a collaborative study of the stability of...

Pure & App!. Chem., Vol. 59, No. 2, pp. 193—216, 1987.Printed in Great Britain.© 1987 IUPAC

INTERNATIONAL UNION OF PUREAND APPLIED CHEMISTRY

MACROMOLECULAR DIVISION

COMMISSION ON POLYMER CHARACTERIZATIONAND PROPERTIES

WORKING PARTY ON STRUCTURE AND PROPERTIESOF COMMERCIAL POLYMERS*

A COLLABORATIVE STUDY OF THESTABILITY OF EXTRUSION, MELT

SPINNING AND TUBULAR FILMEXTRUSION OF SOME HIGH-, LOW-

AND LINEAR-LOW DENSITYPOLYETHYLENE SAMPLES

Prepared for publication byJAMES L. WHITE and HIDEKI YAMANE

Polymer Engineering Center, University of AkronAkron, Ohio, USA

*Membership of the Working Party during the preparation of this report (1983—85)was asfollows:

Chairman: H. H. Meyer (FRG); Secretary: D. R. Moore (UK); Members: G. Ajroldi (Italy);R. C. Armstrong (USA); C. B. Bucknall (UK); J. M. Cann (UK); D. Constantin (France);H. Coster (Netherlands); Van Dijk (Netherlands); M. Fleissner (FRG); H.-G. Fritz (FRG);P. H. Geil (USA); A. Ghijsels (Netherlands); G. Goldbach (FRG); D. J. Groves (UK); H.Janeschitz-Kriegl (Austria); P. B. Keating (Belgium); H. M. Laun (FRG); A. S. Lodge (USA);C. Macosko (USA); J. Meissner (Switzerland); A. Michel (France); A. Plochocki (USA);W. Retting (FRG); K. P. Richter (FRG); G. Schorsch (France); G. Schoukens (Belgium); J. C.Seferis (USA); J. M. Starita (USA); G. Vassilatos (USA); 3. L. White (USA); H. H. Winter(USA); 3. Young (Netherlands); H. G. Zachmann (FRG).

Republication of this report is permitted without the need for formal IUPAC permission on condition that anacknowledgement, with full reference together with IUPAC copyright symbol (© 1987 IUPAC), is printed.Publication of a translation into another language is subject to the additional condition of prior approval from therelevant IUPAC National Adhering Organization.

A collaborative study of the stability of extrusion,melt spinning and tubular film extrusion of somehigh-, low- and linear-low density polyethylenesamplesAbstract — A comparative study by several industrial and academic labor—atones of the shear and elongational rheologica behavior and unstableprocessing behavior of a series of well characterized linear and branched

polyethylene is reported. The processing operations investigated wereflcw through a die, melt spinning and tubular film extrusion. Broadeningmolecular weight distribution in the linear polyethylenes increaseddeviations from Newtonian flow, increased elastic memory and decreasedfilament stability in elongational flow. It also deteriorated melt spin—ning stability but broadened the range of stable operation in tubularfilm extrusion. Extrudate distortion occurred at the same critical diewall shear stress, but the characteristics of the unstable region were

changed. Long chain branched polyethylenes exhibited generally enhancedelastic memory, greater stability and deformation rate hardening inuniaxial extension. Melt spinning and tubular film extrusion character-istics were stabilized relative to linear polyethylenes, but extrudatedistortion first occurred at a lower shear stress. The unstable extrusioncharacteristics were quite different from the linear polyethylenes. The

linear low density polyethylene investigated generally responded similar-ly to a linear polyethylene of about the same molecular weight distri-bution.

INTRODUCTION

No commercial polymer is more important or has received the sane attention as polyethylene.The rheolcgical and melt processing behavior has been widely studied. Two previous majorstudies by this IUPAC Working Party have characterized the rheological and film blowing

characteristics of low density and high density polyethylene (ref. 1,2).

The subject of instabilities is an important one to the polymer rheologist and process engi-neer. Four classes of instabilities have received considerable attention in the literature.These are instabilities in simple uniaxial extension of molten filaments (ref. 3,5), break-down of stable drawdown of molten filaments/films during melt spinning of film casting(ref. 6—13), instabilities in tubular films extrusion behavior (ref. 13—16) and unstableextrusion (ref. 17—23). All of these phenomena occur to varying extents in commercialpolyethylenes (ref. 3, 4, 13—16, 18—23). However, the extent and character of each seems tovary with the molecular weight, distribution of molecular weights and extent and types oflong chain branching. While there have been individual studies of these instabilities,little effort has been made to make a joint study of then.

In the present paper, we describe a joint study f the rheological properties and melt flowinstabilities using a series of molecularly well characterized polyethylenes, of varyingmolecular weight distribution, and extent and type of branching. This report describes thecontributions of thirteen European and North American Laboratories, of which nine were in-dustrial, three academic and one government. These organizations and the prionry investiga-tors are:

BASF AG Ludwigshaf en, West Germany (BASF) H.M. Laun

Borg Warner Amsterdam, Netherlands (BW) H. Coster

BP Chemicals Ltd. Grangenouth, UK (BP) S.T.E. Aldhouse

CdF Chimie Bully des Mines, France (CdFC) U. Constantin

Eidgenossische Technische Hochschuie, Zurich, Switzerland (Em) J. Meissner

Hoechst AG Hoechst, West Germany (Hoechst) M. Fleissner

ICI Wilton, UK (ICI) D.J. Groves

Industrial Materials Research Institute Boucherville,Montreal, Canada (IMRI)L.A. Utracki/P. Sammut

194

Polyethylene elongational flow instabilities 195

Koninklijke/Shell Laboratorium Amsterdam, Netherlands (Shell) A. Ghijsels

Montepolimeri Bollate, Italy (M) G. Ajroldi

Rheometrics Inc. New Jersey, USA/Frankfort, West Germany (Rheo) J.M. Starita/C. Frank

The Unviersity of Akron, Polymer Engineering Center, Akron, OH USA (APEC)J.L. White! Y. Yamane

The University of Massachussets, Amherst, Mass., USA (UN) H.H. Winter

Materials

EXPERIMENTAL

A series of six polyethylenes were included in this study. This includes three high densitypolyethylenes (HDPE), two low density polyethylenes (LDPE) and a linear low density polyethy-lene (LLDPE). Two HOPE (HDPE—1, HDPE—2) were supplied by Hoechst and the third HDPE—3 byDuPont. The two LDPE were supplied by BP. The L—LDPE was supplied by CdF Chimie. Thecharacteristics of these polymers are summarized in Table 1. According to Hoechst, HDPE—1and HDPE—2 contain some butene—1 as a comonomer.

