阅读说明：本技术 一种超低密度、隔热、隔音的微发泡pmma复合材料及其制备方法 (Micro-foaming PMMA composite material with ultralow density, heat insulation and sound insulation and preparation method thereof ) 是由 徐凯华 徐小虎 王凡 张欣 付飞 管卫华 于 2021-08-09 设计创作，主要内容包括：本发明涉及了一种超低密度、隔热、隔音的微发泡PMMA复合材料及其制备方法,具体由以下重量份的原料组成：PMMA树脂50-80份,天然纤维填充体15-30份、超支化聚酯树脂5-15份,高效发泡剂2-8份,高效结晶成核剂0.5-3份。本发明的有益效果在于：凭借PMMA树脂的高熔体粘数特性,以及超支化聚酯树脂和高效成核剂的协助,成功在双螺杆注塑成型机中实现了高发泡倍率(1～1.5)的化学法微发泡注塑成型,再辅以低密度的天然纤维,从而获得了超低密度(≤0.6g/cm～(3))、低孔径、高孔密度的微发泡PMMA复合材料,理想的泡孔结构还赋予了材料良好的隔热、隔音等优异特性。(The invention relates to an ultra-low density, heat insulation and sound insulation micro-foaming PMMA composite material and a preparation method thereof, and the composite material is specifically composed of the following raw materials in parts by weight: 50-80 parts of PMMA resin, 15-30 parts of natural fiber filler, 5-15 parts of hyperbranched polyester resin, 2-8 parts of efficient foaming agent and 0.5-3 parts of efficient crystallization nucleating agent. The invention has the beneficial effects that: by means of the high melt viscosity of PMMA resin and the assistance of hyperbranched polyester resin and efficient nucleating agent, the chemical micro-foaming with high foaming ratio (1-1.5) is successfully realized in a double-screw injection molding machineInjection molding, and adding low-density natural fiber to obtain ultralow density (less than or equal to 0.6 g/cm) 3 ) The ideal cell structure of the micro-foamed PMMA composite material with low aperture and high cell density also endows the material with excellent characteristics of heat insulation, sound insulation and the like.)

1. A micro-foaming PMMA composite material with ultra-low density, heat insulation and sound insulation and a preparation method thereof are characterized in that: the feed comprises the following raw materials in parts by weight:

2. the ultra-low density, thermal and acoustical insulation micro-foamed PMMA composite material and its preparation method of claim 1, wherein: the PMMA resin is low-melting-index and high-viscosity extrusion grade polymethyl methacrylate, the melt index MFR of the PMMA resin is less than or equal to 1g/10min under the test conditions of 230 ℃ and 3.8kg, and the transmissivity (3150 mu m) is less than or equal to 90 percent.

3. The ultra-low density, thermal and acoustical insulation micro-foamed PMMA composite material and its preparation method of claim 1, wherein: the natural fiber is lignin fiber prepared based on natural plant cellulose, the length-diameter ratio L/D is 2: 1-5: 1, and the fiber diameter is 200-.

4. The ultra-low density, thermal and acoustical insulation micro-foamed PMMA composite material and its preparation method of claim 1, wherein: the hyperbranched polyester resin is aliphatic polyester which is synthesized based on hydroxyl-terminated hyperbranched and has a dendritic molecular structure, wherein the number of hydroxyl groups in molecules is more than or equal to 20/mol, and the molecular weight is more than or equal to 2400 g/mol.

5. The ultra-low density, thermal and acoustical insulation micro-foamed PMMA composite material and its preparation method of claim 1, wherein: the efficient foaming agent is a heat absorption type environment-friendly efficient bicarbonate inorganic foaming agent.

6. The ultra-low density, thermal and acoustical insulation micro-foamed PMMA composite material and its preparation method of claim 1, wherein: the efficient crystallization nucleating agent is an organic/inorganic compound polyester special nucleating agent based on long-chain saturated linear calcium carboxylate salt.

