PC vs PMMA Lighting Profiles: How to Choose

The short answer

Choose PC when the profile must survive impact, heat, or a flame-retardant specification. Choose PMMA when the priority is maximum light transmission, long-term UV stability and a hard, scratch-resistant surface. Many luminaires use both – a PC body with a PMMA optical window, or a co-extruded section combining the two.

Side-by-side properties

Optical performance

Transmission and colour

PMMA transmits slightly more visible light and, critically, holds that transmission for years outdoors. Unstabilised PC yellows under UV, which shifts the apparent colour temperature of the luminaire – visible in architectural facades and signage where fixtures are compared side by side after a few seasons. UV-stabilised PC grades close most of that gap and are standard for outdoor-rated work.

Diffusion quality

Both materials can be compounded to a wide range of haze levels. The engineering question is rarely “which material diffuses better” but “which haze and transmission combination hides my LED pitch at my wall thickness and standoff distance”. That is a sample-and-measure exercise, not a datasheet lookup. See how to choose a material for LED diffusers.

Mechanical and thermal behaviour

PC is the structural material. Its notched impact strength is roughly an order of magnitude above PMMA, which is why it is specified for industrial fixtures, low-bay luminaires, transport applications and anything that must pass an IK impact rating. It also holds shape at temperatures where PMMA would soften – relevant near high-power LED boards and in enclosed housings.

PMMA is stiffer and harder. It resists scratching better in cleaning and handling, and it takes a crisper edge when cut or machined. It is the default for architectural profiles, decorative reveals and office luminaires where the surface is seen and touched.

Fire and compliance

This is often the deciding factor. If the luminaire has to carry a flame rating for a commercial or public-space specification, PC reaches UL94 V-2 and V-0 far more readily than PMMA, and at lower additive loading. Flame-retardant packages also affect clarity and cost, so the rating should be specified on the drawing rather than assumed. Both materials are available in UL-recognised grades.

Processing differences that show up in the profile

• Drying: PC is far more moisture-sensitive. Inadequate drying produces brittleness and silver streaks – the most common cause of field failures attributed to “bad material”.
• Melt temperature: PC runs hotter, so colour stability depends on tighter melt control; batch-to-batch shade consistency needs discipline here.
• Stress: PC retains more internal stress and is vulnerable to environmental stress cracking from adhesives, gasket plasticisers and some cleaning agents. Annealing or grade selection solves it, but only if the exposure is known in advance.
• Joining: PMMA solvents and cements are aggressive toward PC. Adhesive and solvent selection must follow the material, not the assembly habit.

Typical specification by application

Using both in one profile

Co-extrusion removes the either/or. A common construction is a rigid PC or PMMA body carrying a soft sealing lip, or an opaque white housing co-extruded with a clear or opal optical window – one part replaces an assembly. Two-material sections need compatible melt behaviour and more complex tooling, so they are planned at drawing stage. see OEM / ODM for how we handle that jointly with customers.

Full material data for each: polycarbonate and PMMA / acrylic. Or send the drawing for a recommendation – request a quote.