20.01.2015
School of Chemistry & Chemical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China.
The raw materials for photo-curing technology such as monomer resins, photo-initiators and functional additives, are usually produced from fossil oil. Vegetable oils are inexpensive, environmentally friendly, renewable, naturally raw materials with low toxicity and functional groups such as hydroxy, epoxy, carboxyl and CC. Vegetable oils consist of mainly triglycerides formed between glycerol and various fatty acids, which have a three-armed star structure (Figure 1.1). Because the internal double bonds in the triglyceride structure are not sufficiently reactive for various polymerization processes, the vegetable oils must be modified with efficient photo-polymerizable groups such as acrylate or epoxy when being used as photo-curing monomers.
Most of the multifunctional epoxy monomers for photo-curing based on vegetable oils are prepared from the epoxidation of unsaturated fatty acids or triglycerides. This process is performed industrially on large scale, and more research is currently focusing on how to improve the conversion rate.28 An epoxidation reaction of mahua oil using hydrogen peroxide was done by Goud et al. The catalytic epoxidation of methyl linoleate with different transition metal complexes as catalysts was studied by Woo's group. The double bonds present in vegetable oils can be transformed into acrylate groups through two steps, then the acrylated vegetable oils can be used as a binder in fast UV-curable coating mixtures.
Esterification of hydroxylated vegetable oils using acrylic acid or acryloyl chloride is another efficient method for the preparation of acrylated vegetable oils for UV-curing. Epoxidized vegetable oils can be reacted with polyhydric alcohols to prepare vegetable-oil-based polyols. Acrylate moieties have also been attached to triglyceride structures by the one-step addition of bromide and acrylate groups to a CC bond.
The Patel group54 has synthesized a series of UV-curable polyurethane acrylate pre-polymer monomers by reacting polyols from sesame oil (edible) and using different ratio of polyols, aromatic isocyanate, and aliphatic isocyanate, 2-hydroxy ethyl methacrylate (HEMA) and dibutyltin dilaurate (DBTDL) as the catalyst.
Photo-curing formulations are usually comprised of multifunctional monomers and oligomers, with small amounts of a photo-initiator which generates reactive species (free radicals or ions) upon UV exposure.
Many researchers pay attention to the chemistry behind the photo-curing process, and especially the photo-curing kinetics of ultrafast reactions for both cationic-type and radical-type polymerization of the multifunctional monomers from vegetable oils. The cross-linking mechanism (Figure 1.12)9,62,69 was investigated in detail, and the formation of the lipidic network was attributed to the successive formation of radical species, isomerization, hydroperoxidation and cross-linking. Acrylated resins are the most widely used photo-curing systems, because of their high reactivity and the variety of available monomers and telechelic oligomers.
Wuzella et al.48 have studied the kinetic properties of acrylated epoxidized linseed oil monomers by UV-curing. Bio-degradable photo-cross-linked thin polymer networks based on acrylated hydroxy fatty acids have been reported. Multifunctional epoxide monomers can be converted into highly cross-linked polymer networks by UV irradiation in the presence of cationic photo-initiators. The Soucek group75 have reported the preparation and photo-polymerization of cyclohexene-derivatized linseed oil (CLO) and epoxycyclohexene-derivatized linseed oil (ECLO). Ortiz's group studied the acceleration effect of substituted benzyl alcohols on the cationic photo-polymerization rate of epoxidized natural oils.78 The Crivello group described the effect of the structure of both the cation and anion of diaryliodinium and triarylsulfonium photo-initiators on the polymerization rate of epoxidized triglycerides as renewable monomers. The unsaturated nature of triglycerides obtained from vegetable oils make them good candidates for thiol-ene coupling. Many works focusing on UV-curable systems based on monomers derived from vegetable oils have been reported,93–95,101 but UV-curable systems based on maleates, fumarates and acrylates have not been widely studied.
Because of flexible thioether linkages and the inherent disadvantages of vegetable oil, it is difficult to obtain cross-linked materials with hardness, toughness and high glass-transition temperatures.
Due to their special structure and bio-compatibility, some vegetable oil derivates can be used as functional additives in resin formulations. ChemStream, an innovative chemicals R&D company and a member of FISCH (Flanders Innovation Hub for Sustainable Chemistry) specialises in translating material challenges into chemical formulations in order to then develop and implement sustainable solutions.
In the search for sustainable industrial processes, UV curing technology (curing utilising ultra violet radiation) is noticeably gaining an increasingly important place in different coating and printing applications.
The wide range of substrates on which the UV coatings can be applied and the diversity in physical properties (from rigid to flexible layers) are also reflected in the range of chemical formulations that ChemStream has designed specifically for each client.
In 2013, ChemStream launched its innovative BlockDrop product line of water-absorbing UV-cured coatings with water-blocking properties.
