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A Complete Guide to Polycarbonate (PC)

A Complete Guide to Polycarbonate (PC)

Polycarbonate is a thermoplastic material that offers manufacturers and designers opportunities for design freedom, aesthetics enhancements and cost reductions. PC is known for maintaining coloring and strength over the time, even in stressful conditions. Become an expert with this comprehensive guide and learn all essentials you need to know about this widely used polymer.

Overview

What is Polycarbonate?

What is Polycarbonate?

Polycarbonate is a high-performance tough, amorphous and transparent thermoplastic polymer with organic functional groups linked together by carbonate groups (–O–(C=O)–O–) and offers a unique combination of properties. PC is popularly used as an engineering plastic owing to its unique features that include:

  • High impact strength
  • High dimensional stability
  • Good electrical properties amongst others

Though the characteristics of polycarbonate are similar to polymethyl methacrylate (PMMA, acrylic), but polycarbonate is stronger, usable in a wider temperature range (Melting point: 155°C) but more expensive. As PC shows excellent compatibility with certain polymers, it is widely used in blends, such as PC/ABS, PC/ PET, PC/PMMA. Some of the common applications are compact disc, safety helmets, bullet-proof glass, car headlamp lenses, baby feeding bottles, roofing and glazing etc.

Facts to Know

Polycarbonate was first prepared in 1953 by Dr.H.Schnell of Bayer AG, Germany and by D.W. Fox of General Electric Company, USA.


Main Characteristics and Properties of Polycarbonate

Main Characteristics and Properties of Polycarbonate

PC is an ideal material well known and widely used in the industry for its versatile characteristics, eco-friendly processing and recyclability. Comprising a unique set of chemical and physical properties makes it suitable over glass, PMMA and PE.

Let’s discuss PC properties in detail:

  • Toughness and High Impact Strength – Polycarbonate has high strength making it resistant to impact and fracture, and further providing safety and comfort in applications that demand high reliability and performance. The polymer has density 1.2 – 1.22 g/cm3), maintains toughness upto 140°C and down to -20°C. Also, PCs are virtually unbreakable.

  • Transmittance – PC is an extremely clear plastic that can transmit over 90% of light as good as glass. Polycarbonate sheets are available in a wide range of shades that can be customized depending on an end-user application.

  • Lightweight – This feature allows virtually unlimited possibilities to OEMs to design as compared with glass. The property also allows to increase efficiency, make installation process easier and reduce overall transportation costs.

  • Protection from UV Radiations – Polycarbonates can be designed to block ultraviolet radiation and provide 100% protection from harmful UV rays.  

  • Optical Nature - For having amorphous structure, PC offers excellent optical properties. The refractive index of clear polycarbonate is 1.584.

  • Chemical Resistance – Polycarbonate exhibits good chemical resistance against diluted acids, aliphatic hydrocarbons and alcohols; moderate chemical resistance against oils and greases. PC is readily attacked by diluted alkalis, aromatic and halogenated hydrocarbons. Manufacturers recommend to clean PC sheets with certain cleaning agents which do not affect its chemical nature. It is sensitive to abrasive alkaline cleaners.

  • Heat Resistance - Offering good heat resistance, Polycarbonates are thermally stable up to 135°C. Further heat resistance can be improved by adding flame retardants without impacting material properties.



Strengths Limitations
  • Highly transparent. Offers light transmission as good as glass
  • High toughness even down to -20°C
  • High mechanical retention up to 140°C
  • Intrinsically flame retardant
  • Offers good electrical insulation properties that are not influenced by water or temperature
  • Possesses good abrasion resistance
  • Can withstand repeated steam sterilizations
  • Easily attacked by hydrocarbons and bases
  • Post prolonged exposure to water at over 60°C, their mechanical properties start to degrade
  • Proper drying is required before processing
  • Low fatigue endurance
  • Yellowing tendency post exposure to UV
Strengths and Limitations of High Heat Polycarbonate Grades


Other Properties:

Limitations of Polycarbonates 


Polycarbonates do have certain limitations that include:

  • Low fatigue endurance
  • Mechanical properties degrade after prolonged exposure to water at over 60°C
  • Attacked by hydrocarbons and bases
  • Proper drying before processing is needed
  • Yellows after long exposure to UV


Use of Additives or Thermoplastic Blends to Optimize Properties

Use of Additives or Thermoplastic Blends to Optimize Properties

Polycarbonates’ creep resistance can be improved with the addition of glass- or carbon-fiber reinforcements. 5-40% of GF reinforcements can improve creep resistance upto 28 MPa at temperature as high as 210°F. Reinforced grades have better tensile modulus, flexural- & tensile strength as compared to standard PC grades.

Adding additives can improve flame retardancy, thermal stability, UV light and color stability and several other properties. Coated polycarbonates sheets also show better weatherability, and mar- and chemical resistance.

  • Stabilizers based on benzotriazole are useful to stabilize PC against UV light and protect from UV degradation.
  • Phosphorous acid esters-based stabilizers are known to be effective to improve thermal stability of polycarbonate.
  • Several flame retardants, such as halogenated, phosphorous-based and silicone-based are widely used to attain the required UL performance, increase LOI and reduce the heat of combustion for PC products.

Polycarbonate blends are successful commercially for providing a right balance between performance and productivity.

PC/Polyester Blends: These alloys are suitable for applications where high chemical resistance is required. PC/PBT blends offer higher chemical resistance than PC/PET blends due to PBT’s higher crystalline behavior whereas PET blended grades offer superior heat resistance.

PC/ABS Blends: PC’s toughness and high heat resistance combined with ABS ductility and processability provide an excellent combination of properties.


How PC is Manufactured?

How PC is Manufactured?

