Presentation is loading. Please wait.

Presentation is loading. Please wait.

Micro-Moulding of Polymers: Process and Product Assessments Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, IRC in Polymer Engineering, University.

Similar presentations


Presentation on theme: "Micro-Moulding of Polymers: Process and Product Assessments Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, IRC in Polymer Engineering, University."— Presentation transcript:

1 Micro-Moulding of Polymers: Process and Product Assessments Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, IRC in Polymer Engineering, University of Bradford, Bradford UK. P S Allan, G. Greenway and P Hornsby, Wolfson Centre for Materials Processing, Brunel University, Uxbridge, UK Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, IRC in Polymer Engineering, University of Bradford, Bradford UK. P S Allan, G. Greenway and P Hornsby, Wolfson Centre for Materials Processing, Brunel University, Uxbridge, UK

2 Contents Micromoulding Process technology Results of studies at Bradford Process dynamics Process interaction Product properties Micromoulding Process technology Results of studies at Bradford Process dynamics Process interaction Product properties

3 Purpose built micro injection process Servo-electric injection Automatic parts handling Clean room filtration Modular Battenfeld Microsystem 50

4 Metering Piston Hopper Shut off valve Extrusion screw Heated Regions Injection piston

5 Operation Cycle

6 Dynisco PCI 4011 Piezo load transducer Dynisco PCI 4006 piezo load transducer The Data Acquisition Setup Temposonics R series displacement transducer J-type thermocouples

7 1 Process Measurement – Data Capture Injection Pressure Cavity Pressure Ram Displacement Ram Velocity 3 Temperature Channels Injection Pressure Cavity Pressure Ram Displacement Ram Velocity 3 Temperature Channels Max sampling rate ~ Hz

8 Mould temperature investigation

9 Hypothesis The high surface area to volume ratio of micro-moulded products allows rapid removal of heat from the product through the cavity wall Mould temperatures should be higher than those used in conventional IM to prevent premature solidification and part-filled products The high surface area to volume ratio of micro-moulded products allows rapid removal of heat from the product through the cavity wall Mould temperatures should be higher than those used in conventional IM to prevent premature solidification and part-filled products

10 Step plaque moulding Material: HAPEX (40% sintered hydroxyapatite HDPE matrix) Produced by IRC in Biomaterial Science Queen Mary and Westfield College, London Material: HAPEX (40% sintered hydroxyapatite HDPE matrix) Produced by IRC in Biomaterial Science Queen Mary and Westfield College, London

11 Cavity Pressure – Hapex, step plaque 80C 50C 20C

12 Product Mass – Hapex, step plaque 0.12% variation

13 Mould temperature - conclusions For products ~25mg recommended mould temperatures for standard injection moulding can be used with confidence for the Hapex material Further investigations to be performed at smaller length scales For products ~25mg recommended mould temperatures for standard injection moulding can be used with confidence for the Hapex material Further investigations to be performed at smaller length scales

14 High shear rate experiments

15 Calculated wall shear rates 0.1 x 0.1mm 0.2 x 0.2mm 0.5 x 0.5mm 1.0 x 1.0mm

16 In-process rheometry Measurements performed on a 30 tonne Cincinnatti Milacron servo-electric injection moulding machine with a custom rheometric nozzle Dynisco Pressure Transducer M Dynisco Pressure Transducer M Capillary die inserts Capillary die inserts 0.5 x 8.0 mm 0.5 x 0.25 mm 1.0 x 16 mm 1.0 x 0.25 mm Thermocouple

17 High-shear capillary rheometry test results

18 Shear heating effects Source: Anthony Bur, Steven Roth, NIST

19 Top Hat Cavity Large diameter = 1.0mm Small diameter = 0.5mm Gate dimension 0.1 x 0.2mm Material BP Rigidex 5050 HDPE Large diameter = 1.0mm Small diameter = 0.5mm Gate dimension 0.1 x 0.2mm Material BP Rigidex 5050 HDPE

