Saturday, August 3, 2013

General Properties of Fiber Polymers and Fibers[1]
Macro Properties - Part V
Art Resource

Marie-Therese Wisniowski

Preamble
This is the eighteenth post in the "Art Resource" series, specifically aimed to construct an appropriate knowledge base in order to develop an artistic voice in ArtCloth.

Other posts in this series are:
Glossary of Terms
Units Used in Dyeing and Printing of Fabrics
Occupational, Health & Safety
A Brief History of Color
The Nature of Color
Psychology of Color
Color Schemes
The Naming of Colors
The Munsell Color Classification System
Methuen Color Index and Classification System
The CIE System
Pantone - A Modern Color Classification System
Optical Properties of Fiber Materials
General Properties of Fiber Polymers and Fibers - Part I
General Properties of Fiber Polymers and Fibers - Part II
General Properties of Fiber Polymers and Fibers - Part III
General Properties of Fiber Polymers and Fibers - Part IV
General Properties of Fiber Polymers and Fibers - Part V
Protein Fibers - Wool
Protein Fibers - Speciality Hair Fibers
Protein Fibers - Silk
Protein Fibers - Wool versus Silk
Timelines of Fabrics, Dyes and Other Stuff
Cellulosic Fibers (Natural) - Cotton
Cellulosic Fibers (Natural) - Linen
Other Natural Cellulosic Fibers
General Overview of Man-Made Fibers
Man-Made Cellulosic Fibers - Viscose
Man-Made Cellulosic Fibers - Esters
Man-Made Synthetic Fibers - Nylon
Man-Made Synthetic Fibers - Polyester
Man-Made Synthetic Fibers - Acrylic and Modacrylic
Man-Made Synthetic Fibers - Olefins
Man-Made Synthetic Fibers - Elastomers
Man-Made Synthetic Fibers - Mineral Fibers
Man Made Fibers - Other Textile Fibers
Fiber Blends
From Fiber to Yarn: Overview - Part I
From Fiber to Yarn: Overview - Part II
Melt-Spun Fibers
Characteristics of Filament Yarn
Yarn Classification
Direct Spun Yarns
Textured Filament Yarns
Fabric Construction - Felt
Fabric Construction - Nonwoven fabrics
A Fashion Data Base
Fabric Construction - Leather
Fabric Construction - Films
Glossary of Colors, Dyes, Inks, Pigments and Resins
Fabric Construction – Foams and Poromeric Material
Knitting
Hosiery
Glossary of Fabrics, Fibers, Finishes, Garments and Yarns
Weaving and the Loom
Similarities and Differences in Woven Fabrics
The Three Basic Weaves - Plain Weave (Part I)
The Three Basic Weaves - Plain Weave (Part II)
The Three Basic Weaves - Twill Weave
The Three Basic Weaves - Satin Weave
Figured Weaves - Leno Weave
Figured Weaves – Piqué Weave
Figured Fabrics
Glossary of Art, Artists, Art Motifs and Art Movements
Crêpe Fabrics
Crêpe Effect Fabrics
Pile Fabrics - General
Woven Pile Fabrics
Chenille Yarn and Tufted Pile Fabrics

The Glossary of Terms, Timelines of Fabrics, Dyes and Other Stuff, A Fashion Data Base, Glossary of Colors, Dyes, Inks, Pigments and Resins, Glossary of Fabrics, Fibers, Finishes, Garments and Yarns and Glossary of Art, Artists, Art Motifs and Art Movements have been updated in order to better inform your art practice.

If you find any post on this blog site useful, you can save it or copy and paste it into your own "Word" document etc. for your future reference. For example, Safari allows you to save a post (e.g. click on "File", click on "Print" and release, click on "PDF" and then click on "Save As" and release - and a PDF should appear where you have stored it). Safari also allows you to mail a post to a friend (click on "File", and then point cursor to "Mail Contents On This Page" and release). Either way, this or other posts on this site may be a useful Art Resource for you.

The Art Resource series will be the first post in each calendar month. Remember - these Art Resource posts span information that will be useful for a home hobbyist to that required by a final year University Fine-Art student and so undoubtedly, some parts of any Art Resource post may appear far too technical for your needs (skip over those mind boggling parts) and in other parts, it may be too simplistic with respect to your level of knowledge (ditto the skip). The trade-off between these two extremes will mean that Art Resource posts will hopefully be useful in parts to most, but unfortunately may not be satisfying to all!


