WO1998046696A1 - High magnetic field processing of liquid crystalline polymers - Google Patents
High magnetic field processing of liquid crystalline polymers Download PDFInfo
- Publication number
- WO1998046696A1 WO1998046696A1 PCT/US1997/002968 US9702968W WO9846696A1 WO 1998046696 A1 WO1998046696 A1 WO 1998046696A1 US 9702968 W US9702968 W US 9702968W WO 9846696 A1 WO9846696 A1 WO 9846696A1
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- WIPO (PCT)
- Prior art keywords
- liquid crystalline
- magnetic field
- orientation
- field
- article
- Prior art date
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Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
- C08G59/20—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the epoxy compounds used
- C08G59/22—Di-epoxy compounds
- C08G59/24—Di-epoxy compounds carbocyclic
- C08G59/245—Di-epoxy compounds carbocyclic aromatic
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
- C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
- C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
- C08G59/44—Amides
- C08G59/444—Sulfonamides
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2300/00—Characterised by the use of unspecified polymers
- C08J2300/12—Polymers characterised by physical features, e.g. anisotropy, viscosity or electrical conductivity
Definitions
- the present invention relates to high magnetic field processing of liquid crystalline polymers and the resultant products from such processing, i.e., liquid crystalline polymers having improved mechanical properties.
- This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).
- Liquid crystalline thermosets have become recognized over the past few years as an important new class of materials. Numerous reports have described their synthesis and phase behavior. In particular, important effects due to the orientation of the rodlike molecules in a liquid crystalline phase have been described. It has been found that curing rates are enhanced compared to reaction in an isotropic phase, and that the glass transition of the fully cured material can be significantly higher than the final cure temperature.
- orientation of LCT's promotes the maximization of mechanical properties.
- a few studies have described use of magnetic fields to orient LCT's.
- the maximum reported field strength was 13.5 T and the polymer placed in the field was typically contained in microcapillary-type tubes such that the polymer was essentially a microfiber in physical dimensions, and no measurements were made of the resultant tensile properties.
- a desired tensile modulus can be selected for a particular application but can exceed 5 X 10 5 pounds per square inch, preferably 8 X 10 5 pounds per square inch, and more preferably 1 X 10 6 pounds per square inch.
- the resultant products can typically be characterized by tensile modulus properties exceeding 5 X 10 5 pounds per square inch, preferably 8 X 10 5 pounds per square inch, and more preferably 1 X 10 6 pounds per square inch.
- the present invention provides a bulk article of a liquid crystalline thermoset material, said material processed in a high strength magnetic field whereby said material is characterized as having an enhanced tensile modulus parallel to orientation of said field of greater than about 25 percent, preferably 50 percent, and more preferably 100 percent over non-magnetically processed material.
- the present invention further provides a process of forming bulk articles of oriented liquid crystalline thermoset materials, said materials characterized as having an enhanced tensile modulus parallel to orientation of said field of greater than about 25 percent, preferably 50 percent, and more preferably 100 percent over non-magnetically processed material comprising curing a liquid crystalline thermoset precursor within a high strength magnetic field of greater than about 2 Tesla.
- the present invention is concerned with orientation of LCT's in field strengths from about 2 Tesla (T) up to 10 to 20 T or more.
- the resultant oriented LCT product can show enhancement of properties such as improved tensile modulus of greater than about 25 percent compared to those for unoriented LCT's, preferably greater than about 50 percent and more preferably greater than about 100 percent.
- the present invention is further concerned with shaped articles or bulk articles of the magnetically processed LCT's.
- bulk article is meant an article having dimensions of generally at least about 0.125 inches in each direction, i.e., height, width and depth (x, y, and z), and more preferably having at least one dimension in excess of about one inch.
- Such a bulk article can be shaped in a suitable mold to yield a shaped article or machined.
- Orientation of the LCT material processed in accordance with the present invention is found throughout the entirety of the bulk article and not limited to orientation on only the surface of the material.
- the present invention involves variable control of LCT processing such that a desired bulk article with targeted tensile modulus properties can be achieved by control of variables such as, e.g., the strength of the magnetic field, B-staging of the polymer and the length thereof, the amount of time of the magnetic processing, the temperature during processing, and selection of the catalyst for the LCT.
