Overview
PC colourless (polycarbonate) is an amorphous, crystal-clear engineering thermoplastic known above all for its exceptional impact strength – PC is considered virtually unbreakable and is used, among other things, for safety glazing and machine guards. It has no defined melting point, but softens above the glass transition temperature of around 147 °C. Well-known brand names for polycarbonate are Makrolon® and Lexan®.
PC colourless is the transparent, untreated standard grade of polycarbonate and thus the base material from which specialised Röchling trade grades such as Exolon GP and Exolon FR are derived: Exolon GP is a general-purpose grade for standard engineering PC applications, while Exolon FR is a flame-retardant PC grade for applications with elevated fire-safety requirements. While PC colourless sits in the standard flammability class UL 94 HB, flame-retardant grades (V-2/V-0, building material class B1) are also available in PC colourless for higher fire-safety requirements such as those covered by Exolon FR.
PC combines three properties that set it apart from other transparent plastics: exceptionally high impact strength ("no break" in the unnotched Charpy test), a high heat deflection temperature with continuous service up to about 120 °C, and good transparency of about 89 %. Mechanically, PC reaches a yield stress of about 60 MPa with a tensile modulus around 2,300 MPa and a density of about 1.20 g/cm³; characteristic is its high elongation at break (>80 %) and very high notched impact strength (about 65 kJ/m²) – PC is tough rather than brittle. Chemically, PC is sensitive: it is attacked by many solvents, alkalis and hydrocarbons and then tends to stress cracking; without UV protection it yellows outdoors.
Typical applications are safety and protective glazing, machine guard screens and protective shields, impact-resistant sight windows and visors, housings and insulating parts in electronics, and sterilisable medical and laboratory parts. Typical industries are mechanical and plant engineering, safety and glazing technology, electronics and electrical engineering, medical and laboratory technology, lighting and illumination technology, and the food industry.
Technical Data
| Property | Value | Test Standard |
|---|---|---|
| General Properties | ||
| Density | 1.20 g/cm³ | DIN EN ISO 1183-1 |
| Water Absorption (24 h) | 0.3 % | DIN EN ISO 62 |
| Flammability | HB (FR grades V-2 / V-0) | UL 94 |
| Building Material Class | B2 (flame-retardant grades: B1) | DIN 4102 |
| Optical Properties | ||
| Light Transmission (3 mm) | ~ 89 % | DIN 5036-3 |
| Refractive Index nD20 | 1.585 | DIN EN ISO 489 |
| Mechanical Properties | ||
| Yield Stress (23 °C) | 60 MPa | DIN EN ISO 527 |
| Elongation at Break | >80 % | DIN EN ISO 527 |
| Tensile Modulus | 2300 MPa | DIN EN ISO 527 |
| Flexural Strength | 90 MPa | DIN EN ISO 178 |
| Impact Strength (Charpy, unnotched) | no break | DIN EN ISO 179 |
| Notched Impact Strength (Charpy) | 65 kJ/m² | DIN EN ISO 179 |
| Ball Indentation Hardness | 110 MPa | DIN EN ISO 2039-1 |
| Thermal Properties | ||
| Glass Transition Temperature | ~ 147 °C | ISO 11357 |
| Vicat Softening Temperature | 145 °C | DIN EN ISO 306, Vicat B 50 |
| Heat Deflection Temperature | 130 °C | DIN EN ISO 75, Method A (HDT) |
| Long-term Service Temperature | -40 … 120 °C | Average |
| Short-term Service Temperature (max.) | 135 °C | Average |
| Coefficient of Linear Thermal Expansion | 65 · 10⁻⁶/K | DIN 53752 |
| Thermal Conductivity | 0.20 W/(m·K) | DIN 52612-1 |
| Electrical Properties | ||
| Volume Resistivity | >10¹⁵ Ω·cm | DIN EN 62631-3-1 |
| Surface Resistivity | >10¹⁵ Ω | DIN EN 62631-3-2 |
| Dielectric Strength | ~ 30 kV/mm | IEC 60243 |
Frequently Asked Questions about PC Colourless
1What is PC colourless?+
PC colourless (polycarbonate) is an amorphous, crystal-clear engineering thermoplastic known above all for its exceptional impact strength – PC is considered virtually unbreakable and is used, among other things, for safety glazing and machine guards. At the same time, with a continuous service temperature of up to about 120 °C, it is considerably more heat-resistant than acrylic glass (PMMA). Well-known brand names are Makrolon® and Lexan®.
2How is PC colourless machined at Liedtke?+
PC machines well – milling, turning, drilling and sawing produce clean, dimensionally accurate results. We also offer cold bending (line bending), thermoforming, polishing and bonding. Before thermoforming we pre-dry PC due to its hygroscopy; annealing after machining can relieve internal stresses. Because of its stress-cracking sensitivity, we avoid solvent-based cutting fluids.
3What determines the price of a PC colourless part?+
PC is a mid-priced engineering thermoplastic, usually above acrylic glass (PMMA) but below high-performance plastics. As a rough guide, semi-finished stock prices are in the range of about €6–15/kg. The component price is determined mainly by the semi-finished shape and dimension, material utilisation, machining effort and lot size. We are happy to quote binding prices on request based on your drawing.
4When is PC colourless not the right choice?+
Contact with solvents, alkalis or hydrocarbons risks stress cracking. For permanent outdoor use without UV protection, natural-coloured PC yellows; UV-stabilised grades or PMMA are preferable here. For scratch- and abrasion-loaded surfaces or the highest optical clarity without yellowing, PMMA is usually the better and cheaper choice.
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