Hemp-based lignocellulosic mass as a basis for producing textile fibers.

The research investigates the thermal behavior of mixed systems based on natural and artificial cellulose fibers used as precursors for carbon nonwoven materials. Flax and hemp fibers were employed as natural components; they were first chemically treated to remove impurities and enriched with alpha-cellulose. The structure, chemical composition, and mechanical properties of both natural and viscose fibers were studied. It was shown that fiber properties depend on the fiber production process history; natural fibers are characterized by a high content of impurities and exhibit high strength characteristics, whereas viscose fibers have greater deformation properties. The thermal behavior of blended compositions was investigated using TGA and DSC methods across a wide range of component ratios. Carbon yield values at 1000 °C were found to be lower for blended systems containing 10-40% by weight of bast fibers, with carbon yield increasing as the quantity of natural fibers increased. Thus, the composition of the cellulose composite affects carbon yield and thermal processes in the system. Using the Kissinger method, data were obtained on the value of the activation energy of thermal decomposition for various cellulose and composite systems. It was found that natural fiber systems have three-times higher activation energy than viscose fiber systems, indicating their greater thermal stability. Blends of natural and artificial fibers combine the benefits of both precursors, enabling the deliberate regulation of thermal behavior and carbon material yield. This approach opens up prospects for the creation of functional carbon materials used in various high-tech areas, including thermal insulation.

In this research, the physical and mechanical properties of cement-based mortars reinforced with hemp, flax and polypropylene fibres, exposed to accelerated aging of wet/dry cycles, were studied and compared with their initial properties, prior aging. The mortar mixture was made with Portland cement as a binder, cement/sand/water ratio of 1:1:0.4 by weight and with sand of particle size between 0.4-0.8mm. As fibre reinforcement short hemp, flax and polypropylene fibres with dosage of 1,0 vol% (volume ratio) within the matrix was used. The results show that both the density and compressive strength of all composites increased after accelerated aging. The highest density increase was observed by hemp fibre mortars (up to 11.6%) whereas the highest increase in compression strength exhibited flax fibre reinforced mortars (up to 57.97%). When exposed to accelerated aging of wet/dry cycles, all mortars loss their initial flexural strength, however the lowest loss was observed by natural fibre reinforced mortars. Generally, the addition of fibre reinforcement significantly increases the energy consumption capacity under flexure of plain mortars (in case of hemp fibres even by 348%). However, under accelerated aging all composites exhibit a significant loss in their energy consumption capacity under flexure.

In the development of a sustainable economy more and more emphasis is put on the development of new materials based on natural resources. Hemp fibers are one of the most environmentally friendly natural fibers with high tensile strength, retained moisture strength and other properties that make them suitable for a wide variety of industrial products. The advantage of extracting hemp fibers is that it is possible to use all parts of the plant at the same time for the production of different products -hemp seeds, their shells, hemp shives, thus maximizing the value added of this resource (the concept of sustainable development). Industrial production based on non-renewable resources, increasing demand in the consumer sphere, rapidly growing population and density puts increasing pressure on planetary resources. In this research project a biodegradable composite material is made from hemp fiber and polylactide (polymerized corn starch). Thermoset treated polylactic and hemp fiber bio-composites have high mechanical properties, which allow to reduce the amount of materials in the product. The developed bio-composite can be used both as a slab material and for molded parts of furniture, etc. In this study 3 samples of bio-composite materials with different proportion of hemp fibres in the PLA matrix were compared and their water absorption was investigated. Bio-composite hemp and polylactide (PLA) fibres were evenly blended using the carding technology. The obtained blanks were treated for thermosetting at a fixed temperature of 180 o C and a pressure of 100 kN, as well as controlled heating, compression and cooling time was applied. Bio-composite samples were tested following the water absorption standard LVS EN ISO 62:2008. Obtained material is biodegradable during the composting process, which improves the ecological assessment (Life Cycle Assessment) of the product and reduces the environmental impact. Annually renewable hemp fiber resource has the potential to create new products and develop the hemp industry in Latvia.

