CN116001176A - Method for preparing foaming Bo lens - Google Patents
Method for preparing foaming Bo lens Download PDFInfo
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- CN116001176A CN116001176A CN202211684227.3A CN202211684227A CN116001176A CN 116001176 A CN116001176 A CN 116001176A CN 202211684227 A CN202211684227 A CN 202211684227A CN 116001176 A CN116001176 A CN 116001176A
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Abstract
The invention relates to a method for preparing a foaming Luneberg lens, and belongs to the technical field of foaming. The invention provides a method for preparing a foaming Luneberg lens, which uses a foaming mould composed of an inner mould and an outer mould, and firstly continuously placing a sphere to be foamed at a saturation temperature T s The pressure is the saturation pressure P s Until the foaming agent gas is fully saturated in the sphere to be foamed, and continuously placing the sphere to be foamed at the foaming temperature T f The pressure is the saturation pressure P s And finally, placing the sphere to be foamed in a spherical outer die cavity for foaming to obtain the foamed Lasiosphaera lens. The method is realized by controlling the to-be-foamed materialThe temperature gradient in the sphere effectively controls the density distribution of the sphere to be foamed after foaming, and further obtains the foamed Luneberg lens with continuously changing relative dielectric constant.
Description
Technical Field
The invention relates to a method for preparing a foaming Luneberg lens, and belongs to the technical field of foaming.
Background
A lens antenna is an antenna capable of obtaining a pencil, fan or other shape beam by converting spherical waves or cylindrical waves of a point source or line source into plane waves by electromagnetic waves. The lens antenna is composed of a lens and an electromagnetic radiator. The electromagnetic wave emitted by the electromagnetic radiator has wave grain two-image, and refraction phenomenon can occur when the electromagnetic wave passes through different non-parallel mediums in the transmission process. The lens is a group of optical devices consisting of a uniform lens and a non-uniform lens, and the lens is arranged in front of the radiator, so that the radiation energy is concentrated, the beam pressure is narrow, and finally, the focusing of electromagnetic wave energy is realized in the form of plane waves.
The luneberg lens belongs to a non-uniform lens, the dielectric constant of which gradually changes from inside to outside according to a specific rule, and the gain of the antenna can be realized by changing the propagation direction of electromagnetic wave beams. The luneberg lens antenna can make electromagnetic waves entering the lens at any point converged into equiphase plane waves on the outgoing aperture surface in the corresponding direction. The Robert lens antenna has a unique perfect optical focusing performance, and has a great application prospect in the fields of aerospace and the like. However, the existing methods of preparing foamed luneberg lenses have problems that severely hamper the widespread use of Long Bo lens antennas.
For example, patent application publication No. CN110911846a discloses a method for producing a luneberg lens without using an adhesive, which uses a multi-layer mold core to simulate the variation of dielectric constant of the luneberg lens, but the method has the defects of complex production process, high product quality, need of hoisting production, and low production efficiency; the patent application publication No. CN109994837A discloses a method for producing the Luneberg lens, which changes the dielectric constant gradient of the Luneberg lens by one-time foaming after multi-layer wrapping, but the method has the defects of enough wrapping layers, complex production process and lower production efficiency, and if the number of wrapping layers is small, the production process can be simplified, the production efficiency can be improved, but the gradual change of the dielectric constant is not obvious, and the requirement of the Luneberg lens cannot be met; the patent application text with publication number of CN109687158A discloses a full-medium multi-beam scanning Robert lens structure suitable for 3D printing and a printing method, wherein the method prepares the Robert lens by a method of splicing two hemispherical lenses after 3D printing, but 3D printing has the defects of high cost, weak industrialization capability, overlong preparation time and lower production efficiency; patent application publication CN110401039a discloses a method for producing a luneberg lens, which uses an adhesive to bond multiple layers of granular materials to form a spherical luneberg lens, but this method requires a large amount of adhesive to pollute the environment, and this method cannot ensure uniform bonding thickness, has a large influence on performance, and in addition, the operation steps of this method are very complicated; the patent application publication No. CN110311227A discloses a method for producing a spliced type Robert lens, which comprises the steps of firstly manufacturing a granular material into a plurality of hemispheres, and splicing the hemispheres into spheres, wherein the method does not use an adhesive, but can not ensure the stability of splicing, and the distribution of the granules at the splicing position is relatively uneven, so that the performance is influenced; the patent application document with publication number of CN112736485A discloses a foaming Lasiosphaera lens and a preparation process thereof, the method comprises the steps of firstly printing dielectric layers with different dielectric constants layer by layer in a 3D way to form a plurality of layers of spheres to be foamed with different dielectric constants, and then foaming the spheres to be foamed to prepare the Long Bo lens, but the method is still based on 3D printing, and has higher production cost, weaker industrialization capability, longer preparation time and lower production efficiency; the patent application publication No. CN113105665A discloses a dielectric material and a manufacturing method thereof, wherein the method is used for preparing the Long Bo lens by performing pressure maintaining foaming on a sphere to be foamed twice and then performing rapid pressure releasing foaming, but the method needs two temperature control processes, two pressure control processes, one standing process and two pressure maintaining foaming processes, the steps are complicated, the process parameters are numerous, the production regulation and control are difficult, and in addition, the method also has the problems of long time consumption and low production efficiency.
