CA1059278A - High modulus polyethylene - Google Patents

High modulus polyethylene

Info

Publication number
CA1059278A
CA1059278A CA193,478A CA193478A CA1059278A CA 1059278 A CA1059278 A CA 1059278A CA 193478 A CA193478 A CA 193478A CA 1059278 A CA1059278 A CA 1059278A
Authority
CA
Canada
Prior art keywords
molecular weight
average molecular
process according
polymer
polymer material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA193,478A
Other languages
French (fr)
Other versions
CA193478S (en
Inventor
Ian M. Ward
Giancarlo Capaccio
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Research Development Corp UK
Original Assignee
National Research Development Corp UK
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by National Research Development Corp UK filed Critical National Research Development Corp UK
Application granted granted Critical
Publication of CA1059278A publication Critical patent/CA1059278A/en
Expired legal-status Critical Current

Links

Classifications

    • DTEXTILES; PAPER
    • D01NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01FCHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/02Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F6/04Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyolefins
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04Polymers of ethylene
    • B29K2023/06PE, i.e. polyethylene

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Artificial Filaments (AREA)
  • Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)
  • Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

An oriented high density polyethylene polymer material having a weight average molecular weight of less than 200,000, a number average molecular weight of less than 20,000, a ratio of weight average molecular weight ?w to number average molecular weight ?n such that for Mn>104, and for ?n?104, , and a Young's modulus greater than 3 x 1010N/m2. The disclosure also includes a process of heat treating a shaped ethylene polymer which is subsequently cooled and drawn.

Description

This invention relates to certain new polymer materials and a process for thqi~r production.
There is a continuing demand for engineering materials having an improved combination of physical properties and, for example, a great deal of attention has recently centred around carbon fibres. Carbon fibres have a very high modulus of elasticity (4.2 x 10 ~/m ) but are very expensive and thus of limited application. Fibres formed from polymers such as polyethylene by conventional methods are cheaper but have a greatly inferior modulus of elasticity (about 0.5 - 0.7 x 10 NJm ).
The present invention provides a new polymer material having improved physical properties in this respect, and a process for its production.
According to the present invention there is provided an oriented high density polyethyl~ne polymer material having a weight average molecular weight of less than 200,000 a number average molecular ~
weight of less than 20,000 a ratio of weight average molecular ;
weight M to number average molecular weight M such that for M > 10 ~ - < lOand for M ~ 10 ~ - <20~ and a Young's modulus as hereinaf~er defined greater than 3 x 10 N/m .
In another aspect the invention provides a process for the production of a polyethylene polymer material which comprises subjecting a high density polyethylene polymer having a weight average molecular weight of less than 200,000 a number average molecular weight of less than 20,000 and a ratio of weight average ;' .
2 ; `

~' .. . . .

lOS9Z78 molecular weight M to number average molecular weight M such that for M > 10 ~ 0 and for M ~10 ~ --<20 to a thermal treatment in which it is cooled from a temperature at or close to its melting point and at a rate of from 1 to 15 C per minute to a temperature 5 at least 15 C below its melting point, and drawing the polymer at a temperature and a rate such that the deformation ratio is at least 15.
In this specification high density polyethylene means a substantially linear homopolymer of ethylene or a copolymer of ethylene containing at least 95% by weight of bthylene having a density of 10 from 0.85 to 1.0 gms/cm3 as measured by the method of British Standard Specification No. 2782 (1970) method 509B on a sample prepared according to British Standard Specification No. 3412 (1966) Appendix A
and annealed according to British Standard Specification No. 3412 (1966) Appendix B (1)~ such as for example that produced by polymerising 15 ethylene in the presence of a transition metal catalyst.
Preferably the polymer is allowed to cool at a rate of from 2 to 10 C pe~ minute to a temperature of from 100 to 120 C after which it will usually be quenched i.e. rapidly cooled, to a low temperature. In a continuous process it may be possible to omit 20 the quenching step and draw the polymer directly after controlled cooling.
Preferably the polymer has a weight average (M ) molecular weight of from 50,000 to 150,000. The number average (M ) molecular weight is preferably from 5,000 to 15,000. Preferably 25 the ratio of weight average molecular weight to number average molecular weight is less than lô. Particularly good results have ~05~3Z7~3 been obtained using polymers having a relatively narrow molecular weight distribution, such that for M > 10 t - <6 and for M ~10 - ~ 5. The mole~ular weights quoted in this specification are those measured by the gel permeation chromatography method.
Although the invention is not limited to any particular theory ~ sh~.~A
it is believed that by subjecting th~ polymer having the desired morphology, to a plastic deformation processt a very high degree of orientation of the polymer molecules i9 obtained. A particularly preferred plastic deformation process comprises drawing the polymer to a draw ratio of at least 15, and preferably at least 20. The polymer must of course be drawn at a speed and at a temperature such that the tension of drawing is less than the tensile strength of the polymer but sufficient to produce the required orientation by extension of the polymer material over and above any extension which may be produced by flow drawing. Preferably the draw temperature is at least 40 C below the melting point of the polymer. The draw speed is related to the draw temperature and the morphology of the polymer but is usually in excess of 1 cm. per minute and may for example, be from 10 to 20 cm. per minute, or even higher.
Preferably the draw temperature is from 60 to 90 C and the draw ratio is at least 18, and preferably from 25 to 60.
It has been found that the physical properties of the polymer material can sometimes be further improved by carrying out the drawing process in incremental stages, allowing the polymer to rest between successive stages.

