Analytical Odor Control in the Recycling Sector: FlavorsSpec.Recycled materials , which are raw materials from the selection of waste, in their various states of life (loose, bales, ground, granules), o the final product, created through recycling processes, can bring with them gradients and types of odors that can be more or less unpleasant to operators or end customers. The sensation of acceptance or not of smell is entirely subjective and depends on an infinite series of sensory evaluations: what for me could be an acceptable smell, for the customer could be an unbearable home. The human nose is sensitive, but different between person and person in intercepting odors and, above all, it is not able to accurately catalog an equal level of odorous compounds, nor the repetition of the intensity of the odors it intercepts. What a company produces, in terms of smell on a product , whether it is raw material or a finished element, must be cataloged in a completely analytical way, without approximation, to determine standards that can accepted by both the producer and the customer, so that all subsequent productions can fall within the established ranges. Defining and being able to replicate a range of odors accepted by the parties is not only an increase in the qualitative service of the product itself and of the company, but also a guarantee towards the end customer who can reasonably know that the odor intensity can be cataloged and managed exactly. Let's see some examples where an "electronic nose" can make the difference : • Producers of PET trays, receiving the recycled granule or ground, can analytically evaluate the odor intensity of the raw material and give the producer himself standards not to be exceeded to avoid problems on the trays in the distribution chain. • Manufacturers of beverages in PET bottles can establish with certainty not only the maximum odor levels accepted on the raw material, but they can establish whether the product contained in the bottles can undergo transfers by the plastic bottle of odorous substances that can affect the quality of their product. • Producers of raw materials can establish with their customers the maximum odor ranges acceptable to both, through an analytical analysis of the material first sold in order to ensure a reliable product quality. • The manufacturers of bottles for detergents , for care, for perfumed liquids need to purchase recycled raw material in HDPE that has an odor content coming from the surfactants such that they do not interact negatively with the final packaging on the shelves of the shops or can alter the fragrance of the liquids or powders contained. • Furniture or packaging manufacturers for industrial logistics who use PP, HDPE and LDPE from post consumption, they must be able to establish with certainty the incidence of the odors of the raw materials they buy, in order to establish limits that cannot negatively affect the final product they distribute. • We could continue to cite other examples in which the lack of a certain classification of odors can often lead to the dispute of the materials, with considerable costs and degeneration of customer-supplier relationships. Through the use of an odorous substance analyzer , a laboratory machine that uses samples of raw materials or pieces of final products , therefore in the form of granules, ground, liquids, etc ..., which are heated, creating volatile substances inside the test tube, which are then chemically analyzed and compared, through an analysis program, this creates a precise picture of the types and intensities. The machine allows you to compare also standard samples and therefore accepted by the parties, with the various production samples in order to intercept the deviations and immediately evaluate production corrections. The results of the analyzes return a precise photograph, not only of the odor intensity, but also of the types of chemical compounds present in the samples that produce the mix of odors, so as to be able to intervene in a precise and timely manner. The tool that analytically analyzes the smells or fragrances of the volatile substances contained in the products is also used in the food sector to unmask food sophistications such as, for example, those of olive oil, to verify the compositions of coffee, to evaluate the freshness of food or the transfer of substances contained in the packaging to food. If you want more information on the equipment for the analytical evaluation of odors write to us.
