Műanyag hulladékok hasznosítása és új termék létrehozása polimer blendek és kompozitok fejlesztésével = Development of polymer blends using recycled plastics

A kutatási időszakban a vegyes műanyaghulladék értéknövelt hasznosítására fejlesztettem ki új eljárást, amelynek segítségével magas műszaki követelményeknek megfelelő alkatrészt gyártását is megvalósítottam. A kutatás első felében a vegyes műanyag hulladékot eredeti polimerek keverékével modelleztem és ezeket vizsgáltam mechanikai, valamint morfológiai szempontból. Elsőként a polimer blend-morfológiák kialakulását és tulajdonságait tanulmányoztam, majd kutatásaimat kiterjesztettem üvegszál-erősítéses rendszerekre is. A megfigyelések alapján egyszerű morfológiai modelleket hoztam létre, amelyekkel jól magyarázhatóak a különböző összetételű blendek mechanikai tulajdonságainak változásai. A munka során kifejlesztett új kritikus szálhossz meghatározási módszer különösen nagy jelentőséget kap, mivel az extrudálás és fröccsöntés jelentős száltördelődést eredményez. A kutatások következő fázisában a vegyes műanyaghulladék adalékolásának optimalizálásán dolgoztam. Többféle égésgátlóval, kompatibilizáló-szerrel és stabilizátorral kísérleteztem, amelyekkel sikerült nagymértékű minőségnövekedést elérni. Az kifejlesztett másodlagos nyersanyag így akár a gépjárműiparban is hasznosítható lenne. Ennek alátámasztására egy autóipari alkatrészt, valamint annak gyártószerszámát készítettük el. Az általunk fejlesztett anyagból fröccsöntött terméket egy autóiparban általánosan használt műszaki műanyaggal összehasonlítva a felhasználáshoz megfelelő értékeket kaptunk. | An upgraded recycling technology for mixed plastic waste was developed in the last research project, allowing even the production of parts with high technical requirements. In the first half of the project the plastic was modeled by a mixture of virgin polymers and these were studied from the mechanical and morphological viewpoints. First the development and properties of polymer blend morphologies were studied then the research was extended also for glass fiber reinforced systems. Based on the observations simple morphological models were developed allowing good explanation of the property changes in blends of varying compositions. The new critical fiber length measurement method is especially important, as the extrusion and injection molding steps are accompanied by significant fiber fragmentation. In the next phase of the research the additive system to be used with mixed plastic wastes was optimized. Experiments were performed with various flame retardants, compatibilizers and stabilizers which resulted in a significant quality improvement. The secondary raw material developed could be used even in the automotive industry. In order to prove this and automotive part and its production mold was produced. A comparison of the injection molded product made form the material developed by us was compared with an engineering plastic widely used by the automotive industry yielded favorable results

Alternative, new method for predicting polymer waste stream contents

Preparing polymer blends is an effective way to tailor the good properties of plastics but the most commonly used polymers are incompatible with each other. Therefore, to reduce the interfacial tension and to achieve finer and stable morphology, a suitable copolymer or compatibilizer has to be added to blends in order to establish new interactions between the phases. However, it is difficult to determine the required amount of compatibilizers in polymer blends. As an outcome of the present research a novel separation method was developed, where the blends are investigated in melted state, utilising centrifugal force to determine the adequacy of compatibilizers. The effectiveness of styrene/ethylene/butylene/styrene block copolymer grafted with maleic anhydride (SEBS-g-MA) was verified by blending two immiscible plastics: polystyrene (PS) and high density polyethylene (HDPE). FTIR measurements were carried out to support the results of optical microscopy regarding the purity of separation. Comparing the results of morphology, rheology and mechanical properties with the novel separation method, it seems that investigation of compatibilization effect in a melted state would be suitable for predicting the adequacy of compatibilizer in blend. The minimum required amount of compatibilizer was also detectable, wherein the stress-strain curves begins to change significantly and the impact properties starting to improve in PS/HDPE blend

Investigation of morphology of recycled PET by modulated DSC

During research injection molded samples were made from recycled poly(ethylene terephthalate) (PET). Morphological properties of samples were investigated by modulated differential scanning calorimetry (MDSC). Total heat flow was separated in two parts, reversing and non-reversing heat flow during measurements. Relationships were found between crystallization and melting processes: the initial crystallinity equals to the non-reversing melting, and the post-crystallization processes equals to reversing melting

Time dependence of morphology and mechanical properties of injection moulded recycled poly(ethylene-terephthalate)

During research, injection moulded samples were prepared from recycled poly(ethylene-terephthalate) granulate, and their mechanical properties were investigated as a function of time. To understand the changes in mechanical properties, both morphology of injection moulded samples and recycled granulates were investigated. A three-phase morphological model was applied for the evaluation of morphological properties while mechanical properties were determined by tensile and impact tests. Relationship was found between morphological and mechanical characteristics as a function of time elapsed since production. Crystalline ratio, tensile strength, and modulus of injection moulded specimens increased while impact strength decreased in the four weeks after production