External Structure Of Fibers
The external structure of s fiber consists of length, diameter, cross-sectional shape, surface contour, crimps or twists and distinctive parts etc. Whilst we have dealt with some of these characteristics previously, for completeness we shall give a quick overview of these external properties.

Length
Fibers are produced in basically two types: filaments and staple form.

Filaments are long continuous strands; they can be natural such as in the case of silk or not natural such as man-made. The man-made filaments are either a mono-filament yarn (i.e. a single fiber type) or multifilament yarn (i.e. made from a number of tiny filaments with or without twists). In the latter form, the size and the number of filaments may vary, depending on the end-use of the fabric.

Types Of Filament Fiber Yarns. A: Multifilament Yarn; B: Monofilament Yarn.
Courtesy reference [1].

Staple fibers are either natural or man-made and are short in length (from 1 to 60 cm). All the natural fibers, except silk, are staple.

Staple From Man-Made Fibers.
Note: Fibers are uniformly cut lengths that have been fluffed.
Courtesy reference [1].

Filament tow is a collection of many parallel filaments with crimp, but without twist and grouped together in rope form.

Section of Filament Tow or Rope.
Note: Thousands of filaments from which it is made.
Courtesy reference[1].

Filament Tow Cut in Uniform Lengths.
Note: This is required for ultimate use in fabrics and garments.
Courtesy reference[1].


Diameter, Size or Denier
Man-made fibers can be made uniform in diameter, can be varied in diameter shape, and can be made thick and thin at regular intervals throughout their length. Natural fibers are subject to growth irregularities and therefore are not uniform in size or in development along their length. The finer the diameter of the fiber, the more pliable it is and therefore the softer it feels. The thicker the fiber, the more body and stiffness it has and the more resistant it is to crushing.

In natural fibers a major determinant of quality is the thickness of the fiber. Fiber thickness is measured in microns (10-6 meter). Hence cotton, wool and silk have thickness of 16-20, 10-70 and 11-12 microns. respectively.

The fineness of man-made fibers is measured in deniers, which is the weight of 9,000 meters of yarn or fiber. It is the weight in grams of this unit length. Stable fiber is sold by denier and length, whereas filaments are sold by denier of the yarn or tow and the number of filaments in the yarn or tow. To determine the filament size, the yarn denier is divided by the number of filaments (i.e. 2 denier per filament is 40 denier yarn divided by 20 filaments). Carpets range from 15-24 deniers, whereas clothing from 1-7 deniers.


Cross-Sectional Shape
Fiber shape of man-made fibers is controlled by the spinneret. Shapes vary from round to flat and straw-like and are important because they help determine the texture of fabrics. For a silk like texture, trilobal fibers, which resemble silk in size and cross-section, are man-made. Shape is also important in luster, bulk and body, and helps to determine the hand or feel of the fabric.

Natural fibers derive their shape from : (i) the way the cellulose is built up during the plant growth; (ii) the way the shape of the orifice through which the silk fiber is extruded; (iii) the way the shape of the hair follicle and the formation of protein substances in animals.

The figure below shows typical cross-section shapes and fiber contours.

Typical Cross-Section Shapes and Fiber Contours.
Note: Surface smoothness or roughness is also exposed.
Courtesy reference[1].


Surface Contour
Surface contour may be smooth serrated, lobular or rough. The surface contour is defined as the surface of the fiber along its shaft. Some of the differences in the surface contour of the different fibers are shown in the figure above. Surface contour is important in the hand and texture of the fabric.

Crimp
Crimp refers to the waves, bends or twists that occur along the length of the fiber. Fiber crimp should not be confused with the weave crimp, which results from the interlacing of yarns in the fabric, nor with molecular crimp, which results from the way molecular chains are built up. Fiber crimp increases cohesiveness, resiliency, resistance to abrasion, and gives increased bulk and warmth to fabrics. It assist fabrics to maintain their loft or thickness, increases absorbency and skin-contact comfort, but reduces luster.

