Thermoplastic high temperature engineering

ICI Plastics Division, P.O. Box No. 6, Bessemer Road, Welwyn Garden City, Hertfordshire, England 

JOHN B. ROSE, GEORGE O. RUDKIN, and JOSEPH FELTZIN ICI America Inc., New Murphy Road Concord Pike, Wilmington, DeL 19899 

The search for thermoplastic materials which can be used for long periods at 300°F and above led logically to polymers composed 

Routes to aromatic polysulphones were discovered independently and almost simultaneously in the early 1960 s in the laboratories of the 3H Corporation (3) and Union Carbide Corporation (6) in the USA and at the Plastics Division of ICI in the UK (4). All three companies have since commercialised their disciveries. In 1963 Union Carbide introduced Udel Polysulfone which is rated to have a continuous use tmp- 

ACS Symposium Series American Chemical Society Washington, DC, 1974. 

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The typical mechanical properties that qualify PCTFE as a unique engineering thermoplastic are provided ia Table 1 the cryogenic mechanical properties are recorded ia Table 2. Other unique aspects of PCTFE are resistance to cold flow due to high compressive strength, and low coefficient of thermal expansion over a wide temperature range. 

The largest use for 2,4-dicumylphenol is in a production of a uv stabilizer of the benzotriazole class, 2-(2 -hydroxy-3, 5 -dicumylphenyl)benzotriazole [70321-86-7] which is used in engineering thermoplastics where high molding temperatures are encountered (67). The high molecular weight of... 

Polyurethane engineering thermoplastics are also manufactured from MDI and short-chain glycols (49). These polymers were introduced by Upjohn/Dow under the trade name Isoplast. The glycols used are 1,6-hexanediol and cyclohexanedimethanol. 1,4-Butanediol is too volatile at the high processing temperatures used in the reaction extmsion process. Blends of engineering thermoplastics with TPU are also finding uses in many appHcations... 

COLLYER, A. A., A Practical Guide to the Selection of High Temperature Engineering Thermoplastics, Elsevier Advanced Technology, London (1990)... 

The presence of the either linkages is sufficient to allow the material to be melt processed, whilst the polymer retains many of the desirable characteristics of polyimides. As a consequence the material has gained rapid acceptance as a high-temperature engineering thermoplastics material competitive with the poly-sulphones, poly(phenylene sulphides) and polyketones. They exhibit the following key characteristics ... 

Thermomechanical behaviour is most probably the most widely exploited property of engineering thermoplastics. Figure 3.1 shows the behaviour of two types of thermoplastic, one amorphous and the other semicrystalline, versus temperature. We can see several steps moving from low to high temperatures ... 

Nylon-6,6 was the first engineering thermoplastic and till 1953 represented the entire annual engineering thermoplastic sales. Plastic nylon-6,6 is tough, rigid, and need not be lubricated. It has a relatively high use temperature (to about 270°C) and is used in the manufacture of many items from hair brush handles to automotive gears. 

Engineering Thermoplastics Polyolefins and Styrenics Table 2.3 Materials with High Glass Transition Temperatures (26)... 

Fluoropolymers. These form one of our oldest and most spectacular families of engineering plastics. Polytetrafluoroethylene was developed by DuPont over two decades ago, and more recently by Allied Chemical, Hoechst, ICI, Pennwalt, and other manufacturers as well. It combines unusually low adhesion and friction, high temperature and flame resistance, excellent electrical properties, and extreme chemical inertness. Its high melting point and melt viscosity make thermoplastic processing extremely difficult, so that many... 

Not all polyetherimides are limited by their tractability, however. Certain aromatic polyetherimides are characterized by a combination of properties that makes them potential engineering thermoplastics (90). One of these polymers contains an isopropylidene unit in the backbone to enhance the solubility. It is a mol ding material introduced by General Electric in 1981 and sold as Ultem resin. Attractive features include high temperature stability, flame resistance without added halogen or phosphoms, high strength, solvent resistance, hydrolytic stability, and injection moldability. 

Within the past several years, improvements in the toughening of high-temperature epoxies and other reactive thermosets, such as cyanate esters and bismaleimides, have been accomplished through the incorporation of engineering thermoplastics. Additions of poly(arylene ether ketone) or PEK and poly(aryl ether sulfone) or PES have been found to improve fracture toughness. Direct addition of these thermoplastics generally improves fracture toughness but results in decreased tensile properties and reduced chemical resistance. 

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