Therefore, it is needed to find a method for preparing Long Bo lens with simple production process, high production efficiency and low cost, and the prepared Long Bo lens has good performance.
Disclosure of Invention
To solve the above-mentioned drawbacks, the present invention provides a foaming mold comprising an inner mold and an outer mold; the inner mold comprises a plurality of inner mold components; the inner die assembly can be combined into a spherical body with an inner die cavity; the inner mould cavity is used for accommodating the sphere to be foamed and the foaming agent gas; the outer die is provided with a plurality of notches corresponding to the inner die assembly; the outer die and the inner die assembly can be combined into a spherical body with a spherical outer die cavity inside; the outer mold cavity is used for foaming the sphere to be foamed.
In one embodiment of the present invention, the inner mold consists of two longitudinal inner mold assemblies and two transverse inner mold assemblies; the two longitudinal inner mold assemblies and the two transverse inner mold assemblies are symmetrically arranged.
In one embodiment of the invention, sealing rings are provided at the edges of the two longitudinal inner mould members.
In one embodiment of the present invention, a plurality of ventilation pipes are inserted into the inner mold.
In one embodiment of the invention, the ventilation pipe is controlled by a valve.
In one embodiment of the present invention, the diameter of the vent pipe is 10 to 100mm.
In one embodiment of the invention, the diameter of the vent tube is 32mm.
In one embodiment of the present invention, the number of the ventilation pipes is two; the two vent pipes are respectively inserted on the two longitudinal inner die assemblies.
In one embodiment of the present invention, the outer mold is provided with a plurality of vent holes.
In one embodiment of the invention, the vent holes are evenly distributed on the outer mold.
In one embodiment of the present invention, the outer mold is configured to be openable and closable.
In one embodiment of the present invention, the diameter of the vent hole is 0.1 to 10mm; the distance between two adjacent vent holes is 0.5-30 mm.
In one embodiment of the invention, the diameter of the vent hole is 1mm; the distance between two adjacent vent holes is 5mm.
In one embodiment of the invention, the foaming mold further comprises a driving assembly; the output end of the driving component is connected with the inner die component, so that the inner die component is switched in a combined state and a separated state.
In one embodiment of the present invention, the two longitudinal output ends of the driving assembly are respectively connected with the two longitudinal mold assemblies, so that the two longitudinal mold assemblies can move towards the center of the outer mold or towards the notch of the outer mold; the two transverse output ends of the driving assembly are respectively connected with the two transverse inner die assemblies, so that the two transverse inner die assemblies can move towards the center of the outer die or towards the notch of the outer die.
In one embodiment of the present invention, when both the longitudinal mold assembly and the transverse mold assembly are moved toward the center of the outer mold, the inner mold assemblies are combined into a spherical body with an inner mold cavity therein; when the longitudinal mold assembly and the transverse inner mold assembly both move towards the notch of the outer mold, the outer mold and the inner mold assembly are combined into a spherical body with a spherical outer mold cavity inside.
In one embodiment of the invention, the drive assembly is a hydraulic drive assembly; the longitudinal output end of the driving assembly is a longitudinally arranged hydraulic rod; the transverse output end of the driving assembly is a transverse hydraulic rod.
In one embodiment of the invention, the foaming mold further comprises a temperature control system; the temperature control system is used for controlling the temperature of the inner die cavity.
The invention also provides a method for preparing the foaming Luneberg lens, which uses the foaming mould and comprises the following steps:
step one: placing the sphere to be foamed into an inner die cavity, and controlling the temperature of the inner die cavity to be the saturation temperature T s ；
Step two: after the step one is finished, injecting the foaming agent gas into the inner die cavity until the pressure in the inner die cavity reaches the saturation pressure P s ；
Step three: after the second step is finished, continuously placing the sphere to be foamed at a saturation temperature T s The pressure is the saturation pressure P s Until the foaming agent gas is completely saturated in the sphere to be foamed; the time for the foaming agent gas to be fully saturated in the sphere to be foamed is the saturation time t s ；
Step four: after the third step is finished, the temperature of the inner die cavity is controlled to be the foaming temperature T f ；
Step five: after the fourth step, continuously placing the sphere to be foamed at a foaming temperature T f The pressure is the saturation pressure P s Until a temperature gradient is formed inside the sphere to be foamed; the time for forming the temperature gradient in the sphere to be foamed is the temperature rise time t f ；
Step six: and fifthly, after the step of finishing, moving the inner mold assembly to the notch of the outer mold so that the sphere to be foamed foams in the spherical outer mold cavity to obtain the foamed Luneberg lens.
In the first step, the sphere to be foamed is put into an inner die cavity as follows: the inner mould assembly is moved to a notch of the outer mould, then the sphere to be foamed is placed into the longitudinal inner mould assembly below, the two longitudinal inner mould assemblies are pushed to the center of the outer mould through the longitudinally arranged hydraulic rods until the two longitudinal inner mould assemblies are in contact with the sphere to be foamed, and finally the two transverse inner mould assemblies are pushed to the center of the outer mould through the transversely arranged hydraulic rods until the two transverse inner mould assemblies are in contact with the sphere to be foamed.
