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Comprehensive Guide on Polyvinyl Chloride (PVC)

Polyvinyl Chloride (PVC) Polyvinyl Chloride (PVC or Vinyl) is a high strength thermoplastic material widely used in pipes and medical devices but list is endless. It is the world's third-most widely produced synthetic plastic polymer... But, what is PVC? What it is made up of? How to process it?

Get technical information on Polyvinyl Chloride, explore methods used to produce it and main types of additives used! Also, learn about key features, conditions to process this polymer material and how to recycle it.

What is PVC?


Polyvinyl Chloride (PVC or Vinyl) is an economical and versatile thermoplastic polymer widely used in building and construction industry to produce door and window profiles, pipes (drinking and wastewater), wire and cable insulation, medical devices etc. It is the world’s third largest thermoplastic material by volume after polyethylene and polypropylene.

Pipes Made from PVC 

It is a white, brittle solid available in powder form or granules. Thanks to its versatile properties such as lightweight, durable, low cost and easy processability, PVC is now replacing traditional building materials like wood, metal, concrete, rubber, ceramics, etc. in several applications.

» View all PVC commercial grades and suppliers in Omnexus Plastics Database

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PVC was first made in 1872 by German chemist Eugen Baumann. The polymer appeared as a white solid inside flasks of the newly discovered vinyl chloride gas that had been left exposed to sunlight.

Polyvinyl Chloride is available in two broad categories:

  • Plasticized or Flexible PVC or PVC-U (Density: 1.1-1.35 g/cm3): Addition of compatible plasticizers to PVC lowers the crystallinity and by acting like lubricants, yields a much clearer and flexible plastic.

  • Unplasticized or Rigid PVC or PVC-P (Density: 1.3-1.45 g/cm3): It is a stiff and cost effective plastic material with high resistance to impact, water, weather, chemicals and corrosive environments.


Key Facts about Rigid and Flexible PVC


Strengths Limitations
Rigid PVC
  • Low cost & high stiffness
  • Intrinsic flame retardant
  • FDA compliant & also suitable for transparent applications
  • Better chemical resistance than plasticized PVC
  • Good electrical insulation & vapor barrier properties
  • Good dimensional stability at room temperature
  • Difficult to melt process
  • Limited solvent stress cracking resistance
  • Becomes brittle at 5°C (when not modified with impact modifiers and/or processing aids)
  • Low continuous service temperature of 50°C
Flexible PVC
  • Low cost, flexible & high impact strength
  • Good resistance to UV, acids, alkalis, oils and many corrosive inorganic chemicals
  • Good electrical insulation properties
  • Non-flammable & versatile performance profile
  • Easier to process than rigid PVC
  • Properties can change with time, due to plasticizer migration
  • Attacked by ketones; some grades swollen or attacked by chlorinated and aromatic hydrocarbons, esters, some aromatic ethers and amines, and nitro- compounds
  • Tends to degrade at high temperatures
  • Non suitable for food contact with some plasticizers
  • Lower chemical resistance than rigid PVC

  » Compare properties of Flexible PVC Vs. Rigid PVC in detail


PVC Manufacturing Process


In 1872, E. Bauman exposed vinyl chloride sealed in a tube to sunlight and produced a white solid called PVC. By World War I, Germany was producing a number of flexible and rigid PVC products which were used as a replacement for corrosion-resistant metals.

Vinyl chloride monomer (VCM) is produced from the chlorination of ethylene and pyrolysis of the resulting ethylene dichloride (EDC) in a cracking unit. PVC (glass transition temperature: 70-80°C) is produced by polymerization of vinyl chloride monomer (VCM).

Vinyl Chloride Monomer
Molecular Formula of Vinyl Chloride
C2H3Cl
Addition
Polymerization
PVC Polymerization
Polyvinyl Chloride Polymer
Molecular Formula of Polyvinyl Chloride
(C2H3Cl)n

The popular methods used to manufacture PVC commercially are: Suspension PVC (S-PVC) Process and Bulk or Emulsion (E-PVC) Process

Suspension Polymerization accounts for 80% of PVC production worldwide

Suspension PVC (S-PVC) Process


In pressure-tight reactor, the monomer is introduced with polymerization initiator and other additives. The content of the reaction vessel are mixed continuously to maintain suspension and ensure uniform particle size of PVC resin.