- the LCT can generally be of any chemical structure. Numerous LCT's are known to those of skill in the art. For example, an exemplary LCT is the diglycidyl ether of dihydroxy-alpha-methylstilbene (DGE-DHAMS) cured with the diamine, sulfanilamide (SAA). Structures for these materials are shown by the structures:
- LCT diglycidyl ether of dihydroxy biphenyl
- DGE-biphenyl dihydroxy biphenyl
- Other suitable LCT's can include materials such as those described in U.S. Patent Nos. 5,114,612; 5,198,551; 5,475,133; 5,266,660; 5,266,661; 5,270,404; 5,270,405; 5,270,406; and, 5,292,831. Mixtures of different LCT's may also be employed as may mixtures of LCT's and liquid crystalline polymers (LCP's) such as Vectra® polyester, Kevlar® aromatic polyamide, and Xydar® polyester. Also, mixtures or combinations of polymer materials including at least one LCT may be employed.
- LCP's liquid crystalline polymers
- the magnetic fields for processing the LCT's are high strength magnetic fields, i.e., fields generally greater than about 2 Tesla, preferably greater than about 6 Tesla, and more preferably from about 10 to 20 Tesla or greater.
- the present invention is more particularly described in the following examples which are intended as illustrative only, since numerous modifications and variations will be apparent to those skilled in the art.
- EXAMPLE 1 Thermosets were cured at field strengths of up to 18 Tesla to evaluate the effects of very high magnetic fields on the properties of the system.
- thermoset formulation was prepared by dissolving 1 equivalent of SAA and 2 milliequivalents of an organophosphonium catalyst into 1 equivalent of DGE-DHAMS at elevated temperatures. This mixture was then poured into a mold for the magnetic field experiments. This mold consisted of a Teflon cup onto which was placed two aluminum heater blocks, with the thermoset formulation filling the space between the blocks. Temperature control was maintained with a PID controller. Magnetic field experiments were conducted at the National High Magnetic Field Laboratory using a 20 T variable field electromagnet. Curing was done in the field for 1 hr at 150 ° C. The sample was then removed from the mold by cutting the Teflon cup and separating the aluminum plates. The final cure was done in a conventional oven, and consisted of an additional 3 hrs at 150 * C, 1 hr at 175 * C, and 4 hrs at 200 " C. Plaques approximately 2 inches by 1.5 inches by 0.125 inches were obtained.
- Thermal Expansion Thermal expansion measurements were performed parallel and perpendicular to the field direction using an Omnitherm TMA 1000 with a heating rate of 5 * C/minute and a mass of 10 grams. Values of the coefficient of thermal expansion (CTE) reported are calculated by linear extrapolation of the displacement-temperature curve over the temperature range 30 to 60 ° C.
- Tensile Properties Tensile properties were measured on ASTM Type V specimens using an Instron 4483 testing machine and an MTS 632.26E extensometer. The results for this example are the average of at least three different runs of sample for each field strength.
- X-ray Diffraction X-ray diffraction was performed using a rotating anode generator and a two dimensional position sensitive detector. Calculation of the orientation parameter was done using the equation
- the DGE-DHAMS/SAA system which is initially isotropic, forms a smectic phase upon curing at 150 ° C.
- the formation of the smectic phase is due to an increase in aspect ratio of the rodlike molecules as the reaction proceeds.
- the smectic phase forms after approximately 20 minutes of cure, and the gel point is reached in approximately 45 minutes. Curing in the magnetic field was done for 1 hour in order to ensure that any orientation induced by the field was locked into the network structure.
- Tensile properties of the final cured LCT at 0, 15, 18 T are shown in Table 1.
- the tensile properties of the macroscopically unoriented material are similar to those obtained with epoxies based on bisphenol-A cured under the same conditions.
- the unique advantages of the liquid crystalline epoxy are realized when the material is oriented in magnetic fields. Particularly noteworthy is the increase in tensile modulus. Orientation in magnetic fields leads to an increase of almost three times the modulus compared to the unoriented material. The strain at break is also significantly affected by the chain orientation. While not wishing to be bound by the present explanation, it is believed that the reduction in strain at break and the increase in the modulus are due to the decreased elasticity of chemical bonds in the direction of orientation as a result of the magnetic field, as compared to segment reorientation which dominates the stress-strain behavior in an unoriented sample. The oriented product is strengthened by locking into a more perfect or ordered grid.
- orientation parameter was determined by integrating the scattered intensity around the azimuthal angle ⁇ at a given value of the scattering angle 2 ⁇ according to the equations given above.
