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EP1268185A1 - Nanocomposites polymeres/inorganiques haute temperature - Google Patents

Nanocomposites polymeres/inorganiques haute temperature

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Publication number
EP1268185A1
EP1268185A1 EP00919564A EP00919564A EP1268185A1 EP 1268185 A1 EP1268185 A1 EP 1268185A1 EP 00919564 A EP00919564 A EP 00919564A EP 00919564 A EP00919564 A EP 00919564A EP 1268185 A1 EP1268185 A1 EP 1268185A1
Authority
EP
European Patent Office
Prior art keywords
nanocomposites
organic
phosphonium
inorganic
layers
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.)
Withdrawn
Application number
EP00919564A
Other languages
German (de)
English (en)
Other versions
EP1268185A4 (fr
Inventor
Anant Singh
Ross Haghighat
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.)
Triton Systems Inc
Original Assignee
Triton Systems Inc
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 Triton Systems Inc filed Critical Triton Systems Inc
Priority claimed from PCT/US2000/007708 external-priority patent/WO2001070492A1/fr
Publication of EP1268185A1 publication Critical patent/EP1268185A1/fr
Publication of EP1268185A4 publication Critical patent/EP1268185A4/fr
Withdrawn legal-status Critical Current

Links

Definitions

  • a nanocomposite is defined as an interacting mixture of two phases, one of which is in the nanometer size range in at least one dimension. Due to the nanoscale dimensions of the reinforcement phase, nanocomposites display unique and improved properties compared to that of micro- or macro- composites. A wealth of unique properties and technological opportunities are offered by these materials. Hence, over the last few years, nanocomposite materials have become an integral part of the synthesis of new materials for a wide variety of applications including mechanical, optical, magnetic and dielectric applications.
  • Polymer/inorganic nanocomposites have attracted much attention as the properties of polymers are further enhanced beyond what is achievable from more conventional particulate- filled or micro-composites.
  • layered mica-type- silicates have been widely used as inorganic reinforcements for polymer matrices to create polymer nanocomposites with nanoscale dispersion of the inorganic phase within the polymer matrix.
  • Layered silicate-polymer nanocomposites having (i) polymer chains intercalated between the silicate layers or (ii) individual silicate layers delaminated and dispersed in a continuous polymer matrix, have been fabricated.
  • the invention provides new high-use temperature, lightweight polymer/inorganic nanocomposite materials with enhanced thermal stability and performance characteristics.
  • the invention provides two techniques that enhance the thermal stability of the nanocomposite systems from their current limits of 100 - 150 °C to over 250 °C.
  • the two unique approaches are based on innovative chemical design of the organic-inorganic interface using (i) more thermally stable surfactants/compatibility agents, and (ii) more thermally stable synthetic organically-modified layered- silicate reinforcements to create unique nanocomposites. These approaches offer processibility through both solution techniques, as well as solvent-free direct melt intercalation technique.
  • nanocomposites are optimized in order to manufacture these materials in commercially applicable forms, e.g. films, fibers and molded components.
  • the new technology provides hitherto unobtainable thermal stability and performance characteristics, and has numerous applications in automotive, aerospace, electronic and food and beverage industries.
  • Figure 1 shows high temperature, high performance organic/inorganic nanocomposites.
  • Figure 2 shows a chemical structure of the preferred tetraphenyl phosphonium surfactant.
  • Figure 3 shows a schematic of polymer-layered silicate nanocomposite structures.
  • Figure 4 provides a table of the properties of nylon-6 and layered silicate-nylon nanocomposites.
  • Nanocomposites 1 have silicate layers 3 with alkyl ammonium surfactants 5 on the surface.
  • the first part of the invention schematically shown in Figure IB, provides new organic/inorganic nanocomposite structures 11 by substituting high temperature organic phosphonium cations 15 for the standard compatibilizing agent, viz., alkyl ammonium cations.
  • ion exchange occurs with the more thermally stable organic phosphonium cations, e.g. tetraphenyl phosphonium 15 ( Figure 2) . That modification enhances the thermal stability of the nanocomposites from the current level of about 100-150 'C to approximately 175-200 'C or more without affecting other physical or mechanical properties of the resulting nanocomposites.
  • the inventors have synthesized a new class of phenyl phosphine-based arylene ether structural polymers that offer excellent mechanical and thermo-oxidative properties. Those polymers are somewhat similar in nature to phenyl phosphonium, are qualified for space missions by NASA and are being commercially produced.
  • the invention also provides the innovative use of organically modified layered alu inosilicates 23 (ORMLAS) that combine the layered silicates and the organic co patibilizing agent 25 in a single chemical compound 21, rendering the material thermally stable, and highly organophilic.
  • ORMLAS organically modified layered alu inosilicates 23
  • This dual function compound is then miscible with a host of structural matrix resins such as polya ides (nylon T m 120 'C), polyether imide (Ultem ® T g 215 'C), polyi ides (T >275'C) and poly arylene ethers (T g >225-350'C).
  • structural matrix resins such as polya ides (nylon T m 120 'C), polyether imide (Ultem ® T g 215 'C), polyi ides (T >275'C) and poly arylene ethers (T g >225-350'C).
  • ORMLAS since the bonding of the organic group to the inorganic Si atom is through the Si- C bonds, the ORMLAS exhibits excellent thermal stability. Fabricating ORMLAS layered silicates with high temperature structural polymers offers an attractive combination of properties such as high heat distortion temperature, excellent impact resistance and excellent mechanical properties.
