Page 38 - New Cloth Market December 2022 Digital Edition

Industrial Hemp Fibers: An Overview

single hemp fiber (mean fiber width of proach to product making [46]. Wam-
Thermoplastic and Thermoset
67 ± 26 µm) was 277 ± 191 MPa, as bua et al. [47] tested and compared
Polymeric Matrices
well as a tensile modulus and a strain the mechanical properties of sisal,
to failure of 9.5 ± 5.8 GPa and 2.3 ± kenaf, hemp, jute, coir fibers, and glass The role of the matrix is to protect the
0.8%, respectively. fiber-reinforced polypropylene compos- fibers from the environment and pack
ites. The composites reinforced with them in a fixed arrangement, transfer
Hemp Fiber-Reinforced
hemp fibers displayed the highest (52 the loads to the fibers, as well as gov-
Composites
MPa) tensile strength, whereas the coir ern the composite shape and surface
When two or more different materials composites displayed higher impact appearance [45]. The properties of the
are combined in order to produce a new strength. Some specific properties of matrix will also determine the maxi-
engineered material, they are called hemp fiber composites were found mum service temperature, moisture
composite materials. In general, this comparable to those of glass fiber. The and chemical resistance, and thermal
refers to a matrix material which is re- advantages and disadvantages of stability. The most common matrices
inforced with fibers [45]. The mechani- hemp fiber composites are summa- currently used in hemp fiber compos-
cal properties of composite materials, rized in Table 3 [19]. ites are polymeric, both thermoplastic
depend on the dispersion and distribu- and thermoset, as they are light weight
tion of reinforcements, the interfacial Long-term performance or durability is and can be processed at low tempera-
adhesion between matrix and reinforce- one of the major concerns to be con- ture [20]. Table 4 presents the proper-
ments, the material’s mechanical prop- sidered for hemp fiber-reinforced com- ties of thermoplastic and thermoset
erties, the fiber surface modification, posites in outdoor applications. Weath- polymeric matrices used for hemp fi-
the fiber dimension and orientation, ering conditions such as humidity, tem- bers [23].
volume fractions, and test conditions perature, and UV radiation impact ad- Thermoplastic Matrices
[6,8]. versely on the service life of the com-
posite. Both linear and branched polymers are
Hemp fibers have been used to rein-
thermoplastic, which means that they
force materials for more than 1000 In addition to that, under constant
can be melted or softened and revers-
years [1]. Low prices and the steadily stress, hemp fiber-reinforced compos-
ibly hardened as a function of temper-
increasing performance of technical ites are more vulnerable to creep than
ature [50]. Natural fibers generally have
and standard plastics have resulted in glass fiber-reinforced composites.
a higher modulus than thermoplastics,
a renewed interest in hemp fibers. Cur- These factors hinder the acceptance
thus the combination of both may re-
rently, the interest in hemp fiber com- of hemp composite products industri-
sult in a higher modulus [51].
posites is growing both in terms of their ally. To overcome the detrimental ef-
industrial applications and fundamen- fects of weathering conditions, the Melt compounding and melt pressing
tal research as they have the potential properties of hemp fiber composites are the processing techniques used the
to replace synthetic fibers as reinforce- are usually enhanced by using coupling most for hemp fiber composites. The
ment materials at a lower cost and with agents, UV absorbers, etc., during the melt compounding processing tech-
a better environmentally friendly ap- manufacturing process [48]. nique includes a single- or twin-screw

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