Chemistry Reference
In-Depth Information
density and T
g
, even below room temperature, polymer blends of EVO
with DGEBA have been frequently applied as polymer matrices for fiber
reinforced composites (FRCs).
Some research has shown that EVOs are best limited to being minor
components in blends, i.e.,
o
30 wt% because EVO components cannot
provide the mechanical and thermal properties desired for an FRC.
61,180
Pure EVO or high EVO content (e.g., 450 wt%) polymer matrices for high-
performance composite applications are rare and better suited to non-
structural applications.
181-184
Glass fibers are one of the most widely used reinforcement materials in
epoxy composites because of their availability, low cost, high modulus, and
excellent adhesion to the matrix resin. Espinoza-Perez et al.
61
manufactured
glass-fiber-reinforced composites using a hand lay-up method. A PACM-
cured EVO commercial epoxy blend was used as the matrix. The 30 wt% EVO
blended composite thermal and mechanical performance was slightly lower
than the composites without EVO, but were comparable with those of
anhydride-cured ones.
EAS, ESO, and EMS have been applied in bio-composite manufacturing
using pultrusion processing but these epoxies were limited to being minor
components in blends, e.g.,
r
30 wt% of the epoxy blend.
185,186
Greater
mechanical properties were demonstrated for EAS than for ESO or EMS due
to an improved oxirane content and better reactivity. A further increase of
EAS content, up to 50 wt%, was also attempted. While the T
g
of the com-
posite decreased from 78 to 52 1C, the impact strength improved.
187
The
pulling force of the pultrusion manufacturing was significantly reduced due
to good lubricity provided an oily bio-based component which apparently
came from the saturated and unreactive components of EAS.
Using anhydride-cured pure EGS, a blend of EGS-DGEBA, or pure DGEBA
as the polymer matrix, glass-fiber-reinforced composites were fabricated
via vacuum-assisted resin transfer molding.
188
The EGS-based composite
showed mechanical properties comparable to that of the DGEBA counter-
parts in terms of flexural strength/modulus and impact strength. Only
a slightly reduced T
g
and thermal stability were observed. This high-
performance bio-based composite has good potential to replace petroleum-
based epoxy resins as a value-added product from VOs.
Cellulosic fibers such as flax, hemp, or jute are also promising reinforce-
ments for polymers composites due to their availability, high specific
strength, low cost, and environmental friendliness.
189
VO-based polymer
composites reinforced by cellulose are often called ''green'' composites, since
both the matrix resin and reinforcement are from bio-renewable resources.
178
However, these composites tend to have lower mechanical strengths than
similar composites reinforced with glass fibers. Due to the hydrophilic char-
acter of cellulosic fibers, surface modification is required to improve the ad-
hesion or compatibility between the cellulose and the polymer matrix.
190,191
Hemp-fiber-reinforced ELO composites were manufactured by Boquillon
192
using a hot pressing method. DMA results indicated the storage modulus
