heat transfer in polymers - national physical...

Martin Rides, Angela Dawson6 October 2004

Heat Transfer in Polymers

Heat Transfer in Polymers - summary

IntroductionHeat Transfer CoefficientThermal ConductivityIndustrial DemonstrationsNPLs Polymer Processing WebsiteSummary

Aim of the project

To help companies measure and model heat transfer in polymer processing

This should lead to:

Higher productivity (faster processing) Energy saving Fewer failures in service

Related project : AIMTECH

Eureka Project: AIMTECH

An associated Eureka project (AIMTECH) is progressingIts aim is to improve productivity of injection moulding

Main focus is on the moulds - reduce cycle times by using copper alloy moulds in injection moulding

NPL Role Measurement of the thermal conductivity of polymer melts (T,P) Understanding the role of the mould/melt interface:

Modelling heat transfer and the effect of uncertaintiesSix UK companies involved25k co-funding contributionClose fit with the DTI project

Tasks in the DTI ProjectHeat Transfer Coefficient

New facility Thermal Conductivity

Uncertainty analysis Extension of method to new materials

Simulation To identify the important data To help design equipment Moldflow & NPLs own software

Industrial Demonstrations Zotefoams Corus

Dissemination Web site, IAGs, PAA Newsletter articles, trade press articles,

measurement notes, scientific paper

Heat Transfer CoefficientIt is the heat flux per unit area (q) across an interface from one material of temperature T1 to another material of temperature T2 :

h = q/(T1 T2) units: Wm-2K-1

Boundary condition for process simulation

In injection moulding & compression moulding Polymer to metal

In extrusion & film blowing Polymer to fluid (eg air or water)

This project will build apparatus to measure heat transfer coefficient and investigate the significance of different interfaces to commercial processing

Heat Transfer Coefficient (heat transfer across an interface)

Features of apparatus being developedRoom temperature to 275 C, pressure to at least 500 barPolymer samples 2 to 25 mm thickInterchangeable top plate to investigate

Different surface finishes Effect of mould release agents

Option to introduce a gap between polymer & top plate Shrinkage, sink marks

Instrumented with thermocouples, fibre optics, heat flux sensors and calorimeter

Heat transfer apparatus

Side view

hot plate

cold plate

sample

Heat transfer apparatus

displacement transducer

cooling pipes thermocouples heat flux sensors pressure transducer port

mould face

heater element

sample

air gap

outer guard ring

PTFE seal

thermo-couple ports

fibre optic thermocouple port

displacement transducer

cooling pipes thermocouples heat flux sensors pressure transducer port

mould face

heater element

sample

air gap

outer guard ring

PTFE seal

thermo-couple ports

fibre optic thermocouple port

Modelling of key features

Effect of vertical thermocouple on distort the temperature field

Effect of an air gap

Effect of a thermocouple

TherMOL 1.0

Mould at 50 C

Polymer at 250 C

Simulation of Heat Transfer with Fibre Optic (left) & Thermocouple (right)

Comparison of thermocouple & fibre optic

50 C 250 C

Air GapMould at 50 C with air gap of 0, 0.5 & 1 mm

Polymer at 250 C

Pipe T piece and 80 mm diameter disc models

Effect of uncertainties in HTC

Effect of uncertainties in HTCThe Effects of Mould-Melt Heat Transfer Coefficient Upon Tf

Predictions For The 5 mm Thick Disc Model

50

51

52

53

54

55

10 100 1000 10000 100000 1000000

Heat Transfer Coefficient, W/(m2C)

Tim

e to

Fre

eze

Part

, s

1/10

x10Default Value

Minimum Value

Effect of uncertainties in HTCThe Effect Of Mould-Melt Heat Transfer Coefficient Upon Time To Freeze Part

For Discs Of Different Thickness

-2

0

2

4

6

8

10

12

14

0 5 10 15 20 25 30

Disc Thickness, mm

Perc

enta

ge V

aria

tion

In T

ime

To F

reez

e Pa

rtFr

om T

he S

tand

ard

Sim

ulat

ion

Res

ult

For T

he G

iven

Dis

c Th

ickn

ess,

%

Default Mould-Melt Heat Transfer Coefficient

Minimum Mould-Melt Heat Transfer Coefficient

1/10 Of Default Mould-Melt Heat Transfer Coefficient

*10 Default Mould-Melt Heat Transfer Coefficient

NPL Report DEPC-MPR 001

The Effect of Uncertainty in Heat Transfer Data on The Simulation

of Polymer Processing

J. M. Urquhart and C. S. Brown

http://libsvr.npl.co.uk/npl_web/search.htm

http://libsvr.npl.co.uk/npl_web/search.htm

Heat Transfer Coefficient Summary

Investigate effect of:

