Agriculture Reference
In-Depth Information
Briquetting and composite technology is yet to get a strong foothold in many
developing countries because of technical constraints and the lack of knowledge for
obtaining higher efficiencies to match the end requirements. Overcoming the many
operational problems associated with this technology and ensuring the quality of
raw materials at the time of use are critical factors for determining its commercial
success. In addition to this commercial aspect, the importance of composite technology
lies in conserving wood, a commodity used in all countries extensively and which
can lead to the widespread destruction of forests. The availability of wood plastic
composites (WPC) with bio-wastes over the past few years has lessened the need for
using natural wood. Also, the arrival of polymeric composites with rice hulls (PCRH)
as ideal substitutes for natural wood with a greater range of applications will help to
ease the need for wood but on a much larger scale.
1.2 What are Composite Materials?
Composites are materials made from two or more constituent materials with
significantly different physical and chemical properties that, if combined, produce a
material with characteristics different from the individual components while remaining
separate and distinct within the structure. A composite material can also be described
as a macroscopic combination of two or more distinct materials having recognisable
interfaces between them, the properties of which can be optimised by the addition of
additives to achieve a balance of properties to meet the requirements of a given range
of applications. Composites are used not only for their superior structural strengths
but, among others, for electric, thermal, biological and environmental applications.
Composites are formed by individual materials, which may occur naturally or be
made artificially. There are two main categories of constituent materials: a matrix
and reinforcements. At least one portion of each is required to make a composite.
The matrix material surrounds and supports reinforcement materials by maintaining
their relative positions. Reinforcement materials provide the special mechanical and
physical properties to enhance the properties of the matrix. Synergism produces
material properties that are not available from the individual constituent materials,
whereas the wide variety of matrices and additives allow the designer/producer of
composite products to choose the optimum combinations and to structure them to
achieve the desired end result.
Several commercially produced composites use a polymer matrix material often called a
'resin solution'. Many natural polymers and modified polymers are available for use and
depend upon the planned composite. Selection is highly dependent upon the compatibility
of the reinforcement materials to be used. There are several broad categories, each
with numerous variations. Some of the most common polymers are polyester; vinyl
 
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