Traditional biological waste streams (such as insect and crustacean shells) can be converted into high-quality chemical building blocks, thanks to white biotechnology. Model of the chitin deacetylase enzyme that converts insect and crustacean shells, amongst other things, into high-quality chemical building blocks. The sustainable building blocks can then be applied in a variety of material contexts as (biodegradable) dispersants, emulsifiers and encapsulators. The majority of R&D projects are carried out within a European context, both bilaterally and in collaboration with SMEs and knowledge institutions. A number of specific products were tested in a European context (coatings that can be removed by plasma to protect cultural legacy), in China (functional coating as part of the Oled (organic light-emitting diode) fabrication process) and in Sri Lanka (new textile applications).
Frank De Voeght – Managing Director of ChemStream: “Due to their flexibility and streamlined structure, SMEs play an important role to provide the innovation process with the very best chance of success. The SAF-T-CURETM STANDARD UV FACE SHIELD provides 100% face protection from exposure to the full UV spectrum (200-405nm), and from accidental splashes of harmful liquids. Note: Additional Safety data is available in the "Download Support Documents" on the left of this page. Man is reported to have been aware since early antiquity of the substance we now know as vitamin D. Considering the fact that now we accept that the biologically active form of vitamin D, namely 1a,25(OH)2-vitamin D3, is a steroid hormone, it is somewhat ironic that vitamin D, through a historical accident, became classified as a vitamin. The chemical structures of the vitamins D were determined in the 1930s in the laboratory of Professor Adolf Otto Reinhold Windaus at the University of Gottingen in Germany. Vitamin D2 which could be produced by ultraviolet irradiation of ergosterol was chemically characterized in 1932. A "vitamin" by definition is a substance regularly required by the body in small amounts but which the body cannot make and is, therefore, required to be supplied in the daily diet. The World Health Organization had responsibility for defining the "International Unit" of vitamin D3.
Since vitamin D3 can be endogenously produced by the body and since it is retained for long periods of time by vertebrate tissue, it is difficult to determine with precision the minimum daily requirements for this seco-steroid. In November of 2010, , the Institute of Medicine's (IOM) special committee of 15 experts from the US and Canada issued its report for the citizens of both countries defining the formal Dietary Reference Intakes (average daily doses) of vitamin D and calcium required for good health.
In the United States, adequate amounts of vitamin D can readily be obtained from the diet and from casual exposure to sunlight. For decades since the determination of the chemical structures of vitamin D3 and vitamin D2 in the 1930's it has been assumed that both vitamins had equivalent biological activity in humans. Thus the authors felt that given the greater potency and lower cost, vitamin D3 should be the preferred choice for correcting vitamin D deficiency in humans.
Animal products constitute the bulk source of vitamin D that occurs naturally in unfortified foods.
Subcommittee on the Tenth Edition of the RDAs, Food & Nutrition Board, Commission on Life Sciences and National Research Council. The structures of vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) and their provitamins are presented in Figure 1 on the right.
Vitamin D (calciferol) is named according to the revised rules of the International Union of Pure and Applied Chemists (IUPAC). Vitamin D3 can be produced photochemically by the action of sunlight or ultraviolet light from the precursor sterol 7-dehydrocholesterol which is present in the epidermis or skin of man and most higher animals. Structural relationship of vitamin D3 (cholecalciferol) and vitamin D2(ergocalciferol) with their respective provitamins, cholesterol, and a classic steroid hormone, cortisol (see inset box).
Photochemical pathway of production of vitamin D3 (cholecalciferol) from 7-dehydrocholesterol. A detailed study of the biochemical mode of action of the fat-soluble vitamin D was not possible until the availability in the 1960s of preparations of high specific activity radioactive vitamin D. As summarized in the figure on the left, the existence of the vitamin D endocrine system is now firmly established.
An additional key component in the operation of the vitamin D endocrine system is the plasma vitamin D binding protein (DBP) that carries the hydrophobic vitamin D3 and all of its metabolites through the circulatory system to their various target organs.
Since 1971, research efforts have largely focused upon understanding how 1a,25(OH)2D3 generates biological responses.
Thus, vitamin D3 is, in reality, a prohormone and is not known to have any intrinsic biological activity itself. The key kidney enzymes, the 25(OH)D3-1-hydroxylase and the 25(OH)D3-24-hydroxylase, as well as the liver vitamin D3-25-hydroxylase, are all known to be cytochrome P-450 mixed-function oxidases. The most important point of regulation of the vitamin D endocrine system occurs through the stringent control of the activity of the renal 1-hydroxylase. 1a,25(OH)2D3working with its VDR is known to selectively activate ? 3% of the some 22,000 genes of the human genome. As a consequence of the significant scientific advances in the understanding of how vitamin D generates biological responses [principally via 1a,25(OH)2D3], a number of new drug forms of 1a,25(OH)2D3 have been generated by pharmaceutical companies.
The objective of this presentation is to provide a brief descriptions of vitamin D's chemistry, nutritional importance, sources, production and presence in milk.
A vitamin is a substance (a specific organic molecule) whose presence is crucial to the normal every day life and functions of animals.