In one embodiment of the present invention, the calculation formula of the inner diameter of the outer mold is as follows:
wherein d out The inner diameter of the outer die is in mm; d, d ball Straight for the sphere to be foamedDiameter in mm.
In one embodiment of the present invention, the diameter of the inscribed circle of the inner mold cavity is equal to the diameter of the sphere to be foamed.
In one embodiment of the invention, the material of the sphere to be foamed is an amorphous polymer or a semi-crystalline polymer.
In one embodiment of the present invention, the amorphous polymer is one or more of polyphenylene oxide (PPO), polycarbonate (PC), polystyrene (PC), and polymethyl methacrylate (PMMA).
In one embodiment of the invention, the semi-crystalline polymer is one or more of polypropylene (PP), polyethylene (PE), polybutylene (PB), polylactic acid (PLA), polyethylene terephthalate (PET), liquid crystal polyester (TLCP), nylon 6 (PA 6) and nylon 66 (PA 66).
In one embodiment of the invention, when the sphere to be expanded is an amorphous polymer, the saturation temperature T s ＝T g -50℃～T g The method comprises the steps of carrying out a first treatment on the surface of the Wherein T is g Glass transition temperature of amorphous polymer;
when the sphere to be expanded is a semi-crystalline polymer, the saturation temperature T s ＝T m -100℃～T m -20 ℃; wherein T is m Is the melting temperature of the semi-crystalline polymer.
In one embodiment of the invention, the saturation pressure P s ＝5～20MPa。
In one embodiment of the invention, the saturation time t s ≥a×(d/2) 1.75 ；
In the formula, the saturation time t s In hours, a= 0.07762 hours/mm 1.75 D is the diameter of the foam sphere, and the unit is mm.
In one embodiment of the invention, when the sphere to be foamed is an amorphous polymer, the foaming temperature T f ＝T g +10℃～T g +100℃; wherein T is g Glass transition temperature of amorphous polymer;
when the sphere to be foamed isSemi-crystalline polymers, said foaming temperature T f ＝T m -15℃～T m +10℃; wherein T is m Is the melting temperature of the semi-crystalline polymer.
In one embodiment of the present invention, the temperature rise time t f =d ball /2；
In the heating time t f Is in minutes; d, d ball The diameter of the sphere to be foamed is in mm.
In one embodiment of the present invention, the diameter of the sphere to be foamed is 5-1000 mm.
In one embodiment of the present invention, the diameter of the foamed Long Bo lens is from 9.46 to 1354mm.
The invention also provides a foaming Lasiosphaera Seu Calvatia lens, which is prepared by the method.
In one embodiment of the invention, a protective layer is provided on the outside of the foamed Long Bo lens.
In one embodiment of the present invention, the protective layer is one or more of a polypropylene film, a polyethylene film, and a polyethylene terephthalate film.
In one embodiment of the present invention, the relative dielectric constant of the foamed luneberg lens in the radial direction gradually changes from 2 to 1, and the change rule thereof conforms to the following formula:
wherein r is the distance from a point in the radial direction of the bubble gabion lens (i.e. the dielectric material body) to the center of the bubble gabion lens, and the unit is mm and epsilon r The relative dielectric constant at a certain point in the radial direction of the foaming luneberg lens is free of units, and R is the radius of the foaming luneberg lens and the unit is mm.
In one embodiment of the invention, the gradual change in the dielectric constant of the foamed luneberg lens is achieved by a gradual change in density. For example, when mostThe density of the outer material is 30kg/m 3 The dielectric constant is 1.04, and the density of the material is 810kg/m 3 A dielectric constant of 2.08, a relative dielectric constant of 2, and a material density of 30kg/m 3 The dielectric constant was 1.04, and the relative dielectric constant was 1.
The invention also provides application of the method in preparation of the foaming Lasiosphaera Seu Calvatia lens.
The technical scheme of the invention has the following advantages:
the invention provides a method for preparing a foaming Luneberg lens, which uses a foaming mould composed of an inner mould and an outer mould, and firstly continuously placing a sphere to be foamed at a saturation temperature T s The pressure is the saturation pressure P s Until the foaming agent gas is fully saturated in the sphere to be foamed, and continuously placing the sphere to be foamed at the foaming temperature T f The pressure is the saturation pressure P s And finally, placing the sphere to be foamed in a spherical outer die cavity for foaming to obtain the foamed Lasiosphaera lens. According to the method, the density distribution of the spherical body to be foamed is effectively controlled by controlling the temperature gradient in the spherical body to be foamed, so that the foamed Luneberg lens with continuously variable relative dielectric constant is obtained, 3D printing is not required, the foamed Luneberg lens with continuously variable relative dielectric constant can be prepared through one-time foaming, the process flow is greatly simplified, the production efficiency is improved, the preparation process is stable and controllable, the advantages of low production cost are achieved, and the method has an application prospect in the mass production of Long Bo lenses.