A fiber may have three kinds of crimp, namely: mechanical crimp, natural or inherent crimp, or latent (chemical) crimp. Mechanical crimp is imparted to fibers by passing them through fluted rollers to produce a two-dimensional, saw-tooth crimp. The bends are angular in contrast to the rounded waves of a natural crimp. If the fluted rolls are heated, the crimp will be permanent in the thermoplastic or synthetic fibers. The figure below shows mechanical crimping gears. Texturizing processes to give loft, bulk or stretch are done on filament (sometimes staple fiber) yarns by dropping the yarns into a stuffing box, or running them through a false twister or subjecting them to a curling process. Natural or inherent crimp occurs in cotton and wool. Cotton has a two-dimensional twist called convolutions. Wool has three-dimensional crimp.

The third type of crimp, latent or chemical, exists in the fiber in an undeveloped state until the finished garment is either: (i) immersed in a suitable solvent or; (ii) given a heat treatment to develop the crimp. This kind of crimp occurs in fibers that have been modified in the spinning solution or in the extrusion process. The modification produces a fiber that will shrink more on one side than it does on the other. High shrinkage of one side forces the fiber to curl.

Mechanical Crimping Of Man-Made Fibers.
Courtesy reference[1].


Distinctive Parts
Natural fibers, except for silk, usually have three distinctive parts: (i) an outer covering called a skin or cuticle; (ii) an inner area; (iii) a central core that may or may not be hollow. On the other hand, man-made fibers are not so complex and usually have a skin and a solid core.

Internal Structure Of Fibers
We shall not labor on the internal structures of fibers, although their chemical structure, chemical composition, molecular structure and the regions of the fiber polymer system are all critical areas in understanding the properties of specific fibers. Rather we shall only give a brief overview of the latter.

The fiber polymer system of a fabric can be explained in terms of the way in which polymer chains are orientated with respect to each other. The amorphous regions of a fiber polymer system have random orientations with respect to each other leaving large voids or spaces between them. These are also called the non-crystalline regions of the fiber polymer system. Hence in the figure (a) below there are two effects, not ordered and not orientated. The second type is when there are highly ordered or crystalline regions embedded amongst unordered or amorphous regions as in figure (b) below. Note: none of the ordered or crystalline regions are orientated with respect to each other. Also the crystalline regions always have much smaller voids or spaces then the amorphous regions. The third extreme is when the fiber polymer system is highly ordered or crystalline as well as highly orientated in a particular direction. Figure (c) show both properties, namely highly ordered and highly orientated.

Orientation and Order of Fiber Polymer System.
(a) Non Orientated Non-crystalline Fiber Polymer System; (b) Non-Orientated but Sections Ordered Fibre Polymer System; (c) Orientated and Crystalline Fiber Polymer System.

It is clear that the amount of crystallinity (ordered regions) and the amount of orientation of the ordered regions will affect a myriad of properties such as dye-ability, tensile strength, hand of the fabric, stretching and drawing properties etc. Note: stretching or drawing of a fiber increases the orientation of the fiber, reduces its diameter and packs the polymer chains closer together.

(a) Non-Stretched or Undrawn Fiber; (b) Stretched or Drawn Fiber.


Fiber Properties and How They Affect Fabrics
To make matters simple, we will do the translation under three headings:
Fiber Property
Reason For Fiber Property
Translation Into Fabric Property

Fiber Property: Abrasion resistance is the ability of the fiber to resist damage due to rubbing or abrasion during every day use.
Reason For Fiber Property: This is due to: (i) the tough outer layer, scales or skin of fiber; (ii) the flexible and strong bonds within the fiber polymer system.
Translation Into Fabric Property: Affects the following properties of fabrics: (i) its durability; (ii) its abrasion resistance; (iii) its rubbing resistance; (iv) its resistance to splitting.

Fiber Property: Absorbency is the ability of a fiber to take up moisture and is expressed in terms of moisture regain (which is the percentage of moisture that a bone-dry fiber will absorb from air under standard conditions of temperature and moisture).
Reason For Fiber Property: This is due to: (i) the fiber polymer system contains hydroxyl groups (-OH); (ii) the fiber polymer system have large amorphous regions and low regions of crystallinity.
Translation Into Fabric Property: It affects the following properties of a fabric: (i) comfort; (ii) warmth; (iii) water repellency; (iv) absorbency; (v) static electricity build up; (vi) shrinkage; (vii) dyeability; (viii) wrinkle resistance and crease recovery; (ix) tear strength; (x) spotting.