A hormone is a chemical messenger that is produced and secreted by specific glands and cells within the body of animals. Chemistry: There are two chemical forms of vitamin D, namely vitamin D2 (sometimes referred to as ergocalciferol) and vitamin D3 (sometimes referred to a cholecalciferol). The molecular structure of vitamin D is closely allied to that of the classical steroid hormones, e.g. Technically the molecule called vitamin D3 is not really a vitamin because it can be produced by exposure of the skin (higher animals and humans) to ultraviolet light or sunlight.
Therefore for nutritional and public health reasons, vitamin D3 continues to be classified even today in 2012 officially as a vitamin.
It has become increasingly apparent since the 1980s that 1a,25(OH)2D3 also plays an important multidisciplinary role in tissues not primarily related to mineral metabolism, e.g. Vitamin D Deficiency: The classic deficiency state resulting from a dietary absence of vitamin D3 or lack of ultraviolet (sunlight) exposure is the bone disease called rickets in children or osteomalacia in adults. Since vitamin D3 is produced in the skin after exposure of 7-dehydrocholesterol to sunlight, the human does not have a requirement for vitamin D when sufficient sunlight is available. Since vitamin D3 can be produced by the body and since it is retained for long periods of time by animal tissues, it has been difficult to determine with precision the minimum daily requirements for this fat soluble vitamin. Animal products constitute the primary source of vitamin D that occurs naturally in unfortified foods.
When the critical importance to human health of a regular dietary access to vitamin D3 was understood (in the 1930's), milk suppliers realized it would be advantageous to their customers' health to market milk which had been supplemented with vitamin D3. In 1973 in the United States some 290 trillion (290 x 10-12) International Units of vitamin D3 was manufactured and sold for over 3 million dollars. The commercial production of vitamin D3 is completely dependent on the availability of either 7-dehydrocholesterol or cholesterol. Next the crystalline 7-dehydrocholesterol is dissolved in an organic solvent and irradiated with ultraviolet light to carry out the transformation (similar to that which occurs in human and animal skin) to produce vitamin D3.
Historically, the major producers of vitamin D3 used for milk and other food supplementation were the companies F. Milk from all lactating animals, including humans, contains vitamin D3 that has been produced photochemically from 7-dehydrocholesterol present in the skin.
If a "food product" is construed to include a chemically pure substance that is the same in all animal species, then those individuals with strict religious reasons for avoiding food products from a particular species have, in the instance of milk and vitamin D3, a dilemma.
Also the WEB sites for the Vitamin D Workshop and provides other general information related to vitamin D. Sun Chemical, en son gelistirdigi organik UV kurlenen murekkep ile cama direkt bask? teknolojisini Glasstec 2012 fuar?nda gorucuye c?kard?. Soz konusu cam bardak SunChemical’?n SunVetro® serisindeki, inorganic murekkeplerle yap?lamayacak sekilde parlak ve guclu renkler bas?lmas?n? saglayan, Vitrocure UV curing murekkebini kullan?yor. POLYQuik floor coatings offer excellent abrasion, corrosion, and UV and chemical resistance.
Concrete curing means controlling the rate and extent of moisture loss from concrete during the first twelve hours so that the concrete can achieve its potential strength and durability.
Concrete that dries out too quickly may not retain enough water for the hardening process, a chemical reaction called hydration. There are many considerations we take into account before selecting the right curing method for a given job.
The CC double bond reactive positions are usually used as the starting points for introducing highly efficient reactive groups. The reaction is active and usually happens at low temperatures, which may minimize side-reactions such as the homopolymerization of acrylate monomers. Polyols were prepared via the alcoholysis of triglyceride oil using a proprietary method, which was further reacted with toluene diisocyanate and isophorone diisocyanate in different ratios to develop a series of polyurethanes (Figure 1.10).


The high rate of unsaturation of these vegetable oils makes them sensitive to auto-oxidation under air. They found that the photo-initiator affects both the reaction rate and the final double-bond conversation. Higher functionalities of polyols, aromatic-type isocyanates, and lower oil ratios lead to poor adhesion and flexibility performance. Di- and trimethacrylates,71 or acrylated oligomers such as acrylated-PEG (polyethylene glycol) or acrylated-poly(?-caprolactone) were used in co-polymerization. It may provide potential opportunities to synthesize polymer materials from renewable resources by a clean and simple process that is totally transposable to lesser drying oils. The structures of CLO and ECLO and the photo-polymerization kinetics are shown in Figure 1.16. 1.17 (a) Effect of the reactive diluent, DEGDVE (diethylene glycol divinyl ether), on the epoxy ring-opening polymerization of ENLO-100 (epoxy norbornane linseed oils) in the presence of 4 wt% OPPI as a function of the irradiation time. Rawlins’ group101 reported the synthesis of thiol-ene UV-curable coatings based on vinyl ether, allyl, acrylate and derivatives of castor oil together with a multifunctional thiol. The mechanical properties of the polymer networks produced, resemble those of elastomeric materials. Additionally, the typically unpleasant odors of low-molecular-weight thiols have also limited their commercial utilization.
