Polymethyl Methacrylate (PMMA)

Acrylic has the highest light transmission of any thermoplastic at roughly 92%, higher than glass, along with superior surface hardness, gloss retention, and UV stability.

It is also the most expensive resin we run and the most notch-sensitive. Acrylic parts fail at stress concentrations, so the design rules are stricter than for the other clear resins.

• Light transmission: Roughly 92%, higher than glass and higher than anything else in the catalog.
• Surface hardness and gloss: Resists scratching in transit and retains gloss over shelf life.
• UV stability: Excellent. It will not yellow in a lit retail display.
• Impact: Brittle and notch-sensitive. A sharp internal corner becomes a crack initiation site.
• Chemical resistance: Poor against alcohols and many solvents.

Luxury cosmetic jars, particularly heavy-wall and double-wall constructions where the optical depth is the design feature. Premium closures and overcaps.

Process: Injection molding.

Shrinkage: 0.2-0.6%.

Drying is critical. Moisture produces silver streaking that ruins a high-gloss cosmetic part. There is no rework path, so streaked parts are scrap.

Process for optics: Slow injection profile and high mold temperature, 60-80°C, to develop the surface finish. Fast fill produces flow lines that cannot be polished out.

Radius internal corners. Minimum internal radius 0.5mm. Notch sensitivity means sharp corners crack, and they crack in the field rather than on the press.

Alcohol: Toners, sanitizers, and alcohol-based formulas will craze acrylic. Specify a liner, an inner vessel, or a different resin.