Benefits of Polished & Finished Plastic
Plastic has significant advantages over other materials, such as glass and quartz.
Compared to glass, plastic can weigh 3x less and perform just as well — if not better than — glass or quartz.
Durable & Heat Resistant
Many polish-capable and high-performance plastics can withstand greater impacts and higher temps than glass.
Most high-performance plastics can shine like glass at often times a much lower price point than other materials.
While no single plastic polishing technique fits every application, we pride ourselves on choosing the best polishing solution for your product. We wrote an entire guide on the subject!
We know that polishing, especially on amorphous plastics, increases surface stress on plastic products. Surface stress management is critically important. With that in mind, we ensure that our polishing processes mitigate that stress, providing high-quality plastic components that meet customer requirements. We typically recommend and use these plastic polishing methods depending on the material:
As a traditional polishing method. buffing works on all types of plastics to smooth plastic products' surfaces. This method uses a cotton cloth to abrade the surface with thousands of multi-directional scratches that clear the first layer. Eventually, the product has a brilliant sheen. We recommend this approach for large flat pieces with limited holes and projections.
Flame polishing utilizes a specialized torch to melt and smooth plastic surfaces, resulting in a visually clear surface for some plastics. Usually used for finishing edges and surfaces, operators use this method to polish a wide variety of products, including medical devices. Despite with versatility, this method requires immense skill to perform perfectly as some surface waviness can happen. Most manufacturers limit internal polishing to larger features at or near the surface for this method to ensure product integrity.
This method uses vaporized solvents or chemicals with specialized equipment to smooth and create glossy surfaces. The operator exposes the plastic's surface to those agents that then work to soften its surface and create flow for irregularities to dissipate. We typically reserve this plastic polish method for clear thermoplastics only, such as polycarbonate, ULTEM®, polysulfone, and acrylic. Unlike other polishing methods, it can polish internal features, such as threads and bores as the operator can more tightly control the materials used. We do not recommend this method for semi-crystalline materials.
Optical machining encompasses 3 different polishing techniques that give optical-grade clarity to transparent/translucent materials: mechanical, chemical, and ultrasonic. Often these require special tooling and equipment for true optical results. As optical has strict QA standards, manufacturers measure finishes for form and roughness before shipping to ensure quality. This method produces the finest finish on most plastics (100 angstroms roughness is typical).
Best Plastic Materials for Polishing
The plastic polishing process transforms common materials into extremely optically clear products optimized for any project relying on transparency. When selecting materials for a project that will require polishing, use the list below to narrow your options. We recommend any of these materials for projects requiring polishing.
Polished Acrylic components are the most common clear parts. In addition to being relatively scratch-resistant compared to other amorphous plastics, Acrylic is also one of the least expensive materials for clear parts with the finish tint-free. As a result, it is the closest plastic substitute for window glass and can be utilized in light pipe applications. Acrylic can be polished via buffing, flame polishing, and optical machining.
Polycarbonate is available in colors and a window grade (no tint) resin. Car headlights covers, in particular, benefit from polycarbonate’s combination of clarity, high impact resistance, and low cost. It's important to note that polycarbonate is not UV resistant and requires an addition of a UV stabilizer to avoid yellowing. Any polished polycarbonate medical components that require FDA or USP Class VI certification use a non-UV stabilized material. Although polycarbonate costs more than acrylic, it costs considerably less than higher performance materials like ULTEM, making it an excellent choice for many projects.
Dark amber in color, designers know ULTEM for its excellent tensile strength, high temperature tolerance, and high resistivity to chemicals and water. Components are polished via vapor polishing or optical machining. Optical machining will provide finishes below one micro-inch for optical applications, while vapor polishing will produce a surface finish of fewer than twelve micro-inches. Our team can reduce ULTEM’s light transmittance based on thickness. As a result, polishing of thicker blocks (>2’’) takes on a black-like appearance to meet this need, if it arises.
Both vapor polishing and optical machining are effective approaches to increase clarity. Clear polysulfone components can be used in FDA-compliant devices and are commonly used in sterilization trays as their clarity allows for easy inspection. In addition, polysulfone is resistant to water absorption and can tolerate steam sterilization to 285°F.
Like Ultem and PPSU, polished PES is dark amber in its natural color. Vapor polishing and optical machining can achieve excellent results with an extremely smooth surface finish. Along with the material’s good dielectric constant, low loss factor, and high resistivity at temperatures above 200°C (392°F), PES makes an excellent high-temperature electrical insulating material.
Like ULTEM, polished Radel (PPSU) is dark amber in its natural color, and standard stock colors for polishing come in white and black. Radel allows for seemingly unlimited steam sterilization, and as a result, polished Radel components are frequently used in medical devices. Radel responds well to vapor polishing and optical machining, and polished Radel components offer better impact and chemical resistance than ULTEM and polysulfone parts.
About Polishing Costs
A common working location of a fluidic subassembly is within an instrument and outside the view of normal operation. Customers wanting to save money will consider removing the polishing step. Things to consider:
- Polishing allows for visual confirmation of fluid flow
- Has a high degree of aesthetic value
- Polishing can be done in a cost-efficient manner
- For manifolds, request polish only on the large flat areas to save money
- Leave manifold edges as machined
- Specify as machined only for highly cost competitive manifolds
- Grade 2 (vapor) is the most cost effective polishing
- Flame polishing is not a precise process. Expect corners to be rolled.
- Apply grade 3 polishing sparingly
- Angular or curved surfaces are harder to polish than flat