Knitted fabrics are made from interlocking loops of yarn. There are two main types of knitting: WEFT KNITS WARP KNITS In weft knitting the loops of yarn are linked across the width of the fabric. In warp knitting the loops are linked in a vertical direction. To recap on what we know about fabrics – they can be woven, non-woven or knitted. Today, we are going to learn a little bit more about knitted fabrics. Knitted fabrics are made from interlocking loops of yarn. Depending on the type of knit construction, this will either be a single yarn, or several yarns. If the loops are broken, the fabric will easily come apart. There are 2 types of knitted fabric: WARP & WEFT. Warp knitting machine

Weft Knitting Weft knitting is made using a single yarn. It can be made by hand knitting or by machines. Characteristics of weft knits: The fabric has high elasticity and stretch. The loops of yarn trap air which retains body heat to keep us warm. The right and wrong sides of the fabric look different. the fabrics can lose shape easily. Creases fall out easily. The fabric can unravel and ladder easily. Weft knitted fabrics curl up at the edges when they are cut. Weft knitting is the type we generally think of as a knitted fabric. It can be be very heavy gauge (thick & chunky) or very fine gauge (used for T-shirts & underwear). Weft knitting uses a single yarn & the loops are linked across the width of the fabric. It can be done by hand or by machine. This type of knitting can unravel, & will ladder if a stitch is dropped, or the yarn is broken (think of what happens to your tights if you snag or catch them on something). I’m going to show you some clips of how the knitting is formed, & then we’ll have a go at producing a bit of our own.

Weft Knitting Weft knitting machines being used in industry: http://www.youtube.com/watch?v=B4qzdAdhKIo What this looks like in slow motion: http://www.youtube.com/watch?v=SUXk-EHKD_c&feature=related How to knit by hand: http://www.youtube.com/watch?v=4ViZRI6oPPg&feature=related In industry, warp knitting is made on huge computerised machines. These can be flat bed, V-Bed or circular machines. We’ll have a look at a clip of a flat bed machine. The 2nd clip is of a home-made knitting machine. Its much slower but it shows quite clearly the single yarn going across the bed of needles & the loops that form each stitch. It’s these stitches that give knitting its V-shapes. (If clip doesn’t work, put in ‘knitting machine – handmade’ into search engine on You Tube) The last clip is of hand knitting. Watch closely, as we’re going to have a go at knitting this stitch ourselves. It’s the most basic knitting stitch & is called the garter stitch.

Warp Knitted Fabrics In warp knitting the yarn loops vertically up the fabric and the process uses many yarns rather than one. The fabric does not unravel or ladder. It is an industrial process only. Warp knitting uses lots of different yarns which are looped together vertically as well as horizontally. The fabric doesn’t unravel when it is cut, so it won’t ladder. It is very fast to produce. The fabric is elastic but will still keep its shape. However, the machinery is very complicated, so the fabric can be expensive to produce. Warp knitting is used to make lace & nets (such as lace curtains) & a fabric called lock-knit which is used for bed sheets, furnishing fabrics, velour & swimwear. Characteristics of warp knits: The production system is fast so the fabrics are quick to make. The fabric is elastic but it can keep its shape. It can be cut and sewn easily as it lies flat when cut. It is mainly used with synthetic filament yarns.

Warp Knitting A warp knitting machine http://www.youtube.com/watch?v=xrSU2XfkAdg&feature=related Making a narrow lace trim http://www.youtube.com/watch?v=Wpx5Cubq7oo&feature=related Warp knitting machines can be used to make lace which is currently very on-trend & fashionable. This 1st clip shows a modern warp knitting machine & you can see that there are many yarns being knitted & looped together (if clip doesn’t work, click on the thumbnail on the right that is called 1.m2ts) The 2nd clip shows an older piece of machinery using many small bobbins of yarn to make narrow lace trims. (if clip doesn’t work, click on thumbnail entitled lace making machine, then on another thumbnail for same thing but a darker image, as this is a better clip).

Uses of Knitted Fabrics Weft Knits T-shirts Jumpers Cardigans Sweatshirt fabrics Warp Knits Net curtains Swimwear Terry towelling fabrics Patterned tights Lace fabrics So finally, a quick re-cap on some of the products that are made from knitted fabrics. If there is time, & the plexi-scope is working, show the knitted construction under the microscope.

Exam questions

Manufactured Synthetic Fibres Learning Objectives: Understand the sources, properties and uses of manufactured synthetic fibres. Identify the advantages and disadvantages of manufactured synthetic fibres.