Molecular weight distribution of the samples were determined by BP, CdFC, Hoechst and Insti-tute of Macromolecular Chemistry (IMC) of the Czechoslovak Academy of Science (IUPAC Sub-group IV—2.1.2) using gel permeation chronatography. The experimental conditions of GPCmeasurements are shown in Table 2. CdFC GPC traces for the polymers studied are containedin Fig. 1. The GPC was calibrated by polyethylene and polystyrene standards using Universal

TABLE 1. Characteristics of Polyethylenes Investigated

Symbol ManufacturedDensity (g/cm3)

(BASF) Melt Index

HDPE—1 Hoechst 0.944—0.946 0.06HDPE—2 Hoechst 0.939—0.942 0.45HDPE—3 DuPont 0.950—0.953LLDPE CdF Chimie 0.917—0.918 1.0LDPE—1 BP 0.921 0.2LDPE—2 BP 0.920—0.921 2.0

TABLE 2. Experimental Conditions for GPC Measurements

Laboratory Solvent Temperature Concentration Flow Rate

HP 1,2,4—Trichlorobenzene(TCB)

140°C adjusted

-

([JC=O.15) 0.5 ml/min

CdFC TCB 140°C 0.25% 1 ml/minHoechst TCB 135°C 0.1 % 1 ml/minINC o—dichlorobenzene 135°C ——— ———

Fig. 1. GPC traces for polyethylemes

io2 lO io6 lOMolecular Weight Molecular Weight

196 COMMISSION ON POLYMER CHARACTERIZATiON AND PROPERTIES

Calibration Curves. INC made branching corrections for LDPE samples. The results aresummarized in Table 3. The weight average molecular weights M of linear polyethylenes

orders as:

HDPE—1 >> HDPE—2 > LLDPE > HDPE—3 (BP)HDPE—1 >> HDPE—2 > LLDPE > HDPE—3 (CdFC)HDPE—1 >> HDPE—2 >> LLDPE > HDPE-3 (Hoechst)HDPE—1 >> LLDPE > HDPE—2 > HDPE (IMC)

N /M order as:w n

HDPE—1 >> HDPE—2 > HDPE—3 ... LLDPE (BP)HDPE—1 >> HDPE—2 > LLDPE > HDPE—3 (CdFC)HDPE—1 >> HDPE—2 >> LLDPE . HDPE-3 (Hoechst)HDPE—1 >> HDPE—2 > LLDPE > HDPE—3 (IMC)

where the double inequality in all cases indicates a factor of about two or more. HDPE—ihas a large high molecular weight tail, and HDPE—2 a more modest one.

Intrinsic viscosities, En] were obtained on all of the polyethylene samples in decahydronaph—thalene at 130°C (IMC). The [ii] were converted to viscosity average molecular weight usingthe expression

[i] = 4.60 x i02 . M°73 (1)

The crystallinities of the samples have been estimated by Hoechst from infra red. The re-sults are summarized in Table 4. The HDPE—2 has a crystalline fraction of 0.63 as opposedto the 0.67 value of HDPE—1 and HDPE—3. The LLDPE and LDPE—2 have values of 0.45, whileLDPE—1 has the lowest value of 0.43.

Hoechst characterized branching in the polyethylenes using infra red absorption and BP car-ried out similar investigations with C 13 nuclear magnetic resonance. The results are con-tained in Tables 5 and 6. These generally show that the HDPE—3 has the lowest level ofbranching. The HDPE—1 and HDPE-2 have some ethyl branches as expected. The LLDPE has verysignificant levels of ethyl branches, an order of magnitude or higher levels than HDPE—1 orHDPE—2. The LDPE—1 and LDPE—2 have levels of total CH3 about the same as LLDPE but the dis-tribution of branch lengths is greater. The difference in branching of the LDPE—1 and LDPE—2 are not clear.

Shear flow

Rheological characterization

The rheological properties of the polymer melts have been characterized using different ex-perimental techniques. Measurements of the shear viscosity were carried out variously incone—plate and capillary rheometers. Rheo and APEC measured the viscosity as a function ofshear rate in a Rheometrics System 4 and a Mechanical Spectrometer at 190°C. The measure-ments by APEC were carried on an instrument in the laboratories of Rheometrics. BP mademeasurements in a Rheometrics System 4 at 180° C. BW made studies in a Weissenberg Rheo—gonioneter at 170°C. Capillary rheometer experiments to determine viscosity were reportedby BASF, CdFC, Hoechst, ICI, IMRI, and APEC at 190°C.

Principal normal stress difference N1 measurements were made using a cone—plate geometry byBP and Rheo.

Linear viscoelastic oscillatory measurements

Measurements of dynamic viscosity r' (w) and storage modulus C' (w) were made by BW, CdFC,IMRI and Rheo at 190°C as well as by BW at 170°C and by Rheo at 150°C. The instruments usedwere a Pheo.metrics Dynamic Spectrometer with a pair of parallel plate of 1.25 cm in diameterand a Weissenberg Rheogoniometer with cone—plate mode (BW), a Contraves Kepes Balance Rheo—meter (CdFC), a Rheometrics Mechanical Spectrometer (IMRI) and a Rheometrics System 4 (Rheo).

Stress relaxation measurements following shear flow were made by BW at 170°C using an R18Weissenberg Rheogoniometer and at 190°C following sudden strain with a Rheometrics DynamicSpectrometer.

Elongational flow experiments

Uniaxial extension experiments were carried out in several laboratories including BASF,Hoechst, IMRI, Rheo, Shell and APEC. The appartus and experiments are described below.

BASF made measurements at constant deformation rate in an elongational rheometer at 150°C.

Polyethylene elongational flow instabilities

TABLE 3. Molecular weight distributions based on GPC and 1111

of Branching by BP

LongerPentyl than C61000c 1000C

197

Placerial M xfl

M x 1O30 N xV IO N x IOZ

N /NWtI N /5ZW (J ]boratotyHDPE—1 13 — 332 — 26 — — EP

20 — 315 1550 18 4.9 — CdFC

15 291 501 — 34 — 3.35 Hoechst

II — 274 (420) 25 — 2.58 INC

HDPE—2 19 — 145 — 7.7 — — BP

29 — 169 713 7.5 4.2 — CdFC

20 160 251 — 12 — 2.5 Hoechst

18 119 (235) 6.6 — 2.03 INC

HDPE—3 26 — 91 — 3.6 — — B?

38 — 129 415 3.4 3.2 CdFC

29 77 91 — 3.1 — 1.95 Hcechst

16 — 60 (95) — 5.0 — 1.46 INC

LLDPE 33 — 113 — 3.4 — — BP

36 — 143 356 3.9 2.5 — CdFC

34 94 110 — 3.2 — 1.67 Hoechst

20 124 (127) 6.2 — — INC

LDPE—1 17 123 7.6 — B?

25 190 836 — CdFC

—— — — — — 1.30 doechs_

12 395 (560) 33 1.11 I}C

LDPE—2 77

114

305 (219)

15

11

TABLE 4. Estimates of

Crystallinity by Hoechst

B?

