synthetic polymer industries

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Synthetic Polymer

Industries

Notes for student use


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Plastic Industries


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Overview

A plastic is a material that contains a polymerizedorganic substance of large molecular weight as anessential ingredient, is solid in its finished state, and atsome stage in its manufacture or its processing into

finished articles can be shaped by flow.

The plastic industries have developed and grown then,since their discovery. Plastics can be used in variousapplications because of their toughness, waterresistance, excellent resistance to corrosion, ease offabrication, and remarkable color range.


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History

The development of commercial phenolic resin in 1909 byBaekland was the start of the synthetic plastic industry. Hisdiscovery stimulated the search for other plastics.

The first plastic of industrial significance was cellulosenitrate (Celluloid) and was discovered about the middle ofthe nineteenth century. It was first used in 1869 by Hyattwho was searching for an ivory substitute.


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Classification

Thermosetting plastics are processed by heatcuring to produce an infusible or insolubleproduct.

Thermoplastics are processed by heating tosoften them and cooling to harden them.

On the basis of derivation, they may also begrouped as natural resins, cellulose derivatives,protein products, and synthetic resins.


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Applications and UsesCommon Resin Types and Applications

Resin Type Applications

Polyesters Construction, auto repair putty, laminates, skis,

fishing rods, boats and aircraft component,

coatings, decorative fixtures, bottles

Polyurethanes Insulation, foam inner liners for clothing, rocket fuel

binders, elastomers, adhesives

Polyethers Coatings, pump gears, water-meter parts, bearing

surfaces, valves


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Epoxies Laminates, adhesives, flooring, linings, propellers,

surface coatings

Polyethylene Packaging films and sheets, containers, wire cable

insulation, pipe, linings, coatings, molds, toys,

housewares

Polypropylene Housewares, medical equipment (can be sterilized),

appliances, toys, electronic components, tubings and

pipes, fibers and filaments, coatings


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Polyvinyl chloride Pipe and tubing, pipe fittings, adhesives, raincoats

and baby pants, building panels

Acrylics Decorative and structural panels, massive glazing

domes, automotive lens systems, illuminated

translucent floor tiles, windows, and canopies

Polystyrene Insulation, pipe, foams, cooling towers, thin-walled

containers, appliances, rubbers, automotive

instruments and panels


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Plastics in Everyday Life


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Standard Symbols


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Raw Materials

Monomers: vinyl chloride, ethylene, propyleneand similar simple hydrocarbons

Chemical intermediates : phenol, formaldehyde,hexamethylenetetramine, phthalic anhydride,methyl acrylate and methacrylate

Other raw materials: plasticizers, fillers, andreinforcements are also added to alter theproperties of the plastic products.


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Manufacturing Processes

is carried out in the liquid or vapor state.

The monomers and activator are mixed in a reactor

and heated or cooled as needed.

Bulk

Polymerization

is used when the exothermic heat is too great to becontrolled in bulk polymerization.

The monomer and initiator are dissolved in a

nonreactive solvent which serves to slow the

reaction and thus moderate the heat given off.

SolutionPolymerization


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Manufacturing Processes

is the process where the monomer is suspended in

water by agitation.

stabilizers (i.e. talc, fullers earth, and bentonite) areadded to stabilize the suspension and prevent

polymer globules from adhering to each other.

Suspension

Polymerization

is similar to suspension polymerization but the monomer

is broken up into droplets that form aggregates called

micelles.

The monomer is on the interior of the micelles, and the

initiator is in the water. Soap or another emulsifying agent

is used to stabilize the micelles.

EmulsionPolymerization


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Polyethylene

It is the first and the largest in production ofpolyolefin plastic.

High-density polyethylene (HDPE), produced bylow-pressure methods, is used mainly for blow-molded containers and injection-molded articlesand pipe.

Low-density polyethylene (LDPE), produced byhigh-pressure methods, is used mainly for plasticfilms.


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Polyethylene


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The Process Flow of LDPE Production


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Individual Process Descriptions

1. Demethanization and Deethanization The

feed for the process is a mixture of methane,

ethane, and ethylene. Since ethylene is the

monomer to be used ethylene has to be

separated from methane and ethane. High

purity ethylene is used (99.8%).


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2. Compression of Ethylene and Catalyst -

Ethylene and the catalyst (free-radical yielding

such as oxygen or peroxide) are compressed

to operating pressure (150 MPa).


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3. Solution Polymerization In a tubular reactor

maintained at 190C, solution polymerization

occurs to convert ethylene to polyethylene.

About 30% conversion is achieved per pass.


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4. Pressure Separation

At this stage, the

unconverted ethylene is

removed and recycled.


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5. Extrusion and Pelletizing The polyethylene

is extruded and pelletized.


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6. Quench Cooling This hardens the

polyethylene pellets by addition of cold water.


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7. Water Separation and Drying These involve

the removal of water from the pellets to

obtain the final product.


