How PVC is Made
Stuff About How PVC Pipe
is Made You (Secretly) Always
Wanted to Know, but Were
Afraid to Ask
OK, my inquisitive and eager
students... time for a quick visit to "PVC University."
(Relax, there'll be no quizzes.)
PVC: Polyvinyl chloride
CPVC: Chlorinated polyvinyl chloride
PvdC: Polyvinylidene chloride
Polyvinyl chloride (PVC) is a
tough, strong thermoplastic material which has an excellent
combination of physical and electrical properties. The
products are usually characterized as plasticized or rigid
types. Polyvinyl chloride (and copolymers) is the second
most commonly used polyvinyl resins in one of the most
The plasticized types, either
soft copolymers or plasticized homopolymers, are somewhat
elastic materials which are familiar in the form of shower
curtains, floor coverings, raincoats, dishpans, dolls,
bottle-top sealers, prosthetic forms, wire insulations and
films, among others.
Rigid polyvinyl chloride
products, which may consist of the homopolymer, copolymer,
or polyblends, are used in the manufacture of phonograph
records, pipe, chemically resistant liners for
chemical-reaction vessels, and siding and window sashes.
The monomer is frequently
prepare from chlorine, acetylene, and ethylene by a
combination of processes which affords complete utilization
of the chlorine. (There's a nice chemical diagram that I
won't bore you with... I can tell you're already yawning.)
The polymerization of vinyl
chloride, chemical reaction, and its copolymerization with
other vinyl monomers may be initiated by peroxide or azo
compounds and carried out in bulk or in aqueous emulsion or
suspension systems. The structure and properties of the
product are quite dependent on polymerization temperature;
the lower the temperature, the higher the softening point of
the resin. Polymers prepared in bulk or suspension are used
for many applications as molded, extruded, or calendered
objects. Polymers prepared in emulsion are often molded by
dipping or pouring techniques.
Because polyvinyl chloride
products have a tendency to lose hydrogen chloride at high
temperatures, a stabilizer, such as a tin or lead compound,
is included in the final composition. Fillers are also
Copolymers with monomers, such
as vinyl acetate or propylene can be processed at lower
temperatures than the homopolymer. The acetate copolymer is
especially useful in floor tiles, though homopolymers are
used as well.
Blends or "alloys" of
polyvinyl chloride with small amounts of rubbery materials,
such as the interpolymer of acrylonitrile, butadiene, and
styrene (ABS) have been produced for applications such as
panels and pipe in which impact resistance, as well as
hardness and strength, is desired.
Chlorination of polyvinyl
chloride is sometimes effected to obtain a stiffer resin at
the expense of processability.
Are you with me so far? If so,
you deserve a break. Go ahead, stand up and stretch your
legs. I'll wait.
Back so soon?
OK, moving along...
PVC is the most common of all
vinyl polymers. The polymer of vinyl chloride, PVC, is
produced by three basic processes...
1. Mass Process
Vinyl chloride is polymerized in a carrying medium. The
polymerization is stopped at a low conversion and the
polymer is separated from the residual monomer which is
2. Emulsion Process
Vinyl chloride is emulsified with water by use of
emulsifying agents. The polymerization is carried out to a
high degree of conversion with a small amount of recovered
monomer being recycled. The product is obtained as an
emulsion or spray and dried to produce a very fine powder.
3. Suspension Process
Vinyl chloride is suspended as small droplets of monomer in
water and then polymerization is carried to a high degree of
conversion. A small amount of monomer is recovered and
recycled. A granular product is obtained by centrifuging and
drying. While a range of products can be made by the first
two methods as above, they are generally limited to
specialty products which are difficult to impossible to make
by the suspension process. The largest proportion of PVC is
produced, particularly in the USA, the by suspension process
because it requires the least capital investment and has the
lowers operation costs.
Advantages and Limitations of
PVC and Related Polymers
Mechanical Properties: Good combination of stiffness
and impact strength (rigid formulation), toughness,
extensibility, high ratio of strength to weight (flexible
formulations). Acrylic-PVC alloy with high impact strength
available. Limitations are recovery from bending or
stretching damped compared to rubber. Comparatively low heat
distortion and softening temperature (even rigid
compositions - except CPVC).
Physical Properties: Good electrical insulation
(enhanced by suitable formulation).
Non-flammability (reduced or enhanced by some plasticizer)
limitations are the tendency to progressive degradation at
elevated temperatures. Stiffening and embrittlement at low
temperatures (rigid compositions) and flexible unless
Application to Food and Medicine: PVC and PvdC used
in packaging applications. Blown bottles and containers also
made from PVC (non-toxic grades).
Formulation and Processing: Formulation versatility
giving materials ranging from elastomers to rigid
engineering thermoplastics and processing possibilities from
paste coatings to injection molding. Limitation is that
adhesion to many substrates limited in the absence of a
Miscellaneous: Dimensional stability at room
temperature for rigid formulations. Almost unlimited range
of colors - transparent to opaque according to formulation.
Low cost. Limitation is the high specific gravity for
Comparison of Characteristics of
PVC and Related Polymers
PVC (Flexible): Wide range of flexibility possible -
competes for rubber applications at lower cost. Ability to
form pastes (plastisols) by addition of plasticizers for
coating and casting. Limitations are that flexible grades
are most susceptible to staining, chemical and
microbiological attack due to presence of plasticizers.
