Fabrication building rigid artificial leather, type of cardboard
The origin of tannins, their historical evolution, their different types, and their applications are described. Old and established applications are described, as well as the future applications which are being developed at present and that promise to have an industrial impact in the future. The chemistry of some of these applications is discussed where it is essential to understand the tannins and their derivates role. The essential points of each application, their drawbacks, and their chance of industrial application are briefly discussed.VIDEO ON THE TOPIC: Faux (Synthetic) Leather Manufacturing Process
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Plastic Material Classifications
The origin of tannins, their historical evolution, their different types, and their applications are described. Old and established applications are described, as well as the future applications which are being developed at present and that promise to have an industrial impact in the future.
The chemistry of some of these applications is discussed where it is essential to understand the tannins and their derivates role. The essential points of each application, their drawbacks, and their chance of industrial application are briefly discussed. The article presents historical applications of tannins, such as leather, or traditional medicine, and more recent applications. Leather tanning has been used for centuries, even millennia, by immersing skins in water where special barks or woods containing tannin have been added.
Up to a full year was necessary for leather to be produced in such a manner. However, the current tannin extraction industry is relatively newer. In , various researchers identified the presence of an acid in these compounds.
This acid was then isolated by Scheele and turned out to be gallic acid. Based on the experiments of Deyeux and Bartholdi, continued by Proust in the late 18th and early 19th centuries, tannins have been officially recognized as a discrete group of different molecules based on gallic acid content.
After 10 years, fashion changed and thus after many bankruptcies and groupings of factories, tannin manufacturers were able to convince the leather industry to use tannin in place of oak chips with considerable savings in tanning time from 12 months with the old system based on wood chips rich in tannin to 28 days using tannin extract [ 1 ]. The benefits of tannin extracts in the manufacture of leather, and even the time savings still allowed by their use, were such that the industry expanded rapidly and thrived.
Tannin being in short supply in Europe, factories were opened in distant countries to satisfy the growing demand and promoting the use of alternative tannin types. Early in the 20th century, South American and southern and central African tannins began to be industrially extracted to supply major markets in Europe and North America. Among these, the main ones were quebracho wood and mimosa bark tannins. Leather processing was thus the second major boom period for the tannin industry.
After World War II the substitution of leather with synthetic materials for shoes again caused a number of tannin extraction plants to close [ 2 ]. The third period of use of tannin therefore began, first with their development as bio-based adhesives and later with an increasing number of applications in new bio-based materials, this latter period being still in full development.
Their general appearance varies, ranging from white amorphous powders to off-white amorphous powders, to glossy, almost colorless pasty substances, to reddish-brown powders when produced by spray drying. They have an astringent taste. Tannins are natural products found in most higher plants.
They are produced in almost all parts of the plant, namely seeds, roots, bark, wood, and leaves, because of their fundamental role in the defense of the plant against insects, food infections, fungi, or bacteria.
The defense mechanism is based on the ability of tannins to complex proteins irreversibly. They are also considered as one of the effective components contributing to the fact that the risk of suffering from cardiovascular diseases and some forms of cancer can be reduced by choosing diets rich in fruits and vegetables.
In addition to their documented effects on human health, tannins are also important for the welfare of ruminants; high protein feeds such as alfalfa trigger the production in the rumen of methane trapped as proteinaceous foam, resulting in a potentially mortal fermentation that can be reduced by adding tannin in the diet.
Two wide classes of tannins exist: hydrolysable tannins such as gallo-tannins and ellagi-tannins, and condensed polyflavonoid tannins, these latter being stable and rarely subject to hydrolysis [ 2 ]. The hydrolysable tannins, usually present in small amounts in plants, are simple derivatives of gallic acid, and they are classified according to the products obtained after hydrolysis—gallo-tannins gallic acid compounds and glucose and ellagi-tannins composed of biaryl units and glucose.
Most gallo-tannins isolated from plants contain a polyol residue derived from D-glucose, although a large variety of polyol types can be found. Two other categories, gallo-tannins of tara composed of gallic and quinic acid and glucose and caffe-tannins quinic acid esterified with caffeic acids plus glucose compounds , also occur [ 3 , 4 ] Figure 1. Example of the structures of tara tannin [ 3 , 4 ] and caffe-tannins quinic acid esterified with caffeic acids plus glucose compounds. Tannic acid is one of the most important substances in relation to hydrolysable tannins.
