Diss. ETHNo. 13978

Ultra-High

Molecular

Processing Polyethylene

and

Weight Polymers

Properties

of

Poly(tetrafluoroethylene)

and

A dissertation submitted to the

EIDGENÖSSISCHE TECHNISCHE HOCHSCHULE ZÜRICH

for the

degree

of

Doctor of Technical Sciences

presented by Jeroen Franklin

M.Sc. Chemical

Eindhoven

Visjager

Engineering

University

of Technology

born December 17, 1970 citizen of the Netherlands

accepted

on

the recommendation of

Prof.Dr. P. Prof.Dr. N.D. Dr. T.A.

Smith, examiner

Spencer, co-examiner

Tervoort, co-examiner

2001

"Gutta cavat

lapidem,

non

vi sed saepe cadendo.

"

Publius Ovidius Naso, Ex Ponto

To my

parents

Table of Contents

1.

Introduction

1.1

General Introduction

1.2

Background

1.3

Objectives

1.4

References

2.

Processing and Rheology of Polyethylene

2.1

Introduction

2.2

Theory

2.3

Experimental

2.3.1

Materials

2.3.2

Compounding

2.3.3

Characterization

2.4

Results and Discussion

2.5

Conclusions

2.6

References

3.

Abrasive Wear of

3.1

Introduction

3.2

Experimental

3.2.1

Materials

and

Survey of the Thesis

Polyethylenes

-

vin

-

3.2.2

Compounding

34

3.2.3

Characterization

36

3.2.4

Abrasive Wear Methods

37

3.3

Result and Discussion

41

3.4

Conclusions

56

3.5

References

57

4.

Phase Behavior of

Binary Systems

of Perfluorinated

Alkanes

59

4.1

Introduction

59

4.2

Experimental

60

4.2.1

Materials

60

4.2.2

Characterization

60

4.3

Theory

61

4.4

Results and Discussion

64

4.5

Conclusions

73

4.6

References

74

5.

Processing and Properties

5.1

Introduction

75

5.2

Experimental

80

5.2.1

Materials

80

5.2.2

Extrusion, Blending and Coumpounding

80

5.2.3

Characterization

82

of Poly(tetrafluoroethylene)

75

-

IX

-

5.3

Results and Discussion

5.4

Conclusion

5.5

Appendix:

5.6

References

109

6.

General Conclusions and Outlook

113

Tuminello

84

108

Storage Modulus Transform

108

Summary

121

Zusammenfassung

123

Acknowledgments

127

Curriculum vitae

129

Publications

131

1. Introduction

1.1 General Introduction

Polymers generally connected

defined

are

long

as

chain molecules that

moieties, and that interact through relatively weak intermolecular forces.

These structural features

are

responsible

for many of the

metals and ceramics. In

organic species,

(molecular weight), characteristics.

general,

However, with increasing

Ultra-high

mobility

of the

these materials from the molten state becomes

molecular

weight (UHMW) polymers,

macromolecules with molecular but

superior properties,

weights

virtually

are

weight

chain

length

also

length,

their

that exceed 10

intractable when

their

longer

mechanical

(melt)viscosity

chain

exceedingly

commonly

term

a

polymeric

low molecular

increasing polymer

at

chain

increases due to sterical hindrance and reduced

processing

as

physical properties improve, notably

many

of

unique properties

materials and set them apart from traditional materials such

and

comprise covalently

molecules,

cumbersome.

used to refer to

g/mol, therefore, typically

applying

conventional

have

processing

means.

A

variety

1.1

an

not

a

well

of UHMW

overview is

given

complete list, as

polymers

and that

polymers UHMW

some

is their

before,

polymers

products

cannot

such

of UHMW

molded and sintered metal

industry.

polymers.

of the molecular

most

'intractability'.

processing techniques

and

known UHMW

weight

40-50 years. In Table

It should be noted that this is

ranges include commercial

examples [1-3].

UHMW

as

polymers typically

resistance, chemical resistance, fracture toughness and frictional

behavior. As noted

or

some

synthesized for more than

various research materials and patent

excel in abrasion

most

of

have been

unfortunately,

Because of the

major

a

drawback of this class of

extremely high

be transformed into useful articles as

injection molding,

polymers traditionally

pre-forms,

with the

Due to the attractive

use

of

blow are

molding

made

molecular

by or

extrusion.

by machining

of UHMW

time-consuming processing methods, increasing

efforts

polymers are

these

conventional melt-

techniques commonly

properties

weight,

being

of

Therefore,

compression

used in the wood and the

expensive

directed towards

-2-

Table 1.1 Various UHMW polymers.

Molecular

Polymer

Weight ( 106 g/mol)

polyethylene

1-6

polypropylene (isotactic)

1-3

polyisobutylene

4-6

poly (aery lamide)

1-21

polyisoprene

1-5

poly(ethyleneoxide)

1-5

poly(tetrafluoroethylene)

5-100

poly(methylmethacrylate)

1-8

polystyrene (atactic)

1-50

poly(vinylalcohol)

1.5

poly(acrylicacid)

4-20

poly(vinylacetate)

3.2

nylon-6

1-3.5

nylon-4

1

poly(acrylonitrile)

1-2

poly(l-lactide)

1.5

the

The number

'intractability'. research articles As

of different

development

illustrated

on

by

dramatically increasing

data,

polymers

is

routes

and

applications)

in the

recent

is

both

polymers

often

article. This

particular

processing, represented for UHMW-PE

patents and in

Figure

1.1.

indeed have

possible processing

routes

1.2. The first

approach (1) depicts

the above-

in

Figure

raw

diffusion and

material

sintering

times

for

Due to the

[e.g. 4-7].

result, which lead

and uneconomical processes. Moreover, much of the

most

noted

An overview of various

presented

morphology

notably

UHMW

years,

above

attention, especially ultra-high molecular weight

extremely high polymer viscosities, long time-consuming

the

graphically displayed

mentioned, compression molding and sintering of the

to

circumvent

to

resulting publications (including

considerable

polyethylene (UHMW-PE). UHMW

of

processing these

processing

original powder

remains, which will adversely effect the properties of the endissue will be addressed in in route 2, has been

[8, 9].

In this process,

more

detail in

extensively

Chapter

3. Solution

described in the

typically, relatively

low

literature,

viscosity (when

-3

500

-

r

]

# Total UHMW polymers

1 # Total UHMW-PE 400

|-

V777À # Patents UHMW polymers

^H #

CO

Patents UHMW-PE

Ö O

|

300

I-

1 ^ 200|tu

X

100

-

'67-'71

'72-'76

'77-'81

'82-'86

'87-'91

'97-'011

'92-'96

Year

Figure

1.1 Total number

periods offive years for

UHMW polymers in

area's indicate the number

compared xylene

to

are

solvent is network

the

melt)

The

the dimensions of the used to manufacture

technology

is the

shaped by

objects

the UHMW

processing

route

that

of reactive a

polymer

using epoxies

thermal

produced and, therefore,

high-strength

solvents,

degradation,

patterned

solvent for the

rather than

poorly

a

reduction in

the PPE mentioned in this

the result demonstrates the

potential

of this

mainly

particular

removed, but polymerized after

investigated

tractable

polymer

was

not

a

very similar

poly(2,6-dimethy 1-1,4was

employed

to

blend below the onset of

viscosity sought study

extraction limits

this route is

In the authors' case, the solvent

of the

or

the

entanglement

in route 3. In this

solution. Venderbosch et al. as

Subsequently,

or

fibers and porous films. A related

depicted

as

high glass-transition temperature

Clearly, although weight,

and

be

by evaporation

monomer, which is not

phenylene ether) (PPE) [10-12]. decrease the

can

methods.

ductile material due to their low

of solvent removal

necessity

process, the solvent used is

shaping

UHMW-PE. The

in, for example, decaline

processing

common

highly

a

high-modulus

use

general and for

in time

ofpatents (values pro rata).

removed, which yields

density [9].

publications)

and research

0.5-10 wt% UHMW-PE solutions

and

prepared

of publications (patents

for UHMW

of

ultra-high

interesting processing

polymers. molecular

route.

