Ferenc Ronkay

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.

Effect of Graphite and Carbon Black Fillers on the Processability, Electrical Conductivity and Mechanical Properties of Polypropylene-Based Bipolar Plates

This study investigates the hybrid effect between graphite and carbon black in a polypropylene (PP) matrix, based on optical microscopy. PP sheets filled with various types of carbon black and graphite were prepared, and the effects of fillers on the flowability, electrical conductivity and mechanical properties were investigated. The effects of three kinds of carbon black with different specific surface areas (65, 770, 1400 m2/g) on the increase of conductivity in the polypropylene (PP) matrix were compared. The best performance was observed when the carbon black with the highest specific surface was used; therefore it was used for preparing the hybrid-filled (graphite – carbon black) materials by melt blending. Optical microscopic studies proved that the carbon black exerted not only a direct but also an indirect influence on the conductivity and on the mechanical properties of the hybrid composites, as it influenced the distribution of graphite significantly. At lower graphite contents the material became more flexible because of the better dispersion of graphite, but at higher carbon black contents the stiffness increased significantly.

A Probe on the Failure Mechanism in Rubber-Modified Epoxy Blends: Morphological and Acoustic Emission Analysis

In this work, diglycidyl ether of bisphenol A based epoxy resin (DGEBA) was modified with varying amounts of two liquid rubbers: carboxyl terminated copolymer of butadiene and acrylonitrile (CTBN); and a hydroxyl terminated polybutadiene (HTPB), using an anhydride hardener. The ultimate aim of this study was to investigate the failure mechanism operating in the rubber-modified epoxies and to evaluate this by correlating these results with the miscibility and interfacial adhesion between the components and the morphology of the cured network. Some of the mechanical and fracture properties, which are associated with the two-phase particulate morphology, were investigated. The visoelastic behavior of modified epoxies was also analyzed and variations in the shift of T g values in toughened epoxies were explained. The samples were carefully analyzed by an acoustic emission technique to investigate the failure mechanism operating in them. From the response of force and number of acoustic events as well as from the amplitude of acoustic events, we were able to explain the failure mechanisms in the elastomer incorporated epoxy resins supplemented by morphological evidence.

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.

Effect of processing technology on the morphological, mechanical and electrical properties of conductive polymer composites

Abstract Conducting carbon/polypropylene (PP) and carbon/poly(butylene terephthalate) (PBT) composites containing crystalline natural graphite and carbon black (CB) were prepared by compression and injection molding. The effect of the processing technology on the electrical, mechanical, and morphological properties was investigated. Determination of the constant torque at the end of the mixing process and differential scanning calorimetric (DSC) measurements showed that graphite had better connectivity with the more polar matrix (PBT) than with the less polar one (PP). Scanning electron microscopy (SEM) studies showed that compression molding results in a homogeneous structure, while injection molding results in a skin-core structure with different orientations. Layered electrical conductivity studies showed that the electrical conductivity of the compression molded samples did not change along the thickness of the sample, while that of the injection molded samples changed throughout the material, which is due to the different structures developed with each type of processing.

The Effect of Pre-Electron Beam Irradiation of HDPE on the Thermal and Mechanical Properties of HDPE/PET Blends

The effect of electron beam (EB) irradiation of high density polyethylene (HDPE) on polyethylene-terephthalate (PET)/HDPE blends has been investigated. The HDPE component was radiation treated before the blend was melt mixed. Although the radiation treatment of HDPE component with 50-200 kGy caused some decrease in the tensile strength and elasticity modulus, the maximum tensile elongation of the blend showed a significant increase (+40%) at optimum dose (100 kGy). The DSC results and the scanning electron microscope images of the fracture surfaces also showed the benefit of a 100 kGy EB-dose in the connection the otherwise thermodynamically incompatible part of the blend.

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.

Effect of solid-state polycondensation on crystalline structure and mechanical properties of recycled polyethylene-terephthalate

Solid-state polycondensation process of recycled polyethylene-terephthalate and its effect on crystalline structure and mechanical properties were investigated. A three-phase morphological model was applied for the evaluation of crystalline structure, while mechanical properties were determined by dynamic mechanical analysis. The effect of solid-state polycondensation process on morphology was investigated and described in detail. A new method was used to analyze the effect of solid-state polycondensation process on mechanical properties. Relationship was found between evolved crystalline structure and storage modulus of samples.

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