Fiber Property: Ageing resistance.
Reason For Fiber Property: This is due to the chemical structure of the fiber polymer system.
Translation Into Fabric Property: This affects the durability and long lived storage of the fabric.

Fiber Property: Chemical reactivity is the effect of acids, alkali, oxidizing agents and solvents on the fiber.
Reason For Fiber Property: The fiber polymer system contains polar groups and so its chemical structure is the cause for this fiber property.
Translation Into Fabric Property: Helps to determine care required during cleaning of the fabric - such as its ability to withstand bleaching, and to take acid or alkali finishes.

Fiber Property: Cover is the ability of the fiber to occupy space for the purpose of concealment or protection.
Reason For Fiber Property: This results from the crimp, curl or twist of the fiber and its cross-sectional shape.
Translation Into Fabric Property: It affects the warmth of the fabric and its cost, since less fiber is required.

Fiber Property: Cohesiveness is the ability of fibers to cling together during spinning. This is an important property in staple but not in filament.
Reason For Fiber Property: This is caused by the crimp or twist property of the fiber.
Translation Into Fabric Property: This affects the fabrics resistance to ravelling.

Fiber Property: Creep is delayed elasticity; that is, the fiber does not recover immediately from the strain but will recover gradually.
Reason For Fiber Property: This is due to the lack of side chains, cross links and strong bonds within the fiber polymer system as well as because of its poor orientation.
Translation Into Fabric Property: It affects the levelness of the fabric when dyed. A high creep fiber may cause the fabric to dye streakily.

Fiber Property: Density of the fiber is a measure of its mass relative to its volume and so has units of gm per millimeter (g ml-1). Specific gravity is the ratio of the mass of the fiber to an equal volume of water at 4oC. Both measure the weight of a fiber.
Reason For Fiber Property: This is due to the chemical composition of the fiber polymer system.
Translation Into Fabric Property: It affects the fabric's: (i) warmth without weight; (ii) loftiness - full and light; (iii) buoyancy.

Fiber Property: Dye-ability is the ability of fibers to be dyed.
Reason For Fiber Property: There are numerous fiber properties that contribute to its dye-ability and for that matter, some of these properties preclude the use of particular dye types in preference for other dye types etc. The major fiber properties with respect to dye-ability depend on: (i) Chemical structure of the fiber (e.g. reactive groups and dye sites in the fiber polymer system); (ii) molecular structure such as its orientation, crystallinity, cross linkages, hydrogen bonding etc. within the fiber polymer system; (iii) fiber diameter.
Translation Into Fabric Property: Affects the ability of a fabric to be dyed or printed with a particular dye type.

Fiber Property: Elastic recovery is the ability of fibers to recover from strain. Elasticity is the ability of a stretched material to return immediately to its original size. Fibers usually have high elasticity for low stretches and high elasticity for high stretches.
Reason For Fiber Property: This is due to the molecular structure - such as side chains, cross-linkages and strong bonds - within the fiber polymer system.
Translation Into Fabric Property: This affects the fabric's process-ability, resiliency and delayed elasticity or creep.

Fiber Property: Electrical conductivity is the ability of a fiber to transfer electrical charges (such as electrons) along its length and breadth.
Reason For Fiber Property: This is due to the chemical structure (i.e. existence of polar groups) within the fiber polymer system.
Translation Into Fabric Property: Poor conductivity causes: (i) fabric to cling to a person in cold dry atmospheres; (ii) promotes the build up of static charge causing electrical shocks; (iii) causes fabrics to cling to machinery during fabric and garment production.

Fiber Property: Elongation is the ability for a fiber to be stretched, extended or lengthened. For production of yarns and fabrics a minimum of 10 per cent elongation is desirable. Elongations vary at different temperatures, or when the fiber is wet or dry.
Reason For Fiber Property: This is due to the fiber crimp and/or to the molecular structure of its fiber polymer system (e.g. molecular crimp orientation).
Translation Into Fabric Property: It affects: (i) working of textiles; (ii) fabrics tear strength; (iii) fabrics brittleness; (iv) provides "give" and stretchiness of fabrics.

Fiber Property: Feltability is the ability of fibers to mat together.
Reason For Fiber Property: This is associated with the scale structure of wool.
Translation Into Fabric Property: Enhances the ability to make fabrics directly from fibers; special care required during washing in order to avoid unintended felting.