Creep properties are inferior to rigid PVC.
PVC (Rigid): Lower coefficient of friction and better
abrasive wear resistance than flexible grades. Easier to
process and cheaper than CPVC. Can be glass fiber-reinforced
to give improved strength and stiffness and lower
coefficient of thermal expansion. Limitations are that it is
attacked by strong acids and alkalix, swollen hydrocarbons
and it has a lower maximum service temperature than CPVC.
PVC Copolymners (Less Rigid than Rigid PVC):
Processing characteristics and impact strength improved by
blending with copolymers. Limitations are that creep
properties are generally inferior to rigid PVC, and lower
CPVC (Rigid): Considerably higher upper service
temperature than rigid PVC. Best creep properties of PVC
types. Resistant to acids, alkalis, most organic solvents,
oil and grease. Limitations are that it's more difficult to
process than PVC due to higher softening point and melt
viscosity and it has higher cost.
PvdC (Flexible): Best resistance to all acids and
most common alkalis. Unaffected by aromatic and aliphatic
hydrocarbons, alcohols and esters. Best resistance to
permeation by organic and aqueous vapors. Limitations are
that it has higher cost and thermal processing is more
Typical Applications of PVC
Rigid Piping: Potable water conduits, water mains, drainage,
soil pipe systems, rain water systems and gutters, gas
conduits, venting, furniture and crafts.
Rigid Structural and Cladding Elements: Paneling and
partitioning (interior), wall cladding (exterior), building
panels, glazing, roofing, window frames and hollow bricks.
Flexible Misc. Products: Flexible "see through" doors,
folding doors, roof underlayment, greenhouse glazing,
suspended ceilings and floorings (continuous and tiles).
Flexible insulation and sheathing (wire and cable), batter
separators. Rigid terminal boxed and conduit.
Rigid Foil (Thin Sheeting): may be fabricated into
containers, blister and skin packs, nesting trays (for
confectionary and cookies/crackers).
Flexible Film: used directly for wrapping food and other
products and "shrink" or "cling" wrap.
Rigid Blown Bottles and Containers: used for oil, wine,
beverages, shampoos, and certain cosmetics.
Coated Fabric and Paper Applications (Flexible)
Leather Cloth: used in upholstery, clothing, travel and
fancy goods. Protective and foul weather clothing.
Tarpaulins, life rafts, hover rafts, conveyer belts.
Rigid Foam: used as a core in sandwich structure (building
and boat building), buoyancy blocks, fishing floats,
insulation (thermal and acoustic) and shock absorbent
Flexible Foam: upholstery (especially automotive), leather
cloth and fancy goods, carpet backing, underlays, embossed
wall papers, foam flooring, shoe soles and soft toys.
Some of these find application in adhesive and thin
protective coatings (i.e. paints). Those vinyl chloride
copolymers which are of direct interest to the product
designer are used mainly where a rigid polymer with PVC-like
service properties are required, but where easier thermal
processing is necessary. This type of copolymer is also the
material of vinyl sheeting used for thermoforming, which
must combine rigidity with easy heat-softening under
fabricating conditions. Vinyl chloride/acrylic ester
copolymer has been used as the material of blow molded
bottles and film, for improved impact strength and/or heat
CPVC: The principal use for this material in in hot water
pipes where its combination of generally PVC-like properties
with a much higher softening point makes it particularly
PvdC: The most important application of this material is as
a coating or laminate component imparting good gas,
moisture, vapor, scent and flavor barrier properties to
plastic packaging films and containers. Heat-shrinkable and
heat-sealable films have been produced from PvdC, as well as
heat-sealable layers or coating on other polymer films. The
solvent resistance of PvdC pipes has been utilized in
special applications, as in chemicals installations and
apparatus. Use of extruded PvdC products in this and other
fields also includes gaskets, valve seats, tape for wrapping
joints and conveyer belts. PvdC moldings are represented by
spray-gun handles, acid dippers and components in equipment
for rayon manufacture.
Processing of PVC and Related Polymers
Calendering: Sheet, film (flexible or rigid), flooring and
floor tiles (flexible)
Extrusion: Sheet, film, pipe, profiles (all flexible or
rigid), coated wire and cable (flexible coating)
Compression molding: Thin sheeting or laminates, cellular
Injection molding: Pipe fittings, electrical fittings,
gaskets, footwear (including micro cellular soles)
Blow Molding: Bottles and other containers
Paste Processing (Coating by Dipping, Spreading or Transfer
Techniques): Coated fabrics, vinyl wall-papers, PVC Backed
carpets, coated work gloves, coated metal sheet and articles
Powder Processing (Coating by Dripping or Spraying): Coated
metal sheet and wire trays
Powder Processing (Spreading on Temporary Support): Sintered
porous sheets for battery separators
Thermoforming: Blister packs, nesting trays, containers and
- fin -
that's about it. Not a complete chemistry lesson, of course.
But a little of the basics. Now that you know, do you really
What's important is, PVC makes
great projects. It's easy to work with; easy to cut, bend,
drill and form. PVC is a versatile material that gives you
endless ways to be creative and make some really neat
projects. That's why, although it's technically called
polyvinyl chloride, to me it's Pretty Versatile Construction
So be sure to surf around my
humble little site... choose a plan or two or three... and have
Wait... on second thought, if
you've read this far, maybe there WILL be a quiz!
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