Shives Research Articles

Enhanced stability of PVA electrospun fibers in water by adding cellulose nanocrystals

Abstract The solubility of electrospun poly(vinyl alcohol) nanofiber mats (PVAES-NFM) is strongly influenced by loading with nanocellulose (NC). The NC was derived from hemp shives obtained by steam explosion autohydrolysis followed by water and alkaline extraction, ball milling, and ultrasonication treatments. It was demonstrated for the first time that PVAES-NFM does not disintegrate in aqueous medium after simple adding of NC without any additional chemical or physical modification (PVAES-NFMNC). The structural and thermal studies on PVAES-NFMNC indicated that enhanced stability in aqueous medium can be explained by interactions between surface groups of NC and PVA macromolecules as well as by reinforcing the effect of NCs. The experimental findings could be important for filtration applications in environments with high relative humidity.

Influence of Water Absorption on The Selected Properties of Hemp Hurds Composites

Influence of Water Absorption on The Selected Properties of Hemp Hurds Composites

Influence of water absorption on the selected properties of hemp hurds composites

All composites based on natural fibers absorb moisture in humid atmosphere and when immersed in water or capillary action. Therefore, one of the major drawbacks of polymer fibers is their high availability to moisture sorption and their heterogeneity, which leads to a weak interface between the fibers and matrix and a poor transfer of the applied stress between the materials, resulting to reduction of physico-mechanical properties. An experimental investigation was conducted to testing the water absorption of hemp composites with MgO-cement binder and its influence on the physico-mechanical and thermal characteristics of composites. The achieved results of composites indicate that water absorption test has deteriorative influence on observed properties due to the degradation of the fibre-matrix interface.

Influence of Water Absorption on The Selected Properties of Hemp Hurds Composites

All composites based on natural fibers absorb moisture in humid atmosphere and when immersed in water or capillary action. Therefore, one of the major drawbacks of polymer fibers is their high availability to moisture sorption and their heterogeneity, which leads to a weak interface between the fibers and matrix and a poor transfer of the applied stress between the materials, resulting to reduction of physico-mechanical properties. An experimental investigation was conducted to testing the water absorption of hemp composites with MgO-cement binder and its influence on the physico-mechanical and thermal characteristics of composites. The achieved results of composites indicate that water absorption test has deteriorative influence on observed properties due to the degradation of the fibre-matrix interface.

Influence of chemical modification on hemp–starch concrete

As a result of growing environmental consciousness, the issues of sustainability and industrial ecology are guiding the development of the next generation of materials and processes. Renewable resources such as hemp hurds in the field of green polymeric materials with their new range of applications represent an important basis in order to fulfil the ecological objective of creating eco-friendly materials.This work deals with the impact of several chemical treatments of hemp hurds on the properties of hemp–starch composite which is made of 100% of natural resources. Two compositions were manufactured, the first one with untreated hemp hurds in starch matrix and the second one with treated hemp hurds in starch matrix. A set of chemical treatments was performed to solubilize hemicelluloses and lignin seal surrounding the cellulose bundle in the first step and then a coupling agent was used to provide a stable bond between hemp hurds and starch matrix. The influence of the treatments on hemp hurds characteristics was investigated by scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA) and attenuated total reflectance spectroscopy (ATR). Moreover, the mechanical properties of green composites were studied and it seems that alkaline treatment followed by silane treatment improves the stiffness of composites according to the results of mechanical properties after treatments.

Influence of Gender on the Mechanical and Physical Properties of Hemp Shiv Fiber Cell Wall in Dioecious Hemp Plant

Hemp (Cannabis sativa L.) shiv has great potential for the production of bio-composites as a reinforcement material. To gain more information about hemp shiv, this research studied the influence of gender on the physical and mechanical properties of the fiber cell wall in the shiv of three dioecious hemp plant varieties by optical microscopy, image analysis software, WXRD, and nanoindentation. The results show that a hemp plant’s gender greatly influences the properties of hemp shiv. While long and thin in female hemp shiv, the fibers are shorter with a larger diameter in male hemp shiv. In addition, the cell walls in female shiv are thinner than those in male shiv. The microfibril angle (MFA), relative degree of crystallinity, elastic modulus, and hardness values of fiber cell walls as well as the lignin content in male hemp plants are higher than those in female hemp plants. Besides, the relationship between mechanical properties and MFA do not align with those observed in previous research, which shows that the gender of an individual plant has a greater effect on the mechanical properties of the fiber cell wall than does its MFA. Thus, when the fiber from this dioecious plant is investigated or used, the sex of the plant should be known and considered.

