PPS (Polyphenylene Sulfide)

PPS (polyphenylene sulfide) is a semi-crystalline high-performance thermoplastic. No known solvent dissolves it below about 200 °C, it absorbs almost no water, it is inherently flame-retardant, and it holds its dimensions under heat and load. Unfilled PPS is stiff but brittle, so most parts use glass-filled or glass- and mineral-filled grades, which are strong, rigid and stable at continuous temperatures up to about 200–220 °C.

Choose PPS for parts that sit in hot fuels, oils, coolants, acids or cleaning agents: pump and valve parts, automotive under-hood components, electrical connectors and chemical-processing equipment. Where lower toughness is acceptable, it is a cost-effective alternative to PEEK. Its limits are brittleness, weak weld lines in molded parts and attack by strong oxidizing acids. On Uretyco, PPS is offered as FDM filament, as stock for CNC machining and as a molding resin; grade and lead time are confirmed during quote and order review.

Mechanical and physical properties

Processing routes

FDM printing

PPS filaments, unfilled or reinforced with carbon or glass fiber, print on high-temperature FDM machines with a heated bed and preferably a heated chamber. The polymer crystallizes as it cools, so warping and layer bonding depend on the build temperature, and many parts are annealed after printing to complete crystallization and raise heat resistance. Printed PPS keeps the chemical resistance of the polymer but is brittle and much weaker across layers. Design and ordering points:

• Orientation: keep loads, clips and bosses in the layer plane; across layers, printed PPS fails at far lower stress. State a fixed orientation in the order notes.
• Fiber-filled filaments: carbon or glass fibers add stiffness and reduce warping, but they increase brittleness and give a matte, slightly rough surface.
• Walls and corners: plan walls of at least about 1.0–1.5 mm, generous fillets at load points and no sharp notches; PPS is notch-sensitive.
• Annealing: if the part runs hot, ask for annealing. It raises stiffness above Tg but can make long and thin parts shrink or distort slightly, so machine critical features afterwards.
• Holes and threads: drill or ream fit-critical holes and use threaded inserts; printed threads suit low loads only.

CNC machining

PPS stock is supplied as unfilled, 40% glass-filled and bearing grades with carbon fiber, graphite or PTFE. Because it hardly absorbs moisture, it machines to tight tolerances and stays dimensionally stable, but filled grades are abrasive and all grades chip easily at sharp edges. Watch for:

• Tools: carbide is the minimum for glass-filled PPS, and diamond-coated or PCD tools last far longer on batches. Sharp tools reduce edge chipping.
• Edges and breakouts: chamfer edges and plan tool exits, since PPS chips at sharp edges and hole breakouts; avoid knife edges and thin, unsupported walls.
• Walls and radii: start from the CNC Design Guide's plastic values (1.5 mm minimum wall, internal radii at least one-third of the pocket depth) and add margin for glass-filled grades.
• Threads: tapped threads chip easily in filled grades; for load-bearing joints or repeated assembly, use threaded inserts.

Injection molding

Most PPS parts are injection molded from glass-filled or glass- and mineral-filled grades. The melt is very fluid: it fills thin walls and long flow paths well but also flashes into small gaps, so tools need tight shut-offs and shallow vents. Mold temperatures of about 135–150 °C are typical so that parts crystallize fully; parts from colder molds can shrink and warp later in service. Key rules, building on Uretyco's injection molding DFM guide:

• Wall thickness: the guide's general range of 1.5–3.5 mm applies; PPS fills thinner walls than most resins, but keep thickness uniform to limit warpage.
• Draft: at least 1° per side outside and 0.5° or more inside; add about 1° per 0.025 mm of texture depth.
• Fiber orientation and weld lines: shrinkage and strength differ along and across the flow, and weld lines in glass-filled PPS can be far weaker than the base material. Place gates so that weld lines stay out of load paths and snap features.
• Ribs and bosses: rib base no more than 60% of the wall and bosses about 2× the screw diameter outside, with generous root radii, because PPS is notch-sensitive.
• Tooling: glass-filled PPS is abrasive and runs in hot molds, so hardened steel tooling is the norm for production; aluminum tooling suits short runs only and is confirmed in the quote.

Tolerances and surface

Without a drawing tolerance, FDM parts on Uretyco follow the default of ±0.5 mm or ±0.5%, whichever is greater, and annealing can add shrinkage. For machined PPS, Uretyco treats unspecified tolerances as ISO 2768-mK with a default surface of about Ra 1.6–3.2 µm; low moisture uptake and low creep make PPS one of the most dimensionally stable plastics to machine. Molded parts follow DIN ISO 20457 (formerly DIN 16742) by default, with SPI finishes from A1 to D3; on glass-filled grades, a resin-rich, glossy surface needs the hot mold temperatures mentioned above. Final values are confirmed in the quote and order review.

