Polycarbonate (PC)

INTRODUCTION Transparency, excellent toughness, thermal stability and a very good dimensional stability make Polycarbonate (PC) one of the most widely used engineering thermoplastics. Compact discs, riot shields, vandal proof glazing, baby feeding bottles, electrical components, safety helmets and headlamp lenses are all typical applications for PC. Polycarbonate is most commonly formed with the reaction of bis-phenol A (produced through the condensation of phenol with acetone under acidic conditions) with carbonyl chloride in an interfacial process. PC falls into the polyester family of plastics. Polycarbonate remains one of the fastest growing engineering plastics as new applications are defined; global demand for PC exceeds 1.5 million tons. Looking to buy polycarbonate PC?

1 History of Polycarbonate
2 Properties
3 Grades Available
4 Physical Properties
5 Resistance to Chemicals
6 Applications
6.1 Electrical & Electronics (E&E)
6.2 Automotive
6.3 General Industries / Packaging
7 Case Studies
7.1 Automotive
7.2 Traffic Lights
7.3 Cash Dispenser
7.4 Baby Bottle
7.5 Mobile Phone
8 Looking to source PC or another polymer?

1 History of PC 

The discovery of Polycarbonate dates back to 1898 when Einhorn, a German chemist, observed the formation of an insoluble, infusible solid, while endeavouring to prepare cyclic carbonates by reacting hydroquinone with phosgene. In 1902, Bischoff and Hedenström obtained similar cross-linked, high-molecular-weight Polycarbonate; Dr WH Carothers extended work on the product. It was not, however, until 1953 that Bayer laboratories produced linear thermoplastic Polycarbonate of high molecular weight. In 1957 Bayer and General Electric announced independent development of PC and in the summer of 1960 both companies began commercial production.

 

2  Properties

Polycarbonates are strong, stiff, hard, tough, transparent engineering thermoplastics that can maintain rigidity up to 140°C and toughness down to -20°C or special grades even lower. The material is amorphous (thereby displaying excellent mechanical properties and high dimensional stability), is thermally resistant up to 135°C and rated as slow burning. Special flame retardant grades exist which pass several severe flammability tests.

Constraints to the use of PC include limited chemical and scratch resistance and it's tendency to yellow upon long term exposure to UV light. However these constraints can be readily overcome by adding the right additives to the compound or processing through a co-extrusion process.

3 Grades Available

Polycarbonate is available in a number of different grades dependent on the application and chosen processing method. The material is available in a variety of grades such as film, flame retardant, reinforced and stress crack resistant, branched (for applications requiring high melt strength) and other speciality grades. Also blends of PC are available with e.g. ABS or Polyesters, widely used in automotive industry. Processing of PC generally falls into:

• Injection Moulding
• Structural Foam Moulding
• Extrusion
• Vacuum Forming
• Blow Moulding

4 Physical Properties
 

Tensile Strength		70 - 80 N/mm²
Notched Impact Strength		60 - 80 Kj/m²
Thermal Coefficient of expansion		65 x 10-6
Max Cont Use Temp		125 °C
Density		1.20 g/cm3

 

5 Resistance to Chemicals 
 

Dilute Acid	Good
Dilute Alkalis	Poor
Oils and Greases	Moderate
Aliphatic Hydrocarbons	Good
Aromatic Hydrocarbons	Poor
Halogenated Hydrocarbons	Poor
Alcohols	Good

Note that these ratings are generalised. The resistance against specific substances can deviate and are dependent on temperature, applied stresses, exposure time etc.

6 Applications

In recent years Polycarbonate blends have become increasingly commercially important. PC is widely used in blends due to its excellent compatibility with a range of polymers. Typical blends include rubber modified PC, improving impact properties, PC/PBT blends, which allow toughness to be retained at lower temperatures and having improved fuel and weather resistance. Amongst the most significant are those incorporating ABS (Acrylonitrile Butadiene Styrene). PC/ABS blends exhibit high melt flow, very high toughness at low temperatures and improved stresscrack resistance compared to PC.

All Blends are produced using a compounding step to blend the polymers. This compounding technology is very important for creating the optimal morphology and interaction between the two phases. In combination with the right additive know-how (flame retardant, stabilisation, reinforcement) blends are obtained with an optimally balanced set of properties.

PC finds usage in a host of markets, notably in the automotive, glazing, electronic, business machine, optical media, medical, lighting and appliance markets

6.1 Electrical & Electronics (E&E)
The largest UK application for PC is in the optical media market (i.e. usage in computer and audio compact discs). This is followed by an assortment of sheeting and glazing applications. The rest of the market consists of electrical and electronics (hosting applications in the business machine and telecommunications market), followed by transportation (including automotive), appliances, packaging, and other miscellaneous uses.

Miniaturisation fast product cycles make the E&E market one of the most demanding for Engineering Plastics. Demands include high service temperature, spike temperature resistance, ductility and toughness in thin sections, and flammability. All of this must be delivered consistently throughout the world, with co-ordinated engineering, market development, and technical service. In the E&E market our materials are well suited to internal components and current carrying devices.

Typical examples of applications of technology are within:

• power distribution (covers and housings)
• connectors
• electrical household appliances
• mobile phones
• electrical chargers
• lighting
• battery boxes

6.2 Automotive
The use of Engineering Plastics in automotive applications is nearing its fiftieth anniversary. PC has been part of this history and continues to bring innovation, which allows automakers to produce lighter, stronger, and more durable components.

• Typical PC and PC-blend applications include:
• automotive lighting
• head lamp lenses
• dashboards
• interior cladding
• exterior parts (bumpers, bodypanels)

6.3 General Industries / Packaging
While automotive and E&E markets tend to drive the technological breakthroughs in materials, other industries develop their own unique uses for Engineering Plastics.

In most of these industries durability, cost effectiveness, and appearance are the driving factors in material selection. The largest of these markets include:

• power tools
• baby bottles
• water dispensers
• garden equipment
• furniture (office & institutional)
• sporting goods
• medical applications

7 CASE STUDIES

7.1 AUTOMOTIVE As consumers demand more luxurious car interiors, the use of textile covered components has increased over the past few years. The In-Mould-Covering process (IMC) is widely used in the automotive industry for the production of these parts Click here for more information on materials Click here for more information on applications

 

7.2 TRAFFIC LIGHTS By making use of advanced electronics and revolutionary LED technology, as well as adapting an integral approach for the housing and the lense, it was possible to develop the concept for a completely new concept in traffic lights. Click here for more information

 

7.3 CASH DISPENSER Polycarbonate grades, suitable for structural foam injection moulding are used in cash dispensers . This processing techniques makes it possible to attain a cost saving of up to 300%, when changing from cast aluminium to plastic moulding. Click here for more information

 

7.4 BABY BOTTLE Performance challenges for injection blow-moulded baby bottles. In applications such as baby bottles, plastic materials due to the inherent safety (unbreakable) and the design freedom they offer are increasingly replacing glass. Click here for more information

7.5 MOBILE PHONE Housing for GSM phones must have high impact strength in order to protect the electronics inside in the case of an accidental drop. This ductile behaviour and excellent surface appearance can be designed in a vast array of 'trendy' colours. Click here for more information

 

8 Looking to source PC or another polymer?

The British Plastics Federation have over 500 members many of which supply polycarbonate and other major polymers.  The BPF offer a free 'source a supplier' service - simply complete the form below and we will send you enquiry direct to companies who can supply you with the product you are looking for.

If you do not wish your enquiry to appear in the secure BPF members’ area, please submit your enquiry here instead.