Cannabis Research: A Timelined Review of Cannabis Studies

Cannabis is derived from Cannabis sativa, a member of the Cannabaceae family. The use of this substance, also known as marijuana, for medical purposes is on the agenda beyond its pleasurable use that comes to mind first. It is reported that approximately 22.2 million people in the USA used cannabis for 1 month. Despite this, the use of cannabis for medical purposes has been legalized in 28 states in the USA today. So, do you know how much research is done on cannabis?

Research on cannabis is very limited due to the restrictions. Still, there are some studies published, which may be a key to understanding the benefits and advantages of cannabis. For example, the US National Academies of Science, Engineering, and Medicine concluded that there is substantial evidence that cannabis is effective in treating chronic pain in adults, as a result of their study. I have compiled important research on cannabis and categorized them into 5-year periods. Here is the most recent cannabis research.

Cannabis Research Between 2000-2005

Keller et al. (2001) conducted research to determine the stage of growth where the hull and hives can be separated from unpainted industrial cannabis with as little fiber damage as possible. In addition, within the scope of the study, the chemical composition of the shell and the molecular weight of the fiber cellulose were analyzed to predict the fiber quality that can be obtained after a baking process. For this, the fibers were extracted using a standard chemical cleaning process.

Studies have been carried out in nine growth stages of plants, ranging from vegetative stages to aging. Considering only the mechanical modification of the hulls of green dry stalks, the results revealed that a harvest time at the beginning of seed maturity led to an easy modification process with no effect on the tensile strength of the hull. For the modification of fresh stems, including the next cleaning process, a harvest after flowering of male plants results in fiber losses during modification and fibers with reduced fineness.

Kozlowski et al. (2002) aimed to develop nonwoven fabrics containing natural fibers with limited flammability. In the studies carried out at the Natural Fiber Institute (Poznan, Poland), the content of recycled synthetic, wool, cannabis, and flax fibers was increased, and nonwoven fabrics with fire resistance were produced.

Considering the results, the assumptions that nonwoven materials produced using cannabis fibers can be used as valuable and effective barrier materials in upholstery systems for furniture and car seats and in beds where ecological aspects are very important, have increased fire resistance.

Hautala et al. (2004), plywood type composites were produced from cannabis fiber strips and epoxy resin. The flexural strength results of the produced composites were found to be similar to those of conventional plywood. When evaluated in terms of appearance, production features, and workability, it is stated that the composites produced are suitable for floor and furniture applications.

Aziz and Ansell (2004) investigated the mechanical properties of unprocessed and alkali-treated cannabis and cannabis fiber reinforced polyester composites. The alkali-treated fibers of both composite types showed superior flexural strength and flexural modulus values compared to untreated fibers. In addition, the effect of using polyester resins specially formulated for natural fibers has also been studied. It has been observed that these polyesters have a positive effect on the strength of composites.

Oujai et al. (2004) investigated the effect of solvent extraction, alkalization, and acrylonitrile (AN) grafting on the surface properties of cannabis fibers and the mechanical properties of cannabis fibers. Spectroscopic studies and diffraction techniques showed a slight decrease in the crystallinity index. Structural transformation of fibers from cellulose 1 to cellulose 2 was observed at a high NaOH concentration of 10-20% by weight.

No crystal structure transformation of acrylonitrile grafted fibers was observed after mercerization, only an X-ray crystallinity index variation with the amount of grafting was observed. It is stated that the moisture recovery of pre-treated and modified fibers varies depending on the structure of the fibers and the amount of grafting.

Tserki et al. (2005) investigated the effect of solvent-free and catalyst-free an-hydride treatment on different lignocellulosic materials to produce low-cost, fully biodegradable composites. Specifically, the effect of three lignose-cellulosic materials on properties such as the esterification of flax, cannabis, and wood fibers, crystallinity and surface morphology X-Ray Diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy ( FTIR), and scanning electron microscopy (SEM) methods.

The chemical composition of the fibers was determined and the ester content was determined to depend on the hemicellulose/lignin content of the fibers. XPS and FTIR experiments revealed the presence of acetyl/propionyl groups located in an ester bond with fiber components for treated fibers. SEM examination showed that the surfaces of esterified materials were smoother than the untreated material.