Figure

in solvent

dissolution

compression moulding

of ductile

casting

molding

extrusion, compression-

molding

compression

or

spinning, casting,

or

solution-spinning,

to process 'intractable' UHMW polymers.

weight (this work)

approaches

distribution

of molecular

optimization

(virgin) powder

synthesis

1.2 Various

5.

4.

in monomer

3. dissolution

2.

1.

t injection molding

llll

or

or

polymerization

of solvent

evaporation

t

of

melting

monomer

extraction

sintering

-5-

Another

possible

powders

of certain

feature enables free of

(4),

route

first disclosed

virgin polymers

that exhibit

flow below the

plastic

boundaries

particle grain

in

is

with respect to

is that lower molecular that

not

are

properties and in

1.2

if not

A last

fact, is the subject of this thesis.

optimized

low

entanglement density.

processing

route

and

processing

is

and have

a

polymer

The latter

products virtually materials with

depicted

Figure

in

weight

used

are

a

1.2-5

distribution

the various

properties. Among

as

options

'solvents'

limited deterious effect

of the final material. This will be discussed in

Chapters 2,

dense

subsequently melted,

versions of the UHMW

weight

[13], involves compacting

In this route, the molecular

"processability"

extracted after

a

al.

et

melting point, yielding

and,

remarkably high drawability [14-16]. which,

by Chanzy

on

the

detail in the next section

more

3 and 5 of this thesis.

Background

Polyethylene

In this thesis UHMW-PE will be discussed

combines many

unique properties

any known other even

at

stress-crack resistance and has been

approved by

pure water and food

its way into many the food

a

a

as an

the first material of interest. This abrasion resistance that is

highest impact toughness

good

corrosion

resistance;

of all

an

low coefficient of surface friction.

polymer

higher

than of

polymer materials,

excellent environmental

Furthermore,

UHMW-PE

the USDA, FDA, and National Bureau of Standards sanctions for

handling.

It

is, therefore,

not

surprising

demanding applications, ranging

industry

particularly

the

thermoplastic;

cryogenic temperatures;

such

as

to

medical

and

from liners for

sport products [17].

of interest is the

use

discussed in the

previous section,

that UHMW-PE has found

of UHMW-PE in medical

One

hoppers

and

application

implants

such

as

pipes

which

artificial

in

is

hip

joints.

As

already

developed to solution

overcome

processing

the

a

variety

purported intractability

of

of this

polymer.

of UHMW-PE, in which the molecular

lower than the molecular

weight

between chain

processing

routes

A notable

weight (Mw)

entanglements (Me),

have been

example

is

of the solvents is

and is

employed

to

-6-

fibers

produce high-performance

Products manufactured in this

SpectraR (Allied, USA) Fig. 1.2-5, is

UHMW-PE

and

can

that

standard

permits

objective

melt-processing,

is to reduce the while

deployed,

such

and

DyneemaR (DSM,

The

melt-mixing,

large

to

such bi-

produce

As sketched in

of

aMw

of the mixture to

that

value

a

fraction of the mechanical

different

general,

blending techniques

followed

powder blending

coarse

solvent-blending [18-22],

a

Netherlands),

weight grades

viscosity

retaining

gel-spinning.

as

TekmilonR (Mitsui Petrochemicals, Japan).

associated with UHMW-PE. In

molding

process often referred to

include

manner

properties

as

a

be blended with lower molecular

the

higher thanMe. Here,

according to

by compression

multi-modal systems. In

or

lieu, these systems could, of course, also be directly produced during polymerization a

of

variety

has been

single

opted

or

as a

multi-stage

processes

[23-25].

In this

are

work,

common

via

melt-mixing

processing technique.

Poly(tetrafluoroethylene)

The second

weight

that will be addressed in detail in this thesis is

polymer

PTFE

(UHMW-PTFE). this

monomer

yields

molecular

weight

polymer,

the

of

more

than 10

engineering material, exhibiting

stability

over a

fully

fluorinated

Pa.s at 380 °C

excellent insulation

handling aggressive by

known

attractive forces have the

involving

at

an

a

acids at elevated temperatures

(481 kJ/mol),

in combination with

(~3 kJ/mol).

Most

solutions

are

atmospheric

systems with solvents

one

low coefficient of

unfortunately, however,

restrained due to the lack of

pressure at

[29], which

their vapor pressures

such

as

[27]. Hence, for

example can

be

units, which is the highest

these very characteristics

manufacturing

common

thermodynamics were

high-temperature

of the lowest ranked interchain

that molecular characterization and

repercussion

useful

extremely

[28]. This outstanding stability

its C-F bond energy of its constituent repeat

a

concomitant ultra¬

all solvents

virtually

demanding high-temperature applications

Previous studies have addressed the solution

systems

a

PTFE is

properties,

with

polyethylene,

wide temperature range and is notorious for its excellent

PTFE is often used in

currently

of and

g/mol

[26].

molecular

tetrafluoroethylene (TFE)

equivalent

and extreme inertness to chemical attack and

accounted for

of

polymerization

that is estimated to exceed 10,000,000

high melt-viscosity

friction

Normal

ultra-high

extended

of

by

(autogenous).

industrial

processes

solvents.

PTFE-perfluorocarbon

Tuminello et al. In

[30]

addition, Chu

et

to

al.

-7-

[31, 32] elegantly characterized at

PTFE in

temperatures above 300 °C. However, due

application

of the solvents used in these process has been

manufacturing

of TFE and

oligomers to poor

thermal

investigations,

developed

as

of

chlorotrifluoroethylene

stability, price

practical

commercial solution-based

no

The current

today.

and

general

route to

generate melt-processabilty of TFE based polymers consists of the introduction of in the PTFE macromolecular chain and

comonomers

[28, 33, 34]. Like PTFE, these copolymers exhibit and

outstanding properties (e.g. toughness resistance

penalty

thermal stress

against

is

in terms of

paid

solution to the 'solvents' with

comprised

molecular

above for UHMW-PE. This

Chapter

1.3

particularly

Objectives

same

and

before, time

thesis is to

are

higher

than

compared

stability

is the

identical to that

successful concept will be

PTFE,

a

and costs. A novel

homopolymers

Me,

to

and

presented

use

of

proposed

in detail in

of the Thesis

Survey

UHMW

polymers

limited in

optimize

processability

polymers,

Chapters

2 and 3

i.e.

are

the molecular

2

comprising

polyethylene

wide spectrum of excellent

due to their

weight

'intractability'.

and

properties,

The

objective

but at of this

distribution with respect to convenient for two

commercially important

poly(tetrafluoroethylene).

concerned with UHMW-PE. The central theme is to elucidate the

properties

describes of

a

(mechanical) properties

detailed relation between molecular certain mechanical

offer

applications

and maximal

UHMW

Chapter

of PTFE

features

5.