Further, the method uses two longitudinal inner mold assemblies of the foaming mold provided with sealing rings at the edges. The sealing ring can effectively prevent the foaming agent gas from leaking in the saturation process.
Further, when the sphere to be foamed is an amorphous polymer, the saturation temperature T s ＝T g -50℃～T g The method comprises the steps of carrying out a first treatment on the surface of the Wherein T is g Glass transition temperature of amorphous polymer; when the sphere to be foamed is a semi-crystalline polymer, the saturationTemperature T s ＝T m -100℃～T m -20 ℃; wherein T is m Is the melting temperature of the semi-crystalline polymer. The function of setting the saturation temperature is to ensure that the sphere to be foamed can not only keep the original sphere in the saturation process, but also ensure certain CO 2 Diffusion rate. If the saturation temperature is too low, CO 2 The diffusion rate is low, the saturation time is long, and the process efficiency is seriously affected. If the saturation temperature is too high, the polymer is in a flowing state, the spherical shape cannot be kept in full contact with the inner die, and the problems of eccentricity, uneven foaming and the like are easily caused in the subsequent temperature rising process. At the same time, the saturation temperature is set in such a way that, in conjunction with the foaming temperature, a temperature gradient is formed in the body to be foamed, and this temperature gradient can be adapted to the saturation pressure, so that a Lunebo lens with a specific dielectric constant distribution can be produced.
Further, the saturation pressure P s =5 to 20MPa. The effect of the saturation pressure is set to match the saturation temperature and the foaming temperature so that the resulting Long Bo lens will conform to the radial dielectric constant profile, which will vary with the saturation temperature and the foaming temperature.
Further, the saturation time t s ≥a× (d/2) 1.75 The method comprises the steps of carrying out a first treatment on the surface of the In the formula, the saturation time t s In hours, a= 0.07762 hours/mm 1.75 D is the diameter of the foam sphere, and the unit is mm. The purpose of the saturation time is to fully saturate the blowing agent gas.
Further, when the sphere to be foamed is an amorphous polymer, the foaming temperature T f ＝T g +10℃～T g +100℃; wherein T is g Glass transition temperature of amorphous polymer; when the sphere to be foamed is a semi-crystalline polymer, the foaming temperature T f ＝T m -15℃～T m +10℃; wherein T is m Is the melting temperature of the semi-crystalline polymer. The purpose of setting the foaming temperature is to enable the dielectric constant of the outermost side to meet the requirements of the Luneberg lens after the sphere to be foamed is foamed. If the foaming temperature is too lowThe outermost foaming ratio is too low and the dielectric constant is too high; if the foaming temperature is too high, the outermost foaming multiplying power is too high and the dielectric constant is too low; if the foaming temperature continues to rise, the outermost polymer cannot maintain its original shape, and the melt strength of the polymer is too low to support cells, resulting in failure of foaming.
Further, the temperature rise time t f =d ball 2; in the heating time t f Is in minutes; d, d ball The diameter of the sphere to be foamed is in mm. The purpose of the heating time is to form a temperature gradient inside the sphere to be foamed, thus forming a density gradient during foaming, and finally forming a dielectric constant distribution. If the temperature rise time is too long, the temperature gradient moves towards the sphere center, the outer foaming multiplying power is too large, and the outer dielectric constant is too small; if the temperature rise time is too short, the temperature gradient moves to the outside of the ball, the internal foaming ratio is too low, and the internal measurement dielectric constant is too high.
Drawings
Fig. 1: the structure of the foaming mould is schematically shown.
Fig. 2: schematic of the preparation flow of the foamed luneberg lens.
Fig. 3: the relative dielectric constants of the foamed luneberg lenses obtained in examples and comparative examples are plotted against radius.
Fig. 4: the internal structure of the resulting foamed gabion lens of example 2.
In fig. 1, an inner die 1, an outer die 2, a driving assembly 3, a longitudinal inner die assembly 4, a transverse inner die assembly 5, an inner die cavity 6, a notch 7, a spherical outer die cavity 8, a vent pipe 9, a vent hole 10 and a hydraulic rod 11.
Detailed Description
The following examples are provided for a better understanding of the present invention and are not limited to the preferred embodiments described herein, but are not intended to limit the scope of the invention, any product which is the same or similar to the present invention, whether in light of the present teachings or in combination with other prior art features, falls within the scope of the present invention.
The following examples do not identify specific experimental procedures or conditions, which may be followed by procedures or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
The homo-polypropylene solid spheres to be foamed referred to in the following examples and comparative examples were obtained by injection molding of commercially available polypropylene particles by an injection molding machine using a conventional process, and the polyphenylene ether solid spheres to be foamed were obtained by injection molding of commercially available polyphenylene ether particles by an injection molding machine using a conventional process.