7. The method for preparing an ultra-low density, thermal and acoustical insulating micro-foamed PMMA composite according to any one of claims 1 to 6, comprising the steps of:

(1) respectively weighing PMMA resin, hyperbranched polyester resin and high-efficiency crystallization nucleating agent according to the weight parts, and uniformly mixing to obtain a mixed raw material;

(2) placing the dried mixed raw materials into a main feeding bin of a double-screw extruder which is tightly meshed and rotates in the same direction, and adding the dried mixed raw materials into a machine barrel of the extruder through a feeding screw; weighing the natural fibers according to the weight parts, placing the natural fibers in a side feeding bin of an extruder, and adding the natural fibers into an extruder barrel through a side feeding screw. The diameter of the used twin-screw extruder is 30mm, the length-diameter ratio L/D is 44, and the temperature of each subarea from the feed inlet to the head outlet of the main machine barrel is set as follows: 185 ℃, 205 ℃, 210 ℃, 220 ℃, 230 ℃, 220 ℃, 215 ℃, 220 ℃ and the rotating speed of a main machine is 250 revolutions per minute, and a matrix resin product of the PMMA composite material is obtained after the processes of melt extrusion, granulation, drying treatment and the like;

(3) weighing the high-efficiency foaming agent according to the weight parts, putting the high-efficiency foaming agent and the matrix resin of the obtained PMMA composite material into a high-speed stirring mixer, uniformly stirring for 10min at the stirring speed of 300 r/min, and obtaining the micro-foaming PMMA composite material with ultralow density, heat insulation and sound insulation.

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a micro-foaming PMMA composite material with ultralow density, heat insulation and sound insulation and a preparation method thereof.

Background

With the rapid iterative update of products in the common fields of polymer materials such as automobiles, household appliances and the like in recent years, the requirements on the aspects of high performance, multi-functionalization and the like of the used polymer materials are more and more diversified, particularly, the current light-weight and environment-friendly 'low carbon emission' green development concept is increasingly deep, higher weight reduction requirements are put forward on key indexes of raw materials for parts in the fields of automobiles, household appliances, industrial electronic appliances and the like, and certain light-weight and low-density materials such as high-performance polyolefin composite materials are matched with special molding processes (micro-foaming extrusion, micro-foaming injection molding, micro-foaming mold pressing and the like) and are initially popularized and applied to large structural members or functional members such as automobile bumpers, lower edge decorative plates, instrument panels, frameworks, door decorative plates, front end frames, skylight frames and the like in the target field, therefore, the automobile light-weight testing device becomes one of the hot areas of the current automobile light-weight research.

However, the micro-foaming molding method has a very high requirement on the melt viscosity number of the polymer, often requires that the polymer molecular chain has a side chain group with a larger volume, and common general plastics such as polypropylene PP are long straight chain structures, and a single side methyl structure is not enough to form chain winding with sufficient strength, so that the polypropylene material special for micro-foaming injection molding is developed based on specially synthesized high melt strength polypropylene (HMSPP), which not only increases the technical development difficulty of the material, but also greatly increases the material cost. Polymethyl methacrylate (PMMA), also known as acrylic, is a general-purpose plastic with long flexible molecular chains and bulky side chain groups, has a significantly better high-viscosity melt performance, and has a material cost only slightly higher than that of conventional polypropylene and far lower than that of high-viscosity meltMelt strength polypropylene (HMSPP), which provides an excellent innate basis for the development of specialized micro-foamed PMMA materials. In spite of the research on the micro-foamed PMMA composite material and similar polyester materials, most of the research focuses on physical micro-foaming (i.e. supercritical fluid) rather than chemical methods (additional chemical foaming agents) with wider application range and lower cost. For example, the light-weight high-strength heat-insulating PMMA foamed composite material described in CN106084274A realizes the micro-foaming molding effect of a nano-scale pore structure by matching supercritical carbon dioxide fluid in a high-pressure reaction kettle with aerogel; in CN106566156A, a supercritical carbon dioxide fluid foaming method in a high-pressure reaction kettle is also adopted to obtain a PMMA nano foaming composite material with an excellent structure; CN108948623A used supercritical nitrogen fluid as the blowing agent. It can be seen that the supercritical fluid method (physical method) has a small pore diameter (8 to 10 μm) and a high pore density (2.0X 10)⁹cells/cm³Even higher), however, as a very special physical state, not only a highly-closed high-pressure reactor is required as a reaction vessel, but also the fluid generation device is very complex, and the stability requirement is very high, so that the development cost of the material is always high, and the technical characteristics of high degree, high precision and sharp degree are difficult to match with the application fields of wide coverage and complex operation environment, such as automobiles, household appliances, industrial electrical appliances and the like, so that the development of the PMMA micro-foaming material with excellent cell structure and outstanding key characteristics is very important based on the more conventional and wider application process route of chemical method and micro-foaming injection molding.