Typical suspension polymerized PVC has a mean particle size of 100-150 µm with a range of 50-250 µm.

S-PVC grades are formulated to meet an extensive range of requirements such as, high plasticizer absorption for flexible products, or high bulk density and good powder flow required for rigid extrusion

Bulk or Emulsion (E-PVC) Process


In this process, surfactants (soaps) are used to disperse the vinyl chloride monomer in water. The monomer is trapped inside soap micelles are protected by the soap and polymerization takes place using water soluble initiators.

The primary particles are solid, smooth surfaced spheres which are clustered into irregular shaped aggregates with a typical mean particle size of 40-50 µm with a range of 0.1-100 µm.

E-PVC resins are used in a wide range of specialty applications such as coating, dipping or spreading

Suspension PVC (S-PVC) Process Bulk or Emulsion (E-PVC) Process
  • Lower flexible PVC formula costs 
  • PVC particles obtained are mixed with plasticizers & can be extruded in pellets which are further used for processing via extrusion, calendering, injection molding... 
  • Processing equipment is typically very expensive
  • Higher flexible PVC formula costs 
  • PVC powder obtained is mixed with plasticizers to produce a paste which is further used for coatings, dipping, spraying... 
  • Processing Equipment may or may not be very expensive


Chlorinated PVC (CPVC)


CPVC is manufactured by chlorination of PVC polymer thereby raising the chlorine content from 56% to around 66%.

Chlorination of PVC reduces the forces of attraction between the molecular chains. CPVC is also essentially amorphous. Both of these factors allow CPVC to be stretched more easily and to a greater extent than PVC above its Tg. Pipe (436), moldings (376) and sheet are formulated for high temperature use based on CPVC or blends of CPVC and PVC.


Key Properties of PVC Polymer


  1. Electrical Properties: PVC is a good insulation material, thanks to its good dielectric strength 

  2. Durability: PVC is resistant to weathering, chemical rotting, corrosion, shock and abrasion. It is therefore the preferred choice for many long-life and outdoor products

  3. Flame Retardancy: Because of its high chlorine content, PVC products are self- extinguishing. Its oxidation index is ≥45. Antimony trioxide has been used extensively, usually in combination with phosphate ester plasticizers, giving excellent fire performance and mechanical properties.

  4. Cost/Performance Ratio: PVC has good physical as well as mechanical properties and henc provides excellent cost-performance advantages. It has long life span and need low maintenance 

  5. Mechanical Properties: PVC is abrasion-resistant, lightweight and tough 

  6. Chemical Resistance: PVC is resistant to all inorganic chemicals. It has very good resistance against diluted acids, diluted alkalis and aliphatic hydrocarbons. Attacked by ketones; some grades swollen or attacked by chlorinated and aromatic hydrocarbons, esters, some aromatic ethers and amines, and nitro- compounds

PVC resin obtained from polymerization is extremely unstable due to low thermal stability & high melt viscosity. It needs to be modified before processing into finished products. Its properties can be enhanced/modified by adding several additives such as heat stabilizers, UV stabilizers, plasticizers, impact modifiers, fillers, flame retardants, pigments, etc. It shows a wide spectrum of properties ranging from the extremely rigid to very flexible.

Selection of these additives to enhance polymer properties is dependent on end application requirement. For example:

  1. Plasticizers (Phthalates, Adipates, Trimellitate, etc.) are used as softening agents to enhance rheological as well mechanical performance (toughness, strength) of vinyl products by raising the temperature. Factors that affect the selection of plasticizers for vinyl polymer are:

    • Polymer Compatibility
    • Low Volatility
    • Cost
    Flexible PVC Pipe 

    Flexible PVC Pipe

    Explore more about plasticizers for polymers, various chemical types, regulatory updates & more to select right additive for your application

  2. PVC has a very low thermal stability and stabilizers help prevent degradation of polymer during processing or exposure to light. When subjected to heat, vinyl compounds initiate a self-accelerating dehydrochlorination reaction and these stabilizers neutralize the HCl produced enhancing the life of polymer. Factors to be considered while selecting heat stabilizer are:

    • Technical requirements
    • Regulatory Approval
    • Cost

  3. Fillers are added in PVC compounds for a variety of reasons. Today, a filler can be a true performance additive by delivering value in new and interesting ways at the lowest possible formulation cost. They help to:

    • Increase stiffness and strength
    • Improve impact performance
    • Add color, opacity and conductivity
    • And more..

