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  • Rijksuniversiteit Groningen

    Improving the properties of polymer blends by reactive compounding

    Proefschrift

    Ter verkrijging van het doctoraat in de Wiskunde en Natuurwetenschappen aan de Rijksuniversiteit Groningen op gezag van de Rector Magnificus Dr. F. van der Woude In het openbaar te verdedigen op vrijdag 12 juni 1998 des namiddags te 2. 45 uur precies

    door

    Douwe Jurjen van der Wal

    Geboren op 28 april 1964 te Leeuwarden

  • Promotores Prof. dr. ir. L.P.B.M. Janssen Prof. dr. ir. H.W. Hoogstraten

  • contents

    CONTENTS

    CHAPTER 0 IMPROVED PROPERTIES OF POLYMERIC MATERIAL BY MEANS OF MIXING TWO POLYMERS 1

    1 Introduction 1 1.1.1 Theory of compatibilisation 2 1.1.2 Mechanical properties of blends 3 1.2 What has been done in earlier work 3 2 This thesis 7

    References 8

    CHAPTER 1 A NEW METHOD FOR REACTIVE BLENDING 10

    Abstract 10 1 Introduction 10 2 Theory 11 2.1 Experimental set-up 13 2.2 Analysis 13 3 Experimental results 14 4 Concentration profiles 17 4.1 The materials formed in the dispersed phase 20 5 Conclusions 23

    Nomenclature 23 References 24

    CHAPTER 2 THREE DIMENSIONAL FLOW MODELLING OF A SELF WIPING COROTATING TWIN SCREW EXTRUDER, THE KNEADING SECTION

    25

    Abstract 25 1 Introduction 25 2 Mathematical method 26 3 Definition of the problem 28 3.1 Geometry and mesh 28 3.2 Boundary conditions 30 4 Results 31 4.1.1 The axial velocities 31 4.1.2 The axial backflow volume 32 4.2 The transverse velocities 34 4.3 The pressure difference over one kneading element 35 4.4 The shear and elongation rate 37 4.5 The influence of the stagger angle between the kneading elements

    on the flow 39 4.6 The influence of the viscosity on the flow 43

  • contents

    4.7 The adiabatic axial temperature rise 45 4.8 Experimental validation 46 5 Discussions and conclusions 47

    Nomenclature 48 References 49

    CHAPTER 3 THREE DIMENSIONAL FLOW MODELLING OF A SELF WIPING COROTATING TWIN SCREW EXTRUDER, THE TRANSPORTING SECTION

    51

    Abstract 51 1 Introduction 51 2 Mathematical method 53 3 Definition of the problem 55 4 Results and discussion 57 4.1 The throughput 57 4.2 The flow profile 58 4.3 The backflow 61 4.4 The axial pressure gradient 63 4.5 The shear and elongation rate 64 4.6 The adiabatic temperature rise 67 4.7 The influence of viscosity 68 5 Conclusions 71

    Nomenclature 71 References 73

    CHAPTER 4 THREE DIMENSIONAL FLOW AND TEMPERATURE MODELLING IN THE CHANNEL OF THE COROTATING TWIN SCREW EXTRUDER

    74

    Abstract 74 1 Introduction 74 2 Definition of the problem 75 2.1 The geometric model 75 2.2 The flow problem 77 2.3 The temperature problem 78 2.4 The temperature profile for a larger length of the channel 79 3 Results 79 3.1 Three dimensional temperature calculation, an example 80 3.2 The influence of the heat conductivity coefficient 86 3.3 The influence of reaction heat on the temperature profile 88 4 Conclusions 90

    Nomenclature 90 References 91

  • contents

    CHAPTER 5 THE ROLE OF DIFFUSION AND REACTION IN REACTIVE COMPOUNDING

    92

    Abstract 92 1 Introduction 92

    Diffusion 92 Kinetics 93 Modelling 93

    2 Experimental set-up 94 2.1 The measurements of the diffusion coefficient with FRAP 95 3 Results 97 3.1.1 The diffusion coefficient 97 3.1.2 Variation of the temperature 98 3.1.3 Diffusion coefficients of binary diffusion in a polymer 102 3.2.1 Kinetics 105 3.2.2 Measurements of the reaction velocities 106 4 Modelling the concentration profiles and Mn distribution of

    the alloying agent 107 5 Discussion and conclusions 112

    Nomenclature 114 References 114

    CHAPTER 6 MODELLING AND EXPERIMENTAL EVALUATION OF THE TEMPERATURE IN A COROTATING TWIN SCREW EXTRUDER

    115

    Abstract 115 1 Introduction 115 2 Modelling of the average axial temperature in the corotating

    twin screw extruder 116 2.1 The geometry and the throughput of the extruder 116 2.2 The temperature model 119 2.3 The viscous dissipation 119 2.4 The temperature profile 120 3 Experimental 122 3.1 Extrusion and viscosity 122 4 Results 123 4.1 The power 123 4.2.1 The temperature profile in the partially filled section 126 4.2.2 The fully filled section 128 4.2.3 The temperature at the entrance of the kneading section 130 4.2.4 The heat transfer coefficient calculated ; the kneading section 132 4.2.5 The temperature of a blend (PS/HDPE) 133 5 Conclusions 135

    Nomenclature 135 References 137

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    CHAPTER 7

    MODELLING AND EXPERIMENTAL EVALUATION OF MIXING IN A COROTATING TWIN SCREW EXTRUDER

    138 Abstract 138

    1 Introduction to mechanical properties of blends 138 1.1 Mixing in the intermeshing corotating twin screw extruder 139 2 Modelling of mixing in the corotating-twin screw extruder 140 2.1.1 A simplified modelling of the average size of the dispersed phase of a blend