,. . . . ' .: ,; , ;

` ' ' ~ ' ~ -, - , ~' ,: ` . :

~05~'71~
v~ ~eQ~ h It is preferred to carry out the drawing proce~s upon ~polymer havin~ a relatively small cross-section and the invention i8 particularly suitable for the production of fibres and filns. In particular continuous filament~ may be produced by melt spinning and drawing on a draw frame. For convenience the diameter of the fibre, or the thickness of the film, before drawing is preferably less than 1 mm.
In this specification the deformation ratio or draw ratio is defined either as the ratio of the final length to the initial length or as the ratio of the cross-sectionalareas before and after drawing.
The process of the invention is capable of producing a polymer material having a Young's modulus as hereinaft`er defined well in excess of 3 x 10 N/m and in some case~ at least 6 x 10 ON/m . The Young's modulus of a polymer material depends partly upon the method of measurement, and therefore in thi# specification Young's modulus is defined as being the modulus measured at 21 C by a dead-loading creep experiment, as described by Gupta & Ward in J. Macromo. Sci.
Phys. Bl 373 (1967)~ taking the 10 second response at a strain of 0.1%.
It i9 found that, in accordance with the process of the invention, substantially complete alignment of the polymer molecules can be obtained by plastic deformation. The molecular orientation will in most cases be uniaxial, although it is also possible with an appropriate drawing process, to produce biaxially oriented polymer materials. The presence of substantially complete orientation may be determined by physical measurements, such as for example, X-ray diffraction measurements, or nuclear magnetic resonances studies.
A simple test comprises measuring the weight loss of the polymer in ~)5~Z7~3 fuming nitric acid and this is a measure of the perf~ction of the polymer material. A low weight loss indicates a high degree of perfection.
The new polyethylene polymer materials~of the present invention have a highly oriented structure as can be observed by X-ray diffraction and N.M.R. studies. In particular samples with a modulus above 5 x 10 N/m have a weight loss in fuming nitric acid of less than 5% after 10 days at 60 C.
A theoretical estimate for the Young's modulus of polyethylene is 24 x 10 N/m and it can thus be seen that the polymer materials of the invention have a modulus which approaches quite closely to this figure. Polyethylene polymer materialY having a Young's modulus in excess of 4 x 10 N/m and o M en in the range 5 x 7 x 10 N/~ may be obtained by the process of the lnvention.
Polyethylene polymer materials according to the pre~ent invention can be produced in the form of coherent unitary structures.
m ey are tough and not brittle, for example polyethylene fibres may be produced which have an extensibility of at least 7%~ and which can be fibrillated.
The invention is illustrated by the following Examples:
EXAMPL~ 1 Isotropic filaments of 0. o6 - o. 07 cm diameter are obtained by melt spinning at 190 C through a 0.1 dm diameter die. The filaments are wound up on a cylinder of 5.5 cm diameter rotating at a speed of 2.3 revs/min. The cooling rate of the polymer is arranged to be 5 C
per minute and the structure produced when the temperature of the .. . .
- - - ~ ~ . . . .

.

-~OS'3'~78 polymer rcaches il5 C is prosclvc(1 by rlpld coo1ing. Samples 3 l~ cm long are subsequ~ ly drliwn on an Instron t~ns;le testing machine at 72 c wi th a cross-head speed of 20 cm/min for 3o 1~5 secs. The draw ratio ;.s deterinined from the variation in cross-section of the filament.
This process is undertaken with two polymers from the commercial range of BP high density polycthylene; 07s-60 grade with a melt flow index of 8.o measured at 190 C with a load of 2.14 kg~ M of 1~ 450, and M of 69100, and for comparison, Rigidex 9, with a rnelt flow index of 0. 9, M of 6060 and M of 126600. The 10 sec Young~s modulus is measured at room +emperature (21 c). The 07s-60 grade had a narrow molecular weight distribution, - = 4.8, and gives a drawn product having a draw ratio of 20 and a Young's modulus of 4.0 x 10 N/m .
In contrast, the Rigidex 9 ~as a broader molecular weight M
distribution, - ~ 20.9 as well as a higher M value, and consequently gives a drawn product having a considerably lower modulus. Continuous -~
filaments of the above materials may be drawn on a draw frame with similar results.

