Chapter 4 A Study of Fibers and Textiles identify and describe common weave patterns of textile samples compare and contrast various types of fibers through physical and chemical analysis describe principle characteristics used to identify common fibers apply forensic science techniques to analyze fibers
Natural Fibers ______________ are the plant fibers most ______________ used in textile materials. Type of cotton, _________ and degree of _________ contributes to the diversity of these fibers. Processing techniques and color applications also influence the value of cotton fiber identification.
Natural Fibers Other plant fibers used in the production of textile materials include ______, _____ and _____. The animal fiber most frequently used is ________, typically from sheep. ____________ of fiber determined by usage in final fabric application.
Fiber Classification —Natural Fibers _________ fibers (made of proteins): Wool from ______, cashmere and mohair from ______, angora from ______, and hair from alpacas, llamas, and camels are commonly used in textiles. Shimmering silk from caterpillar _________ is longer and not as easily shed.
Fiber Classification —Natural Fibers Plant fibers (made of the polymer cellulose): can ________ water. are __________ in water. are very ___________ to damage from harsh chemicals. can only be _________ by strong ______. can be ___________ at crime scenes because they become ________ over time.
Fiber Classification —Natural Fibers Plant fibers: Cotton from _________ is the plant fiber most commonly used in textiles (shown above). _______ from ________ is durable. Hemp, jute, and flax from stems grow in bundles. __________ and sisal from leaves deteriorate more quickly. Mineral Fibers: __________ is a fibrous form of glass. __________ is a naturally occurring mineral with a crystalline structure.
Fiber Classification —Synthetic (artificially produced) Fibers Until the nineteenth century only plant and animal fibers were used to make clothes and textiles. __________ the products produced today are artificially produced. Artificially produced fibers include ______, ________, _________, _________, and ____________.
Fiber Classification —Synthetic (artificially produced) Fibers Regenerated Fibers (derived from cellulose): __________ is the most common of this type of fiber. It can imitate natural fibers, but it is __________. __________is cellulose chemically combined with __________ and is often found in carpets. ____________ nylon is cellulose combined with three acetate units, is breathable, lightweight, and used in performance clothing.
Fiber Classification —Synthetic (artificially produced) Fibers Synthetic Polymer Fibers: ___________ is the basis for these fibers, and they have very different characteristics from other fibers. ____________ in large vats are joined together to form polymers. The fibers produced are spun together into yarns. They have no ____________ structures, and under magnification they show regular diameters.
Fiber Classification—Synthetic (artificially produced) Fibers Examples of synthetic polymer fibers: spandex nylon _________—found in “polar fleece,” wrinkle- resistant, and not easily broken down by light or concentrated acid; added to natural fibers for strength. __________—easily broken down by light and concentrated acid; otherwise similar to polyester. ___________—inexpensive, tends to “ball” easily, and used as an artificial wool or fur. ___________—high performance, quick drying, and resistant to wear.
Man-made Fibers The shape of a ___________ fiber can determine the value placed on that fiber. Cross section of a man-made fiber can be manufacturer-__________. Some ___________ are more common than others, and some shapes may only be produced for a ________ of time.
Comparison of Natural and Synthetic Fibers Visual Diagnostics of Some Common Textile Fibers under Magnification
Yarns, fabrics, and textiles Fibers can be twisted (spun) into ______ of any length, thick or thin, loose, or tight. A blend can be made to meet different needs such as resistance to __________. Fibers can be woven into ________ or ________. –Threads are arranged side by side (the _______). –More threads (the _____) then are woven back and forth crosswise in one of a number of different patterns through the warp.
Man-made Fibers More than ______ of all fibers used in textile manufacturing are man-made. ___________ and ________ fibers are the most _________encountered man-made fibers, followed by __________, _________ and __________.
Sampling and Testing Weaving spun fibers (yarns) together produces clothing and many textiles. ___________ from an article of clothing or a textile is the most _________ form of fiber transfer. Natural fibers require only an _______ microscope to find characteristic _______ and _________. ___________________ can reveal something of the chemical structure of other fibers that, otherwise, may look very much alike.
Sampling and Testing If a large quantity of fibers is found, some can be subjected to ________ tests such as burning them in a flame (see analysis key above) or ___________ them in various liquids. Crimes can be solved in this way by ___________ fibers found on different suspects with those found at the crime scene.
................. Summary................. Summary Fibers are spun into yarns having specific characteristics. Yarns are woven, with different patterns, into clothing or textiles. Fibers, trace evidence, are a form of class evidence used by crime scene investigators. Fiber evidence may be gathered using different techniques. Fibers may be analyzed using burn tests, tests for solubility in different solutions, polarized light microscopy, or infrared spectroscopy.