Polyphenylene Sulfide (PPS)

August 30, 2024

wanplas

Industry Knowledge, Plastic Materials

Polyphenylene sulfide (PPS) is a new type of high-performance thermoplastic resin with the advantages of high mechanical strength, high temperature resistance, chemical resistance, flame retardancy, good thermal stability, excellent electrical properties, etc. It is widely used in the fields of electronics, automobiles, machinery and chemicals.

Introduction

Polyphenylene sulfide is the full name of polyphenylene sulfide. It is a thermoplastic resin with phenylthio groups in the main chain of the molecule. Polyphenylene sulfide is a crystalline polymer. The unstretched fiber has a large amorphous area (crystallinity is about 5%), crystallization exotherm occurs at 125℃, the glass transition temperature is 150℃; the melting point is 281℃. The stretched fiber produces partial crystallization (increased to 30%) during the stretching process. If the stretched fiber is heat-treated at a temperature of 130-230℃, the crystallinity can be increased to 60-80%. Therefore, the stretched fiber has no obvious glass transition or crystallization exotherm, and its melting point is 284℃. With the increase of crystallinity after stretching and heat setting, the density of the fiber also increases accordingly, from 1.33g/cm³ before stretching to 1.34g/ cm³ after stretching, and can reach 1.38g/ cm³ after heat treatment. Molding shrinkage: 0.7% Molding temperature: 300-330℃.

PPS is a special engineering plastic with excellent comprehensive performance. PPS has excellent high temperature resistance, corrosion resistance, radiation resistance, flame retardancy, balanced physical and mechanical properties, excellent dimensional stability and excellent electrical properties. It is widely used as a structural polymer material. After filling and modification, it is widely used as a special engineering plastic. At the same time, it can also be made into various functional films, coatings and composite materials, which have been successfully applied in the fields of electronics, aerospace, automobile transportation, etc. China’s enterprises have actively carried out research and development and have initially formed a certain production capacity, changing the previous situation of complete dependence on imports. However, China’s PPS technology still has problems such as few product varieties, few high-function products, and urgent expansion of production capacity. These will be the focus of the next development of PPS.

Features

The characteristics of PPS are as follows:

1. Good chemical resistance.
2. Low creep.
3. Low water absorption.
4. Good dimensional stability.
5. High elastic modulus.
6. Flame retardant.

Polyphenylene sulfide (PPS) is known as the six major special engineering plastics together with polyetheretherketone (PEEK), polysulfone (PSF), polyimide (PI), polyarylate (PAR) and liquid crystal polymer (LCP).

Outstanding performance of PPS: good heat resistance, heat deformation temperature is generally greater than 260℃, can be used in the temperature range of 180~220℃, PPS is one of the best heat-resistant varieties of engineering plastics; corrosion resistance is close to tetrafluoroethylene, and chemical resistance is second only to polytetrafluoroethylene; excellent electrical properties; excellent mechanical properties; good flame retardant properties.

Disadvantages of PPS: The price is too high, which is the lowest price among high-temperature resistant materials, but much higher than general engineering plastics; poor toughness and brittleness; medium viscosity is unstable.

Pure PPS is rarely used due to its brittleness, and most of the PPS used is its improved performance varieties, including 40% glass fiber reinforced PPS (R-4), inorganic filled PPS (R-8), carbon fiber reinforced PPS (G-6), etc. PPS is developing rapidly and is expected to become the sixth largest engineering material.

(1) General properties: PPS is a white, highly crystalline, hard and brittle polymer. The relative density of pure PPS is 1.3, but it will increase after modification. PPS has a very low water absorption rate, generally only about 0.03%. PPS has good flame retardancy, and its oxygen index is as high as 44%. Compared with other plastics, it is a highly flame retardant material among plastics (the oxygen index of pure PVA is 47%, PSF is 30%, PA66 is 29%, MPPO is 28%, and PC is 25%).

