High-temperature Plastics: Rapid Growth In Challenging Applications

August 17, 2024

Plastics, classified by long-term use temperature, can be divided into general-purpose plastics, engineering plastics and high-temperature plastics, of which high-temperature plastics are also known as heat-resistant plastics, high-performance plastics, special engineering plastics and so on.

General-purpose plastics are plastics that are used for a long period of time at temperatures lower than 100 oC; the five major general-purpose plastics include Polyethylene (Polyethylene, PE ), Polypropylene (Polypropylene, PP ), Polystyrene (Polystyrene, PS), Polyvinyl Chloride (Polyvinyl Chloride, PVC ), and Acrylonitrile-Butadiene-Styrene Copolymer (ABS); they have low mechanical properties but are widely used in packaging, home appliance and construction industries because of their wide range of applications and excellent processing properties.

Engineering plastics, are plastics that are used for long periods of time at temperatures ranging from 100 oC to 150 oC; the five major engineering plastics include polycarbonate (Polycarbonate, PC ), Polyoxymethylene (Polyoxymethylene, POM ), Polyester (Polybutylene Terephthalate, PBT), Polyamide (Polyamide, PA) and Polystyrene (Polyphenylene, PA). Polyamide, PA) and Polyphenylene Oxide (PPO); they have good mechanical properties, chemical resistance and abrasion resistance, through the addition of modifiers, can optimize the material, easy to process engineering plastics are widely used in automotive, electronics and machinery industries.

High-temperature plastics, are plastics that can be used for a long time at temperatures higher than 150 oC; they have many excellent properties that can only be manifested at high working temperatures, including good mechanical properties and excellent chemical resistance, but also radiation resistance, flame retardant, and good electrical properties; through modification, the dimensional stability and rigidity of the material can be improved while improving friction properties and adjusting the electrical conductivity; in the military, aviation, aerospace, automotive and oil and gas industries, replacing traditional metals and ceramics, high-temperature plastics continue to have new and challenging applications, becoming one of the fastest-growing plastic products.

1. Bridging Engineering Plastics to High Temperature Plastics - PPA, PARA

Aromatic polyamides include semi-aromatic polyamide (Polyphthalamide, PPA) and fully aromatic polyamide (Polyarylamide, PARA). By introducing semi-aromatic or fully aromatic amide chain segments containing benzene rings into the main chain of the aliphatic PA molecule, the mechanical properties, heat resistance, and dimensional stability of conventional PA are enhanced.

The main suppliers of PPA are BASF, DuPont, DSM, EMS, Evonik, Kuraray, Mitsui, SABIC and Solvay, and the common ones are PA4T, PA6T, PA9T, PA10T and other PPAs.Table 1, taking DuPont's Zytel® as an example, shows and compares the properties of Pa6 , Pa66 and PPA. PPA, where the PPA is PA6T/XT (Hexamethylenediamine + Methylglutylenediamine + Terephthalic Acid).

The main suppliers of PARA are DuPont, Kolon, Solvay, Teijin and Tayho, etc., the most famous of which are DuPont's Nomex (polyisophthaloyl isophthalamide) and Kevlar (all-para-polyarylamide).Nomex's main product forms are paper (insulating paper), sheets and fibers; it has no melting point and starts to decompose at 370 oC or above; it has high dielectric strength, and its properties can be compared with PA6, PA66 and PPA. Began to decompose; high dielectric strength, can withstand short-term 40 kV/mm voltage; good mechanical toughness (1.5 mm thick insulating paper, tensile strength of 1800 N/cm, elongation at break 8.0%); in 220 oC can be used for a long time for more than ten years; chemical corrosion resistance, irradiation resistance and flame retardant; mainly used for electrical insulation (eg, transformers) and flame retardant, etc.. Kevlar main product form is fiber and sheet; no melting point, 427 oC above the beginning of decomposition; high strength, high modulus and toughness (fiber tensile strength of 3.6 GPa, tensile modulus of 130 GPa, elongation at break 3%); long-term use of the temperature of 180 oC; mainly used as a super-strong fibers and reinforcing materials, used in military, aviation and aerospace and other structural components.