The dielectric constants of the foamed luneberg lenses (i.e., dielectric material bodies) obtained in the following examples and comparative examples were obtained by density conversion, and the conversion formulas were as follows:
wherein ε is the dielectric constant at a point in the radial direction of the foamed Luneberg lens (i.e., the dielectric material body) PP The dielectric constants of the sphere to be foamed which is solid by homopolymerized polypropylene or the sphere to be foamed which is solid by polyphenyl ether are respectively 2.2 and 2.6, and the values are p PP The density of the sphere to be foamed is 900kg/m respectively 3 And 1.05g/cm 3 ，ρ air The dielectric constant of air is 1, ρ foam Is the density at a point in the radial direction of the bubble gabion lens;
the density of the foaming Luneberg lens (namely the dielectric material body) at a certain point in the radial direction is measured by adopting a drainage method, and the measuring method comprises the following steps: cutting the foaming Lasiosphaera lens along a first spherical surface and a second spherical surface to obtain a part to be detected containing the point, wherein the first spherical surface and the second spherical surface are complete spherical surfaces, the spherical centers of the first spherical surface and the second spherical surface are coincident with the spherical center of the foaming Lasiosphaera lens, the thickness of the part to be detected (namely, the difference between the radiuses of the first spherical surface and the second spherical surface) is 1mm, the point is positioned at the center of the part to be detected in the thickness direction, and the density of the part to be detected is measured through a drainage method, namely, the density of the part to be detected in the radius direction of the foaming Lasiosphaera lens is obtained.
The relative dielectric constants of the foamed lobster lenses (i.e., dielectric material bodies) obtained in the following examples and comparative examples are ratios of the dielectric constants thereof to the outermost dielectric constants.
Example 1: foaming mould
As shown in fig. 1, the present embodiment provides a foaming mold, which is composed of an inner mold (made of stainless steel), an outer mold (made of stainless steel), a driving assembly and a temperature control system; the inner mold consists of two longitudinal inner mold components and two transverse inner mold components; the two longitudinal inner mold assemblies and the two transverse inner mold assemblies are symmetrically arranged, and the two longitudinal inner mold assemblies and the two transverse inner mold assemblies can be combined into a spherical body with an inner mold cavity; the inner mould cavity is used for accommodating the sphere to be foamed and the foaming agent gas; the outer mold is in an openable and closable arrangement (the outer mold consists of two outer mold components which are symmetrically arranged, and the two outer mold components are opened and closed through a hinge), and two notches corresponding to the longitudinal inner mold components and two notches corresponding to the transverse inner mold components are formed in the outer mold; the outer die, the longitudinal inner die assembly and the transverse inner die assembly can be combined into a spherical body with a spherical outer die cavity inside; the outer mold cavity is used for foaming the sphere to be foamed; sealing rings are arranged at the edges of the two longitudinal inner mold assemblies; two vent pipes are inserted into the inner die; the two vent pipes are respectively inserted into the two longitudinal inner die assemblies; the ventilation pipe is controlled by a valve; the diameter of the vent pipe is 32mm; a plurality of vent holes are formed in the outer die; the vent holes are uniformly distributed on the outer die; the diameter of the vent hole is 1mm; the distance between two adjacent vent holes is 5mm; the two longitudinally arranged hydraulic rods of the driving assembly are respectively connected with the two longitudinal die assemblies, so that the two longitudinal die assemblies can move towards the center of the outer die or towards the notch of the outer die; the two transversely arranged hydraulic rods of the driving assembly are respectively connected with the two transverse inner die assemblies, so that the two transverse inner die assemblies can move towards the center of the outer die or towards the notch of the outer die (when the longitudinal die assemblies and the transverse inner die assemblies move towards the center of the outer die, the inner die assemblies are combined into a spherical body with an inner die cavity, and when the longitudinal die assemblies and the transverse inner die assemblies move towards the notch of the outer die, the outer die assemblies and the inner die assemblies are combined into a spherical body with a spherical outer die cavity; the two longitudinal inner mold assemblies and the two transverse inner mold assemblies are internally provided with cavities for containing heat conduction oil; the temperature control system is a mold temperature machine; the die temperature machine heats the heat conduction oil, the heated heat conduction oil is led into the cavities of the two longitudinal inner die assemblies and the two transverse inner die assemblies through the pipeline, the heat is transferred to the whole inner die through heat transfer by the heating oil entering the cavities, and the flow and the temperature of the heat conduction oil are controlled through the die temperature machine, so that the temperature of the inner die cavity is controlled.