Disclosure of Invention

The invention aims to make up the blank of the prior art and provide a micro-foaming PMMA composite material with ultra-low density, heat insulation and sound insulation, aiming at the current situation that most of the prior technical schemes concentrate on supercritical fluid physical foaming with low application degree and high modification cost, the invention selects high-viscosity extrusion-grade PMMA matrix resin, and then matches with a hyperbranched polyester material with a special dendritic molecular chain structure and an efficient crystallization nucleating agent, thereby constructing a polymer system suitable for chemical micro-foaming injection molding, and then matches with a natural fiber filler with low density and excellent characteristics, thereby obtaining the PMMA composite material with ideal foam structure, greatly reduced density and outstanding heat and sound insulation characteristics.

The invention is realized by the following technical scheme:

an ultra-low density, heat insulation and sound insulation micro-foaming PMMA composite material and a preparation method thereof comprise the following raw materials in parts by weight:

in the micro-foamed PMMA composite material,

the PMMA resin is low-melting-index high-viscosity extrusion grade polymethyl methacrylate, the melt index MFR of the PMMA resin is less than or equal to 1g/10min under the test conditions of 230 ℃ and 3.8kg, and the transmissivity (3150 mu m) is less than or equal to 90%.

The natural fiber is lignin fiber prepared based on natural plant cellulose, the length-diameter ratio L/D is 2: 1-5: 1, and the fiber diameter is 200-.

The hyperbranched polyester resin is aliphatic polyester which is synthesized based on hydroxyl-terminated hyperbranched and has a dendritic molecular structure, wherein the number of hydroxyl groups in molecules is more than or equal to 20/mol, and the molecular weight is more than or equal to 2400 g/mol.

The efficient foaming agent is a heat absorption type environment-friendly efficient bicarbonate inorganic foaming agent.

The efficient crystallization nucleating agent is an organic/inorganic compound polyester special nucleating agent based on long-chain saturated linear calcium carboxylate salt.

The second purpose of the invention is to provide a micro-foamed PMMA composite material with ultralow density, heat insulation and sound insulation and a preparation method thereof, which is characterized by comprising the following steps:

(1) and weighing the PMMA resin, the hyperbranched polyester resin and the efficient crystallization nucleating agent according to the parts by weight, and uniformly mixing to obtain the mixed raw material.

(2) Placing the dried mixed raw materials into a main feeding bin of a double-screw extruder which is tightly meshed and rotates in the same direction, and adding the dried mixed raw materials into a machine barrel of the extruder through a feeding screw; weighing the natural fibers according to the weight parts, placing the natural fibers in a side feeding bin of an extruder, and adding the natural fibers into an extruder barrel through a side feeding screw. The diameter of the used twin-screw extruder is 30mm, the length-diameter ratio L/D is 44, and the temperature of each subarea from the feed inlet to the head outlet of the main machine barrel is set as follows: 185 ℃, 205 ℃, 210 ℃, 220 ℃, 230 ℃, 220 ℃, 215 ℃, 220 ℃ and the rotation speed of a main machine is 250 r/min, and the base resin product of the PMMA composite material is obtained after the processes of melt extrusion, granulation, drying treatment and the like.