0.05-0.07 cm thick sheets are obtained by compression moulding high density polyethylene pellets at 160 c between two copper plates.
These sheets are then removed from the press and slowly cooled at a rate of 7-9 C/min to a temperature of 100 C (measured on the surface of the copper plate) and then quenched in cold water. Xectangular samples 2 cm long and 0.5 cm wide are drawn on an Instron tensile testing machine at 75 c at a cross-head speed of 10 cm/min for * Trademark ~.

-~05~3Z78 70-90 secs. 'I`he draw rat;o is mcasured frorn marks on the surface of the un(]rawn sa~ )les spaccd at ;ntervals of O.Z or 0.1 cm.
The polymc!rs invost;gatcd are two different grades from the commercial Innge of Bl~liyh densi-ty polyethylenc~ Qigi(lex 50~ with a me]t flow indcx of 5.5 M of 6180 and M of 101450, and 1ll0-60 grade with a melt flow index of 12~ M of 13350 and M of 67800.
A maximum draw ratio of 30 is measured for the Rigidex 50~ and a maximum draw ratio of 37-38 for the 140-60 grade.
The 10 sec Youn~3's modulus for representative samples is 10 measured at room temperature and the results given in the following Table.
TABLE

Mater;alsMelt Flow Draw Ratio 10 sec Young's modulus Index (N/mZ x 10 ~9 strain 0.1 x 10-2 after thermal treatment and drawing : -Room ternperature *
Rigidex 50 5.5 27 5-7 ~ " 30 6.8 140-60 12.0 28 5~7 ~ --- : :

* Trademark ,,~' -

Claims (21)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. An oriented shaped high density polyethylene polymer material having a weight average molecular weight of less than 200,000, a number average molecular weight of less than 20,000, a ratio of weight average molecular weight ?w to number average molecular weight ?n such that for ?n>104, and for ?n?104, , and a Young's modulus greater than 3 x 1010N/m2.
2. A polyethylene polymer material according to Claim 1, having a weight average molecular weight of from 50,000 to 150,000.
3. A polyethylene polymer material according to Claim 2, having a number average molecular weight of from 5,000 to 15,000.
4. A polyethylene polymer material according to Claims 1, 2 or 3 having a molecular weight distribution such that for ?n>104, , and for ?n<104, .
5. A polyethylene polymer material according to Claims 1, 2 or 3 having a weight loss in fuming nitric acid of less than 5%
after 10 days at 60°C.
6. A polyethylene polymer material according to Claims 1, 2 or 3 that is unaxially oriented.
7. A polyethylene polymer material according to Claims 1, 2 or 3 that is a fibre or a film.
8. A polyethylene polymer material according to Claims 1, 2 or 3 that is a continuous filament.
9.A process for the production of a polyethylene polymer material which comprises subjecting a shaped high density polyethylene polymer having a weight average molecular weight of less than 200,000 a number average molecular weight of less than 20,000, and a ratio of weight average molecular weight ?w to number average molecular weight ?n such that for ?n>104, and for ?n?104, to a heat treatment from which it is cooled from a temperature at or close to its melting point and at a rate of from 1° to 15° per minute to a temperature at least 15°C. below its melting point and drawing the polymer at a temperature and a rate such that the deformation ratio is at least 15.
10. A process according to Claim 9 in which the polymer is allowed to cool at a rate of from 2° to 10°C. per minute to a temperature of from 100° to 120°C.
11. A process according to Claim 10 in which the polymer after the heat treatment is quenched.
12. A process according to Claims 9, 10 or 11 in which the polymer has a weight average molecular weight of from 50,000 to 150,000.
13. A process according to Claims 9, 10 or 11 in which the polymer has a number average molecular weight of from 5,000 to 15,000.
14. A process according to Claims 9, 10 or 11 in which the polymer has a molecular weight distribution such that for ?n>104, and for ?n<104, .
15. A process according to Claim 9, 10 or 11 which comprises drawing the polymer to a deformation ratio of at least 20.
16. A process according to Claim 9, 10 or 11, in which the draw temperature is at least 40°C. below the melting point of the polymer.
17. A process according to Claim 9, 10 or 11 in which the draw speed is in excess of 1 cm. per minute.
18. A process according to Claim 9, 10 or 11, in which the draw temperature is from 60° to 90°C. and the draw ratio is from 25 to 60.
19. A process according to Claim 9, 10, or 11 in which the polymer is a fibre or a film, the diameter of the fibre or the thickness of the film before drawing being less than 1 mm.
20. A process according to Claim 9, 10 or 11 in which the continuous filament is produced by melt spinning and drawing on a draw frame.
21. A polyethylene polymer material according to Claims 1, 2, or 3 having a Young's modulus in the range of from 5 to 7 x 1010N/m2.
CA193,478A 1973-03-06 1974-02-26 High modulus polyethylene Expired CA1059278A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1074673A GB1469526A (en) 1973-03-06 1973-03-06 Polymer materials