The photochemical process behind UV curing enables the production process to be carried out at higher speeds using less energy, without releasing VOCs (volatile organic compounds).
Even substrates that are difficult to coat because of splitting and bonding can be finished using an in-line plasma treatment with a modified UV formulation.
Until recently, loose slush powder (superabsorbent polymers) was still mixed into coating compositions such as Plastisol (PVC), which creates dust in the production environment and formulations that are not environmentally friendly because it requires the use of phthalates. The sustainability of the process workflows can be maximised in specification situations by introducing new, tailor-made chemical building blocks in the chemical formulations. As a result, they form interesting secondary streams that deliver new raw materials thanks to the symbiosis of enzymatic biocatalysis and "classic organic chemistry". ChemStream works in partnership with Swedish textile companies in the field of digital functioning of textile substrates, and is involved with different European consortia (including Italy, Germany and Bulgaria) in the development of new, innovative coatings and building blocks. They consist of a lightweight plastic head piece and a durable, injection-molded, polycarbonate lens. The first scientific description of a vitamin D-deficiency, namely rickets, was provided in the 17th century by both Dr.
McCollum and associates observed that by bubbling oxygen through a preparation of the "fat-soluble vitamin" they were able to distinguish between vitamin A ( which was inactivated) and vitamin D (which retained activity). Professor Windaus had some 55 doctoral and postdoctoral chemists working on the 'vitamin D project'.
Vitamin D3 was not chemically characterized until 1936 when it was shown to result from the ultraviolet irradiation of 7-dehydrocholesterol. The induction of growth promoting and calcifying properties in a ration by exposure to light. Technically the molecular species classified as vitamin D3 is not really a vitamin because it can be produced by exposure of the skin to sunlight (see section on Chemistry).
Their most recent definition, provided in 1950 states that "the International Unit of vitamin D recommended for adoption is the vitamin D activity of 0.025 micrograms (25 nanograms) of the international standard preparation of crystalline vitamin D3". Since vitamin D3 is produced in the skin after exposure to sunlight, the human does not have a requirement for vitamin D when sufficient sunlight is available.
The requirement for vitamin D is also known to be dependent on the concentration of calcium and phosphorus in the diet, the physiological stage of development, age, sex, degree of exposure to the sun, and the amount of pigmentation in the skin. Their recommendation for vitamin D is that from ages 1 to 70, people need to consume no more than 600 International Units (IU) per day. However, in some parts of the world where food is not routinely fortified and sunlight is often limited during some periods of the year, obtaining adequate amounts of vitamin D becomes major problem. This was based on biological determination in rats of their comparative antirachitic activity. Heaney and coworkers it was reported that vitamin D3 is approximately 87% more potent in raising and maintaining serum 25(OH)D levels than was vitamin D2. Salt water fish such as herring, salmon, sardines, and fish liver oils are good sources of vitamin D3. From Vitamin D to hormone D: Fundamentals of the vitamin D endocrine system essential for good health. Vitamin D is a generic term and indicates a molecule of the general structure shown for rings A, B, C, and D with differing side chain structures. Because vitamin D is derived from a steroid, the structure retains its numbering from the parent compound cholesterol. The chief structural prerequisite of a provitamin D is that it be a sterol with a D5,7 diene double bond system in ring B (Figure 2 to the left).
Identification and characterization of noncalcemic, tissue-selective, nonsecosteroidal vitamin D receptor modulators J.
Degradation chemistry of a Vitamin D analogue (ecalcidene) investigated by HPLC-MS, HPLC-NMR and chemical derivatization J. The starting point is the irradiation of a provitamin D, which contains the mandatoryD5,7-conjugated double bonds; in the skin this is 7-dehydrocholesterol. As a consequence of efforts in several laboratories a new model emerged in the late 1960’s to describe the biological mechanisms of action of vitamin D3.
From 1960 – 2021approximately 25,000 scientific papers were published that used the term vitamin D either in the title or abstract. Both of the renal enzymes are localized in mitochondria of the proximal tubules of the kidney. In this way the production of the hormone 1a,25(OH)2D3 can be modulated according to the calcium and other endocrine needs of the organism.
The regulation of gene transcription by 1a,25(OH)2D3 is known to be mediated by interaction of this ligand with its personal nuclear receptor protein, termed the VDR. Over the past decade, four lines of investigation have collectively yielded striking new insights into the many newly appreciated actions of vitamin D. The table below summarizes these new drugs and the relevant pharmaceutical company, and identifies the clinical circumstance for which their use has been authorized.
This will first require a review of the biological and nutritional background on vitamin D, which is a precursor of a steroid hormone [1a,25(OH)2D3] in higher animals, including humans.
After secretion of the hormone, it is transported through the bloodstream to designated target organs where the hormone by binding to its specific personal receptor delivers its "message" to that set of cells. The natural form of vitamin D for animals and man is vitamin D3; it can be produced in their bodies from cholesterol and 7-dehydrocholesterol. The skin of many animals and man has a high concentration of the sterol cholesterol which is converted by enzymes in the skin to the sterol 7-dehydrocholesterol.
