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Plastics raw mat

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by

Andrea Corbillon

on 18 September 2012

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Transcript of Plastics raw mat

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Most plastic products consist of a polymeric material that has been altered in order to improve selected properties. Polymers are prepared by processes in which small molecules undergo multiple combinations to form very large molecules These were the raw materials of Plastics Up next! I. Resins Shaping up Plastics: Raw materials where most plastics are originally made

principal material forming the basic plastic mixture

derived from vegetable matter, such as cellulose (from cotton),
furfural (from oat hulls), oils (from seeds, starch derivatives, or coal) Natural Resins secreted by many plants, appearing on the external surface of a
plant after a wound
cuts are made in the tree bark
globules of liquid resin that flow from the cut are directed by
troughs into collecting buckets
yellow to brown in color
insoluble in water but soluble in alcohol, ether, and other organic solvents Classification of Natural Resins a.hard resins are hard, brittle, odorless, and tasteless and exhibit glasslike fracture
obtained either as fossils or as distillation products of the oleoresins
e.g. amber, copals, mastic sandarac b. oleoresins are sticky, amorphous semisolids that contain essential oils
e.g. balsam, dragon’s blood, copaiba, turpentine

: most widely used oleoresin
: obtained by distillation of the oleoresin turpentine
: most commercially important of all the resins Turpentine Rosin c. gum resins are natural mixtures of gums and resins in variable proportions, therefore partly soluble in water

e.g. frankincense, myrrh, benzoin, asafetida But what are polymers? They are large organic molecules that are made synthetically or are of natural origin, and find use as plastics, rubber, fibers, and coatings These are giant molecules made up of repeating units called or monomers mers also called... macromolecules Natural Polymers a homopolymer of glucose in the alpha-glucose configuration and serves as an energy reserve for plants and an energy source of animals Starch a structural polymer in plants Cellulose cellulose-like biopolymer found in the exoskeletons of many insects and marine invertebrates Chitin
Casein (from milk): was among the non-vegetable materials used

sticky, liquid, organic substances that usually harden, upon exposure to air, into brittle amorphous, solid substances copolymers of up to 20 amino acids; perform a myriad of functions in all living tissue Proteins Synthesizing Polymers Polymerization first stage in manufacturing plastics bulk polymerization solution polymerization interfacial polymerization monomer alone is polymerized (either in gaseous or liquid phase) emulsion is formed and then coagulated monomers are dissolved in two immiscible liquids and polymerization occurs at the interface of the two liquids Processing Plastics Shellac Amber Wool Silk Natural Rubber Cellulose Two Principal Types of Polymerization 1. Step growth polymerization 2.Chain growth polymerization 1. Step growth polymerization sometimes called
involves monomers containing a carbon-carbon double bond that add end to end
very fast reaction – up to 104 times faster than condensation polymerization addition polymerization
Produces a variety of polymer chain lengths

Produce a small by-product molecules such as water, ammonia, and glycol CONDENSATION
Produce only specific lengths

No by-products ADDITION REACTIONS 2. Chain growth polymerization relatively slow
reaction can be stopped anytime and low molecular weight products, called , can be isolated
is the most common kind of step growth polymerization oligomers, 1. Step growth polymerization Condensation polymerization v II. Additives Antioxidants Antistatic Agents Pigments and Dyes Plasticizer Filler Stabilizers Blowing agents Catalysts Accelerators Fire-retardants Additives chemical additives are often used in plastics to produce some desired characteristics o Polymer + Additives/Modifiers = Plastic Compounds They provide additional properties for applications strength
density
color
thermal properties
cost, etc. many plastics are manufactured as composites, usually fibers made of glass or carbon are added to a plastic resin matrix most important additive, usually an organic liquid, is a suitable chemical chosen to increase flexibility of the plastic makes it easier for plastics to enter and flow around a mould also called almost always used in thermosetting plastics to make them less brittle and to reinforce their strength extenders added to plastics to lower cost, modify viscosity and improve physical properties Kaolin (clay) wood flour talc cotton lower materials cost, more product per pound of plastic (polymer) and improved heat resistance lower mechanical properties than unfilled plastics Advantage Disadvantage they counteract decomposition of polymers during manufacture e.g. Polyvinylchloride (PVC) – liable to decomposition 3 categories of Stabilizers Thermal stabilizers Plasticizers Ultraviolet (UV) Light Stabilizer (cc) image by nuonsolarteam on Flickr improve long term stability of heat-sensitive plastics when exposed to heat many thermoplastics fade or physically degrade when exposed to sunlight by neutralizing Van der Waals forces “new car smell” the milky mist on the side of the windshield Responsible for UV resistance for it to be suitable for exterior applications added to give color the amount added is relative to the color of the base plastic (the darker the base plastic, the more colorant is required)
e.g. white colorant (titanium dioxide) – plastic can become stiffer and less flexible
black colorant (carbon black) – can increase rigidity Disadvantage: affects other properties all foamed plastics are basic resins with a blowing agent introduced heat converts the blowing agent into gas bubbles expanding the resin into a foam helps to start the chemical reaction of polymerization and curing or "initiators" organic peroxides are used to polymerize and cross-link plastics in addition to thermosetting plastics also a chemical which speeds up the process of curing
sometimes referred to as hardener flame- retarding grades of plastic are produced either by the addition of a fire-retardant to the mix or by application afterwards plastics burn; added to prevent plastic from supporting a flame compounds that when heated will generate a gas that starves a flame (removes available oxygen) and
plastics that are more flame-retardant than the selected plastic two main categories: chemical substances that combat or stop oxidation

phenolic and amine materials Primary antioxidants: -Disadvantage of plastics: dielectric ability; they do not conduct electricity. This becomes a problem when static electricity needs to be dissipated - proven helpful in recording industry because static charges attracts dirt and dusts in compact discs
- used in anti-cling fabric softener dryer sheets
- developed for packaging and electronic industries Types: Internal External Ion discharge To sum up.. Plastics Resins Additives . I
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