(2) Mechanical properties: The mechanical properties of pure PPS are not high, especially the impact strength. After being reinforced with glass fiber, the impact strength will be greatly improved, from 27J/m to 76J/m, an increase of 3 times; the tensile strength will increase from 6Mpa to 137Mpa, an increase of 1 time. PPS has high rigidity. It is rare in engineering materials. The bending modulus of pure PPS can reach 3.8Gpa, and it can reach 12.6Gpa after inorganic filling modification, an increase of 5 times. However, PPO, which is famous for its rigidity, is only 2.55Gpa, and PC is only 2.1Gpa. PPS has good creep resistance under load; high hardness; high wear resistance, and its modulus at 1000 revolutions is only 0.04g, which will be further improved after filling with F4 and molybdenum disulfide; PPS also has a certain self-lubricating property. The mechanical properties of PPS are less sensitive to temperature.

(3) Thermal properties: PPS has excellent thermal properties. It can withstand 260°C for a short period of time and can be used for a long time at 200-240°C. Its thermal resistance is comparable to that of PI and is second only to F4 plastic, which is rare among thermosetting plastics.

(4) Electrical properties: PPS has outstanding electrical properties. Compared with other engineering materials, its dielectric constant and dielectric loss tangent are relatively low, and do not change much over a large frequency, temperature and temperature range. PPS has good arc resistance, comparable to thermosetting plastics. PPS is often used as electrical insulation material, which is rare among thermosetting materials. Its usage accounts for about 30%.

(5) Environmental performance: One of the biggest features of PPS is its good chemical corrosion resistance. Its chemical stability is second only to F4:

PPS is stable to most acids, esters, copper, phenol, fatty acids, aromatic acids, chlorinated acids, etc., but is not resistant to chlorinated biphenyls, oxidizing acids, oxidants, concentrated sulfuric acid, concentrated nitric acid, aqua regia, hydrogen peroxide, sodium hypochlorite, etc. PPS has good radiation resistance.

Production method

There are many methods for synthesizing PPS, such as self-condensation of halogenated thiophenols, melt polymerization of halogenated diphenyl and sulfur, electrophilic reaction of sulfur and benzene, solution polycondensation of alkali metal sulfide and 4-dihalobenzene (sodium sulfide method), solution polycondensation of sulfur and 4-dichlorobenzene (sulfur solution method), polymerization of diphenyl disulfide under the action of Lewis acid, etc. Currently, the sodium sulfide method and sulfur solution method are used for industrial production.

1. Sodium sulfide method

It is obtained by polycondensation reaction of sodium sulfide and p-dichlorobenzene in a polar solvent.

2. Sulfur solution method

The solvent used in the sulfur solution method to produce PPS resin is the same as that of the sodium sulfide method, and the reaction conditions are also roughly the same. The main difference is that the sulfur-containing monomer used is a single substance (sulfur) rather than a compound.

Application Areas

Electronics: high-voltage components, casings, sockets, terminals on televisions and computers, starting coils, blades, brush brackets and rotor insulation parts of electric motors, contact switches, relays, electric irons, hair dryers, lamp holders, heaters, Class F films, etc.

Automobile industry: Applicable to exhaust gas recirculation valves and water pump impellers, as well as carburetors, exhaust devices, exhaust regulating valves, light reflectors, bearings, sensor components, etc.

Mechanical industry: used as bearings, pumps, valves, pistons, precision gears, as well as copiers, cameras, computer parts, catheters, sprayers, fuel injectors, instrument parts, etc.

Chemical industry: used to make acid- and alkali-resistant valve pipes, pipe fittings, valves, gaskets, submersible pumps or impellers and other corrosion-resistant parts.

Engineering plastics: used to manufacture automotive parts, anti-corrosion coatings, electrical insulation materials, etc.

Environmental protection field: PPS fiber filter material is used in smelting, chemical industry, building materials, thermal power, waste incinerator, coal-fired boiler and other industries with high temperature and harsh working conditions. It is a high-quality, high-efficiency and high-temperature resistant filter material.

Tableware field: used to make chopsticks, spoons, bowls and plates and other tableware.

Production Development

Common polyphenylene sulfide adhesives mainly include the following varieties:

Note: The above adhesives can be used for bonding most common materials such as metal, plastic, glass, ceramic, wood, etc. Their color, curing speed and viscosity can be customized according to needs.

Development situation in China

The research and production of PPS in China began in the early 1970s. More than 20 companies have established PPS resin synthesis pilot or production facilities, but they generally have fatal weaknesses such as low technical level and inadequate process.