2. Examples of replacing steel with plastic - PPS , PAEK, PI

Polyphenylene Sulfide (PPS) is a thermoplastic, semi-crystalline resin with a benzene-sulfur bond in the main chain of the molecule.The main suppliers of PPS are Celanese, DIC, Kureha, Polyplastics, Solvay, Toray, Tosoh, and Zhejiang NHU.PPS can be used for a long period of time at temperatures ranging from 180 to 220 oC with low water absorption and good dimensional stability. It can be used for a long time in the temperature range of 180 to 220 oC, with very low water absorption and good dimensional stability. After modification, it is widely used as a structural material in the electronic, electrical, and automotive industries. Table 2, shows the properties of PPS with Celanese's Fortron® as an example.

Polyaryletherketon (PAEK) is a semi-crystalline, thermoplastic, mainly including Polyetherketone (PEK), Polyetheretherketone ( PEEK ), Polyetherketoneketone (PEKK), and so on. PEKK), etc. The difference between the various varieties of PAEK is the chemical composition, the order and proportion of ether ketone, the glass transition temperature from 143 to 175 oC, the melting point from 338 to 375 oC. PAEK molecular structure contains benzene ring, with good mechanical properties, electrical insulation and chemical resistance; ether bonding and so that it has a flexible, and can be molded with the thermoplastic processing method. The main suppliers of PAEK are AKRO-PLASTIC, Celanese, Evonik, Solvay and Victrex. Table 3, for example, shows the properties of PEEK from Victrex. It is worth mentioning that PEEK is developing rapidly for 3D printing wires and powders, which are available from suppliers such as Lehvoss, Indmatec, Solid Concepts and others.

Polyimide (PI) is a polymer containing an imide (-CO-NH-CO-) on the main chain, including aliphatic, semi-aromatic and aromatic PI three kinds, amorphous-based, thermoplastic and thermosetting. PI has no significant melting point, high temperature resistance of up to 400 oC, high insulating properties; widely used in the field of aviation, aerospace, microelectronics, nano, liquid crystal, separation membranes, laser, etc. The main product form of PI. The main product forms of PI are films, fibers, foams and resins. 3E Etese, Arakawa, DuPont, Kaneka, Mitsui, Taimide, etc. The tensile strength of DuPont's Type 100 HN PI film made from Kapton® is 231 MPa and 139 MPa at 23oC and 200 oC, respectively. 231 MPa and 139 MPa at 23oC and 200 oC, respectively, and the tensile modulus was 2.5 GPa and 2.9 GPa, respectively.Table 4, as an example, shows the properties of PI resins that can be used for injection molding processing, using Mitsui's Aurum® as an example.

Among high-temperature plastics, polyimides (PI) are at the top of the pyramid in terms of temperature resistance dimension. Polyimides are produced by the polymerization of dianhydrides and diamines, and by further introducing ether and amide bonds into the main chain, polyether-imide ( PEI ) and polyamide-imide ( PAI ) can be obtained, respectively. For commercially available thermoplastic polyimides, PI, PEI and PAI are typically represented by Mitsui's Aurum®, Sabic's Ultem ® and Solvay's Torlon®, respectively. Table 5 shows the basic properties of the products from these three suppliers. It is worth noting that Sabic's Ultem® PEI has begun to be used in Stratasys' 3D printing filaments (Ultem® 9085). In summary, polyimides are available in a wide variety of products with outstanding overall performance, ranging from films, fibers, coatings, foams, and composites, and can be selected for a variety of application purposes.

In high-temperature plastics, there is a class of amorphous materials with high transmittance (ASTM D1003), which are transparent plastics (transmittance of visible light at wavelengths of 400-800nm is above 80%), and have higher heat-resistant temperatures compared to common transparent plastics, PS, PC and PMMA , which are able to meet the more stringent requirements for materials at high temperatures in the case of substituting plastics for glass.

