“This study investigates the processability-via Fused Deposition Modeling (FDM) 3D printing-and mechanical performance of biocomposites based on polylactic acid (PLA), polybutylene succinate (PBS), and their 50/50 wt% blend, each reinforced with hemp shive at 3 and 5 wt%.

Blending PLA with PBS represents a straightforward and encouraging strategy to enhance both the printability and mechanical properties of the individual resins, expanding the range of their potential applications.

The addition of hemp shive-a by-product of hemp processing-not only enhances the biodegradability of the composites but also improves their thermo-mechanical performance, as well as aligning with circular economy principles.

The rheological characterization, performed on all the systems, evidenced that the PLA/PBS blend possesses viscoelastic properties well suited for FDM, enabling smooth extrusion through the nozzle, good shape stability after deposition, and effective interlayer adhesion. Moreover, the constrain effect of hemp shives within the polymer matrix reduced the extrudate swell, a key factor affecting the dimensional accuracy of the printed parts. Optimal processing conditions were identified at a nozzle temperature of 190 °C and a printing speed of 70 mm/s, providing a favorable compromise between print quality, final performances and production efficiency. From a mechanical perspective, the PLA/PBS blend exhibited an 8.6-fold increase in elongation at break compared to neat PLA, and its corresponding composite showed a ductility nearly three times higher than the PLA-based counterpart’s.

In conclusion, the findings of this study provide new insights into the interplay between material formulation, rheological behavior and printing conditions, supporting the development of sustainable, hemp-reinforced biocomposites for additive manufacturing applications.”

https://pubmed.ncbi.nlm.nih.gov/40942198

“This study explores the use of hemp powder—obtained by grinding hemp shive—as a natural filler in PLA, PBS, and a PLA/PBS blend at 50/50 by weight.”

“Overall, the PLA/PBS blend reinforced with hemp shive presents a promising and sustainable formulation for FDM applications, delivering a well-balanced compromise between processability, print quality, mechanical performance and environmental impact.”

https://www.mdpi.com/2073-4360/17/17/2280

“For the first time, the hydrophilicity of hemp shiv was modified without the compromise of its hygroscopic properties.

This research focused on the use of sol-gel method in preparation of coatings on the natural plant material, hemp shiv, that has growing potential in the construction industry as a thermal insulator.

The sol-gel coatings were produced by cohydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) using an acidic catalyst. Methyltriethoxysilane (MTES) was added as the hydrophobic precursor to provide water resistance to the bio-based material. Scanning electron microscopy (SEM) and focused ion beam (FIB) have been used to determine the morphological changes on the surface as well as within the hemp shiv.

It was found that the sol-gel coatings caused a reduction in water uptake but did not strongly influence the moisture sorption behaviour of hemp shiv. Fourier transformed infrared (FTIR) spectroscopy shows that the coating layer on hemp shiv acts a shield, thereby lowering peak intensity in the wavelength range 1200-1800 cm^-1.

The sol-gel coating affected pore size distribution and cumulative pore volume of the shiv resulting in tailored porosity. The overall porosity of shiv decreased with a refinement in diameter of the larger pores. Thermal analysis was performed using TGA and stability of coated and uncoated hemp shiv have been evaluated.

Hemp shiv modified with sol-gel coating can potentially develop sustainable heat insulating composites with better hygrothermal properties.”

https://pubmed.ncbi.nlm.nih.gov/31258251

“Sol–gel coated hemp shiv showed improved thermal stability and good water resistance. It has also potential to be mixed with binders to produce composites with better interfacial adhesion, lower drying times, provide ease of handling during the manufacturing stage and ultimately a more robust bio-based thermal insulation building material.”

https://link.springer.com/article/10.1007/s10971-018-4621-2

“This study investigated the utilization of innovative green composites made from hemp shiv, a waste by-product of hemp cultivation, with the aim of promoting sustainability within the construction industry.

The manufacturing method involved the application of pressure in a mold to create the samples.

