(2013 - 2017)
Natural and synthetic polymers and plastics made of them, are an integral part of the urban environment in many different areas . Polyethylene is one of the most widely used polymers. Production of films of different kinds and purposes is determined by the specific properties of polyethylene. Among the polymers and polymeric materials only a small portion can be considered non-flammable. The vast majority (including the above-mentioned polyethylene) undergoes a process of thermal destruction under the influence of a sufficient amount of energy, emitting a considerable amount of heat and smoke. Studies on the flammability of polymers and methods of its reduction are driven by factors of ecological, economic and safety aspects.
The experimental section describes a procedure for preparing a film material and a comparison of properties, with respect to the used filler: colloidal silica, calcium phosphate or hydroxyapatite. With Differential Scanning Calorimetry (DSC) we tested properties such as melting and crystallisation temperature, heat of fusion and the content of crystalline phase. Studies were carried out using the flammability test LOI UL-94 and microcalorimetry of pyrolysis-combustion to determine the burning rate, the limiting oxygen index as well as the rate and the amount of released heat. Optical microscopy was also used to examine the morphology of the polymer matrix.
On the basis of the results, the modification of polyethylene matrix was found effective. The addition of fillers had a significant impact on the mechanism of combustion of the investigated films. It revealed a reduction in burn rate, a reduction in rate and amount of released heat and an increase of the value of LOI. At the same time, there were no significant effects on the other properties of the composites. The most prominent flame retardant effect as compared to a pure polyethylene film was provided by hydroxyapatite. There was no occurrence of synergistic effect between the phosphorus compounds and the silica, so there is no reason to apply them in such combination as a mixture of fillers, giving the effect of fire retardant in the composite material.
Polyurethanes (PU) during the last 50 years have become one of the most developing polymers and it is almost impossible to find an industry field, where they are not used. This term concerns a wide range of materials, both expanded and non-expanded products. PUs are widely used in many applications as foams (flexible, semiflexible and rigid foams), elastomers, adhesives, fibers and obtained by the exothermic reaction of an oligomeric polyol (the substance which contains at least two hydroxyl groups) and polyfunctional isocyanates. PU foams are considered to be one of the most efficient materials for insulation with many desirable properties (very low conductivity, low density and water absorption, dimensional stability and high ecoeficiency index to save energy). Nowadays, rigid polyurethane foams are synthesized using vegetable-oil based polyols, which is connected to their abundance and economy. What is more, materials synthesized from renewable resources can almost fully replace their petrochemical analogs. Several types of vegetable oils have been already used, such as soy bean oil, palm oil, linseed oil and sunflower oil. Such oils are characterized by low amount of functional groups, however present in the structure unsaturated bonds can be successfully converted into hydroxyl groups. The great possibility is using waste cooking oil to synthesize polyol, but the biggest problem is low number of hydroxyl value and contaminations from food. This short communicate presents a discussion about the influence of various polyol systems on physical, mechanical and thermal insulation properties, as well as on the cellular structure of PU foams.
The process of bonding and adhesives are an important part of human life from the earliest times. Over the years, a development has evolved. Natural adhesives were increasingly replaced by synthetic, which allowed to obtain more permanent weld and glue together different types of materials. Despite the emergence of new industrial sectors which allowed to connect components such as soldering, welding, thermal bonding, rivets, screws or pins gluing process did not lose in significance. People are willing to use the features and ease of use adhesives. Ecological aspects, however, pay attention to the safety of the environment. Decreasing non-renewable sources and the growing amount of waste affects the market, on which to a greater extent firms appear with environmentally friendly technologies. An important field of biodegradable polymers are produced from renewable raw materials that do not affect negatively the environment. Nowadays, more and more research is conducted to increase the scope of their use.
The experimental section presents a method to prepare polylactide paper adhesives and the effects of additives on its properties. The first part a review of the latest scientific and patent literature towards polylactide biocomposite adhesives. This review shows a lack of studies on polylactide adhesives in the literature. This led to a series of experimental studies related to the selection of appropriate adhesive formulations, as well as additives favorably affecting the strength of the glued joints. The object of the study were the four compositions with the same concentration (polylactide dissolved in chloroform - primary composition, the composition containing pigments, the composition containing the essential oil and the composition with corn flour).
The resulting compositions were subjected to a series of experimental studies such as: rheological tests including measurements of viscosity and thixotropy, peel strength, wettability and penetration, content of solids and creep tests. The lifetime of adhesives were determined, and we finally propose a method and the respective conditions for their long-term storage.