As stated

the

when

weight

combination of

superb

flexibility, blow-molding

thermal and chemical

that is

weight

and

unique

cracking). Nevertheless,

melt-processability problem a

a

the molecular

reducing

the

ultra-high

analogs. Furthermore,

a

behavior and molecular

on

weight

the other side

preparation

molecular

quantitative

weight

distribution and

and

processing

on one

side, and

(cf. Figure 1.3).

rheological

weight polyethylene correlation will be

characterization

of

blends

and lower molecular

weight

presented

distribution of these blends.

between

rheological

-8-

molecular

processing

weight

distribution

w(M)

**

**

(rheology)

Figure

Interrelation

1.3

properties

(abrasive wear)

between

processing,

properties

and

molecular

weight

molecular

weight

distribution.

Chapter

3

distribution

elucidates the on

and

samples wear

Chapter

wear

of UHMW-PE.

applications that

abrasive

of

a

low

heretofore

unknown

influence

behavior, which plays

Employing

polydispersity

a

variety

of

offer the best

a

of the

role in many

particularly important

analytical techniques compromise

it is established

between

processability

resistance.

4 deals with

binary systems phenomena properties

are

of

perfluorinated investigated.

of

key

a

basic

study

homologous factors in

phase segregation

extended-chain

alkanes.

determining

non-monodisperse alkanes

of solid-solution formation and

for

The

latter

the solid-state structure and mechanical

polymers.

(model compounds

perfluorinated

in

The

phase

behavior

poly(tetrafluoroethylene))

mixtures was,

of

therefore,

-9-

In

Chapter 5,

the identification of a window of viscosities of poly(tetrafluoroethylene)s is

disclosed that and

of this

unique polymer

into

mechanically

coherent

tough objects.

Finally,

Note:

in

Chapter

6

some

In view of the

polymers, expressed as

permit melt-processing

adopted

we

in

kg/mol

or

general

conclusions and outlook

parlance "Ultra-High

common

in this thesis the historical

g/mol,

opposed

as

to

the

presented.

Molecular

terminology correct

more

the International Union of Pure and

suggested by

are

Weight (UHMW)" "molecular

designation

weight",

"molar mass"

Applied Chemistry (IUPAC).

1.4 References

1

Search, are

© American Chemical

Society,

key-word dependent and, therefore,

2000

(it

not to

be considered

2.

Polysciences, Inc., Polymer/Monomer Catalog

3.

Smith, L.E., Verdier, PH., 2nd New

in

has to be noted that these searches as

absolute

1998-2000.

Encyclopedia of Polymer

Science and

Engineering,

ed., Mark, H.F., Bikales, N.M., Overberger, CG, Menges, G, Eds., Wiley: York,

Vol.

12,

p. 690

(1988).

4.

Zachanades, A.E., Watts, P.C., Porter, R.S., Polym. Eng Sei., 20,

5.

Zachariades, A.E., Kanamoto, T., Polym. Eng. Sei., 26,

6.

Uehara,

H.,

Nakae,

Macromolecules, 32, 7.

numbers).

Nakae,

M.,

2761

Uehara,

Macromolecules, 33,

M.,

(1980).

(1986).

T.,

Zachariades,

A.E.,

Porter,

R.S.,

T.,

Zachariades,

A.E.,

Porter,

R.S.,

505

(1980).

(1999).

H.,

2632

Kanamoto,

658

555

Kanamoto,

(2000).

8.

Smith, P., Lemstra, P.J.,

9.

Smith, P., Lemstra, PL, Booij, H.C.,

J. Mater.

Sei., 15, J.

Polym.

Sei.

Polym. Phys. Ed., 19,

877

(1981). 10.

Meijer, HE.H, Venderbosch, R.W, Goossens, LPG, Lemstra, PL, High Perform. Polym., 8,

11.

133

(1996).

Venderbosch, R.W, Meyer, H.E.H., Lemstra, PL, Polymer, 35,

4349

(1994).

-

12.

10-

Venderbosch, R.W, Nehssen, J.G.L., Meyer, H.E.H., Lemstra, PL,

Makromol.

Chem., Macromol. Symp., 75, 73 (1993). 13.

Chanzy, H.D., Rotzinger, B., Smith, P.,

14.

Rotzinger, B.P, Chanzy, H.D., Smith, P., Polymer, 30,

15.

Endo, R., Kanamoto, T., Porter, R.S.,

(1988).

US Patent 4,769,433

J.

Sei.

Polym.

1814

(1989).

Polym. Phys.Ed., 36,

1419

(1998). 16.

Endo, R., Jounai, K., Uehara, H., Kanamoto, T., Porter, RS.,

Phys.Ed, 36, 17.

Polym.

Sei.

Polym.

(1998).

2551

Coughlan, J.J., Hug, 2nd

J.

D.P in

Encyclopedia of Polymer

Science and

Engineering,

ed., Mark, H.F., Bikales, N.M., Overberger, CG, Menges, G, Eds., Wiley: York,

New

Vol.

6,

p. 490

(1986).

18.

Bhateja, S.K, Andrews, E.H., Polym. Eng Sei., 23,

19.

Dumoulin, M.M., Utracki, L.A., Lara, L, Polym. Eng Sei., 24,

20.

Vadhar, P., Kyu, T.,

21.

Vadhar, P., Kyu, T., Polym. Eng Sei., 27,

22.

Sawatan, C, Matsuo, M., Polymer, 30,

23.

Winter, A., Dolle, V, Spaleck, W, US Patent 5,350,817 (1994).

24.

Ahhevainen, A., Sarantila, K., Andtsjö, H., Takaharhu, L, Palmroos, A.,

J.

Appl. Polym. Sei., 32,

1603

(1983). 117

(1984).

(1986).

5575

202

888

(1987). (1989).

US Patent

5,326,835 (1994). US Patent 5,543,376

25.

Bergmeister, II,

26.

Hintzer, K., Löhr, York,

27.

p.

G. in Modem

(1996).

Fluoropolymers, Scheirs, L, Ed., Wiley:

New

240(1997).

Sperati, CA., Starkweather, H.W., Jr.,

Hochpolym.-Forsch., 2,

Fortschr.

465

(1961). 28.

Scheirs, J., Ed.

29.

Smith, P., Gardner, K.H., Macromolecules, 18,

30.

Tuminello, W.H., Dee, G.T., Macromolecules, 27,

31.

Chu, B., Wu, C, Zuo, J., Macromolecules, 20,

32.

Chu, B., Wu, C, Buck, W., Macromolecules, 21,

33.

Gangal,

S.V. in

inModern

Fluoropolymers, Wiley:

New

1222

Encyclopedia ofPolymer Science

(1985).

669

700

York, p.15 (1997).

(1994).

(1987).

397

(1988).

and

Engineering, 2nd ed., Mark,

H.F, Bikales, N.M., Overberger, CG, Menges, G, Eds., Wiley: New York, Vol.

16,

p.

577(1989).

-11

34.

Banks, R.E., Willoughby,

B.G. in The

-

Encyclopedia ofAdvanced Materials, Bloor,

D., Brook, R.J., Flemings, M.C, Mahajan, S., Eds., Pergamon: Oxford, 1994, Vol.2,

p.

862(1994).

2.