Influence of various starch/hemp mixtures on mechanical and acoustical behavior of starch-hemp composite materials

The starch-hemp composite materials are manufactured from the natural raw materials (water, starch and hemp shives) and a new durable material for construction and building. In this work, experimental investigation was carried out to study the mechanical and acoustical performance of starch-hemp composite materials. The starch-hemp composite materials specimens with five Hemp/Starch ratios (H/S = 6, 8, 10, 12 and 14), were manufactured by using the optimal binder and two hemp shives (0–15 mm and 0–20 mm). Density of the starch-hemp composite materials varies with the H/S ratio. The dry density for the starch-hemp composite materials is lower, between 163.6 kg/m3 and 169.1 kg/m3 in case of the hemp shives 0–15 mm and between 168.1 kg/m3 and 174.3 kg/m3 for the hemp shives 0–20 mm. The relation between stress and strain of the composite materials is not linear. The ultimate compressive stress can reach 0.55 MPa and the compressive strain is up to 30%. The results obtained by test show that the tensile strength depends strongly on the Hemp/Starch ratio and the hemp shives sizes. The variation of elasticity modulus and Poisson's ratio in function of the H/S ratio was also analyzed in this paper. The mechanism of the cracks or failure of the specimens was studied by using ARAMIS optical system. The study on acoustical behavior shows that the starch-hemp composite materials are a good sound absorber material for medium and high frequencies with a value around 0.7. The influence of the H/S ratio on the absorption coefficient is small. The results show that the starch-hemp composite materials have a good mechanical and acoustical performance and can be used as building materials.

Electrospinning of Poly(Vinyl Alcohol) Nanofiber Mats Reinforced by Lignocellulose Nanowhiskers

This article reports on electrospun poly(vinyl alcohol) (PVA) modification with lignocellulose nanowhiskers (LCNWs) produced from hemp shives without using harsh preparation steps. LCNWs were obtained by using steam explosion (SE) pretreatment, ball milling, and ultrasonication. Formation of LCNWs was confirmed by atomic force microscopy. Obtained LCNWs were used to modify the mechanical properties of electrospun PVA nanofibers. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy analyses provided clear evidence of the presence of cellulose nanowhiskers in the PVA/LCNW electrospun mats. It was found that tensile stress at break increases more than fivefold for PVA nanofiber mats reinforced with LCNWs.

Impacts of Limestone Particle Size on the Performance of Flexible Wood Fiber Composite Floor

Sustainable wood floor (WFF), produced from natural plants, is a sort of novel green and ecofriendly composite floor, which has been attracting more and more attention in the world. WFF also gives a solution of utilizations of agricultural wastes, such as bamboo mats and hemp hurd. The additive limestone powder plays key role in the performance of flexible bamboo composite floor, so, in this paper, the effects of limestone size and size distributions were investigated. The best particle size distributions of limestone are 25 wt% of 48 μm, 25 wt% of 106 μm, and 50 wt% of 160 μm. The as-obtained WFF has good elasticity, good affinity, and strong comfortableness as well as free formaldehyde release.

Properties Characterization of Chemically Modified Hemp Hurds.

The effect of chemical treatment of hemp hurds slices in three solutions (EDTA (Ethylenediaminetetraacetic acid), NaOH and Ca(OH)2) on the properties of natural material was discussed in this paper. Changes in the morphology, chemical composition and structure as well as thermal stability of hemp hurds before and after their modification were investigated by using FTIR (Fourier transform infrared spectroscopy), XRD (X-ray powder diffraction analysis) and TG (thermogravimetry)/DSC (differential scanning calorimetry). Size exclusion chromatography (SEC) measurements were used for determination of degree of cellulose polymerization of hemp hurd samples. Chemical modification is related to the partial removal of non-cellulosic components of lignin, hemicellulose and pectin as well as waxes from the surface of hemp hurd slices. Another effect of the chemical treatment applied is connected with increasing the crystallinity index of cellulose determined by FTIR and XRD methods. Decrease in degree of cellulose polymerization and polydispersity index in chemically modified hemp hurds compared to the original sample was observed. Increase in thermal stability of treated hemp hurd was found. The most significant changes were observed in alkaline treated hemp hurds by NaOH.

