Biomedical Engineering Reference
In-Depth Information
materials and their products started early, and there is a wide range of industrial
application examples. In China, the National University of Defense Technology,
Sun Yat-sen University, Northwest Textile Institute, and so on have performed
research on hemp fiber-reinforced polyurethane and unsaturated polyester resin but
have not seen industrial applications. The heterogeneity of natural fibers and their
incompatibility with organic synthetic polymer limit their application in the field of
composite materials. Natural fiber can be effectively modified by surface treatment,
graft copolymerization, and the interface coupling methods to improve combination
with the polymer resin. In recent years, India and China's Sun Yat-sen University
studied the impact of alkalization, acetylation, and cyanoethylated modification of
mechanical properties and electrical properties of sisal and epoxy composites. The
National University of Defense Technology researched the mechanical properties
of epoxy composites reinforced with jute fiber (cloth) compared with glass fiber-
reinforced resin composites and explored the application of hemp fiber-reinforced
resin composites. Natural fiber-reinforced amino resin is a thermosetting plastic
with excellent electrical insulating properties, heat resistance, and flame resistance
and good mechanical strength; thus, it has been considered a superior alternative for
synthetic plastics in a certain range.
Processing technologies for polymer plastics include molding, extrusion, blow
molding, injection molding, and so on. Usually, synthetic polymer material has
a relatively regular molecular structure and morphology. But, the structures of
lignocellulose and other natural polymers are often affected by the source of
raw material, season, geography, and so on, leading to complex and changeable
processing performance. Lignocellulose polymer materials must be modified before
universal molding, extrusion, blow molding, injection molding, and other process-
ing to improve plasticity, rheology, and liquidity.
Microcellular foam technology in recent years has developed from the
single-polymer foam to composite microcellular foam, but research on biomass
fiber/plastic composite foam started relatively late. At present, the majority of
foaming biomass fiber/plastic composite is PVC-based WPC materials, mainly
utilizing the extrusion foaming process. The foaming process for biomass
fiber/plastic composites is basically divided into two categories according to
foaming method: physical foaming and chemical foaming. Development of biomass
fiber/plastic composites is the result of increasing environmental issues. The wide
range of sources of raw materials, cheap production costs, increasingly improved
performance, and environmental friendliness make these the preferred alternatives
to wood and plastic, and they will play a broader role in more areas.
The overall structural modification (fractionation) of the straw can improve
the plastic nature of the straw materials and the compatibility of straw-modified
materials and the plastic compound, which is expected to improve the dosage of
straw and reduce the cost of WPC production.