(3) Weighing the high-efficiency foaming agent according to the weight parts, putting the high-efficiency foaming agent and the matrix resin of the obtained PMMA composite material into a high-speed stirring mixer, uniformly stirring for 10min at the stirring speed of 300 r/min, and obtaining the micro-foaming PMMA composite material with ultralow density, heat insulation and sound insulation.

Compared with the prior art, the invention has the following beneficial effects:

1. based on the characteristics that PMMA has large side chain groups and high chain winding, low-melting-point extrusion-grade PMMA resin with higher viscosity and better melt strength is further optimized, and then hyperbranched polyester resin with the number of high-end hydroxyl groups (more than or equal to 20/mol) is supplemented, so that the wrapping capacity of carbon dioxide bubbles decomposed by a foaming agent in the injection molding process is greatly enhanced, and the high-efficiency nucleating agent matched with the PMMA resin can promote the quick cooling and shaping of the PMMA resin, thereby effectively preventing the merging and opening phenomena of micro bubbles in the melt cooling process, and further improving the micro-bubble conditions in the PMMA composite material.

2. On the basis of good performance of micro-foaming injection molding, the scheme of the invention also matches and uses the natural fiber filler with the density far lower than that of other inorganic fillers, not only further improves the weight reduction performance of the PMMA composite material, but also can further enhance the key characteristics of heat insulation, sound insulation and the like of the composite material by the porous structure of the natural fiber.

3. The PMMA alloy material obtained by the technical scheme of the invention has excellent micro-foaming injection molding performance and excellent characteristics (porosity, low specific gravity and filling increase) of the used natural fiber fillerStrong, etc.), not only the density of the material after foaming can be greatly reduced to 0.45-0.6 g/cm³On the left and right sides, key characteristic indexes such as heat conduction coefficient, average sound absorption coefficient and the like are improved and promoted obviously; further testing the microstructure of PMMA composite material shows that the pore diameter of the pores can reach 9.5 mu m, and the average pore density can reach 1.95 multiplied by 10⁹cells/cm³The two key foaming indexes are close to the level of physical method (supercritical fluid) micro-foaming which is researched more at present, and the method is a lightweight and functionalized PMMA modification method which is simpler and more convenient in device, easy to realize, lower in modification cost and extremely wide in application field.

Detailed Description

The invention is further illustrated by the following specific examples, which are intended to be illustrative only and not limiting.

The raw materials used in the embodiment of the invention are as follows:

PMMA-1: polymethyl methacrylate (PMMA) TD542, a melt index MFR of 0.9g/10min at 230 ℃ under a test condition of 3.8kg, a transmittance (3150 μm) of 89%, and a melt viscosity of celluloid color International chemical Co., Ltd.

PMMA-2: polymethyl methacrylate Frosted DR, melt index MFR of 0.5g/10min at 230 ℃ under the test conditions of 3.8kg, transmittance (3150 μm) of 85%, Acomata group, France.

Natural fibers: natural fiber Symbio P10 prepared based on lignocellulose has the length-diameter ratio L/D of 3:1, the fiber diameter of 260-.

Hyperbranched polyester resin-1: hydroxyl-terminated hyperbranched polyester tree Hyper H203, white powder, 20-24/mol of hydroxyl in molecules, 2600g/mol of molecular weight, Wuhan hyperbranched resin science and technology Limited.

Hyperbranched polyester resin-2: hyperbranched polyester tree H40P, white powder, 35/mol of hydroxyl group in the molecule, 7103.1 of molecular weight, Wehaichen molecular New Material Co.

