RU2663160C2 - Solution-free method for producing nanocomposite binders in situ - Google Patents

Abstract

FIELD: nanotechnologies.SUBSTANCE: invention relates to nanotechnology and can be used for producing carbon plastics for space and aircraft apparatus engineering, as well as for building structures. Method for producing nanocomposite binders without the use of solvents involves two stages. At the first stage at room temperature, a cyanate ether monomer, carbon nanotubes and a dispersant based on sulfonylbisyanatophenylisoindolindione is simultaneously crushed. At the second stage in situ, the said monomer is oligomerized and the resultant mixture is sonicated.EFFECT: invention allows producing materials with predetermined properties, for example, electrical and thermal conductivity, and also improving their isotropy, increasing moisture resistance and durability.1 cl, 2 dwg, 2 ex, 4 tbl

Description

The invention relates to a technology for producing stable dispersions of carbon nanomaterials in thermoset oligomerized cyanate ethers without the use of solvents for their subsequent curing in the form of plastic or reinforced plastic. More specifically: the invention relates to the technology of simultaneous oligomerization of a cyanate ether monomer and ultrasonic dispersion of carbon nanotubes and a dispersant based on sulfonyl biscyanatophenyl isoindolinedione in situ.

Cyanate-ether binders have a number of key advantages and features that make them extremely important in space engineering. It is the unique chemical structure of the skeleton of the emerging spatial three-dimensional network of the polymer macromolecule that is the key basis for the important physical-chemical and thermomechanical properties that are manifested, such as: low dielectric constant, high thermal and crack resistance, ultra low moisture absorption. [Reghunadhan Nair C.P., Mathew D., Ninari K.N., Cyanate Ester Resins, Recent Developments, Advances in Polymer Science. Vol. 155, 2001. P. 84-87], [Hamerton I. Chemistry and technology of cyanate ester resins, Springer, 1994. Pp. 30-31, 116-117, 241-245]

Single-walled carbon nanotubes (CNTs) are actually graphene sheets rolled into a cylinder. Their unique structural features and quantum-size effects allow them to possess a number of unique properties. They have high thermal conductivity comparable to diamond, an ultra-low coefficient of linear thermal expansion, high modulus of elasticity and high strength. The high conductive and thermally conductive properties of CNTs are well known. [Prabhakar R. Bandaru, Electrical Properties and Applications of Carbon Nanotube Structures. Journal of Nanoscience and Nanotechnology Vol. 7, 1-29, 2007].

A known method of dispersing nanoscale objects in binders using high boiling solvents (N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) [Kevin D. Ausman, Organic Solvent Dispersions of Single-Walled Carbon Nanotubes: Toward Solutions of Pristine Nanotubes: Toward Solutions of Pristine Nanotubes: Toward Solutions of Pristine Nanotubes J. Phys. Chem. B, 2000, 104 (38), pp 8911-8915]. This method involves enormous technological difficulties as well as economic costs. When working with highly viscous binders, it is not possible to completely remove the solvent even from thin films. the surface of nanotubes, the solvent degrades new properties of the nanocomposite (dielectric, physicomechanical, gas evolution, etc.). In the case of parts of spacecraft, this will lead to desorption of the solvent and subsequent shrinkage and warpage of the entire structure, which in turn can lead to a deterioration in the dielectric properties of the product and loss of quality In addition, working with such solvents is harmful from an environmental point of view.

Also known is a method of manufacturing polymer nanocomposites on a thermoplastic binder for space, aviation, building and other structures (fiberglass, carbon fiber, organoplastics, etc.) using CNTs introduced into the binder using ultrasonic treatment. This method is described in patent RU 2497843 from 12.29.2011 and is the closest.

The proposed method for producing nanocomposite binders without the use of solvents allows the use of CNTs of various allotropic configurations and binders based on cyanate ethers to create materials with special properties: plastics and reinforced plastics for space, aviation, building and other structures.

For example: a dispersant based on sulfonyl biscyanatophenyl isoindolinedione and bisphenol A dicyanate monomer together with CNTs are sonicated at elevated temperature (150 ° C). CNTs are dispersed using an ultrasonic emitter and dispersant in the melt of the oligomerizable monomer in situ, rather than interfere with the oligomer using solvents. The simultaneous growth of the oligomer trimerization chains and the dispersion of CNTs allows one to obtain a stable nanocomposite oligomer. Nanoobjects, dispersant and matrix create a single structure and homogeneous topology, as a result of which CNTs do not aggregate and do not precipitate over time.