3. Examples of Plastics in Place of Glass - PSU, PESU, PPSU , PAR

Polysulfone (PSU or PSF) is a class of thermoplastic resins containing -SO2- in the main chain, amorphous. There are three main types of polysulfone, ordinary bisphenol A-type PSU, polyethersulfone (PESU) and polyarylsulfone (PPSU), the structural formulas of the three are shown in the figure below. Polysulfone's long-term use temperature can reach 180 oC, short-term heat resistance can be up to 220 oC, with good dimensional stability, electrical insulation, chemical and hydrolysis resistance, mainly used in automotive, electronic and electrical, household (food contact) and other fields, especially some transparent parts, is a good alternative to metal, glass and ceramics.

Currently, the main suppliers of polysulfone are BASF, Sabic, Solvay, Sumitomo and so on. Table 6 shows the properties of PSU, PESU, and PPSU using BASF's Ultrason® as an example. All three can be further reinforced with glass fibers and carbon fibers and processed by injection molding and extrusion.

Polyarylate (PAR) is a polyaryl compound, a thermoplastic resin with benzene rings and ester bonds in the main chain, and is amorphous.PAR has good light transmittance (close to 90%), heat resistance, elastic recovery, weathering resistance, and flame retardant properties, and is mainly used in precision devices, automobiles, medical care, food, and daily necessities.A typical representative of PAR is Unitika's U-polymer®, which is a bisphenol resin. polymer®, a copolymer of bisphenol A and terephthalic and isophthalic acid. Table 7 shows some of the properties of U-polymer, and it is worth mentioning that the toughness of PAR is significantly better than that of polysulfone plastics.

4. Special Function Plastics (Fluoroplastics) - PVDF , PTFE , PCTFE, etc.

Fluoroplastics are polyalkanes in which some or all of the hydrogen atoms have been replaced by fluorine atoms. The six common fluoroplastics include Polytetrafluoroethylene (PTFE), Tetrafluoroethylene-Perfluoroalkoxy Vinyl Ether Copolymer (Polyfluoroalkoxy, PFA), Fluorinated Ethylene Propylene (FEP), Ethylene-Perfluoroethylene (PEP), and Ethylene-Perfluoroalkoxy Vinyl Ether Copolymer (PFAVC). , FEP, Ethylene-Tetra-Fluoroethylene Copolymer (Ethylene-Tetra-Fluoro-Ethylene, ETFE), Polyvinylidene fluoride (PVDF) and Polychlorotrifluroethylene (PCTEF). (PCTEF).

Overall, fluoroplastics have excellent corrosion resistance, high and low temperature resistance, low coefficient of friction, good self-lubrication and dielectric properties, and are widely used in chemical, electronic, electrical, aviation, aerospace, machinery, construction, medicine, automotive and other industrial fields. The main properties of the six fluoroplastics are shown in Table 9, of which PTFE melt viscosity is too large to be used in injection molding process; PFA, FEP, ETFE, PVDF and PCTEF have better processing performance and can be molded by injection molding, extrusion and other processes. At present, the main suppliers of fluoroplastics are 3M, Chemours (formerly DuPont Fluoroplastics), Dakin, Solvay, Arkema, etc. The product forms include extruded profiles, pellets, films, powders, etc. It is worth mentioning that some fluoroplastics, such as PFA, FEP, ETFE, PVDF and PCTEF, are not suitable for injection molding. It is worth mentioning that some fluoroplastics, such as PVDF, have special properties such as barrier and piezoelectricity that traditional high temperature plastics do not have, and are developing rapidly in some challenging new applications in lithium batteries, semiconductors and other industries.

In short, high-temperature plastics mainly include aromatic polyamide (PPA, PARA), polyphenylene sulfide (PPS), polyarylene ether ketone (PEAK), polyimide (PI), polysulfone (PSU, PESU, PPSU), polyarylate (PAR), liquid crystal polymer (LCP) and fluorine plastics, etc., and their long-term use of the temperature of 150 to 300 oC, the main features are respectively Their main features include high heat resistance, high strength, high transparency, high fluidity and high friction resistance, etc., and the performance can be further improved by modification. These high-temperature plastics have their own advantages and disadvantages, in the aerospace, automotive, electronics and other industries, plastic instead of steel, plastic instead of glass (or ceramics) and a variety of challenging applications, require different material selection and product design to meet the various requirements.

Author:

Ms. Tina

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sales@honyplastic.com

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