Thus many vitamin capsules and food sources including cows milk are supplemented with vitamin D3 to improve their nutritional value. Classically vitamin D3 has been shown to be one of the most important biological regulators of calcium metabolism through stimulating the absorption of calcium from food across the intestine and participating in the incorporation of the absorbed calcium into the skeleton (2). Man's tendency to wear clothes, to live in cities where tall buildings block adequate sunlight from reaching the ground, to live indoors, to use synthetic sunscreens that block ultraviolet rays, and to live in geographical regions of the world that do not receive adequate sunlight, all contribute to the inability of the skin to biosynthesize sufficient amounts of vitamin D3 (5). The requirement for vitamin D3 is also known to be dependent on the age, sex, degree of exposure to the sun, season, and the amount of pigmentation in the skin (8). The ultraviolet exposure can be as little as 3 X per week exposure of the face and hands to ambient sunlight for 20 minutes (10). Thus there developed in the 1940's, and continues to the present, a large business of industrial production of vitamin D3 used for the supplementation of foods for human consumption: milk (both homogenized and evaporated), some margarine and breads. 7-Dehydrocholesterol can be obtained via organic solvent extraction of animal skins (cow, pig or sheep) followed by an extensive purification. This vitamin D3 is then purified and crystallized further before it is formulated for use in dairy milk and animal feed supplementation.
In cow's milk it has been determined that the concentration of vitamin D3 in milk provided by the cow is roughly 35-70 International Units per quart as determined via biological assay (12) and approximately 50-80 International Units as determined by modern chemical mass spectrometric procedures (13). An evaluation of the relative contributions of exposure to sunlight and of diet to the circulating concentrations of 25-hydroxyvitamin D in an elderly nursing home population in Boston. Dietary reference intakes: A risk assessment model for establishing upper intake levels for nutrients. Vitamin-D synthesis and metabolism after ultraviolet irradiation of normal and vitamin-D-deficient subjects. Cam bardak uzerine yap?lan bask? ile UV organik murekkepleri ile gelistirilebilecek yuksek kalitede bask? efektleri tan?t?l?rken, markalar?n ambalaj tasar?m? konusunda art?k daha yenilikci olabilecekleri de kan?tlanm?s oldu.
Sun Chemical Industrial Inks Avrupa Pazarlama Muduru olan Robin McMillian, “Bu bask?l? cam ornegi ile markalar?n UV curing murekkeplerinin kullanarak ulasabilecekleri paketleme kalitesi ve cesitliligini gorebiliyoruz.
These rapid-curing coatings offer quick turnaround times resulting in substantial savings in both application time and labor costs. Their competitive cost, worldwide availability, and built-in functionality make them attractive. The reaction proceeds via the enzymatic in situ formation of the peracids required for the chemical epoxidation of the double bonds. The naturally occurring hydroxyl groups in castor oil are usually used to attach polymerizable acrylic moieties, by reacting castor oil with acryloyl chloride. The final degree of the polymerization and the physical and chemical properties of the photo-curing polymers are determined by the chemical structure and functionality of both the monomer and the oligomer. Also, the aromatic nature of the isocyanate moiety further enhances the film hardness and toughness. A fundamental research study on photo-initiators was described for the case of the cationic photo-polymerization of triglycerides. The most important feature of the reaction was the influence of the number of double bonds per chain in the vegetable oil on the thiol grafting yield. The films exhibited high solvent resistance and hardness as well as excellent adhesion and flexibility.
The materials exhibited a flexural modulus in the 240–340 MPa range and glass-transition temperatures below room temperature.
By responding to the nature of the chemical components (monomers and photoinitiators) that can be utilised in the coating and ink formulations, a whole range of various functionalities can be realised in the cured layers. That is why ChemStream is working on a new, pioneering product range by making both chemical and biochemical modifications to natural building blocks. In 1921 he wrote, "The action of fats in rickets is due to a vitamin or accessory food factor which they contain, probably identical with the fat-soluble vitamin." Furthermore, he established that cod liver oil was an excellent antirachitic agent.
In 1923 Goldblatt and Soames clearly identified that when a precursor of vitamin D in the skin (7-dehydrocholesterol) was irradiated with sunlight or ultraviolet light, a substance equivalent to the fat-soluble vitamin was produced. Professor Windaus received a Nobel Prize in Chemistry in 1928 for his work on sterols and their relationship to vitamins. Virtually simultaneously, the elusive antirachitic component of cod liver oil was shown to be identical to the newly characterized vitamin D3.
A study of rats on a normal diet irradiated daily by the mercury vapor quartz lamp or kept in darkness. However, for nutritional and public health reasons, vitamin D3 continues to be classified officially as a vitamin (see section on History of Vitamin D).
The 13th and 14th Vitamin D Workshops reported in white papers that two thirds of the world population has a vitamin D deficiency.
