PPS-CF Carbon-fiber-reinforced polyphenylene sulfide (QIDI PPS-CF)

PPS (polyphenylene sulfide) is a high-performance engineering plastic used in molded automotive, electrical and chemical-processing parts, where heat and aggressive fluids rule out ordinary plastics. PPS-CF adds chopped carbon fiber for stiffness and dimensional stability. It is at the top of the range we print for heat and chemical resistance, and it is the material we reach for when nothing else on the list will survive the environment.

QIDI's product page makes some strong claims for it: continuous operation above 200 °C, being virtually insoluble in any solvent below 200 °C, outstanding resistance to acids, alkalis and salts under normal conditions, and a UL 94 V-0 flame rating. UL 94 V-0 is a flammability classification meaning a vertical test bar stops burning quickly after the flame is removed, without flaming drips. QIDI doesn't state the thickness tested for PPS-CF, and flame ratings depend on thickness, so a printed part should not be assumed to carry that rating without testing.

The catch is brittleness. On QIDI's comparison table, PPS-CF has a between-layer (Z) tensile strength of only 15.63 MPa, one of the lowest of any material we print, and the filament itself is so stiff that it can snap in the printer's feed path. PPS-CF is a specialist material: excellent where heat, chemicals or flame matter most, poor where a part has to take knocks or bend.

QIDI also sells a glass-fiber sibling, PPS-GF20. Its product page lists a slightly lower HDT of 236.3 °C (load not stated), tensile strength of 64.1 MPa, density of 1.36 g/cm³, and a UL 94 V-0 rating at 1.5 mm. On QIDI's comparison table, its between-layer tensile strength is 22.9 MPa, noticeably better than PPS-CF's. If your part needs PPS chemistry but takes more load across the layers, PPS-GF20 is worth discussing.

PPS-CF is extremely stiff. QIDI lists a bending modulus of 7160 MPa and an XY bending strength of 142 MPa on the product page. Its comparison guide lists a lower XY bending strength of 105.0 MPa, likely from a different test setup; we quote both. Tensile strength on the product page is 55–65 MPa, direction not stated.

Its weakness is between layers. All FDM parts are anisotropic: strong along the printed layers (XY), weaker across them (Z). For PPS-CF, QIDI's comparison guide gives a Z tensile strength of 15.63 MPa, roughly a quarter of its in-layer tensile strength. The product page lists a Z bending strength of 36 MPa against 142 MPa in XY. We orient every PPS-CF part so loads run along the layers and will warn you if a design can't avoid loading across them.

In practice, PPS-CF behaves as a brittle material. QIDI lists an impact strength of 27.8 kJ/m² without stating the test method, and an elongation at break of 4–8 %, but those are in-layer test bars. Real parts usually fail across the layers, at sharp corners or around fasteners. Thick sections, generous fillets, inserts and careful orientation are essential.

QIDI publishes two different heat deflection temperatures (HDT, the point where a standard bar bends a set amount under load) for PPS-CF, both at 0.45 MPa. The specification table and comparison guide give 242.7 °C; the headline text on the product page says up to 264 °C. We quote the table value as our baseline and treat the 264 °C as an upper-end figure, perhaps from annealed samples, which QIDI doesn't state. QIDI also lists a Vicat softening temperature of 268 °C and melting at 284 °C.

QIDI claims continuous operation above 200 °C. That's a vendor claim, and real limits depend on load, time and part geometry. For any part that will run continuously hot under load, tell us the temperature and load, and we'll advise whether a test part should be validated first.

QIDI's comparison guide gives an annealing recipe of 130 °C for 10 h. Annealing can improve heat performance, but it can also cause small dimensional changes and warping of large or thin parts; QIDI warns about warping for the PPS-GF20 recipe. We only anneal by agreement, after testing on your geometry.

QIDI doesn't publish UV-resistance data for PPS-CF. PPS is generally regarded as fairly weather-stable, and carbon black helps protect the surface, but long-term sun can dull the finish.

PPS-CF's very low water absorption means outdoor humidity, rain and freeze-thaw cycles won't change its dimensions or stiffness noticeably. Its brittleness is the bigger risk outdoors, where cold weather and knocks combine.

Chemical resistance is one of PPS-CF's strongest points. QIDI states that it is virtually insoluble in any solvent below 200 °C and shows outstanding resistance to acids, alkalis and salts under normal conditions. For PPS-GF20, QIDI adds resistance to oils and solvents, but flags strong oxidizing acids, such as nitric acid and hot concentrated sulfuric acid, as limited or not recommended. It's reasonable to assume similar limits for PPS-CF.

In practical terms, PPS-CF generally handles fuels, oils, brake fluid, coolants, acetone, alcohols and most cleaning chemicals far better than any other material we print. Strong oxidizers are the main exception. Printed parts also have layer lines that fluids can wick into, so test a sample in the real fluid and at the real temperature before committing to a batch.

PPS-CF barely absorbs water: QIDI lists 0.05 %. Finished parts keep their stiffness and dimensions in humid or wet environments, which makes PPS-CF a good choice for precision parts exposed to water or steam.

The filament still needs drying before printing to remove surface moisture. QIDI gives 100–140 °C for 8–12 h, warns not to exceed 160 °C to avoid damaging the spool, and recommends storage below 20 % RH. Its comparison guide gives 100 °C for 10 h. We follow these, so this is our concern rather than yours.

PPS-CF prints with a uniform matte black or dark grey finish. It looks technical and molded, and most customers use it as printed.

With the 0.6 mm or larger nozzle QIDI recommends, layer lines are slightly coarser and edges softer than with finer nozzles. We choose the nozzle per part: larger for reliability and strength, smaller where detail matters and the geometry allows.

Support contact areas show as rougher patches, and PPS-CF supports can be hard to remove cleanly from such a stiff material. Tell us which faces are cosmetic so we keep supports off them.

Annealing is the main post-process, done only by agreement after testing on your geometry, because it can change dimensions slightly and warp thin or large parts.

Light sanding removes support marks but exposes fibers and leaves a fuzzy, lighter surface. PPS is chemically resistant, which also makes it hard to paint or glue; surface preparation and specialist primers or adhesives are needed. Vapor smoothing isn't something we offer for PPS-CF.

Heat-set inserts are possible but need higher temperatures than in common plastics; we'll advise whether inserts or through-bolts with washers suit your part better. Drilling and reaming are possible, with care, because the material chips easily at edges.

PPS-CF is very dimensionally stable once printed: it barely absorbs water, and the fiber limits shrinkage. QIDI also describes PPS-CF as low-shrinkage on its wiki. Large flat parts are still harder to print than in lower-temperature materials, so we'll flag geometry that concerns us.

Holes print slightly undersized and outer dimensions slightly oversized, as with all FDM. For precise fits we compensate in the model or ream holes carefully after printing.

QIDI's wiki notes that on the standard feed path the stiff filament must bend sharply, especially for prints at the right side of the plate, and can break; it advises avoiding models covering the rightmost area. Very large PPS-CF parts may therefore need to be split, fed from the QIDI Box with dry-while-print, or fed from the top with the chamber heater off.