Page 35 - New Cloth Market December 2022 Digital Edition

Industrial Hemp Fibers: An Overview

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João P. Manaia ,*, Ana T. Manaia and Lúcia Rodriges
1
Laboratory for Wear, Testing & Materials (LED&MAT),
Instituto Pedro Nunes, Rua Pedro Nunes, 3030-199 Coimbra, Portugal; Email: [email protected]
2
CITEVE, Rua Fernando Mesquita, 2785,
4760-034 Vila Nova de Famalicão, Portugal; Email: [email protected]
* Correspondence: [email protected] or [email protected]; Tel.: +351-963-128-954

Abstract: Industrial hemp (Cannabis sativa) is one of the most available and widely produced bast
fibers with high cellulose content. Interest in these fibers is warranted due to environmental protection
challenges as well as their inherent properties such as low density, high specific strength, and stiffness.
In addition, advanced research and progress have gone into increasing their mechanical performance
through surface treatments and in the development of new materials. The most promising application for
hemp fibers is as reinforcement in polymeric composites or through hybridization.

Nonetheless, more research is needed to improve their properties and expand their range of applica-
tions. The biodegradability issue is one problem that must be addressed when considering long life-
cycle applications as the reproducibility of these composites’ final properties. This review is a compre-
hensive literature review on hemp fibers. It includes hemp fibers’ chemical and mechanical properties,
surface modifications, hybrid composites, as well as current and future applications.
Keywords: hemp fibers; surface treatments; hybrid composites; mechanical properties; industrial appli-
cations

Joshi et al. [12] compared the life-cy- bers are their inherited hydrophilic char-
Introduction
cle assessment of three components acter, highly anisotropic nature, low re-
made from natural fiber-reinforced sistance to microorganisms, low ther-
Environmental protection is one of the
composites and glass fiber-reinforced mal stability, variation in mechanical
greatest challenges facing the current
composites. They found that natural properties, and mechanical properties
generation [1]. Due to increasing envi-
fiber-reinforced composites emerged lower than those of synthetic fibers [6].
ronmental concern and protection, the
more environmentally friendly, mainly Additionally, it is recognized that vari-
number of available studies dealing
for three reasons: (1) natural fiber pro- ous aspects such as growth condition,
with the potential use of natural fibers
duction had the lower environmental harvesting methods, and maturity of-
in developing thermoset and thermo-
impacts, (2) natural fiber composites ten affect natural fiber properties [11].
plastics composites as well as improv-
had higher fiber content for equivalent
ing their mechanical performance The hydrophilic character of natural fi-
performance, which reduced the vol-
through physical and chemical surface bers results in poor interfacial interac-
ume and weight of the base polymeric
treatments is growing. tion between the matrix and fiber and
matrix, and (3) the lower weight of the
poor fiber dispersion, as well as high
Furthermore, natural fibers are getting resultant components reduced the
moisture absorption, which might lead
more attention as possible alternative emissions and fuel consumption in its
to fiber swelling and debonding of the
replacements for synthetic fibers, such life cycle.
matrix-fiber interface [14,15]. The
as glass fibers [2–7].
The life-cycle assessment, performed moisture absorption in natural fiber-re-
Natural fibers are eco-friendly [8], are by La Rosa et al. [13], showed that inforced composites is governed by
non-abrasive to the processing equip- hemp mats in glass fiber-reinforced three different diffusion mechanisms,
ment, are relatively low cost, are from thermoset composites are more envi- namely, (1) water diffusion between the
renewable resources, have low densi- ronmentally friendly than the conven- polymer microcaps, (2) capillary trans-
ty, and have high specific strength and tional single use of glass fiber, due to ports into flaws and defects at the
stiffness [8,9]. the reduction of glass fiber and resin matrix-fiber interface, and (3) transpor-
content. tation through microcracks formed dur-
On average, natural fiber production
ing the fiber’s swelling process [16].
uses 60% less energy than glass fiber
While there are a wide number of ben-
production, and results in lower air This review article describes the re-
efits in using natural fibers, there are
emissions [10]. Moreover, the wastes cent research works related to various
also some disadvantages.
are mostly organic and 100% biode- aspects of hemp fibers and their use
gradable [7,11]. The major disadvantages of natural fi- in the reinforcement of composites.
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