Example 2: method for preparing foaming Bo lens
The embodiment provides a method for preparing a foaming Lasiosphaera lens, which uses a foaming mold (diameter of a homo-polypropylene solid sphere to be foamed is 109mm, a foaming mold with an inner diameter of 150mm and an inscribed circle diameter of an inner mold cavity of 109mm is selected, and when the foaming mold is in an initial state, an upper longitudinal inner mold component, a lower longitudinal inner mold component, a left transverse inner mold component and a right transverse inner mold component are positioned at a notch of an outer mold) in the embodiment 1;
the method comprises the following steps (as shown in fig. 2):
step one: the temperature of the inner die cavity is controlled to be 125 ℃ (saturation temperature T) through a temperature control system s ) The method comprises the steps of carrying out a first treatment on the surface of the The outer mould is opened, and the homo-polypropylene solid sphere (T) m 155 ℃ and 109mm in diameter) are placed in the lower longitudinal inner mold assembly, then the two longitudinal inner mold assemblies are pushed to the center of the outer mold through the longitudinally arranged hydraulic rods until the two longitudinal inner mold assemblies are contacted with the homo-polypropylene solid sphere to be foamed, and finally the two transverse inner mold assemblies are pushed to the center of the outer mold through the transversely arranged hydraulic rodsUntil it contacts with the solid sphere to be foamed of the homopolymerized polypropylene;
step two: after the first step, the foaming agent gas CO is discharged through the vent hole 2 Injecting into the inner cavity until the pressure in the inner cavity reaches 15MPa (saturation pressure P s )；
Step three: after the second step, the solid homo-polypropylene sphere to be foamed is continuously placed in an inner die cavity with the temperature of 125 ℃ and the pressure of 15MPa to be saturated for 84.85 hours (saturation time t s ) So that the foaming agent gas is completely saturated in the sphere to be foamed;
step four: after the step three is finished, the temperature of the inner die is controlled to 145 ℃ through a temperature control system (foaming temperature T) f )；
Step five: after the step four is finished, continuously placing the solid homo-polypropylene sphere to be foamed in an internal mold cavity with the temperature of 145 ℃ and the pressure of 15MPa, and heating for 54.5min (heating time t f ) So that a temperature gradient is formed inside the sphere to be foamed;
step six: and fifthly, after the step of finishing, moving the upper and lower longitudinal inner mold assemblies and the left and right transverse inner mold assemblies to the notch of the outer mold through the hydraulic rod, so that the homo-polypropylene solid sphere to be foamed foams in the spherical outer mold cavity, and obtaining the foamed Luneberg lens with the diameter of 150mm and the relative dielectric constant continuously changing.
Example 3: method for preparing foaming Bo lens
The embodiment provides a method for preparing a foaming Lasiosphaera lens, which uses a foaming mold (diameter of a homo-polypropylene solid sphere to be foamed is 220mm, a foaming mold with an inner diameter of 300mm and an inscribed circle diameter of an inner mold cavity of 220mm is selected, and when the foaming mold is in an initial state, an upper longitudinal inner mold component, a lower longitudinal inner mold component, a left transverse inner mold component and a right transverse inner mold component are positioned at a notch of an outer mold) in the embodiment 1-1;
the method comprises the following steps (as shown in fig. 2):
step one: the temperature of the inner die cavity is controlled to be 130 ℃ (saturation temperature T) by a temperature control system s ) The method comprises the steps of carrying out a first treatment on the surface of the Opening the outer mould, and firstly, making the homo-polypropylene solidSphere to be foamed (T) m 155 ℃ and 220mm in diameter) are placed in the lower longitudinal inner die assembly, then the two longitudinal inner die assemblies are pushed to the center of the outer die through a longitudinally arranged hydraulic rod until the two longitudinal inner die assemblies are contacted with the homo-polypropylene solid sphere to be foamed, and finally the two transverse inner die assemblies are pushed to the center of the outer die through a transversely arranged hydraulic rod until the two transverse inner die assemblies are contacted with the homo-polypropylene solid sphere to be foamed;
step two: after the first step, the foaming agent gas CO is discharged through the vent hole 2 Injecting into the inner cavity until the pressure in the inner cavity reaches 15MPa (saturation pressure P s )；
Step three: after the second step, the solid homo-polypropylene sphere to be foamed is continuously placed in an inner die cavity with the temperature of 130 ℃ and the pressure of 15MPa to be saturated for 290 hours (saturation time t s ) So that the foaming agent gas is completely saturated in the sphere to be foamed;
step four: after the step three is finished, the temperature of the inner die is controlled to 145 ℃ through a temperature control system (foaming temperature T) f )；
Step five: after the step four is finished, continuously placing the solid homo-polypropylene sphere to be foamed in an internal mold cavity with the temperature of 145 ℃ and the pressure of 15MPa, and heating for 110min (heating time t f ) So that a temperature gradient is formed inside the sphere to be foamed;
step six: and fifthly, after the step of finishing, moving the upper and lower longitudinal inner mold assemblies and the left and right transverse inner mold assemblies to the notch of the outer mold through the hydraulic rod, so that the homo-polypropylene solid sphere to be foamed is foamed in the spherical outer mold cavity, and the foamed Luneberg lens with the diameter of 300mm and the relative dielectric constant continuously changing is obtained.
