Softening point definition

Vicat hardness It is a determination of the softening point for TPs that have no definite melting point. The softening point is taken the temperature at which the specimen is usually penetrated to a depth of 1 mm2 (0.0015 in2) circular or square cross section, under a 1,000 g load. 

Nytril fiber n. A manufactured fiber containing at least 85% by weight of a long chain polymer of vinylidene dinitrile [-CH2-C (CN)2-] and having the vinylidene dinitrile group in no less than every other unit in the polymer chain (FTC definition). Nytril fibers have a low softening point so they are most commonly used in articles that do not require pressing such as sweaters and pile fabrics. They are also blended with wool to improve shrink resistance and shape retention. 

Vicat softening point The Vicat softening point is a standard test for measuring the temperature at which a thermoplastic will soften. Thus it is useful to characterize polymers that have no definite melting point. 

Vicat Softening Point n The temperature at which a fiatnosed needle of 1-mm circular cross section penetrates a thermoplastic specimen to a depth of 1 mm under a specified load using a uniform rate of temperature rise (www.astm.org). This test is used for thermoplastics such as vinyls, polystyrene, acrylic, and cellulosics that have no definite melting ranges. 

In many cases, the value of PE is considered as -21 °C. Actual values may be observed between -120 and -20 °C depending on the frequency/heating rate. In the case of copolymers, is strongly dependent on comonomer content. For example, ethylene-vinyl acetate (EVA) copolymers with -50% VA content exhibit T values of -109 °C, while for a VA content of 10-20%, has values between -32 and -10 °C. T ie Vicat softening point (see Section 3.4.5 for definition) is 95 °C for LDPE and 120 °C for HDPE. 

The polymerization of diphenyldiacetylene in the presence of vanadyl acetyl-acetonate and triethylaluminum gave an open-chain polymer 10) [13]. However, when tri(isobutyl)aluminum and titanium tetrachloride were used to catalyze polymerization of [11], the product was postulated to contain another type of repeat unit [14] 35). The soluble product from the latter polymerization possessed a cryoscopic molecular weight of 1270 and a softening point of 255°-260°C. It also had good heat resistance, losing only 3% of its weight after 6 hours at 250°C in argon. Definite catalytic activity toward the decomposition of nitrous oxide was exhibited by this product [12,14]. 

There are one or two exceptions to this rule, however, such as glass and pitch. These substances remain soft for a considerable interval of temperature, becoming less and less viscous as the temperature rises, until they ultimately hquefy. This property is peculiar to so-called amorphous, i.e. non-crystalline, bodies. We shall exclude bodies of this kind from consideration, and also hquid crystals and crystalhne fiuids, substances which appear to combine the characteristic properties of the sofid and of the hquid states. They have the fixed configuration of the molecules in space peculiar to sohds, as well as the mobihty of liquids. The transition from an anisotropic crystal to a perfectly isotropic fluid always takes place at one definite temperature. The softening of crystals in the neighbourhood of the melting point is not an exception to this rule, since these softened crystals are still anisotropic. 

Tend to soften gradually upon heating and have no definite melting point Contain chains of various lengths mixed together... 

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