Tuesday, 15 February 2022

Design Data for Plastics Engineering: Selected Properties of Natural Fiber Based Polymer Compounds

Hello and welcome to a new blog post. Today I present to you selected properties of natural fiber based polymer compounds as part of our design data for plastic engineering series.

Which natural fibers can be used and why to replace e-glass with them?

The use of natural fibers represents a sustainable alternative to synthetic glass and carbon fibers. They can be used in applications ranging from automotive, aeronautics to building and construction. Natural fibers can be plant, animal, and mineral based. In this post, we focus only on plant based fibers as reinforcement. The most important plant based fibers (cellulose) include cotton, flax, hemp, jute, pineapple, abaca, wood, wheat, rice, bamboo, and esparto. Among the animal fibers are lamb’s wool, goat hair, angora wool, and cashmere. Mineral fibers are fibrous brucite and wollastonite.

Recycling of glass and carbon fibers is still high energy consuming. Table 1 shows the environmental parameters (production of 1 kg of fibers [5]) of hemp and glass fibers. In all three categories, hemp fibers represent a sustainable alternative to glass fibers.

Table 1: environmental parameters (production of 1 kg of fibers [5]) of hemp and glass fibers

Properties of fibers

Before deciding to replace glass fibers with natural fibers, a look at the mechanical properties of natural fibers is important. This will later enable a better material formulation and material selection.

Figure 1 and 2 compares the mechanical properties of glass with those of jute, flax, hemp, and cotton. It can be shown that the tensile modulus of flex and hamp is with 70 GPa in the range of the glass tensile modulus.

Figure 1: Tensile strength vs. density of different natural fibers and glass fiber

Figure 2: Tensile modulus vs. density of different natural fibers and glass fiber

Properties of natural fiber reinforced plastics

For formulating plastic compounds using natural fibers, thermal processing properties must be in the suitable range of the fibers. Polyethylene (PE) and Polypropylene (PP) base polymers are good examples for such a suitability and our examples will be based on a PP copolymer.

Figure 3 presents the mechanical properties of PP based natural fiber compounds (six different fibers; always 35%) and compares them to a PP based glass fiber compound (also 35%). Within the natural fiber compounds, mechanical values are in a similar range. PP glass fiber reinforced compounds are double in tensile modulus and tensile strength.

Figure 3: Tensile modulus vs. tensile strength of different PP compounds with natural fiber reinforcement and PP with glass fiber reinforcement


Natural fiber based compounds allow a weight saving in the range of 10 -30%. Most used fibers are hemp, jute, and flax. Hemp fiber production is almost pesticide free. Additionally, hemp fibers are hydrophilic and proper drying must be done prior to compounding. In terms of performance, natural fiber compounds can be used in automotive interior applications (door panels, seat backs paneling), together with exterior applications (bumpers, spoilers). In building and construction, such compounds can be found in roof panels and insulations.

Thanks for reading and #findoutaboutplastics

Herwig Juster

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[1] WIS Polymer-Wissenmatrix; https://www.advanced-compounding.com/de/polywood-pp.html

[2] https://www.researchgate.net/figure/Mechanical-Properties-of-chemically-treated-jute-fibre-reinforced-polymer-composites_tbl6_282073854

[3] https://www.frontiersin.org/articles/10.3389/fmats.2019.00226/full#B95

[4] https://hal.archives-ouvertes.fr/hal-03153829/document

[5] Shahzad, 2011: https://journals.sagepub.com/doi/10.1177/0021998311413623

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