Heat deflection/distortion temperature

Heat softening and heat deflection/distortion temperatures—reference hot processing etc. 

ASTM American Standard Test Method BS British Standard CAB Cellulose acetate butyrate DGEBA Diglycidyl ether of bisphenol A DSC Differential scanning calorimetry ENR Epoxidized natural rubber EVA Ethylene-co-vinylacetate EPDM Ethylene propylene diene monomer ESC Environmental stress cracking HDT Heat deflection/distortion temperature HDPE High-density polyethylene HIPS High -impact polystyrene... 

Various thermal material properties (as opposed to thermal stability. Chapter 9) are discussed in Chapter 16. These include coefficient of expansion, melting temperature, Vicat softening point, heat deflection/distortion temperature by thermomechanical analysis, also brittleness temperature, minimum filming temperature, delamination temperature, meltflow index, heat of volatilisation, thermal conductivity, specific heat and ageing in air. 

Two particular test methods have become very widely used. They are the Vicat softening point test (VSP test) and the heat deflection temperature under load test (HDT test) (which is also widely known by the earlier name of heat distortion temperature test). In the Vicat test a sample of the plastics material is heated at a specified rate of temperature increase and the temperature is noted at which a needle of specified dimensions indents into the material a specified distance under a specified load. In the most common method (method A) a load of ION is used, the needle indentor has a cross-sectional area of 1 mm, the specified penetration distance is 1 mm and the rate of temperature rise is 50°C per hour. For details see the relevant standards (ISO 306 BS 2782 method 120 ASTM D1525 and DIN 53460). (ISO 306 describes two methods, method A with a load of ION and method B with a load of SON, each with two possible rates of temperature rise, 50°C/h and 120°C/h. This results in ISO values quoted as A50, A120, B50 or B120. Many of the results quoted in this book predate the ISO standard and unless otherwise stated may be assumed to correspond to A50.)... 

In the deflection temperature under load test (heat distortion temperature test) the temperature is noted at which a bar of material subjected to a three-point bending stress is deformed a specified amount. The load (F) applied to the sample will vary with the thickness (t) and width (tv) of the samples and is determined by the maximum stress specified at the mid-point of the beam (P) which may be either 0.45 MPa (661bf/in ) or 1.82 MPa (264Ibf/in ). 

To enhance the resistance to heat softening his-phenol A is substituted by a stiffer molecule. Conventional bis-phenol A polycarbonates have lower heat distortion temperatures (deflection temperatures under load) than some of the somewhat newer aromatic thermoplastics described in the next chapter, such as the polysulphones. In 1979 a polycarbonate in which the bis-phenol A was replaced by tetramethylbis-phenol A was test marketed. This material had a Vicat softening point of 196 C, excellent resistance to hydrolysis, excellent resistance to tracking and a low density of about l.lg/cm-. Such improvements were obtained at the expense of impact strength and resistance to stress cracking. 

Radio and television uses largely arise from the ability to produce components with a high level of dimensional accuracy coupled with good dielectric properties, high heat distortion temperatures and the availability of selfextinguishing grades. Specific uses include coil formers, picture tube deflection yokes and insert card mountings. 

Heat distortion temperature (deflection temperature under load) of cured... 

The ASTM heat distortion temperature (deflection temperature under load) test may be used to characterise a resin. Resins must, however, be compared using identical hardeners and curing conditions. 

Heat deflection temperature (HDT), 45 Heat distortion temperature (HDT), 242 Heck coupling, 489... 

TDI isomers, 210 Tear strength tests, 242-243 TEDA. See Triethylene diamine (TEDA) Telechelic oligomers, 456, 457 copolymerization of, 453-454 Telechelics, from polybutadiene, 456-459 TEM technique, 163-164 Temperature, polyamide shear modulus and, 138. See also /3-transition temperature (7)>) Brill temperature Deblocking temperatures //-transition temperature (Ty) Glass transition temperature (7) ) Heat deflection temperature (HDT) Heat distortion temperature (HDT) High-temperature entries Low-temperature entries Melting temperature (Fm) Modulu s - temperature relationship Thermal entries Tensile strength, 3, 242 TEOS. See Tetraethoxysilane (TEOS)... 

HDT heat deflection temperature under flexural load (1820 kPa) Heat distortion test (HDT) ASTM D-648-72 CEAST 6005... 

We use a variant of flexural testing to measure a sample s heat distortion temperature. In this test, we place the sample in a three point bending fixture, as shown in Fig. 8.6 b), and apply a load sufficient to generate a standard stress within it. We then ramp the temperature of the sample at a fixed rate and note the temperature at which the beam deflects by a specified amount. This test is very useful when selecting polymers for engineering applications that are used under severe conditions, such as under the hoods of automobiles or as gears in many small appliances or inside power tools where heat tends to accumulate. 

A good applications-oriented measure of the use temperature for a ma-teral is the heat distortion or heat deflection test (HDT). The HDT is described by ASTM-D648 as the temperature at which a sample of defined dimensions (5 X Vi X Vs (or Va) in.) deflects under a flexural load of 66 or 264 psi placed at its center. In case of a largely amorphous polymer, the HDT temperature is typically slightly (10 to 20 °C) lower than the Tg as determined by DSC or DTA, whereas with more-crystalline polymers, it more closely correlates with the Tm. The HDT temperature is a useful indicator of the temperature limits for structural (load-supporting) applications. A loaded cantilever beam is used in another heat deflection test called the Martens method. 

Heat-Distortion Temperature (see also Deflection Temperature Under Load)... 

Heat distortion temperature (or heat deflection temperature)... 

Heat deflection temperature (see Heat distortion temperature above)... 

Heat Deflection Temperature - The temperature at which a material specimen (standard bar) is deflected by a certain degree under specified load. Also called rensi/e heat distortion temperature, heat distortion temperature, HDT, deflection temperature under load. 

Heat Distortion Temperature (HDT) - See Heat Deflection Temperature. 

PET/elastomer blends have been used commercially either filled or reinforced. Owing to slow crystallization of PET in these blends, unfilled grades would be very difficult to mold. In warm molds, the cycle would be too long, the parts would tend to stick and distort when removed, making the process expensive. In cold molds, amorphous parts with low heat deflection temperatures, would be produced, reducing the usefulness of the blends. 

The heat distortion temperature (HDT), the deflection temperature under load (DTUL), or the softening temperature are practical and important parameters of a polymeric material. They denote... 

Two particular test methods have become very widely used. These are the Vicat softening point test and the test widely known as the heat distortion temperature test (also called the deflection temperature under load test). In the Vicat softening point test a sample of polymer is heated at a specified rate temperature increase and the temperature is noted at which a needle of specified dimensions indents into the polymer a specified distance under a specified load. 

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