    Calcium carbonate, titanium dioxide, calcined clay, glass, talc etc. are common types of fillers used in PVC.

  4. External lubricants are used to assist smooth passage of PVC melt through processing equipments. while internal lubricants reduce melt viscosity, prevent overheating and ensure good color of product

  5. Other additives like processing aids, impact modifiers, are added to enhance mechanical as well as surface properties of PVC

Rigid PVC: Maximizing Performance to Cost Ratio


PVC Blend with Other Thermoplastics


PVC/Polyester Blends – These blends combine superior physical properties of polyesters with the excellent processing characteristics of PVC. Benefits include abrasion resistance, tensile properties and tear resistance.

PVC/PU Blends – These blends offer increased abrasion and chemical resistance. Some TPUs are biocompatible and when blended with PVC results in valuable products for PVC industry

PVC/NBR Blends – Flexible PVC modified with NBR are melt processable yet possess good elasticity/recovery characteristics

PVC/polyolefin rubber alloys - They have potential utility in many applications where conventional flexible vinyl compounds do not meet certain end-use performance requirements.


Limitations of Polyvinyl Chloride


  • Poor heat stability
  • Properties can change with time, due to plasticizer migration
  • Flexible PVC has lower chemical resistance than rigid PVC
  • Rigid PVC has low continuous service temperature of 50°C


Application of PVC Resin


Commercially, PVC is one of the most important thermoplastics in the world today. Rigid (unplasticized) PVC is one of the most widely used plastic materials. Main Applications of both types of PV (rigid and flexible) include:

Applications of PVC

Application Rigid PVC Flexible PVC
Construction Window Frames, Pipes, House Siding, Ports, Roofing Waterproof Membranes, Cable Insulations, Roof Lining, Greenhouses
Domestic Curtain Rails, Drawer Sides, Laminates, Audio and Videotape Cases, Records Flooring, Wall Coverings, Shower Curtains, Leather Cloth, Hosepipes
Packaging Bottles, Blister Packs, Transparent Packs and Punnets Cling Film
Transport Car Seat Backs Under Seal, Roof Linings, Leather Cloth Upholstery, Wiring Insulation, Window Seals, Decorative Trim
Medical - Oxygen Tents, Bags And Tubing For Blood Transfusions, Drips and Dialysis Liquids
Clothing Safety Equipment Waterproofs for Fishermen and Emergency Services, Life-Jackets, Shoes, Wellington Boots, Aprons and Baby Pants
Electrical Insulation pipes, Jacketing, Electricity Distribution Boxes, Switches, Transparent Distributor Box Housings, Plug Housings & Battery Terminals Cable & Wire insulation, plugs, cable jackets, sockets, Sable Heads and Distributors
Others Floppy-Disk Covers, Credit Cards, Traffic Signs Conveyor Belts, Inflatables, Sports Goods, Toys, Garden Hoses


Processing of Vinyl Plastic


Some of the main processes include extrusion, calendering, injection molding, stretch blow molding, etc.

The intimate mixing of the PVC resin with its associated additives is necessary prior to converting into a thermoplastic melt. Thermal stabilization is required for processing rigid PVC, otherwise material may decompose during processing. Also, spray, blush & peel are very common molding defects associated with rigid PVC…Learn systematic methods to solve routine molding issues!

PVC is sensitive to the thermal history and the window of processing temperatures is quite small. Drying before processing is highly recommended, moisture rate should be lower than 0.3%.

Drying before processing is highly recommended for plasticized PVC, moisture rate should be lower than 0.3%.