These materials were produced using an environmentally friendly binder consisting of colophony, arabic gum, and corn starch. Moreover, white glue and bioepoxy were also used to compare with the green resins. Three different binder compositions were used for the specimens. The samples underwent mechanical testing through tensile and bending assessments, and their performance was compared to that of non-green binders to validate the effectiveness of the manufacturing processes.

The study revealed that decreasing the moisture content during the curing process was crucial for improving the mechanical properties. The best results were achieved when using arabic gum as a binder, yielding a tensile strength of 2.16 MPa and a bending strength of 5.25 MPa, with a composition of 62.5% hemp shiv and a manufacturing process involving a pressure of 5 MPa.”

https://pubmed.ncbi.nlm.nih.gov/39203077

“Gathering all this information, it can be concluded that in some applications in the construction industry, hemp shiv could be use as a more ecological material to substitute the inorganic commercial materials. Coffered ceilings could offer a great starting point into the construction sector for hemp shiv.”

https://www.mdpi.com/1996-1944/17/16/3900

“The growing demand for sustainable building materials has boosted research on plant-based composite materials, including hemp shives bound with biodegradable binders.

This study investigates the enhancement of potato-starch-based binders with sodium metasilicate and glycerol to produce eco-friendly bio-composites incorporating hemp shives.

Potato starch, while renewable, often results in suboptimal mechanical properties and durability in its unmodified form. The addition of sodium metasilicate is known to improve the mechanical strength and thermal stability of starch-based materials, while glycerol acts as a plasticizer, potentially enhancing flexibility and workability.

Bio-composites were produced with varying concentrations of sodium metasilicate (0-107% by mass of starch) and glycerol (0-133% by mass of starch), and their properties were evaluated through thermal analysis, density measurements, water absorption tests, compressive strength assessments, and thermal conductivity evaluations.

The results demonstrate that sodium metasilicate significantly increases the bulk density, water resistance, and compressive strength of the bio-composites, with enhancements up to 19.3% in density and up to 2.3 times in compressive strength. Glycerol further improves flexibility and workability, though excessive amounts can reduce compressive strength.

The combination of sodium metasilicate and glycerol provides optimal performance, achieving the best results with an 80% sodium metasilicate and 33% glycerol mixture by weight of starch.

These modified bio-composites offer promising alternatives to conventional building materials with improved mechanical properties and environmental benefits, making them suitable for sustainable construction applications.”

https://pubmed.ncbi.nlm.nih.gov/39410482

https://www.mdpi.com/1996-1944/17/19/4911

“Innovative Hemp Shive-Based Bio-Composites, Part II: The Effect of the Phase Change Material (PCM) Additive on Characteristics of Modified Potato Starch Binders”

https://pubmed.ncbi.nlm.nih.gov/40004414

“The construction industry is facing an increased demand to adopt sustainable green building materials to minimize the carbon footprint.

Hemp concrete is a green building material not only because of its low embodied carbon but also because of its ability to regulate heat and relative humidity. Its thermal characteristics are often viewed as favorable for reducing the energy used to heat or cool indoor buildings.

The current research is focused on the properties of hemp concrete from Slovak manufacturers which can be effectively used in construction as a replacement for conventional building materials and can also be effectively applied in building renovations.

The basic thermal properties of hemp concrete, i.e., specific heat capacity, thermal conductivity, effusivity, thermal diffusivity, and lag time, were determined. The determination of all properties is dependent on the knowledge of heat fluxes at the surface and the density of samples.

The insulation ability was expressed with a thermal conductivity of 0.099 W·m^-1·K^-1. The accumulation was expressed with a specific heat of 1540 J·kg^-1·K^-1 and density of 322 kg·m^-3 in the air environment temperature of 22 °C and relative humidity of 50%.

To assess moisture properties, the moisture content and the speed of molecules during diffusion and lag time, based on the thickness of the hemp concrete samples, were measured. The speed of water molecules during diffusion in hemp concrete was 8.6 × 10^-7 m·s^-1.