High-efficiency foaming agent: a complex bicarbonate foaming agent is prepared from aminoguanidine bicarbonate: citric acid is compounded according to the proportion of 5:1, white ultrafine powder with the average grain diameter of 10-15 microns, and environment-friendly science and technology Limited, Wandebeng of Jinan, Ji.

Efficient crystallization nucleating agent: calcium salt of long-chain saturated linear carboxylic acid (montanic acid), Licomont NAV 101, white amorphous powder, craine catalyst (shanghai) ltd.

And (3) product performance testing:

micro-foaming test: the method is carried out in a Haitian HTDZ HT-280 double-screw injection molding machine, the temperature of each injection section is respectively 200 ℃, 210 ℃, 220 ℃ and 220 ℃, the mold temperature is kept at 80 ℃, and a two-section low-pressure injection molding process of mold-core retraction is adopted to carry out injection molding to obtain a standard test sample strip.

Density: the test was carried out according to the standard method indicated in ISO1183-1, with test specimen dimensions of 10X 4mm, at normal temperature (23 ℃).

Heat conduction performance: a test specimen having a size of 160X 120X 3.2mm was injection-molded according to the transient planar heat source method of ISO22007-2, and the heat transfer coefficients in the parallel direction (/) and the perpendicular direction (.

Sound insulation performance: according to the standard method shown in ISO354, a wafer with the size of phi 80 multiplied by 4mm is injected, a JTZB-standing wave tube sound absorption coefficient tester is adopted, vertical incidence is carried out, the sound absorption coefficients of the test sample are measured when the frequency is 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz and 4000Hz, and the arithmetic mean value is calculated to obtain the average sound absorption coefficient.

And (3) characterizing a cell structure: cutting a sample strip section with the size of 80 multiplied by 10 multiplied by 4mm in an environment with the temperature of minus 30 ℃, carrying out gold spraying on the section on a KYKY-EM6200 scanning electron microscope, respectively testing the aperture of the micropores with the magnification of 500 times, and carrying out statistical calculation to obtain the pore density.

Example 1

The PMMA resin, the hyperbranched polyester resin and the high-efficiency crystallization nucleating agent are respectively weighed according to the weight parts according to the data of example 1 shown in the table 1, and are uniformly mixed to obtain the mixed raw material.

Placing the dried mixed raw materials into a main feeding bin of a double-screw extruder which is tightly meshed and rotates in the same direction, and adding the dried mixed raw materials into a machine barrel of the extruder through a feeding screw; weighing the natural fibers according to the weight parts, placing the natural fibers in a side feeding bin of an extruder, and adding the natural fibers into an extruder barrel through a side feeding screw. The diameter of the used twin-screw extruder is 30mm, the length-diameter ratio L/D is 44, and the temperature of each subarea from the feed inlet to the head outlet of the main machine barrel is set as follows: 185 ℃, 205 ℃, 210 ℃, 220 ℃, 230 ℃, 220 ℃, 215 ℃, 220 ℃ and the rotation speed of a main machine is 250 r/min, and the base resin product of the PMMA composite material is obtained after the processes of melt extrusion, granulation, drying treatment and the like.

Weighing the high-efficiency foaming agent according to the weight parts, putting the high-efficiency foaming agent and the matrix resin of the obtained PMMA composite material into a high-speed stirring mixer, uniformly stirring for 10min at the stirring speed of 300 r/min, and obtaining the micro-foaming PMMA composite material with ultralow density, heat insulation and sound insulation.

Example 2

The PMMA resin, the hyperbranched polyester resin and the high-efficiency crystallization nucleating agent are respectively weighed according to the weight parts according to the data of the example 2 shown in the table 1, and are uniformly mixed to obtain the mixed raw material.