However in 1997, the IOM vitamin D reference intake publication for vitamin D, serum 25-hydroxyvitamin D [25(OH)D], rather than antirachitic activity, was defined as the functional indicator of vitamin D status. In addition, vitamin D3 produced a 2- to 3-fold greater storage of vitamin D than does equimolar D2. Small quantities of vitamin D3 are also derived from eggs, veal, beef, butter, and vegetable oils while plants, fruits, and nuts are extremely poor sources of vitamin D.
The A, B, C, and D ring structure is derived from the cyclopentanoperhydrophenanthrene ring structure for steroids.
Asymmetric centers are designated by using the R,S notation; the configuration of the double bonds are notated E for "entgegen" or trans, and Z for "zuzammen" or cis. The conjugated double bond system in this specific location of the molecule allows the absorption of light quanta at certain wavelengths in the UV range; this can readily be provided in most geographical locations by natural sunlight (or UV-B). It is to be emphasized that vitamin D3 is the naturally occurring form of the vitamin; it is produced from 7-dehydrocholesterol, which is present in the skin, by the action of sunlight (see Figure 2). After absorption of a quantum of light from sunlight (UV-B), the activated molecule can return to the ground state and generate at least six distinct products.
This model is based on the concept that, in terms of its structure and mode of action, vitamin D is similar to the classic steroid hormones, e.g. The chief regulatory factors are 1a,25(OH)2D3 itself, parathyroid hormone (PTH), and the serum concentrations of calcium and phosphate. Target organs and cells for 1a,25(OH)2D3 by definition contain nuclear receptors for 1a,25(OH)2D3 (VDRnuc). Accordingly, the daily requirements for each vitamin must be met through regular dietary intake of appropriate quantities of the vitamin(s).


An alternative vitamin D2 is commercially prepared from ergosterol that is present in yeast. All steroid hormones and vitamin D3 are chemically related to the well known sterol cholesterol. Exposure of skin (including human skin) to sunlight for regular intervals results in the photochemical conversion of 7-dehydrocholesterol into vitamin D3. In the 1940's this milk supplementation process reduced the incidence rate of juvenile rickets by 85% in the United States. These important biological effects are only achieved as a consequence of the metabolism of vitamin D into a family of daughter metabolites, including 1a,25(OH)2-vitamin D3 [1a,25(OH)2D3]. The classical skeletal disorder of rickets includes deformity of the bones, especially in the knees, wrists, and ankles, as well as associated changes in the rib joint functions, which have been termed by some as the rachitic rosary (1). These recommendations are all summarized in a 2010 publication from the Food and Nutrition Board of the Institute of Medicine (9). However, in some parts of the world where food is not routinely fortified and sunlight is often limited during some periods of the year, obtaining adequate amounts of vitamin D becomes more of a problem. Small quantities of vitamin D3 are also found in eggs, veal, beef, butter, and vegetable oils while plants, fruits, and nuts are extremely poor sources of vitamin D.
Since the 1960's vitamin D3 has been used also for the supplementation of farm animal and poultry food. Cholesterol typically is extracted from the lanolin of sheep wool and after thorough purification and crystallization can be converted via a laborious chemical synthesis into 7-dehydrocholesterol.
The exact details of the chemical conversion of cholesterol to 7-dehydrocholesterol and the method of large-scale ultraviolet light conversion into vitamin D3 and subsequent purification are closely held topics for which there have been many patents issued (3).
However these are rather low levels of vitamin D3 from the perspective of providing the 600 IU per day as recommended by the Food and Nutrition Board of the Institute of Medicine in 2010..
Seasonal changes in plasma 25-hydroxyvitamin D concentrations of young American black and white women.
Identification of vitamin D3 and 7-dehydrocholesterol in cow's milk by gas chromatography-mass spectrometry and their quantitation by high-performance liquid chromatography. Sun Chemical’in dekorasyon cozumleri markalar?n kulland?klar? cam paketlerin rafta goze carpmas?na yard?mc? olacak” dedi. POLYQuik floor coatings can be combined with colored chip, flake and aggregate for decorative application, while sand and other aggregates can be incorporated for industrial applications where slip-resistance is essential. While hot weather and wind can make concrete harden and gain strength faster, it ultimately leads to weaker concrete than one that's been cured with a membrane and gains strength slowly. However, the monomers that are used to form photo-cured materials are mainly derived from petroleum products. In recent years, there has been a growing trend in using vegetable oils as renewable resources, especially in oleochemical products.
The Applewhite49 and Pelletier50 groups reacted the hydroxyl groups of castor oil with acryloyl chloride to prepared acrylated castor oil (ACO). The monomer with the photo-initiator HAC (2-hydroxy-2-methyl-1-phenyl-propan-1-one) showed the highest conversion rate and reached the highest level of double-bond conversion, followed by the mixtures with BP (benzophenone) TX (2,4-diethyl-9H-thioxanthen-9-one). Thus, the experimental sets based on higher polyols, higher functionality acrylate reactive diluents, and a lower proportion of oil gave better scratch hardness.