Manufactured Synthetic Fibres – Polyamide (Nylon) Properties: Very strong Hard-wearing Does not decompose (rot) Melts as it burns Not very absorbent so it dries quickly Crease resistant Resists alkalis but can be damaged by acids. Versatile - can be made into many types of products. Advantages: Strong when wet Inexpensive Resists bacteria Durable and long lasting Disadvantages: Can be damaged by sunlight which discolours it and makes it weak. Low absorbency Not always comfortable to wear. Uses: Clothing Ropes Carpets & rugs Seat belts Fabric Names: Nylon Tactel Tactel Micro

Manufactured Synthetic Fibres- Polyester Properties: Very strong Can be made flame resistant Thermoplastic – can be heat set into pleats and shapes. Does not decompose Resists most alkalis but can be damaged by acids. Versatile as it can be made into many types of products. Fabric Names: Terylene Polar Fleece Trevira Finesse Miratec Dacron Uses: Sportswear Ties Sewing threads Medical textiles Net curtains Carpets Disadvantages: Poor absorbency so it is difficult to dye. Advantages: Strong when wet Dries quickly Crease resistant Cheap Resists bacteria

Manufactured Synthetic Fibres - Acrylic Properties: Strong when it is dry but weaker when wet. Shrinks away from heat. Thermoplastic Burns slowly then melts. Soft Warm Easy to wash and dry. Advantages: Warm Soft Insulating Inexpensive Dries quickly Disadvantages: Poor absorbency Fabric Names: Courtelle Amicor Uses: Knitwear Upholstery fabrics Fake fur Sportswear Toys

Manufactured Synthetic Fibres - Elastane Properties: Very elastic Lightweight Very strong Resists chemicals Not damaged by perspiration Aids crease resistance Advantages: Very stretchy Keeps its shape Resistant to damage by sun and seawater Lightweight Strong Makes garments comfortable to wear Disadvantages: Very poor absorbency Always needs to be blended with other fibres. It is too stretchy and elastic to be used on its own. Uses: Swimwear Sportswear Jeans Fabric names: Lycra

Regenerated Cellulose Fibres Regenerated cellulose fibres are made from wood pulp and chemicals. They are similar to cotton. Names of regenerated fibres: Viscose Rayon Acetate Triacetate Modal Tencel Lyocell Uses: Lyocell is used as a non woven fabric for medical wipes and swabs. Fashion clothing Lingerie Ribbons Protective clothing These are environmentally friendly fibres because they reuse waste chemicals in the production process. Properties of Regenerated Cellulose Fibres: Highly absorbent Washable Soft Smooth Comfortable to wear Drape well High strength when wet

Exam questions

Natural Fibres Learning Objectives: Understand the sources, properties and uses of natural fibres. Identify the advantages and disadvantages of natural fibres.

Natural Plant Fibres - Cotton Properties: Strong Absorbent Cool to wear Hard- wearing Creases easily Smooth Versatile Easy to care for Breathable Fabric Names: Calico Drill Corduroy Poplin Denim Velvet Advantages: Strong when wet Durable & long lasting Not expensive Environmentally sustainable Comfortable to wear Disadvantages: Creases easily Burns easily Shrinks when washed Uses: Soft furnishings such as cushions and curtains Clothing such as jeans and T-shirts Knitting yarns

Natural Plant Fibres - Linen Properties: Very hard-wearing Cool next to the skin Strong Absorbent Creases easily Dull lustre Breathable Fabric Names: Duck Huckabuck Mattress Ticking Holland Uses: Light weight summer clothing Tea towels Sheets Table cloths Disadvantages: Creases easily Expensive Advantages: Strong when wet Very hard-wearing Highly absorbent so dyes easily Comfortable to wear

Natural Animal Fibres - Wool Properties: Warm Absorbent Low flammability Good elasticity so creases drop out easily Comfortable to wear Fabric Names: Lambswool Merino Superwash Felt Harris Tweed Gaberdine Uses: Warm outer wear such as coats Jumpers and cardigans Blankets Carpets Advantages: Warm and insulating Does not crease easily Comfortable Can be produced in a wide range of weights of fabric. Disadvantages: Can shrink & felt when washed Takes a long time to dry as it is very absorbent Some types can be itchy next to the skin

Natural Animal Fibres - Silk Properties: Absorbent Soft and comfortable Cool but also warm and insulating when worn in layers Natural sheen and lustre Strong when dry Fabric Names: Chiffon Duchess Crepe Organza Dupion Taffeta Advantages: Soft, smooth and lustrous Drapes well Comfortable to wear next to the skin Disadvantages: Expensive Can be weak when wet so it needs careful washing or dry cleaning. May crease easily Uses: Luxury clothing such as lingerie, evening and bridal wear. Knitwear Soft furnishings

Exam questions

Regenerated Fibres Definition: Regenerated fibres are made from wood pulp (cellulose). They are partly natural and partly synthetic as a chemical is needed to extract the fibres. They way the fibres are produced differs from fibre to fibre. It can be done through wet spinning and dry spinning or even melt spinning. All cellulose fibres are either wet or dry spun or a combination of both.

