【Deep coating society popular science knowledge】Common 8 kinds of high-temperature resistant engineering plastics, how many do you know?

Plastics are classified according to long-term use temperature, which can be divided into general plastics, engineering plastics and high-temperature engineering plastics, of which high-temperature plastics are also called heat-resistant plastics, high-performance plastics, special engineering plastics, etc
.

The long-term use temperature of general-purpose plastics is below
100 °C.
Usually includes PE, PP, PS, PVC, ABS
.
General plastics are the type of plastics we use the most on a daily basis, and are usually used as packaging, daily necessities, toys, etc
.

The long-term use temperature of engineering plastics is about
100 °C to 150 °C.
The five major engineering plastics include PA, POM, PBT, PC and PPO
.
Usually used in mechanical parts, automobiles, electrical and electronic fields and other fields
.

The use temperature of high-temperature engineering plastics is above 150 °C, and in addition to high heat resistance and flame retardancy, these materials usually have excellent machinability, aging resistance, dimensional stability and excellent electrical properties
.
It can be used to replace metal materials and is widely used in electronic appliances, aerospace, medical equipment, automobiles, and military fields
.
It is the material at the top of the
plastic pyramid.

Common high-temperature engineering plastics are divided into the following 8 categories:

NO.
01
High temperature nylon

High-temperature nylon is divided into three categories:

Aliphatic nylon – PA46

PA46 is an aliphatic polyamide formed by polycondensation of butanediamine and adipic acid, PA46 has a higher number of amides per given length of chain than PA6 and PA66, and the chain structure is more symmetrical, which makes it crystallinity up to 70% and gives it a very fast crystallization rate
.

The melting point of PA46 is 295 °C, the HDT (heat distortion temperature) of unreinforced PA46 is 160 °C, and after glass fiber reinforcement, its HDT can be as high as 290 °C, and the long-term use temperature is also 163 °C
.
The unique structure of PA46 gives unique properties that cannot be achieved with other materials

PA46 is mainly used in electronics, aerospace, and automotive
.

Semi-aromatic nylon – PPA

PPA is formed by polycondensation of diacids containing benzene rings and aliphatic diamines, and its melting point is between 310-325 °C and the heat distortion temperature is between 280-290 °C
.
The main varieties are PA4T, PA6T, PA9T, PA10T, etc
.

Compared with ordinary PA66, PPA has a very low water absorption rate, even if it is soaked in cold water for several years, its tensile strength can be maintained at more than 80%, and PPA oil resistance is very good, even at high temperatures, it has extremely high resistance to lubricating oil and fuel
.
PPA also has excellent dimensional stability and weather resistance
.

Commonly used in automobiles, electrical and electronics, machinery industry, daily necessities field
.

Fully aromatic nylon – PARA

PARA was invented by DuPont, the most famous of which are Nomex (polyisophthaloyl isophthalamine also known as aramid 1313) and Kevlar (full para-polyarylamide also known as aramid 1414).

This kind of material is mainly used in the preparation of high-performance fibers and sheets, and the fibers made have the characteristics of
high strength, high rigidity, high modulus, high heat resistance and high dielectric strength.

It can be applied to ultra-strong fibers and reinforcements for structural components
such as military, aviation and aerospace.

NO.
02
Polyphenylene sulfide (PPS).

Polyphenylene sulfide (PPS) is the fastest growing and largest amount of special engineering plastics in recent years, with excellent high temperature resistance, chemical resistance, weather resistance, flame retardancy, and electrical properties, good dimensional stability and other advantages, is widely used in automobiles, electronic and electrical, machinery industry, petrochemical, pharmaceutical industry, light industry and military, aerospace, 5G communications and other fields, is the most widely used special engineering plastics
.

PPS is also the most localized special engineering plastic in China, and the self-sufficiency rate can reach more than
80%.

According to incomplete statistics, the production capacity of major global polyphenylene sulfide (PPS) enterprises exceeds 200,000 tons
.
From the perspective of capacity distribution, the current global polyphenylene sulfide (PPS) industry production capacity is mainly concentrated in Japan and China
.

Summary table
of PPS major enterprise capacity as of 2021.

Traditional PPS giants such as DIC, Toray, Solvay, and Wu Yu are still relatively leading in PPS production and technology, and the production capacity of these four companies accounts for more than
56% of the global production capacity.
However, Chinese enterprises are showing a rapid rise momentum, Zhejiang Xinhecheng, Chongqing Juli and other domestic enterprises have formed large-scale production, and many other enterprises have mass production or planning layout
.

NO.
03
Polyaryletherketone (PAEK) class

Polyaryletherketone (PAEK), is the main chain of phenylene ring through ether bonds, ketone bonds connected polymer, according to ether group, ketone group number and order can be divided into polyetherether ketone (PEEK), polyetherketone ketone (PEKK), polyetherketone etherketone ketone (PEKEKK) and so on
.

PEEK (polyetheretherketone)

PEEK is a special engineering plastic
with excellent comprehensive performance.
Its heat resistance, water resistance, solvent resistance and electrical insulation are excellent; high fatigue strength; Radioactivity resistance is the best of all plastics; The oxygen index is high, and the smoke produced when burned is low and non-toxic.

PEEK artificial skeleton
.