Different surface finishes/mould materials Mould release agents Air gap between polymer & top plate Shrinkage, sink marks

THERMAL CONDUCTIVITYMEASUREMENT

Angela Dawson

Thermal Conductivity

Sample Measurementcylinder

Guiding bar

Distance holderLower Piston

Thermalconductivityprobe

Heater bands

Line source probe apparatus

Measures at temperature and pressure conditions found in industrial polymer processing

Uncertainty Budget For NPL Line-Source Thermal Conductivity Probe (Atmospheric Pressure)

Value %

Proba bility Dis tribu tion

Di vis or Ci Uncertainty Contri bution %

Uncertainty S qu are d %

Vi or Veff

Ty pe A Re pe atability 15 .6@

2 s td de vs

Nor m al 2 1 7 .8 15 @ 1 s td de v 6 1 .0 7 8 9

Re pr oduci bility 13 .6@ 2 s td de vs

Nor m al 2 1 6 .8 01 @ 1 s td de v 4 6 .2 5 8 9

Ty pe B Non- uni for mity o f heat in put

0 .0 02 Rectangular 1 .73 1 0 .0 0116 1 .34 E-06

Non-unifor mity o f tem pera ture

0 .0 Rectangular 1 .73 1 0 .0 00 0 .00 0

S am ple heig ht 0 .0 Rectangular 1 .73 1 0 .0 00

0 .00 0

Ti me 0 .0 Nor m al 1 1 0 .0 00

0 .00 0

Calcul ati on of Uncertainty

S um of s quares 1 07 .3 % S qu are root of

s um of s quares 1 0 .4 %

M ulti plica tio n by k = 2 for 95% confi de nce le vel

20 .7% Fin al Uncertainty Value

Thermal Conductivity of PDMS (Atmospheric Pressure)

Thermal Conductivity of HDPE (Atmospheric Pressure)

Thermal Conductivity of HDPE (Atmospheric and 1000 bar Pressures)

Repeatability (95% confidence level) of thermal conductivity test data for one operator testing HDPE HCE000 from 170C to 50C

at 1000 bar pressure (green) and at ambient pressure (blue)

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

40 60 80 100 120 140 160 180Temperature, C

1000 bar repeatability 8%

Ther

mal

Cond

uctiv

ity, W

/mK

ambient pressure repeatability16%

Thermal Conductivity Uncertainty Analysis Summary

Picking data from literature expect uncertainty value +/- 50%Measurement of a typical thermoplastic at atmospheric pressure - total uncertainty value +/- 20.7%Measurement of a typical low viscosity polymer +/- 1.4% (repeatability)Measurement of a typical thermoplastic at atmospheric pressure expect +/- 16% (repeatability)Measurement of a typical thermoplastic at 1000 bar +/- 8% (repeatability)

Conclusion: Can improve on +/- 20.7% total uncertainty value

Action: Incorporate +/- 8% repeatability value into uncertainty budget Investigate repeatability contribution at elevated pressure and

incorporate result uncertainty budget

What is the commercial significance of this? Illustrated by Moldflow simulation

Moldflow model of HDPE Pipe T-piece

Changes In Cooling Times With Increasing Thermal Conductivity Values For T- Piece From Moldflow Simulation

Thermal Conductivity

Extending the scope of the measurement (at least six)

Nanoclay filled PPs 3

Rubber toughened PMMA 3

Rubber samples (Avon) softness project link 3

HDPE (Durapipe grade) used for uncertainty analysis 1

HDPE powder (rotational moulding grade) 1

Thermosets (Railko polyesters) 2

Glass filled nylon 1

PC 1

PS 1

ABS 1

Total 13 + 4 = 17

Nano-materials Thermal Conductivity (200 bar)

Comparison of thermal conductivity behaviour on cooling of virgin polypropylene (AAATJ000) with two polymer

nanocomposites (AAATJ001 and AAATJ002) at 200 bar pressure

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0 50 100 150 200 250

Temperature, C

AAATJ000 200barAAATJ001 200barAAATJ002 200barT

herm

al C

ondu

ctiv

ity, W

/mK




0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0 50 100 150 200 250

Temperature, C

AAATJ000 800barAAATJ002 800barAAATJ001 800bar

Ther

mal

Con

duct

ivity

, W/m

K




0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0 50 100 150 200 250

Temperature, C

AAATJ000 1200barAAATJ001 1200barAAATJ002 1200bar

Ther

mal

Con

duct

ivity

, W/m

K

Summary of Thermal Conductivity Study of Nano-clay Filled Polypropylene

Can measure thermal conductivity of polymer nano-composites at range of temperatures and pressuresAddition of nano-clay filler to polypropylene increases the crystallisation temperature of the polymerAddition of nano-clay filler to polypropylene can increase the thermal conductivity of the polymer across the processing range of temperatures New area of work would be to look at addition of nano-clays to range of polymers to determine effects of nano-clays on thermal conductivity and other physical properties of polymers

