REINFORCEMENTS
Roving
Roving is made up of fiberglass unidirectional filaments, which are
manufactured in continuous rolls. Roving is always present in
pultruded products comprising 50% to 70% of the total glass content.
In addition to supplying the necessary strength to pull the profile,
roving supplies the product with high tensile, flexural properties
and is a big contributor to the overall section stiffness.
Generally, fiberglass roving is used in pultrusion to achieve the
required properties. In special structural applications where more
stiffness is required, graphite roving can be used. Conversely,
polyester roving may be used in applications where more flex is
needed.
Mat
Continuous strand mat is the remainder of glass reinforcement used
in the pultrusion process. Typically, it is 30%-50% of the total
glass content. Unlike hand-laid-up or press-molded processes that
use short chopped fibers, the pultrusion process must have a
multidirectional mat that has good pull strength to facilitate
getting it to the die after it has been wet-out with the resin. This
continuous strand mat is designed specifically for the pultrusion
process and offers good wet-out characteristics, conformability to a
variety of shapes, and good physical properties including the
required pull strength.
Generally, fiberglass continuous strand mat is used to obtain the
desired transverse properties of the product. Whereas the roving
ties the composite together in the longitudinal direction, the mat
is responsible for tying the composite together in all directions,
but mainly in the transverse direction. Although continuous strand
mat is suitable for most applications, a variety of products such as
woven roving, stitched roving, and woven fabrics can be used in
custom applications to increase the desired transverse properties.
Veil
Veils are used to enhance the surface of pultruded profiles. Most
widely used today are synthetic veils. A veil is added to the
outside of a profile just prior to entrance of the die. As a result,
the finished profile has a resin-rich surface that aids in
resistance to ultraviolet (UV) degradation and makes the profile
more hand-friendly. Since the veil brings more resin to the surface
and the resin is the ingredient that gives the corrosion resistance,
adding the veil increases the corrosion resistance.
All standard structural shapes are manufactured using a surface veil
as well as UV inhibitors to protect against UV degradation.
RESIN SYSTEMS
Generally, two types of resins are most often used in the pultrusion
process. They are isophthalic polyester resin and vinylester resin.
Each resin is available in a fire retardant version as well as
non-fire retardant. In selecting the proper resin, one must consider
the environment in which the product will be used. Generally,
polyester resin will be adequate to handle most environments.
However, the vinylester will handle the more severe applications
where better chemical resistance is needed. It is a good idea to
check the resin corrosion guide for proper selection of system.
Standard structural shapes are stocked in three series: standard
polyester, fire retardant polyester and fire retardant vinylester
resin systems.
Standard Polyester (ST) Resin System
Standard structural shapes are manufactured using isophthalic
polyester resin. This resin system is olive green in color and
contains UV inhibitors. Polyester resin exhibits good corrosion
resistance, good dielectric properties, low thermal conductivity,
and excellent mechanical properties.
Fire Retardant Polyester (FR) Resin System
This resin system exhibits the same characteristics as standard
polyester along with a fire retardant rating of 25 or less when
tested in accordance with ASTM E-84 and exhibits low smoke
generation. Products manufactured using this resin system are gray
and yellow in color.
Fire Retardant Vinylester (VE) Resin System
Being fire retardant, this resin meets a rating of 25 or less when
tested per ASTM E-84 and has low smoke generation. It is produced in
beige and yellow. This system exhibits excellent corrosion
resistance and is capable of higher service temperatures than
polyester resin systems.
Generally, these resin systems cover most applications, and can be
custom mixed to meet more stringent requirements for a specific
application.
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