Finishing options

PPS is usually used as molded, machined or printed. The chemical resistance that makes it valuable also makes it hard to paint, print on or bond, so finishes are chosen for function rather than appearance.

Cost and lead-time drivers

PPS resin is moderately priced for a high-performance polymer and well below PEEK and PEI, so the tool dominates cost in molding and the process dominates in machining and printing. The main levers:

• Process and volume: FDM for prototypes and fixtures, CNC for small batches of precise parts, injection molding once the design is stable and quantities justify hardened tooling.
• Grade: 40% glass-filled molding grades are widely used; unfilled, glass- and mineral-filled and bearing grades and fiber-filled filaments can take longer to source.
• Tool wear: glass and carbon fibers wear cutting tools, printer nozzles and molds faster, which shows in batch and tooling prices.
• Post-processing: annealing, post-machining of printed parts and inserts each add a step.
• Documents: material certificates and inspection reports are opt-in and can extend the lead time. Request them at quote time.

PPS vs. common alternatives

PPS is the economical step up from glass-filled nylon when parts see temperatures above about 150 °C, aggressive fluids, or humidity that makes PA66 swell and lose stiffness. Move to PEEK when toughness, wear resistance or continuous temperatures near 250 °C matter, and consider PEI when the part needs toughness and flame resistance more than chemical resistance.

When not to choose PPS

Typical applications

• Pump housings, impellers, valve bodies and fittings in fuels, coolants and chemicals.
• Automotive under-hood parts such as thermostat housings, coolant and fuel-system components and sensor housings.
• Electrical connectors, coil formers, relay and lamp components that need V-0 and heat resistance.
• Chemical-processing and laboratory equipment parts such as filter housings and manifolds.
• Printed jigs, fixtures and test parts that must survive solvents, oils or cleaning agents.
• Household appliance parts near heat sources, such as components of irons, hair dryers and cookers.

Specifying PPS on Uretyco

1. 1
   Choose the process

   FDM for prototypes and fixtures, CNC for precise small batches, injection molding for stable designs in volume; if you are unsure, the quote can compare routes.

2. 2
   Name the grade

   Unfilled, 40% glass, glass and mineral, bearing grade or fiber-filled filament: state it in the order notes so that availability is confirmed.

3. 3
   Upload the right files

   STL, 3MF or STEP for printing; STEP plus a 2D drawing for machining; for molding, a drawing with draft, parting line, gate preference and acceptable weld-line areas.

4. 4
   Describe the environment

   List fluids, concentrations, temperatures and loads; for printed parts, add orientation, annealing and cosmetic faces.

5. 5
   Request documents and review the quote

   Material certificates and inspection reports are opt-in; the final grade, tooling and lead time are confirmed in the quote and order review.

FAQ

PPS or PEEK?

If the requirement is chemical resistance and stiffness up to about 200 °C, glass-filled PPS usually does the job at a fraction of the cost of PEEK. Choose PEEK when the part must be tough, resist wear, see continuous temperatures closer to 250 °C or handle hot water and steam over long periods.

Why is PPS considered brittle?

Unfilled PPS breaks at low strain, and glass-filled grades, although very strong, stretch only about 1–2% before failure. Parts therefore fail at notches, sharp corners, weld lines and over-tightened screws rather than by bending. Generous radii, threaded inserts and gates placed to keep weld lines out of load paths prevent most problems.

Is printed PPS as chemical-resistant as molded PPS?

The polymer is the same, so resistance to fuels, oils and solvents is similar. Printed parts reach full crystallinity only with suitable build conditions or annealing, however, and their layer seams are weaker and can leave small leak paths. For sealing or pressurized parts, machined or molded PPS is the safer route.

When is glass-filled nylon enough?

For parts below about 120 °C in dry or oily environments, PA66-GF is tougher and much cheaper. PPS becomes the better choice when temperature, humidity, acids or coolants would make nylon swell, soften or degrade over time.

Related resources

• PEEKTougher, for higher temperatures and steam.
• PEI (ULTEM)Flame-resistant amorphous alternative.
• Glass-Filled NylonLower-cost choice for moderate temperatures.
• Injection Molding DFMWalls, draft, ribs, gates and tooling.
• CNC Design GuideTolerances, walls, threads and setups.
• 3D PrintingTechnologies, files and cost drivers.