CdFC

Hoechst

1)10

— 5.0 — —

431 5.2 3.3 —— — 1.05

23 — 0.39

TABLE 5. Infra Red Analysis

of Branching of Hoechst

Sample Crystallinity

HDPE—1 0.67HDPE—2 0.63HDPE—3 0.67LLDPE 0.45LDPE—1 0.43LDPE—2 0.45

Sample

Total1000C

CH3 EthylI000C

HDPE—1 3.4 1.2HDPE—2 3.2 1.6HDPE—3 <2 <0.2LLDPE 21.6 13.6LDPE—1 25.0 6.5LDPE—2 26.5 5.1

TABLE 6. C 13 Nuclear Magnetic Resonance Analysis

SampleMethyl1000C

Ethyl1000C

1,3-Diethyl1000C

Butyl1000C

HDPE— 1 —— —— ——— —— —— 2.2HDPE—2 —— —— ——— —— —— 1. 1HDPE—3LLDPE —— 18.0 1.5 —— —— 1.3LDPE—1 4.2 1.4 0.5 7.4 2.5 3.1LDPE—2 0.7 5.0 0.9 6.0 2.2 3.2

198 COMMISSION ON POLYMER CHARACTERIZATION AND PROPERTIES

The rod—like sample was prepared by extrusion. It was floated on silicone oil in a bath withelectrically heated walls. Fig. 2 shows a schematic drawing of the rheometer. It has beendescribed by Laun and Nunstedt (ref. 24). A pair of toothed wheels (W) is used to stretchthe sample (S) and the other end of the sample is glued to a metal strip (N) that is con-nected to the leaf spring of a force transducer. To check homogeneity of sample deformationand to determine the recoverable strain, the sample is cut by means of scissors after agiven total strain. Local control of the apparatus was used and a constant Hencky strainrate imposed by a constant rotary speed of the servo motor.

Hoechst, INRI, Rheo and Shell made experiments with a Rheometrics Extensional Rheometer (seeFig. 3). The specimens to be stretched in this experiment are prepared by compression mold-ing. The measurements of Hoechst and Rheo were at 150°C, those of Shell at 190°C.

APEC made experiments on an apparatus newly developed by H. Yamane in its laboratories (seeFig. 4). It is similar in design to the BASF instrument described above and is based onipgrading of an instrument originally described by Yamane and White (ref. 25). The speci-mens were prepared by extrusion.

ICI measured elongational viscosities using die entrance pressure drops. These were comput-ed using the theory of Cogswell (ref. 26).

Equal biaxial extension measurements followed by stress relaxation werea Rheometrics RDS—LA rheometer using lubricated squeezing silicone oilsViscasil) were used as the lubricants. This is illustrated in Fig. 5.

carried out by UN in(General Electric

Fig. 4. APEC elongational flow rheometer Fig. 5. UM lubricated squeezing flow

experiments

Fig. 2. Elongational flow apparatus of BASF Fig. 3. Rheometrics extensional rheometer

Melt spinning (Fig. 6)


Melt spinning experiments were carried out by BP,mental procedures are described below.

CdFC, Hoechst, Shell and APEC. The exper—

BP used El Goettfert Rheotens apparatus which measures the take—up velocity, vL and spin—line tension F. The melt temperature was 180°C. The spinline was not thermostatted.The spinline length from the die face to the axes of the3take—up rollers was 121 mm.Tests were conducted at output rates from 130 to 530 mm. /sec. The take—up speed was chang—ed continually. The rate of change of take—up was kept low and did not affect the results.

CdFC used a Tcyoseiki melt tension tester, which is a ram extruder with a tension measuringtake—up device. A die of diameter 2 mm. and L/D ratio of 4 was used. The melt temperaturewas 190°C. 3The spinlinc which was not thermostatted had a length 250 mm. The extrusion ratewas 11.8 mm /sec. Experiments were carried out at constant take—up speed which was thea in—

creased by step.

Shell carried out melt spinning experiments with a Goettfert single screw laboratory extrud—er with a screw diameter of 20 mm and length of 40 mm. A capillary die of diameter 3 mm.L/D of 10 and 900 entrance angle was used. The melt temperature was 190°C. Most experimentswere carried out under non—isothermal conditions (cooling of extrudate y ambient air). Thespinline length was 180 cm. and the mass flow rate 10 g/min. (219.3 mm /sec). The filamentswere drawndown using a Goettfert Rheotens. One series of experemnts was carried out with

steadily increasing take—up velocity (acceleration = 1.2 mm/sec ). Another series was per-formed at constant take—up speed conditions so as to measure the extent of draw resonanceunder steady conditions. These experiments were started at low speeds which was then in-creased in steps into the region where draw resonance occurs. At each take—up speed, thediameter of the spinline at the position of the take—up wheels was continuously measuredby an optical laser technique. Both the amplitude and the periodicity of the instabilitieswere taken from these diameter data when a steady state pulsation of the diameter wasobtained.

APEC carried out melt spinning experiments with an Instron Capillary Rheometer. A capillarydie of diameter 0.147 cm and L/D of 28 was used for non—isothermal melt spinning, and anotherdie of diameter 0.107 cm and L/d of 29 was used for isothermal runs. For isothermal melt

spinning, an isothermal chamber was attached to the bottom of the barrel of the InstronCapillary Rheometer to keep the temperature of the spinline air the same as polymer melttemperature (Fig. 4). The distance between the die exit to the surface of the quench waterwere 7 cmn he isothermal case and 2.5 cm in the non—isothermal case. The flow rates were9.05 x 10 cm /sec. for both cases.

Tubular film extrusionTubular film extrusion experinents were carried out by APEC. A inch Killion Screw Extrud—er with tubular die and frame was used. An annular die of outer radius 3.175 cm. and gap of0.1 cm. was used. An extrusion rate of 1500 cm /hr was used in all of the experiments. Themelt temperature in the die was held as close to 190°C as possible. This is illustrated inFig. 7.

Extrusion instabilitiesExtrusion instabilities, notably extrudate distortion have been investigated by BASF, CdFC,ETh, N and APEC. BASF, ETH and N used Goettfert a Rheograph 2000 which has a barrel diameterof 3/8 inch. A Dynisco pressure transducer was placed at the capillary inlet. BASF usedcircular dies of diameter 0.5 mm to 2.5 mm and L/D ratio of 30. M used two dies with dia-meter 1 mm and L/D ratio of 0 and 30. APEC used a Monsanto Processability Tester with adie of diameter 0.762 mm and L/D = 30. CdFC and Brabender extrusiograph screw extruderwith dies of diameter 1.02 to 3 mm.

Die

Nip Rolls

Collapsing I

Take-up SystemFig. 7. Tubular blown film extrusion

Fig. 6. Melt spinning experiments experiments of' APEC


SHEAR VISCOSITY MEASUREMENTS

Results

Many Laboratories (CdFC, NP, Rheo, APEC) reported shear viscosity data at 190°C. These aresummarized in Figure 8 together with data of BP determined at 180°C. The data have greatqualitative similarities. The viscosity for all of the polyethylenes exhibits a plateauof low shear rates and then decreases with increasing rates of shear. The magnitudes ofthe plateau and1rates of decrease change from material to material. The data at a shearrate of 10 sec order as

HDPE—1 > LDPE—1 > HDPE—2 > LLDPE > LDPE 2 > HDPE 3

At a shear rate of 100 sec', the curves have re—ordered with

HDPE—1 HDPE—2 - LLDPE > LDPE-1 HDPE 3 > LDPE—2

There are differences in the data from the individual laboratories. Generally the results ofBP tend to be higher and CdFC lower in the low shear rate region. This should not be unexp-ected of the BP data as the measurements were performed at 180°C.