  • the invention provides high use-temperature light-weight polymer/inorganic nanocomposites which have outstanding properties, compared to the state of the art layered silicate nanocomposites that use alkyl ammonium as the surfactant.
  • a database of properties of control specimens is established for nanocomposites made from mixtures of a number of commodity polymers (e.g., Polystyrene, Nylon, modified Polyetherimide, Polyethylene oxide) with montmorillonite containing alkyl ammonium-surfactants (through cation- exchange) .
  • Superior polymer/layered silicate nanocomposites are fabricated by using mixtures of polyetherimide (PEI) resins with montmorillonite containing organic phosphonium surfactants, e.g., tetraphenyl phosphonium (TPP) (through cation-exchange) , via direct polymer melt intercalation process.
  • PEI polyetherimide
  • montmorillonite containing organic phosphonium surfactants e.g., tetraphenyl phosphonium (TPP) (through cation-exchange)
  • Superior nanocomposites are fabricated by direct polymer melt intercalating organically-modified layered aluminosilicates (ORMLAS) with polyetherimide and thermoplastic polyimide (PI) or polyarylene ether (PAE) resins.
  • ORMLAS organically-modified layered aluminosilicates
  • PI thermoplastic polyimide
  • PAE polyarylene ether
  • nanocomposites are designed by creating favorable interactions at the polymer-layered silicate interfaces. That is achieved by making the chemistry of the inorganic reinforcement phase more compatible with the organic polymer matrix, i. e. , by making the layered silicate surfaces organophilic.
  • the normally hydrophilic silicate surfaces are rendered organophilic after ion-exchange reactions of the loosely-held cations in the interlayer spaces of the silicate structure with organic cations.
  • Nanocomposites have been synthesized for a variety of commodity polymer systems. Nanocomposites with properties much superior to that of the corresponding unfilled and conventionally-filled polymers are hence obtained. This unique combination of improved properties, easy fabricability, and low-cost, offers tremendous potential for commercial applications of these materials.
  • polymer/inorganic nanocomposites 31, schematically shown in Figure 3, exploits the ability of the layered inorganic silicates 23 to accommodate polymer 33 chains 35 between the layers 23 creating intercalated hybrids 37.
  • Delaminated hybrids 39 are created by dispersing individual layers 23 in a continuous polymer matrix 41.
  • Figure 3 shows a schematic representation 31 of the polymer/inorganic nanocomposite structures 37, 39 obtained using the layered silicates 23.
  • Nanocomposites 37 have single polymer chains intercalated between the silicate layers 23.
  • the host silicate layers 23 are delaminated and dispersed in a continuous polymer matrix 41.
  • That synthetic design also exploits the ion-exchange capacity of these layered-silicates 23 which allows for a fine-tuning of their surface chemistry to create a favorable organic-inorganic interface.
  • layered silicates in the synthesis of those nanocomposites arise from their unique crystal structure.
  • Those layered silicate materials are fine-grained and have crystal structures with a "platy" habit.
  • Their structure is common to the family of 2:1 layered- or phyllosilicates, well-known examples of which are mica and talc.
  • the structure is composed of Si04 tetrahedra fused to edge-shared octahedra of aluminum or magnesium hydroxides.
  • Layer stacking leads to regular Van der aals gaps between the layers, viz., interlayer or gallery.
  • Isomorphic substitution of cations is common (for example, A13+ or Fe3+ substituting for Si4+ in the tetrahedral network) . That leads to a net negative charge on the structure, which is generally counter-balanced by cations residing in the interlayer spacing. Those cations are more or less readily exchanged and result in the cation-exchange capacity of the materials.
  • Those interlayer cations are, for example, Na+ or K+ in pristine layered silicates.
  • an organophilic surface chemistry is desired to create favorable interactions with the organic polymer matrix. Therefore, those inorganic cations are exchanged with various organic cations, e. g., alkyl ammonium cations.
  • the hydrophilic silicate surface is thus rendered organophilic.
  • Those surfactants typically are alkyl ammonium compounds e.g., dimethyl ditallow ammonium bromide.
  • dimethyl ditallow ammonium bromide is the use of dimethyl ditallow ammonium bromide to cation-exchange with the Na+- montmorillonite - a layered silicate.
  • Such ion-exchanged 'organo'silicate clays are commercially available.
  • the properties of the nanocomposites can be optimized through interfacial surface chemical design.
  • layered silicate nanocomposites has involved intercalation of a suitable monomer followed by in situ polymerization. Alternatively, polymer intercalation is carried out from solution. Those techniques limit use in the case of most technologically important polymers, since suitable monomers and compatible polymer-silicate solvent systems are not always available.
  • the spectrum of nanocomposite systems that can be synthesized is considerably broadened by the advent of a more versatile and environmentally-friendly synthetic approach, called direct polymer melt intercalation. In that approach, the polymer and the silicate are mixed, and the mixture is heated above the softening point of the polymer. That technique allows the synthesis of a much wider range of polymer/inorganic nanocomposites.
  • Polymers with varying degrees of polarity and crystallinity are directly intercalated into organically- modified layered silicates.
  • Example of polymers use direct polymer melt intercalation include polystyrene, poly (dimethylsiloxane) , poly (vinylidene fluoride), poly (e- caprolactone) , and (polyethylene oxide) .
  • Delamination of the silicate layers can also be achieved during nanocomposite synthesis through 'polymer melt intercalation' .
  • An example is the delamination of the individual silicate layers achieved by suspending ditallow ammonium-exchanged montmorillonite in PDMS
  • a key to obtaining superior properties at low inorganic loadings is the homogeneous nanoscale dispersion of the inorganic phase in the polymer, and the creation of favorable interactions at the organic-inorganic interface.
