Basic Technology of Plastics - Introduction to Polymeric Composites with Rice Hulls - page 21

All of these properties are important in the general processing of plastics, but I will
present information only on the properties that are relevant to the subject under the
presentation polymeric composites .
2.3.1 Compatibility of Material Properties
In the design and production of composites, material compatibility is the most
important aspect for a successful end product, and is dependent largely on the
compatibility of the materials being used. Testing of materials is a specialised area,
and the average producer of composites cannot engage in this area of activity because
it takes good knowledge, experience and equipment to do so. However, a producer
of composites can make use of the many databanks available and base the design
of the intended composite on this information. For a producer already in business,
these databanks will be of immense value to sustain good-quality production and to
improve the products already being made.
For the beginner, a basic knowledge of composites would help greatly, and these
databanks will be a base upon which a producer can experiment and finalise the
composite formula. Some of the important basic properties required for compatibility
are: specific gravity; density; water absorption; melt flow; tensile strength; flexural
properties; softening temperature; and coefficient of thermal expansion.
2.3.2 Mechanical Properties
Polymeric materials are used in various designs of composites because of their low cost,
easy processing ability and desirable material properties. Mechanical considerations
for designing include: fatigue; tensile strength, flexural strength, impact, compressive
strength, hardness, damping, cold flow, thermal expansion, and dimensional stability.
Composites that need dimensional stability necessitate careful selection of materials
(though fillers will improve the dimensional stability of most plastics). A factor often
used for the evaluation and selection of materials is the strength:mass ratio (i.e., the
ratio of tensile strength to the density of the material). End applications may require
a minimum safety factor (also called a 'design factor').
2.3.3 Friction and Wear
Friction can be defined as the resistance that two surfaces generate as they slide
(or try to slide) over each other. Friction can be between dry surfaces or lubricated