Interpretation

The viscosity function is well known to be related to molecular weight and its distribution(ref. 5, 25, 27, 28). In Table 7, we summarize zero shear viscosity of the polyethylenesstudied as a fraction as function of weight average molecular weight. It may be seen thatthe values of n for the LDPEs fall below the HDPEs and LLDPEs at specific M . The data onthe latter two olymers are roughly consistent. This effect has been ioted °y earlier in-vestigators (ref. 2, 30) studying the zero shear viscosities of linear and branched poly-

ethylene s.

TABLE 7. Zero shear viscosities as afunction of weight average molecularweight from polyethylenes studies

M x

Polymer CdFC Hoechst

no x 10(Pa S)

HOPE—i 315 501 >60

HDPE—2 169 251 3.97

HDPE—3 129 91 0.41

LLDPE 143 110 1.16LDPE—1 190 ——— 9.70LDPE—2 114 ——— 0.93

Fig. 8. Shear viscosity qof polyethylenes as afunction of shear rate at 190 C

The shear rate dependence of the viscosity frunction is widely considered to be related tothe breadth of the molecular weight distribution in linear polymer system. In Figure 9, weconstruct a Vinogradov—Nalkin plot (ref. 28) of n/n0 vs. for the HDPE—1 HDPE—2, and theIIDPE—3. The LLDPE which is also a linear polymer is included. Generally the rate of 'falloff' of the data orders as

HOPE—i > HDPE—2 > HDPE-3 - LLDPE

which corresponds to the breadth of the molecular weight distribution. The data may be com-

pared with earlier correlations of this type by Yamane, Ninoshima and White (ref. 13, 25).

A similar n/n0 plot for the LLDPE, LDPE—i and LDPE—2 is given in Fig. 10.

10

k

io2

(s')

1.0

Results


io2 io3 io4 io5 io6

Fig. 10. Reduced viscosity l7/ias a functionof for LDPE—1, LDPE—2 and LLDPE (CdFC)

PRINCIPAL NORMAL STRESS DIFFERENCE MEASUREMENTS

The principal normal stress differences N1 of the melts were reported by Rheo and BP. Rheo'smeasurements are presented in Fig. 11 as a function of shear stress. This type of plot hasbeen found by earlier researchers (ref. 5, 29, 30) to be independent of temperature and sen-sitive to molecular weight distribution. As shown by Coleman and Markovitz (31) at lowshear stresses N1 is related to shear stress as

N 21 e 12

Estimated values of J are summarized in Table 8. The data order ase

LDPE—1 > LDPE—2 > HDPE-2 > LLDPE > HDPE—1

(2)

The results cf BP were obtained on a parallel plate instrument. iJ, the principal normalstress difference coefficient was estimated. This was converted to J and the values arealso summarized in Table 8. BP could not obtain steady state data 0meHDPE_1 or LDPE—1. TheJ data order ase

LDPE—2 > HDPE—2 > LLDPE > HDPE-3

The Rheo and BP data are qualitatively consistent but differ quantitatively.

At high shear

gap.

rates instabilities develop in this instrument and the melt emerges from the

S

zio3

io2io2 (Pa) 10

o12

Fig. 11. Principal normal stressdifference N, as a function ofshear stress 12 for polyethylenes(Rheo)

TABLE 8. Steady State Compliance and Relaxation Time

for Polyethylene Samples (BP, Rheo)

Material

J (Pa) x 10e (BP)

Normal Stress

J (Pa) x 10e (nh)

Normal Stress

Je(Pa) x 10(Bheo)

DynamicT (sec)Rheo

}IDPE—1 ——— 0.22 0.9 40.5

HDPE—2 0.299 0.96 1.5 6.0

HDPE—3 0. 132 ——— ——— ———

LLDPE 0.283 0.54 1.1 1.06LDPE—1 ——— 1.7 1.6 14.4

LDPE—2 0.719 0.99 2.1 1.85

LLDPEHDPE—3HDPE—2

HDPE—l

1.0

LLDPELDPE—2LDPE—l

io1 102 1O3 1O4 l0 106 101Th,y(Pa)

Fig. 9. Reduced viscosity /ias a functionof i'' for HDPE—l, HDPE—2, HDPE—3 and LLDPE

(CdFC)

I I I

HDPE—l(190°C)

LLDPE (150°c)


Discussion

R1-ieo's data indicate that the steady state compliance and memory of LDPE—1 is greater thanthat of the other melts. The values for LDPE—2 are second in magnitude. From BP theHDPE—3 has the lowest J followed by LLDPE. This indicates the highest values are for the

long chain branched polyethylenes and the narrow molecular weight distribution linearpolymers possess the 'owest values. This is similar to earlier results for polyolef ins

(ref. 11—13, 16). The low value of J for the broad distribution HDPE—1 is surprising.

The mean relaxation time r was determined by Rheo from

JI1 =TeoThis is summarized in Table 8. The data order as

Results

HDPE-1 > LDPE-1 > HDPE—2 > LDPE-2 > LLDPE

LINEAR VISCOELASTIC MEASUREMENTS

(3)

Dynamic viscosity n'(w) and storage modulus G'(w) data have been reported by BW, CdFC, IMRIand Rheo as a function of frequency. i' (w) and G' (w) are plotted as a function of frequency

in Fig. 12 and 13. The complex viscosity n° defined by

* =J') + (G'/w)2 (4)

is plotted as a function of frequency in Fig. 14 for experiments carried out at 190°C. AtloW frequencies, the ii' and n* data order as

IIT)PE—1 > LDPE—1 > HDPE—2 > L—LDPE > LDPE—2 > HDPE—3

At a frequency of 100 sec1, the n*(w) data order as

HDPE—2 > L—LDPE > HDPE—1 > HDPE—3 > LDPE—1 > LDPE-2

BW also presents data at 170°C which order in the same manner.

The storage modulus G' data at 190°C is presentedThe data order as

in Fig. 13 at a frequency of 10'sec'.