Thermal Conductivity of Rubber

thermal conductivity of AAATH000 rubber powder on heating and cooling from 50C to 250C at atmospheric

pressure

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0 50 100 150 200 250 300

Temperature, C

300304 AAATH000 1bar heating300304 AAATH000 1bar cooling310304 AAATH000 200 bar heating310304 AAATH000 200 bar cooling

Ther

mal

Con

duct

ivity

, W/m

K

Thermal Conductivity of PMMA

thermal conductivity of AAATH001 PMMA bead polymer on heating and cooling from 50C to 250C at atmospheric

pressure

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0 50 100 150 200 250 300

Temperature, C

310304 AAATH001 200bar heating310304 AAATH001 200bar cooling010404 AAATH001 1bar heating010404 AAATH001 1bar cooling

Ther

mal

Con

duct

ivity

, W/m

K

Thermal Conductivity of Rubber/PMMA Compound

thermal conductivity of AAATH002 rubber/PMMA granular compound on heating and cooling from 50C to 250C at

atmospheric pressure

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0 50 100 150 200 250 300

Temperature, C

010404 AAATH002 1bar heating010404 AAATH002 1bar cooling300404 AAATH002 200bar heating300404 AAATH002 200bar cooling

Ther

mal

Con

duct

ivity

, W/m

K

Summary of Thermal Conductivity Study on Rubber, PMMA and Rubber/PMMA Compound

Thermal conductivity measurements on powders, beads and granules are possible at range of temperatures and pressuresThermal conductivity measurements at atmospheric pressure depend on compaction of sample best results achieved with powder sampleThermal conductivity measurements of rubber samples can be made in the pre-crosslinked powder form (atmospheric pressure) and after crosslinking (200 bar)

Effect of Pressure on PP Thermal Conductivity

Thermal conductivity of polypropylene (AAATK004) on cooling from 250C to 50C at pressures of 200, 800 and 1200 bar

0.15

0.17

0.19

0.21

0.23

0.25

0.27

0.29

0.31

0.33

0.35

0 50 100 150 200 250 300Temperature,C

200 bar800 bar1200 bar

Ther

mal

Con

duct

ivity

, W/m

K

Effect of Pressure on PE Thermal Conductivity

Thermal conductivity of polyethylene (AAATK005) on cooling from 250C to 50C at pressures of 200, 800 and 1200 bar

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0 50 100 150 200 250 300

Temperature,C


Ther

mal

con

duct

ivity

, W/m

K

Effect of Pressure on PC Thermal Conductivity

Thermal conductivity of polycarbonate (AAATK001) on cooling from 200C to 50C at pressures of 200 and 800 bar

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0 50 100 150 200 250Temperature,C

200 bar800 bar

Ther

mal

Con

duct

ivity

, W/m

K

Effect of Pressure on PS Thermal Conductivity

Thermal conductivity of polystyrene (AAATK002) on cooling from 250C to 50C at pressures of 200, 800 and 1200 bar

0.15

0.17

0.19

0.21

0.23

0.25

0.27

0.29

0.31

0.33

0.35

0 50 100 150 200 250 300Temperature,C


Ther

mal

con

duct

ivity

, W/m

K

Summary of Pressure Effects on Thermal Conductivity of Polymers

Increase in thermal conductivity with increase in pressure across temperature range for all crystalline and amorphous polymers

Increase in crystallisation temperature with increase in pressure for crystalline polymers (PP and PE)

Decrease in thermal conductivity with cooling for amorphous polymers (PS and PC) across temperature range

Step increase in thermal conductivity with cooling for crystalline polymers (PP and PE) across temperature range

INDUSTRIAL TRIALSCorus & Zotefoams

Industrial Demonstrations

Aim is to demonstrate practical benefits of heat transfer measurements and modelling

Corus Thermal conductivity of plastisol coated steel before and

after solidification

Zotefoams Heat transfer during cooling of polyolefin foam

Corus

Use DSC method to measure thermal conductivity of bilayer Plastisol/steel

Measure before and after solidification

Data useful in predicting optimum line speeds

Earlier work had shown that the polymer layer was significant in terms of heat transfer

DSC method for thermal conductivity

Indium or eutecticDSC pan

Mulitlayer sample

Heat Transfer for sapphire

45

50

55

60

65

145 150 155 160 165 170 175Temperature (C)

Hea

t Flo

w (m

W)

(1988)) al et (Khannahh

mmKK

i

x

i

xix

2

=

DSC method for thermal conductivity

Zotefoams

Model heat transferMeasure (T, heat flux) over timeModel/measure shrinkageCalculate internal stressesUse bending theory to predict curvature

