Machining Exolon GP

Exolon® GP is made of polycarbonate, an amorphous engineering thermoplastic without a defined melting point that softens above the glass transition temperature (around 147 °C). Its outstanding feature is extreme toughness: in the unnotched Charpy test the material does not break ("no break"), and it remains impact-resistant even at low temperatures. Exolon® GP is stiff, dimensionally stable and transparent, yet comparatively soft and scratch-sensitive at the surface; chemically, PC is sensitive to many solvents.

Exolon® GP 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 the sheets due to their hygroscopy; after machining, annealing can relieve internal stresses. Because of its stress-cracking sensitivity, we avoid solvent-based cutting fluids. This is how we reliably produce impact-resistant, transparent precision and protective parts – from single pieces to series production.

Exolon® GP is worthwhile whenever transparency must be combined with shatter resistance, higher temperature or fire safety – for example:

• Safety and protective glazing, machine guard screens
• Impact-resistant sight windows, protective shields and covers
• Roofing and glazing in building and architecture
• Transparent components at temperatures above about 80 °C (up to 120 °C)
• Applications requiring flame-retardant material (B-s1,d0)

Exolon® GP is a solid PC sheet in the mid price segment and is usually above acrylic glass (PMMA) but below high-performance plastics. As a rough guide, sheet prices are in the range of about 6–15 €/kg. The component price is determined mainly by sheet thickness and dimension, material utilisation (offcut), machining effort and lot size. We are happy to quote binding prices on request based on your drawing.

Equally important are the limits of the material:

• Contact with solvents, alkalis or hydrocarbons (strong risk of stress cracking)
• Permanent outdoor use without UV protection – natural PC yellows; then UV-protected sheets or PMMA
• Scratch- and abrasion-loaded surfaces – PC is soft; then hard-coated grades, PMMA or glass
• Highest optical clarity and non-yellowing – then PMMA
• Very tight budget – PMMA is usually cheaper

An honest assessment – and how the disadvantages can be mitigated in practice: Advantages:

Disadvantages:

Practical tip: Exolon® GP plays to its strengths wherever transparency meets shatter resistance, fire safety and higher temperatures – for example in safety glazing, machine guards and roofing. Where highest scratch resistance, non-yellowing and weathering resistance are required, acrylic glass (PMMA) is the better and cheaper choice; for permanent outdoor use, we recommend UV-protected PC sheets.

• Extremely high impact strength – virtually unbreakable, even in the cold
• High heat deflection temperature (continuous up to ~120 °C, range -100…+120 °C)
• Flame-retardant (UL 94 V-2, EN 13501-1 B-s1,d0)
• Good transparency (~90 %) and high stiffness
• Good machinability, cold-bendable and thermoformable
• Soft, scratch-sensitive surface (without hard coating)
• Sensitive to solvents, alkalis and hydrocarbons (stress cracking)
• Only limited weathering resistance without UV protection (yellowing)
• Higher price and slightly lower clarity than PMMA