HDPE-1 > LDPE—1 > HDPE—2 > L—LDPE > LDPE 2 > HDPE—3

Fig. 12. Dynamic viscosity 'rj(w) at 190°C forpolyethylene melts as a function of

frequency w (CdFC)

Fig. 13. Storage modulus G'(w) at 190°Cfor polyethylene melts as a functionof frequency u (Rheo, CdFC and IMRI)

1 o6

101

w (rads1)

100

1 02

10-1 100 101 io2

w (rad.s1)

Discussion

Fig. 15. Test of Cox—Merzrelationships between

'r(y) and *(w) (CdFC)

The Cox—Merz (ref. 32) empirical relationship connecting the complex viscosity n'(w) and theshear viscosity n(') appears to work rather well at lower shear rates especially if the dataof the same laboratory. e.g. CdFC, is used for each function. A comparison is made in Fig.15. At higher shenr rates deviations are observed esnecially for the LLDPE.

was computed from G' (w) and n' (w) by Rheo through the approximate relationship

The results are summarized in Table 8. The results order as

LDPE—2 > LDPE—1 > HDPE—2 > LLDPE > HDPE—1

which agree roughly qualitatively with those of the Rheo normal stress results but not in ab-solute magnitudes. The long chain branched LDPEs have the highest e and the narrow molecul-ar weight distributions linear polyethylenes the lowest.

io6

10


u (tad/a)

Fig. 14. Comples viscosity of polyethylene melts as a function of frequency w. (CdFC and BW)

10°

io2

100 101

- (sd) or w (rad.s1)

G'e

(wn ) w = 0.1 sec'(5)


Results

UNIAXIAL ELONGATIONAL FLOW

Elongational flow characteristics of the various melts studied have been reported by BASF,Hoechst, IMRI, Rheo, Shell and APEC. BASF using a rheometer built in their laboratoriespresents steady state elongational viscosities determined by BASF are plotted in Fig. 16.APEC carried out the elongational flow experiments on their apparatus (Fig. 4) at 190°C.Their results are shown in Figure 17.

c1o7a

io6

z0

11

010

a0

10

(a)

io0 101 iOrIME(S)

(b)' I I I

T150°C

1.13x102s'

}IDPE-2

I I I I10U 101 1OLTIME(S) 10 10

(c)

10

a

H100

H

a010

10

io0 101 io2 TiME(S)

io6H

10

100

10

a

810H

a0H 510

Is

1

a

H00H

a0H

IS

(d)

101 io2 TIME(S)

(e)

Fig. 16. Transient elongational viscosity X(t) for polyethylene meltsas a function of time t at 150°C (BASF)

a) HDPE—l b) HDPE—2 c) HDPE—3

d) LLDPE e) LDPE—l f) LDPE—2

HDPE—1

T=150'C

7.65x102s1.53x10 2 1

LLDPEI . I . .

T= 150° C

—3 —14.5x10 a

10'

LOPE—i

10 TIME(S) 10

(f)

T = 150° C

—1 —11 .5x102s13.OxlO

IIDPE—3iI . .1


3n

(a)

(b)

100 101 io2

t( s )

(c)

(d)

-

101

-

io2t( s )

(e)

'Ii

101

t( $ )

(f)

t (s)

io2

t(s)

Fig. 17. Transient elongational viscosity X(t) for polyethylenemelts as a function of time t at 190°C (APEC)



o1

,cio6

10 LLDPE-1 190'C110 2

2x102100

t( $ )

io6

HDPE-2 190C

•—10

lx

1o6

3n

I I I I I

LOPE-i 190C

5x103

I •

10 io2

HOPE—3 190°C

2x101

I I I I

J1:11x1:1100 io2


Elongational flow data on a Rheometrics Extensional Rheometer are given by Hoechst, IRNI,Rheo and Shell. Typical data of Hoechst at 150°C and INRI (150°C, 190°C) nrc shown in Fig.18 and Fig. 19.

The materials respond as three different groups. The HDPE—3 and LLDPE show slow buildups ofelongational viscosity to a steady state value. Their steady state elongational viscositiesare essentially Newtonian being equal to 3n. The LDPE—1 and LDFE—2 especially the formerare strain hardening. The broader molecular weight distribution HDPE—1 and HDPE—2 do notappear to achieve steady states.

The elongations to break from the Shell and APEC data are listed in Table 9. The values forHDPE—1 and HDPE—2 are lower than for the other melts.

ICI concluded using entrance pressure losses that HOPE—i, HDPE—2, HDPE—3 and LLDPE all ex-hibited decreasing elongational viscosities.

Discussion

It seems clear that the LOPE—i and LDPE—2 are strain hardehing and show increasing elong—ational viscosities while HDPE—3 and LLDPE are nearly linear viscoelastic. The LOPE—i andLDPE—2 are the most stable filaments and the HDPE—1 and HDPE—2 seem the most unstable inuniaxial elongational flow. This in agreement with early studies for similar materials(ref. 13, 16) and studies for the polyolefins (ref. 11,12)

Fig. 18. Transient elongational viscosityX(t) for polyethylene melts as a functionof time at 150°C on Rheometrics ExtensionalRheometer (Hoechst)

Fig. 19. Transient elongational viscosityX(t) for polyethylene melts as a functionof time t at 150°C and 190°C IMRI

(a)

HDPE—2

0C-,

z

"3 I

1O 1O 10°TIME(a)

(b)

10 10 1

TIME(s)

io_2 lo o ioTIME(s)


TABLE 9. Hencky Strains to Failure of Polyethylene Filaments

Polymers Stretch Rate (sec1) Shell APEC

HDPE—1 0.0050.010.020.050.250.501.00

2.52.51.55

3.43.02.93.0

HDPE—2 0.0050.010.020.050.250.501.00

1.2

1.61.6

5.33.73.84.0

HDPE—3 0.020.050.100.200.250.501.00

>3>3>3

8.07.98.28.3

MULTIAXIAL ELONGATIONAL FLOW

Polymers Stretch Rate (sec1) Shell APEC

LLDPE 0.010.020.050.100.250.501.00

>3>3>3

7.97.47.57.4

LDPE—1 0.0050.010.020.050.250.501.00

>3

>3

>3

6.66.05.75.6

9.58.78.2

7..6

LDPE—2 0.010.020.050.100.250.501.00

>3>3>3

The six polyethylene samples were strained to varying amounts H/il of 0.6 and 0.2 and the

relaxation rates followed. Typical results are shown in Fig. 20. Generally the high densitypolyethylenes show greater strain dependence of the stresses (noduli). Relaxation timeswere determined from the data. These are summarized in Table 10. They order as

HDPE—1 > HDPE-2 > HDPE—3 (190°C)

LDPE—1 > LDPE—2 > LLDPE (150°C)

TABLE 10. Relaxation Times from Biaxial Elongation flow Experiment of UM

Material Temperature (°C) TB (sec)at Eb = 0.26

HDPE—1 190° 59.3HDPE—2 190° 22.3HDPE—3 190° 3.26

LLDPE 150° 10.2LDPE—1 150° 52.0LDPE—2 1500 23.3

log It Is) I

Extensional relaxation modulus of LDPE—2

0.25, 0.62, 0.84

—2 —1

log It sI

Extensional relaxation modulus of HDPE—2

Rb0 0.27, 0.63, 0.86

0

9.5

9.0

3.5

5.0

a-

9.0

3.5

0 1 2

Fig. 20. Typical results of biaxial elongational flow and relaxation (UM)

208

Results

COMMISSION ON POLYMER CHARACTERIZATION AND PROPERTIES

MELT SPINNING

The melt spinning of the various polymers included in this study have been investigated byBP, CdFC, Hoechst, Shell and APEC. The studies of BP and CdFC concentrate on stable meltspinning behavior.