ENHANCING COPPER AND LEAD BIOACCUMULATION IN RAPESEED BY ADDING HEMP SHIVES AS SOIL NATURAL AMENDMENTS

The current study reveals the results of a phytoremediation process applied to a multi metal contaminated soil, located in close proximity to an energy power plant. Phytoremediation process was studied using the rapeseed cultivation, both in the presence and absence of hemp shives, considered as potential natural soil amendments. The physiological responses of the rapeseed plants, such as variations in length and accumulation of biomass, as well as the content of assimilating pigments were investigated. The concentrations of Cu (II) and Pb (II) ions have also been determined in soil and plants aiming at locating the metal ions in different organs of the plants. By using hemp shives as amendments, bioaccumulation of copper and lead ions in plant increases. The plants cultivated in the presence of high amounts of heavy metal ions have been characterized by an inhibition of growth and development that consisted in decrease of root and stem lengths, as well in the amount of biomass accumulated in different vegetative organs.

A chemical, morphological and mineralogical study on the interaction between hemp hurds and aerial and natural hydraulic lime particles: Implications for mortar manufacturing

Mixing hemp with aerial or natural hydraulic lime gives rise to mortars with improved flexibility and insulation but with peculiar microstructure compared to lime-aggregate mortars. The chemical–mineralogical and morphological investigation carried out here shows that hemp absorbs most of the water present in the matrix, causing superficial deposition and scarce adhesion of the lime to the hemp. This also delays the hardening process, as demonstrated by the high content of portlandite, vaterite and calcium silicates found after three months of curing. Some modifications to the production and curing procedures are suggested to improve the microstructure and final performance of hemp-lime mortars.

Comparison of water absorption behavior of biocomposites based on hemp hurds

Nowadays, the use of natural fibers as reinforcements for composite is attractive. Plant fibers from hemp, jute, sisal and others are used for the purposes of the construction. In this paper the attention is given to the preparation of composites based on hemp hurds. Hemp hurds is obtained from hemp stem in the fibers processing. Lightweight composites based on alternative binder MgO-cement and unmodified and chemically modified hemp hurds as filler were prepared. Their water absorption behavior was observed in time dependence.

Study of the Hygric Behaviour and Moisture Buffering Performance of a Hemp–Starch Composite Panel for Buildings

This paper presents the results of a laboratory investigation into the hygric properties and moisture buffering performance of hemp-starch composite panels designed for building applications. Composite panels were produced by bonding hemp shiv with wheat starch as a binder. Two types of hemp shiv were tested: chemically processed shiv with enhanced adhesion between fibers and starch matrix, and non-treated shiv. The panels were then characterised in terms of their hygroscopic properties (sorption curve and vapour diffusion resistance factor) and their moisture buffering performance (moisture buffering value, MBV). The determination of theoretical MBV was based on the effusivity of the material, which is obtained from its basic hygroscopic characterisation. The results show that both panels are excellent hydric regulators that can be used to improve indoor hygrothermal comfort by buffering indoor relative humidity variations.

Omega-3 fatty acid production from enzyme saccharified hemp hydrolysate using a novel marine thraustochytrid strain

In this work, a newly isolated marine thraustochytrid strain, Schizochytrium sp. DT3, was used for omega-3 fatty acid production by growing on lignocellulose biomass obtained from local hemp hurd (Cannabis sativa) biomass. Prior to enzymatic hydrolysis, hemp was pretreated with sodium hydroxide to open the biomass structure for the production of sugar hydrolysate. The thraustochytrid strain was able to grow on the sugar hydrolysate and accumulated polyunsaturated fatty acids (PUFAs). At the lowest carbon concentration of 2%, the PUFAs productivity was 71% in glucose and 59% in the sugars hydrolysate, as a percentage of total fatty acids. Saturated fatty acids (SFAs) levels were highest at about 49% of TFA using 6% glucose as the carbon source. SFAs of 41% were produced using 2% of SH. This study demonstrates that SH produced from lignocellulose biomass is a potentially useful carbon source for the production of omega-3 fatty acids in thraustochytrids, as demonstrated using the new strain, Schizochytrium sp. DT3.