In recent years there has been a substantial growth in the use of natural fiber reinforced composite in more advanced applications. However, high strength applications require high mechanical properties. Hybridization of natural fibers with synthetic fibers is an effective method of increasing the field of application and mechanical properties. The effects of hybridizing hemp (Cannabis sativa L.) fiber with recycled-carbon fiber were investigated in this study to determine the trends in mechanical properties resulting from varied weight fractions. Characterization of void content was accomplished using micro computed tomography (micro-CT). Through hybridizing hemp fiber and recycled carbon fiber in a polypropylene thermoplastic, a new class of high performance, low cost composites were demonstrated for injection molding applications. This study showcased a 10–15% increase in tensile strength after the reinforcement of recycled-carbon fiber with hemp fiber. A 30–35% increase was observed in the flexure strength after the reinforcement of recycled-carbon fiber with hemp fiber. Impact strength also had an increase of 35–40% for hemp fiber reinforced recycled-carbon fiber polypropylene composites.

Characteristics of sandy soil treated using EICP-based urease enzymatic acceleration method and natural hemp fibers

The alkali treatment is aimed to modify the surface chemistry of natural plant fibres effectively through several factors. This treatment has been carried out at ambient and high temperature. Natural plant fibres treated with alkali have been seen to have benefits such as improved separation of fibres from fibre bundles, improved removal of unwanted surface constituents, increased tensile strength and stiffness, better thermal stability, and enhanced interfacial adhesions compared to other standard treatments. Hemp fibres are an attractive reinforcement for natural plant fibres as they are environmentally friendly compared to other natural plant fibres and exhibit good mechanical properties. This chapter mainly provides an overview of alkali treatments on hemp fibres.

In today’s world, global warming has become a concern. To overcome this, we need to reduce the carbon footprints caused by the production of materials. Much of the time, this is equivalent to the same amount of CO2 emissions per tonne of production. This is a serious concern and needs to be overcome by identifying alternative materials to have as minimal a carbon footprint as possible. In this context, hemp fiber is by far the best natural fiber when compared to its peers. As per the survey conducted by the Nova institute, hemp has CO2 emissions of only 360 Kg/tonne, whereas jute has CO2 emissions of 550 Kg/tonne, kenaf 420 Kg/tonne, and flax 350 Kg/tonne. This paper presents an experimental study of the fracture toughness of hemp-reinforced hybrid composites (HRHC). The effect of the parameters on the fracture toughness behavior of HRHC is studied using the Taguchi technique. It uses different filler combinations with hemp fiber and epoxy. Hemp fiber is used as the reinforcement, epoxy resin is used as a matrix, and banana fiber, coconut shell powder, and sawdust are used as fillers. The experimental plan is prepared using an orthogonal array and analyzed using Minitab software. The obtained results were analyzed using ANOVA and main effects plots. It was observed that the fracture toughness increases with a decrease in thickness. The fracture toughness is affected by the fiber content in the range of 25%–35% and is also affected by the filler materials.

This paper deals with the characterization of high strength and functional natural fiber reinforced composite materials which are fabricated using starch-based biodegradable resin and Manila hemp fiber. Hemp fiber reinforced cross-ply composites were prepared by a conventional hot-pressing method. Their mechanical characterization was carried out by evaluating tensile strength as a function of fiber content. It can be seen that the tensile strength of the cross-ply composites was saturated over 50 wt% due to the interaction between warp and weft during the hot-pressing. However in the case of flexible weft; such as cotton thread or resin fiber, the tensile strength of the cross-ply composites almost linearly increased with increasing fiber content. The biodegradation behavior of the hemp fiber reinforced unidirectional composites was also examined by burying them into compost media. The changes in surface morphology of the specimen and in specimen weight loss were monitored for 30 days. It is apparent that the natural fiber reinforced composites showed an enhanced biodegradation speed. This enhanced biodegradation behavior seems to be derived from increased apparent surface area of the composite specimen due to the preferential biodegradation at interface between hemp fiber and biodegradable resin as well as the preferential water transportation through internal cavity in hemp fiber.