Tannic acid exists de facto in the form of a mixture of very similar substances, for example penta- digalloyl -glucose and tetra- digalloyl -glucose or tri- digalloyl -di- galloyl -glucose, etc.
Different from gallo-tannins, ellagi-tannins contain additional binding motifs that arise from additional oxidative coupling reactions between the galloyl fragments [ 6 ]. The biosynthesis of ellagi-tannin is therefore an oxidative enzymatic progression of gallo-tannins. The first step is an oxidation of 1,2,3,4,6-pentagalloylglucose to form the monomeric ellagi-tannin.
The second step consists essentially of dimerization after a second enzyme-mediated specific oxidation of hexahydroxydiphenoyl group of the ellagi-tannin with the galloyl group of another tannin to form a valoneyl group-containing dimer and these reactions continue to form higher oligomers.
An example of ellagi-tannin is the tannin of chestnut wood Figure 2. Schematic representation of the repeating unit of the ellagi-tannin of chestnut wood. Condensed tannin extracts consist of flavonoid oligomers of different average degrees of polymerisation.
Small proportions of flavanols, flavan-3,4-diols, and other flavonoid analogs are also present [ 7 , 8 ]. Carbohydrates, such as broken down residues of hemicelluloses, and hexoses, pentoses, and disaccharides together with some imino acids and amino acids [ 2 , 9 ] constitute the non-phenolic part of tannin extracts. These latter, as well as the monoflavonoids, are equally present in too low a proportion to influence the extract properties. On the contrary, oligomers derived from hydrolysed hemicelluloses are often present in sufficient quantities.
Equally, carbohydrate chains of various lengths [ 4 , 5 ] are also sometime linked to the flavonoid unit in the tannin. The basic structure of these tannins is based on the flavonoid unit Figure 3.
These flavonoid units are generally linked C4 to C6, or C4 to C8 to forms a variety of short chains of different lengths according to the type of tannin. The industrial uses briefly described below are in order of present or probable future importance to give an idea of what is developed and used already, and which applications are likely to gather importance in the future.
The manufacture of leather is still the largest use of tannins of vegetable origin. Leather has traditionally been made in ground pits in which alternating layers of animal skins and wood chips containing tannins, such as oak chips, have been placed and soaked for considerable periods of time.
The tannins exfiltrated the wood chips and slowly impregnated increasingly more of each skin. Such a manufacturing system was practiced for many centuries and produced good quality leather but it took several months, often a whole year, for the leather to be ready. The first change came when the tannin extraction industry, which had grown considerably in the s to supply black iron tannate dyes to color silk, was in a desperate position because of the change in fashion. Some tannin extraction plants were able to demonstrate that by directly adding tannin extract to traditional tanning pits, the same quality of leather could be produced in just 28 days 28 pits, one per day.
Leather tanned in this way began to prevail and this use led to a boom which lasted mainly until the end of the Second World War.
In particular, the war years were good simply because armies were walking in leather boots. At the end of the Second World War, three events contributed significantly to the steady decline in vegetable tanned leather. First, the introduction of synthetic materials, derived from petrol, for shoe soles begun to compete strongly with leather for one of its most traditional applications.
Secondly, the demobilization of armies, which sharply reduced the need for leather shoes, and the third, the strong penetration of the market by chromium salt tanning for the manufacture of soft leathers, in particular the upper part of shoes. With all these changes, while vegetable leather has now begun to gain a reputation as a luxury product, there are still some important niches for which it is used such as equestrian equipment, heavy bags and luggage, and other heavy applications as well as the real high price luxury markets.
Although the traditional 28 pits tanning method still exists for a number of special leathers as well as in the case of artisanal leather as in Morocco for example , the tanning processes has also evolved for vegetable tanning where rotary drums, a technique borrowed from chrome tanning, allows vegetable tanning to be finalized in about 24 h.
Today, research on vegetable tanned leather has been able to produce much more supple leather through the inclusion of oils and other techniques, so that some rebirth of the use of plant tannins for other application areas appears to take place. There are a number of detailed reviews on the use of tannins for wood adhesives.
The reader is referred to these detailed studies [ 2 , 10 ]. However, here existing technologies and industrial use of wood tannin adhesives are presented. As extensive studies already exist, and this application of tannin is now the second most important after leather manufacturing, only a few of the main achievements of tannin-based adhesives for wood products will be highlighted.
