Method To Produce Polymer Matrix Composites

Abstract

This patent describes a new, simple, and low-cost method to produce aromatic thermosetting copolyester (ATSP) based polymer matrix composites. For this method, the ATSP based composites are directly produced from the blended mixtures of the ATSP oligomer powders with the composite fillers through a high temperature and high pressure curing process. In addition, the fully cured ATSP composite laminates can be bonded together to form thicker multi-material composites. The characterization showed that these ATSP based composites are fully condensed, they have excellent tribological performance (low friction and low wear rate), and they have excellent thermal stability, indicating utility in high performance bearing applications, structural materials, and as an ablative composite material.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority to provisional application Ser. No. 62 / 627,337 filed Feb. 7, 2018 entitled Ablative Composites Based on Aromatic Thermosetting Copolyester, 62 / 659,844 filed Apr. 19, 2018 entitled Reversible Adhesion and Interchain Transesterification Composite Welding Mechanism, and 62 / 786,269 filed Dec. 28, 2018 entitled Adhesive and Processing Methods Utilizing Exchangeable Chemical Bonds, all of which are incorporated herein by reference in their entirety.BACKGROUND OF THE INVENTION[0002]Typically, aromatic thermosetting copolyester resins are produced by a two-part oligomerization process wherein branched aromatic crosslinkable copolyester oligomers are synthesized in a melt with average molecular weights between 1000 and 2000 g / mol with monomer feed ratios selected such that the oligomers preferentially are capped with either carboxylic acid or acetoxy functional groups. These are synthesized with an initial f...

AI Technical Summary

Benefits of technology

[0005]This patent describes a new, simple, and low-cost method to produce continuous and discontinuous polymer matrix composite from a pre-polymer system that generates a volatile by-product as a consequence of its cure reaction. For example, the crosslinkable aromatic polyester oligomers evolve acetic acid as their cure by-product, forming an ester bond and thereby advancing molecular weight. The enabling feature that allows this is an abundance of exchangeable bonds within the resin. At temperatures above the glass transition temperature, polymer resins that feature exchangeable bonds (that are active in a temperature regime well before the resin begins to thermally degrade) have an additional mechanism of stress relaxation. Porosity evolved from the generation of a volatile by-product can be collapsed to negligible values and densities that approach theoretical values can thereby be achieved. Examples of exchange reactions that enable this process include transesterification, transimidization, transamidization, urea exchanbe, hydrogen bonding exchange, and sulfone exchange. In this patent, we demonstrate this principle using aromatic thermosetting copolyester (ATSP) based composites. For this method, we eliminate the need to either pre-cure any of the ATSP powders or need to use solvent; instead, the ATSP-based composites are directly produced from the mixture of the ATSP oligomer powders with the composite fillers thereby eliminating rate-limiting steps. In the curing process, the acetic acid off-gassing escape from the system between empty spaces and microscopic flow-paths introduced by the fillers, with high pressure at high temperature, the cured mixture can be fully condensed using the additional stress relaxation mechanism as described above. The produced ATSP based composites have excellent thermal stability and tribological performance and the laminates of the composites can be bonded together ex-situ to form thicker multi-material composites.

Problems solved by technology

These oligomers are typically brittle, glassy solids at room temperature which can have their particle size reduced to micron-scale powder by simple grinding with a laboratory blender.

However, substantially more grinding time was necessary due to the high mechanical properties of the ATSP resin and the reduction of the particle size becomes a significant rate-limiting step.

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