Processing and Rheology of Polyethylene Blends

2.1 Introduction

Polyethylene (PE)

has become

thermoplastic polymers

with

architecture and molecular

bags

and

bullet

containers)

proof

molecular

Chapter 1)

vests

weight as a

to

and

A

abundant

shields)

version of

and medical

that

common

such

corrosion

widely investigated

(depending

daily

as

life

molecular

on

objects (e.g. garbage

ballistic

items

protection

Interest in the

implants [1-5].

polyethylene (UHMW-PE)

result of its many

used and

(e.g.

ultra-high

has grown in recent years

outstanding properties,

i.e.

high

abrasion

(see

resistance,

resistance, environmental stress-crack resistance, and

low coefficient of surface friction.

major

this

drawback of UHMW-PE,

polymer

with

extremely high

common

melt

linear

existence of

melt-processable by properties

weight

and its

"plastics" industry,

objective

an

molecular

optimum

common

means

of this

processing

in

which is due to its

chapter,

to

investigate

weight

particular study distribution

is to

(MWD)

and to exhibit certain desirable

explore

low-molecular

(mechanical)

broad spectrum of MWD's, two different

weight high-density polyethylene (HDPE) grades

all with known MWD,

between MWD and

were

rheological

formalism which enables

function of shear rate from

a

a

one

provide

a

relatively

UMMW-PE

blended in their molten state. In this work the relation

behavior of linear

polyethylenes

quantitative prediction

given

and

the

for PE to be

that resemble those of the "intractable" UHMW-PE. In order to a

the

distribution, and rheological properties of

The ultimate purpose of this

series of materials that represent

grade,

used in the

It is the

viscosity [2].

polyethylenes.

possible

however, is the difficulty encountered

techniques

relation between molecular

a

applications

range from

weight)

commonly

high-performance products

high impact thoughness, a

of the most

one

MWD

of the

[see Figure 1.3].

will be evaluated

complex viscosity

using as

a

14-

-

2.2

Theory

It has

been realized that the relation between

long

distribution is of paramount and

properties

MWD

characterization of

high

molecular

soluble in use

importance. of

are

and

molecular

weights

dictate to

weights between

the

particularly

are

a

very

large

rheological

characteristics. It

properties.

a

an

is, therefore,

case

not at

all

the as

soluble

are

for the

higher

molecular

approximative

correlation

be

extremely useful,

chemistry

the

direct

such

as

the

synthesis

of

relation between

quantitative

design polymer grades significant

with

given

effort has been

of the relation between MWD and

Menefee

rheological

averaging

of

viscosities, T|0, by weight fractions. However, this model is applicable only

in

for which the molecular

poly disperse

linear

[6], initially considers the trivial

weight dependence

polymers,

of the

linear, but follows the commonly accepted relationship T|0

systems. Here, A is definition of the

a

constant

weight-average

and B is

normally

molecular

T|o in melts of linear polymers then follows

is of the

(nearly)

melts, this dependence is =

AMW

for

polydisperse

found to be close to 3.4. From the

weight, Mw as:

i.e. linear

viscosity

first power, i.e. dilute solutions. For concentrated solutions and not

or

higher

new

that

and ultra¬

restricting

polymers

these

enables

surprising

not

simple model, proposed by

rule for the viscosities of

zero-shear

hand,

thus

techniques

would

and MWD. A

essential tool to

understanding

even an

molecular

Two of the most successful relations will be reviewed below.

The first and most

the

would be

better

On the other

weight

weight

and the MWD, such

Even if the

measurements

catalysts, nowadays

with controlled molecular

rheology,

mixing

processability. Hence,

polymers.

MWD and

weight

unfortunately, especially

rheological

of metallocene

directed towards

only slightly

are

and resolution of the above

poor;

extent

and

MWD

for UHMW

development polymers

sensitivity

light scattering.

the

polymers

(e.g. poly(tetrafluoroethylene) (PTFE)),

gel permeation chromatography the

for

of 'intractable'

case

of conventional methods to determine the molecular

(e.g. UHMW-PE),

value

practical

The former materials often

weight polymers. solvents

in the

and molecular

hand, relations between rheological

one

considerable

polymers, especially

common

On the

rheology

=

Vw,^ '

,

the

mixing

rule for

15-

-

.1/3 4

T|(Y)

nJ

imJ

J

J

ninJ

J

J

immJ

J2c

2.1 Schematic

Figure

viscosity (r\)

versus

plot of

shear

the

iiiiJ

immJ

to

J_

J_ 3.4

2>^

of the

rule

for

until

a

that

(1)

the

(EQ2.1)

monodisperse

critical shear rate yc above which the

law coefficient n; and

approach

is shown in

(2)

the

Figure

mixing

rule is

fraction i. Malkin and Teishev

of

the

steady-state

phenomenological relation, predict

the

rheological

exactly

the

quantities

critical shear rate yc.

what

the

monodisperse

viscosity

follows

independent

rheological

viscosity

might

behavior from

one

to

a

power-law with

of Mw and yc.

a

would like to

be called

a

a

power-

Graphically,

particularly

However,

this

useful

it

is

a

purely

and not well suited to

since it needs

i.e. the

shear

[8, 9] since it involves only

disadvantage,

given MWD, predict,

data

curve.

steady-state

fractions is constant

2.1. The model of Malkin and Teishev is

for the determination of the MWD from differentiation

of

viscosity

shear

[7J.

0/

[7] generalized this mixing rule for the zero-shear viscosity

viscosity, T|(y), assuming

steady-state

the

Malkin and Teishev

3.4

viscosity

34

]

J

generalized mixing

T| o

.1/3 4

+W2T[ (y)

y

rate(y) according

where T|0/ is the zero-shear

[WjTl (y)

=

power-law

as

input parameters

coefficient

n

and the

-

The second model of interest is based Cloizeaux

[10-12], which has

viscoelastic response of

shear relaxation modulus is

F(M,t)

is the

used

for

[15], with

for

success

in

model of des

modeling

an

integral

transform of the

of the linear the double-

to

continuous distribution of molecular

a

f

=

weights,

weight

the

distribution

weight

w(M)jF(M,t)dM

relaxation

monodisperse

F(M,t) a

double-reptation

weights, w(M):

related to the molecular

expressions

with considerable

essentially

pS Here

the so-called

polydisperse systems [13, 14]. According

reptation model, generalized

function of molecular

met

on

16-

between

have been

function, and G g is the plateau modulus,

entanglements, Me, by G0

proposed.

relaxation time that

(EQ2.2)

In what

depends

on

follows,

an

=

pRT/Me.

exponential

the molecular

weight

via

Several

function a

was

power-law

with the familiar exponent 3.4:

JF(M, t)

-/ =

exp

with

|_2t(M).

Once the shear relaxation modulus is

x(M)

=

(EQ 23)

KM3A

known, other viscoelastic functions

through

the well-known transformation rules from

example,

the zero-shear

viscosity, T|0, simply

is the

linear of

integral

can

be derived

viscoelasticity [16].

