VICAT Method

The Vicat method measures the temperature at which an arbitrary determination or a specified needle penetration (Vicat) occurs when polymers are subjected to a standardised set of testing conditions. This property can also be measured by using TMA [plots of temperature versus compression (mm)]. 

An additional way of gaining a first impression as to the short-term temperature behavior of a plastic is to determine its heat distortion temperature. The two most important standardized methods are the Vicat method (ISO 306) [16] and ISO 75. The heat distortion temperature determined by these methods is not a generally valid material property, but a parameter defined by special test conditions. Heat distortion temperatures may therefore differ significantly. Because the test conditions can hardly be transferred to service conditions, the test results only provide the designer with a rough frame of reference for selecting a material. In no case should the heat distortion temperature be regarded as maximum operational temperatures. 

The dimensional stability of a plastic when exposed to heat is another crucial property. The Vicat method of determining a plastic s softening point and the heat deflection temperature (HDT) method are two ways of rapidly determining which polymers have suitable characteristic values. In both methods the test specimens are heated under defined load with a certain heating rate while deformation is measured. Vicat softening temperature and HDT are each defined as the temperatures at which deformation reaches a given value [8]. 

Glass-transition temperatures are commonly determined by differential scanning calorimetry or dynamic mechanical analysis. Many reported values have been measured by dilatometric methods however, methods based on the torsional pendulum, strain gauge, and refractivity also give results which are ia good agreement. Vicat temperature and britde poiat yield only approximate transition temperature values but are useful because of the simplicity of measurement. The reported T values for a large number of polymers may be found ia References 5, 6, 12, and 13. 

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.)... 

Vicat softening point ( C) ASTM D1525 (DSC method) 39 52 66... 

The most widely used method is that of Vicat in which a blunt steel needle (area of point 1 mm ) is applied vertically to the surface of a test piece (about 1 cm and 3-4 mm thick) under a load of 49 N. The oven temperature is then raised at 50 °C/h and the temperature determined at which the needle has simk 1 mm into the test piece this is taken as the softening point (Vicat temperature). 

ASTM D 1525-87 Standard Test Method for Vicat Softening Temperature of Plastics, 3 pp (DOD Adopted) (FSC 9330) (MR) (Comm D-20)... 

Covers the determination of the temperature at which a specified needle penetration occurs when specimens are subjected to specified test conditions. The method is useful for many thermoplastic materials. The specimen and needle are heated at either of two permissable rates. The temperature at which the needle has penetrated to a depth of 1 mm is the Vicat softening temperature. 

The Vicat needle method consists of determining the temperature at which a 1-mm penetration of a needle (having a point with an area of 1 mm) occurs on a standard sample (0.32 cm thick with a minimum width of 1.8 cm) at a specified heating rate (often 50 °C/h) under specific stress (generally less than 1 kg). This determination is related to the heat deflection point. 

BS 27X2. Methods I20A. B. D. E. IX-tcrmination of Vicat softening temperature of thermoplastics. 1990. 

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. 

Vicat softening K ASTM D1525, ring and ball method ... 

Vicat softening point, method B K ASTM D1525 Rate B 492 (12)... 

The Vicat temperature measures the penetration of a needle into a sample under otherwise constant conditions. Thus, the method also measures elasticity and surface hardness. 

The methods of determining Martens number and Vicat and heat... 

Several methods were applied in the studies of rheological properties of paste those based on the acoustic wave velocity, as well as on the measurements of resistance against the force in of penetrator (similar to Vicat apparatus for setting time measurements), also based on the pressure transfer in the paste and different rotation methods with spindle and finally viscometers with co-axial cylinders [5]. 

ASTM. Standard test method for time of setting of hydraulic cement by Vicat needle. ASTM standards. 2002 C191-01a 1-6. 

The Vicat softening temperature (VST) is the temperature (in °C), at which an indentation tip has penetrated 1 mm deep into the test specimen surface. The indentation tip has a circular cross-section area of 1 mm. The testing method is standardized in ISO 306. It defines four different methods by varying heating rate (50 K h and 120 K h ) and load (A 10 N and B 50 N). The most common method is the B50-method (50 N and 50 K h ). The specimens have to be plane and parallel with a thickness between 3 mm and 6.5 mm and a minimum diameter resp. edge length of 10 mm (Fig. 3.5). 

ASTM D1525-06 Standard Test Method for Vicat Softening Temperature of Plasties... 

The Vicat softening temperature (VST) is standardized in ISO 306 and ASTM D 1525. It is very useful as a quality control or development tool (ASTM D1525-2009). (This test method is technically equivalent to ISO 306 1987(E)). The result is a measure of the temperature at which thermoplastics begin to rapidly soften. VST describes the temperature at which a circular indenter with a cross section of 1 mm under a standardized loading of 10 N or 50 N penetrates exactly 1 mm into the specimen. VST was introduced to measurement technology as a substitute value for melting point. VST for some common polymers are presented in Table 10.20. 

Polyethylene compositions with improved Vicat softening point Vicat softening point A method of selecting materials for polyethylene with improved Vicat softening point has been disclosed Davis 2008... 

Taj2(, Vicat softening point, HK - ball pan hardness method. 

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