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

Polyphenylene sulfide (PPS) is a high-performance, engineering thermoplastic characterized by an unusual combination of properties. These properties range from high temperature performance to dimensional stability and excellent electrical insulation properties.

But, what makes PPS a high performance plastic in several sectors? What it is made up of? Get detailed technical information on Polyphenylene sulfide and explore:

   »  What is PPS - Polyphenylene Sulfide?
   »  How PPS is Produced?
   »  Key Properties of PPS (Physical, thermal, electrical…)
   »  How to Optimize PPS Properties?
   »  What are the popular applications of PPS?
   »  Processing methods for PPS

(Continue reading or click to go on specific section of the page)

What is PPS - Polyphenylene Sulfide?


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

PPS offers an excellent balance of properties like:


Key Properties of Polyphenylene Sulfide (PPS) Polymer

And, it can be easily processed as well as its toughness increases at high temperatures.

These assets make Polyphenylene sulfide a chosen alternative to metals & thermosets for use in automotive parts, appliances, electronics and several others applications.

Some of the key producers of PPS include:

   »  Toray Resin Company - TORELINA®, TORAYCA®
   »  RTP Company - RTP 1300 series
   »  Solvay - Ryton®, PrimoSpire®, Tribocomp®
   »  Celanese - FORTRON®, CoolPoly®, Celstran®
   »  Polyplastics - DURAFIDE®
   »  SABIC - LNP™ LUBRICOMP™, LNP™ STAT-KON™, LNP™ THERMOCOMP™ and more
   »  Lehman & Voss - LUVOCOM®


» View >1600 Commercially Available PPS Grades & >80 Suppliers in Omnexus Plastics Database

This plastic database is available to all, free of charge. You can filter down your options by property (mechanical, electrical…), applications, conversion mode and many more dimensions.


What is PPS Made From?


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.

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

Synthesis of PPS


In the original process developed by Philips, the product obtained has a low molecular weight and 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, modification to the process have been reported to eliminate curing stage & develop products with improved mechanical strength.

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:

Linear PPS

  • The MW 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 heating of regular PPS in the presence of air (O2)
  • Curing results in molecular chain extension & formation of some molecular chain branches increases the MW and provides some thermoset-like characteristics

Branched PPS

  • Has higher MW than regular PPS
  • The backbone of the extended molecule has extended polymer chin branched from it
  • Branched PPS has improved mechanical properties, tenacity and ductility


Key Properties of Polyphenylene Sulfide (PPS)


In the above section, we discussed about the general characteristics of Polyphenylene sulfide. It is also important to mention that there are several other properties of Polyphenylene sulfide that should be considered before employing it for a specific application. Let’s discuss all the properties of PPS in detail…

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 from 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

Knowledge about the crystallization behavior of PPS is very important to understand the recommended processing parameters. The following table shows the phase transition temperatures of PPS. Ranges depend on mol. weight and curing status (linear or crosslinked).

Glass Transition Temperature (Tg) 85 - 95 °C
Crystallization on Heating (Tc-h) 120 - 140 °C
Cristallite Melting (Tm) 275 - 285 °C
Recrystallization on cooling (T c-c) 255 - 225 °C
Density 1.35 g/cm3
Gamma Radiation Resistance Good
UV Light Resistance Good
HDT @0.46 Mpa (67 psi) 140 - 160 °C
HDT @1.8 Mpa (264 psi) 100 - 135 °C
Max Continuous Service Temperature 200 - 220 °C
Thermal Insulation (Thermal Conductivity) 0.29 - 0.32 W/m.K
Phase Transition Temperatures & Other Physical Properties of PPS

Dimensional Stability


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

Coefficient of Linear Thermal Expansion 3 - 5 x 10-5 /°C
Shrinkage 0.6 - 1.4 %
Water Absorption 24 hours 0.01 - 0.07 %

Electrical Properties


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

Arc Resistance 124 sec
Dielectric Constant 3 - 3.3
Dielectric Strength 11 - 24 kV/mm
Dissipation Factor 4 - 30 x 10-4
Volume Resistivity 15 - 16 x1015 Ohm.cm

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 resistance to 260°C for short time and used below 200°C for a long time.

Fire Resistance (LOI) 43 - 47 %
Flammability UL94 V0

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.

Elongation at Break 1-4%
Elongation at Yield 1-4%
Flexibility (Flexural Modulus) 3.8-4.2 GPa
Hardness Rockwell M 70-85
Hardness Shore D 90-95
Stiffness (Flexural Modulus) 3.8-4.2 GPa
Strength at Break (Tensile) 50-80 MPa
Strength at Yield (Tensile) 50-80 MPa
Toughness (Notched Izod Impact at Room Temperature) 5 - 25 J/m
Young Modulus 3.3 - 4 GPa
Click here to compare the mechanical properties of reinforced grades vs. unfilled neat polymer

Chemical Properties


PPS has good chemical resistance. If cured, it is unaffected by alcohols, ketones, chlorinated aliphatic compounds, esters, liquid ammonia etc. however, it tends to be affected by dilute HCl and nitric acids as well as conc. sulphuric acid. It is insensitive to moisture and has good weatherability.
Click here to see chemical properties of PPS in detail

PPS has however, 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.