First we will summarize the research results on Shell. In Fig. 21, we plot spinline tensionas a function of drawdown ratio. It can be seen that the tension at low drawdown ratios VL/V0 exhibits small diameter fluctuations. At a roughly critical value of VL/Vn the ampli-tudes become much larger in magnitude. The actual amplitude of the diameter fluctuations isplotted in Fig. 22. The growth in amplitude is sudden and large in magnitude. The criticalvalues are summarized in Table 11. The materials studied order in terms of increasing stab-

ility

LDPE—2 > HDPE—3 > LDPE-1 > LLDPE > HDPE-2 > HDPE-1

The diameter oscillations are periodic in character. The resonance period and wavelengthare summarized in Table 12. The resonance period is independent of drawdown ratio andorders as

HDPE—2 > LLDPE — HDPE-3 > HDPE—1 > LDPE-1 LPDE-2

The experimental results of APEC generally correspond to those of Shell. The ordering of thestability differs with respect to HDPE—3, LLDPE and LDPE—1. The specific numbers are tabul-ated in Table 13. Another difference is that APEC finds that LDPE—2, the most stable mater-ial, much more resistant to draw resonance than Shell. Summarizing,

LDPE—2 > LDPE—1 > LLDPE > HDPE—3 > HDPE—2 > IIDPE—1

Hoechst and Shell drawdown the filamentci in the spinline until the filaments break. Thespinline rupture deta is summarized in Table 13. The extensibility to rupture orders as:

LDPE—2 > HDPE3 > LPPE—1 > LLDFE > hDPE-2 > HDPE-1

3

C

E2

6

0 2 4 6

Draw Down Ratio

10 12

Fig. 21. Spinline tension as a function Fig. 22. Amplitude of diameter fluctuationsof drawdown ratio (Shell) as a function of drawdown ratio (Shell)

I I

LLDPE

HDPE—1 HDPE-2HDPE-3

IIi

DRAW RATIO. V/V0RHEOTENS DIAGRAMS Draw Down Ratio


TABLE 11. Critical Drawdown Ratios

for onset of Draw Resonance

Material Shell APEC

HOPE—i 5.6 4.9HDPE—2 6.8 6.7HDPE—3 10.5 10.9LLDPE 9.3 11.7LOPE—i 11.2 15.1LDPE—2 23.2 45.0

TABLE 13. Spinline Rupture Data

Material

Sc (MPa)

hell

VL /V0

Hoechst

VLAo

HOPE—i 0.38 7.0 6.4HDPE—2 0.30 8.5 8.5HDPE—3 0.14 14.6LLDPE 0.24 12.0 11.8LOPE—i 0.70 13.3 13.2LDPE 2 0.60 26.4 >26.3

Discussion

TABLE i2. Periodicity of Draw Resonance (Shell)

Material

.Draw Ratio

LOResonance

.period(s)

Resonance

wavelength(cm)

HOPE—i 5.65.8

3.73.7

6466

HDPE—2 5.86.26.66.8

4.54.64.74.8

818895iOO

7.0 4.9 106HDPE—3 10.7

11.1

u.Sii.7

4.34.34.44.5

142147156162

L—LDPE 9.39.59.79.9

10.1

4.34.34.34.34.35

123126128132136

LOPE—i 8.511.211.712.012.6

2.452.62.62.652.6

65919599

101LDPE—2 23.2

24.225.2

2.52.452.5

182 —

185197

The results of the melt spinning experiments show the LOPE—i and LDPE—2 to exhibit the moststable spinlines and the HOPE—i and HDPE—2 the least stable. The LDPE—2 is the most strik-ingly stable of all the materials investigated. The HDPE—3 and LLDPE are intermediate intheir behavior.

Clearly the observations of the linear polymers indicate that spinline stability correlateswith narrowness of molecular weight distribution. This agrees with the previous results ofthe Shell (Ref. 10) and APEC (Ref. 11,12) research teams on polypropylene. The long chainbranched LOPEs are more stable than the linear polymers in agreement with our earlier studyof polyesters (ref. 30). Minoshima (13) has reached similar conclusion to those cited aboveusing a different set of linear branched (LDPE and LLDPE) polyethylenes.

Results

TUBULAR FILM EXTRUSION

The stability of the tubular film process for the five polyethylenes was investigated byAPEC. Following the procedure of Kanai and White (Ref. 16) and Minoshima (ref. 13) theregions of instability and stability are represented in a three dimensional space of draw—

down ratio (VL/Vo), blowup ratio (R/R0), and frostline height (z ). These three variablesrepresent the kinematics of deformation of the bubble. In Fig. 23 a—f we display constant

frostline height planes showing, regions of stability and instability. It would appear thattwo different types of instability are observed. At a blowup ratio 1.0 and at a high (blow-up ratio) x (draw down ratio) one finds the draw resonance type instability of Han and Park.At high blowup ratios one finds a bent and/or helically shaped bubble of the type describedby Kanai and White (Ref. 16) and Minoshima (ref. 13).

It may be seen that HDPE—3 is the most unstable of all of the polymers. It has indeed nostable operating region. The LLDPE is only slightly better. The LOPE—i, LDPE—2, HDPE—i and

HDPE—2 have much broader regions of operating stability. Summarizing stability roughlyorders as

Discussion

LDPE—i > LDPE—2 > HDPE-1 > HDPE-2 > LLDPE > HDPE—3

The studies described above clearly indicate that LOPE—i and LDPE—2 exhibit the most stablebehavior. The HDPE—3 and LLDPE are the most unstable. The behavior is basically the sameas that observed by Minoshima (ref. 13) on other polyethylene samples and similar to that ofKanai and White (ref. 16). The long chain branched LOPE polymers are the most stable follow-ed by the broad molecular weight distribution HDPE. The narrow distribution HOPE and LLOPEare the most unstable.


000010F 0 0 0 0 0 0Joo 0 0 0 0 0 0

0 0 0 0 0 010 0 0 0 0 0 0 07oo 0 0 0 o 0 0

00000000

0 0 •1

0 0 0 • •0 0 0 0 00 0 0 0 0o 0 0 0 0 0 0 o000000000

9 0 00 0

• • I

\\\ E

?00,000

0 0 00 0 0 0 0 0

• 100000000Joo 0 0 0 0 0 0

• loo00000001° 0 0 0 0 0 0 0• 000 0,0 0 0 o0

A/lA

0 0 0 0 00 0 0 0 0 00000000000000000

o 0 o•0 0 ? 0

A/lA

H)OH W0.00000•4 -P H-POWCd 0CO04- C\i cJ

0-Pd) CO 0 CO0OWH

0 -HCdC-CHO00. CO .0 Oo C) 00.

-H 1-4 0CO 0—C) C/)H0.0W H

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-P-HH•H.0• CCH -P• C/)0H

1-4)-P C)-P -H H-H H .0H -H .0-H .0 0.0 CCCC-P-P (/)000OH CdH H H

00 CC CCHH 00.0 .0 -H -HCC .0 H H-POC)C)cI)ZO4 e

°E o • 0

00000 00o o 0 0 0 000000 oooI,

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() HCO CO0.0.

