PLASTIC POLISHING & OTHER FINISHES

BENEFITS OF POLISHED & FINISHED PLASTIC

Plastic has significant advantages over other materials, such as glass and quartz.

Manufacturing plastic parts from clear material is common for manifolds and machined components as it allows for easier internal process monitoring. Many amorphous materials in their raw state are clear, however, after machining they become translucent to opaque. This depends mostly on tool wear and cutting efficiency. To return the machined part to clear, operators usually need a secondary polishing operation. Designers find that specifying the proper clarity to match the application can be a challenge. Controlled Fluidics has defined The 4 Clarity Grades to aid this design effort.

GRADE 1

Standard machined plastic finish and appropriate for non-visual applications.

GRADE 2

Allows for activities like visual fluid flow and bubble detection. This is the most cost-efficient method with limited quantitative measurements for quality.

GRADE 3

This finish is appropriate for imaging through the manifold or plastic part for detection sensors. This clarity is specified in a localized area and typically not used for entire parts.

GRADE 4

This finish is a true optical finish specified in both surface finish and surface form. This level is appropriate for lenses but usually not used in manifold applications.

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.

Acrylic

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 (PC)

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.

ULTEM

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.

Polysulfone

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.

Polyethersulfone (PES)

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.

Radel

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.

Interested in other materials? See our comprehensive list of materials Controlled Fluidics works with.

QUICK NOTE ABOUT ALLOWABLE DEBRIS

Something we must mention about polished components is the potential cosmetic blemishes post production. This can cause some concerns about debris in the material and any loss of function when it comes to components, especially those made from acrylic.

According to the ASTM standard D4802-16, there is an allowable level of particulate debris in acrylic sheets. This standard states that any amount of particles under 0.8 mm (0.031 in) is acceptable provided they do not affect the service ability of the sheet. Particles between 3.2 mm (0.125 in) and 0.8 mm are allowed given no more than one particle of this size is found in 0.4 m² (4.3 ft²) of the sheet. We only purchase acrylic sheets that conform to this standard. We also hold our products to this standard, including parts in other clear materials.

While visible debris can seem inconvenient, it hardly ever has an impact on functionality including those directly above a channel. For those applications requiring debris free material, please define the requirements during the quoting process. It is possible to cull material based on contamination levels for an additional cost.