For

G(t):

oo

Tin

Another

quantity

of interest is the

f

=

(EQ2.4)

G{t)dt

complex viscosity T|*(co),

which is related to

G(t) by:

oo

r|*(co)

Although the double-reptation used to

predict

According

to

the

=

f G(0exp[-7O>f]df

model is

steady-state

a

shear

linear viscoelastic

viscosity using

this, the steady-state shear viscosity

dynamic viscosity (absolute

value of the

T|(y)

=

(EQ2.5)

Jo

|t|*(cû)|

at

model, it nevertheless

the Cox-Merz rule

shear rate y,

complex viscosity [19])

at

y

=

co

at

T|(y),

can

be

[17, 18].

is related to the

frequency

CO as:

(EQ 2.6)

-

In this way,

which is

Equations [2.2-6] of the most

one

considerable effort to

an

relate the MWD to the

important rheological the

use

characteristics to the MWD. MWD is

17-

ill-posed problem

double-reptation

steady-state

shear

viscosity T|(y),

characteristic. There has also been model to

Unfortunately, solving

of

which is far from trivial

relate

Equation

linear viscoelastic

2.2 for

an

unknown

[20], and is outside the

scope of

this work.

2.3

Experimental

2.3.1 Materials

Various

this work

2.3.2

of PE obtained from DSM

grades (see

Table

analyzed

and

employed

in

2.1).

were

prepared

with

twin-screw extruder

recycling

the temperature of which

addition, for

more

detailed

quantities (~5 kg)

of

(model ZSK-30M,

L/D

Ausbildungspowder

und

a

kg/hr]

[feeding

1

small scale

was

kept

product

=

40) co-rotating

was

were

in order to

window of 200-240 °C.

All

Barbara,

The material residence time

was

discharged.

and mechanical

prepared using

was

CH.

beads

a

studies, larger

Werner and Pfleiderer

In the

were

first step, UHMW-PE

'pre-blended' [total feeding

collected, pelletized and compounded again

produce homogeneously

increase the residence-time.

cc) laboratory,

twin-screw extruder located at the Kunststoff-

weight (HDPE)

different viscosities of the selected

volume: 4

DACA Instruments, Santa

at 180 °C.

Technologie-Zentrum, Aarau,

after which the material

kg/hr]

(total sample

rheological, processing

series of blends

and lower molecular

rate: 3-6

a

(MicroCompounder,

10 min at 120 rpm, after which the

In

were

Compounding

Various blends

CA),

(StamylanR),

compositions,

extruder-sections

mixed material. an

Depending

additional pump

were

kept

within

a

was

on

the

used to

temperature

b

a

80-20

60-40

50-50

95-5

90-10

80-20

60-40

50-50

Blend

Blend

Blend

Blend

Blend

Blend

Blend

Blend

Blend

+

+

+

+

I

I

I

I

+

+

+

+

II

II

II

II

III

III

III

III

III

n.a.

=

not

applicable.

Values derived from the

Values calculated

+

II

III

III

III

from GPC data.

-

12

9

-

-

-

34

26

-

-

a

-

978

522

-

-

-

967

530

-

-

2,063

230

91

(kg/mol)

M

-

6,060

4,175

-

-

-

5,571

4,669

-

-

5,135

1,726

302

-

81.6

58.0

-

-

-

27.6

20.4

-

-

7.2

n

*

14

12

9

8

8

40

34

26

24

23

n.a.

n.a.

n.a.

(kg/mol)

Mb

interpolated

thereof.

32.9

4.3

w'

and blends

(kg/mol)

M/

polyethylene grades

distributions for the various blends, calculated from the

285

7

predicted molecular weight

directly

90-10

Blend

+

I

III

95-5

UH210, DSM

III

III

HD

II

-

HD

I

-

(kg/mol)

(-)

21

Ma

various

weight ratio

8621, DSM

grade

-

ene

weight characteristics of

7048, DSM

Polyethy]

Table 2.1: Molecular b

4,792

4,646

4,082

3,426

2,818

4,930

4,833

4,407

3,757

2,926

n.a.

n.a.

n.a.

(kg/mol)

Mzb

GPC data of the neat materials,

1,147

963

597

414

322

1,077

880

486

289

190

n.a.

n.a.

n.a.

(kg/mol)

M

81.9

80.3

66.3

51.8

40.3

26.9

25.9

18.7

12.0

8.2

n.a.

n.a.

n.a.

n

IMh w'

M

19-

-

2.3.3 Characterization

Rheology

The absolute values of the were

complex

determined from small

Rheometric Mechanical

relaxation

long

plate experiments

Spectrometer

estimated from

degradation

using

all tests

at

grades

experiments

180

cone-plate

and

were

(see Figure 2.2).

at

carried out with

a

frequencies

plate-plate (in cone-plate

the

and

case

plate-

The linear range

100 rad/s. In order to

carried out under

and their blends

°C for several

The differences between

found to be small

polymers,

800

standard

strain-sweep experiments

of the

10

rad/s

RMS

times) geometries.

were

shear

amplitude oscillatory

between 100 rad/s and 3.10" of very

viscosities of different PE

was

prevent oxidative

nitrogen atmosphere.

F :

A

plate-plate cone-plate

10°

o o

>

10D

o

cö

e

Q

104

10

10"'

10"

10"

10" œ

Figure

2.2

blend [PE

+

III) [weight

ratio

80-20] (see

10

(s" )

Comparison of the dynamic viscosity (I

101

Table

versus

frequency fcoj of a typical

2.1)] using cone-plate

geometries, illustrating the small difference between the

two

PE

and plate-plate

experimental set-ups.

-20-

Gel Permeation

Chromatography

Gel

High-Temperature Montell

Permeation

Polyolefins, Ferrara, Italy

,

with

solvent and mobile

carried out

was

at

Waters 150C ALC/GPC instrument with the

a

column type: TSK GMHXL-HT

following specifications: rate: 0.5 ml min"

Chromatography (HT-GPC)

phase

antioxidant:

(13 |im),

mobile

flow

phase

1,2,4-trichlorobenzene and 2,6-

detector: refractive index and column temperature: 135 °C. Standard

di-/-butyl-p-cresol,

Cal

polystyrene samples (Easy

Kit, Polymer Laboratories, UK)

calibration; the total elution duration

was

used

were

for

about 120 min.

2.4 Results and Discussion

The

logarithmic weight

grades

PE

I,

II and III

distributions

are

shown in

(W

O o on

.2

on

g O

1 c >>

Q

co(s" )

(s"1)

Y

(b) 10s

-

on

CO on

cö

p^

p^

io7t

on O O

on

10°

O

on

r

o

*****

8

on

io3

•s

'>

on

-

CO

ta +-»

h:

io4t

CO

I/PE

I/PE

I/PE

II/PE

II/PE

II/PE

Fraction, S.N.P.A.7'8

grade

80/20 PE

A

Y

grade

90/10 PE

H

grade

grade

80/20 PE

A

V

grade

grade

10/90 PE 2000/PE

90/10 PE

grade

20/80 PE 2000/PE

A

H

grade

30/70 PE 2000/PE

grade

+

40/60 PE 2000/PE

210, DSM)

(HD 7048, DSM)

(HD 8621, DSM)

II

2000,

PE

Polyscience6'7)

F

2) i Sample/j

o

weight, crystallinity,

#

in i Symbol1-1

Table 3.1: Molecular

^

-36-

Table 3.1

(continued):

i)

corresponding

2)

blends

3)

crystallinity 100

to denotation in

prepared according

to

Figures

procedure

calculated from the

%-crystalline

material

5)

average value from 3 measurements.

6)

estimated from the

7)

Mn andM^ according

8)

Nc

calculated

experimental

section of Chapter 2.

equations

assuming

a

with 293

J/g

for

3.4-7.

peak melting temperature (125 °C) according to

polymer

of fusion of once-molten

[12].

calculated

to

in the

enthalpy

4)

according

3.5-3.18.

supplier; except forM„ log-normal

of PE 2000

to

[13].