Publications (1)

Publication Number Publication Date
CA1059278A true CA1059278A (en) 1979-07-31

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ID=9973530

Family Applications (1)

Application Number Title Priority Date Filing Date
CA193,478A Expired CA1059278A (en) 1973-03-06 1974-02-26 High modulus polyethylene

Country Status (13)

Country Link
JP (2) JPS5746414B2 (en)
BE (1) BE811853A (en)
CA (1) CA1059278A (en)
CS (1) CS181752B2 (en)
DE (1) DE2410747C2 (en)
ES (1) ES423956A1 (en)
FR (1) FR2220547B1 (en)
GB (1) GB1469526A (en)
IE (1) IE39164B1 (en)
IT (1) IT1013059B (en)
LU (1) LU69546A1 (en)
NL (1) NL184696B (en)
ZA (1) ZA741145B (en)

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1506565A (en) * 1974-03-05 1978-04-05 Nat Res Dev Production of polyethylene filaments
GB1568964A (en) * 1975-11-05 1980-06-11 Nat Res Dev Oriented polymer materials
NL177759B (en) * 1979-06-27 1985-06-17 Stamicarbon METHOD OF MANUFACTURING A POLYTHYTHREAD, AND POLYTHYTHREAD THEREFORE OBTAINED
JPS5752403A (en) * 1980-09-11 1982-03-27 Kyoto Prefecture Production of fan stick
NL8104728A (en) * 1981-10-17 1983-05-16 Stamicarbon METHOD FOR MANUFACTURING POLYETHENE FILAMENTS WITH GREAT TENSILE STRENGTH
JPS59133418U (en) * 1983-02-28 1984-09-06 本州製紙株式会社 injection molded composite container
JPS59167649U (en) * 1983-05-04 1984-11-09 京都府 Fan rib manufacturing equipment
GB8404843D0 (en) * 1984-02-24 1984-03-28 Amersham Int Plc Free analyte assay
JPS61121867A (en) * 1984-11-20 1986-06-09 Masakatsu Hoshino Polishing method for both side surfaces of metal foreign-style tableware
JPH074752B2 (en) * 1987-01-29 1995-01-25 三菱重工業株式会社 6-axis control automatic polishing machine
JPH0777755B2 (en) * 1987-09-16 1995-08-23 昭和電工株式会社 Polyethylene film
US4882230A (en) * 1987-10-30 1989-11-21 Kimberly-Clark Corporation Multilayer polymeric film having dead bend characteristics
JPH0577855U (en) * 1992-03-23 1993-10-22 株式会社トータス Positioning of the circuit board to the leg of the image quality compensator Temporary fixing structure
US5549867A (en) * 1994-11-03 1996-08-27 Fiberweb North America, Inc. Distribution enhanced polyolefin meltspinning process and product
GB0128405D0 (en) * 2001-11-27 2002-01-16 Btg Int Ltd Process for fabricating polyolefin sheet

Also Published As

Publication number Publication date
JPS59192534A (en) 1984-10-31
FR2220547B1 (en) 1978-01-06
DE2410747A1 (en) 1974-09-12
IE39164B1 (en) 1978-08-16
IE39164L (en) 1974-09-06
GB1469526A (en) 1977-04-06
JPS5025679A (en) 1975-03-18
ES423956A1 (en) 1976-11-01
JPS5746414B2 (en) 1982-10-02
NL184696B (en) 1989-05-01
DE2410747C2 (en) 1983-02-10
NL7402956A (en) 1974-09-10
JPS6216813B2 (en) 1987-04-14
CS181752B2 (en) 1978-03-31
ZA741145B (en) 1975-01-29
BE811853A (en) 1974-09-04
LU69546A1 (en) 1974-06-21
IT1013059B (en) 1977-03-30
FR2220547A1 (en) 1974-10-04
AU6593674A (en) 1975-08-28

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