Zotefoams

hplate

hfoam

hgap

Air Flow

Key

Foam

Steel or aluminium plate

L

hplate

width = W

uamb m&

Stress relaxation of a two layer section after cutting

Layer 1

Layer 2

Layer 2

Layer 1

Layer 1

Layer 2

Cut foam layers fromfoam sheets

Release of stressesat the free surfaces

Onset of bending

Lset

Lset

Ltop

cut

cut

Lbottom

Ltop

Lbottom

hstrip

Thermal Conductivity StandardsISO TC61 SC5 WG8 Thermal Properties

Thermal conductivity and diffusivity: General Principles - New Work Item Proposal (NWIP) prepared

Hot Wire Techniques:Hot Wire (S. HEYEZ, Belgium) (ISO 8894)Line Source (H. LOBO, USA) (D 5930 ASTM)Hot Disk (S. GUSTAFSSON, Sweden) - NWIP prepared

Wave and Pulse methods:Temperature Wave Analysis (J. MORIKAWA, Japan) - NWIP preparedLaser Flash (B. HAY, France) (ISO 18755)

Steady State methods:Guarded Hot Plate (G. SIMS, UK) (ISO 8302) cross referencedGuarded Heat Flux (G. SIMS, UK) (ISO 8301/E 1530 ASTM) cross referencedTemperature Modulated DSC (in DSC ISO 11357 series)

http://www.npl.co.uk/npl/cmmt/polyproc/Polymer Processing Website

http://www.npl.co.uk/npl/cmmt/polyproc/

http://www.npl.co.uk/npl/cmmt/polyproc/

The next 6 monthsCommission and commence trials on heat transfer coefficient equipment

Continue to extend thermal conductivity measurement procedures to new types of material thermosets, rubbers, powders, nano-materials, glass

filled scientific paper

Industrial demonstrations (Corus / Zotefoams) to complete/continue

Deliverable extensions

Heat transfer coefficient apparatus M2/d2 Delivery of equipment: Jan 05 M3/d1 & d2 Test procedure and commissioning: March 05

Thermal conductivity measurement M6/d3 Scientific paper: November 04

Summary Heat Transfer

Heat transfer coefficient apparatus designed and now being manufactured Assisted by modelling studies Effect of uncertainties investigated (report available)

Melt thermal conductivity Nano-fillers Powders/granules Effect of uncertainties investigated (report available)

Standards active

New website - IAG members facilityhttp://www.npl.co.uk/npl/cmmt/polyproc

http://www.npl.co.uk/npl/cmmt/polyproc

Heat Transfer in Polymers - summaryAim of the projectEureka Project: AIMTECHTasks in the DTI ProjectHeat Transfer CoefficientHeat Transfer Coefficient (heat transfer across an interface)Modelling of key featuresEffect of a thermocoupleSimulation of Heat Transfer with Fibre Optic (left) & Thermocouple (right)Comparison of thermocouple & fibre opticAir GapHeat Transfer Coefficient Summary Thermal ConductivityUncertainty Budget For NPL Line-Source Thermal Conductivity Probe (Atmospheric Pressure)Thermal Conductivity of PDMS (Atmospheric Pressure)Thermal Conductivity of HDPE (Atmospheric Pressure)Thermal Conductivity of HDPE (Atmospheric and 1000 bar Pressures)Thermal Conductivity Uncertainty Analysis SummaryMoldflow model of HDPE Pipe T-pieceChanges In Cooling Times With Increasing Thermal Conductivity Values For T- Piece From Moldflow SimulationThermal ConductivityNano-materials Thermal Conductivity (200 bar)Nano-materials Thermal Conductivity (800 bar)Nano-materials Thermal Conductivity (1200 bar)Summary of Thermal Conductivity Study of Nano-clay Filled PolypropyleneThermal Conductivity of RubberThermal Conductivity of PMMAThermal Conductivity of Rubber/PMMA CompoundSummary of Thermal Conductivity Study on Rubber, PMMA and Rubber/PMMA CompoundEffect of Pressure on PP Thermal ConductivityEffect of Pressure on PE Thermal ConductivityEffect of Pressure on PC Thermal ConductivityEffect of Pressure on PS Thermal ConductivitySummary of Pressure Effects on Thermal Conductivity of PolymersIndustrial DemonstrationsCorusDSC method for thermal conductivityZotefoamsZotefoamsStress relaxation of a two layer section after cuttingThermal Conductivity StandardsPolymer Processing Websitehttp://www.npl.co.uk/npl/cmmt/polyproc/http://www.npl.co.uk/npl/cmmt/polyproc/http://www.npl.co.uk/npl/cmmt/polyproc/http://www.npl.co.uk/npl/cmmt/polyproc/The next 6 monthsDeliverable extensionsSummary Heat Transfer

heat transfer in polymers - national physical...

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