Patent Application
20250043114
This invention relates to an elastomeric composite containing an oxide filler, which will find application in the preparation of substrates and insulating layers for flexible antennas.
The document EN 112723 A is known, which relates to an elastomeric composition, encapsulating a compact antenna based on natural rubber. The composition according to the invention is based on natural rubber, and the components in the composition are in parts by mass per 100 parts by mass of natural rubber (phr), the components being: glass-ceramic filler, which is acermanite or mervinite-35-65; zinc oxide-3; stearic acid—2; polymerized trimethyl dihydroquinoline-1.5; tertiary butyl-benzothiazolyl-sulfenamide-1.5; sulphur-2. The known composition does not provide a sufficiently low dielectric loss angle tangent of the composite.
Another document U.S. Pat. No. 5,557,286 A has disclosed a composition of a dielectric ceramic having application in the fabrication of antenna structures. An improved dielectric powder was created containing barium strontium titanate BST, prepared by a sol-gel method. Graphite was added to the resulting dielectric powder, resulting in a highly porous BST substrate, where the included graphite is burned off. A low dielectric filler is added to the thermally treated substrate to provide a composite substrate of physical hardness. The filler may be organic or inorganic, such as epoxy resin or low-loss oxide powder. The composition according to the invention relates to a dielectric ceramic, which does not possess the necessary flexibility and elasticity, and could not be applied in the manufacture of substrates for flexible antennas.
The article of “L. Radev, Influence of thermal treatment on the structure and in vitro bioactivity of sol-gel prepared CaO—SiO2—P2O5 glass-ceramics, Processing and Application of Ceramics, 8 (2014) 3, 155-166” describes the synthesis and bioactive properties of a series of samples prepared at different temperatures up to 1,500° C. of CaO—SiO2—P2O5-based material. The resulting sol-gel glass-ceramic is biocompatible and is used in the preparation of joint prostheses.
Document CN103086703A discloses a ceramic material containing a multi-component oxide filler that possesses a relatively low dielectric loss angle tangent, but it lacks sufficient flexibility and ductility, and thus could not be used in elastic substrates for flexible antennas.
The objective of this invention is to create a composition of an elastomeric composite containing an oxide filler and for the composite to have a low dielectric loss angle tangent, high flexibility and elasticity, which ensures its use in the substrates of flexible antennas.
Such objective is achieved by an elastomeric composite composition according to the invention based on natural rubber containing an oxide filler, which is calcium silicate phosphate CaO—SiO2—P2O5 in the amount of 25 to 75 parts by mass per 100 parts by mass of rubber (phr) and the remaining ingredients are zinc oxide, stearic acid, tertiary butyl benzothiazolyl sulfenamide and sulphur in the following amounts: zinc oxide—from 3 to 5, stearic acid—from 1 to 3; tertiary butyl benzothiazolyl sulfenamide—from 0.6 to 1 and sulphur—from 2 to 3.
The amount of components of the oxide filler CaO—SiO2—P2O5 are (in wt %): CaO—63.70. P2O5—5.97, SiO2—30.33.
The CaO—SiO2—P2O5 oxide filler was synthesized by a multistep sol-gel method, which includes the following operations: preparation of sol A by mixing suitable amounts of Ca(OH)2 and SiO2; preparation of sol B containing two components of Ca(OH)2 and H3PO4; mixing the two sols, and the resulting mixed sol is gelled at 120° C. for 12 hours and treated thermally at 1,200° C. Three crystal phases are obtained:
The synthesized sample has the following phase composition, confirmed by the XRD-analysis and FTIR-spectroscopy:
To date, there is no known elastomeric composite with filler based on a three-component oxide mixture of CaO—SiO2—P2O5. Surprisingly, it was found that the elastomeric composite containing the filler has the required low dielectric loss angle tangent due to the incorporation of the filler according to the invention and in addition the composite has high flexibility and elasticity, which ensures its use in the substrates for flexible antennas.
The incorporation of CaO—SiO2—P2O5 as a filler in elastomer composites used as substrates in flexible antennas provides enhanced performance, guarantees a lower dielectric loss angle tangent of the composite material compared to known solutions. Due to its lower dielectric losses, the elastomer composite offers flexibility and elasticity that ceramics do not have.
The preferred example embodiments illustrate the invention without limiting it
According to the invention, the filler based on CaO—SiO2—P2O5 has the following physical and chemical properties:
Chemical composition of the filler:
The phase composition was confirmed by XRD-analysis and FTIR-spectroscopy of the synthesized sample, which was as follows:
Dielectric Characteristics of the Studied Composites at Frequency of f=2.56 GHz
According to the aforementioned indicators, NR-75 is the most suitable for incorporation into elastomeric composites as it possesses the lowest value of the dielectric loss angle tangent, and the composites were tested at a frequency of 2.56 GHz.
From the studies conducted on the filler properties based on CaO—SiO2—P2O5, a composition of elastomer composites for embedding in flexible antennas was developed including the following components:
Composition of elastomeric composites (in phr parts by mass per 100 parts by mass of rubber):
Initially, the rubber is plasticized. At the fourth minute of plasticizing, zinc oxide and stearic acid are added. After a three-minute homogenization, i.e. on the seventh minute, half the amount of filler is added. After another three-minute homogenization, respectively at the tenth minute, the second half of the filler is added. Next, the mixture is homogenized again and at the sixteenth minute the vulcanization accelerator (TBBS) and sulphur are added. The mixture is again homogenized for four minutes and at the twentieth minute the rubber mixture is now ready and removed from the mixer.
Composition of elastomeric composites (in phr parts by mass per 100 parts by mass of rubber):
Making the rubber compound in a sequence of operations and process mode, as in Example 1.
Composition of elastomeric composites (in parts by mass per 100 parts by mass of rubber):
