Research Progress and Application of Natural Fiber Composites

Figures & data

Table 1. Statistics on consumption of natural fiber composites in major regions of the world from 2018 to 2021. Adapted and reproduced with permission from the ref (Beijing Yubo Zhiye Market Consulting Co., Ltd 2022).

Year	Consumption（ten thousand ton）
	North America	Europe	China	Japan	Southeast Asia	India
2018	156.4	80.6	83.2	39.8	32.5	30.1
2019	171.5	88.5	94.2	43.3	37.2	34.2
2020	181.2	93.9	104.1	45.6	41.1	37.5
2021	197.5	102.5	117.2	49.3	47.4	42.6

Table 2. Forecast of consumption of natural fiber composites in major regions of the world from 2022 to 2026. Adapted and reproduced with permission from the ref (Beijing Yubo Zhiye Market Consulting Co., Ltd 2022).

Year	Consumption（ten thousand ton）
	North America	Europe	China	Japan	Southeast Asia	India
2022	214.3	111.4	130.9	53.0	55.2	48.4
2023	233.0	121.4	148.4	57.1	64.4	55.8
2024	252.5	131.8	167.1	61.1	74.0	63.4
2025	271.7	141.5	184.4	65.3	83.3	71.4
2026	290.2	151.4	200.0	69.5	93.3	78.8

Figure 1. Number of articles published in the field of natural fiber composites in the past 20 years.

Figure 2. Relationship between fiber length and mechanical properties of glass fiber reinforced polypropylene composites. Adapted and reproduced with permission from the ref (Thomason 2002).

Figure 3. Principle of the foaming process. Adapted and reproduced with permission from the ref (Villamil Jiménez et al. 2020).

Table 3. Modification methods and effects of polyelectrolytes on natural cellulosic fibers. Adapted and reproduced with permission from the ref (Sun et al. 2022).

