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High-performance plastics are plastics that meet higher requirements than ''standard'' or ''engineering'' plastics. They are more expensive and used in smaller amounts.


Definition

High performance plastics differ from standard plastics and engineering plastics primarily by their temperature stability, but also by their chemical resistance and
mechanical properties A materials property is an intensive property of a material, i.e., a physical property that does not depend on the amount of the material. These quantitative properties may be used as a metric by which the benefits of one material versus another ca ...
, production quantity, and price... There are many synonyms for the term high-performance plastics, such as: high temperature plastics, high-performance polymers, high performance thermoplastics or high-tech plastics. The name high temperature plastics is in use due to their
continuous service temperature Continuity or continuous may refer to: Mathematics * Continuity (mathematics), the opposing concept to discreteness; common examples include ** Continuous probability distribution or random variable in probability and statistics ** Continuous g ...
(CST), which is always higher than 150 °C by definition (although this is not their only feature, as it can be seen above). The term " polymers" is often used instead of "plastics" because both terms are used as
synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
s in the field of engineering. If the term "high-performance thermoplastics" is used, it is because both standard and technical as well as high-performance plastics are always thermoplastics.
Thermosets In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening (" curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and ...
and elastomers are outside of this classification and form their own classes. However, the differentiation from less powerful plastics has varied over time; while nylon and poly(ethylene terephthalate) were initially considered powerful plastics, they are now ordinary.


History

The improvement of mechanical properties and thermal stability is and has always been an important goal in the research of new plastics. Since the early 1960s, the development of high-performance plastics has been driven by corresponding needs in the aerospace and
nuclear technology Nuclear technology is technology that involves the nuclear reactions of atomic nuclei. Among the notable nuclear technologies are nuclear reactors, nuclear medicine and nuclear weapons. It is also used, among other things, in smoke detectors an ...
. Synthetic routes for example for PPS,
PES Pes (Latin for "foot") or the acronym PES may refer to: Pes * Pes (unit), a Roman unit of length measurement roughly corresponding with a foot * Pes or podatus, a * Pes (rural locality), several rural localities in Russia * Pes (river), a river ...
and
PSU PSU may refer to: Organizations Military *Police Support Unit, a paramilitary wing of the Zimbabwe Republic Police *Port Security Unit, a U.S. Coast Guard expeditionary force protection unit Political parties * Parti Socialiste Unifié (disambig ...
were developed in the 1960s by Philips, ICI and Union Carbide. The
market entry Market is a term used to describe concepts such as: *Market (economics), system in which parties engage in transactions according to supply and demand *Market economy *Marketplace, a physical marketplace or public market Geography *Märket, an ...
took place in the early 70s. A production of
PEEK Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family, used in engineering applications. The polymer was first developed in November 1978, later being introduced to the market by Vic ...
(ICI), PEK (ICI) and PEI (General Electric and GE) via polycondensation was developed in the 1970s. PEK was offered since 1972 by Raychem, however, made by an electrophilic synthesis. Since
electrophilic synthesis In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carri ...
has in general the disadvantage of a low selectivity to linear polymers and is using aggressive reactants, the product could hold only a short time on the market. For this reason, the majority of high-performance plastics is nowadays produced by polycondensation processes. In manufacturing processes by polycondensation a high purity of the starting materials is important. In addition, the stereochemistry plays a role in achieving the desired properties in general. The development of new high-performance plastics is therefore closely linked to the development and economic production of the constituent monomers.


Characteristics

High performance plastics meet higher requirements than standard and engineering plastics because of their more desirable mechanical properties, higher chemical and/or a higher heat stability. Especially the latter makes processing difficult, often requiring specialized machinery. Most high-performance plastics are exploited for a single property (e.g. heat stability), in contrast to engineering plastics which provide moderate performance over a wider range of properties. Some of their diverse applications include: fluid flow tubing, electrical wire insulators, architecture, and fiber optics. High performance plastics are relatively expensive: The price per kilogram may be between $5 (PA 46) and $100 (
PEEK Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family, used in engineering applications. The polymer was first developed in November 1978, later being introduced to the market by Vic ...
). The average value is slightly less than 15 US-Dollar/kg. High-performance plastics are thus about 3 to 20 times as expensive as engineering plastics. Also in future there cannot be expected a significant price decline, since the investment costs for production equipment, the time-consuming development and the high distribution costs are going to remain constant. Since production volumes are very limited with 20.000 t/year the high-performance plastics are holding a market share of just about 1%. Among the high-performance polymers, fluoropolymers have 45% market share (main representatives: PTFE), sulfur- containing aromatic polymers 20% market share (mainly PPS), aromatic polyarylether and Polyketones 10% market share (mainly PEEK) and liquid crystal polymers (LCP) 6%. The two largest consumers of high-performance plastics are the electrical and electronics industries (41%) and the automotive industry (24%). All remaining industries (including
chemical industry The chemical industry comprises the companies that produce industrial chemicals. Central to the modern world economy, it converts raw materials (oil, natural gas, air, water, metals, and minerals) into more than 70,000 different products. The ...
) have a share of 23%.


