PPS Material Properties and Applications

Polyphenylene Sulfide (PPS) is a high-performance engineering thermoplastic, one that is know for its chemical and dimensional stability at high temperatures.

PPS also exhibits exceptional mechanical and electrical properties, making it suitable for a wide range of demanding applications. Moreover, PPS can be processed via different processes, such as extrusion, injection, and additive manufacturing (3D printing).

In this article, we discuss PPS properties, applications, and processing techniques.

What is PPS?

PPS was first synthesized in the 19th century. However, there was no industrially viable version until the latter half of the 20th century.

Polyphenylene Sulfide (PPS) is a rigid semi-crystalline polymer that can be used as a metal alternative because it offers significantly better corrosion resistance and strength-to-weight ratio. The material’s semi-crystalline nature provides it with excellent properties, comparable to those of PEEK, at a lower price point.

The high-performance plastic is especially important in the chemical and oil & gas industries, but also finds a lot of use in aerospace, electrical, and automotive applications.

PPS Material Structure

PPS has a stable aromatic-sulfide structure that endows it with significant rigidity. PPS has a backbone that comprises para-phenylene units with sulfide linkages, with -[C₆H₄-S]_n– repeating units. The sulfur atoms are bonded to the benzene rings via single covalent bonds.

The crystalline regions in PPS contribute to its high thermal and chemical stability. The aromatic rings provide it with high rigidity and structural integrity under high-temperature and corrosive conditions. Finally, the sulfide linkages enhance its resistance to most chemicals.

There are two forms of PPS – linear and cross-linked.

Linear PPS consists of uninterrupted polymer chains with minimal crosslinking. Those long, largely unbranched chains easily slide past one another in a melted state. This gives linear grades better ductility as well as easier processability. This chain mobility also lets the polymer absorb strain without cracking, so linear PPS also exhibits better fatigue resistance under cyclic loading.

Cross-linked PPS instead introduces biphenyl linkages or sulfone bridges between the molecular chains. The positive is improved thermal and chemical durability. On the downside, the pinned-down chains decrease toughness and make the material harder to process. That trade-off is the reason why most available PPS grades are linear.

PPS Material Properties

The properties of PPS depend on its form and type. As just discussed, linear and cross-linked grades have different properties.

Most of the values reported here are based on unfilled linear PPS filaments suitable for 3D printing. The values corresponding to other grades and types, especially filled grades, can significantly differ.

PPS Physical and Mechanical Properties

Property	Typical value/Rating
Density (g/cm³)	1.28–1.38
Tensile Strength (MPa)	50–85
Flexural Strength (MPa)	135–155
Impact Strength, Notched Izod (kJ/m²)	2–8
Impact Strength, Unnotched Izod (kJ/m²)	15–18
Young’s Modulus (GPa)	2.60–4.20
Flexural Modulus (GPa)	2.3–3.9
Hardness	M95/R125
Elongation at Break	1.3%–8%
Creep Resistance	High
Fatigue Strength (MPa)	37 @107 cycles (40% GF-filled)
Coefficient of Friction (COF)	0.24–0.35

PPS offers excellent mechanical properties. It has a relatively low density with high strength, giving it a high strength-to-weight ratio. Below are the highlights of PPS mechanical properties.

Strength and toughness

PPS offers high tensile and flexure strength (up to 85 and 155 MPa, respectively) at high temperatures, with minimal degradation.

However, it also exhibits intrinsic brittleness, necessitating special considerations during the design process, such as avoiding sharp corners and uneven thickness, to reduce stress concentrations and cracking.

Stiffness

PPS demonstrates high stiffness due to its high Young’s modulus (2.60–4.20 GPa) and flexural modulus (2.3–3.9 GPa). In the case of bulk resin, the flexural modulus is typically higher than Young’s modulus. Based on the available data in the filament market, this pattern is reversed for PPS filaments.

Moreover, stiffness can be substantially enhanced with reinforcement. For example, glass fiber can increase flexure modulus up to 14 GPa.

Hardness and deformation

Unfilled PPS exhibits moderate hardness with a decent resistance to deformation. This is also true for resistance to deformation under sustained load, with PPS showing high creep resistance at high temperatures (up to 220 °C).

Cyclic loading performance

PPS exhibits good fatigue resistance (up to 37 MPa after 10⁷ cycles for 40% GF-filled grades), showing stability under cyclic mechanical stress. However, it can form microcracks with high-impact or bending loads.

Wear resistance

PPS has decent wear resistance (COF = 0.24–0.35). However, it shows relatively poor performance under dry sliding without added lubrication. This can be enhanced by incorporating materials such as graphite, which endows PPS with self-lubricating properties.

PPS Thermal Properties

Property	Typical value
Glass Transition Temperature (Tg)	85 °C
Melting temperature (Tm)	283 °C–285 °C
Heat Deflection Temperature (HDT)	129 °C–180 °C (@0.45 MPa), ~112 °C (@1.8 MPa, unfilled)
Maximum Operating Temperature	220 °C (unfilled); up to 240 °C for filled grades
Thermal Conductivity (W/m∙K)	0.18–0.2
Coefficient of Linear Thermal Expansion (CLTE, µm/[m*°C])	50

PPS exhibits thermal stability under continuous operation up to 220 °C. This high-temperature resistance also allows high-temperature processing of the polymer.