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How and why it is necessary to reduce the moisture of recycled polymers before their use. As described in the article the" Absorption of 'humidity in polymers ” the presence of humidity on the external surface and inside the polymeric masses creates different types of problems for the characteristics of the raw material to be used. Both hygroscopic and non-hygroscopic recycled plastic polymers are subject to the damaging effect of moisture, which can be absorbed in the phases processing, transport or storage, through the search for a balance with the environment in which they are found. As we have seen, in non-hygroscopic recycled polymers, moisture is retained on the surface, while in hygroscopic ones it will also be found inside the plastic granule. Humidity, whether on the surface or inside the granule, negatively affects the aesthetic and mechanical aspect of the final product and, therefore, to produce a plastic raw material that does not encounter these problems, it must be dehumidified before using it. The percentage of residual moisture tolerated by the recycled raw material is usually indicated by the producers through the quality control of the outgoing goods and can vary according to the type of polymer taken into consideration and the type of product to be made. It must be borne in mind that recycled plastics, after the packaging phase, spend more or less long times in transport and storage operations, times in which it is possible that the polymers take on new moisture. For this reason it is always recommended, before using the granule, to carry out the dehumidification operation which, according to the polymer , may require variable times, reaching a final residual humidity expressed as follows for a polymer sampling: • ABS Air temperature: 80 ° Treatment time: 2-3 hours Residual moisture: 200 ppm • PE Air temperature: 90 ° Treatment time: 1 hour Residual moisture: 100 ppm • PP Air temperature: 90 ° Treatment time: 1 hour Residual moisture: 200 ppm • PVC Air temperature: 70 ° Treatment time: 1 hour Residual moisture: 200 ppm The most common way to dehumidify recycled polymers is to bring the plastic material together with a current of hot air , as this has the ability to retain humidity and the higher the temperature, the greater the volume of humidity removed. The air has the ability to retain water until it is saturated and this quantity varies according to the temperature increase. For example 1 Kg. Of air is saturated with: • 20 ° - 14.7 grams of water • 35 ° - 36.6 grams of water • 50 ° - 82.6 grams of water In polymer dehumidification cycles it is possible to use the air coming from the environment, defined as simple drying, only in situations of favorable temperature and humidity. While previously dried air, called dehumidified, can be used to achieve an important drying action even in unfavorable conditions. We take into consideration that a dry granule, when placed in contact with the air, begins to absorb moisture , whose percentage will vary as the climatic conditions in which it is found vary, therefore the type of dehumidification intervention will vary according to these parameters. In a drying process the hot air will hit the granule, which will be placed in a hopper, which will release moisture from its surface and its interior. which will migrate to the created airflow. The main variables, therefore, during a drying process are: • Type of polymer • Starting moisture of the granule • Process air dew point • Required residual moisture • Drying time • Process air temperature • Size of the grain The whole drying process rotates around the humidity residual accepted , depending on the type of product to be produced and the production technique and, the lower the drying process, the higher the temperature used, without prejudice to the technical limits of each polymer on the degree of softening and emanation of harmful substances. The air requirement for the dehumidification processes will be expressed in cubic meters of air for each Kg. of polymer to be dried, taking into account the quantity of granules handled in the hopper, the air temperature and the current consumption. The size and shape of the granule also have an influence in the dehumidification process, as, as its size and surface area per unit of measurement increase ( cube, cylinder or sphere) increases the drying time. Automatic translation. We apologize for any inaccuracies. Original article in Italian.
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Moisture in polymers: hygroscopic and non-hygroscopic materials.All materials polymeric materials during the synthesis, transport and storage phase have a tendency to retain moisture,reaching a equilibrium value with the environment, which depends on the type of polymer, humidity and air temperature, the size of the grain and many other factors that will be studied in detail in the next chapter. Depending on the ability to absorb water molecules in the surrounding environment, plastics can be divided into: igroscopic and non-igroscopic. In igroscopic polymers, water is absorbed inside the plastic grain and chemically binds with the material itself. They belong to this group engineering polymers such as polyammide (PA), polycarbonate (PC), polymethylatecrilate (PMMA), polyethyryreftalate (PET), acrylonitrile-butadiene-stirene (ABS). In non-igroscopic polymers, on the other hand, water does not penetrate the material but only settles on the surface. Polyethylene (PE), polypropylene (PP), polystyrene (PS) are polymers of this type. The process of removing surface moisture in non-igroscopic materials is quick and easy and requires the use of hot air dryers. In the case of igroscopic polymers, on the other hand, the removal of residual moisture is more difficult and requires the use of dehumidifiers in which the hot air, infused to remove the water contained in polymer granules, is preemptively dehumidified. Many technical polymers (also called “technopolymers” or “engineering polymers”) are igroscopic and are characterized by a certain percentage of moisture that makes them saturated and a precise rate of absorption. When a higroscopic polymer is exposed to the atmosphere, water molecules spread within the polymer structure by binding to