- the orientation parameters calculated are 0.93 and 0.90 for 15 and 18 T, respectively, where a value of 1.0 indicates complete orientation. These two values are the same within experimental error.
- X-ray results confirm that the molecular axes and the smectic layer normals are aligned parallel to the field direction.
- the present invention describes preliminary results on magnetic field processing of liquid crystalline thermosets.
- EXAMPLE 2 The following materials were used: digylcidyl ether of dihydroxy-alpha-methyl stilbene (DHAMS), sulfanilamide (SAA), various organophosphonium catalysts, and a non-liquid crystalline material, i.e., diglycidyl ether of bisphenol-A (DER 332).
- DHAMS dihydroxy-alpha-methyl stilbene
- SAA sulfanilamide
- DER 332 various organophosphonium catalysts
- DER 332 diglycidyl ether of bisphenol-A
- the various materials were formulated and placed into the mold described in Example 1.
- the molds were placed into the high strength magnetic fields and respective samples cured for various periods of time of five minutes, thirty minutes and fifty-five minutes. Some samples were subjected to B-staging for forty-five minutes or ninety minutes prior to Physical properties of the resultant shaped articles from the cured molds were measured including measurement of tensile modulus parallel to the field in kilopounds per square inch, tensile modulus perpendicular to the field in kilopounds per square inch, thermal expansion coefficient in microns per meter per °C for both parallel and perpendicular to the direction of the field, and an x-ray order parameter as determined by wide angle x-ray scattering with -0.5 indicating the molecules were completely aligned perpendicular to the field, 0.0 indicating that the molecules were arranged randomly, and 1.0 indicating that the molecules were aligned completely parallel to the field.
- Table 4 show that tensile modulus can be increased up to about three times that of the same material processed in the absence of a magnetic field (tensile modulus was shown in Table 1 to be about 443 kpsi for no magnetic field processing.
- Table 5 shows that tensile modulus can be increased up to about three times that of the same material processed in the absence of a magnetic field (tensile modulus was shown in Table 1 to be about 443 kpsi for no magnetic field processing.
- the results of Table 5 demonstrate that transverse modulus was not affected in the magnetic processing; yet the tensile modulus is dramatically increased. Further, the results show that catalyst can be a factor in reaching a desired product. Catalyst 2 is a faster catalyst than catalyst 1 thereby promoting faster reaction of the LCT. Such a faster catalyst may not allow sufficient time for orientation of the LCT material in the magnetic field. Also, the results show that purity of the liquid crystalline precursor material can affect the resultant properties as well. Finally, the results show that a non-liquid crystalline polymer material remains essentially unaffected by processing in the magnetic field, atleast with respect to tensile modulus properties.
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
Abstract
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Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1997/002968 WO1998046696A1 (en) | 1997-04-14 | 1997-04-14 | High magnetic field processing of liquid crystalline polymers |
AU45810/97A AU4581097A (en) | 1997-04-14 | 1997-04-14 | High magnetic field processing of liquid crystalline polymers |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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PCT/US1997/002968 WO1998046696A1 (en) | 1997-04-14 | 1997-04-14 | High magnetic field processing of liquid crystalline polymers |
Publications (1)
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WO1998046696A1 true WO1998046696A1 (en) | 1998-10-22 |
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Family Applications (1)
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PCT/US1997/002968 WO1998046696A1 (en) | 1997-04-14 | 1997-04-14 | High magnetic field processing of liquid crystalline polymers |
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AU (1) | AU4581097A (en) |
WO (1) | WO1998046696A1 (en) |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4808149A (en) * | 1982-04-12 | 1989-02-28 | Dayco Products, Inc. | Endless power transmission belt construction and method and apparatus for making the same |
-
1997
- 1997-04-14 WO PCT/US1997/002968 patent/WO1998046696A1/en active Application Filing
- 1997-04-14 AU AU45810/97A patent/AU4581097A/en not_active Abandoned
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4808149A (en) * | 1982-04-12 | 1989-02-28 | Dayco Products, Inc. | Endless power transmission belt construction and method and apparatus for making the same |
Non-Patent Citations (1)
Title |
---|
OBER C.K. et al., "Liquid Crystalline Thermosets as Materials for Microelectronics", MAT. RES. SOC. SYMP. PROC., Vol. 227, (1991), pages 281-292. * |
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AU4581097A (en) | 1998-11-11 |
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