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0 0 0 0 600 0 0 66

00O0 00 000 0 0 0 000 ooofr,eo

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'.

0 0000000__J , , 9 o 00 0 0 o0

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0 0 0 00 0 0 0 0o o 0 0 0 0 0 o'0o 0 0 0 0 0 0\ 4- 4- \ \

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0 0 0 00 0 0 0 0 00000000

\4\00u00000 00090000 I


The mechanisms for this variation must be primarily rheological in character. The behaviorof the LDPEs are certainly related to the strain hardening elongational flow characteristics.The HDPEs all have the same activation energy at viscous flow. The LLDPE behaves like theHDPE—3 in which it is rheologically similar despite undoubtedly having a higher activationenergy of viscous flow.

Results

EXTRUSION INSTABILITIES

BASF investigated the three HDPE melts at 190°C. In Fig. 24 extrusion pressure is plottedversus apparent shear rate. A steady extrusion pressure independent of the die cross sectionis observed for an L/D 60 die up to a critical shear rate , which is indicated by the symbol+. At higher shear rates a pulsation of the Dressure is found. In that range no data pointsare given. The extrusion pressure becomes steady again above the shear rates marked by. +.In that range the shear stress—shear rate behavior is dependent on the die cross section.This also implies the flow instability occurs at a critical shear rate of shear stress.

iO1 lO 1O 1O4 1Q5APPARENT WALL SHEAR RATE (s')

(a)

I10

0

H10

100

(U

0 4R'4 0*0) Lu

o 0

oo O. $0

o s 10, L2, 10

1

T = 190° C

0A

40

42

0.10 40

0.41 I

100 101 io2 io io io io6APPARENT WALL SHEAR RATE (s1)

LLDPE—1= 190°C

(U

00

APPARENT WALL SHEAR RATE (s1)

100 101 102 io io 105APPARENT WALL SHEAR RATE (s

io6

I I I4(4*1) UI (f)

0 Iii 0.40 40

10 A 422 0.40 0

FLD:100 io6

Fig. 24. Characteristic flow curves for polyethylene melts (BASF)

a) HDPE—l b) HDPE—2 c) HDPE—3 d) LLDPE e) LDPE—l f) LDPE—2

10APPARENT WALL SHEAR RATE (s1)


The LLDPE melt which was investigated at 190°C and 150°C exhibits a flow behavior which isvery similar to that of the HDPE melts. Pulsation of the extrusion pressure is most pronoun-ced at 150°C. The gap between the shear rates of steady extrusion pressure becomes broaderwith smaller diameter of the die.

In the case of the two LDPE melts, which were investigated at 150°C, no oscillation of thepressure was found nor a dependence of the flow curve on the die cross section.

In Table 14, we compare critical die wall shear rates and shear stresses The o dataunlike5the shear rate is independent of temperature. Te data is in the range of 05 to5 x 10 pascal.

ETH observed that HDPE—3 and LLDPE exhibit two unstable flow regimes and not a single un-stable reginre like HDPE—1 and HDPE—2. The characteristics of the extrudate are shown inFig. 25. The relationship of these extrudate shapes to positions on extrusion pressureapparent shear rate curves is shown in Fig. 26.

Type

L/D=30 D=Onset of Flow Inst

1.2mmabilities

T[°C] w' Gw[105I

HDPE—1HDPE—2HDPE—3

190

190190

3953301400

2.63.33.7

LLDPELLDPE

190150

670140

4.03.2

LDPE—1LDPE—2

150150

28567

0.480.85

I I I

HDPE-3 190°C

io2 L/D

101Extrudate Distortion

L/D ° 0.5

100

100

loll

I I

101 io2 io5 106

APPARENT SHEAR RATE Is1)I

LLDPE 190°C

10

io2

101

•

.

L/

0L/ Extrudate Distortion

100 I I

S10° 10' io2 io3 1O'

APPARENT ShEAR RATE (1)

TABLE 14. Characterization of ExtrusionInstabilities by BASF

0

z

LUcI/l

z0

F->(LU

0z

1/,

a-z0

F-xLU

A Q.

BO,.))1))IiDQTETT

Extrudates of LLDPE and HDPE-3

at Different Extrusion Rates

Fig. 25. Characteristic flowcurves for narrow MWD linear

polyethylenes (ETH)

Fig. 26. Shapes of the extrudatesof HDPE—3 and LLDPE at variousextrusion rates (ETH)

10 1&

Polyethylene elongational flow instabilities

CdFC who used a screw extruder, classified their observations according to:

They present their data as die wall shear rate as a function of screw speed, using die dia-meter as a running parameter (see Fig. 27). Dotted lines delimit different visual aspect

M U froct reSmooth /•2zone7i/Z/•'-

./h,or1ski/'./

-98 SmoothHDPE 3

2.5"/"1:190°C

N (tmin1)

0 i0(c)

213

N (t.min)I iii l IIII

02

—smooth

-sharkskin

—melt fracture—two zones

extrudate without any surface and diameter irregularities

regular extrudate diameter by thread aspect

extrudate with surface and diameter irregularitiesregular alternative zones of sharkskin and melt fracture

40D—(s7rtrShear roteD(s)

10

HDPE-l1:190°C

IC'

HDPE-2 102T:1900C

N (t.min)ii I I ui_i_i_I 1010 102

(a)

275

Screw Nspeed (t.min)

I uuuuuul I I liii102I0

(b)

:-4- (s) 0:- (s) D-(s)

0

i0

102

Melt

LLDPE —IT: 90°C

N (tmtn)

I0(d)

1.5

8

2.2

2.5

LDPE -I1:190°C

N (t.min1)

LOPE -2T:190°C

0(e)

I0(f)

Fig. 27. Apparent shear rate 4Q/irD3 as a function of screwrotation speed of extruder for polyethylene melts (CdFC)



214 COMMISSION ON POLYMER CHARACTERIZATION AND PROPERTiES

zones. There are differences between the five samples. We observe with increasing shearrate:

— smooth — sharkskin — two zones — melt fracturefor one HDPE sample (HDPE—2) and for LLDPE 1;for HDPE—3 there is a supplementary smooth zonebetween 2 zones and melt fracture.

— direct modification from smooth extrudate tomelt fracture for one IIDPE sample (HDPE—1) andfor the two LDPE samples.

Discussion

It is noteworthy that the three HDPE melts and LLDPE exhibit similar flow breakdown withinception of apparent slippage at about the same wall shear stress level i.e., 2.64.0 x 10pascal and thi probably the same mechanism. The LDPE breaks down at a lower shear stress0.480.85 x 10 pascal apparently by a different mechanism. This corresponds to the obser-vations of Tordella (ref. 23) more than a quarter century ago.