Synthesis of π-π dispersant to obtain a high-quality dispersion of carbon nanotubes and their subsequent connection with the cyanate-ether matrix

Based on the performed quantum-mechanical calculations using Materials Studio 8, the dispersant adsorption values on the surface of a single-walled CNT were selected for the synthesis of the following dispersants: bisphenol A diacrylate polyimide (PIBAD, foreign analogue) [Magu B. Chan-Park, Use of Polyimide-graft -Bisphenol A Diglyceryl Acrylate as a Reactive Noncovalent Dispersant of Single-Walled Carbon Nanotubes for Reinforcement of Cyanate Ester / Epoxy Composite, Chem. Mater. 2010, 22, 6542-6554] and sulfonyl biscyanatophenyl isoindolinedione (CBSII, patented substance). The adhesion of SBCPI to a single-walled carbon nanotube (SWCNT) as a result of calculations turned out to be higher than that of PIBAD (Table 1). After that, the characteristics of nanocomposites and carbon plastics obtained on their basis were studied. Schemes for the synthesis of dispersants are shown in figure 1 and 2.

It was noted that the dispersant based on SBCPI dissolves completely in the monomer and oligomer of bisphenol A dicyanate, unlike PIBAD. The obtained dispersions of SWCNTs have good dispersion (due to their high compatibility with the matrix) and are not sedimented. SWCNTs form the topology of the resulting polymer matrix and are associated with it due to the cyanate groups of the adsorbed dispersant. And with the help of π-π interactions, a bond is made between the imide dispersant fragments and the surface of the SWCNTs. An additional increase in the adhesion of the dispersant to the nanomaterial is possible by varying the imide fragment during its synthesis.

Example No. 1

1st stage. A mixture of powders of dispersant SBTSII (1% wt.), Carbon nanotubes (single-walled carbon nanotubes with hydroxyl groups) (1% wt.) And monomer of cyanate ether (bisphenol A dicyanate) (98% wt.) At room temperature.

2nd stage. Mechanical grinding of powders at room temperature.

3rd stage. Heating to obtain a monomer melt at T = 80 ° C

(The heating rate is not more than 5 ° C / min).

4th stage. Ultrasonic (ultrasound) dispersion.

5th stage. Heating to 150 ° C.

Example No. 2 (foreign counterpart for comparison)

1st stage. A mixture of PIBAD dispersant powders (1% wt.), Carbon nanotubes (single-walled carbon nanotubes with hydroxyl groups) (1% wt.) And cyanate ether monomer (bisphenol A dicyanate) (98% wt.).

2nd stage. Mechanical grinding of powders.

3rd stage. Heating to obtain a monomer melt at Т = 80 ° С (Heating rate not more than 5 ° С / min)

4th stage. Ultrasound dispersion.

5th stage. Heating to 150 ° C.

Obtaining films of a modified cyanate-ether binder for the production of prepreg.

When rolling films for the production of a prepreg based on high-modulus fiber and nanocomposite binders containing SWCNTs dispersed using various dispersants, it turned out that the PIBAD dispersant did not completely dissolve in the binder, which caused problems when rolling the films and, as a result, rather total embrittlement of the composite. SBCPI is completely dissolved in the binder.

* DMA - dynamic mechanical analysis.

* CNT = carbon nanotubes with carboxyl functional groups, purity 98%, production NanoShel, India)

Thus, the proposed method allows to obtain a solution-free method of nanocomposite binders in situ.

The low thermal conductivity of cyanate-ether binders with all their advantages does not allow for efficient heat removal from carbon fiber: the use of nanocomposite binders can completely solve this problem without increasing the mass of the structure.

Nanocomposite carbon plastics, films and coatings prepared by solvent-free technology open up opportunities for the creation of special-purpose materials with the desired properties of the finished product: electrical conductivity, thermal conductivity, dielectric and frequency characteristics.

Dispersed by the patented method, nanomaterials can be used to create nanocomposite carbon plastics with improved isotropy, moisture resistance, physical and mechanical properties, increased durability in operation at ultra low and high temperatures and increased dimensional stability.

Claims (1)

 A method for producing solvent-free nanocomposite binders, comprising two stages, the first stage simultaneously crushing the cyanate ether monomer, carbon nanotubes and a dispersant based on sulfonyl biscyanatophenyl isoindolinedione at room temperature; at the second stage, cyanate-ether monomer, carbon nanotubes and a dispersant based on sulfonyl biscyanatophenyl isoindolinedione in situ are oligomerized and sonicated.

Images