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EP-4735530-A1 - METHODS FOR POLYMER MATERIALS

EP4735530A1EP 4735530 A1EP4735530 A1EP 4735530A1EP-4735530-A1

Abstract

A process for the preparation of a polymer composition comprising the combination of silozane, cross-linked silozane, organic monomer and a photo initiator to allow the 3D printing preferably sterolithography of a polysilozane structure with UV exposure times similar to conventional UV curable resins, wherein the polymer composition allows article parts to be produced at speed with complex geometries relying on the mechanical properties of the polymer composition to retain fine features. Also provided are composites, articles and complex structures prepared according to the method.

Inventors

  • DUFF, PAUL
  • SEABRIGHT, Ryan

Assignees

  • QinetiQ Limited

Dates

Publication Date
20260506
Application Date
20240625

Claims (12)

  1. 1 . A process for the preparation of a polymer composition comprising the combination of silozane, cross-linked silozane, organic monomer and a photo initiator to allow the 3D printing preferably sterolithography of a polysilozane structure with UV exposure times similar to conventional UV curable resins, wherein the polymer composition allows article parts to be produced at speed with complex geometries relying on the mechanical properties of the polymer composition to retain fine features.
  2. 2. A process according to claim 1 wherein the photo initiator is selected from 4-Dimethylaminobenzophenone and Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide.
  3. 3. A process according to any preceding claim wherein the organic monomer is 1 ,6- Hexanediol diacrylate.
  4. 4. A process according to any preceding claim wherein the polysilazane composition includes a resin system comprising a blend of polysilazane polymer with silazane oligomer, said oligomer acting as a reactive diluent to tune the resin system to the desired viscosity to use as a prepreg, optionally comprising fillers, said system allowing the processing of polysilazane into ceramic matrix composite parts using suitable manufacturing techniques to process standard polymer composites and to allow the manufacture of composite parts with high temperature resistance wherein the reactive diluent comprises any oligomer of lower viscosity than the polysilazane and capable of reacting with said polysilazane to form a cross linked polymer network.
  5. 5. A process according to any preceding claim wherein the silozane is subsequently driven to full crosslink density through additional heat treatment.
  6. 6. A process according to any preceding claim wherein upon ceramification the polymer composition is degraded leaving a SiCN ceramic with good mechanical properties.
  7. 7. A method according to claim 1 wherein the cross-linked polymer has been prepared by cross linking under ambient conditions.
  8. 8. A method according to any preceding claim wherein fillers are included such as silicon carbide, boron carbide, milled carbon fibres, alumina-silicate fibres, glass fibres, silicon carbide fibres, chopped silicon carbide fibres, chopped glass fibres, chopped alumina silicate fibres, metal fillers (stainless steels, cobalt, nickel), Sialon particles, magnetic oxide fillers and stabilising fillers.
  9. 9. A method according to any preceding claim wherein the high temperature resistance is greater than 800, or greater than 1500, or up to about 2000 degrees C.
  10. 10. Composites prepared according to the method of any preceding method having a uniform microstructure or reduced porosity.
  11. 11. Articles or complex structures prepared using the method of any preceding claim.
  12. 12. Use of polymers or composites prepared by a method of any preceding claim in aerospace, automotive, energy , oil and gas industries.

Description

Methods for polymer materials The present invention relates to methods and compositions for processing polymers for use in ceramics technology, and products therefrom. In particular, the invention relates to Si-C-N ceramics, and improved products prepared therefrom. Existing methods for preparing Si-C-N ceramics include US 10,385,234, which discloses a method for the cross-linking of a polysilazane material with a fluoride containing catalyst in tetra h yd of u ran (THF) and O. Flores et al, J. Mat. Chem. A., 2013, 1 , 15406. Improved processes are required to allow polymer derived ceramics (PDC) materials to be easily fabricated and processed into new, large or complex shapes with improved properties - such as with improved strength and high temperature resistance. In particular improved manufacture methods are needed for the preparation of complex component geometries manufactured from high performance materials and for adaption for further methods, such as additive layer manufacture. Problems with existing processes and materials include that they do not allow the manufacture of certain composite materials, in particular machining materials from a block is expensive. Traditional methods for delivering complex geometries using complex manufacturing and post processing steps is also costly. There is also a need to enable the manufacture of finer features and to provide improved techniques to improve the strength of green bodies. According to the present invention there is provided a method according to the appended claims. In the process of the present invention the combination of silozane (preferably Durazane), crosslinked silozane (preferably cross-linked Durazane), organic monomer and a photo initiator allows the 3D printing of polysilozane structures with UV exposure times similar to conventional UV curable resins. In one embodiment the polymer composition provides scaffolding that allows parts to be produced with complex geometries relying on the mechanical properties of the polymer scaffolding to retain fine features. Benefits of the present invention include faster processes and finer product features. In a preferred embodiment the silozane can subsequently be driven to full crosslink density through additional heat treatment. In one embodiment, upon ceramification the polymer scaffolding is degraded leaving a SiCN ceramic with good mechanical properties. In one embodiment the combination and compositions optionally comprises fillers such as silicon carbide, boron carbide, milled carbon fibres, alumina-silicate fibres, glass fibres, silicon carbide fibres, chopped silicon carbide fibres, chopped glass fibres, chopped alumina silicate fibres, metal fillers (stainless steels, cobalt, nickel), Sialon particles, magnetic oxide fillers and stabilising fillers. In one embodiment the high temperature resistance is greater than 800, or greater than 1500, or up to about 2000 degrees C. In a further aspect the invention provides composites prepared by the invention method having a very uniform microstructure or reduced porosity approximately 75% of theoretical maximum density as measured using the Archimedes Principle. In a further aspect the invention provides the use of polymers or composites prepared by a method of any preceding claim in aerospace, automotive, oil and gas industries. Benefits of the invention methods include the ability to use any cross linked polysilazane to produce improved parts with relatively little deviation to existing manufacturing techniques, hence dramatically reducing the costs vs. standard ceramic matrix composites and in particular improved articles for use in automotive, energy and aerospace industries. Where catalysts are used, the catalyst may be a source of fluoride ions. The catalyst may be selected from tetraethylammonium fluoride or tetrabutylammonium fluoride. Preferably, the catalyst is tetrabutylammonium fluoride (TBAF). The solvent may be tetra hydrofuran. The solvent may additionally be toluene. The solvent may also be 2-methyltetrahydrofuran. The solvent may also be dibutylether. The solvent may be a mix of tetrahydrofuran or toluene in any particular ratio, with or without additional solvents selected from 2-methyltetrahydrofuran and dibutylether. The solvent may additionally be any other solvent known in the art, which dissolves both the oligosilazane, catalyst, and the quenching agent. The mass ratio of oligomer:solvent may be between 8:1 and 1 :8. The mass ratio of oligomer:solvent may more specifically be within the range 8:1 and 1 :1 , yet more specifically be within the range 8:1 and 3:1 , and further within the range 8:1 and 5:1. The mass ratio of oligomer:solvent may alternatively be within the range 1 :1 and 1 :8, more specifically within the range 1 :3 and 1 :8, yet more specifically within the range 1 :5 and 1 :8. The mass ratio of oligomer:solvent may be preferably within the range 1 :3 and 3:1 . More preferably the mass ratio of oligomersolvent m