Experimental study to measure the sound transmission loss of natural fibers at tonal excitations

Experimental study to measure the transmission loss of double panel natural fibers

This study aims to optimize the mechanical and rheological properties of cementitious mortar by incorporating hemp fibers (HF) and brick waste powder (BWP), with the goal of developing a more sustainable and eco-friendly construction material. Using response surface methodology (RSM), different proportions of HF (0, 0.25, 0.5%) and BWP (0, 10, 20%) were tested to optimize flowability, compressive and flexural strength. The experimental results indicate that the optimal composition, 0.25% HF and 10% BWP, significantly enhances mechanical performance while maintaining workability. Furthermore, the outcomes show that adding 10% BWP and around 0.5% HF considerably reduced the rheological characteristics, as seen by a longer flow time in comparison to other combinations. The ideal cement substitution rates, as determined by RSM, were 11.46% of BWP and 0.31% of HF. The study demonstrates the feasibility of using natural fibers and recycled materials in eco-friendly mortars, offering a sustainable alternative for construction. The predictive accuracy of the RSM model was validated through experimental verification, with results deviating by less than 5%. These findings contribute to the advancement of green building materials and sustainable construction practices.

The integration of renewable materials promotes sustainability in construction industry. Plant based natural fibers can be effectively utilized in cement concrete composites, being low cost and renewable. This paper presents a short review on the utilization of hemp, kenaf and bamboo natural fibers in cement based concrete. The fresh, hardened and durability properties of natural fiber reinforced concrete are discussed in brief. It is shown that the use of hemp fibers improves the compressive strength, flexural tensile strength, and toughness of concrete. Bamboo fibers can be used with different concentrations with concrete to achieve a targeting ductility. Overall, bamboo fibers improve the tensile strength and torsional toughness of concrete samples. It was also found that the use of kenaf fibers of different length and diameter improves the mechanical properties of concrete. The findings from this review confirm the feasibility of achieving standard concrete attributes by using the natural fibers in cement based concrete.

Many problems such as the increase in the world population, global drought, and greenhouse gases have caused materials used in industries to be reconsidered. This is how the concept of green composite material emerged. Using natural fibers to obtain such materials is important in terms of sustainability. This study is aimed to use hemp fiber and banana fiber as natural fiber additives in the gypsum composite to produce green bio-composite. Natural fibers are chemically modified with 5% NaOH solution. In this way, a good fiber/matrix interface interaction is provided. The composite hardness test result of 5 wt% HB fiber added sample is obtained as 50.4. Compared to the control plaster sample test result, which is 53.6, a slight decrease can be seen. However, it is observed that the fibers held the structure together and sopped the crack propagation. The increase in the porous structure with fiber addition caused a decrease in the thermal conductivity of the composite. Comparing thermal conductivity result of 5 wt% HB fiber reinforced gypsum composite (0.131 W⸳mK-1) with respect to pure gypsum result (0.237 W⸳mK-1), it gave a promising result as an insulation material.

5 - Surface modification of natural fibers

Polylactic acid (PLA) is the most promising in the bio-derived polymer's family. But its use can be constrained by its poor mechanical properties, poor thermal stability and processing difficulties. The objective of this research is to investigate and improve mechanical and dynamic thermal properties of PLA by developing PLA composites reinforced with natural fibres (hemp). Composites were prepared by melt blending of PLA with hemp fibres. Their properties were investigated using mechanical and dynamic thermal analysis. The elastic modulus increased significantly – from 4.1 ± 0.74 to 9.32 ± 0.86 (GPA) – when the weight fraction of hemp increased from 0 to 30(wt %). The storage modulus obtained by dynamic mechanical analysis increased from 2.20 to 4.58 (GPA) for the same change in the volume fraction of hemp. FE simulation of tensile testing and DMA were carried out to investigate the effect of strain rate and temperature on the observed properties respectively. The model was developed in the commercially available code MSC Marc mentate. The model validated all experimental results.