Placing the dried mixed raw materials into a main feeding bin of a double-screw extruder which is tightly meshed and rotates in the same direction, and adding the dried mixed raw materials into a machine barrel of the extruder through a feeding screw; weighing the natural fibers according to the weight parts, placing the natural fibers in a side feeding bin of an extruder, and adding the natural fibers into an extruder barrel through a side feeding screw. The diameter of the used twin-screw extruder is 30mm, the length-diameter ratio L/D is 44, and the temperature of each subarea from the feed inlet to the head outlet of the main machine barrel is set as follows: 185 ℃, 205 ℃, 210 ℃, 220 ℃, 230 ℃, 220 ℃, 215 ℃, 220 ℃ and the rotation speed of a main machine is 250 r/min, and the base resin product of the PMMA composite material is obtained after the processes of melt extrusion, granulation, drying treatment and the like.

Weighing the high-efficiency foaming agent according to the weight parts, putting the high-efficiency foaming agent and the matrix resin of the obtained PMMA composite material into a high-speed stirring mixer, uniformly stirring for 10min at the stirring speed of 300 r/min, and obtaining the micro-foaming PMMA composite material with ultralow density, heat insulation and sound insulation.

TABLE 1 formulation of ultra low density, thermal and acoustical insulation micro-foamed PMMA composite materials (unit: gram)

	Example 1	Example 2	Example 3	Example 4	Example 5
						PMMA-1	61.5		61	60	60
PMMA-2		65
						Natural fiber	30	15	20	20	20
Hyperbranched polyester resin-1	5		10		12
						Hyperbranched polyester resin-2		15		12
High-efficiency foaming agent	3	2	8	6	6
						High-efficiency crystallization nucleating agent	0.5	3	1	2	2

Example 3

The PMMA resin, the hyperbranched polyester resin and the high-efficiency crystallization nucleating agent are respectively weighed according to the weight parts according to the data of the example 3 shown in the table 1, and are uniformly mixed to obtain the mixed raw material.

Placing the dried mixed raw materials into a main feeding bin of a double-screw extruder which is tightly meshed and rotates in the same direction, and adding the dried mixed raw materials into a machine barrel of the extruder through a feeding screw; weighing the natural fibers according to the weight parts, placing the natural fibers in a side feeding bin of an extruder, and adding the natural fibers into an extruder barrel through a side feeding screw. The diameter of the used twin-screw extruder is 30mm, the length-diameter ratio L/D is 44, and the temperature of each subarea from the feed inlet to the head outlet of the main machine barrel is set as follows: 185 ℃, 205 ℃, 210 ℃, 220 ℃, 230 ℃, 220 ℃, 215 ℃, 220 ℃ and the rotation speed of a main machine is 250 r/min, and the base resin product of the PMMA composite material is obtained after the processes of melt extrusion, granulation, drying treatment and the like.

Weighing the high-efficiency foaming agent according to the weight parts, putting the high-efficiency foaming agent and the matrix resin of the obtained PMMA composite material into a high-speed stirring mixer, uniformly stirring for 10min at the stirring speed of 300 r/min, and obtaining the micro-foaming PMMA composite material with ultralow density, heat insulation and sound insulation.

Example 4

The PMMA resin, the hyperbranched polyester resin and the high-efficiency crystallization nucleating agent are respectively weighed according to the weight parts according to the data of example 4 shown in the table 1, and are uniformly mixed to obtain the mixed raw material.

Placing the dried mixed raw materials into a main feeding bin of a double-screw extruder which is tightly meshed and rotates in the same direction, and adding the dried mixed raw materials into a machine barrel of the extruder through a feeding screw; weighing the natural fibers according to the weight parts, placing the natural fibers in a side feeding bin of an extruder, and adding the natural fibers into an extruder barrel through a side feeding screw. The diameter of the used twin-screw extruder is 30mm, the length-diameter ratio L/D is 44, and the temperature of each subarea from the feed inlet to the head outlet of the main machine barrel is set as follows: 185 ℃, 205 ℃, 210 ℃, 220 ℃, 230 ℃, 220 ℃, 215 ℃, 220 ℃ and the rotation speed of a main machine is 250 r/min, and the base resin product of the PMMA composite material is obtained after the processes of melt extrusion, granulation, drying treatment and the like.

