Deflashing PPS Molded Parts

Introduction

PPS, also known as Polyphenylene Sulfide, is a high-performance thermoplastic polymer known for its excellent thermal and chemical resistance properties. It is a type of engineering plastic that belongs to the family of sulfide polymers.

PPS plastic has several notable characteristics that make it suitable for various applications:

1. Thermal Resistance: PPS can withstand high temperatures without significant degradation. It has a high melting point, typically around 280-300°C (536-572°F), and maintains its strength and stiffness even at elevated temperatures.
2. Chemical Resistance: It exhibits exceptional resistance to a wide range of chemicals, including acids, bases, fuels, and solvents. It is highly resistant to degradation and remains stable when exposed to corrosive environments.
3. Electrical Insulation: The material has excellent electrical insulating properties, making it suitable for applications in the electrical and electronics industries. It has low dielectric constant and dissipation factor, which means it does not easily conduct electricity.
4. Dimensional Stability: This material has low thermal expansion and contraction rates, resulting in excellent dimensional stability. This characteristic makes it suitable for applications where tight tolerances and precise dimensions are required.
5. Mechanical Strength: PPS offers good mechanical strength and rigidity. It has high tensile strength, impact resistance, and flexural modulus, making it capable of withstanding mechanical stress and load-bearing applications.
6. Flame Resistance: It is inherently flame retardant and exhibits self-extinguishing properties. It does not readily support combustion, making it suitable for applications that require fire resistance.

Due to its excellent properties, PPS plastic finds application in various industries, including automotive, electrical and electronics, aerospace, chemical processing, and more. It is used for components such as electrical connectors, pump parts, valves, gears, insulation components, and other high-performance applications that require resistance to heat, chemicals, and mechanical stress.

Molding PPS

PPS (Polyphenylene Sulfide) can be injection molded using standard injection molding techniques. The process typically involves the following steps:

1. Material Preparation: PPS is available in pellet form. The pellets are typically dried before processing to remove any moisture that could affect the quality of the molded parts. The drying temperature and duration depend on the specific grade of PPS being used and are usually provided by the material manufacturer.
2. Mold Design and Preparation: A mold is designed based on the desired shape and dimensions of the final product. The mold is typically made from steel and consists of two halves, the cavity and the core, which come together to form the desired shape. The mold is prepared by cleaning and applying a mold release agent to ensure easy part removal.
3. Injection Molding Machine Setup: The injection molding machine is set up according to the specific requirements of the PPS material being used. This includes setting the barrel temperature, nozzle temperature, injection pressure, injection speed, and cooling parameters. The exact settings may vary depending on the grade of PPS and the manufacturer’s recommendations.
4. Pellet Feeding: The dried PPS pellets are loaded into the hopper of the injection molding machine. The pellets are gravity-fed from the hopper into the heated barrel of the machine.
5. Melting and Injection: The PPS pellets are conveyed by a screw mechanism within the barrel, where they are heated to their melting point. Once molten, the screw injects the melt into the mold cavity under high pressure. The mold is typically held closed by the clamping unit of the injection molding machine.
6. Cooling and Solidification: After the molten PPS is injected into the mold, it begins to cool and solidify. The mold is designed with cooling channels to facilitate the rapid cooling of the plastic. The cooling time is determined by the wall thickness and geometry of the part.
7. Part Ejection: Once the PPS has solidified and cooled sufficiently, the mold opens, and the molded part is ejected using ejector pins or other mechanisms. The part may undergo additional post-processing steps such as trimming, deburring, or surface finishing, if necessary.
8. Cycle Repeat: The process is then repeated for the next cycle, with the mold closing, new PPS pellets being fed, and the cycle starting again.

It’s important to note that the specific injection molding parameters and process conditions may vary based on the grade of PPS being used, the complexity of the part, and the specific requirements of the application. It is recommended to consult the material manufacturer’s guidelines and work with experienced injection molding professionals for optimal results.

Deflashing PPS

PPS (Polyphenylene Sulfide) parts can be cryogenically deflashed. Cryogenic deflashing is a process used to remove excess flash or burrs from molded plastic parts by subjecting them to extreme cold temperatures.

The cryogenic deflashing process typically involves the following steps:

1. Preparing the Parts: The PPS parts are first inspected to identify any excess flash or burrs that need to be removed. They are then placed in a fixture or container that can withstand the extreme temperatures of the cryogenic process.
2. Loading into a Cryogenic Deflashing Machine: The parts, along with any media or abrasive agents, are loaded into a cryogenic deflashing machine. This machine is specifically designed to handle the low temperatures and remove the excess flash from the parts.
3. Cryogenic Cooling: The machine is sealed, and liquid nitrogen is introduced into the machine, rapidly cooling the parts and the media to very low temperatures, typically below -50°F.
4. Tumbling and Deflashing: Once the parts and media are cooled, the machine is activated, causing the parts to tumble or rotate inside the chamber. As the parts move, the brittle excess flash or burrs become more fragile and brittle due to the low temperature. The media, along with the cold temperature, helps break away and remove the excess material.
5. Separation and Inspection: After the tumbling process, the parts and media are separated. The parts are inspected to ensure that the excess flash has been adequately removed. If necessary, the process can be repeated for further deflashing.
6. Post-Processing and Finishing: Once the cryogenic deflashing process is complete, the parts may undergo additional post-processing steps, such as washing, drying, and any required finishing operations, to achieve the desired surface quality.

Cryogenic deflashing is an effective method for removing excess flash or burrs from PPS parts without causing damage to the part itself. It is a relatively fast and efficient process that can be automated for large-scale production. However, the specific parameters and conditions for cryogenic deflashing may vary based on the size, geometry, and material composition of the PPS parts, so it is important to work with experienced cryogenic deflashing service providers or consult the manufacturer’s guidelines for optimal results.

Want to send in your PPS parts for a no-cost deflashing evaluation? Learn more by calling us at (508) 459-7447×105 or email us at info@nitrofreeze.com.