–Vonk method were between xiii and fifteen% with disorder parameters k in the range of ane.viii to 2.ii. In contrast, the saponified Fortisan fibre has a crystallinity as high every bit 47% (Table 6.one).

Due to the low crystallinities even compared to the viscose fibres from Table half dozen.ane, no crystallite dimensions could exist determined for the CA fibres. For Fortisan large crystallites with the highest lateral area of thirty.5   nm2 of all the fibres in Table 6.3 are detected.

Chain orientation can be qualitatively assessed by broad-angle X-ray fibre patterns as shown in Fig. 6.16. It is clear from the X-ray diagrams that CA fibres are very different with their weak crystalline reflections as well as their complete baggy halo which accept only minor increased intensity in the equator region. This means weak anisotropy and a very low degree of chain orientation for the existing CA fibres.

half dozen.sixteen. Ten-ray flat moving picture photographs of (a) viscose, (b) cellulose tyre string yarn, (c) Lyocell, and (d) cellulose acetate fibres.

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An introduction to fibre construction

W.E. Morton , J.W.Due south. Hearle , in Concrete Properties of Textile Fibres (Quaternary Edition), 2008

1.5.3 Cellulose acetate

In acetate fibres, the most of import of the chemically modified cellulose fibres, the cellulose is chemically treated in solution so that the hydroxyl groups are replaced by acetyl (CH3  ·   CO   ·   O—) groups. In ordinary commercial acetate (more exactly known as secondary cellulose acetate), about five out of six of the hydroxyl groups are replaced in this style. Fibres fabricated of this fabric contain a smaller proportion of crystalline material than do regenerated celluloses. At that place are iii reasons for this reduction in crystallinity: (a) the acetyl groups are comparatively inert, hydrogen bonding is not possible, and thus the attractive forces between the molecules are weaker; (b) the acetyl groups are beefy, preventing the shut arroyo of the concatenation molecules; and (c) the structure is irregular, with some acetyl and some hydroxyl groups protruding from the chain, and then preventing the formation of a regular crystalline club. As a consequence of these effects, acetate fibres are weaker, more extensible, and less dense and absorb less water than cellulose fibres. They as well have a depression softening signal, whereas unmodified cellulose fibres cannot exist melted and decompose first.

The large-scale production of secondary cellulose acetate was largely a historical blow arising from difficulties in the early on processing of a fully acetylated cellulose. These difficulties have been overcome, and triacetate fibres, in which all the hydroxyl groups are replaced by acetyl groups, accept been produced. Considering of the greater regularity of construction, these fibres are more highly crystalline than ordinary acetate fibres. They also absorb less water because of the removal of all the hydrophilic hydroxyl groups. Their applied advantages are a college softening betoken, greater dimensional stability, and the fact that materials made from them are crease-resistant and tin can be heat-gear up.

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An introduction to cellulosic fibres

D. Ciechańska , ... D. Wawro , in Handbook of Cloth Fibre Structure: Natural, Regenerated, Inorganic and Specialist Fibres, 2009

ane.1.6 Acetate and triacetate fibres

The term acetate fibres relates to fibres made from cellulose acetate. The divergence between acetate and triacetate fibres lies in the number of cellulose hydroxyl groups that are acetylated (Table one.2). Cellulose acetate was the first man-made thermoplastic fibre.

These fibres are quite different from viscose and are characterized by high elongation at pause and poor abrasion resistance, though resistance to pilling is very skillful, and they can be textured. The dry out strength of the two types is similar, though triacetate fibres have college forcefulness in the wet state. The main terminate-uses for the filament yarns are in linings, dress vesture and household furnishing. Staple acetate fibres are the major product used for cigarette filters. The biggest cigarette filter tow producer in Europe is Rhodia Acetow GmbH in Freiburg, Germany.

Triacetate fibres are used in sportswear, garments and woven fabrics that continue their shape. Due to their depression moisture absorption, fabrics made from them are hands washed and dry very quickly. Fabrics made from blends of triacetate and wool are very popular, combining advantageous properties of both types of fibres: the warmth of wool and the baste-dry properties of triacetate [7].