Example 4: method for preparing foaming Bo lens
The embodiment provides a method for preparing a foaming Lasiosphaera lens, which uses a foaming mold (the diameter of a polyphenyl ether solid sphere to be foamed is 109mm, a foaming mold with an inner diameter of 150mm of an outer mold and an inscribed circle diameter of an inner mold cavity of 109mm is selected, and when the foaming mold is in an initial state, an upper longitudinal inner mold component, a lower longitudinal inner mold component and a left transverse inner mold component and a right transverse inner mold component are positioned at a notch of an outer mold) in the embodiment 1-1;
the method comprises the following steps:
step one: the temperature of the inner die cavity is controlled to 140 ℃ (saturation temperature T) by a temperature control system s ) The method comprises the steps of carrying out a first treatment on the surface of the The outer mould is opened, the polyphenyl ether solid sphere (T) g 150 ℃ and 109mm in diameter) are placed in the lower longitudinal inner mold assemblies, then the two longitudinal inner mold assemblies are pushed to the center of the outer mold through a longitudinally arranged hydraulic rod until the two longitudinal inner mold assemblies are contacted with the polyphenyl ether solid sphere to be foamed, and finally the two transverse inner mold assemblies are pushed to the center of the outer mold through a transversely arranged hydraulic rod until the two transverse inner mold assemblies are contacted with the polyphenyl ether solid sphere to be foamed;
step two: after the first step, the foaming agent gas CO is discharged through the vent hole 2 Injecting into the inner cavity until the pressure in the inner cavity reaches 15MPa (saturation pressure P s )；
Step three: after the second step, continuously placing the polyphenyl ether solid sphere to be foamed in an inner die cavity with the temperature of 140 ℃ and the pressure of 15MPa to saturate for 84.85 hours (saturation time t s ) So that the foaming agent gas is completely saturated in the sphere to be foamed;
step four: after the third step is finished, the temperature of the inner die is controlled to be 165 ℃ (foaming temperature T) through a temperature control system f )；
Step five: after the step four is finished, continuously placing the polyphenyl ether solid sphere to be foamed into an internal mold cavity with the temperature of 165 ℃ and the pressure of 15MPa, and heating for 54.5min (heating time t f ) So that a temperature gradient is formed inside the sphere to be foamed;
step six: and fifthly, after the step five is finished, the upper and lower longitudinal inner mold assemblies and the left and right transverse inner mold assemblies are moved to the notch of the outer mold through the hydraulic rod, so that the polyphenyl ether solid sphere to be foamed is foamed in the spherical outer mold cavity, and the foamed Luneberg lens with the diameter of 150mm and the relative dielectric constant continuously changing is obtained.
Example 5: method for preparing foaming Bo lens
The implementation isExample a method for producing a foamed luneberg lens is provided, which method is based on example 2, by bringing the saturation temperature T s Adjust to 115 ℃ and saturation pressure P s Adjusting the foaming temperature to 20MPa and T f The temperature was adjusted to 140 ℃.
Example 6: method for preparing foaming Bo lens
This example provides a method for preparing a foamed Luneberg lens by combining the saturation temperature T on the basis of example 2 s Regulating to 140 deg.C and saturation pressure P s Adjusting the foaming temperature to 10MPa and T f The temperature was adjusted to 155 ℃.
Comparative example 1: method for preparing foaming Bo lens
This comparative example provides a method for preparing a foamed luneberg lens by combining the saturation temperature T on the basis of example 2 s The temperature was adjusted to 155 ℃.
Comparative example 2: method for preparing foaming Bo lens
This comparative example provides a process for the preparation of a foamed Luneberg lens by combining, on the basis of example 2, a foaming temperature T f The temperature was adjusted to 130 ℃.
Comparative example 3: method for preparing foaming Bo lens
This comparative example provides a process for the preparation of a foamed Luneberg lens by combining, on the basis of example 2, a foaming temperature T f The temperature was adjusted to 170 ℃.
Comparative example 4: method for preparing foaming Bo lens
This comparative example provides a method of preparing a foamed luneberg lens by replacing the foaming mold with a foaming mold without an inner mold on the basis of example 2; the foaming mold consists of a spherical mold (made of stainless steel) with an inner diameter of 150mm and a temperature control system; a spherical die cavity for foaming the sphere to be foamed is arranged in the spherical die; the spherical mold is arranged in an openable and closable manner, and two vent pipes are inserted into the spherical mold; the ventilation pipe is controlled by a valve; the diameter of the vent pipe is 32mm; the spherical mold comprises a spherical mold body and a spherical mold body, wherein the spherical mold body is internally provided with a cavity for accommodating heating oil; the temperature control system is a mold temperature machine; the heating rod of the die temperature machine is inserted with heating oil from the outside of the shell of the spherical die to heat the heating oil, and the heat obtained by the heating oil is transferred to the whole spherical die through heat so as to control the temperature of the spherical die cavity.
Experimental example 1: performance experiments of foaming Luneberg lenses
The relative dielectric constants of the foamed puffball lenses prepared in examples 2 to 6 and comparative examples 1 to 4 at different radii were examined, and the examination results are shown in fig. 3. The internal structure of the foamed lobster lens prepared in example 2 was observed using an electron microscope, and the observation result is shown in fig. 4.