20 Molecular weight measurement Sample material taken from runner system and cavity Gel Permeation Chromatography (GPC) analysis performed by Rapra Technology Ltd on each sample to determine molecular weight distribution Sample material taken from runner system and cavity Gel Permeation Chromatography (GPC) analysis performed by Rapra Technology Ltd on each sample to determine molecular weight distribution

21 Molecular weight distributions Source: RAPRA UK

22 High shear investigation - conclusions The process contains shear rates orders of magnitude higher than those encountered in conventional IM Viscosity curves behave predictably in this region Shear heating will be a factor Stable materials show no sign of degradation Temperature sensitive materials? The process contains shear rates orders of magnitude higher than those encountered in conventional IM Viscosity curves behave predictably in this region Shear heating will be a factor Stable materials show no sign of degradation Temperature sensitive materials?

23 Surface feature replication

24 Plaque cavity 25 x 2.5 x 0.25 mm Fabricated using micro-milling technique Kern machine 0.2mm cutter at rpm. Left in an unpolished state. Plaque cavity 25 x 2.5 x 0.25 mm Fabricated using micro-milling technique Kern machine 0.2mm cutter at rpm. Left in an unpolished state.

25 Surface feature replication - gate AFM scan size 75 µm x 75 µm Pitch of scroll marks ~ 6µm AFM scan size 75 µm x 75 µm Pitch of scroll marks ~ 6µm Cavity Product

26 Surface feature replication - gate AFM scan size 75 µm x 75 µm Cavity Product

27 Surface feature replication -downstream AFM scan size 75 µm x 75 µm Pitch of scroll marks ~ 6µm AFM scan size 75 µm x 75 µm Pitch of scroll marks ~ 6µm Cavity Product

28 Surface feature replication - comments Mould features of the order of a few µm are accurately replicated on the product assuming pressure is sufficient Further work to be performed to investigate the limit to which a feature is adequately moulded on a product Mould features of the order of a few µm are accurately replicated on the product assuming pressure is sufficient Further work to be performed to investigate the limit to which a feature is adequately moulded on a product

29 Morphology Measurement Component sectioned using glass-knife microtomy Surface is etched using potassium permanganate solution to produce representative surface Surface imaged using microscopic technique (TEM, AFM etc) Component sectioned using glass-knife microtomy Surface is etched using potassium permanganate solution to produce representative surface Surface imaged using microscopic technique (TEM, AFM etc) Surface following microtomySurface following etching

30 Morphology Measurements - Structure Nano-indent Crystal Structure Crystal Structure

31 Morphology Measurements – Spherulite size

32 Morphology Variation Line of indents 25µm separation 800 µm

33

34

35 Morphology Measurements – Amorphous layer

36 The Rondol Micro-Injection Compounder

37

38 Prism twin-screw extruder

39 The Rondol Micro-Injection Compounder Advantages: Minimise residence time of polymer in plasticising screw Exposure to single heating/cooling cycle Positive displacement allows use of low viscosity materials Advantages: Minimise residence time of polymer in plasticising screw Exposure to single heating/cooling cycle Positive displacement allows use of low viscosity materials

40 Operation

41 The Rondol Micro-Injection Compounder

42 Initial testing It works! Able to process low molecular weight materials It works! Able to process low molecular weight materials Dosing control can fluctuate Toggle clamp can result in flashing Dosing control can fluctuate Toggle clamp can result in flashing

43 Experimental Battenfeld Microsystem50 Stepped plaque cavity 60mg total shot mass HDPE 5050 Injection speed – 200, 400, 600 mm/s Screw speed 40revs/m Melt temp 200C Mould temp 50C Battenfeld Microsystem50 Stepped plaque cavity 60mg total shot mass HDPE 5050 Injection speed – 200, 400, 600 mm/s Screw speed 40revs/m Melt temp 200C Mould temp 50C


Download ppt "Micro-Moulding of Polymers: Process and Product Assessments Dr Ben Whiteside, Dr Mike Martyn, Prof Phil Coates, IRC in Polymer Engineering, University."

Similar presentations


Ads by Google