Nylon Lecture Materials PDF

Nylon History Nylon was the first manufactured SYNTHETIC fibre. It emerged out of the basic chemical research carried out by a team led by WALLACE CAROTHERS of the Du Pont company in USA. Starting in 1928 Carothers led a team investigating the production of polymers that might be used as fibres. Thi...

Nylon History Nylon was the first manufactured SYNTHETIC fibre. It emerged out of the basic chemical research carried out by a team led by WALLACE CAROTHERS of the Du Pont company in USA. Starting in 1928 Carothers led a team investigating the production of polymers that might be used as fibres. This was around the time when scientists were beginning to understand more the structure of polymers, so Carothers had a scientific basis for his work. Initially the team synthesized a variety of POLYESTERS, but their properties were unsuitable for fibre production or plastics. They then turned to POLYAMIDES. The turning point came in April 1930, when JULIAN HILL, a young research chemist, withdrew a glass rod he had poked into a reaction mixture to find several strands of substance adhering to it. It stretched to several times its original length, and in the process, seemed to become stronger, before a commercially viable product was achieved. In 1938 the first product using nylon, Dr. West’s Miracle Toothbrush’, appeared. Nylon stockings were seen for the first time in 1939. Most of the nylon produced at this time was used in place of silk for parachute material, so nylon stockings did not become generally available in Britain until the end of the Second World War. Sadly, Wallace Carothers was not to see the development of his invention. He had been troubled with periods of mental depression since his youth. Despite his success with nylon, and other inventions such as neoprene (the first commercially successful synthetic rubber), he felt that he had not accomplished much and had run out of new ideas. His unhappiness was compounded by the death of his favourite sister, and on 29th April 1937 he committed suicide. Meanwhile, the Germans were also working on a replacement for silk in parachutes, and in about 1939 successfully produced ‘PERLON’. This was a similar POLYAMIDE to the Du Pont product, which was called ‘nylon’. Strangely, the term ‘nylon’ was not registered, and has become the generic name for polyamides used to make fibres.  Chemistry Carothers did not make his discoveries by accident; he set about systematically trying to create new polymers. In one series of experiments he decided to try to make synthetic polymers in which the polymer molecules were built up in a similar way to the protein chains in silk and wool. Instead of using amino acids (the starting materials for proteins), Carothers began with amines and carboxylic acids. Amines are organic compounds which contain the –NH2 reacts with the –COOH group in a carboxylic acid, an AMIDE group –CONH- is formed. In the process, a molecule of water is eliminated. Reactions of this type are known as: CONDENSATION REACTIONS. Carothers uses diamines and dicarboxylic acids which contained reactive groups in two places in their molecules, so they could link together to form a chain. In this way he was able to make polymers in which monomer units were linked together by amide groups. The process is called CONDENSATION POLYMERISATION because the individual steps involve condensation reactions. Chemically, Du Pont’s version of nylon, also made in the 1960’s by ICI under the name ‘Bri Nylon’ is NYLON 6.6. This is because the 2 MONOMERS used to make the POLYMER both contain 6 carbon atoms. The polymer is therefore of the type……ABABABABAB….. or (AB)n where is the degree of polymerization (DP) has a value of 60-80 for nylon 6.6 Perlon, on the other hand, was manufactured from only one MONOMER, and as this also has 6 carbons atoms in it, the polymer is called NYLON 6. It is therefore of the type….AAAAAAAAAA…… or (A)n, where n is about 200. Courtaulds manufactured nylon 6 in the 1970’s under the name ‘CELON’. Other Polyamides There have been, and in some cases, still are, many other polyamides used for fibre manufacture. Among them are: a) ‘QIANA’ (Du Pont) – 1969 - > 1984. An expensive, fine denier (tex) silk-like fibre. b) ARAMID fibres. KEVLAR (Du Pont) – very strong NOMEX Temperature resistant c) MICROFIBRES e.g. Tactel (ICI -> Du Pont) MERYL (Rhone-Poulenc) Spinning and Drawing Drawing …. As described earlier  Mechanical Properties Interchain bonding in Nylon 6,6 Nylon is very crystalline, up to 85% 1. High strength-to-weight ratio (65-85% Crystalline) SG 1.14 2. High Breaking Elongation 3. Excellent recovery from deformation (100% recovery, 6-8% extension) 4. 