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Polycarbonate PC

We are grateful to DSM for their assistance in the preparation of this materials page. For more information click on www.dsmep.com . Alternatively email chris.jesson@dsm.com

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.

PROPERTIES

Polycarbonates are strong, stiff, hard, tough, transparent engineering thermoplastics that can maintain rigidity up to 140oC 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 135oC 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.
 

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:

 

 

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 oC
Density 1.20 g/cm3


RESISTANCE TO CHEMICALS

Dilute Acid ***
Dilute Alkalis *
Oils and Greases **
Aliphatic Hydrocarbons ***
Aromatic Hydrocarbons *
Halogenated Hydrocarbons *
Alcohols ***

KEY * poor ** moderate *** good **** very good

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

For a more in-depth look at full range of properties and how this varies with grade, please visit www.dsmep.com

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

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:

 


u>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.


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:

 

CURRENT CASE STUDIES

 

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


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.

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CASH DISPENSER

DSM has developed a special range of Xantar Polycarbonate grades, suitable for structural foam injection moulding. This processing techniques makes it possible to attain a cost saving of up to 300%, when changing from cast aluminium to plastic moulding.

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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.

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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.

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History of PC and DSM Engineering Plastics
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.

DSM Engineering Plastics has been producing Polycarbonate products for more than 30 years. The products are sold under the tradename Xantar®. Xantar products have found uses in automotive, electrical/electronics, consumer, and packaging applications worldwide.

Xantar® C is a family of products based on blends of PC and ABS in different Ratios, also containing flame retardant grades, whereas Stapron E is the trade name of blends of PC with polyesters (Arnite PET and PBT).

DSM Engineering Plastics is a Business Group in the performance materials cluster of DSM, with sales in 2000 of 590 m € and 1300 employees worldwide. It is one of the world's leading players in the field of engineering thermoplastics offering a broad portfolio of high performing products.

DSM Engineering Plastics operates in all major markets of the world including the Americas, Asia, and Europe. Within each region customers can count on our innovative research, development, and support facilities. Our in-house resources are backed by a corporate research and development center that is utilized in creating new solutions for customer needs. The advanced level of account management, in combination with our effective global communication network secures the support of customer needs wherever it is required. With polymerization and compounding facilities for a range of polyamides, polyesters and polycarbonates, we serve our global customers' base and assure a constant, reliable supply of products.

We are grateful to DSM for their assistance in the preparation of this materials page. For more information click on www.dsmep.com . Alternatively email CSC-UK.DEP@dsm.com
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