JPS6056001B2 - Membrane material for radome - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber cloth used as a membrane material for a radome.

A radome is used to protect a radar antenna from wind, rain, snow, etc. As shown in FIG. 1, a radome 1 is assembled into a hemispherical shape by combining a plurality of panels 2.

As shown in FIG. 2, this panel 2 is constructed by using a metal frame 3 as a strength member and a membrane material 4 stretched between them. Generally, the following properties are required for this radome membrane material.

(1) Good radio wave transparency.

(Both dielectric constant and dielectric loss tangent values are small.) (2) Tensile strength and modulus are high, and creep and elongation are small.

(3) Characteristics that can withstand long-term outdoor use (more than 1 hour) (
(weather resistance, color stability).

(4) It must be easy to adhere to the metal frame, have high strength, and have long-term reliability.

Lately, rubber cloth type membrane materials have been used as this membrane material.

This rubber cloth for membrane materials (hereinafter referred to as membrane material) is a base fabric (for example,
A comb composition (ethylene propylene copolymer...) with good weather resistance on both sides of a woven fabric made of aramid fibers.
Hereinafter referred to as EPM. Or ethylene propylene diene copolymer...hereinafter referred to as EPDM. ) coated with This membrane material is characterized by a combination of high-performance aramid base fabric and inexpensive rubber.
The use of PM or EPDM rubber has the following drawbacks. Originally, EPM and EPDM rubbers have low polarity and have the poorest adhesion among various synthetic rubbers.

Therefore, even if the surface rubber has excellent weather resistance, it cannot be used as a com cloth (
It can also be used as a radome panel (coating adhesion with base fabric).
Unreliable for long-term outdoor use (adhesion to metal frames). In addition, this rubber has poor coloring stability,
In order to maintain a desired color tone stably over a long period of time, it is necessary to add a large amount of titanium white, a compounding agent with a high dielectric constant, of 3 parts or more, which will only significantly deteriorate the electrical properties. However, due to the increase in rubber viscosity, the coating workability during the rubber fabric manufacturing process becomes extremely poor. The present invention provides a high-performance radome membrane material that eliminates the drawbacks of conventional products as described above, and is suitable for EPM, EPD
An elastomer composition prepared by adding 1 to 20 parts of a polyhydroxy polymer containing 0H groups at both ends to 100 parts of a mixture of M, an inorganic filler, a plasticizer, a coloring agent, and a vulcanizing agent was impregnated with isocyanate. It is characterized by coating both sides of a woven fabric made of aramid base fabric.

Hereinafter, this invention will be specifically explained using one example.

Table 1 shows elastomer compositions for coating layers according to the present invention, and Table 2 shows conventional elastomer compositions for coating layers.

The polyhydroxy polymer containing 0H groups at both ends used here is a so-called liquid rubber and is hydrogenated, so it has excellent weather resistance, water resistance, heat resistance, etc., and because both ends have 0H groups, it is compatible with EPDM. It has good adhesion and coloring stability.

Therefore, by adding this liquid rubber as shown in Table 1, the coloring stability is improved, so the amount of titanium white added is half of the conventional composition, and the resulting composition and the conventional composition as shown in Table 2 are improved. Unlike the case of physical products, there is no deterioration in electrical properties or workability. Further, since the adhesion of this composition is improved by the addition of the above-mentioned liquid rubber, sufficient adhesive strength can be obtained in coating adhesion to base fabrics and adhesion to metal frames. In particular, the aramid woven fabric (manufactured by Kepler 9 DuPont) used here as the base fabric of the membrane material is an aromatic polyamide fiber that has excellent radio wave transparency, a property possessed by organic fibers, and a property found in conventional organic fibers. It combines the advantages of inorganic fibers, such as high strength, high modulus, and low elongation, making it the most suitable reinforcing base fabric for radomes.The only drawback of this woven fabric is its adhesiveness, which is impregnated with isocyanate. Due to the treatment, the adhesion with the compositions listed in the above table is always excellent. For comparison, the composition used in this invention shown in Table 1 and the conventional composition shown in Table 2 were coated on both sides of an aramid fabric with a coating of about 1.27 g.
n/TTI. Create thick sheets and measure each under the same conditions: (1) radio wave transmission loss (S band);
(2) Appearance change using a weather meter, (3) peel strength between the surface coating layer and base fabric, and (4) adhesive strength with aluminum were measured.

The amount of radio wave transmission loss was 2.8 to 3.1% for the product of the present invention, whereas it was as large as 3.2 to 4.0% for the comparative example, and the variation was wide. Appearance changes due to deterioration tests are as follows:
While the Comparative Example began to develop cracks and change in color tone after 10 (4) hours of outdoor exposure (equivalent to about 5 years), no changes were observed in the invention product even after 200011 days. The peel strength between the surface coating layer and the base fabric was 1.0 to 1.5 k9/Crfl in the comparative example, whereas the peel strength of the product of this invention was extremely strong at 2.5 to 3.0 kg/Cm. In addition, the adhesive strength using an epoxy adhesive (Araldite 9 manufactured by Ciba) was 0.2 in the peel test of Comparative Example.
5 to 0.6k9/CTn, in this invention 1.6 to 2
．． It was 4k9/cm.

As described above, the membrane material for radome according to the present invention is similar to that of conventional EP.
It is a high-performance film material for radomes that has particularly superior characteristics in terms of radio wave transmittance, weather resistance, coloring stability, workability, adhesiveness, etc., than coating film materials in the M, EPDM formulation.

[Brief explanation of the drawing]

FIG. 1 is an external view of a radome having a panel joint structure in which the present invention is implemented, and FIG. 2 is a perspective view of a spring constituting this radome. In the figure, 1 is a radome, 2 is a panel, 3 is a metal frame, 4
is a membrane material.

Claims (1)

[Claims] 1. For 100 parts of ethylene propylene copolymer or ethylene propylene diene copolymer mixed with inorganic filler, plasticizer, colorant, and vulcanizing agent,
A membrane material for a radome, characterized in that an elastomer composition containing 1 to 20 parts of a group-containing polyhydroxy polymer is coated on both sides of a woven fabric made of isocyanate-impregnated aramid fibers.