How to Optimize PPS Properties?



Search PPS Grades Based on
Their Reinforcement Method


Search PPS Grades Based on Their Reinforcement Method

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 the 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 as 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 and 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 for a great variety of applications in thermally and/or chemically demanding environment.

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 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 of 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, oligomers of a silyl ether may be added. 



  • During polymerization, if calcium chloride is added, the molecular weight will increase.
  • The impact resistance can be improved with the inclusion of block copolymers in initial reaction
  • Sulfonic acid esters along with a nucleating agent would improve the crystallization rate
  • With the addition of an alkali metal or alkali earth metal dithionate in the mixture, they would increase the heat stability and lower the crystallization temperature



Popular Applications of PPS


The excellent properties of PPS with its ease of production and moderate cost makes it one of the most suitable choices for various applications where cost and high performance are essential.

Automotive Applications/ Automobile Parts


Polyphenylene Sulfide Applications in Automotive Market Polyphenylene Sulfide applications in automotive market have seen strong growth mainly due to its ability to replace metal, thermosets and other types of plastic, in more demanding applications. It is an ideal choice for automotive parts exposed to:

  • High temperatures, 
  • Automotive fluids, or 
  • Mechanical stress

PPS is a lighter weight alternative to metals, resistant to corrosion by salts and all automotive fluids. The ability to mold complex parts to tight tolerances and insert molding capability accommodate multiple component integration.

Under-the-hood is the largest application area for PPS followed by electrical parts. PPS applications in automotive include fuel injection systems, coolant systams, water pump impellers, thermostat holder, electric brakes, switches, bulb housing and so on.

It is rarely used for the manufacture of interior or exterior auto parts.

» Select Suitable PPS Grade for Your Automotive Application

Electronic and Electrical Applications


Owing to its high temperature resistance, high toughness, good dimensional stability and good rigidity, PPS becomes an ideal material of choice in E&E market.

Electronics and Electrical Applications of PPS
  • Offers excellent flow and low shrinkage for precision molding of connectors and sockets
  • Provides superior stiffness and mechanical integrity for reliable assembly, and
  • Is the most stable material choice for all soldering methods

PPS compounds also have UL94 V-0 flammability ratings without the use of flame retardant additives. Special low flash grades have been developed to meet the needs of high precision molding applications.
In the electrical / electronic sector, Polyphenylene Sulfide is also used to manufacture a range of articles including bobbins and connectors, hard disk drives, electronic housings, sockets, switches and relays. The key trend influencing PPS growth in electrical / electronic applications is substitution of other lower temperature polymers.

Appliances


Thanks to its exceptional dimensional stability, low density, corrosion- and hydrolysis resistance, PPS can be used to manufacture heating and air conditioning components, fry pan handles, hair dryer grills, Steam iron valves, toaster and dryer switches, microwave oven turntables etc. in electric appliances.

Industrial Applications


PPS has been replacing metal alloys, thermosets, and many other thermoplastics in mechanical engineering applications. The thermal stability and broad chemical resistance of Polyphenylene Sulfide make it exceptionally well suited to service in very hostile chemical environments.

Industrial Applications of PPS
  • It finds uses in many heavy industrial applications, including some outside the arena of reinforced injection molding compounds
  • It is used in fiber extrusion as well as in non-stick and chemical resistant coatings
  • It is well suited to manufacture mechanically and thermally highly stressed molded parts
  • In machine construction and precision engineering, PPS is used for various components such as pumps, valves and piping
  • It can also be found in oil field equipment such as lift and centrifugal pump components, oil patch drop balls, rod guides and scrapers
  • In the heating, ventilation and air conditioning (HVAC) equipment sector, Polyphenylene Sulfide is used for compressors, mufflers/reservoirs, hot water circulation components, induced draft blower housing, motor relays and switches, power vent components and thermostat components

» Find Suitable PPS Grade for Your Engineering Application

Medical and Healthcare Applications


PPS compounds (typically glass reinforced grades) are used in medical application such as surgical instruments and device components & parts that require high dimensional stability, strength and heat resistance. PPS fibers are also used in medical fibers and membranes.


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.

Polyphenylene Sulfide 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.

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

Pre-drying


Pre-drying at 150-160°C for 2-3 hrs or 120°C for 5 hours is recommended to enhance molded products appearance and prevent drooling.

For carbon fiber filled grades, pre-drying is particularly important, because moisture absorption is high due to the carbon fibers.

Injection Molding


  • 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

» View All PPS Grades Suitable for Injection Molding

But in order 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.

Extrusion


Extrusion PPS grades are commonly available for fiber and monofilament production as well as tubing, rod and slab.

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

Commercially Available PPS (Polyphenylene Sulfide ) Compounds





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