jrups
Abstract : Thermal Stability of Polyurethanes from Soybean Oil as Natural Source and its Chemical Modifications
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Abstract: In this contribution, a summary of recent publications about the thermal stability of polyurethanes from soybean oil as natural source for polyols was made. From the review, it can be concluded that polyurethanes from natural oil-derived polyols decomposed at a temperature up to 30°C higher than petrochemically-based polyurethanes. Chemical modification of soybean oil for polyol synthesis is mainly based on epoxidation. However, we highlighted the possibility of functionalizing soybean oil by maleinization, a route that was very scarcely studied. Maleinization allows the introduction of labile reactive hydrogen to react with isocyanates for polyurethane synthesis with a broad range of properties. Keywords: Polyurethanes, modified soybean oil, natural polyol, thermalproperties, maleinization. |
Abstract : Mono- and Bis- Maleimide Resins in Preimpregnated Fibres
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Abstract: Fibres are preimpregnated by solutions of mono- and bis-maleimides with comonomers. Imides alone polymerize to resins with too low energies of fracture. In the presence of Methylene dianiline or Aniline Diphenylmethylenebismaleimide reacts via Michael addition to equimolar addition products. When fibres are preimpregnated with these addition compounds alone or in combination with flame retardants, B-prepregs are obtained, which after curing show high glass temperatures and sufficient energies of fracture. 2.5 moles of Diphenylmethylene bismaleimide and 1mol Methylene dianiline or 1mole Aniline react to resins with glass temperatures of 350 and 380°C and energies of fracture of 75 and 100J/m2. The resins contain no carcinogen or blood harming free amines. A one pot reaction starting from Methylene dianiline and Maleic anhydride is possible and more economic. As polymerized bismaleimides possess their imide bonds in the side chain, they are strictly spoken no polyimides with imide bonds in the main chain. Diphenylmethylenebismaleimide and styrene as copolymer react to an insoluble crosslinked polymer. Fibres are preimpregnated with equimolar mixtures of 2- Bromophenylmaleimide and styrene. After curing laminates with 285°C glass temperature and sufficient energies of fracture are obtained. The heat resistant resins are charring polymers and display higher Limiting Oxygen Indices, when the heats of combustion are increased. Differential Scanning Calorimetry determines the temperatures and the heats of glass transition, which indicate that the glass temperature is raised, when the enthalpy is increased and the entropy reduced, which is achievable by Diphenylbismaleimide and 2-Bromophenylmaleimide with their large side groups appropriate for intermolecular forces and steric hindrance. Keywords: Thermodynamic, heat resistant, burning behaviour, brittleness, toxicity. |
Abstract : Innovations in Polymer Applications - Plastic Packaging
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Abstract: Polymer materials are used in several industrial sectors such as, paints and varnishes, packaging, and the automotive sector. The countless applications of this type of material stem from several factors such as lightness and ease of processing when compared to metals and ceramics. The possibility of chemical modification of polymers is worth mentioning, which can result in a new material with mechanical properties superior to those of the original ones. Another unique characteristic of polymer material is related to the ease with which they can be mixed with other elements (vegetable and synthetic fibers, metals, ceramics) to obtain a composite or hybrid material, thus expanding the spectrum of polymer applications. In this sense, the present work aims to show the uses of polymers in the packaging segment, addressing the main physicochemical and mechanical characteristics that are necessary for manufacturing packaging items as well as innovative technologies to obtain those materials. Keywords: Polymer, film, packing, product, researches. |
Editorial: Climate Change and Economy of Africa
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Abstract : Properties and Applications of Biodegradable Polymers
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Abstract: Biodegradable materials are one of the major discussable matters in the modern world. To keep and produce environment-friendly products for our daily usage the utilization of degradable materials is increasing at a high rate. The modern world wants sustainable products which will not bring about any harm to the environment. Products made from plastics are sustainable but they cause great harm to our environment due to lack of degradation property. After the end of our usage, these materials can sustain for a long time without any degradation which causes a supreme level of loss to our environment. But if we can produce products by using biodegradable raw materials, they will be degraded by the action of bio-organisms hence our environment will be protected from a great loss. So, it has become a crying need for us to use biodegradable raw materials in our products. The materials which are not biodegradable cause a great pollution especially soil pollution. To protect the world from the cruel humiliation of waste, it has become an overwhelming necessity to manufacture biodegradable products, which can quickly be degraded in the environment, from our daily useable items. The materials contain almost all the properties which are suitable for our environment. Already these materials have been using in several sectors and showing their applications for their friendly properties. Keywords: Degradable, sustainable, bio-organisms, crystallinity, natural, synthetic. |