As can be seen from fig. 3 to 4, the relative dielectric constants of the foamed cobs prepared by the methods of examples 2 to 6 can be changed regularly. Comparative example 1 has a saturation temperature too high, so that the sphere to be foamed cannot maintain a spherical shape, and the polymer is completely in contact with the lower longitudinal inner mold during saturation, and the polymer in contact with the lower longitudinal inner mold after foaming is excessively foamed, so that the lower half has a lower dielectric constant, and the upper half has a higher dielectric constant, so that serious decentration is caused, the relative dielectric constant in the longitudinal direction is reduced by 'cliff' around the normalized radius of 0.3, and the relative dielectric constant in the transverse direction is entirely lower by not more than 1.3. The foaming temperature of comparative example 2 was too low, resulting in a higher outer density, and thus a higher outer dielectric constant, and a lower relative dielectric constant. The foaming temperature of comparative example 3 was too high, the density was high because the outermost melt strength was low, cells could not be supported, the dielectric constant was high, and the density was low because the foaming temperature was high, resulting in low dielectric constant, and finally low relative dielectric constant overall, and the relative dielectric constant was lower than 1 at the near-outer side. Comparative example 4 since the mold of example 1 was not used, only the lower half in contact with the outer mold had a good density distribution while the upper half in contact with the blowing agent gas had insufficient heat transfer, resulting in a higher overall density, a higher dielectric constant, and a relative dielectric constant approaching 1 when a temperature gradient was formed.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (10)
1. A method of making a foamed cobra lens, the method using a foaming mold; the foaming mold comprises an inner mold and an outer mold; the inner mold comprises a plurality of inner mold components; the inner die assembly can be combined into a spherical body with an inner die cavity; the inner mould cavity is used for accommodating the sphere to be foamed and the foaming agent gas; the outer die is provided with a plurality of notches corresponding to the inner die assembly; the outer die and the inner die assembly can be combined into a spherical body with a spherical outer die cavity inside; the outer mold cavity is used for foaming the sphere to be foamed;
the method comprises the following steps:
step one: placing the sphere to be foamed into an inner die cavity, and controlling the temperature of the inner die cavity to be the saturation temperature T s ；
Step two: after the step one is finished, injecting the foaming agent gas into the inner die cavity until the pressure in the inner die cavity reaches the saturation pressure P s ；
Step three: after the second step is finished, continuously placing the sphere to be foamed at a saturation temperature T s The pressure is the saturation pressure P s Until the foaming agent gas is completely saturated in the sphere to be foamed; the time for the foaming agent gas to be fully saturated in the sphere to be foamed is the saturation time t s ；
Step four: after the third step is finished, the temperature of the inner die cavity is controlled to be the foaming temperature T f ；
Step five: after the fourth step, continuously placing the sphere to be foamed at a foaming temperature T f The pressure is the saturation pressure P s Until the interior of the sphere to be foamed is formedA temperature gradient; the time for forming the temperature gradient in the sphere to be foamed is the temperature rise time t f ；
Step six: and fifthly, after the step of finishing, moving the inner mold assembly to the notch of the outer mold so that the sphere to be foamed foams in the spherical outer mold cavity to obtain the foamed Luneberg lens.
2. The method of claim 1, wherein the outer mold inner diameter is calculated as:
wherein d out The inner diameter of the outer die is in mm; d, d ball The diameter of the sphere to be foamed is in mm;
the diameter of the inscribed circle of the inner die cavity is equal to the diameter of the sphere to be foamed.
3. A method according to claim 1 or 2, characterized in that the material of the sphere to be foamed is an amorphous polymer or a semi-crystalline polymer; the amorphous polymer is one or more of polyphenyl ether, polycarbonate, polystyrene and polymethyl methacrylate; the semi-crystalline polymer is one or more of polypropylene, polyethylene, polybutylene, polylactic acid, polyethylene terephthalate, liquid crystal polyester, nylon 6 and nylon 66.
4. A method according to claim 3, characterized in that when the sphere to be expanded is an amorphous polymer, the saturation temperature T s ＝T g -50℃～T g The method comprises the steps of carrying out a first treatment on the surface of the Wherein T is g Glass transition temperature of amorphous polymer;
when the sphere to be expanded is a semi-crystalline polymer, the saturation temperature T s ＝T m -100℃～T m -20 ℃; wherein T is m Is the melting temperature of the semi-crystalline polymer.
5. The method according to any one of claims 1 to 4, wherein the saturation pressure P s ＝5～20MPa。
6. The method according to any one of claims 1 to 5, wherein the saturation time t s ≥a×(d/2) 1.75 ；
In the formula, the saturation time t s In hours, a= 0.07762 hours/mm 1.75 D is the diameter of the foam sphere, and the unit is mm.
7. A method according to claim 3, characterized in that when the sphere to be foamed is an amorphous polymer, the foaming temperature Tf = T g +10℃～T g +100℃; wherein T is g Glass transition temperature of amorphous polymer;
when the sphere to be foamed is a semi-crystalline polymer, the foaming temperature T f ＝T m -15℃～T m +10℃; wherein T is m Is the melting temperature of the semi-crystalline polymer.
8. The method according to any one of claims 1 to 7, wherein the temperature rise time t f ＝d ball /2；
In the heating time t f Is in minutes; d, d ball The diameter of the sphere to be foamed is in mm.
9. A foamed cobra lens, characterized in that it is produced by the method of any one of claims 1 to 8.
10. Use of the method of any one of claims 1 to 8 for the preparation of a foamed lobster lens.
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