Effects of SEBS-g-MA on rheology, morphology and mechanical properties of PET/HDPE blends

The effects of additive styrene/ethylene-butylene/styrene copolymer grafted with maleic anhydride (SEBS-g-MA) were investigated on the rheology, morphology and mechanical properties of a polyethylene terephthalate (PET) / high density polyethylene (HDPE) blend. The ratio of the two components was changed in small increments to track phase inversion. The rheology measurements show that SEBS-g-MA acts differently on HDPE and PET, as different morphologies are formed due to viscosity ratio change. With the help of electron microscopy various phases after extrusion and after injection moulding were revealed and identified. Because of the high viscosity of HDPE the co-continuous morphology was immediately formed when PET reached 30 vol%. The range of the co-continuous structure of the blend was wider when SEBS-g-MA was added, and the elongation at break also improved as additive content increased, without a significant strength decrease. The divergence of the mechanical properties from the theoretical value, i.e. the value determined by the mixing rule, can be explained by the changing phase structure

Influence of morphology and compatibilizer on burning behavior of PET/HDPE blend

Blending polymers offers a wide range of possibilities to tailor the properties of the components and to produce new materials. However, the most commonly used plastics are not compatible with each other. To increase compatibility between the phases, copolymer or compatibilizer has to be added to polymer blends, resulting in a finer morphology and better impact properties. Polymer blends are widely used in engineering where burning behavior can be a main criterion of application. It became clear that the fire resistance of blends can be improved by using flame retardant or different fillers. But the number of papers that examine the effects of morphological change or adding additives in polymer blends is quite few. In this paper polyethylene terephthalate (PET) and high density polyethylene (HDPE) were blended with styrene/ethylene/butylene/styrene block copolymer grafted with maleic anhydride (SEBS-g-MA), in order to present its effects on the morphology, rheology and burning characteristics

Investigation of compatibilization effects of SEBS-g-MA on polystyrene/polyethylene blend with a novel separation method in melted state

Preparing polymer blends is an effective way to tailor the good properties of plastics but the most commonly used polymers are incompatible with each other. Therefore, to reduce the interfacial tension and to achieve finer and stable morphology, a suitable copolymer or compatibilizer has to be added to blends in order to establish new interactions between the phases. However, it is difficult to determine the required amount of compatibilizers in polymer blends. As an outcome of the present research a novel separation method was developed, where the blends are investigated in melted state, utilising centrifugal force to determine the adequacy of compatibilizers. The effectiveness of styrene/ethylene/butylene/styrene block copolymer grafted with maleic anhydride (SEBS-g-MA) was verified by blending two immiscible plastics: polystyrene (PS) and high density polyethylene (HDPE). FTIR measurements were carried out to support the results of optical microscopy regarding the purity of separation. Comparing the results of morphology, rheology and mechanical properties with the novel separation method, it seems that investigation of compatibilization effect in a melted state would be suitable for predicting the adequacy of compatibilizer in blend. The minimum required amount of compatibilizer was also detectable, wherein the stress-strain curves begins to change significantly and the impact properties starting to improve in PS/HDPE blends

Alternative polymer separation technology by centrifugal force in a melted state

In order to upgrade polymer waste during recycling, separation should take place at high purity. The present research was aimed to develop a novel, alternative separation opportunity, where the polymer fractions were separated by centrifugal force in melted state. The efficiency of the constructed separation equipment was verified by two immiscible plastics (polyethylene terephthalate, PET; low density polyethylene, LDPE), which have a high difference of density, and of which large quantities can also be found in the municipal solid waste. The results show that the developed equipment is suitable not only for separating dry blended mixtures of PET/LDPE into pure components again, but also for separating prefabricated polymer blends. By this process it becomes possible to recover pure polymer substances from multi-component products during the recycling process. The adequacy of results was verified by differential scanning calorimetry (DSC) measurement as well as optical microscopy and Raman spectroscopy

Effects of phase inversion on mold shrinkage, mechanical and burning properties of injection molded PET/HDPE and PS/HDPE polymer blends

The study deals with the effects of forming morphological structures in immiscible polymer blends, where polyethylene terephthalate and polystyrene were mixed with high density polyethylene. While tracking phase inversion the composition ratio was altered with small increments by volume. The results revealed that the mold shrinkage depends significantly from the dispersed phase. Due to the heterogeneity and lack of adhesion between the phases tensile strength differed from the linear mixing role, particularly in case of polyethylene matrix. Depending on which component formed the continuous phase of the blends major differences were detectable during flammability test