Cannabis Research Between 2005-2010

In their study, Turunen and Werf (2007) aimed to measure the main effects associated with hemp yarn production using the life cycle analysis (LCA) methodology and to compare the effects of hemp yarn with hemp and cotton yarn. To assess the effects of cannabis plant production, a general Euro-European scenario based on cannabis cultivation practices in Hungary and France has been drawn.

The flax plant scenario is based on production practices in France, Belgium, and the Netherlands. For hemp fiber processing, the traditional warm water pooling system was taken as the reference according to current production practices in Hungary. Three scenarios have been compared to this reference:

  • Bio-pooling: extracting the cannabis plant while it is green and then pooling it in water with the selected bacterial strain
  • BabyHemp, which is based on drying and holding pre-matured cannabis,
  • Keeping the flax raw.

Bio-pooling has higher impacts for climate change and energy use than the reference scenario due to high energy use in the fiber processing phase, while BabyHemp has a higher impact than the reference scenario due to eutrophication, land take (due to low efficiency), and pesticide use. It has been observed to have high effects. Comparison with cotton was difficult due to the lack of comparable data, but the hemp plant was found to clearly outperform cotton in terms of production stage, pesticide, and water use.

This study focuses on the yarn production chain, which is one of the first three main stages of the life cycle. The first stage in this chain is crop production. In the fiber processing stage, the fibers are removed from the stem and converted into raw material for yarn and then fabric production. There are many alternative production techniques and methods, but when examined in more detail, there is no standard textile production chain for hemp.

The fiber processing stage is the bottleneck of the hemp textile production chain. Today, the traditional fiber processing process of hemp is at the technological stage 50 years ago. Because this technology is labor-intensive, it is only suitable for countries with low labor costs (eg Hungary, Romania, China). For West-Europe, there is still no optimum processing method. Life cycle analysis has been terminated only in yarn production since the production and analysis of t-shirt in textiles is found to be more complex.

It was foreseen that priority should be given to reducing environmental impacts related to hemp yarn production, reducing energy use in fiber processing and yarn production stages, and reducing eutrophication during the crop production stage. It was observed that less than half of the total amount of fiber was recovered as long fiber, so it was stated that studies should be done to increase the long fiber yield.

Kostic et al. (2008) examined the effect of different concentrations of alkalinization on hemp fibers at different temperatures. Hemp fibers were treated with sodium hydroxide solutions at room and boiling temperature, at different time periods, and in both tension and rest. The fibers have been characterized to determine the quality, chemical composition, fineness, mechanical, and absorption properties of the fibers.

At the end of the study, the modified hemp fibers were thinned, the lignin content of the fibers was reduced, their flexibility was increased, and in some cases, the tensile properties were developed, and an original method was developed to evaluate the tensile properties. This method involves determining the tensile strength or strength of the fibers as a straight bundle using extrapolation values ​​up to zero distance between stems (zero test length).

The values obtained for the flat bundle strength extrapolated to the zero test length show a high correlation with the values measured in single fibers and require much less time and skill. It is foreseen that this method can be useful in research studies for determining environmental effects and treating fiber strength, and in investigating the relationships between these fiber properties, processing conditions, and end-product quality, and can be used for testing commercial shipments.

In general, the alkali treatment provided high resilience of the modified fibers under tension with 18% NaOH. In some improvements, changes in flexibility reflect changes in chemical composition (partial breakdown of lignin and other non-cellulosic materials) and structure (rearrangement of fibrils). The water retention values of alkali-modified cannabis were found to be lower than the value of untreated fibers as a result of the removal of easily accessible non-cellulosic water-absorbent and retention materials and the change in the fiber structure.

Zhang et al.’s (2008) ‘s studies have shown that the pooling process in seawater gives good pooling results and is presented as a possible alternative to the pooling process to remove high-quality fibers from cannabis and reduce freshwater consumption. Pooling in marine water, three pectinolytic strains isolated from tanks (population of individuals with the same type of genotype) exhibited a high pectinase activity and good pooling performance.