Plasticized PVC Rigid PVC
Injection Molding
  • Melt temperature: 170 and 210°C 
  • Mold temperatures: 20 to 60°C
  • Mold shrinkage: 1 and 2.5% 
  • Material Injection Pressure: Up to 150 MPa
  • Packing Pressure: Up to 100 MPa
  • Melt temperature: 170 and 210°C. 
  • Mold temperatures:20 to 60°C
  • Mold shrinkage: 0.2 and 0.5%. 
  • Recommended Screw with an L/D ratio of 15 to 18
Extrusion
  • Extrusion temperatures are 10-20°C below injection molding temperatures in order to avoid premature thermal degradation. 

PVC has largely been overlooked as being suitable for 3D printing, and the new developments are opening the way for PVC into the growing world of additive manufacturing. For example, Chemson Pacific Pty Ltd, a Vinyl Council of Australia member, demonstrated a world-first for 3DVinyl™ PVC material by 3D printing a giant flower vase using a pellet-fed 3D-printer.

PVC material can be bonded using different joining techniques to fabricate PVC into the finished article. All welding techniques involve the application or generation of heat to soften the material whilst pressure is applied simultaneously. Bonding techniques, involving adhesives, are also common.


Plasticized PVC: How to Troubleshoot Adhesive Failures


Recyclability and Toxicity of PVC


Products made from PVC are 100% recyclable and can be identified as recycling code #3.

PVC Resin Identification Code 

Adopting an appropriate recycling pathway is of both an economic value and an environmental benefit. Two key methods include:

  • Mechanical Recycling – After mechanical separation, grinding, washing and treatment to eliminate impurities, it is reprocessed using various techniques (granulated or powder) and reused in the production
  • Feedstock Recycling – It involves (usually) thermal treatment of the PVC waste stream with recovery of hydrogen chloride that can then be returned to the PVC production process or used in other processes

PVC Recycling - Benefits

Recycled PVC can be used to produce packaging, film and sheet, loose-leaf binders, pipes, carpet backing, electrical boxes, cables and more.

The industry is working with the regulatory authorities to ensure that recycling activities remain sustainable while complying with the regulatory regime.

Presence of chlorine content and use of additives such as plasticizers bought PVC under scrutiny for a number of years. Concerns have been raised at regular intervals, in several regions, regarding the possible negative impact of phthalates on the environment and human health. However, on further investigations and studies certain phthalates are now confirmed safe for use in current applications.

Similarly, Europe has phased out use of lead-based stabilizers in vinyl compounds due to their classification as reprotoxic, harmful, dangerous for the environment and their presence (heavy metal) causing issues in waste management strategies.


Properties Comparison: Flexible PVC Vs. Rigid PVC


Keeping information about the properties of a thermoplastic beforehand is always beneficial. This helps in selecting the right engineering thermoplastic for a particular application. It also assists in evaluating if the end use requirement would be fulfilled or not.

The table below comprises of all relevant properties of Flexible PVC and Rigid PVC. From physical properties, dimensional stability, electrical performances to fire and thermal properties, find out every possible attribute with its values here.

Property Plasticized (Flexible) PVC Unplasticized (Rigid) PVC
Dimensional Stability
Coefficient of Linear Thermal Expansion 5-20 x 10-5 /°C 5-18 x 10-5 /°C
Shrinkage 0.2-4% 0.1-0.6%
Water Absorption 24 hours 0.2-1% 0.04-0.4%
Electrical Performances
Arc Resistance - 60-80sec
Dielectric Constant 3-5 3-4
Dielectric Strength 10-30kV/mm 10-40kV/mm
Dissipation Factor 400-1600 x 10-4 60-200 x 10-4
Volume Resistivity 10-16 x 1015 Ohm.cm 15-16 x 1015 Ohm.cm