    142 2.1.2 Modelling of the average size of the dispersed phase of a blend 144 3 Experimental set up 146 4 Results and discussions 147 4.1 Modelling of the axial development of the average size of the dispersed phase

    147 4.2 The influence of the rotation speed of the screws 152 4.3.1 Comparison between measurements and modelling, PS/HDPE blends 155 4.3.2 Comparison of our computer modelling with the measurements of others 156 5 Conclusions 157

    Nomenclature 158 References 159

    CHAPTER 8 MODELLING AND EXPERIMENTAL EVALUATION OF REACTIVE COMPOUNDING IN A COROTATING TWIN SCREW EXTRUDER

    161

    Abstract 161 1 Introduction 161 2 Modelling reactive compounding 164 2.1 The different steps taken in our modelling 164 2.2 Measuring and modelling the reaction velocity of monomer in the melt,

    an example 166 2.3 Modelling and measuring the size of the dispersed phase, an example 170 2.4 Modelling of the diffusion of monomer out of the dispersed phase

    , an example 171 2.5 Modelling of the conversion of monomer in the dispersed phase 171 3 Experimental set-up 172 3.1 Experiments with the Brabender mixing chamber 173 3.2 Reactive blending in the extruder 174 3.3 Reactive blending of PS/PP with MAH/S 175 3.4 Experiments with an improved screw geometry 176 4 Comparison between model and experiments 178 4.1 The measured and modelled conversions of MAH in the

    dispersed phase (HDPE) versus rotation speed and throughput 179 4.2 The conversion of acrylates in the dispersed phase of PS/HDPE 180 5 The grafted monomer on HDPE in the dispersed phase of PS/HDPE 182

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    6 Conclusions 185 Nomenclature 186 References 186

    CHAPTER 9 IMPROVED TOUGHNESS VERSUS PROCESSING PARAMETERS

    188

    Abstract 188 1 Introduction 188 1.1 Theory, mechanical properties and morphology 189 1.2 The conversion in the dispersed phase of a PS/HDPE blend 190 2 Experimental set-up, the extruder 192 2.1 Experimental set-up, the materials 192 2.2 Analysis 193 3 Results 193 3.1 Material choice for the dispersed and matrix phase 194 3.2 Material properties versus processing conditions 194 3.3 Toughness and elongation at break 197 3.4 The influence of rotation speed on the Notched Izod Impact values 199 3.5 Impact values versus conversion and rotation speed 202 3.6 The relation between elongation at break, and an efficient alloying agent 203 4 Discussion 207 5 Conclusions 209

    Nomenclature 210 References 210

    CHAPTER 10 THE LINK BETWEEN THE GLASS TRANSITION TEMPERATURE, THE ALLOYING AGENT FORMED, AND THE MECHANICAL PROPERTIES OF THE BLEND

    211

    Abstract 211 1 Introduction 211 2 Experimental 215 2.1 Analysis 216 3 Results 217 3.1 The conversion of monomer in the dispersed phase 217 3.2 The glass and melt transition temperature and toughness versus the rotation

    speed of the screws 220 4 The Notched Izod Impact value, Tg, and the alloying agent 226 5 The influence of the type of dispersed phase 229 6 Conclusions 230 6.1 Theoretical considerations 231

    Nomenclature 232 References 232

  • Dankwoord

    Het heeft even geduurd maar nu is het toch klaar. Direct nadat mijn contract bij het NWO afliep werd ik bij Philips gevraagd om te komen werken als kunststof specialist. Dit heb ik gedaan om op deze manier ook de toepassingen en de markt van kunststoffen te leren kennen. Maar ja om dan ook nog een proefschrift af te maken bleek een zware klus. Om het toch af te ronden ben ik een aantal hoogleraren dank verschuldigd. Als eersten wil ik natuurlijk mijn promotors prof. Dr. Ir. H.W. Hoogstraten en vooral mijn eerste promotor Prof Dr. Ir. L.P.B.M. Janssen noemen. De grote vrijheid die ik heb gekregen om mijn eigen methode te bedenken en te onderzoeken heeft geresulteerd in een patent op deze methode (een publikatie met een gouden randje). Hun begeleiding bij het doen van dit onderzoek en het publiceren hiervan heeft (hun en mij) zeer veel tijd gekost, waarvoor dank. Verder wil ik de hoogleraren uit mijn leescommissie bedanken die bestond uit Prof. dr. G. Hadziioannou, Prof. Dr. Ir. L.L. van Dierendonck, Prof. Dr. Ir. A.A.C.M. Beenackers. Maar ook andere hoogleraren hebben bijgedragen door apparatuur beschikbaar te stellen of door middel van waardevolle discussies waarbij ik vooral Prof dr. G. Hadziioannou, Prof. dr. G. ten Brinke, en Prof. dr. A. J. Pennings wil bedanken. Van onschatbare waarde voor mij waren de technische medewerkers zoals Laurens Bosgra, Luuk Balt, Harry Nijland, Gert Alberda v Ekenstein, Marcel de Vries, Adams Verweij, Dirk Grijpma, Joop Vorenkamp, Karel van der West, Jan Henk Marsman, Berend Quant, Yannis Pappantoniou en al die anderen bij Technische Scheikunde zoals Gerda Everts en de ander dames van het secretariaat, en Polymeerchemie. Ec