Thermal stability

Thermal stability is a key feature of high-performance plastics. Also mechanical properties are closely linked to the thermal stability. Based on the properties of the standard plastics some improvements of mechanical and thermal features can already be accomplished by addition of stabilizers or reinforcing materials ( glass and
carbon fibers Carbon fibers or carbon fibres (alternatively CF, graphite fiber or graphite fibre) are fibers about in diameter and composed mostly of carbon atoms. Carbon fibers have several advantages: high stiffness, high tensile strength, high stren ...
, for example) or by an increase in the degree of polymerization. Further improvements can be achieved through substitution of aliphatic by aromatic units. Operating temperatures up to 130 °C are reached in this way. Thermosets (which do not belong to the high-performance plastics, see above) have a similar temperature stability with up to 150 °C. An even higher service temperature can be reached by linking of aromatics (e.g. phenyl) with oxygen (as diphenyl ether group e. g. PEEK),
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
(as
diphenyl sulfone groups Biphenyl (also known as diphenyl, phenylbenzene, 1,1′-biphenyl, lemonene or BP) is an organic compound that forms colorless crystals. Particularly in older literature, compounds containing the functional group consisting of biphenyl less one ...
in PES or
diphenyl group Biphenyl (also known as diphenyl, phenylbenzene, 1,1′-biphenyl, lemonene or BP) is an organic compound that forms colorless crystals. Particularly in older literature, compounds containing the functional group consisting of biphenyl less one ...
, for example in PPS) or nitrogen (
imide In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis. In terms of commercial applications, ...
group in PEI or PAI). Resulting operating temperatures might be between 200 °C in the case of PES to 260 °C in case of PEI or PAI. The increase in temperature stability by incorporating aromatic units is due to the fact, that the temperature stability of a polymer is determined by its resistance against thermal degradation and its
oxidation resistance Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...
. The thermal degradation occurs primarily by a
statistical Statistics (from German: ''Statistik'', "description of a state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industria ...
chain scission; depolymerization and removal of low molecular weight compounds are playing only a minor role. The thermal-oxidative degradation of a polymer starts at lower temperatures than the merely thermal degradation. Both types of degradation proceed via a radical mechanism. Aromatics offer a good protection against both types of degradation, because
free radicals In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spont ...
can be delocalized through the π-system of the aromatic and stabilized. In this way the thermal stability is strongly increasing.
Poly(p-phenylene) Poly(''p''-phenylene) (PPP) is made of repeating ''p''-phenylene units, which act as the precursor to a conducting polymer of the rigid-rod polymer family. The synthesis of PPP has proven challenging, but has been accomplished through excess pol ...
can serve as an example, it consists exclusively of aromatics and provides extremely stability, even at temperatures above 500 °C. On the other hand the rigidity of the
chains A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A c ...
makes it more or less inprocessible. To find a balance between processability and stability, flexible units can be incorporated into the chain (e.g., O, S, C(CH3). Aromatics can also be substituted by other rather rigid units (e. g. SO2, CO). By mixing these different elements the diversity of high-performance plastics is created with their different characteristics. In practice a maximum temperature resistance (about 260 °C) can be obtained with fluoropolymers (polymers, in which the hydrogen atoms of the hydrocarbons have been replaced by fluorine atoms). Among them,
PTFE Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemour ...
has the largest market share with 65-70 %. Fluorine-containing polymers are, however, not suitable to serve as construction material due to poor mechanical properties (low
strength Strength may refer to: Physical strength *Physical strength, as in people or animals *Hysterical strength, extreme strength occurring when people are in life-and-death situations *Superhuman strength, great physical strength far above human ca ...
and
stiffness Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a b ...
, strong
creep Creep, Creeps or CREEP may refer to: People * Creep, a creepy person Politics * Committee for the Re-Election of the President (CRP), mockingly abbreviated as CREEP, an fundraising organization for Richard Nixon's 1972 re-election campaign Art ...
under load).


Crystallinity

High-performance plastics can be divided in amorphous and semi-crystalline polymers, just like all polymers. Polysulfone (PSU), poly(ethersulfone) (PES) and polyetherimide (PEI) for example are
amorphous In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal. Etymology The term comes from the Greek ''a'' ("wi ...
; poly(phenylene sulfide) (PPS), polyetheretherketone (PEEK) and polyether ketones (PEK), however are
semi-crystalline Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion ...
. Crystalline polymers (especially those reinforced with fillers) can be used even above their glass transition temperature. This is because semi-crystalline polymers have, in addition to a glass temperature Tg, a
crystallite melting point A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains. Bacillite is a type of crystallite. It is rodlike with parallel longulites. Stru ...
Tm, which is usually much higher. For example PEEK possesses a Tg of 143 °C but remains usable up to 250 °C (
continuous service temperature Continuity or continuous may refer to: Mathematics * Continuity (mathematics), the opposing concept to discreteness; common examples include ** Continuous probability distribution or random variable in probability and statistics ** Continuous g ...
= 250 °C). Another advantage of semi-crystalline polymers is their high resistance against chemical substances: PEEK possesses a high resistance against aqueous acids, alkalies and organic solvents.


See also

*
Commodity plastics Commodity plastics or commodity polymers are plastics produced in high volumes for applications where exceptional material properties are not needed (such as packaging, food containers, and household products). In contrast to engineering plastics ...
* Engineering plastic


References

{{plastics Thermoplastics