The study shows that hemp concrete has interesting hydrothermal properties for use as an insulation layer in envelope structures. Thus, this material can be used effectively in the construction field in order to meet the requirements of the current standards, which aim to reduce energy and environmental impacts.”

https://pubmed.ncbi.nlm.nih.gov/40271892

“Hemp concrete is a lightweight bio-based material, which attracts the attention of developers in Slovakia. This lightweight bio-based material is intended to be an excellent thermal insulator and moisture diffusor with enhanced durability. It holds the potential to significantly impact the climate quality inside buildings and their overall sustainability from a life cycle perspective. Hemp concrete consists of the inner woody core of the hemp plant mixed with a lime-based binder (hydraulic lime and non-hydraulic lime) and water.”

https://www.mdpi.com/1996-1944/18/7/1651

“The construction industry is facing increased demand for adopting sustainable ‘green’ building materials to minimise the carbon footprint of the infrastructure sector to meet the United Nations 2030 Sustainability Goals.

Natural bio-composite materials such as timber and bamboo have been widely used in construction for centuries. Hemp has also been used in different forms in the construction sector for decades for its thermal and acoustic insulation capability owing to its moisture buffering capacity and thermal conductivity.

The current research aims to explore the possible application of hydrophilic hemp shives for assisting the internal curing of concrete materials as a biodegradable alternative to currently used chemical products.

The properties of hemp have been assessed based on their water absorption and desorption properties associated with their characteristic sizes.

It was observed that, in addition to its excellent moisture absorption capacity, hemp released most of its absorbed moisture into the surroundings under a high relative humidity (>93%); the best outcome was observed for smaller hemp particles (<2.36 mm).

Furthermore, when compared to typical internal curing agents such as lightweight aggregates, hemp showed a similar behaviour in releasing its absorbed moisture to the surroundings indicating its potential application as a natural internal curing agent for concrete materials.

An estimate of the volume of hemp shives required to provide a similar curing response to traditional internal curing techniques has been proposed.”

https://pubmed.ncbi.nlm.nih.gov/37297126

https://www.mdpi.com/1996-1944/16/11/3993

“There has been increasing interest in green and recyclable materials to promote the circular economy. Moreover, the climate change of the last decades has led to an increase in the range of temperatures and energy consumption, which entails more energy expenditure for heating and cooling buildings.

In this review, the properties of hemp stalk as an insulating material are analyzed to obtain recyclable materials with green solutions to reduce energy consumption and reduce noise to increase the comfort of buildings.

Hemp stalks are a low-value by-product of hemp crops; however, they are a lightweight material with a high insulating property.

This study aims to summarize the research progress in materials based on hemp stalks and to study the properties and characteristics of the different vegetable binders that could be used to produce a bio-insulating material. The material itself and its microstructural and physical aspects that affect the insulating properties are discussed, as is their influence on durability, moisture resistance, and fungi growth.

Research suggests using lignin-based or recyclable cardboard fiber to develop a bio-composite material from hemp stalk, but long-term stability requires further investigation.”

https://pubmed.ncbi.nlm.nih.gov/37110081

“According to the results presented in the different studies of the last decades, hemp is positioned as a green material with great insulating properties that could replace some inorganic commercial materials to improve the insulating performance of buildings and build green buildings.”

https://www.mdpi.com/1996-1944/16/8/3245

“We investigated the thermal conductivity of materials based on pyrolysis temperature, filler loading, filler size, and type of biomass feedstock.

Hemp stalk and switchgrass were pyrolyzed at 450, 550, and 650 °C and crushed into 50, 75, and 100 μm particle sizes. Biocarbon fillers (10, 15, and 20 wt %) were added to the bioepoxy polymer matrix.