5. High abrasion resistance 6. High Flex resistance OTHER PROPERTIES 7. Ease of dyeing (cf Polyester) Acid dyes 8. Best moisture regain of synthetics (4-4.5%)  Nylon 6 and Nylon 66 NYLON 6 NYLON 66 Melting point 215°C Melting point 265°C DP c. 200 DP 50-80 Lower energy costs Greater dye affinity Better colour fastness Gel formation better Better temperature resistance Degradation if held molten Stenter range 6°C Stenter range 20°C Heat setting Better fatigue resistance Tyre Cord Nylon End Uses Carpets (tufted) Hose (Stockings, tights, socks etc.) Waterproofs – anoraks, Cagoules, ski jackets Tarpaulins Sportswear – Tactel microfiber Lingerie Summary We have seen that nylon was first truly synthetic man-made fibre, and that there is a wide variety of possible POLYAMIDES to choose from. We have seen that the main types are nylon 6.6 and nylon 6, and that their properties are similar, but that there are significant differences, e.g. in melting point and dyeability. We have noted the importance of new developments such as ARAMIDS and MICROFIBRES. NYLON 6 – invented in Germany during World War II The polymer is of the type H-[A]n-OH where A is H-N-[CH2]5-C=O The monomer used is a ring compound called CAPROLACTAM  Acrylics Definitions POLYMERS Polymers can have single monomer unit (A),……AAAAAAAAAAA……, such as nylon 6 and polyethelene COPOLYMERS There are 4 types of Copolymer: RANDOM e.g Acrylic fibres ALTERNATING e.g Nylon 6.6, PET BLOCK Elastane, Lycra GRAFT Acrylics From the 1950s to 1970s several companies introduced acrylic fibres. COMPANY TRADE NAME Du Pont (USA) Orlon (no longer made) Coutaulds (UK) Courtelle Bayer (Ger) Dralon Monsanto (USA) Acrilan The methods of manufacture have been kept secret, but the main part of the polymer chain is POLYACRYLONITRILE (PAN). This is how Courtaulds describe the production of Courtelle.  Acrylic Fibre Manufacture Drying Extrusion: The spinning soln is pumped th’ the fine holes of a spinneret into a coagulating bath and drawn off as continuous filaments which are collected together to form a continuous ‘tow’ or rope of filaments. The bath removes the solvent from the spinning soln leaving solid acrylic filaments. Stretching: Under heat to develop strength, the filaments are drawn. Washing: To remove excess solvent Drying: Using heat Stabilising or heat setting: Heated to a specific temperature to prevent subsequent shrinkage. Crimping or texturing: Crimps facilitate spinning into yarns, adds resilience and improves handle. Cutting & collecting: Cutting the filaments to the desired staple length for spinning on cotton, worsted or other machinery. More on Acrylics An acrylic polymer is a RANDOM COPOLYMER composed of 2 or more monomers, but, by definition, at least 85% of the monomer used must be acrylonitrile. The remaining monomer is included in order to confer dyeability. e.g acrylic acid CH2 = CH-COOH CH2 = CH-COOH acrylic acid provides dye sites for BASIC dyes CH2 = CH-COCH3 vinyl acetate (opens up structure) AND MAKES IT LESS CRYSTALLINE Modacrylics Acrylic monomers which contain 65-85% acrylonitrile are classed as MODACRYLICS. These usually involve a monomer containing H2C=CH-Cl Vinyl Chloride Chlorine containing polymers tend to be flame retardant. Nearly all acrylic fibre production is in the form of STAPLE fibre which is spun and TEXTURISED, and competes with wool in knitted goods. It is also used in blankets and pile fabrics (artificial furs), as in soft toys. Acrylic Fabric Aesthetics Acrylic fibres and fabrics more successfully duplicate the positive aesthetic attributes of wool fibres and fabrics than any other manufactured fibre. As a generic group, acrylic fibres are among the softest. In the case of acrylic fibres, softness is due to the flexibility of the polymers as well as to cross-sectional fibres.  The excellent covering power and bulk of acrylic fabrics result from the low specific gravity and irregular cross-sectional shape of the fibres. Acrylic fibres have moderate resilience. Fabrics resist wrinkling and undesirable creases hang out rather quickly. Bulky fabrics are especially resilient and lofty. Trouser creases and skirt pleats can be set in and remain unaffected by normal wear as well as laundering and dry cleaning processes. Acrylic Fibre Properties 1. Do not melt – degrade above 200°C Yellow – carbonizes -> Carbon fibres 2. Wet spun 3. Fibres not very crystalline, but soft, flexible, wool-like handle. 4. Dimensional instability caused by both heat and wetness. An increase in temperature when the fibre is wet causes greater instability. 