Károly Dobrovszky

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

Abstract 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 molding 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.

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.

Alternative, New Method for Predicting Polymer Waste Stream Contents

In order to achieve the desired polymer recycling standards, precise estimations are needed about the composition of the polymer waste streams. The technologies that are currently used for this purpose, such as the infrared spectroscopy and the pyrolysis are neither time nor energy efficient as the processes may take up to hours, moreover the results are usually concluded by only analyzing small fractions of the waste streams. Meanwhile, as the polymer consumption of the world is increasing, the recycling and recovery rates demanded by numerous laws and restrictions are getting higher as well. The aim of this paper is to introduce a new technology that utilizes centrifugal force to separate the different polymer components of a sample in a melted state, containing the most common polymers found in a regular waste stream. After the separation, using the calculation method that is described, the exact ratio of the different materials can be given as well. In order to show the possibilities hidden in this technology, two samples, containing PA/PS/PP and PET/PA/PS/PP respectively, were separated and analyzed. The promising results were verified using optical microscopy as well as Raman spectroscopy.

Temperature dependent separation of immiscible polymer blend in a melted state

The density and the spectral fingerprint of a compounded blend or composite vary widely depending on the type of the components and their composition. However, the currently used polymer separation techniques, such as density-based and optical sorting systems are not suitable for recovering these materials fully due to the physical-chemical bonding between the components. The application of a novel separation principle creates the opportunity to enrich the blend fractions to neat, homogeneous zones in a melted state by utilising centrifugal force. In this study three different types of plastics: high density polyethylene, polystyrene and polyethylene terephthalate were deeply investigated in order to understand the separability of their blends as a function of rotation time and melt temperature. The results showed that the separation of polymer mixtures and blends depends strongly on the viscosity and bulk density at a given temperature, and the initial particle size also has a significant impact.

Effects of Phase Inversion on Molding Shrinkage, Mechanical, and Burning Properties of Injection-molded PET/HDPE and PS/HDPE Polymer Blends

ABSTRACT 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 molding shrinkage depends significantly on the dispersed phase. Due to the heterogeneity and lack of adhesion between the phases, tensile strength differed from the linear mixing role, particularly in the case of polyethylene matrix. Depending on which component formed the continuous phase of blends, major differences were detectable during the flammability test. GRAPHICAL ABSTRACT

Influence of the phase inversion on mould-shrinkage, mechanical- and burning properties of polymer blend

Blending polymers is an effective method to develop novel materials, tailoring the properties of the components. However, different morphology structures can be formed during the preparation, which could result in a wide diversity of mechanical and physical properties. The properties of polymer blends are most significantly influenced by the emerging range of phase inversion, which depends on the composition ratio and the viscosity ratio. In this paper various blends were prepared, utilizing polyethylene terephthalate (PET), polystyrene (PS) and two high density polyethylenes (HDPE), which differ in flowability. After preliminary homogenization by twin screw extruder, standard injection moulded specimen were prepared in order to present the effects of phase inversion on tensile properties, shrinkage and burning characteristics in binary polymer blends.

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.