The study showed increased filler loading and particle size increased thermal conductivity-the biocomposite samples with 20 wt % filler loading of 100 μm particle size of the biocarbon obtained at 650 °C showed the maximum thermal conductivity in both hemp biocarbon-filled composites (0.59 W·m^-1·K^-1) and switchgrass-filled composites (0.58 W·m^-1·K^-1) with the highest flame time. Biocarbon in biofiber-reinforced polymer composites can improve thermal conductivity and extend the flame time.

These findings significantly contribute to developing hemp-based bioepoxy composite materials for thermal applications in various fields. These include insulating materials for buildings and thermal management systems, energy-efficient applications, and help in material selection and product design with a positive environmental impact.”

https://pubmed.ncbi.nlm.nih.gov/37151540

“These novel composite materials will likely be increasingly important in sustainable manufacturing and construction processes. Using sustainable and renewable materials like hemp and biocarbon aligns with the trend toward eco-friendly and green manufacturing practices.”

https://pubs.acs.org/acsodf/article/8/17/15422/343646/Thermal-Response-of-Biocarbon-Filled-Hemp-Fiber

“The present work aims to develop thermosetting resins using epoxidized hemp oil (EHO) as a bio-based epoxy matrix and a mixture of methyl nadic anhydride (MNA) and maleinized hemp oil (MHO) in different ratios as hardeners.

The results show that the mixture with only MNA as a hardener is characterized by high stiffness and brittleness. In addition, this material is characterized by a high curing time of around 170 min. On the other hand, as the MHO content in the resin increases, the mechanical strength properties decrease and the ductile properties increase.

Therefore, it can be stated that the presence of MHO confers flexible properties to the mixtures. In this case, it was determined that the thermosetting resin with balanced properties and high bio-based content contains 25% MHO and 75% MNA. Specifically, this mixture obtained a 180% higher impact energy absorption and a 195% lower Young’s modulus than the sample with 100% MNA.

Also, it has been observed that this mixture has significantly shorter times than the mixture containing 100% MNA (around 78 min), which is of great concern at an industrial level. Therefore, thermosetting resins with different mechanical and thermal properties can be obtained by varying the MHO and MNA content.”

https://pubmed.ncbi.nlm.nih.gov/36987185

“After compiling all the data obtained, it can be concluded that maleinized hemp oil (MHO) is an excellent crosslinking agent next to methyl nadic anhydride (MNA), which is of petrochemical origin, for epoxidized hemp oil (EHO).

After performing the mechanical tests, it was observed that the sample containing 100% MNA (100MNA) presented with high rigidity and brittleness, whereas, with the addition of MHO in different amounts, it was observed that the material showed greater ductility and flexibility.”

https://www.mdpi.com/2073-4360/15/6/1404

“In this study, hemp seed oil was reacted with maleic anhydride in an ene reaction to obtain maleinized hemp seed oil (MHO).

The use of MHO as a plasticizer and compatibilizer has been studied for polylactic acid (PLA) and thermoplastic starch (TPS) blends (80/20, respectively). By mechanical, thermal and morphological characterizations, the addition of MHO provides a dual effect, acting as plasticizer and compatibilizer between these two partially miscible biopolymers.

The addition of MHO up to 7.5 phr (parts by weight of MHO per hundred parts of PLA and TPS) revealed a noticeable increase in the ductile properties, reaching an elongation at break 155% higher than the PLA/TPS blend. Furthermore, contrary to what has been observed with maleinized oils such as linseed oil, the thermal properties do not decrease significantly as a result of the plasticizing effect, due to the compatibilizing behavior of the MHO and the natural antioxidants present in the oil.

Finally, a disintegration test was carried out in aerobic conditions at 58 °C, for 24 days, to demonstrate that the incorporation of the MHO, although causing a slight delay, does not impair the biodegradability of the blend, obtaining total degradation in 24 days.”

https://pubmed.ncbi.nlm.nih.gov/33922939

“MHO is shown to be a potential plasticizer and compatibilizer of organic origin, to be used in different polymeric blends without affecting their biodegradability.”

https://www.mdpi.com/2073-4360/13/9/1392