Viscose Cellulose sheets are placed in a bath of caustic soda. Both are shredded They are thoroughly mixed up More caustic soda is added which makes the viscose solution. Solution is stored until needed.

Wet spinning The fibre solution is pressed through the spinneret It enters the acid bath which causes the fibres to set. Filaments are passing through a set of heated rollers that will further set the fibre. They are wound onto godet wheels ready for spinning. Pollution Viscose currently is becoming less common because of the polluting effects of carbon disulfide and other by-products of the process, forcing some factories to close.

Properties Viscose drapes and swings beautifully and the material is softer than cotton and more springy than silk. It is comfortable to wear and is great for dyeing. Viscose is a lovely fabric for floaty summer skirts, figure-hugging dresses, and underwear you want someone to notice. Uses: Jersey, suits, dress fabric and lining.

Viscose is a solution made from woodchips What do you know Viscose? Viscose is a solution made from woodchips False. It is a solution made from cellulose sheets dipped into caustic soda. Which spinning process is used to produce Viscose? Wet spinning Which liquid is the spinneret placed into? Acid Viscose pollutes the environment due to the by products of the viscose process. Which chemical causes the problem? Carbon disulfide It drapes well, is soft & comfortable to wear Give an example of viscose fabric qualities Give an example of a property of the viscose fibre It’s a filament, its soft has more elasticity than silk and is lustrous.

Lyocell & Tencel Lyocell is produced from wood pulp cellulose. It is marketed under the brand name Tencel. It is the modern Rayon! It that it is soft, absorbent, very strong when wet or dry, and resistant to wrinkles; it can be machine- or hand-washed or dry-cleaned, it drapes well, and it can be dyed many colours, as well as simulating a variety of textures like suede, leather, or silk. It is biodegradable.

Making process: Dissolve the wood pulp in a chemical which creates a solution called “dope”. The dope is then pushed through a spinneret to form the individual fibres. It is washed and the chemicals are retrieved from the water, purified, and recycled. Since there is little by product, this process is labelled as relatively eco-friendly. However, it uses a substantial amount of energy and the solvent is a by-product of petrol production. coagulation bath Dry/wet spinning

Uses: Staple fibres are used in apparel items such as denim, chino, underwear and other casual wear clothing, even in bath towels. Filament fibres are used in items that have a silkier appearance such as women’s clothing and men’s dress shirts and medical dressings. Tencel is also used for making baby diaper wipes. Fibres blends: Look for Tencel® lyocell blended with Tactel® nylon in which the Tactel® is on the surface for durability and wind and water resistance, while the Tencel® has greater exposure on the backing surface for warmth, absorbency, and comfort.

Acetate Properties of cellulose acetate: Good toughness Deep gloss High transparency A feel that can be described as ‘natural comfortable, Breathable and absorbent Natural and Renewable It is manufactured using wood pulp as a raw material. Wood pulp is a renewable resource grown in closely managed wood pulp forests.

Viscose is a solution made from woodchips What do you know Tencel & Lyocell? Viscose is a solution made from woodchips False. It is a solution made from cellulose sheets dipped into caustic soda. Which spinning process is used to produce Viscose? Wet spinning Which liquid is the spinneret placed into? Acid Viscose pollutes the environment due to the by products of the viscose process. Which chemical causes the problem? Carbon disulfide It drapes well, is soft & comfortable to wear Give an example of viscose fabric qualities Give an example of a property of the viscose fibre It’s a filament, its soft has more elasticity than silk and is lustrous.

Production of Acetate The production of cellulose acetate fibres is clean and meets all environmental regulations. Also, acetone is a biodegradable solvent. Cellulose acetate has been shown to be biodegradable and can be composted or incinerated. The acetone used in the manufacturing process is recovered (up to 95-98%). guidelines. Dry spinning

Uses: Ties, lingerie, and bathing suits, lining, dress fabric.

What are regenerated fibres made out off? Cellulose What do you know about Regenerated Fabrics? What are regenerated fibres made out off? Cellulose What do you need to make the wood pulp into a fibre? A chemical Which two spinning methods are there to make a generated fibre? Dry/wet spinning Which products are made from Acetate? Lining, dress fabric & ties Which products are made from Viscose? Lining, dress fabric & jersey Which is the least environmentally friendly regenerated fibre? Viscose Which regenerated fibres have a poor crease recovery? Viscose & Acetate Which R.F. have good crease recovery? Tencel & Lyocell