CONCLUSIONS

A series of linear polyethylenes of varying molecular weight distribution and extent ofbranching has been structurally and rheologically characterized in laminar shear flowand umiaxial extension. They have subsequently been investigated in a series of processingflows. Certaim gemeral conclusions may be reached classifying the stability behavior of thepolymer melts in the different flows investigated. Specifically for umiaxial extension thestability as rated in terms of kinematic variables (strçtch ratio) may be expressed as

LDPE-2 > HDPE-3 LLDPE > LDPE-1 > HDPE—2 > HDPE-1

For melt spinning the critical drawdown ratios order as

LDPE-2 > LDPE-1 > HDPE-3 LLDPE > HDPE-2 > HDPE-1

while for tubular film extrusion, the stability in terms of kinematics (drawdown ratio,blowup ratio) varies as

LDPE-1 > LDPE—2 > HDPE—1 HDPE—2 > LLDPE > HDPE—3

For extrusion instabilities evaluated in terms of shear rate

HDPE—3 > LLDPE > HDPE—1 > HDPE-2 (190°c)

LDPE-l > LLDPE > LDPE—2 (150°c)

and shear stress

HDPE—1 HDPE—2 HDPE—3 LLDPE > LDPE—1 LDPE—2

The rating in each case is different. Long chain branching seems generally stabilizing inelongational flows including uniaxial stretching, melt spinning and tubular film extrusion.Broadening molecular weight distribution in linear polymers is destabilizing for uniaxialstretching and melt spinning, but apparently stabilizing for tubular film extrusion.

PARTICIPATING MEMBERS AND LABORATORIES

Dr. H.M. Laur, Dr. S.T.E. AldhouseBASF AG British PetroleumD-ZKM-G201 P.O. Box 21D 6700 Ludwiqshafen/Rhein Boness RoadGermany Grangemouth, Stirlingshire FK 39XH

Scotland

Mr. H. CosterBorg Warner Chemicals Dr. D. ConstantinP.O. Box 8122 Societe Chimique des CharbonnagesAmsterdam CcJF ChimieNetherlands Centre de Recherches Nord

62160 Bul 1 y-Les—Mi nesFrance


Dr. 3. MeissnerEi dgenoessi scheTechnische Hochschule ZurichTechni sches Laboratori urnUniversitatstrasse 6CH — 8006 Zurich Switzerland

Dr. M. FleissnerHoechst AGKunststoff Forschung HPostfach 80 03 20D — 6230 Frankfurt am Main 80Germany

Dr. D.J. GrovesICI Petrochemicals and Plastics DivisionWilton CentreP.O. Box No. 90WiltonMi ddl esbroughClevelandUnited Kingdom

Dr. L.A. UtrackiNational Research Council CanadaIndustrial Materials Research Institute75, Soul De MortagneBouchervi 1 1 euebecCanada

Mr. A. GhijselsKoninklijke/Shell LaboratoriumPostbus 3003Badhuisweg 3Amsterdam — NNetherlands

Acknowledgements

Dr. J.M. StaritaRheometrics, Inc.I Possumkown RoadPi scatawayNew Jersey 08854USA

Dr. FrankRheometrics GmbHArabella CenterLyoner Strasse 44—48D6000 Frankfurt aM. 71West Germany

Dr. G. AjroldiMontepolimeri SpACentre Richerche BollateVia S. Pietro, 50I — 20021 BollateItaly

Pr. J.L. WhiteDr. H. VamanePolymer Engineering CenterThe University of AkronAkron, Ohio 44325USA

Pr. H.H. WinterDept. of Chemical EngineeringUniversity of MassachusettsAmherst, Mass. 01003USA

Research at the University of Akron was supported by the Division of Engineering of theNational Science Foundation. The authors also wish to thank the efforts of Mr. Ho JongKang of the University of Akron.

REFERENCES

J. Meissner, Pure Appl. Chem. 42, 553 (1975).H.H. Winter, Pure Appl. Chem. 55, 943 (1983).Y. Ide and J.L. White, J. Appl. Polym. Sci. 20, 2511 (1976).Y. Ide and J.L. White, J. Appl. Polym. Sci. 22, 1061 (1978).W. Minoshima, J.L. White and J.E. Spruiell, Polym. Eng. Sci.20, 1166 (1980).H.I. Freeman and N.J. Coplan, J. Appl. Polym. Sci. 8, 2389 (1964).S. Kase, T. Matsuo and Y. Yoshimoto, Seni Kikai Gakkaishi 19, 763 (1966).A. Bergonzoni and A.J. DiCresci Polyn. Eng. Sci. 6, 45 (1966).S. Kase, J. Appl. Polym. Sci. 18, 3279 (1974).A. Ghijsels and J.J.S. Ente, Rheology Vol. 3, Edited by G. Astarita, G. Narrucci andL. Nicolais, Plenum, NY (1980).W. Minoshinia, J.L. White and J.E. Spruiell, J. Appl. Polym. Sci. 25, 287 (1980).H. Yamane and J.L. Vhite, Polym. Eng. Sci. 23, 516 (1983).

W. Minoshiina, Ph.D. Dissertation in Polymer Engineering University of Tennessee,Knoxville (1983). Also W. Minoshima and J.L. White, J.Nom. Newt. Fluid Mech.19, 275 (1986).

1.

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11.

12.

13.


14. C.D. Han and J.Y. Park, J. Appl. Polym. Sci. 19, 3291 (1975).15. C.D. Han and R. Shetty, IEC Fund 16, 49 (1977).16. T. Kanai and J.L. White, Polym. Eng. Sc 24, 1185 (1984).17. R.S. Spencer and R.E. Dillon, J. ColloidSci. 4, 241 (1949).18. J.P. Tordella, J. Appl. Phys. 27, 454 (1956).19. J.P. Tordella, Rheol. Acta 1, 216 (1958).20. P.L. Clegg, Trans. Plastics Inst. 28, 245 (1960).21. E.B. Bagley and H.P. Schreiber, Trans Soc. Rheology 5, 341 (1961).22. E.R. Howells and J.J. Benbow, Trans Plast. Inst. 30, 242 (1962).23. J.P. Tordella, J. Appl. Polyn. Sci. 7, 215 (1963).24. H.N. Laun and H. Munstedt, Rheol. Acta 17, 415 (1978).25. H. Yamane and J.L. White, Polym. Eng. Rev. 2, 167 (1982).26. F.N. Cogswell, Polyn. Eng. Sci. 12, 64 (1972).27. T.G. Fox, S. Gratch and E. Loshaek in "Rheology" Vol. 1, Edited by F.R. Eirich, Academic

Press, NY (1956).28. G.V. Vinogradov and A.Y. Nalkin "Rheology of Polymers" Mir, Noscow (1980).29. C.D. Han and T.C. Yu, Rheol. Acta 10, 398. (1971).30. K. Oda, J.L. White and E.S. Clark, Polym. Eng. Sci. 18, 25 (1978).31. B.D. Coleman and H. Narkovitz, J. Appl. Phys. 35, 1 (1964).32. W.P. Cox and E.H. Merz, J. Polym. Sci. 28, 619 (1958).33. J.L. White and H. Yamane, Pure Appl. Chem. 57, 1441 (1985).

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