All industrialized technologies today are based on paraformaldehyde or hexamethylene tetramine hexamine [ 36 ]. The latter is much more user and environmentally friendly. As regards wood adhesives, a number of experimental improvements have been studied, dictated by the new environment in which wood adhesives must operate. First of all, the relative scarcity of tannins produced in the world, compared to the tonnage of synthetic adhesives used in the panel industry, has led to a great deal of research on the extension of the tannin resource in order to have larger tonnage.
As the potential material for tannin extraction shows that millions of tons of this material can be extracted each year worldwide, some companies have started to build additional extraction plants.
This movement is still relatively small, but it is ongoing. The second approach, to extend the tannin with another abundant and natural material, has led to the preparation of adhesives based on in situ copolymers of tannins and lignin [ 37 ] or copolymers of tannin and protein or soy flour [ 38 ], and the use of tannin—furfuryl alcohol adhesive formulations, furfuryl alcohol being also a bio-based material [ 39 ].
The second new constraint is the demand of most companies to eliminate formaldehyde emissions from tannin adhesive. Tannins are known bactericides because they react with proteins irreversibly, thus complexing within bacterial membranes, neutralizing their activity. As a consequence, tannin-based pharmaceuticals to cure intestine infections have long-time been marketed. They have effective anticaries properties.
Several experimental studies on the pharmaceutical use of tannins have been published with antitumor and anti-oncogenic activities particularly well documented [ 47 , 48 , 49 , 50 , 51 , 52 ]. Their antiviral effectiveness is also well documented by in vitro screening for a variety of 12 different hydrolysable and condensed tannins [ 51 ].
The lower MIC values yielded the best antiviral behavior. The effectiveness of different tannins due to their polyphenolic nature can be very high against a number of different viruses.
This is due to their irreversible reaction and combination with the viruses capsid proteins. It is the same reaction used in leather tannins and in their association with carbohydrates.
Thus, a number of commercially available tannins have been tested, namely mimosa bark tannin extract and its derivatives, chestnut tannin extract, tara tannin, quebracho wood tannin extract both sulphited and natural, pecan nut tannin extract, pine bark tannin extract, sumach tannin extract, and spruce tannin extract [ 51 ]. The inhibitory effects of these tannins have also been tested on proliferation of murine leukemia cells, murine mammary carcinoma cells, and human T-cells [ 51 ].
Acutissimin A is a bound flavonoid with an ellagi-tannin. Acutissimin A has been found to present an effectiveness times higher to stop tumors growth than the drug Etoposide.
While many studies have been conducted on a variety of tannins derived from a wide variety of plants as an anticancer treatment, some studies on the possibility of using tannin for other medical applications have also been highlighted. Condensed tannins are traditionally used for the treatment of intestinal problems [ 55 , 56 ]. This is due to their complexation ability with other molecules and their antioxidant behavior.
The extract of Stryphnodendron rotundifolium and of other tannins has proven their effectiveness against ulcers by functioning as a protective coating of the gastrointestinal tract [ 57 , 58 , 59 ]. Other possible mechanisms of action of phenolic plant extracts as herbal medicines against ulcers and gastritis have also been described [ 57 , 58 , 59 , 60 ].
Wine, beer, and fruit juices naturally contain tannins [ 61 ]. It is actually their presence that accounts for their characteristic taste.
Too low an amount of tannin and the beverage will be insipid and with no taste. Initially, addition of tannin or tannin-rich wood chips directly to wine to enhance its taste and give the impression of a wine of greater age was strictly forbidden in most European countries.
With the determined and successful push for wine markets by southern hemisphere producers where limitations on adding oak particles to the wine to accelerate its aging was not forbidden, producers of more established countries tried to defend their market in a different way. Some producers the wines of which were particularly low in tannin content started to add tannin directly to some of their wines.
This was kept fairly confidential, to not incur potential problems.
Classification of goods and services — Name of the classes. Parts of an article or apparatus are, in general, classified with the actual article or apparatus, except where such parts constitute articles included in other classes. Class 1. Chemical used in industry, science, photography, agriculture, horticulture and forestry; unprocessed artificial resins, unprocessed plastics; manures; fire extinguishing compositions; tempering and soldering preparations; chemical substances for preserving foodstuffs; tanning substances; adhesive used in industry. Class 2.
We provide footwear adhesive products for any part of the shoe which requires a hot melt adhesive glue or film to stick a component into place or to bond various layers together. Variations include thin laminating films, dry granules or touch sensitive adhesives. It is necessary to identify the different processes in a shoemaking where adhesives are involved and the different adhesive joints produced, as well as their technical requirements. So we offer chemical products for various parts of footwear. You can easily find the best one for your products on this page.