Since the 21st century, there are many China’s companies engaged in the production and development of PPS composite materials, such as Chenguang Chemical Research Institute, Beijing Chemical Research Institute, Guangzhou Chemical Research Institute, etc., which have made great achievements in the fields of PPS glass fiber reinforcement, carbon fiber and inorganic mineral filled reinforced PPS molding processing and application, Beijing FRP Research Institute in the preparation of continuous fiber reinforced PPS composite plates, and Sun Yat-sen University in the research of PPS/carbon fiber composite materials. However, domestic composite granular manufacturers still have the problem of small output and single variety, and most of them are general varieties – glass fiber reinforced materials and inorganic filled modified varieties.

Since 2003, the total market demand for PPS modified and compounded granules in China has grown rapidly, with an annual growth rate of 15%-20%. The PPS product models consumed are still mainly general-purpose varieties with 0%-40% glass fiber reinforcement, and are mainly used in electronic appliances and precision machinery. The consumption in the fields of automobiles, motorcycles, petroleum, and chemicals is also growing steadily. With the rapid development of China’s electronic appliances and automobile industries, the global production and demand for PPS has become tense since the beginning of the 21st century. With the development of society, the total demand for PPS in the automobile and electronics industries will further expand. The Chinese market is forming a dual competition situation for PPS production at home and abroad, which will be conducive to the further promotion of PPS in China and the expansion of its market and application areas, as well as the development of the international market.

In combination with the development trend of PPS and new materials at home and abroad, on the basis of developing new PPS material varieties and developing new PPS synthesis methods, we should also focus on the research and development of new modified materials and special materials, actively develop new PPS composite material modified varieties, and establish larger-scale production equipment as soon as possible. Among them, it is imperative to establish a 5,000-8,000 tons/year PPS resin production line as soon as possible. This is a necessary strategic measure for the development of China’s high-performance structural materials, which is of great significance to breaking foreign technical restrictions and blockades and meeting the needs of the national economy and military industry for high-performance structural materials.

Types

1. Celstran polyphenylene sulfide type SF6-01

Celstran Polyphenylene Sulfide Type SF6-01 is a 6% long stainless steel fiber polyphenylene sulfide. This material is endowed with excellent static and dynamic dissapative properties. Celstran long fiber stailess steel products offer a much higher level of electrical conductivity than short fiber stainless steel materials.

2. Celstran PPS-GF50-01-US

50% long chain glass fiber reinforced polyphenylene sulfide.

Polyphenylene sulfide – hGR20

Polyphenylene sulfide – hGR20 is glass fiber reinforced polyphenylene sulfide

It is a product of PPS resin and glass fiber. The inherent properties of polyphenylene sulfide determine the polyphenylene sulfide resin and their compounds, which include good mechanical properties, high creep resistance, high temperature resistance, friction, flame retardancy, chemical resistance, excellent electrical insulation properties, arc resistance, low mold shrinkage utility, easy processing, good dimensional stability, and radiation resistance.

Due to its excellent properties, polyphenylene sulfide-hGR20 is widely used in electronic appliances, such as: connectors, sockets, and several components of instruments. Polyphenylene sulfide can be used to make elements in high strength, high temperature resistance, electrical insulation is the most important in aviation. It is also used for precise electrical sockets, high hardness shells, and in the military to resist high temperature parts.

Polyphenylene sulfide composite hFR61

Polyphenylene sulfide, polyphenylene sulfide composite hFR61 filled, which is filled with mineral and glass fiber in polyphenylene sulfide resin base. It has excellent electrical insulation properties, arc resistance, high temperature resistance, inherent flame retardancy, chemical resistance, high rigidity, creep resistance, low water absorption, easy processing, low mold shrinkage, good dimensional stability and radiation resistance. Its color is black.

Identification criteria

1. Surface finish is an important indicator to measure the quality grade of various types of recycled material particles.

The surface of high-quality recycled materials is smooth and lubricated

2. Transparency is an important indicator for measuring the quality grade of medium and high-end recycled material particles.

Transparent materials are of good quality

3. Color uniformity and consistency are important indicators for measuring the quality grade of colored recycled material particles.

White, creamy white, yellow, blue, black and other colors

4. Particle density is an important aspect to test the level of regeneration technology.

Poor plasticization and loose particles.

5. Check whether the recycled particles float or sink in water to test the filler content of PP and PE particles.

For recycled materials, different recycled materials have different uses. It is difficult to formulate unified standards because there is no such standard to fully meet the user’s process requirements.