Fiber Property: Flammability is the ability of a fiber to ignite and burn.
Reason For Fiber Property: This is due to the chemical composition of the fiber polymer system.
Translation Into Fabric Property: The flammability of the fabric is controlled by the flammability of the fiber.

Fiber Property: Hand is the way a fiber and fabrics feels when handled - silky, harsh, soft, crisp, dry and tactile are just some descriptors of the handle or hand of a fabric.
Reason For Fiber Property: This is due to the outside or external structure of the fiber; that is, is due to the fiber's diameter, cross-sectional shape, its crimp and length etc.
Translation Into Fabric Property: It affects the handle or hand of the fabric.

Fiber Property: Heat conductivity is the ability of the fiber to conduct heat away from the body.
Reason For Fiber Property: This is due to the fiber's external structure; that is, it is due to its crimp, cross-sectional shape and the uniformity of its cross-section shape.
Translation Into Fabric Property: It affects the warmth of a fabric.

Fiber Property: Heat sensitivity is the ability of the fiber to soften, melt or shrink when subjected to heat.
Reason For Fiber Property: This is due to the inner structure of the fiber; that is, there are fewer inter-molecular attractive forces, and no cross links within the fiber polymer system. Heat causes the molecular structure and/or molecular groups within the fiber polymer system to vibrate more vigorously.
Translation Into Fabric Property: This property determines safe washing and ironing temperatures of the fabric; makes heat setting the fabric possible; makes certain heat sensitive fabric finishes possible.

Fiber Property: Luster is the light reflected from the surface of the fiber. It differs from shine in that it is more subdued; that is, in the case of luster the reflected light is more scattered, whereas for shine the reflected light is better bundled in a given direction.
Reason For Fiber Property: This is due to the external structure of the fiber; that is its length, crimp and cross-sectional shape.
Translation Into Fabric Property: It affects the luster or shine of the fabric.

Fiber Property: Loft or compressional resiliency refers to the ability of the fiber, yarn or fabric to spring back to its original thickness after being compressed.
Reason For Fiber Property: This is due to the fiber crimp.
Translation Into Fabric Property: It affects fabric's springiness, cover and resistance to flattening.

Fiber Property: Moth resistance.
Reason For Fiber Property: This is due to chemical composition of the fiber (e.g. no sulfur being present in the fiber polymer system).
Translation Into Fabric Property: It affects level of care during storage of the fabric.

Fiber Property: Mildew Resistance.
Reason For Fiber Property: This is due to the chemical composition of the fiber polymer system.
Translation Into Fabric Property: It affects level of care during storage and moreover, the selection of fabrics for damp, humid conditions.

Fiber Property: Pilling is the balling up of fiber ends on the surface of fabrics.
Reason For Fiber Property: This is associated with fiber strength.
Translation Into Fabric Property: It affects extent of pilling of fabric.

Fiber Property: Stability is the retention of size, shape or form of the fiber.
Reason For Fiber Property: This is due to the chemical composition of the fiber polymer system (e.g. strong molecular bonds).
Translation Into Fabric Property: It affects the fabrics resistance to shrinkage.

Fiber Property: Stiffness or rigidity is the opposite to flexibility. It is the resistance to bending or creasing of the fiber.
Reason For Fiber Property: This is due to the amount of crystallinity of the fiber polymer system.
Translation Into Fabric Property: It affects the handle and body of the fabric.

Fiber Property: The strength of the fiber is defined as the ability to resist stress and is expressed as tensile strength (pounds per square inch) or tenacity (grams per denier).
Reason For Fiber Property: This is due to molecular structure of the fiber polymer system (e.g. degree of polymerization, orientation, crystallinity etc.).
Translation Into Fabric Property: It affects the fabric's: (i) durability; (ii) tear strength); (iii) sagging characteristics; (iii) extent of pilling; (iv) fabric weight.

Fiber Property: Sunlight resistance is the ability of a fiber to withstand degradation from direct sunlight (usually the UV component).
Reason For Fiber Property: This is due to the chemical composition of the fiber polymer system.
Translation Into Fabric Property: It affects the durability of outdoor cloths, swim wear, curtains and draperies etc.


Reference:
[1] N. Hollen and J. Saddler, Textiles, 3rd Edition, The Macmillan Company, London (1971).

1 comment:

sarvesh singh said...

Thanks for sharing this information about tow service.