Polycarbonates are manufactured by condensation polymerization of bisphenol A (BPA; C15H16O2) and phosgene (COCl2).

PC Manufacture

Common Methods to Produce Polycarbonate Parts


  • Extrusion
  • Injection molding
  • Blow molding
  • Thermoforming

PC is melted and forced into a mold with high pressure to give it the desired shape. Drying before processing is highly recommended: 2-4 hr at 120°C. Target moisture content should be a maximum of 0.02%.

In order to avoid material degradation, the ideal maximum residence time is between 6 and 12 minutes depending on the selected melt temperature. Two major techniques involved in polycarbonate processing are injection molding and extrusion.

Injection Molding 


Injection molding is most often used method to produce parts made from polycarbonates and their blends. Since polycarbonate is highly viscous, it is usually processed at high temperature to reduce its viscosity. In this process, the hot polymer melt is pressed through into a mold with high pressure. The mold when cools, gives the molten polymer its desired shape and characteristics. This process is generally used to manufacture polycarbonate bottles, plates etc. Since polycarbonate is a poor-flowing plastic, wall thickness should not be too thin.

Certain guidelines that need to be followed while processing polycarbonate by injection molding are mentioned below:

Resin Melt Temperature, °C Mold Temperature, °C Molding Shrinkage, %
PC 280-320 80-100 0.5-0.8
High Heat PC 310-340 100-150 0.8-0.9
Filled PC 310-330 80-130 0.3-0.5
PC/ABS 240-280 70-100 0.5-0.7
PC/PBT 250-270 60-80 0.8-1.0
PC/PET 260-280 60-80 0.6-0.8
Typical Settings for Injection-Molding Various Polycarbonate Resins

Extrusion 


In the extrusion process, the polymer melt is passed through a cavity which helps in giving it the final shape. The melt when cooled attains and maintains the shape acquired. This process is used to manufacture polycarbonate sheets, profiles and long pipes. Recommendations:

  • Extrusion Temperature: 230-260°C
  • L/D ratio of 20-25 is recommended

3D Printing 


Polycarbonate is the strongest thermoplastic material and an interesting choice as a 3D Printing filament. PC is a strong material and known for maintaining temperature resistance. Polycarbonate does not shatter like plexiglass.

  • Machine bendable at a room temperature
  • Printing temperature from 260 – 300°C
  • Recommended printing bed temperature of 90°C or higher
  • Print speeds : 30mm/s is ideal, can go up to 60 or 80mm/s

An Interesting Video on PC 3D Printing – Watch Today!
Credit: Polymaker

Polycarbonate material can be bonded using several techniques including solvent bonding, adhesive bonding or mechanical fastening. It is imperative to understand the quality requirements for adhesive bonding processes according to regulatory standard DIN 2304-1.


Is Polycarbonate Safe for Use? How to Recycle PC? 

Is Polycarbonate Safe for Use? How to Recycle PC? 

Polycarbonate plastic is a perfect material for baby bottles, refillable water bottles, sippy cups, and many other food and beverage containers. Though the safety of PC came under scrutiny as it is made with bisphenol A (BPA).

Research & government agencies worldwide continue to study the potential for low levels of BPA to migrate from polycarbonate products (material degradation in contact with water) into foods and beverages. These analyses have shown that potential human exposure to BPA from polycarbonate products in contact with foods and beverages is low and poses no known risk to human health.

Several regulatory authorities worldwide, such as US FDA, European Commission's Scientific Committee on Food, UK Food Standards Agency, have recognized safe use of PC for food contact applications but there are some studies as well which showed BPA to be a hazardous risk to health and hence, leading to the development of “BPA-free” polycarbonate products.

All applications made for Polycarbonate plastic is 100% recyclable and identified by recycling code “7”. One of the methods are chemical recycling where scrapped PC is reacted with phenol to produce monomers which are purified for further polymerization.

Polycarbonate Recycling

Researchers are also working to develop new processes for recycling polycarbonates into another type of plastic—one that does not release bisphenol A (BPA) into the environment when it is used or dumped into a landfill.

Development in Bio-based Polycarbonate


Many companies have developed bio-based polycarbonate poised to act as a drop-in substitute to synthetic counterpart in several end-use industries. Bio-PC has a similar molecular structure with enhance durability but there are certain limitations w.r.t production cost.

Development in Bio-based Polycarbonate

In the last few year several new developments were seen in the bio-based polycarbonate resins segment. They include:

DURABIO™ by Mitsubishi Chemical Corporation – It is a bio-based engineering plastic made from plant-derived isosorbide monomer. Its transparency and optical homogeneity surpass those of BPA (BisPhenol A) based conventional polycarbonate resin.

POLYSORB® Isosorbide by Roquette – It is a plant-based alternative solution to bisphenol A (BPA) that can be used as a monomer in polycarbonates synthesis. Isosorbide-based polycarbonates can be used to provide enhanced chemical and UV resistance and scratch resistance in the construction and automotive industries amongst others.

LEXAN™ PC resin based on Certified Renewable Feedstock by SABIC – It is a latest polycarbonate solution based on ISCC PLUS certified feedstock. Part of its TRUCIRCLE™ initiative of circular solutions, SABIC shows the significant reductions in carbon footprint (up to 50%) and fossil depletion impacts (up to 35%) during polycarbonate resin production based on renewable feedstock.

Recently, a breakthrough has been made at Korea Research Institute of Chemical Technology (KRICT) where researchers have created a bio-polycarbonate made largely from glucose. Unlike earlier bio-polymers, the team claims that this new bio-polycarbonate has the strength and durability to match its petrochemical counterpart, paving the way for commercialization.


Find Suitable Polycarbonate Grade

View a wide range of polycarbonate grades available in the market today, analyze technical data of each product, get technical assistance or request samples.

Key Applications

Key Properties

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