Then, the obtained stand oil was functionalized in a two-step one-spot process without solvent in order to graft onto it some photo-polymerizable groups. Their newly developed photo-initiating systems are highly efficient under air upon solar irradiation, leading to 60% conversion, and form a completely tack-free and uncolored coating after 1 h. Increasing the thiol functionality does not increase the rigidity of the materials due to structural factors.
By responding to the degree of crosslinking, layers can be developed that are able to absorb up to 500 times their weight in water.
The major breakthrough in understanding the causative factors of rickets was the development in the period 1910 - 1930 of nutrition as an experimental science and the appreciation of the existence of vitamins. These results clearly established that the antirachitic substance vitamin D was chemically a steroid, more specifically a seco-steroid. With the discovery of the metabolism of vitamin D3 to other active seco-steroids, particularly 1?,25(OH)2D3, it was recommended that 1.0 unit of 1?,25(OH)2D3 be set equivalent in molar terms to that of the parent vitamin D3.
In the United States, artificial fortification of foods such as milk (both fresh and evaporated), margarine and butter, cereals, and chocolate mixes help in meeting the RDA recommendations.
Vitamin D2 (which is equivalently potent to vitamin D3 in humans and many mammals, but not birds) is produced commercially by the irradiation of the plant sterol ergosterol with ultraviolet light. The four steroids that do not have a broken 9, 10-carbon bond (provitamin D, lumisterol, pyrocalciferol, and isopyrocalciferol) represent the four diastereomers with either an a- or b-orientation of the methyl group on carbon-10 and the hydrogen on carbon-9. Mitochondrial mixed-function oxidases are composed of three proteins that are integral components of the mitochondrial membrane; they are renal ferredoxin reductase, renal ferredoxin, and cytochrome P-450. The most important determinant of the 1-hydroxylase activity is the vitamin D status of the animal. Also, 1a,25(OH)2D3 generates biological effects involving rapid signal transduction pathways utilizing a putative membrane receptor. There are many scientific publications; a list of recent summary articles are available at the end of this presentation.
There are two general chemical categories of vitamins based on their solubility: water soluble vitamins (the B vitamins and others) and fat soluble vitamins (A, D, E and K). Cholesterol in animals and man is a precursor substance for all steroid hormones and as well vitamin D3. 1a,25(OH)2D3, is considered to be a steroid hormone because the general mechanism by which it produces the biological responses attributed to vitamin D is similar to those of steroid hormones (3;4). A regular access to vitamin D3 throughout life is important to facilitate the normal absorption into the body of dietary calcium which, in turn, is essential for normal bone health and may diminish or prevent the onset in the elderly of the bone disease osteoporosis.
As a result, the incidence of rickets in these countries is higher than in the United States.
In the United States, fortification of foods such as milk (both fresh and evaporated), margarine and butter, cereals, and chocolate mixes help in meeting the adequate intake (RDA) recommendations (11). It should be appreciated that once chemically pure, crystalline 7-dehydrocholesterol has been obtained, it is impossible to use any chemical or biological tests or procedures to determine the original source (sheep lanolin, pig skin, cow skin, etc.) of the cholesterol or 7-dehydrocholesterol.
Accordingly, as discussed above, the business practice of supplementing cows milk with chemically synthesized vitamin D3 was initiated.
It is simply not possible to distinguish the origins of the two vitamin D3 preparations by any biological or chemical procedure, because they are the same molecular structure. The petroleum in the Earth will last for fewer than 100 years, hence, in the past few decades, much attention has been paid to feedstocks for polymers based on renewable resources. The high conversion rate for HAC might be due to the quick generation of radical pairs through the efficient ?-cleavage process of Type I photo-initiators.
Higher cross-linking densities showed better solvent and chemical resistance in the cured films.
The thermal stability of the obtained hybrid materials increased with the increase of POSS content. This UV coating offers possibilities that can be utilised in telecommunication, agriculture, and hygiene and medical applications, amongst others.
They excised a small portion of skin, irradiated it with ultraviolet light, and then fed it to groups of rachitic rats. An experimental demonstration of the existence of a vitamin which promotes calcium deposition. Thus, 1.0 unit of 1?,25(OH)2D3 has been operationally defined to be equivalent to 65 pmoles. Seco-steroids are those in which one of the rings has been broken; in vitamin D, the 9,10 carbon-carbon bond of ring B is broken, and it is indicated by the inclusion of "9,10-seco" in the official nomenclature. The two secosteroid products, vitamin D3, previtamin D3, and tachysterol3 have differing positions of the three conjugated double bonds. In addition, the VDR is known to localize with the plasma membrane of the target cell where it initiates rapid responses (e.g. The precise biological roles of 24,25(OH)2D3 are not yet defined although it is believed to function in bone and cartilage. Under these circumstances vitamin D3 is not a vitamin because it has been produced by the body (with the assistance of sunlight). Because only fluid milk is fortified with vitamin D, other dairy products (cheese, yogurt, etc.) only provide the vitamin that was produced by the animal itself.