5. Hot water must not be used when washing acrylic fabric, nor is steam cleaning advisable, thus limiting the fibres use in woven fabrics and carpets. Acrylic carpets are made in expensive, high density constructions such as a result of the fibres poor hot-wet performance. Acrylic End Uses 1. Apparel (mainly knitted) Sweaters, hosiery, pile/fleece garments 2. Industrial and consumer Toy animal furs, paint rollers, outdoor furniture, Fabric boat, car, swimming pool covers 3. Household/Interior/furnishings Blankets, upholstery, drapes, furniture covers Bulk Knitted Yarn Manufacture  Elastomerics ELASTANE (=Spandex) Trade name LYCRA by DuPont Lycra Lycra belongs to the generic elastane classification of man-made fibres (known as spandex in the United States and Canada), and is described in chemical terms as a segmented polyurethane. It is composed of soft, or flexible, segments bonded together with hard, or rigid segments. It is this molecular structure which endows the fibre with its in-built capacity to stretch and recover. In the fibre’s naturally relaxed state, the soft chains lie in tangle disorder. Under tension the chains straighten out….. ….while always straining to draw back to their natural tangle Lycra can be stretched four to seven times its initial length. It will instantly recover its original length when tension is relaxed. Lycra elastane compared with rubber is both stronger and more durable, and possesses two or three times more restraining power with one-third less weight. Unlike rubber, Lycra is resistant to both sun and salt water and retains its flex-tone in wear, and over time.  Single and Double covered Lycra Stretched Lycra is wrapped in a strand of non-elastic filament yarn. For maximum quality sometimes two strands are used, wound in opposite directions (described as S and Z). The second covering balances the yarn’s tendency to spiral. First covering Second covering Lycra Properties 1. Stretch: elongation up to 600% 2. Light weight 3. Resistant to: Distortion and abrasion Discoloration Damage from oil and perspiration UV light degradation Deterioration caused by ozone and pollutants in the air Oxidation Dry cleaning Washing at high temperatures Lycra End Uses Lingerie and Underwear Bodywear, Swimwear, Sportwear Sleepwear Waistbands and Edgings Accessories Medical bandages  Summary We have seen how acrylic fibres, incorporate a co-monomer in order to confer dyeability. Acrylic fibres compete with wool in knitwear, but care must be taken not to wash above 60°C, as acrylics are unstable under hot, wet conditions. Lycra is superior to rubber in stretch garments, and is incorporated into many modern textiles (2%-10% by weight). Linen Flax and Linen There are sometimes some confusion between the words “Flax” and “Linen”. Flax relates to the flat plant and the fibres derived from it. e.g Flax plant Flax seed (also linseed) Flax fibre Flax yarns, or linen yarns Linen applies to the products made from flax fibres. E.g. Linen fabrics Linen handkerchiefs Linen sheets Linen tablecloths Linen clothes Linen is the oldest textile material in the world. Its history goes back into the Stone Age. Fragments of Linen, in the stages of manufacture (straw, seeds and seed capsules, fibres, yarns, ropes and various types of fabrics) have been found amongst the remains of Swiss lake dwellings which date from about 8000 years B.C. The anatomy of flax The botanical name of cultivated flax (of both the “oil” and “textile” varieties) is linum usitatissimum. One of the varieties of this species is characterized by a long (80/120 cm) relatively unbranched stem and bears small seeds – this is textile flax. Another variety is used for the production of vegetable oil – “linseed oil”. The flower of the flax plant has five petals, whose colour or less violet) to white. The microscopic examination of a cross-section of the plant shows that it has different layers of cellulose (98%) which are extracted. The length, the composition and the cohesion of the fibre bundles produce the strongest, most comfortable of natural fibres. This section of the stem of a flax plant shows the bundles of fibres cells lying below the surface layer From seed to fabric Linen/flax Manufacture Reed-like plant grows 90-120cm high. Grows in temperate climates  Russia, France, Belgium, Netherlands most important for fibres. BAST fibres, also Jute. Seen known as linseed – Canada, USA, Argentina Properties c.f cotton Linen Cotton Tenacity at 12% R.H 4.0-6.0 3.0-4.9 Wet 4.5-8.0 3.3-5.1 Extension at break 12% R.H 1.5-4.5 3-7 Wet 2.5-6.0 - Moisture Regain (%) 12 7 Moisture Absorption 46-60 35-48 (Water imbibition per 100g fabric) End Uses Household textiles Bed linen, bathroom linen and dining linen Furnishing fabrics Curtains, upholstery, wallcoverings Clothing