Fiber Type	Treatment Methods	Process Conditions	Modification Effects
Wood (Liriodendron tulipifera)	Immersive assembly	Polydiallyldimethylammonium chloride (PDDA) and montmorillonite (MMT) clay were used. The concentration of PDDA solution was about 0.5 wt%, the concentration of MMT was about 0.05 wt%, NaCl 0.5 M. PDDA treatment time was 20 min, and the pH was 10.5.	The surface of the fiber was covered with nanoscale PDDA-clay films, and the heat resistance of the fibers improved.
Wood	Immersive assembly	Poly(allylamine hydrochloride) (PAH) and Polyacrylic acid (PAA) were used, the addition amount was 30 mg/g fiber, NaCl 0.01 M, and the treatment time was 20 min. PAH and PAA were adsorbed at pH values of 7.5 and 3.5, respectively.	The water resistance of the fiber improved, and paper sheets from modified fibers showed improved mechanical properties.
Wood	Immersive assembly	Chitosan (CH) and poly (vinylphosphonic acid) (PVPA) were used. The addition amount was 10 mg/g fiber. The concentration of both solutions was 0.1 wt %, NaCl 0.01 M. The treatment time was 10 min, and the pH was 4.	The flame retardant effect improved, the phosphorus-containing thin films (20 CH/PVPA bilayers) reduced the peak heat release rate by 49%.
Wood	Immersive assembly	PAH and PAA were used. The addition amount was 30 mg/g fiber, NaCl 0.01 M, and the treatment time was 20 min (1) PAH at pH 7.5 and PAA at pH 7.5 and (2) PAH at pH 7.5 and PAA at pH 3.5.	The tensile properties of paper increased with the number of modified layers. The bonding force between fibers was also strengthened.
Wood	Immersive assembly	PAH and Poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were used. The concentration of both solutions was 0.0025 wt%. The addition amount was 5 mg/g fiber, NaCl 0.01 M, and the treatment time was 10 min. PAH and PEDOT:PSS were adsorbed at pH values of 7.5 and 3.5,respectively.	The conductivity of fiber and paper improved. The modified fibers had a much smoother surface.
Wood	Immersive assembly	PAH and Lignosulfonates-amine (LSA) were used. The concentration of PAH solution was 0.01 wt%, and the pH was 7.5. The concentration of LSA was 0.02 wt%, the pH was 12, and the treatment time was 15 min.	The water resistance of the fiber improved, and paper sheets from modified fibers showed improved mechanical properties.
Wood	Immersive assembly	Polyethylenimine (PEI) and Sodium hexametaphosphate (SHMP) were used. The addition amount was 30 mg/g fiber, NaCl 0.01 M. The treatment time was 30 min, with pH 9 for PEI, and pH 4 for SHMP.	The flammable character of wood fibers was reduced while the mechanical properties of the paper material were strengthened.
Wood	Immersive assembly	PEI, PSS and indium tin oxide (ITO) nanoparticles were used, and the concentrations of the three solutions were 0.2 wt%, 0.01 wt% and 0.01 wt%, respectively. The pH values were 6.5, 7.0 and 3.0 respectively. The treatment time was 20 min.	The conductivity of fiber and paper improved. The conductivity of coated paper improved by more than six orders of magnitude in both thein-plane and through-the-thickness directions.
Cotton	Immersive assembly	Branched PEI (pH 7 or 10) and MMT clay(0.2 or 1 wt %) were used. The PEI solution concentration was 0.1 wt %，The first dip into each mixture was for 5 min,and subsequent dips were for 2 min each.	This process could carry out flame-retardant treatment on cotton fiber fabrics, and improve the heat resistance to a certain extent without effects on the characteristics of fiber fabrics.
Cotton	Immersive assembly, Spray assembly	Positive alumina-coated silica and negativesilica nanoparticles were used. The concentration of both solutions was 0.2 wt %. The treatment time was 5 min, and the spray gun distance 6 cm.	The horizontal spray showed a very homogeneous silica coating when compared to vertical spray or dipping. A better flame retardant effect was achieved.
Cotton	Spray assembly	Graphene and vinylphosphonic acid were used. The concentrations of the graphene solutions were 1 wt% and 2 wt%, the concentration of the vinylphosphonic acid solution was 3 wt%, and the treatment time was 10 s.	This process could improve hydrophobicity, thermal stability, electrical conductivity, UV absorption and EMI shielding.
Cotton	Immersive assembly	CH and alginic acid sodium salt were used. The concentration of both solutions was 0.1 wt %, the pH was 5, and the treatment time was 5 min.	The surface water resistance and dyeability of the fiber could be accurately adjusted. Moreover, the treated fiber had potent antibacterial activity toward both Gram-positive and Gram-negativebacteria.
Cotton	Immersive assembly	CH and PEDOT:PSS/Graphene were used. The solution of CH was 3 wt%, PEDOT: PSS solution was 1 wt% PEDOT and 0.5 wt% PSS. The treatment time was 20 min.	This process couldimprove electrical conductivity，UV protection ability and laundering durability.
Cotton	Immersive assembly	PEI/melamine, and phytic acid were used, the concentration of PEI/melamine was 0.5 wt% and 3 wt%, the concentration of phytic acid was 3 wt%, the pH value of both solutions was 4, and the treatment time was 2 min.	This process could improve the flame retardancy and water repellency.The peak heat release rates decreased by more than 50%.
Cotton	Immersive assembly	CH, and pentasodiumtripolyphosphate and PSS were used, the solution concentration was 1 wt%, and the treatment time was 5 min.	The bacterial resistance of the fiber improved, and the water resistance could be precisely controlled. The air-permeability was reduced.
Ramie	Immersive assembly	Ammonium polyphosphate (APP) and PEI were used, the concentrations of both solutions were 0.4 and 0.9 wt %, the pH was 9, and the treatment time was 2 min	The specific surface area decreased with the number of deposited layers. The flame retardancy of the fiber improved.
Ramie	Immersive assembly, Spray assembly	APP and PEI were used, the concentration of both solutions was 0.9 wt%, the pH was 9, and the treatment time of Immersive process was 2 min. The spray gun distance was 55 cm.	The heat resistance of the fibers treated by the two methods improved, and the spray assembly had a better flame retardant modification effect than the immersive assembly.
Bagasse (Saccharum officinarum)	Immersive assembly	APP and CH were used, the concentration of both solutions was 0.5 wt%, and the treatment time was 10 min. The pH of chitosan solution was 3.5.	The flame retardant effect improved. The peak heat release rate and total heat release decreased by 64.6% and 13.2%, respectively after six-layermodification.
Sisal	Immersive assembly	CH and MMT were used, the concentration of CH solution was 0.2 wt %, the treatment time was 10 min, the concentration of MMT solution was about 0.5 wt %, and the treatment time was 30 min.	This process could significantly improve the flame retardant performance.
Rice (Oryza sativa)	Immersive assembly	The branched PEI and PAA were used. The concentration of the PEI solution was 0.5 wt %, the pH was 10, the concentration of PAA was 1 wt %, the pH was 3, and the treatment time was 3 min.	The heat resistance improved, and the mechanical properties of the prepared composite plates greatly improved.
Cellulose nanofibril	Immersive assembly	Branched PEI and PVPA were used, and the solution concentration was 0.1 wt%	This process could improve self-extinguishing and intumescent properties，not hamper optical transparency of the nanopapers.

Figure 4. Preparation of aligned nanofibers. Reproduced with permission from the ref (Zhu et al. 2020).

Figure 5. The production of 3D-printable continuous flax fiber reinforced plastic prepreg filaments. Adapted and reproduced with permission from the ref (Zhang et al. 2020).

Figure 6. Schematic diagram of multiscale modeling for mechanical properties of natural fiber. Adapted and reproduced with permission from the ref (Sun et al. 2014).

Figure 7. Wood fiber membrane with high strength and ionic conductivity. Reproduced with permission from the ref (Chen G. et al. 2019).

Beijing Yubo Zhiye Market Consulting Co., Ltd. 2022. Research report on the development status and investment prospects of natural fiber reinforced polymer composite industry in the world and China (2022-2026).

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