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Polyphenylene Sulfide (PPS): A Comprehensive Guide on High Heat Plastic

Polyphenylene sulfide (PPS) is a high-performance engineering thermoplastic with high temperature. It has a semi-crystalline structure with a unique combination of properties. They range from dimensional and thermal stability to high temperature and chemical resistance. Due to its excellent electrical insulation, it is suitable for electrical components. Know more about this versatile material in detail.


What is polyphenylene sulfide (PPS)?

What is polyphenylene sulfide (PPS)?

Polyphenylene sulfide (PPS) is a semi-crystalline, high-temperature engineering thermoplastic. It is a rigid and opaque polymer. It has a high melting point (280°C). It consists of para-phenylene units alternating with sulfide linkages.

PPS offers an excellent balance of properties like:

  • Exceptional mechanical strength
  • Dimensional stability
  • Electrical insulation properties
  • Resistance to flame, chemical, and high temperature

It can be easily processed as its toughness increases at high temperatures. These assets make it a chosen alternative to metals & thermosets. Suitable for automotive parts, appliances, electronics, and several other applications.

How is PPS manufactured?

How is PPS manufactured?

The first commercial process for PPS was developed by Edmonds and Hill (US patent 3 354 129, Yr. 1967) while working at Philips Petroleum under the brand name Ryton. In the original process developed by Philips, the product obtained has a low molecular weight. It can be used in this form for coating applications.

To produce molding grades, PPS is cured (chain extended or crosslinked) around the melting point of the polymer in the presence of a small amount of air. This curing process results in:

  • Increase in molecular weight
  • Increased toughness
  • Loss of solubility
  • Decrease in melt flow
  • Decrease in crystallinity
  • A darkening in color (a brownish color in contrast to this linear PPS grades are off-white)

Over the period of time, modifications to the process have been reported. This is done to eliminate the curing stage & develop products with improved mechanical strength.

Today, all commercial processes use improved versions of this method. PPS is produced by the reaction of sodium sulfide and dichlorobenzene in a polar solvent such as N-methylpyrrolidone and at a higher temperature [at about 250°C (480°F)].

Synthesis of PPS
The reaction of sodium sulfide and dichlorobenzene in a polar solvent to produce Polyphenylene sulfide (PPS)

What are the main types of PPS?

What are the main types of PPS?

Regular PPS is an off-white, linear polymeric material of modest molecular weight and mechanical strength. When heated above its glass transition temperature (Tg ~85°C), it crystallizes rapidly. Main three types of PPS include:

Polymer Type
Linear PPS
  • The molecular weight of this polymer is nearly double as compared to regular PPS.
  • The increased molecular chain length results in high tenacity, elongation, and impact strength.
Cured PPS
  • Obtained from the heating of regular PPS in the presence of air (O2).
  • Curing results in molecular chain extension & formation of some molecular chain branches.
  • Increases the molecular weight and provides some thermoset-like characteristics.
Branched PPS
  • Has higher molecular weight than regular PPS.
  • The backbone of the extended molecule has extended polymer chain branched from it.
  • Branched PPS has improved mechanical properties, tenacity and ductility.

What are the properties of polyphenylene sulfide (PPS)?

What are the properties of polyphenylene sulfide (PPS)?

  1. Crystal Structure and Physical Properties: PPS is a semi-crystalline polymer.

    • The unit cell is orthorombic (a=0.867 nm, b=0.561 nm, c=1.026 nm)
    • The heat of fusion for an ideal PPS crystal was calculated as 112 J/g
    • Depending on the thermal history, molecular weight, and cross-linked status (linear or not) the degree of crystallinity ranges from 0.30 to 0.45%
    • Amorphous and crosslinked PPS can be prepared by:
      • Heating the material above the melting temperature
      • Cooling it to around 30°C below the melting temperature, and
      • Holding it for several hours in the presence of air

  2. Dimensional Stability: PPS is an ideal material of choice to produce complex parts with very tight tolerances. The polymer exhibits excellent dimensional stability even when used under high temperature and high humidity conditions.

  3. Electrical Properties: PPS has excellent electrical insulation properties. High volume resistivity and insulation resistance are retained after exposure to high-humidity environments. It has a less pronounced O2 sensitivity. It can be conveniently doped to get high conductivity.

  4. Thermal Properties and Fire Resistance: PPS is a high-temperature specialty polymer. Most of the PPS compounds pass UL94V-0 standard without adding flame retardant. PPS can be resistant at 260°C for a short time and used below 200°C for a long time.

  5. Mechanical Properties: PPS has high strength, high rigidity, and low degradation characteristics even in high-temperature conditions. It also shows excellent fatigue endurance and creep resistance. PPS has a lower elongation to break, a higher cost, and is rather brittle. Today, PPS is available in different forms and grades such as compounds, fibers, filaments, films and coatings.

  6. Chemical Properties: PPS has good chemical resistance. If cured, it is unaffected by alcohols, ketones, chlorinated aliphatic compounds, esters, liquid ammonia, etc. It also tends to be affected by dilute HCl, nitric acids, and concentrated sulfuric acid. It is insensitive to moisture and has good weatherability.

Key Properties of Polyphenylene Sulfide (PPS) Polymer

How additives optimize PPS properties?

How additives optimize PPS properties?