  • Favorable interfacial chemistry leads to organic and inorganic phases being dispersed at a nanometer level .
  • the superior properties of the new composites are obtained at low inorganic loadings.
  • the use of low inorganic contents leads to significant advantages. High degrees of stiffness, strength and barrier properties are obtained with far less inorganic content than comparable glass- or mineral reinforced polymers. Considerable weight savings are, therefore, obtained.
  • Nylon-layered nanocomposite automatic timing belt cover Some commercial applications of these materials are, for example, Nylon-layered nanocomposite automatic timing belt cover. Other applications include airplane interiors, fuel tanks, components in electrical and electronic parts, under- the-hood automotive structural parts, brakes and tires. Applications of nanocomposite barrier films may be used in food packaging and in other applications are also possibilities .
  • the nanocomposites yield significant enhancements in properties at low inorganic loadings also provides ease-of-manufacturing and several cost-benefits. It allows for the use of simple manufacturing techniques (viz., extrusion, injection-molding and casting) which are normally used for pure polymers. Therefore, the nanocomposites can be manufactured at a much lower cost than the more conventional fiber- or mineral-reinforced composites which require more expensive fabrication procedures. That provides further reasons for their commercial appeal .
  • Commodity polymers provide use-temperatures below 125 'C. Substructure applications for rockets and aircraft require higher long term use-temperatures of about 175 'C and 250 'C.
  • the thermal stability of the current state-of-the-art nanocomposite systems is often limited by the thermal instability of the surfactants used to create favorable interactions at the interface.
  • Those surfactants typically are alkyl ammonium compounds.
  • One example is the use of dimethyl ditallow ammonium bromide to ion-exchange with the Na+-montmorillonite - a layered clay.
  • the thermal stability of the nanocomposite system is, therefore, limited by the thermal stability of the alkyl ammonium compound. Degradation of those surfactant molecules, and hence that of the organic-inorganic interface, begins at temperatures around 100 - 110 'C.
  • the invention provides more thermally stable surfactants, which optimize the dispersion of the inorganic phase, and also enhance the compatibility at the organic- inorganic interface through the creation of favorable interactions.
  • the invention therefore provides enhanced use-temperatures of the nanocomposites.
  • One part elevates the use-temperature of the nanocomposite system by using more thermally stable surfactants than the currently used alkyl ammonium compounds.
  • the first part provides tetra-phenyl phosphonium compounds (with thermal stability in the range of 190' - 200 * C) to carry out a cation-exchange with the layered silicate reinforcement.
  • Tetraphenyl phosphonium is a reactive salt with a net positive charge, as shown in Figure 2.
  • the salt readily ion exchanges with the cations on the surface of the inorganic phase attaching itself from the oxide surface and thus rendering the surface organophilic. That surface modified system lends itself to direct melt intercalation.
  • tetraphenyl phosphonium is a high temperature organic moiety with thermal stability in excess of 200 'C
  • the first part of the invention provides nanocomposites which will satisfy the need for long-term use- temperatures of 175-200 'C.
  • the second part of the invention extends the use- temperature of the nanocomposites to over 250 'C. It is based on the innovative use of organically-modified layered alumino-silicates (ORMLAS) that combine the layered silicate and the organic surfactant/compatibility agent in a single chemical compound.
  • ORMLAS organically-modified layered alumino-silicates
  • the organic surfactant groups are bonded to the structural Si atom through thermally stable Si-C bonds.
  • the thermal stability of the overall system is therefore greatly enhanced. Therefore, those materials provide unique inorganic layered silicate reinforcements having markedly more thermally-stable surfactants "built-in" to the chemical structure.
  • polyamides nylon Tm 120'C
  • polyether imide Ultem T g 215'C
  • polyimides T >275 * C
  • PAE T m poly arylene ether
  • ORMLAS materials are synthesized using the sol-gel process where the organic groups are incorporated into the molecular structure through the use of organically modified silicon alkoxides, i. e. , precursors containing Si-CxHx bonds. The organic functionality is therefore directly bonded to the structural Si atom by the Si-C bond.
  • the organically modified aluminosilicate will be synthesized using mixtures of organically-modified silicon alkoxides and solutions of aluminum chloride.
  • the standard approach combines an alcohol solution of aluminum chloride with an alcohol solution of organically functionalized alkoxysilane.
  • the organically functionalized trialkoxysilane e. g.
  • alkyltriethoxysilane provides alkyl organic groups connected directly through Si-C bonds.
  • the mixture is then condensed (crosslinked) to form a gel at appropriate pH conditions by the addition of NaOH.
  • the gel is aged, filtered, washed with distilled water, and then dried in vacuum. That procedure yields a stable layered organophilic compound.
  • the resulting material is either precipitated as a powder, dried and ground to appropriate particle size, or cast into various shapes and forms. In that case, the ORMLAS is precipitated as a powder or ground and classified it into appropriate size particles for incorporation with the polymer matrix for direct melt intercalation.
  • ORMLAS compounds are especially engineered to dela inate in the presence of a variety of polymer resins - thus promoting the dispersion of the inorganic layers in the polymer matrix. That versatile and innovative new feature yield nanocomposites which will satisfy needs for a range of use- temperatures extending to long-term use-temperatures over 250 * C.
  • ORMLAS organically-modified layered silicates