According to FTIR and chemical analyzes, pectin and hemicellulose contents were found to be lower in seawater pooled fibers than raw cannabis fiber. In addition, SEM demonstrated that non-cellulosic gummy materials in cannabis fibers can be largely removed by pooling in seawater.

In the study conducted by Stankovic (2008), newly designed cannabis/filament hybrid yarns were used to produce knitted fabrics in order to investigate the effect of the internal structure of hybrid yarns on the compression behavior of clothing textile materials. By subjecting knitted fabrics to successive compression release cycles, it is possible to calculate certain compression parameters such as compression release curves, recoverable and irreversible compression. Using the parameters, inelastic deformation components (viscoelastic and plastic deformation) were determined.

Stankovic et al. (2008), the heat transfer properties of cannabis, cotton, and viscose-containing knitted fabrics were investigated. For this purpose, fabric porosity, air permeability, thermal conductivity, the thermal resistance of knitted fabrics with single jersey knit produced from cannabis, cotton, and viscose fibers alone or with their blends were examined. As a result of the experiments, the highest air permeability and the lowest thermal conductivity values were obtained in 100% cannabis fabrics, while the lowest air permeability and the highest thermal resistance values were obtained in 100% cotton fabrics. Hemp / Cotton and Hemp / Viscose blended fabrics showed intermediate values.

Ariyakuare (2010), in his research, obtained yarn by using fibers from waste cocoons together with cotton, flax, pineapple, ramie, and cannabis fibers, and by using these yarns in fabric structure suitable for home textiles, he investigated the performance properties. The test result of the new mixed fiber obtained from the waste cocoon used as weft yarn and the five types of plant fibers used as warp yarn in industrial weaving, the fiber obtained from the waste cocoon mixed with cannabis yarn has the best breaking strength with 194 CN / tex.

The results of the research showed that the fiber obtained from the waste cocoon mixed with cannabis yarn is suitable for producing home textiles as it has the highest tensile strength, while the fiber obtained from the waste cocoon mixed with pineapple yarn is suitable for producing clothes.

Cannabis Research Between 2010-2015

Miranda (2011) analyzed and compared cannabis and cotton fabrics that can be used in home textiles. It compared the performance characteristics of 100% cotton and 100% cannabis weaved fabrics with different weaves in terms of colorfastness to friction, colorfastness to light, dirt repellency, colorfastness to water, flame retardancy, abrasion resistance, tear strength, tensile strength, and elongation.

According to the results obtained, it has been shown that cannabis fabrics are comparable and superior to cotton fabrics in many parameters. According to these results, it has been stated that cannabis fabrics are an option that can be used in many products where cotton fabrics are used as upholstery fabrics.

Within the scope of Shahzad’s (2011 )’s study, it has been shown that cannabis fiber improves matrix interface adhesion, and thus, various fiber surface properties improve with the improvement of mechanical properties. In the study, it was stated that cannabis fibers have properties that make glass fibers a suitable material for use as reinforcement in composite materials. Its main disadvantages are stated to be variability in its properties.

Quiguang et al. (2011) investigated the production parameters of cannabis cotton blended combed vortex yarns with different blending ratios and production parameters. Hemp fibers are mechanically pretreated and softened. According to the findings obtained, it was stated that the optimum production was achieved at a yarn count of 21.6 tex. with a mixture of 40% cotton – 60% cannabis.

In the study, it was also stated that there are still aspects that are open to development for the strength, elongation, and unevenness properties of cannabis-containing yarns, and it is necessary to conduct researches on reducing production costs, conducting product development studies, and ensuring production efficiency.

Zhihai (2011) conducted research on the production line to spin yarn by blending cotton, cannabis, and bamboo fibers. The cannabis fibers were pre-treated, the fibers were treated with a softener and conditioned for 24 hours under production conditions. In the study, the blend feeding was performed in a controlled manner, by increasing the comb effect, the waste ratios were increased, and the shear distances were adjusted to the average fiber lengths.

At the end of the study, by blending 50% cotton – 25% cannabis – 25% bamboo, yarns with a thickness of 29.2 tex. were provided. It was stated that in order to meet the quality demand of cotton/cannabis/bamboo blended yarns, technological measures should be taken at every production stage, considering only the properties of cannabis fiber.