At the present time almost all milk sold commercially in the United States has 400 IU of chemically synthesized vitamin D3 added per quart. Further, there is no legal requirement for the manufacturer of the vitamin D3 formulated for human food supplementation to specify the animal sources of the precursor molecules that were employed in the synthesis of the D vitamin. CH3COOH and HCOOH as oxygen carriers, but they found that acetic acid is a more effective oxygen carrier than formic acid.
This UV-curable resin can be used for wood coating, as it contains sufficient cross-link density to withstand the solvent stress. The thermal decomposition temperature of the hybrid materials is between 250 and 300 °C, and the Young's modulus of the cured hybrid film is 230 MPa, which is higher than pure cured acrylated castor oil films. The skin that had been irradiated provided an absolute protection against rickets, whereas the unirradiated skin provided no protection whatsoever; clearly, these animals were able to produce by uv irradiation adequate quantities of "the fat-soluble vitamin", suggesting that it was not an essential dietary trace constituent. In addition to geographical and seasonal factors, ultraviolet light from the sun may also be blocked by air pollution.
Thus, it is important to appreciate that vitamin D3 can be endogenously produced and that as long as the animal (or human) has access on a regular basis to sunlight there is no dietary requirement for this vitamin. In the skin, the principal product is previtamin D3, which then undergoes a 1,7-sigmatropic hydrogen transfer from C-19 to C-9, yielding the final vitamin D3: Vitamin D3 can be drawn as either a 6-s-trans representation or as 6-s-cis representation depending upon the state of rotation about the 6,7-single bond. Any vendor of milk for human consumption containing added vitamin D3 is required by the US Food and Drug Administration (FDA) to include a notice on the milk carton label. Vegetable oils have already been utilized extensively in coatings, inks, lubricants, resins, agrochemicals and plasticizers.
Moreover, the polymer chains are flexible enough against scratches and exhibit good adhesion to wood substrates. Compared to a naturally oxidized linseed-oil-based materials, the thermal stability and hydrophobicity remained unchanged.
Interestingly, the photo-reaction can therefore be performed under mild conditions, requiring neither solvent nor photo-initiator. These characteristics give the obtained hybrid material potential applications in coating, and these studies provided a novel alternative approach to preparing hybrid materials from renewable sources.
In parallel studies, Steenbock and Black at the Biochemistry Department of the University of Wisconsin found that rat food which was irradiated with ultra violet light also acquired the property of being antirachitic. The tendency to wear clothes, to live in cities where tall buildings block adequate sunlight from reaching the ground, to live indoors, to use synthetic sunscreens that block ultraviolet rays, and to live in geographical regions of the world that do not receive adequate sunlight, all contribute to the inability of the skin to biosynthesize sufficient amounts of vitamin D3.
The resulting vitamin D3, which is formed in the skin, is removed by binding to the plasma transport protein, the vitamin D-binding protein (DBP), present in the capillary bed of the dermis. A number of excellent articles have appeared describing the current understanding of how the VDR regulates both gene transcription and rapid responses.
Under these conditions, vitamin D becomes a true vitamin which dictates that it must be supplied in the diet on a regular basis. Because of the presences of CC bonds in vegetable oils, they can be easily functionalized with reactive groups such as epoxy, hydroxyl, carboxyl and acrylate.
However, because of the rapid rise of the science of nutrition -- and the discovery of the families of water-soluble and fat-soluble vitamins -- it rapidly became firmly established that the antirachitic factor was to be classified as a vitamin. Under these conditions vitamin D becomes a true vitamin in that it must be supplied in the diet on a regular basis. However it is not required by law to indicate either the manufacturer of the added vitamin D3 or the sources of the cholesterol and 7-dehydrocholesterol used for its production. These functionalized vegetable oils have been used to prepare polyurethane, elastomers, plastics and pressure-sensitive adhesives. This one-step route to produce fatty polyols represents a significant advance compared to the traditional epoxidation approach (that occurs in two steps) and further evidence of the synthetic usefulness of thiol addition in materials chemistry. In contrast to feedstocks extracted from petroleum, vegetable oil feedstocks are non-toxic and friendly to the environment. Indeed, this synthetic method can readily incorporate different reactive functionalities onto vegetable oils and their derivatives, thus leading to functional precursors suitable for polymer synthesis.
Therefore, in view of the attractive advantages of both photo-curing technologies and vegetable oils, it is worth the energy and money required to research and develop photo-cured materials based on vegetable oils.
Through a similarly efficient coupling procedure, Meier99 described the syntheses of materials derived from plant oils. By coupling both transesterification and thiol-ene addition, the Caillol group100 synthesized a pseudo-telechelic diol from vegetable oil.



Glue glass rubber seals
Bohle uv adhesive glue
Supercove coving adhesive
Philips t8 uv lamp 25 watt xenon

Comments Uv curing chemical reaction

  1. hgk
    Possible through seemingly difficult surfaces that you've got a glue patch on your forever, but.
  2. Narmina
    For vertebrate zoology collections safe to leave petroleum jelly to soak into the glue patch dangerous.