(see 6).

distribution.

3.2.3 Characterization

Gel Permeation

All values of

Chromatography

Mn

and

Mw

were

determined

by High-Temperature

section

Chromatography (HT-GPC) (see experimental

Gel Permeation

Chapter 2).

Thermal Analysis

Thermal model

analysis

200),

(at

conducted with

calibrated with Indium.

10 °C/min under

of

was

a

a

Netzsch differential

Samples

scanning

of about 5 mg

nitrogen atmosphere. Crystallinity

was

were

°C/min) material, adopting

the value of 293

J/g

heated at

calculated from the

fusion, determined from the endothermal peak of once molten (at 10

calorimeter

for 100 %

180

°C)

crystalline

a

(DSC, rate

of

enthalpy

and cooled

PE

[12].

Microscopy

Optical photomicrographs using

a

Leica MS5

of different

samples

were

taken at

a

magnification

of 15-25 x,

stereo-microscope.

Profilometry

Profilometry

was

carried

Forschungsanstalt, Dübendorf,

out

at

CH with

the a

Eidgenössische

Materialprüfungs-

Profilometer Tencor P10.

und

-37-

3.2.4 Abrasive Wear Methods

To determine the

used:

resistance of the various

wear

sand-slurry test, pin-on-disc

and

test

grades,

mico-scale

a

of each of these test will be discussed in

principles

three test

procedures

abrasive-wear test.

detail in the

more

have been

following

The

sections.

Micro-Scale Abrasion Test

Abrasive

wear

specifications

measurements

with

a

two

coaxial

400

nm

an

water)

abrasive cases, was

slurry (0.75

dripping

wear

crater

spherical

calculated

a

onto was

craters

according

a

custom-built device

a

hard

Bearing

constant

a

g SiC

(mean particle a

observed

an

Co.

size of 4-5

a

the

of the test

Carbide ball

sample

pivoted L-shaped

/min. The size of the

resulting

section

corresponding

3.2.3).

wear

to:

the measured diameter of the crater

empirical

rule

surrounded

(according

d

by

a

wear



craters

roughened

to Trezona et

=

V

In all

volume V

where R is the ball radius and d is the surface chordal diameter of the crater

spherical

arm,

distilled

per

r-(%$ correct

was

cm

microns)

optical microscope (see

(cf. Figure 3.5);

to

Ltd., UK) clamped between

using

cm

according

diagram

of 200 rpm. The

speed

feed rate of 0.5

measured with

A schematic

sphere (1" Tungsten

normal force of 0.25 N

the ball at

were

device,

Atlas Ball &

rotated at

the ball with

using

by Hutchings [14].

3.2. In the

roughness,

driving shafts,

abrasive

was

Figure

surface

placed against while

carried out

and method described

is shown in

procedure

were

0.9358

J

d=d ford> 2.193

al.

or

[16])

for 0.5

(d),

which

typically

'scuffed' annular was

mm
a

_l

I

I

I

I

I

l_l_

_l

I

I

I

I

10

'

'

_i

i

i_

100

N(-)

Figure

effective physical for a)

n

coefficients,

3.10 Wear

=

0 and

K,

of all

materials

plotted

crosslinks per macromolecular chain,

b)

n

=

1.

Designation of the symbols

versus

the average number

Nc, according

is in Table 3.1.

to

of

Equation 3.4,

-49-

(a)

7

r

r B B

5

-

o

U C

A

'3 a

_l

I

I

I

I

I

l_l_

_l

I

I

I

I

'

'

10

_i

i

i_

100

N(-)

(b)

7

r

r 5

-

o

U

'o

^A



io4

^St

io3 10"'

iou

10" co

101

10

(rad/s)

**a»***ï

10

10 co

Figure

(a)

5.8 Linear viscoelastic characteristics

absolute value

modulus, G',

of the complex

versus

compositions,

resp.:

shear

(rad/s)

of various

viscosity

shear rate. The notations

10

PTFE blends

versus

shear rate;

a-fcorrespond to

(V+XI)

at 380

(b) storage

°C;

shear

the following V/XI blend

100/0, 80/20, 60/40, 40/60, 20/80and0/100.

-90-

10

10

10

10

M (g/mol)

Figure

from

5.9

Logarithmic

molecular

weight

distribution

the storage shear modulus using the Tuminello

The notations

a-e

correspond

to

the

following

60/40, 40/60, 20/80 and 0/100. Compositions and

yielded mechanically

curve

(c)

in

coherent and

c

of PTFE compositions transform (ref 16;

see

calculated

appendix).

V/XI blend compositions, resp.: 100/0,

and d

were

found to

be

melt-processable

tough products (see, for example,

stress-strain

Figure 5.12).

04

06

10

Weight fraction (-)

Figure

XI). to

5.10 Zero-shear

The solid line

is

Menefee (ref. 25).

viscosity

vs.

composition ofPTFE blends (V+XI, weightfraction

the zero-shear viscosity-composition relation calculated

according

-91

.-••"'"

-

a

o

c

0.1

3

-^b

c

n n

i

i

„

1050

i

i

1000

Wavenumber

Figure ratio

5.11

Infrared spectra of (a)

PTFE and

900

(cm" )

(b)

blend

of PTFE grades

V

+

XI

(weight

10-90).

A most illustrative set of data,

increasing in

i

i

950

Figure

revealing the development

of mechanical characteristics at

viscosities and their variation with the PTFE blend 5.12. This

figure displays

a

composition,

is

presented

series of stress-strain curves, recorded at

room

temperature, of melt-compression molded films (thickness 0.25 mm) of (most of) those blends. The

gradual

strain to break different PTFE results in

and smooth increase in the zero-shear

(Figure 5.12) grades

Figure 5.13,

was

indeed appears to indicate that molecular

in which the tensile

content

and which

of HMW-PTFE.

mixing

achieved for the blends at hand. This is also illustrated

Young's modulus (cf. Table 5.4),

composition

viscosity (Figure 5.10)

were

are

strength, yield stress,

graphically displayed

found to vary

according

to

and

of the

by

the

strain at break and the

as

a

function of blend

expectation

with

increasing

-92-

20

15

10 -f

),

whereas

relatively

low

are

of crystallinity of 50-60 %

of a

and

to

belonging

higher density

logically,

melt-processable grades

LLD-PTFE).

a

versions of

the term "HDPE" is used in

Analogously

sensibly applied

classified

display degrees

28), and, therefore,

forms; for this

>80

for

hand, melt-crystallized medium and lower

of both PTFE and PE

weight grades

terminology could

a

of about 30-40 %>. On the other

corresponding parlance

of

molecular

materials, after crystallization from the melt, exhibit

same

molecular

are

scanning calorimetry,

in

certain to

the

the

family

common

designation

of PTFE

copolymers

than their

"HD-

(Similarly,

this

of PTFE; e.g., FEP

of linear

low-density

100-

-

noted certain salient similarities in the behavior of PE's and PTFE's in their

Having molten

[16, 29] and solid forms (this chapter), the question (re-)emerges

requires other

substantially higher

a

polymers,

already

to

form

stated in the

weight,

(semi)-crystalline

introduction, it

interchain bonds in PTFE

alternative, origin

molecular

was

responsible

are

solids of a

mechanical

adequate

time ago

long

for this

necessity.

PTFE most

properties.