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Laundry performance of fabrics and garments

L. Lau , J. Fan , in Engineering Apparel Fabrics and Garments, 2009

Acetate

The smoothness of acetate fibres helps to produce hygienic fabrics that shed dirt and wash easily. However, acetate loses force temporarily when moisture, so information technology must be handled gently during washing. Avoid wringing or twisting acetate fabrics when they are moisture, because the resulting wrinkles and creases are hard to remove. Acetate is thermoplastic, and therefore the h2o temperature and ironing temperature should be carefully controlled.

Some problems still be with colourfastness of disperse-dyed acetates. Some dyes are sensitive to gas-smoke fading; hue changes occur in fabrics exposed to atmospheric contaminants, such as oxides of nitrogen and ozone. The problems are more than prevalent in areas with loftier concentrations of atmospheric contaminants. In homes with gas heating, it is advisable to brand sure that acetate decorative fabrics have been treated with inhibitors to prevent smoke fading. iii, 7

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Dyeing with disperse dye

J.Due north. Chakraborty , in Fundamentals and Practices in Colouration of Textiles, 2014

18.11 Gas fading of disperse dyes

Polyester, triacetate and acetate fibres dyed with anthraquinoid disperse dyes possessing primary or secondary –NH2 groups in structure show fading effect on exposure to N2O gases or other fumes. This happens when either primary –NH2 groups are diazotised or secondary –NHii groups are converted into nitroso compounds. The problem can be solved by treating manmade textiles with chemicals possessing affinity for fibre having general formula R1R2N(CH2)nNRaneR2 during or before dyeing or by introducing electronegative groups in place of –NHtwo groups. Azo disperse dyes mostly remain stable against gas fumes except few blue dyes.

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Tensile properties

West.E. Morton , J.West.Southward. Hearle , in Concrete Properties of Fabric Fibres (4th Edition), 2008

13.v.3 Regenerated cellulose and related fibres

The stress–strain curves of rayon and acetate fibres show an initial rapid rise with a marked yield point, followed past a nearly flat portion and a rising again every bit breakage approaches. The curves vary widely for different types of rayon and different manufacturing methods. Differences are due to the spinning method and the degree of stretch imposed. A highly stretched fibre, such as the formerly produced Durafil, has high molecular orientation, which gives high strength and low extensibility, similar to the bast fibres. Rayons used for apparel are weaker and more extensible.Tyre-cord rayons, such equally Tenasco, are intermediate in value.

The issue of orientation is conspicuously shown in the set up of curves in Fig. xiii.19, for acetate of varying degrees of orientation. If cellulose yarns are regenerated from the acetate, every bit they were in Fortisan, the locus of strengths is somewhat college. Acetate fibres are, in general, weaker and more extensible than viscose rayon fibres. The load–elongation curves of acetate fibres, measured at constant rate of elongation, often show a drop after the yield signal.

13.19. Stress–strain curves of filaments of varying degrees of orientation. The dotted curves are secondary cellulose acetate and the full curves are cellulose fibres regenerated from acetate. The lowest curve in each set is for unoriented material.

 From Piece of work [45].

There are also important differences in the tensile properties of viscose rayon, depending on their fine structure. An improvement in structure will cause the whole locus of breaking points to exist moved farther from the origin, so that strength is increased without the loss of extensibility that occurs when orientation is increased. This is illustrated in Fig. 13.20, and the great advances that were made in hightenacity rayon tyre yarns in the 1950s are shown in Tabular array 13.6. More than extensible analogues of these fibres are used equally high-forcefulness staple fibres. Rayons made until the 1950s had a micellar structure, which results in a depression-moisture-modulus and a low strength equally shown later in Fig. 13.26.

13.20. Load–extension curves for viscose rayon, showing changes produced by increasing orientation and improving structure.

Tabular array 13.6. Properties of viscose rayon tyre cords.

Blazon Tenacity (Northward/tex) Breaking extension (%)
Textile rayon 0.xix 20
Tenasco 0.30 x
Tenasco 35 0.35 x.5
Tenasco 70 0.36 13.5
Tenasco Super 105 0.47 12.5

From Wilkinson [46]

13.26. True stress–strain curves for polyester fibres spun at different speeds: (a) with strain based on as-spun length, (b) with curves translated to an equivalent initial depict-ratio.