Introduction to Leatherworking
PVC is no stranger to the clothing industry. Employed for its waterproof qualities and aesthetic versatility, it is commonly used in footwear, coats, sporting gear and accessories. When manufacturers are in need of hard wearing leatherette that is supple and doesn't lose its shape easily, they rely on the qualities of PVC. Plasticized PVC suspension type resins can also be used to produce soft semi-rigid soles, thanks to its ability to withstand all weather conditions, resistance to abrasion and antistatic properties. The coating technique is used to manufacture boots from PVC pastes. Compact or cellular injection of suspension type resins are used to produce soles. Increasingly PVC is used to manufacture shoes, contributing to the creation of hard-wearing yet supple leatherette that doesn't easily lose its shape. PVC is also ideal for manufacturing stiffeners for dress shoes.
Vegan Leather Isn’t As Ethical As You Think
Here are all the tools you'll need for the specific kind of leatherwork we will be doing in this class. I'll show you how to use a few more optional tools along the way as well, but there are a few basics that you will definitely need to get started. You can buy your tools individually, or you can also choose to buy a leatherworking tool kit. I'll talk more about each tool and material specifically in a minute.
Almost free, easy to find, easy to manipulate, cardboard prototyping is also super fun. Besides looking around your house, there are a few ways to get cardboard for free. Ask you local grocery stores and supermarkets Walmart, Costco if they have boxes to spare. For large size free cardboard: try kitchen stores, bike stores and dollar stores.
What do you need to sew bags? Just a sewing machine and pretty fabric? If you make bags as a hobby or it is your whole career — By the time you have made the first few bags, you would have come to know that sewing bags is addictive. And that the right material and hardware play very important roles with almost equal importance in making your bag beautiful and functionally appropriate. Here are the most important bag materials as a list.
DOWSIL™ 790 Silicone Building Sealant
Leather is an amazing product that has been used by humans since really, the beginning of man. It's in clothes, shoes, bags, belts, holsters and really, pretty much anything you can think of can be made from leather. Working with leather isn't as hard as some people fear it will be, but the craft of it has been around for such a long time, and people have been improvising tools to work with leather, literally as long as people have been using leather to make things. Going into a retail leather supply store, you'll very likely wind up with sticker shock when you see how much some of the tools and leather itself costs. My goal with this Instructable is to help you decide what tools you really must have, what you can improvise on your own, and some alternatives to a leather specific retail store for some of your items.
Leather Tools and Supplies
We also have experts on hand at all times to show you how to use every tools and to keep you safe while you do. Take a look at the equipment available to you. Precisely cut vinyl decals, conductive copper film, adhesive backed epoxy film, or laminate film.
In the production of synthetic leather, the raw materials acquired from the earth are heavily processed to make polyvinyl chloride or polyurethane and excess chemicals during processing are recycled. Product durability seems to be a good solution for waste management by inhibiting the speed of the product life cycle with better raw materials Blackburn, However, lowering the product consumption is the best solution.
Jump to navigation. Before starting the chapter on the uses and subsequent recycling of plastic, let us establish a general classification of these thermosetting resins or thermo-plastics the two big groups into which we include elastomers by detailing their properties, their make-up, their aspect, and their final uses, while explaining which ones are recyclable. Remember that thermoplastic is a material whose structure and viscosity can be modified both ways through heating or cooling. Obtained through the polymerisation of ethylene, polyethylene is a waxy solid, colourless and odourless.
When it comes to leather, a vegan faces two choices: wear synthetic or wear none at all. The answer is complicated. Items that qualify as vegan or faux leather can be produced from materials as varied as cork, barkcloth, glazed cotton, waxed cotton, paper, polyvinyl chloride PVC , and polyurethane. For years PVC was the primary go-to, most famously used in Naugahyde. As a rigid plastic, PVC requires that plasticizers such as phthalates be added in order to make it flexible. Polyurethane, however, presents its own set of economic and environmental challenges.
General building contractors who combine a special trade with the contracting are included in this major group. Specialized activities that are covered here include grading for highways and airport runways; guardrail construction; installation of highway signs; trenching; underwater rock removal; and asphalt and concrete construction of roads, highways, streets and public sidewalks. Establishments primarily engaged in specialized activities that may be performed on buildings or on other heavy construction projects are classified in Major Group These include contractors primarily engaged in painting including bridge painting and traffic lane painting , electrical work including work on bridges, power lines, and power plants , and carpentry work.