Aerogel and adhesive-containing composite, process for its produ

Details Aerogel and adhesive-containing composite, process for its produ Aerogel and adhesive-containing composite, process for its produ

1998-05-11

2000-11-07

Krynski, William

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Composite having voids in a component

4283066, 4283126, 4283179, 428338, 428446, 2523132, 252306, 2523152, B32B 500

Patent

active

061434000

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a new type of composite material, of any shape, which provides good thermal insulation, and which contains 5 to 97% aerogel particles and at least one adhesive, the diameter of the aerogel particles being smaller than 0.5 mm.
As a rule, conventional insulating materials that are based on polystyrene, polyolefins, and polyurethanes are manufactured by using foaming agents such as chlorofluorocarbons (CFC). The foaming agent that is entrained within the cells of the foam is what provides the good thermal insulation capability. Foaming agents of this kind constitute an environmental hazard because they gradually escape into the atmosphere.
Also known are moulded parts that contain duroplastic resins such as urea, melamine, and phenolformaldehyde resins or mixtures of such resins; these are then mixed with extenders such as wood powder, asbestos, and preferably cellulose, and optionally with slip agents such as zinc stearate, pigments such as titanium dioxide, softening agents such as glycerin, or o,p-toluolsulfonamide and/or acid or acid cleaving hardening accelerators, to form so-called moulding compounds that are hardened in presses by the application of pressures from 100 to 2500 bar at temperatures from 100 to 200.degree. C. to form moulded parts (Kunststoffhandbuch 10 "Duroplaste," [Plastics Handbook 10 "Duroplasts"], Publisher: Prof. Dr. Woebcken, 2nd Ed., 1988, Hanser Verlag, pp. 266-274). The resins can be used as powder resins in the so-called fused-mass process, or a liquid resins in the so-called liquid resin process. The composition of a typical moulding compound as defined by DIN 7708 Type 152 is as follows:
Standard sample parts obtained in accordance with DIN 7708 have densities between 1.5 and 2.0 g/cm.sup.3 and thermal conductivities between 300 and 600 mW/m.cndot.K (Kunststoffhandbuch 10 "Duroplaste," [Plastics Handbook 10 "Duroplasts"], Publisher: Prof. Dr. Woebcken, 2nd Ed., 1988, Hanser Verlag, pp. 269-270). This means that they are unsuitable for use as thermal insulation.
Because of their very low densities and high porosities aerogels, in particular those with porosities above 60% and densities of less than 0.6 g/cm.sup.3, display extremely low thermal conductivity, and for this reason are used as thermal insulation, as described in EP-A-O 171 722.
However, their high porosity results in poor mechanical stability, both of the gel from which the aerogel is dried, and of the dried aerogel itself.
It is also known that aerogels have extremely low dielelectric constants with values between 1 and 2, depending on the density of the aerogel. For this reason, aerogels are destined for use in electrical applications such as for high-frequency applications (See C. W. Hrubesh et al., Journal of Materials Research, Vol. 8, No. 7, pp. 1736-1741).
In the broadest sense, i.e., when regarded as "gels with air as the dispersant," aerogels are manufactured by drying a suitable gel. When used in this sense, the term "aerogel" includes aerogels in the narrower sense, such as xerogels and cryogels. A gel is designated as an aerogel in the narrower sense if the liquid is removed from the gel at temperatures above the critical temperature and starting from pressures that are above the critical pressure. In contrast to this, if the liquid is removed from the gel non-critically, for example with the formation of a liquid-vapour boundary phase, then the resulting gel is, in many instances, referred to as xerogel. It should be noted that the gels according to the present invention are aerogels in the sense that they are gels with air as the dispersant.
The process that shapes the aerogel is concluded during the sol-gel transition. Once the solid gel structure has been formed, the external shape can only be changed by size reduction, for example, by pulverizing.
For many applications, however, it is necessary to use the aerogel in certain shapes. To this end, it is necessary to carry out a shaping stage after the production of the aerogel, which is to say, after it has been dried,

REFERENCES:
patent: 5569513 (1996-10-01), Fidler et al.

Affiliated with

Also associated with

Rating

Aerogel and adhesive-containing composite, process for its produ does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Aerogel and adhesive-containing composite, process for its produ, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aerogel and adhesive-containing composite, process for its produ will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1638564