In the study conducted by Merdan et al. (2012), the breaking strength and elongation values of treated cannabis fibers were investigated by microwave method. In this study, cannabis fibers were treated with different concentrations of maleic anhydride using conventional and microwave methods.

When the tensile strength and breaking elongation values of untreated cannabis fibers were compared with the values obtained as a result of the microwave method, it was observed that the elongation values were less than the values of the untreated fiber compared to the conventional method, and the elongation values increased as the time continued to shorten. has been seen. It has been stated that the use of microwave energy in cannabis fiber surface treatments ensures optimum use of the chemical substance in a short time and the amount of water and energy used is less.

In the study by Hwang and Ji (2012), yarn count and liquid ammonia (L / A) treatment’s crystal structure, wrinkle, drying rate, washing shrinkage, roving speed, UV protection, and SEM morphologies of fine count hemp yarns and woven fabrics. Effects on physical properties have been investigated. 100% hemp woven fabrics with equal warp and weft counts used in the experiment were made of yarns of Nm 24, 36, 48, and 60 counts.

The fabrics were treated in liquid ammonia for 2 seconds under stress-free conditions at -33.4 ° C. As a result of the L / A process, the hemp fiber crystal structure was changed from cellulose I to blends of cellulose III and cellulose I, and the crystallinity was slightly reduced by 13%. The crease recovery of the hemp fabric treated with L / A is improved up to 78%, the washing shrinkage of the fabric is below 0.4%, while the washing shrinkage of the hemp fabric prepared with fine count yarn is made from hemp fabric prepared with coarse yarn. It has been observed to have better values.

It was observed that the wicking speed and drying rate of specially treated hemp fabrics were higher than the treated ones as the yarn number increased, but it was found that this treatment had no significant effect on UV protection.

Fuqua et al. (2012), the use of bio-based fibers as composite reinforcement material was investigated. The methods used to increase the interface of these fibers have been studied with various polymer matrices. The effects of textile processes on the creation of various fiber structures capable of reinforcement, processing methods of natural fiber-reinforced composites were discussed, and the correlation between structure, processing, and final composite properties was provided.

Marrot et al.’s (2013) ‘s research is to better understand the source of relatively poor hemp fiber mechanical properties and why they are dispersed. With this research, an original study was proposed by analyzing the hemp stalk, nano-indentation, fiber morphology and finally examining the relationship between fiber biochemical composition and mechanical performance. In the study, the morphologies of the fibers were analyzed; Thin cuts of the same hemp root sections were observed using an electronic and optical microscope.

To investigate the origin of the fiber stiffness propagation, stiffness measurements were made using the nanoindentation test on the kernel bodies, and X-ray diffraction (XRD) analysis of the fiber hemp crystallization was performed. Tensile tests were performed on manually extracted single hemp fibers to highlight the mechanical properties of hemp and compare them with literature data. In this study, it was demonstrated that these plant fibers used in the study of hemp fibers (Fedora 17 variety) showed variable and poor mechanical properties compared to flax fibers.

Various internal parameters have been investigated to explain this mechanical behavior. Strong differences in fiber and lumen morphology are highlighted, depending on their location in cross-section, and are probably due to the considerable distribution in the calculated tensile properties. As a result of the analysis tests, high lignification and strong middle lamellae can be noticed, which indicates that unbounded cannabis was used in the study and therefore the modification became more difficult.

In addition, for composite reinforcement, each pot defined in a correct application can meet the required specifications, increasing hemp performances using accurate pooling. As a matter of fact, the pooling process in water or raw makes it possible to remove some of the pectin and lignins found in the middle lamellae. It facilitates defibration, so this step becomes soft and the fibers are less damaged.

Dai et al. (2013) initially used oxidation/ultrasonication to produce nano-cellulose from hemp fibers. Subsequently, nano-cellulose was used as a “binding agent” to treat hemp fibers. The size distribution of the nano-cellulose was characterized by nanoparticle tracking analysis (NTA) and the morphologies of the nano-cellulose were defined by SEM and atomic force microscopy (AFM).