Unlike the amorphous high-performance thermoplastics, PPS does not get its heat resistance from a high glass transition temperature. Its Tg is only 85 °C, and above that point the amorphous fraction of the polymer softens. What carries load up to the 283–285 °C melting point is the crystalline phase, which accounts for roughly 50–65% of an unfilled grade.

This is also why the HDT of PPS is so load-dependent. At 0.45 MPa, unfilled PPS holds 129–180 °C, but at 1.8 MPa it falls to around 112 °C because the softened amorphous regions can no longer resist the higher bending stress. Glass-fiber reinforcement removes that weakness almost entirely, with GF40 grades hold an HDT above 260 °C, which is why load-bearing PPS parts are nearly always filled.

PPS Chemical Properties

Property	Value/Rating
Solubility in Different Solvents	High resistance to almost all acids (except concentrated nitric and sulfuric acids), bases, and known solvents below 200 °C
Oxidation Resistance	High resistance at elevated temperatures
Flammability UL94	V0 (self-extinguishing)
Limiting Oxygen Index (LOI)	44%
Moisture absorption	0.01% (24 h) 0.03% (saturation)

Chemical resistance

PPS’s most remarkable trait is its chemical resistance. Due to its sulfur–aromatic bond structure, PPS is one of the most chemically inert thermoplastics to date. It is stable to almost all solvents, fuels, acids, and bases up to 200 °C. The only exception to this is highly concentrated sulfuric and nitric acids, which can degrade PPS.

PPS also shows exceptional oxidation resistance at high temperatures. The oxidation resistance of some grades extends to temperatures significantly higher than its maximum operating temperature.

These exceptional properties make it ideal for pumps, seals, and other parts that are subjected to chemicals.

Hydrolysis resistance

In addition, its very low moisture adsorption allows it to be used in applications under humid conditions and steam. This property, along with its chemical and thermal resistance, enables its use in non-implantable biomedical applications, such as medical tools, as well as oil and gas and chemical applications.

Flammability

PPS is inherently flame-retardant as it passes the UL94V-0 standard, without adding any flame retardant. In fact, it has a very high LOI of 44%, surpassing several high-performance thermoplastics. This, combined with its low cost compared to other high-performance engineering thermoplastics, makes it ideal for applications exposed to fire hazards such as aerospace and automotive.

PPS Electrical Properties

Property	Typical value
Dielectric Constant	3–4.6
Dielectric Strength (kV/mm)	17–18

PPS exhibits excellent electrical insulation performance even under high-temperature and humid conditions. This can be attributed to its high dielectric strength (17–18 kV/mm) and low dielectric constant (3–4.6). These excellent properties allow its use in electrical connectors, housing, and other parts requiring high electrical insulation.

Other Qualities

PPS’s useful traits do not stop with the ones that fall neatly under mechanical, thermal, chemical or electrical properties. Radiation resistance and dimensional stability are what push the material into nuclear handling, semiconductor equipment and precision-critical assemblies.

Radiation resistance

PPS exhibits excellent radiation resistance, including high-energy radiation, e.g., gamma- and X-rays. This makes it suitable for parts used in nuclear energy production plants and nuclear waste processing facilities. It can also be used to produce parts used in X-rays machines.

Dimensional stability

Owing to its exceptional thermal, oxidation, and chemical resistance as well as its negligible water adsorption, PPS shows exceptional dimensional stability in different harsh environments.

PPS Material Applications

PPS has numerous applications in several fields due to its excellent properties and lower price point compared to other engineering thermoplastics.

Automotive

PPS is used as a metal alternative in under-the-hood and electrical parts. It maintains dimensional stability, electrical insulation, and resistance to corrosion under the combined effects of heat, fuel, oils, and constant vibrations.

Examples of PPS applications in the automotive field include sensor housing, connectors, thermostat covers, pump impellers, brakes, cooling systems, and brackets.

Aerospace

Owing to the high-strength-to-weight ratio, stiffness, and flame retardancy of PPS, it is used for insulation parts and structural components in aerospace applications.

Chemical and Oil & Gas Industries

The excellent chemical resistance of PPS to most chemicals, including acids, bases, solvents, and fuels, makes it an ideal material in chemical and fluid transport systems. Examples include parts such as chemical pump housings and impellers, valves, and seals as well as oil patch drop balls and rod guides in the oil & gas industry.

Industrial

PPS’s excellent mechanical properties under harsh environmental conditions allow its use in industrial and mechanical engineering applications in pump components and valves. In the heating, ventilation and air conditioning (HVAC) equipment sector, PPS is used in compressors, hot-water circulation systems, power vent components, etc.

PPS is also used in household items, such as fry pan handles, toaster and dryer switches, and hair dryer grills.

Electrical

Owing to its excellent insulation properties and stable electrical and mechanical performance under humid and harsh conditions, PPS is widely used in electrical and electronic systems, replacing some metals and low-temperature polymers. Examples of PPS parts in electrical systems include connectors and terminal blocks, sensor and transformer housings, and coil bobbins.