 From Perez [sixty].

The modal rayons, which include polynosic fibres, are fibrillar in texture, and are stiffer, and closer to cotton in backdrop, than earlier rayon fibres (see Fig. thirteen.21). They have a high-wet-modulus and better wet forcefulness. The reasons for this are discussed in Department 20.ii.2. Lyocell fibres, such as Tencel, are similar in tensile properties, only somewhat stronger and stiffer. White et al. [47] requite dry out tenacities and break extensions of 0.38–0.42   N/tex at 14–16% dry and 0.34–0.38   N/tex at 16–18%.

13.21. Stress–strain curves of lyocell (Tencel), modal and regular viscose rayon compared with cotton wool.

 From Courtaulds Lyocell Overview.

Chamberlain and Khera [48] investigated the variation in the backdrop as the outer layers of viscose and cuprammonium rayon filaments are removed chemically. A typical result for viscose rayon is shown in Fig. 13.22. 1   t appears from these results that the outermost layers are less extensible than the layers below the surface, but the variation in tenacity cannot exist worked out, since the stress would concentrate in the least extensible parts of the fibre. The results for cuprammonium rayon were different for the 2 samples of fibre tested.

13.22. Change of tenacity and braking extension of viscose rayon as outer layers are removed.

 From Chamberlain and Khera [48].

From reports past different workers, Muri and Brown include tenacities North/tex and intermission extensions of 0.154/14.5% and 0.183/ six% for calcium alginate fibres and 0.204/10% for zinc alginate [49].

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Building Decorative Fiber Fabric and its Products

In Building Decorative Materials, 2011

2 Chemical Cobweb

Chemical fiber is classified to bogus fiber (viscose fiber and acetate cobweb etc.) and synthetic fiber (polyester, acrylic, chinlon, urethane elastic fiber and polypropylene cobweb etc.)

1)

Viscose cobweb. Viscose fiber is classified to bogus cotton wool, artificial silk and artificial wool. It is non stain-resistant or article of clothing-resistant, and easy to crease. Usually it is mixed with other fibers and used every bit window mantle or cushion fabric.

ii)

Acetate fiber. It has light stability, incombustible and non like shooting fish in a barrel to pucker. Information technology has silk-like advent and is mainly used equally window curtain.

3)

Polyamide fiber (chinlon). Known equally nylon before, besides called chinlon, its advantages are corrosion-resistance, easy cleaning and unique functioning of habiliment resistance. The disadvantages are low elasticity, easiness to catch dust and to deform, getting partly molten in burn etc.

iv)

Polyester fiber (terylene). It has good wear-resistance, which keeps the aforementioned either in wet state or in dry state. It is less likely to crimple, and with light and heat-resistance. It is composite with many other fibers and cotton yarns to make sheets and curtains etc.

v)

Polypropylene fiber (pylen). It has advantages such as lightweight, high strength, skilful elasticity, mildew-proof and moth-proof, easy cleaning, good wear-resistance and lower production cost.

6)

Polyacrylonitrile fiber (acrylic). Information technology is light, soft, moisture-proof, mildew-proof, mothproof and thermal preservative, with good elasticity and resistance to acid and alkali corrosion; it has the reward of light-resistance, which is unique and unequalled with natural fiber and most synthetic fibers.