Weighing the high-efficiency foaming agent according to the weight parts, putting the high-efficiency foaming agent and the matrix resin of the obtained PMMA composite material into a high-speed stirring mixer, uniformly stirring for 10min at the stirring speed of 300 r/min, and obtaining the micro-foaming PMMA composite material with ultralow density, heat insulation and sound insulation.

Example 5

The PMMA resin, the hyperbranched polyester resin and the high-efficiency crystallization nucleating agent are respectively weighed according to the weight parts according to the data of example 5 shown in the table 1, and are uniformly mixed to obtain the mixed raw material.

Placing the dried mixed raw materials into a main feeding bin of a double-screw extruder which is tightly meshed and rotates in the same direction, and adding the dried mixed raw materials into a machine barrel of the extruder through a feeding screw; weighing the natural fibers according to the weight parts, placing the natural fibers in a side feeding bin of an extruder, and adding the natural fibers into an extruder barrel through a side feeding screw. The diameter of the used twin-screw extruder is 30mm, the length-diameter ratio L/D is 44, and the temperature of each subarea from the feed inlet to the head outlet of the main machine barrel is set as follows: 185 ℃, 205 ℃, 210 ℃, 220 ℃, 230 ℃, 220 ℃, 215 ℃, 220 ℃ and the rotation speed of a main machine is 250 r/min, and the base resin product of the PMMA composite material is obtained after the processes of melt extrusion, granulation, drying treatment and the like.

Weighing the high-efficiency foaming agent according to the weight parts, putting the high-efficiency foaming agent and the matrix resin of the obtained PMMA composite material into a high-speed stirring mixer, uniformly stirring for 10min at the stirring speed of 300 r/min, and obtaining the micro-foaming PMMA composite material with ultralow density, heat insulation and sound insulation.

Comparative example 1

The modified PMMA composite material HAM-8580 is commercially available from Shanghai brocade lake Rili company.

TABLE 2 test results for ultra low density, thermal and acoustical insulating micro-foamed PMMA composite

Combining the examples in Table 1 and Table 2The components and test data of the comparative example show that the high melt viscosity of the selected PMMA material and the polymer chain winding promoting effect of the hyperbranched polyester material with the special tree structure greatly enhance the bubble coating capability of the PMMA melt; the foamable property before modification (comparative example 1) was significantly poor, the cell diameter was 50 μm or more, and the cell density was only 10⁶The left and right show that the pore diameter is large and the pore density is low in the material, the pore diameter of each modified embodiment is generally 10-20 μm, the lowest pore diameter (embodiment 5) can reach 9.5 μm, and the pore density can be increased to 10 at most⁹The above (examples 4, 5) show that the microcellular structure of the PMMA material is significantly improved.

The improvement of the micro-cellular structure in the above embodiment not only greatly reduces the material density, but also achieves great improvement in heat insulation and sound insulation. The density of the material can be from 1.15g/cm³Reduced to 0.52g/cm³On the left and right sides, the expansion ratio was 1.21, and the heat conductivity in the parallel and perpendicular directions was also from 0.2 W.m^-1·K^-1Greatly reduced to the minimum of 0.02 W.m^-1·K^-1The average sound absorption coefficient was also increased from 0.51 to 0.8 or more (examples 4 and 5).

The invention discloses a micro-foaming PMMA composite material with ultra-low density, heat insulation and sound insulation and a preparation method thereof, which is a brand new PMMA composite material designed and developed based on the urgent requirements of low density, light weight and multiple functions in the fields of automobiles, household appliances, industrial electronic appliances and the like, endows the material with excellent special characteristics of heat insulation, sound absorption and noise reduction through the optimized design of a cellular structure on the premise of greatly reducing the dead weight density, and can well meet the new requirements of the PMMA composite material special for shells and decorating parts in the application field.