As

[9] that the

very weak

additional,

or

An

be found in the macromolecular

may

why

rather, longer chain length than

or,

argued

to

as

perhaps

requirements

for "elastic

composed

of extended-

transmitted via the

crystal grain

percolation". It is well known that

chain

crystals

boundaries

isotropic, organic

molecular solids that

brittle, because applied

are

stresses

of such materials

only. Toughness

are

are

develops solely

constituent molecular chains exceeds the "thickness" of the

bridges

between

typically 10 nm;

forms

phase

(orthorhombic) crystalline regions

4-5 times that value

corresponding

crystallized

from the

often

by

a

factor of 10-20

noted that when PE is

hexagonal, highly

crystallized

mobile

very similar to those of PTFE PTFE

crystals

in

comparison

the minimum chain

larger than

length

that of PE

(in

for

phase,

are

analysis

and

an

or

weights

of

example

obtained).

at

Figure

appears

Upon

polyethylene

a

that

are

5-10

extremely high mobility (hence

high

crystals

pressures

Due to the

tough

weight,

about

g/mol.

hexagonal crystal phase [30]

of

a

its

high

thickness that

[32, 33]. (It should be

under conditions where it also first forms

of molecular

assumptions,

5.17.

approximately

more, than those of PE

for PTFE to form

terms

Figure

lengths

a

similar

[34], crystals thicknesses

dramatically larger

with those of commonly solidified PE,

the data in Tables 5.3 and 5.4 and crude

display

chain

at

in turn to the formation of

melting temperature [29]), leading larger,

molecular

of

of characteristic thickness of about

melt, it first forms

in which the chains

(see Figure 5.18)

are

to

in

length

and form covalent

-under ambient conditions- linear

thus, this polymer forms tough solids only

When PTFE is

crystals

them, which is schematically represented

from the molten

crystallization

when the

one

thickness of

must

expect that

solids also be at least 10-20 times >

2-4-10

g/mol).

A cursory view of

5.9 reveals that this estimate in view of the very

satisfactory.

-

101

-

Poly(tetrafiuoroethylene)

Polyethylene

/ M

10

/

nm

(min):

~4

*

M

80 C-atoms

~4

-4,500 g/mol

Figure

=

-200

nm

(min): *

1,600 C-atoms

-320,000 g/mol

5.17 Elastic

percolation requirements for polyethylene

and

poly(tetrafiuoro¬

ethylene).

275

300

325

350

375

400

600

625

650

675

Temperature (K)

Figure

5.18

Pressure-temperature

phase

diagram for poly(tetrafiuoroethylene)

(reproduced in part with permission from ref. 31).

-

Compounding, fillers

With

with this

applied

of fillers

adding

unique polymer.

cover a

reduce cost

to

enhance the

glass fibers, or

properties

stainless like

to

of

dispersions

coagulate

the

obtain

polymer,

with

an

removed, before

or

and

finely

for

divided solids added to

Fillers range from

minerals,

of PTFE, the

undergone

resistance

or

fillers

following

in order to

dyes

surface-

metals

are

of

(such

as

improve important

thermal-

by dry mixing

electrical

or

them with the

of the added material to adhere to

tendency

uniform

dispersion. Alternatively,

dispersion polymerization

process

additives

when the

are

one

added to

polymer

has

[40]. Upon coagulation

material, they become mixed with the coagulated solid

thus

resulting

in

a

clump during

poor

the

dispersion.

agitation

that is needed

In order to achieve

considerable research has been conducted to

dispersion [e.g. 39]

aqueous

With the

and additive

powder

are

(KevlarR) pulp, graphite,

wear

example,

synthetic inorganic compounds. They

case

additives often tend to

granular powder [40, 41]. the PTFE

a

for

be

can

important requirement

non-melt-processable PTFE, especially

homogeneous distributions, mixing-process

due to

an

and if necessary, have

In the

now

high processing temperatures

such additives have been added

and the added

polymer

fillers

or

shapes

fibers, aramid

the aqueous

polymer. Unfortunately, to

products

compression resistance,

produced by

due to the

steel), pigments (Ti02)

another, it is difficult

of the

'waste'

carbon

polymer powder; however,

aqueous

dyes. Naturally,

improve properties.

to

compatibility.

conductivity. Heretofore,

been

or

processing techniques

interesting possibilities of,

general,

In

wide range of particle sizes and

interest: bronze

employed.

are

powders, organic

treatment to

of

use

high-temperature stability

which

polymer systems metallic

This leads to

[e.g 35-38] and the

these additives is

(-350-400 °C)

dyes

and

of "HD-PTFE", conventional

discovery

our

102-

after the

use

can

or

to

intensify

the

modify

mixing

of conventional lubricated extrusion

also be

processed

more

the

with the

techniques

after which the lubricant is

subsequent forming technique [42-44],

followed

by

sintering.

In

a

first attempt to

investigated, ratio

explore

the

"compoundability"

all of which the continuous

10-90, and which

extruder, operated

were

at 380°C.

phase

produced

of HD-PTFE, various systems

consisted of PTFE

with the Brabender

The filler content,

(f),

was

grade

V

XI, weight

+

co-rotating

varried from 10 wt% =S

were

twin-screw

(f)

=S 30

wt%>.

-

The well-known and with the an

use

widely

of conventional

optical micrograph

Ti02

shows

a

of

used

pigment, Ti02

(-100 nm)

remarkably homogenous

Similarly, Figure

5.19

(b)

shows

a

products.

homogeneously advantage

Figure

colored

a

welding

shows

macroscopic

neck

a

dyes

optical and

a

introduced in PTFE

Figure

in

(Figure can

was

5.21

a)

system containing 20 wt% carbon

were

compounded

micrographs blue)

of

in PTFE,

samples.

HD-PTFE

a

samples.

A further

notorious in

of

problem

Figure 5.21,

and simultaneous

The tensile bar shown contains

and after tensile-deformation ran across

yielding

cross-sections

produced by melt-compression

be observed which

(a). Here,

particles (), using [16].

To this extent, the square root of the reduced

function of

as a

was

hyperbolic tangent function, using

a

log(co),

was

fitted to the

nonlinear least squares

modulus,

following two-component

Levenberg-Marquardt (LM)

algorithm:

^05 where x

=

2]^= 1,

0 =s

log(co). Next,

relative molecular 1/(0

the

=

molecular

1

-

Wu,

weight.

+

tanh(g;(*+ Q]

\,Bt> ln(10)/6.8 (to

=s

logarithmic frequency

weight

axis

Subsequently,

ocMw

CMD(M)

Ax

^41

was

using

an

the

obtained

axis

ofMw andM„)

transformed to

a

5

cumulative

CMD(M)

logarithmic

weight

transformed into absolute molecular

weight

molecular versus

the

with respect to

distribution.

Finally,

weight

logarithmic to:

distribution,

logarithm \og(M)

3)

and

arbitrary proportionality constant, according

differential was

convergence

was

by plotting \-Wu

The derivative of molecular

ensure

(£Q

of relative

resulted in the

the relative molecular

weight by matching

the relative

weight-

-

-

average molecular

weight

to

viscosity (see text).

For the

plateau modulus, G°N,

value of

G°N

1.7 MPa

=

was

the

109

obtained from the

experimental value,

adopted,

as

a

determined

critical parameter in the

by

Tuminello et al.

shear

zero

analysis,

a

[16].

