With respect to fiber, a “composite” is often defined as a material consisting of 30%–70% fiber and 70%–30% matrix (Bolton 1995). However, in North America particleboards and fiberboards, which generally contain less than 10% adhesive or matrix, are sometimes referred to as composites. This section addresses plastic-type composites. In plastics, fibers are introduced to improve physical properties such as stiffness, impact resistance, bending and tensile strength. Man-made fibers of glass, kevlar and carbon are most commonly used today, but plant fibers offer considerable cost savings along with comparable strength properties.
The Cannabis plant has a history of medicinal use dating back thousands of years across many cultures. The Yanghai Tombs, a vast ancient cemetery (54 000 m2) situated in the Turfan district of the Xinjiang Uyghur Autonomous Region in northwest China, have revealed the 2700-year-old grave of a shaman. He is thought to have belonged to the Jushi culture recorded in the area centuries later in the Hanshu, Chap 96B. Near the head and foot of the shaman was a large leather basket and wooden bowl filled with 789g of cannabis, superbly preserved by climatic and burial conditions. An international team demonstrated that this material contained tetrahydrocannabinol, the psychoactive component of cannabis. The cannabis was presumably employed by this culture as a medicinal or psychoactive agent, or an aid to divination. This is the oldest documentation of cannabis as a pharmacologically active agent.
"Hemp oil is extremely nutritious, and is used in foods and nutraceutical products for humans and animals, as well as in personal care products. Hemp oil is also suitable for use in industrial products such as paints, varnishes, inks and industrial lubricants, and can be used to produce biodiesel. The crushed seed meal left over from oil production is frequently used for animal feed."
The genus Cannabis was formerly placed in the nettle (Urticaceae) or mulberry (Moraceae) family, and later, along with the genus Humulus (hops), in a separate family, the hemp family (Cannabaceae sensu stricto). Recent phylogenetic studies based on cpDNA restriction site analysis and gene sequencing strongly suggest that the Cannabaceae sensu stricto arose from within the former family Celtidaceae, and that the two families should be merged to form a single monophyletic family, the Cannabaceae sensu lato.
In the United States, the public's perception of hemp as marijuana has blocked hemp from becoming a useful crop and product," in spite of its vital importance prior to World War II. Ideally, according to Britain's Department for Environment, Food and Rural Affairs, the herb should be desiccated and harvested towards the end of flowering. This early cropping reduces the seed yield but improves the fiber yield and quality. In these strains of industrial hemp* the tetrahydrocannabinol (THC) content would have been very low.
^ Russo, E. B.; Jiang, H.-E.; Li, X.; Sutton, A.; Carboni, A.; Del Bianco, F.; Mandolino, G.; Potter, D. J.; Zhao, Y.-X.; Bera, S.; Zhang, Y.-B.; Lü, E.-G.; Ferguson, D. K.; Hueber, F.; Zhao, L.-C.; Liu, C.-J.; Wang, Y.-F.; Li, C.-S. (2008). "Phytochemical and genetic analyses of ancient cannabis from Central Asia". Journal of Experimental Botany. 59 (15): 4171–82. doi:10.1093/jxb/ern260. PMC 2639026. PMID 19036842.
The use of cannabis for pain relief dates back to ancient China, according to a report published in the journal Cannabis and Cannabinoid Research. It’s thought that CBD oil might help ease chronic pain in part by reducing inflammation. In addition, CBD oil is said to promote sounder sleep and, in turn, treat sleep disruption commonly experienced by people with chronic pain.
"Whereas fibres and shivs did not show any significant difference between 2010 and 2013, the production of seeds increased by 92% and the production of flowers and leaves by 3,000%. The flowers for CBD production gave hemp farmers a considerable extra profit in 2013. It should also be mentioned that hemp is one of the very few crops in Europe that is cultivated on non-organic farms without the use of any agrochemicals. Strong, fast growing hemp crops are able to supress weeds without chemical support and the crop does not suffer from any pests or diseases that would warrant a spray. Hemp also grows well under an organic regime."
And without high-quality trials, experts don’t know how much is best for a given purpose. The staff at Roth’s dispensary told her, “Try some once or twice a day and see what happens.” (Half a dropper’s worth was a good amount for her.) One thing scientists feel confident about is that CBD is not dangerous. It won’t damage vital organs even at doses as high as 5,000 mg a day, Marcu says, and nobody has died from simply overdosing on a cannabis product.
Another claim is that Mellon, Secretary of the Treasury and the wealthiest man in America at that time, had invested heavily in DuPont's new synthetic fiber, nylon, and believed[dubious – discuss] that the replacement of the traditional resource, hemp, was integral to the new product's success. The company DuPont and many industrial historians dispute a link between nylon and hemp, nylon became immediately a scarce commodity.[clarification needed] Nylon had characteristics that could be used for toothbrushes (sold from 1938) and very thin nylon fiber could compete with silk and rayon in various textiles normally not produced from hemp fiber, such as very thin stockings for women.
The first of Berenson’s questions concerns what has long been the most worrisome point about cannabis: its association with mental illness. Many people with serious psychiatric illness smoke lots of pot. The marijuana lobby typically responds to this fact by saying that pot-smoking is a response to mental illness, not the cause of it—that people with psychiatric issues use marijuana to self-medicate. That is only partly true. In some cases, heavy cannabis use does seem to cause mental illness. As the National Academy panel declared, in one of its few unequivocal conclusions, “Cannabis use is likely to increase the risk of developing schizophrenia and other psychoses; the higher the use, the greater the risk.”