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Biodegradable nonwovens

1000. Bhat , H. Rong , in Biodegradable and Sustainable Fibres, 2005

Cotton/cellulose acetate biodegradable nonwovens

The first studied biodegradable cotton wool-based nonwoven fabrics were produced by cotton and ordinary cellulose acetate (OCA) fiber. Bonding temperatures used here for thermal calendering are 150°C, 170°C, and 190°C based on the ordinary cellulose acetate's high softening temperature (Ts: 180–205°C). The tensile strengths along machine direction of the bonded fabrics are listed in Tabular array 10.4 . Nonetheless, the tensile strength of the nonwoven fabric made with cotton wool/cellulose acetate nonwoven alloy is quite depression and is non suitable for consumer application when it is processed nether the temperatures associated with cellulose acetate'south softening temperature (180°C–205°C). Solvent handling has been introduced in order to modify the softening temperature of cellulose acetate cobweb and to lower the calendering temperature, while maintaining enhanced tensile properties. Acetone, a good solvent for cellulose fiber, was considered a choice in the solvent pre-treatment. Xx pct acetone solvent pre-treatment was and then applied for cotton fiber/cellulose acetate nonwovens to subtract the softening temperature and further lower the calendering temperature [24]. The results showed that these solvent treatments tin can subtract the softening temperature of cellulose acetate cobweb and produce comparatively high tensile strengths as shown in the data in Table 10.4. Even so, from a practical standpoint, manufacturers practice not similar to have a process involving the apply of acetone since acetone evaporates easily, and is flammable and toxic. These detrimental factors may crusade big issues in manufacturing and pollute the working environment. Also, consumers may non prefer to purchase acetone treated products.

Table 10.iv. Peak load for cotton/cellulose nonwovens (kg)

Bonding temperature (°C) Binder component 25% Binder component fifty%
Cotton wool/OCA 150 0.10 0.03
(No treatment) 170 0.09 0.03
190 0.09 0.09
Cotton wool/OCA 150 0.21 0.20
(With 20% acetone solvent treatment) 170 0.34 0.47
190 0.69 0.65
Cotton/OCA 150 0.21 0.25
(With water dip-nip treatment) 170 0.37 0.44
190 0.81 0.77
Cotton wool/PCA 150 0.17 0.25
(No treatment) 170 0.33 0.42
190 0.63 0.90
Cotton/PCA 150 0.52 0.57
(With h2o dip-nip treatment) 170 0.eighty 0.86
190 0.81 0.87

Thus, two culling methods were further practical for cotton/cellulose acetate nonwovens [25]. H2o dip-nip treatment was further used instead of acetone solvent pre-treatment to make the process more surroundings friendly. Comparing the effect of water dip-nip treatment with acetone solvent treatment, it can be constitute that there is no significant difference betwixt water dip-nip treatment and twenty% acetone solvent treatment and pinnacle load of cotton/cellulose acetate thermally bonded webs are enhanced past both the treatments. Based on these data, water tin can be used as an external plasticizer instead of 20% acetone solvent without compromising web strength and the process is environment friendly.

From the point of free energy business organization, information technology is ameliorate to make the whole process as simple as possible. And so a plasticized cellulose acetate fiber, wherein an internal plasticizer was added during cobweb manufacture to lower the softening temperature of ordinary cellulose acetate and further lower the bonding temperature during thermal calendering process. Information technology tin exist conspicuously seen from the information (Table 10.iv) that peak load has been improved by using PCA instead of OCA, peculiarly at higher bonding temperature. Further comparison of external plasticizer (h2o) and internal plasticizer shows that in that location is no significant difference betwixt using external plasticizer and internal plasticizer. Thus, it is evident that an internal plasticizer (PCA) tin exist used in place of the external plasticizer (water) without compromising spider web strength, and the procedure is more than economic. Based on the higher up assay, it seems that the optimal processing conditions are either for cotton fiber/OCA with water dip-nip treatment or cotton fiber/PCA without treatment bonded at 190°C for both the blend ratios. The optimal strength of the biodegradable nonwovens is around 0.8   kg.

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Structure, characteristics and types of fiber for textile product design

Y.E. El Mogahzy , in Applied science Textiles, 2009

eight.5 Regenerated synthetic fibers

Another serial of fibers used in traditional fibrous products are regenerated fibers. These include rayon and acetate fibers. In Chapter 2, the story of rayon development was presented; it marked the kickoff of unlimited development of constructed fibers. In comparison with cotton, conventional viscose rayon exhibits junior physical properties as a result of its lower degree of polymerization and lower crystallinity. Regular viscose rayon fibers have medium strength, low modulus and high elongation. New developments resulted in many derivatives of regenerated fibers with meliorate concrete properties (east.grand. high tenacity and loftier wet modulus viscose). Acetate fibers are fabricated from cellulose acetate polymer solution. This fiber is relatively less durable than other fibers as it exhibits poor force and poor abrasion resistance. Regenerated fibers are mostly used in apparel products such equally blouses, shirts, dresses, shirts and slacks, and lining fabrics for suits and coats.

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