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Man-Made Fiber and

Film Industries


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ClassificationAccording to Spinning Procedures

Melt spinning involves pumping molten polymer throughcapillaries or spinnerets and the polymer streams thatemerge are solidified by quenching in cool air.

In dry spinning, the polymer is dissolved in a suitableorganic solvent. The solution is forced through spinneretsand dry filaments are formed upon evaporation of thesolvent.

Wet spinning involves spinning of a solution of polymerand coagulation of the fiber in a chemical bath.


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Overview

Fibers were originally of natural origin and wereproduced from wool, silk, cotton, flax, and similarmaterials.

The first man-made fibers were made by Swan in1883 when he squirted a solution of cellulosenitrate in acetic acid through holes.

Fibers have three important general properties:length, crimp and denier.


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Synthetic Fibers and their

Applications

PolyamidesThey are used in home furnishings,especially carpets.

Acrylics and Modacrylics polyacrylonitrile is themajor component of several industrial textilefibers.

Spandex It is used in foundation garments,hose, swimwear and other elastic products.


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Vinyls and Vinylidines

Saran is the copolymer of vinyl chloride and andvinylidene chloride. It is resistant to mildew, bacterialand insect attack. Automobile seat covers and homeupholstery are its prime applications.

Vinyon is the trade name of copolymers of 90% vinylchloride and 10% vinyl acetate.Resistance to acids and alkalies, sunlight, and aging

makes Vinyon useful in heat-sealing fabrics andclothing.


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Other Synthetic Fibers

Polyolefins They excel in special cases, such as ropes,laundy nets, carpets, blankets and backing for tuffedcarpets, but are difficult to dye and their melting pointis low.

Fluorocarbons It is widely used in pump packings andshaft bearings.

Glass Fibersare used for electrical insulation inmotors and generators, structural reinforcement ofplastics, fire-proof wall coverings and tire cords.


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Multicomponent fibers

Multicomponent fibers have been prepared

which possess superior properties to either

component if spun alone. They correspond to

better dyeability, permanent crimp, or silklikefeel, etc.


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Finishing and Dyeing of Textiles

Dyeing, bleaching, printing, and special finishing (such as for crease

recovery, dimensional stability, resistance to microbial attack and

ultraviolet light) involve unit operations such as filtering, heating, cooling,

evaporation and mixing.


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Films

are made fromdifferentpolymers such aspolyesters,

polyvinyl chloride,etc.


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3 Common Types of Film Processing

Slit-die process

produces flat sheets by extruding themolten polymer through a slit-die into a quenchingwater bath or onto a chilled roller.

Blow-extrusion Process

produces tubular film byusing air pressure to force the molten polymer arounda mandrel.

Calendering

preparation of film is produced byfeeding a plastic mix of polymer, stabilizer, andplasticizers between two heated roll where it issqueezed into a film.


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Nylon 6.6

Nylon 6.6 was the first all-synthetic fiber made

commercially and opened up the entire field.

It is the product resulting from the

polymerization of adipic acid and

hexamethylene diamine.


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PFD for Nylon Production


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Raw Materials

The raw materials for fiber production are justthe same as in plastics production and willdepend on the type of material the fiber is madeup of.

For the production of nylon yarn, however, theraw materials cited are adipic acid andhexamethylene diamine (hexa).

Utilities such as steam and water will also beused.


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Individual Process Description

1. Nylon Salt Formation - The reaction between equimolar proportions

of the two raw materials produces nylon salt solution. Acetic acid is

added to the (hexa) to to stabilize chain length.


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2. Evaporation The water produced from the reaction is evaporated in an

evaporator and a jacketed autoclave.

In the jacketed autoclave, pure nitrogen at 175-345 kPa forces the

material downward. TiO2 dispersion is also added.


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3. Casting Wheel

Each 900-kg batch is extruded as rapidly as possible. A ribbon of polymer about 30 cm wide and 6 mm thick flows on the 1.8-m cat

drum.

Water sprays on the inside cools and harden the underside of the ribbon, theouter is cooled by air and water.


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Individual Process

Description

4. Blender and Hopper

The ribbons are cut into

small chips or flakes, blended and emptied to

hoppers.


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Melt Spinning A typical spinning unit is composed of a metal vesselsurrounded by a Dowtherm vapor heated jacket which keeps thetemperature of the vessel above melting temperature (263C).

As the nylon flake enters the vessel, it strikes a grid, where it melts andflows through to the melt chamber below.

The molten polymer passes through the portholes in this chamber to gearspinning pump.

They deliver it to a sand filter, which is followed by screens and a spinneret

plate.

The filaments are solidified by air and passed in a bundle through steam-humidifying chamber.


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Melt Spinning


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6. Cold Drawing

After lubrication on

a finish roll, the yarn is stretched

or drawn to the desired degree.

7. Bobbin The nylon yarn passes

through a bobbin system and is

shipped to various manufacturers

for processing.


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THANQ -

SALAMAT NG MARAMI. =)

Reference

Austin, G.T. Shreves Chemical Process

Industries (5th Ed). New York: McGraw-Hill, Inc., 1984.

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