Fire Performances

Fire Resistance (LOI) 20-40% 40-45%
Flammability UL94 HB V0
Mechanical Properties
Elongation at Break 100-400% 25-80%
Flexibility (Flexural Modulus) 0.001-1.8GPa 2.1-3.5GPa
Hardness Rockwell M 1 1-70
Hardness Shore D 15-70 65-90
Stiffness (Flexural Modulus) 0.001-1.8GPa 2.1-3.5GPa
Strength at Break (Tensile) 7-25MPa 35-60MPa
Strength at Yield (Tensile) 4-7MPa 35-50MPa
Toughness (Notched Izod Impact at Room Temperature) - 20-110J/m
Young Modulus 0.001-1.8GPa 2.4-4GPa
Optical Properties
Haze 3-5% -
Transparency (% Visible Light Transmission) 75-85% 80%
Physical Properties
Density 1.3-1.7g/cm3 1.35-1.5g/cm3
Glass Transition Temperature -50--5°C 60-100°C
Radiation Resistance
UV Light Resistance Fair Fair
Service Temperature
Ductile / Brittle Transition Temperature -40--5°C -10-1°C
HDT @0.46 Mpa (67 psi) 30-56°C 57-80°C
HDT @1.8 Mpa (264 psi) 30-53°C 54-75°C
Max Continuous Service Temperature 50-80°C 50-80°C
Min Continuous Service Temperature -40--5°C -10-1°C
Others
Sterilization Resistance (Repeated) Poor -
Thermal Insulation (Thermal Conductivity) 0.16W/m.K 0.16W/m.K
Chemical Resistance
Acetone Plasticized PVC Properties Non Satisfactory
Ammonium hydroxide @ 30%, Plasticized PVC Properties Satisfactory
Ammonium hydroxide @ diluted, Plasticized PVC Properties Satisfactory
Ammonium hydroxide @ diluted, 60°C Limited
Aromatic hydrocarbons @ Plasticized PVC Properties Non Satisfactory
Aromatic hydrocarbons @ hot conditions Non Satisfactory
Benzene Plasticized PVC Properties Non Satisfactory
Butylacetate Plasticized PVC Properties Non Satisfactory
Butylacetate @ 100%, 60°C Non Satisfactory
Chlorinated solvents @ Plasticized PVC Properties Non Satisfactory
Chloroform @ Plasticized PVC Properties Non Satisfactory
Dioctylphtalate @ 100%, 100°C Non Satisfactory
Dioctylphtalate Plasticized PVC Properties Non Satisfactory
Dioctylphtalate @ 100%, 60°C Non Satisfactory
Ethanol @ 96%, Plasticized PVC Properties Non Satisfactory Satisfactory
Ethyleneglycol (Ethane diol) @ 100%, 100°C Non Satisfactory
Ethyleneglycol (Ethane diol) Plasticized PVC Properties Satisfactory
Ethyleneglycol (Ethane diol) @ 100%, 50°C Satisfactory
Glycerol Plasticized PVC Properties Satisfactory
Hydrogen peroxide @ 30%, 60°C Satisfactory
Kerosene @ Plasticized PVC Properties Satisfactory
Methanol Plasticized PVC Properties Satisfactory
Methylethyl ketone Plasticized PVC Properties Non Satisfactory
Mineral oil @ Plasticized PVC Properties Satisfying
Phenol @ Plasticized PVC Properties Limited
Soap @ Plasticized PVC Properties Satisfying
Soap @ 60°C Limited
Sodium hydroxide @ <40%,> Satisfying
Sodium hydroxide @ <40%,> Limited
Sodium hydroxide @ 10%, Plasticized PVC Properties Satisfying
Sodium hydroxide @ 10%, 90°C Non Satisfactory
Sodium hypochlorite @ 20%, Plasticized PVC Properties Satisfying
Strong acids @ concentrated, Plasticized PVC Properties
Toluene @ Plasticized PVC Properties Non Satisfactory
Toluene @ 60°C
Xylene @ Plasticized PVC Properties


Commercially Available PVC Grades






Polymer Application Check Latest News About PVC Now!


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1 Comments on "Comprehensive Guide on Polyvinyl Chloride (PVC)"
David P Jan 3, 2018
This is a great article. Another great posting from Arlington Machinery can be found here: https://www.arlingtonmachinery.com/blog/p.170518001/pvc-recycling-comes-into-its-own/

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