molecular chains and causing the reduction of intermolecular bonds and increasing the mobility of molecules, acting as a plasticizer. In general, the igroscopicity of a polymer is linked to the polarity of the chemical structure of the polymer’s macromolecules. An important feature of water is the polarity of its molecule, with a molecular dipole moment of 1,847 D. The water molecule forms an angle of 104.5o with the oxygen atom at the top and the two hydrogen atoms at either end. Since oxygen has a greater electroniveness,the vertex of the molecule hosts a partial negative electrical charge, while the extremities carry a partial positive electrical charge. A molecule that presents this imbalance of electrical charges is said to be an electric dipole. In the molecular structure of many higroscopic polymers is present the carbonyl group, which is a functional group consisting of a carbon atom and one oxygen atom bound by a double bond. The peculiarity of this group is that oxygen is very electronegative and gives a polarity to the bond. Since oxygen has a greater electroniveness, it hosts a partial negative electrical charge, while carbon remains a partial positive electrical charge. Polymers containing many carbonyl groups therefore have a negative charge on oxygen that attracts the positive charge present on the hydrogen atom of the water molecule. The attraction between the positive and the negative charge generates a weak bond called a hydrogen bridge. The carbonyl group is present in many igroscopic polymers such as polycarbonate (PC), polyeilentereftalate (PET) and polybutilentereftalate (PBT). Hydrogen bridge bonds are weak compared to the strong bonds in the polymer chain, but they are strong enough to cause water molecules to absorb up to a equilibrium value that is characteristic for each different type of polymer. In polyamide, nitrogen-bound hydrogen has a weak positive charge, as the nitrogen atom is much more electronegative than the hydrogen atom, and once attracted by the negative oxygen charge of the water molecule forms a hydrogen bridge bond. In addition, there is also a carbonyl group in polyammides that forms weak bonds with hydrogen in water molecules. The higroscopicity of polymers, therefore, is linked to the structure of macromolecules and the formation of hydrogen bridge bonds that cause moisture to rise. In fact polymers that contain the carbonyl group and polymers such as polyammides are igroscopic and absorb moisture through the formation of hydrogen bonds. Non-polar polymers, on the other hand, such as polyolefins (polypropylene and polyethylene) and polystyrene do not absorb moisture through hydrogen bonds.
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What challenges automakers face to overcome today’s crisis. Is a happy era over? The auto industry has been one of the most admired and envied entrepreneurial activities since the post-war period, arousing passion, dynamism, freedom and a sense of affirmation in their customers. Among the first truly globalized and globalizing companies. Today, however, things are changing. Having a car in the 60s was generally a fairly high goal for ordinary people, which gave many a sense of well-being of their family and a social revenge after the dark years of the war. In the following years the machine took on different symbols : social and class struggle, passion for a brand like a football team, a means of work in transformation, a tool for female emancipation and a means for youth independence. For each period of our life, the automotive industry, more than others, has been able to interpret the social needs , expectations and dreams of its customers, becoming a global company, with a growth in sales at a rate such as to financially support the continuous evolutions of the sector. In recent times many clouds have thickened over this industry , due to strong changes that could undermine the stability of the automotive giants. Let’s see some: The increasingly stringent anti-pollution regulations that led automotive causes to begin the conversion of thermal engines to electric ones, making huge investments in research, structures and acquisitions of companies included in the electrification chain. The digitalization of driving systems has triggered fierce competition within the auto system, which has required huge financial resources. In addition, new indirect competitors have appeared on the market, which are developing assisted driving systems, whose companies see the car only as a means of conveying their products. Car sharing is significantly reducing customer purchase requests, especially in large cities, where car sharing is a system that allows you to optimize costs and time of use of the vehicle. The distortion of the concept of car ownership, as a personal and social value, especially among young people, who do not see ownership as an important element in which to invest money. The recent Coronavirus epidemic crisis that imposed a globalized stop on the automotive industries and a consequent reduction in international demand. The confusion from a regulatory point of view on power supplies (petrol or diesel), in relation to anti-pollution measures and possible tax exemptions, has created an atmosphere of uncertainty among users. In the face of all this, the automotive industries are rethinking their future scenario by questioning some previous forecasts. Strict compliance with the environmental regulations imposed by many states, not least Europe, had imposed a rapid transition to the electric car , which today is seriously questioned due to a decidedly declining market, which does not allow to generate revenue in line with planned investments. Therefore, postponing the completion of projects related to electric mobility , which had placed car manufacturers in front of onerous but ambitious choices, is putting a strain on not only the primary sector, but also the related sector, consisting of the supplies of raw materials, the spare parts, plant engineering, logistics, distribution, financial structures, engineering. Furthermore, there could be a contraction in the workforce of the evaluable sector, according to ACEA , which represents the association of European manufacturers , in 14 million units in Europe. A social problem before an industrial one.