Antibacterial properties of hemp hurd powder against E. coli

ABSTRACTHemp (Cannabis sativa L.) is an eco‐friendly and multifunctional plant. Hemp hurd is a by‐product of hemp plant during hemp fiber separation. Although hemp hurd is repeatedly announced owing antibacterial activity, it has never been systematically investigated and reported. In this study, the antibacterial activity of hemp hurd powder against Escherichia coli is investigated. This article reveals antibacterial activity of hemp hurd where hemp hurd powder inhibits the growth of E. coli. Meanwhile, the self‐contamination (forming during retting process) inside hemp hurd has dramatic impact on the antibacterial performance. To achieve better antibacterial activity, hemp hurd was heat treated to eliminate self‐contaminations. The impact of the particle sizes and heat treatment on the antibacterial effectiveness was evaluated. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41588.

Mechanical Properties of Pre-Compressed Hemp-Lime Concrete

To answer different problems set by the 21st century, European Union is constantly updating the old and adapting new directives and regulations. One of these directives is 2010/31/EU as a piece of Energy package which sets forth a goal to reduce primary energy use by 20% and to achieve 20% reduction in greenhouse gas emissions by 2020. It also sets a task for all buildings built after 2020 to be zero-energy buildings. To achieve these goals, next to existing building materials, a new, innovative, and more sustainable materials needs to be studied and implemented. One of these possible materials is lime-hemp concrete – a self-bearing thermal insulation material that consist of lime and hemp shives. Its mechanical properties seem promising, and thermal conductivity below 0,08 W/m*K is significant result for a material that sequesters more CO2 then is created in its life cycle. In the paper an effect of pre-compressed of hemp-lime mix before curing is studied. Two different binders were chosen (dolomitic lime and dolomitic lime with metakaolin) and three different compaction ratios – 50, 25 and 0 %. As expected, the compaction has a direct impact on compressive strength, as well as flexural. The elevated densities also have a negative effect on thermal conductivity, yet not as much if the same density would be achieved with addition of more binder. This method could help to produce lime-hemp concrete materials with better strength/thermal conductivity ratio. A further research of improved drying techniques is needed, as the samples had softer inner part, due to excess moisture during curing. DOI: http://dx.doi.org/10.5755/j01.sace.8.3.7451

Impact of hemp shiv on cement setting and hardening: Influence of the extracted components from the aggregates and study of the interfaces with the inorganic matrix

The need for efficient building insulation with low environmental impact has led to a growing market for hemp lightweight concretes. However, a deeper understanding of the interactions between hemp particles and binders during the setting and hardening phase is needed to meet required industrial specifications. In this paper, the effects of three types of shiv and their corresponding water extracts on cement setting are compared. Various analyses show that these extracts delay hydration, thereby negatively affecting the mechanical properties of the cement. A comparison of the chemical composition of shiv water extracts highlights the importance of plant quality and the variability of their effects on cement. The development of a new methodology, combined with the use of 13C labeled plant material, made it possible to closely monitor the physiochemical phenomena occurring at the plant aggregate and cement matrix interface.

Improvements in self-consolidating cementitious composites by using micro carbonized aggregates

There is growing interest in the use of self-consolidating cementitious systems in construction industry. The present research was conducted to enhance the mechanical performance of cement composites by the utilization of micro-sized inert particles. This paper deals with the synthesis of micro-sized inert carbonized particles from hemp hurds. The synthesized carbonized particles were characterized by field emission scanning electron microscope (FESEM). These particles were further used as additive in self-consolidating cement composites. Total of four different wt% additions (i.e. 0.08, 0.20, 1.00 and 3.00 by wt% of cement) were investigated. The cement composites containing carbonized particles inclusions were characterized by three point bending and compression tests. The results indicate that the carbonized particles additions enhanced the flexural and compressive strengths of the cement composites. It was also observed that the fracture properties and the energy absorption capability of the cement composites were enhanced substantially.

Manufacturing Particleboard Using Hemp Shiv and Wood Particles with Low Free Formaldehyde Emission Urea-Formaldehyde Resin

Abstract In order to better use the hemp shiv in manufacturing particleboard panels, tests for determining the mechanical and physical properties of this particleboard were performed according to the Chinese standard for wood-based paneling. The results showed the following. (1) The properties of the particleboard are optimal, with a 1:1 ratio of hemp shiv to wood particles; hemp shiv and wood particles actually strengthen each other when particleboard is made from a mixture of hemp shiv and wood particles. (2) The low density and the low mechanical properties of fiber cell walls were both advantages for the hemp shiv used to manufacture the particleboard panels.