The mechanical properties and interfacial properties of modified natural fibers have been mainly studied. SEM and XRD were made to reveal the tensile strength increase mechanism of fibers by nano-cellulose modification. XPS and FTIR were made to investigate the surface properties of natural fibers covered with unsaturated polyester and to reveal the interface change mechanism and self-modification mechanisms.

The results show that the nano-cellulose developed by oxidation-sonication has a wider size range (29-283 nm) and average size (100-112 nm). Mechanical tests have shown that nano-cellulose modification can significantly improve the mechanical properties of natural fibers. The modulus and tensile of the nano-cellulose modified hemp fibers increased by 36.13%, 72.80%, and 67.89%, respectively. SEM and XRD have been used to reveal the mechanism of nano-cellulose reinforcement on natural fibers.

SEM showed that the nano-cellulose treatment resulted in an effective distribution of nano-cellulose along the line on the surface of the fibers, resulting in a significant increase in the tensile strength of the treated hemp fibers. XRD analysis also showed that the crystallinity index of processed fibers increased from 55.17% to 76.39%.

Mustata et al. (2013) examined how the water absorption-desorption process is affected by the spinning type (dry or wet) and the cottonization process of flax and hemp yarns. In addition, the electrical resistance of fibers and yarns in the wet and dry state and their mechanical properties after wetting and drying at room temperature, the effect of the amount of absorbed water on the electrical resistance, and mechanical properties of the fibers and yarns were investigated.

Hygroscopic properties of boiled or bleached fiber, yarn, and woven fabrics from flax and hemp were investigated at different relative humidity. It was stated that the saturation limit of the moisture absorption of the fibers changes depending on the source and the pretreatment applied. As a result of the study, it was observed that linen yarns obtained by dry spinning absorb more water with their high porosity properties compared to compact structured wet spun yarns.

For flax and hemp yarns, the degree of water absorption was found to depend on the moist duration, the finishing process applied to the fibers before spinning (boiling or bleaching), and the type of spinning (dry or wet). It was observed that flax and hemp yarns obtained by wet processing absorb more water than boiled and bleached fibers. It has been determined that flax and hemp fibers obtained by the wet spinning method have a lower water absorption rate.

It was observed that the tensile strength of flax and hemp yarns increased slightly as a result of the water absorption in the fibers compared to the dry ones. For flax yarns obtained from boiled and bleached fibers, it was stated that soaking at room temperature and subsequent drying had no effect on rupture strength. It was observed that the electrical resistance of flax and hemp fibers and yarns decreased about ten times in a wet state after 10 minutes of soaking.

In the study of Richardson and Zhang (2014), the effects of nonwoven hemp on mechanical properties and microstructural properties of phenolics were examined. A significant increase in bending resistance and modulus of phenolics was found with the addition of non-woven surface hemp. Impact toughness has been greatly improved. The reason for this has been stated as the restrictive effect of hemp fiber bundles on gap development and expansion. It has been observed that the presence of cannabis has the ability to reduce the number and size of voids (defects) that significantly contribute to the improvement in mechanical properties.

Stankovic et al. (2014) investigated the effects of folding on yarns produced from hemp fibers on the thermal and attitude comfort properties of flat knitted fabrics. In addition, structural properties, transfer properties, deformation behavior, and surface properties of hemp knitted fabrics were investigated. As a result, it has been observed that the use of hemp yarns by folding has positive effects on the thermal and handle properties of knitted fabrics, and it improves air permeability and water vapor permeability thanks to the increase in the yarn density and the smooth distribution of the pores.

Factors affecting the smoothness properties, mechanical properties, and structural properties of blended yarns with different hemp content were analyzed by Zhang et al. (2014) and the regression equation between the blend ratio and yarn mechanical property was investigated. Based on this equation, blended yarns were produced in different proportions using polyester, hemp, and cotton fibers in the experiment.

When the results were examined, it was observed that the unevenness of the hemp blended yarn increased as the hemp fiber ratio increased in the yarn. At the same time, hemp fiber, in addition to its hardness, has a greater fiber length, greater initial modulus, irregular fiber cross-section, and greater surface friction than polyester and cotton, so its distribution in the yarn is greatly influenced by the content.

