abstract
In this study, composites were fabricated with four types of pulp fibers and two types of thermoset polymers.
Four pulp fibers included hardwood and softwood high-yield pulp (HYP), Kraft pulp, and Whatman
cellulose fibers and two polymers included unsaturated polyester (UPE) and vinyl ester (VE). FTIR and
TGA results showed the chemical differences among the four pulp fibers and confirmed the existence
of lignin on the HYP pulp fibers. The two HYP fibers were more compatible to the UPE resin, while the
Kraft and Whatman cellulose fibers were more compatible to the VE resin as indicated by the tensile
properties. Lignin on the two HYP fibers acted as a natural coupling agent for the natural fiber and the
more hydrophobic UPE resin. The two cellulose-rich pulp fibers performed better when the VE resin
was used. Composite storage moduli were significantly improved as compared with those of the neat
UPE and VE resins. Only a slight increase in glass transition temperature was noted for the composites