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  • Compositions Of Macromolecular Compounds (AREA)
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Abstract

The invention provides new high.-use temperature, lightweight polymer/inorganic nanocomposite materials (37, 39) with enhanced thermal stability and performance characteristics. The invention provides two techniques that enhance the thermal stability of the nanocomposite systems (37, 39) from their current limits of 100 150 °C to over 250 °C. The two unique approaches are based on innovative chemical design of the organic-inorganic interface using (i) more thermally stable surfactants/compatibility agents, and (ii) more thermally stable synthetic organically-modified layered-silicate reinforcements (23) to create unique nanocomposites (37, 39). The new technonogy provides hitherto unabtainable thermal stability and performance characteristics, and has numerous applications in automotive, aerospace, electronic and food and beverage industries.d packaging materials. The new technology provides hitherto unobtainable thermal stability and performance characteristics, and has numerous applications in automotive, aerospace, electronic and food and beverage industries.
EP00919564A 2000-03-23 2000-03-23 Nanocomposites polymeres/inorganiques haute temperature Withdrawn EP1268185A4 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2000/007708 WO2001070492A1 (fr) 1997-06-06 2000-03-23 High-temperature polymer/inorganic nanocomposites

Publications (2)

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EP1268185A1 true EP1268185A1 (fr) 2003-01-02
EP1268185A4 EP1268185A4 (fr) 2004-07-21

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EP (1) EP1268185A4 (fr)
JP (1) JP2004503607A (fr)
AU (1) AU2000240226A1 (fr)
CA (1) CA2401052A1 (fr)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE159270T1 (de) * 1991-08-12 1997-11-15 Allied Signal Inc Bildung polymerer nanokomposite aus blättrigem schichtmaterial durch ein schmelzverfahren
US5530052A (en) * 1995-04-03 1996-06-25 General Electric Company Layered minerals and compositions comprising the same
US6060549A (en) * 1997-05-20 2000-05-09 Exxon Chemical Patents, Inc. Rubber toughened thermoplastic resin nano composites

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JP2004503607A (ja) 2004-02-05
EP1268185A4 (fr) 2004-07-21
AU2000240226A1 (en) 2001-10-03

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