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Mechanical (tensile and compressive properties, heat distortion, pressure-velocity limit,
toughness, stress rupture resistance, creep resistance)
Dimensional considering manufacturing conditions (manufacturing tolerances,
stability, available sizes, moldability, surface texture)
In order to illustrate the importance of polymer materials' idiosyncrasies (Budinski &
Budinski, 2010), each group of followed properties should be described. Physical properties
are material characteristics that pertain to the interaction of these materials with various
forms of energy and human senses. Generally they could be measured without destroying
the material. Density is a physical property determined with weighting or measuring the
volume of the product. Physical properties like feel and colour are even easier to determine
while they affect the customer as he or she only looks at it. Nevertheless, they are not
marginal material properties and their importance rises in today's consumer oriented
society. The designer has to acknowledge that plastic feels different from metal and yellow
is happier colour in comparison to brown.
Chemical properties are related to the structure of polymer material, its formation from the
elements of which the material is made, its reactivity with chemicals and environments.
These properties cannot be visually inspected and are measurable in chemical laboratory.
Mechanical properties are the features of material, which are put on view when it is exposed
to a force. They are related to the elastic or plastic behaviour of the polymer and they often
require destruction for measurement. Term mechanical is used because they are usually
used to indicate the suitability of the material for use in mechanical applications - parts that
carry a load, absorb shock, resist wear, etc.
Dimensional properties include as well manufacturing considerations like manufacturing
tolerances and moldability. This category concerns also the surface texture and its
roughness, which is measurable and essential for many applications. Available size,
shape, finish and tolerances of the product are also important polymer material selection
factors.
4.3 Material selection program packages
Regardless of the material selection method used in design process the designers and
experts all should choose eventually from the broad list of materials in catalogues from
several material suppliers or they can use the web or computer programs for easier
material selection. Plastic material selection web programs like CAMPUS offer some
comparison of plastic materials' properties for one or more suppliers. User can observe
the relations between several property types like rheological, mechanical, thermal,
processing, etc., where each type has some specific single value technical parameters
introduced along with multi-joint graphical data at disposal. Although, the value of such
computer tool for the engineer and design process is unequivocal, the plastic material
selection support is limited. Firstly, the potential selected polymers - candidates are
ranked according to some of basic properties, where maximum and minimum values are
defined by the user. Depending on designer's skills to do so, the system offers from zero
to hundreds of candidates, which meet the requirements. If the number of candidates is
large, he or she has to define the values tightly and vice-versa, if there are no suggestions.
Due to unambiguous ranking the user receives systematically acquired candidates. Thus,
it could be misleading for the inexperienced designer as he or she could overlook the
crucial parameters like time and temperature dependence of properties. In addition,
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