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Metal boxes for food preservation have a long history but, if in the past, they had deficiencies from the hygienic and toxicological point, especially in because of the welds that were made in Sn-Pb alloy, currently the quality of the manufactured products are much better. Today the protection of food is mainly entrusted to the polymeric layer of inner coating , called coating , which stands between the metal wall and the contained food. The primary function of this barrier is to protect food products from light, oxygen, enzymes, humidity, pollutants and microorganisms that would result in the modification of the structure of the food and its quality. The aim is also to increase the useful life of the food or the drink which in normal, that is, not canned, it would deteriorate more quickly, as the biochemical and enzymatic reactions and the activity of microorganisms would normally run their course. Therefore, to increase the life of the food, the metal packages are normally coated with synthetic resin film applied to the metal sheet again flat, film with a thickness of a few microns. The choice of the type of resin depends on its mechanical, chemical or thermal characteristics based on the content they must host. Below we can list the main ones: • Rosin consists mainly of abietic acid, which is normally added with ZnO to control the chemical reactions that are formed through the sulfur amino acids of proteins. • Vinyl resins are from the family of thermoplastic resins, normally PVC, which have excellent resistance to acids, but have the defect to absorb food pigments. • Phenolic resins are composed through the polymerization of formaldehyde and phenol which have excellent resistance to heat treatments, PH and to fats. Through the formaldehyde content we can identify two families of phenolic resins: Novolacche (thermoplastic) and Resoli (thermosetting). • Epoxy Resins are thermosetting resins consisting of bisphenol A and epichlorohydrin which are the most common coating in canned foods, especially in fish-based foods in oil. • Polyester resins are thermosetting resins obtained from different monomers such as phthalic anhydride, maleic anhydride or fumaric acid, integrated with vegetable oils and pigments. They have the characteristic of flexibility giving this characteristic to the metal wall layer. • Epoxy-Phenolic Resins are the result of the polymerization of epoxy resins with phenolic ones through catalysts. They are used as a transparent coating for many metal cans that contain oil, vegetable or pet food preserves. As regards the toxicological characteristics there are specific legal regulations that place limits on the possible migration of packaging substances into food, in which both specific migration and global migration are considered. However, the scientific community has given new impetus to studies and research on the toxicological aspects relating to plastics used in the food industry, with particular attention no longer to the single element that constitutes the packaging, but takes into consideration the cocktail effect that is given by all the elements that come into contact with food translated over time and with different thermal characteristics. Undoubtedly the food or drink contained in the packaging at the time of packaging has certain characteristics, but over time and in different climatic conditions , the quality of the food that arrives on the table could be different. Therefore it would be advisable to verify it through a chemical analysis, on a sample, with an instrument composed of a gas chromatograph and a spectrometer ion mobility that, in a simple and rapid way, will give the photograph, analytical, of the quality of food or drinks. Automatic translation. We apologize for any inaccuracies. Original article in Italian.
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