PEK (polyetherketone)

Because the ratio of ether bonds and ketone groups in its molecular structure is lower than that of PEEK, the melting point and glass transition temperature of PEK are higher than that of PEEK, and its heat resistance is better than that of PEEK, and the continuous use temperature is 250 °C
.

PEK profiles
.

PEKK (polyetherketone ketone)

PEKK Chinese called polyetherketone ketone, is a high-performance material
.
The material has a high melting point, almost 300°C to 600°C, and is highly resistant to chemicals and abrasion
.
In recent years, the application of PEKK in the field of 3D printing has made rapid progress, and it has better performance
than traditional 3D printing materials.

PEKK is used in 3D printing
.

NO.
04
Polyimide (PI) class

Polyimide (PI) is an aromatic heterocyclic polymer compound with a molecular structure containing imide-based links, which is currently one of the best heat-resistant varieties of engineering plastics, can withstand extreme temperatures, thermal decomposition temperature up to 600 °C, and will not be brittle in
liquid helium at -269 °C.
In addition, it has excellent mechanical properties, acid and alkali resistance, biocompatibility and electrical properties
.

Polyimide engineering plastics can be divided into both thermosetting and thermoplastic, can be divided into polyterephthalimide (PMMI), polyetherimide (PEI), polyamideimide (PAI), etc.
, and have their own uses
in different fields.

PMMI heat distortion temperature of 360 °C under load of 1.
8MPa, excellent electrical properties, can be used for precision parts under special conditions, high temperature resistant self-lubricating bearings, sealing rings, blower impellers, etc.
, can also be used for valve parts in contact with liquid ammonia, jet engine fuel supply system parts
.

PEI has excellent mechanical properties, electrical insulation properties, radiation resistance, high temperature resistance and wear resistance, good melting fluidity, molding shrinkage of 0.
5% ~ 0.
7%, can be used injection and extrusion molding, post-treatment is easier, can also be combined with other materials by welding method, widely used
in electronic appliances, aviation, automobiles, medical equipment and other industries.

The strength of PAI is the highest among the current non-reinforced plastics, with tensile strength of 190MPa, bending strength of 250MPa, and heat deflection temperature of up to 274°C
under 1.
8MPa load.
PAI has good ablation resistance and electromagnetic properties at high temperature and high frequency, and has good adhesion properties to metals and other materials, mainly used in gears, bearings and copiers separating claws, etc.
, and can also be used for ablative materials, permeable materials and structural materials
of aircraft.

NO.
05

Polysulfone (PSU) class

PSU is a slightly amber, amorphous transparent or translucent polymer, its excellent mechanical properties, rigidity, wear resistance, high strength, even at high temperature to maintain excellent mechanical properties is its outstanding advantages; Its range is -100~150 °C, long-term use temperature is 160 °C, short-term use temperature is 190 °C
.

Polysulfone has common bisphenol A type PSU (commonly known as PSU), polyphenylsulfone and polyethersulfone
.

Molecular formula of ordinary bisphenol A type PSU:

The conjugated effect of sulfone groups provides oxidation resistance and thermal stability; The ether chain improves toughness, and the benzene ring ensures its mechanical strength and modulus
.

Molecular formula of polyphenylsulfone PPSU:

The benzene ring on the polyphenylsulfone backbone provides high heat resistance and mechanical properties; Ether bonds provide excellent fluidity and processability
.

Molecular formula of polyethersulfone PESU:

Ether groups provide compliance and high flowability, sulfone groups provide heat resistance, and phenylene groups provide rigidity
.

Performance comparison of
bisphenol A type polysulfone, polyarylsulfone and polyethersulfone.

NO.
06
Polyaryl ester (PAR).

Polyaryl ester (PAR) is a thermoplastic resin
that contains benzene rings and ester bonds on the backbone.
PAR has good light transmittance (close to 90%), toughness, heat resistance, elastic recovery, weather resistance and flame retardant properties, and the continuous use temperature reaches up to 170°C
.
Mainly used in precision devices, automobiles, medical, food and daily necessities
.

PAR structure is similar to PC, its performance is generally the same, can be shared molding, but PAR main chain on the aromatic ring density is high, so that PAR heat resistance is better than PC, heat distortion temperature is 20~40 °C higher than PC, and ultraviolet resistance, creep resistance is excellent
.
However, elongation at break and impact resistance are not as good as polycarbonate
.

Performance comparison of
PAR and PC.

NO.
07

Liquid crystal polymer (LCP)

LCP Chinese name is liquid crystal compound, and the so-called "liquid crystal" is a substance
that has the fluidity of a liquid in a molten state and maintains an orderly arrangement of crystal molecules.

The mechanical properties of LCP are excellent, and the biggest feature is that the relative strength increases
as the wall thickness becomes thinner.
LCP has good thermal performance, continuous use temperature can reach 200°C-300°C
.

LCP has a small dielectric constant and dielectric loss, so it is used in electronic devices such as connectors, sockets, switches, brackets, and sensors
.
The most widely researched concern is the application of 5G antennas for
mobile phones.

NO.
08
Fluoroplastics

Fluoroplastie refers to plastics
made from fluororesins.
The main varieties are polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), polyperfluoroethylene propylene (FEP), polyvinylidene fluoride (PVDF) and so on
.
The use temperature is between
150°C-260°C.

Source: Engineering Plastics Application

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