There is a great number of PPS compounds in the market. Due to the chemical robustness of the polymer, a great variety of fillers and reinforcing fibers and combinations of these can be applied.

PPS resin is generally reinforced with various reinforcing materials or blended with other thermoplastics in order to further improve its mechanical and thermal properties. PPS is more used when filled with glass fiber, carbon fiber, and PTFE.

Many grades are available including:

However, on the market PPS-GF40 and PPS-GF MD 65 are established as standard compounds. These two have an overwhelming market share.

As you can see, the mechanical properties of reinforced grades differ significantly from the unfilled neat polymer. The typical property values for reinforced and filled grades fall in the range shown in the table below.

Property (Unit) Test Method Unfilled Glass Reinforced Glass-Mineral Filled*
Filler Content (%)   - 40 65
Density (kg/l) ISO 1183 1.35 1.66 1.90 - 2.05
Tensile Strength (MPa) ISO 527 65-85 190 110-130
Elongation at Break (%) ISO 527 6-8 1.9 1.0-1.3
Flexural Modulus (MPa) ISO 178 3800 14000 16000-19000
Flexural Strength (MPa) ISO 178 100-130 290 180-220
Izod notched Impact Strength (kJ/m2) ISO 180/1A   11 5-6
HDT/A (1.8 MPa) (°C) ISO 75 110 270 270
Typical Mechanical Properties of PPS Compounds
Data from Product brochures: DURAFIDE®, Polyplastics; Ryton®, Solvay
* depending on filler ratio Glass / Mineral

Typically neat polymer grades are used for fibers and films. Whereas filled/reinforced grades are used in thermally and/or chemically demanding environments.

Further PPS-based nanocomposites can also be prepared using:

  • carbon nanofillers (expanded graphite (EG) or ultrasonicated EG (S-EG), CNTs) or 
  • inorganic nanoparticles.

Due to the insolubility of PPS in common organic solvents, most PPS-nanocomposites have been prepared by melt-blending approach. One of the main reasons for adding nanofillers to PPS is to improve its mechanical properties to meet the increasingly high demand for certain applications.

Further, different additives are used to alter PPS properties.

  • In order to lower the melt flow i.e., achieve high viscosity, additives such as alkali metal silicate, alkali metal sulfite, amino acids, and oligomers of a silyl ether may be added.
  • During polymerization, if calcium chloride is added, the molecular weight will increase.
  • The impact resistance can improve with the inclusion of block copolymers in the initial reaction.
  • Sulfonic acid esters along with a nucleating agent would improve the crystallization rate.
  • The addition of an alkali metal or alkali earth metal dithionate in the mixture would increase the heat stability and lower the crystallization temperature.

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What are the processing conditions for PPS?

What are the processing conditions for PPS?

PPS resins (base polymer, glass-reinforced, and mineral/glass-reinforced systems) are typically used for:

  • injection molding,
  • extrusion blow molding, and
  • extrusion applications.

They can be processed at temperatures in the range of 300 to 350°C. The processing of PPS can be hampered at times due to its high melting point.

For filled PPS grade, the upper processing temperature should be used to avoid wear and tear of the barrel, screw, and screw tip.

  1. Pre-drying: It occurs at 150-160°C for 2-3 hrs or 120°C for 5 hours. It enhances molded the appearance of products and prevents drooling. For carbon fiber-filled grades, pre-drying is particularly important. This is because the moisture absorption is high due to the carbon fibers.

  2. Injection Molding: To have higher productivity, a mold temperature of 50°C followed by post-crystallization at 200°C is possible. But it is not recommended for applications requiring high dimensional stability.

    • Because of its low viscosity, mold tightness has to be checked
    • Cylinder temperature: 300-320°C
    • Mold temperature: 120-160°C, to obtain good crystallization and minimize warping
    • Injection pressure: 40-70MPa
    • Screw Speed: 40-100 rpm

  3. Extrusion: Commonly available for fiber and monofilament production as well as tubing, rod, and slab.

    • Drying conditions: 121°C for 3 hrs
    • Mold Temperature: 300-310°C
    • Melt Temperature: 290-325°C

Is PPS recyclable?

Is PPS recyclable?

Polyphenylene sulfide (PPS) is recyclable. PPS can be recycled by:

Due to its high melting point and chemical resistance, the recycling process for PPS can be challenging. This in turn makes the processing more difficult. However, there are specialized recycling facilities that are equipped to handle PPS recycling, and efforts are being made to increase its recyclability and promote the circular economy.

Take the course by our leading expert Donald Rosato who will help you establish a successful plastics recycling system by clearly understanding the recovery & reuse model and gaining in-depth knowledge about advanced technologies (depolymerization, pyrolysis, mechanical and solvent-based recycling), materials & applications.

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Is PPS toxic?

Is PPS toxic?

Polyphenylene sulfide is generally considered to be a safe and non-toxic material. PPS can pose a risk to human health and the environment if not handled properly or used inappropriately. Hence, it is important to follow proper safety protocols and guidelines.

Note: It is important to note that the safety of any material depends on its specific use and application.

Key Applications

Key Properties



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1 Comments on "Polyphenylene Sulfide (PPS): A Comprehensive Guide on High Heat Plastic"
Teresa N May 10, 2023

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