Biomedical

PPS, especially glass-reinforced grades, is used in medical instruments and device components because of its low water absorption and high heat resistance, making it suitable for repeated steam sterilization.

PPS Composites

Property	Unfilled	Glass Reinforced (PPS-GF40)	Glass-Mineral (PPS-GF MD 65)
Filler Content (%)	0	40	65
Tensile Strength (MPa)	50–85	190	110–130
Elongation at Break (%)	1.3%–8%	1.9	1.0–1.3
Flexural Strength (MPa)	135–155	290	180–220
HDT (°C)	129–180	270	270

Fillers

There are different types of fillers for PPS, including glass fiber (GF), carbon fiber, polytetrafluoroethylene (PTFE), minerals, and glass fiber and minerals (glass-mineral).

The two market-dominant grades are PPS-GF40 and PPS-GF MD 65, which are GF- and glass-mineral-filled PPS, respectively.

The above table shows a brief comparison between the unfilled grade and these two grades. It illustrates the leap in the mechanical and thermal properties after filler addition. Below is a summary of the advantages of these glass fiber and mineral fillers.

The glass fiber (GF) filler content typically ranges from 30% to 40%. GF-filled PPS is often used in structural components.

GF-filled PPS advantages:

• More than double the strength of unfilled PPS
• A metal-like rigidity due to the significantly enhanced flexural modulus
• Enhanced dimensional stability due to the reduced shrinkage
• Enhanced HDT

Mineral fillers typically include talc, silica, or calcium carbonate.

MF advantages:

• Reduced thermal expansion
• Reduced shrinkage, improving dimensional accuracy
• Enhanced surface finish

Nanocomposites

PPS nanocomposites are also available for more sophisticated applications. Nanofillers include inorganic nanoparticles and carbon nanotubes (CNTs). What sets them apart from glass and mineral fillers is loading. Nanofillers change the material’s behaviour at a few percent or less, where conventional fillers need 30–40%.

Comparison to Other High-Performance Polymers

Property	Polyphenylene Sulfide (PPS)	Polyphenylsulfone (PPSU)	PEEK	PEI (ULTEM)	PEKK
Continuous operating temperature	220 °C	180 °C	260 °C	170 °C	260 °C
Thermal stability	Slightly lower than PEEK	Lower than PEEK	Highest	Moderate	High
Mechanical properties at high temperatures	High, but more brittle than PEEK	Lower strength and stiffness than PEEK, but higher elongation at break and toughness	Most consistent performance	Good up to 170 °C	High
Chemical resistance	Best	Moderate	Excellent	Moderate	Excellent

PPS is the most chemically resistant polymer among the thermoplastics compared above. Thus, if chemical resistance is critical along with decent mechanical properties, PPS should be chosen, especially given its lower price. PEEK has higher mechanical properties, including strength and fatigue resistance. Thus, PEEK should be chosen if superior mechanical properties are required.

The price gap between PPS and PEEK filaments can be up to 3x. For a part that does not need PEEK’s extra 40 °C of thermal headroom, that is the single strongest argument for PPS.

Similar to PEEK, PPS’s properties are comparable to those of PEKK, but at a lower price point.

PPSU is the closer call. It sits in a similar price bracket to PPS but trades chemical and thermal performance for toughness, and it survives repeated steam sterilization and accidental drops that would crack an unfilled PPS part.

In short, PPS is the go-to choice when chemical inertness at high temperatures is critical.

PPS 3D Printing

PPS 3D printing is typically used when complex geometries are required. 3D-printed PPS can exhibit lower crystallinity and mechanical properties than molded PPS. However, it can be enhanced through annealing or using reinforced PPS.

There are two processes currently used for 3D printing PPS: fused filament fabrication (FFF) and selective laser sintering (SLS).

FFF uses filaments, while SLS uses powder. One notable difference between the parts produced by the two processes is the isotropic properties of SLS-manufactured parts, while those manufactured by FFF exhibit lower strength in the Z direction.

However, FFF is still more widely available and cost-effective than SLS.

In practice, unfilled PPS filament prints at a nozzle temperature of 300–320 °C, with some formulations calling for 330–370 °C, onto a bed held at 90–120 °C and at print speeds of 25–45 mm/s. A full metal hot end is required, since these temperatures are hot enough to melt PTFE liners. PPS is far less hygroscopic than nylon or PEI, so drying is not always mandatory, though some manufacturers still do recommend it.

Cooling rate is the parameter that matters most. Crystallization makes PPS contract as it cools, and uneven cooling produces warping, residual stress and, in bad cases, cracking or delamination. This is also the reason why industrial high-temp printers are necessary.

The Chemical-Resistance Champion

In summary, PPS is a semi-crystalline engineering thermoplastic with remarkable chemical resistance as well as high thermal and mechanical properties. It is either linear or crosslinked, but current commercial grades are mostly linear. PPS offers comparable performance to PEEK at a lower price point, making it an ideal choice for demanding applications, especially those involving harsh chemicals.