5.6 References

1

The

ethylene comprising 2.

refers to

designation "poly(tetrafluoroethylene)"

Gangal, S.V.,

in

less then 0.5 mol % of

a

polymers

of tetrafiuoro¬

comonomer, ISO 12086.

Encyclopedia ofPolymer Science

and Engineering, 2nd

ed., Mark,

H.F, Bikales, N.M., Overberger, CG, Menges, G, Eds., Wiley: New York, Vol. 3.

16,

p.

577(1989).

Banks, R.E., Willoughby, B.G,

in The

Encyclopedia ofAdvanced Materials, Bloor,

D., Brook, R.J., Flemings, M.C., Mahajan, S., Eds., Pergamon: Oxford, 1994, Vol.2,

p.

862(1994). inModern

Fluoropolymers, Wiley:

New York

4.

Scheirs, J., Ed.,

5.

Bro, M.I., Sandt, B.W., US Patent 2,946,763 (1960).

6.

Grulke, Cliffs,

7.

p.

E.A. in

Process

Engineering,

PTR Prentice Hall:

Englewood

42(1994).

Seymour, R.B., p.

Polymer

(1997).

in

Engineering Polymer Sourcebook; McGraw-Hill:

New

York,

13,214(1990).

8.

Doban, R.C., Sperati, CA., Sandt, B.W., SPE Journal, Nov.,

9.

Sperati, CA., Starkweather, H.W., Jr.,

Fortschr.

17

(1955).

Hochpolym.-Forsch., 2,

465

(1961). 10.

Hintzer, K., Löhr, G, ref. 4,

11.

Plunket, R.J.,

12.

ref. 3, p. 863.

13.

e.g.:

14.

Smith, P., Visjager, J., Bastiaansen, C, Tervoort, T.,

15.

e.

2183

US Patent 2,230,654

Zonyl MP®

g.:

p. 240.

(1941).

Technical Information

Sheets,

(a) Suwa, T., Seguchi, T., Machi, S.,

J.

DuPont

(1998).

Int. Pat.

Appl.

Polym. Sei., Polym. Phys. Ed., 13,

(1975); (b) Chu, B., Wu, C, Buck, W, Macromolecules, 21,

16.

Tuminello, W.H., Treat, T.A., English, A.D., Macromolecules, 21,

17.

Starkweather, H.W, Jr., Zoller, P., Jones,

Phys. Ed, 20,7'51 (1982).

G

WO 00/08071.

397

(1988).

2606

(1988).

A., Vega, J., J. Polym. Sei., Polym.

110

-

-

(1954).

18.

Bunn, C.W., Howells, E.R., Nature, 174,

549

19.

Doughty, T.R., Jr., Sperati, CA.,

Un, H, US Patent 3,855,191 (1974).

20.

Polymat, Werkstoffdatenbank,

21.

Grace, H.P, Chem. Eng Commun., 14,

22.

Starita, J.M.,

23.

Cox, WP, Merz, E.H., J. Polym. Sei., 28,

24.

Yasuda, K., Armstrong, R.C, Cohen, R.E.,

25.

Menefee, E., J.Appl. Polym. Sei., 19,

26.

Smit, R.J.M., Brekelmans, W.A.M., Meijer, H.E.H., J. Mech. Phys. Solids, 47,

Trans. Soc.

Ho-Wei

Deutsches Kunststoff-Institut

Rheol, 16,

(1989).

(1982).

225

(1972).

339

277

619

(1958).

Rheol.

Acta, 20,

163

(1981).

(1972). 201

(1999). 27.

e.g.

Smith, P., Chanzy, HD., Rotzinger, B.P, Polymer Commun., 265,

28.

e.g.

Capaccio, G, Ward, I.M., Polymer, 15,

29.

Flory, P.J., p.

in Statistical Mechanics

233

(1974); ibid, 16,

of Chain Molecules,

239

258

(1985).

(1975).

Interscience: New

York,

157(1969).

30.

Bunn, C.W., Cobbold, A.J., Palmer, R.P, J. Polym. Sei., 28,

365

31.

Wunderlich, B., Macromolecular Physics, Academic Press,

New

(1980) [Copyright

© 1980

by

Academic

Kolloid-Z. Z.

Polym., 250,

Melillo, L., Wunderlich, B.,

33.

Bassett, D.C., Davitt, R., Polymer, 15,

34.

Wunderlich, B., Melillo, L.,Makromol. Chem., 118,

35.

Xiao-Qun, W, Jie-Cai, H., Shan-Yi, D.,

36.

Li, F., Yan, F.Y, Yu, L.G, Wear, 237,

37.

Zhang, Z.Z., Xue, Q.J., Liu, W.M., J. Appl. Polym. Sei., 74,

38.

Zhang, Z.Z., Xue, Q.J., Liu, W.M.,

39.

Tsakumis, TG,

40.

Gangal,

S. V, in

York, Vol.3,

721

J.

33

417

(1972).

(1974).

Reinf

250

Plast.

(1968).

Comp., 17,

1496

16,

p. 581

(1998).

(2000).

Tribol.

Int., 31,

361

797

(1999).

(1998).

(1983).

Encyclopedia of Polymer

Science and

Engineering, 2nd ed.,

Mark, H.F, Bikales, N.M., Overberger, CG, Menges, G, Eds., Wiley: Vol.

New

(1989). (1983).

41.

Crocker, Z.,

42.

Gore, R.W, US

Patent

3,953,566 (1976).

43.

Gore, R.W, US

Patent

4,096,227 (1976).

44.

Bowman, J.B., US Patent 4,598,011 (1986).

45.

Xue, Y.Q., Tervoort, T.A., Lemstra, P.J.,Macromolecules, 31,

US Patent 4,420,449

p. 92

Press].

32.

US Patent 4,397,980

(1958).

3075

(1998).

York,

-

46.

Guide to the Safe

Ill

-

Handling of Fluoropolymers, 3rd ed.,

Washington (1998).

Soc. Plastics

Industry,

Inc.:

6. General Conclusions and Outlook

The aim of this thesis

respect

convenient

to

mers, i.e.

molecular

to

optimize

processability

polyethylene

ultra-high

was

and

the molecular

and maximal

weight

distribution

(MWD)

with

for two

poly¬

currently

their

(mechanical) properties

poly(tetrafluoroethylene),

in

applications

were

form is used.

weight (UHMW)

Polyethylene

In

Chapter 2,

so-called

a

detailed relation between molecular

"double-reptation model")

successfully predicts molecular

weight

the

rheological

distribution

applied

was

behavior

using only

parameter. On the other hand, in chapter 3 it

weight

it is

6.1). Hence,

one

subject

physical

shown that for this

of this outlook to

processing (listed

in Table

6.1)

with

the

superior

from the

viscosity)

wear

polymer,

use

unique

Nc (see Figure

both relations to

design

commonly accepted limiting

abrasive

a

coefficient K, which resides

crosslinks per macromolecule

processable polyethylene grades according to

relation

(temperature-dependent) adjustable

one

was

shear

rheology (the This

polyethylene.

(steady-state

correlation exists between the MWD and the abrasive in the average number of effective

to

distribution and

wear

melt-

values for

properties. Secondly,

both

relations will be used to examine the effect of standard industrial modifications of the MWD to enhance

Table 6.1

processability.

Commonly accepted limiting values ofshear rate techniques.

and

viscosity for some

standard polymer processing

Technique

(s"1)

y

n

(Pa-s)

Injection molding

IO3