It has been observed that the mechanical properties of hemp fibers are affected by their distribution in the yarn, and because of their smooth surfaces and low cohesion force, they are easy to slip from each other, although they have high strength when stretched. It has also been observed that when hemp fiber is mixed with polyester and cotton in certain proportions, its adhesive strength increases again under the effect of twisting.

Cannabis Research Between 2015-2020

Seki et al. (2017) studied the physical and chemical properties of vegetable fibers by modifying vegetable fibers used as composite materials in order to investigate and improve the usability of cellulose-based fibers as reinforcement material. Within the scope of the studies carried out, the common vegetable fibers such as flax, jute, banana, hemp, sisal, and coconut fibers, which are widely used as composite materials, were modified with alkali, the contents of the fibers were analyzed and their chemical properties were analyzed with FTIR and morphological properties with SEM and fluorescence microscopy.

When the findings obtained in the study were examined, it was determined that the cleaning effect occurred on the surface of the fiber as a result of the alkali treatment, the non-cellulosic components in the fiber decreased, the fluorescent color given changed due to the change in the fiber content and the fiber surface became rough.

In the study of Paulitz et al. (2017), the results of the national network project focused on the development of an integrated process chain for the production of new fabrics produced from lyocell fibers obtained from organically grown hemp were examined. The whole process line is starting from hemp cultivation, machine-assisted harvesting, and automatic peeling, to separating the hemp strips from the stalks, was established within the scope of the process works that started with wet spinning until yarn production, dyed, and finished fabrics.

The fibers produced show similar properties in terms of fineness, tensile strength, elongation, and elasticity as common lyocell fibers made from conventional pulp. The project consortium has developed innovative processes and machines for harvesting and integrated processing of organically grown hemp. Hemp bast ribbons are produced from mechanically peeled hemp hulls. It has been stated that woody pieces of hemp can be transformed into innovative composite materials.

Antony et al. (2018) examined the strength properties of hemp yarns by experimental, analytical, and numerical analysis. First, samples were prepared with warp and weft yarns separated from woven fabrics in direct taffeta and bilge knits, and tensile tests were carried out to characterize the mechanical properties of the twisted yarn. Analytical analysis was performed to predict the mechanical behavior of hemp fiber yarns under tensile load.

Experimental tensile tests were performed at different yarn orientation angles. A mathematical yarn behavior model has been proposed, taking into account the fiber curl, elasticity, and damage phenomena, in line with the law of probability. 3D reconstructed CAD images of each warp and weft yarn and numerical simulations of their mechanical behaviors were performed.

The simplex reverse optimization approach was combined in numerical analysis to optimize the material properties of hemp yarn, and a reverse optimization approach was adopted to numerically optimize the mechanical properties of yarns. The proposed model is also validated at tensile loads of yarns in different directions. It was stated that the proposed method could be used in later studies to characterize fabric behavior.

Cannabis Research in General

Nowadays, in their studies on cannabis, researchers have made it the aim of both evaluating the cannabis plant according to its characteristics and developing new production methods. Because they have observed that cannabis fibers, when mixed with cotton and similar raw materials, enable the production of more durable yarns and the yield per unit area is high.

For this reason, cannabis fiber is in a competitive position against synthetic fibers, glass fibers, and many fibers. In fact, the fact that cannabis fiber is lighter than glass fiber in usage areas gives cannabis a priority, especially in the heat and sound insulation. Hemp, which has a similar structure and cross-section with synthetic fibers, has comparability with synthetics in terms of durability and stability. For this reason, simpler and mass production methods such as synthetics in cannabis fiber and yarn production should be developed to make cannabis more widespread and usable.

In this way, it will be possible to pave the way for new markets and employment areas. Due to the superior ecological properties of cannabis fiber, it is expected that there will be a significant increase in the production-consumption band of cannabis products in the coming years due to the organic textile production potential and good textile performance properties.

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Savaş Ateş

I like cannabis. I read a lot about cannabis usage in the medical field. I researched a lot about planting it. I have started a cannabis business and i want to share my experiences with you.

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