1. A near-infrared laser-induced local foaming method of a high polymer material is characterized by comprising the following steps: the foaming method comprises the following specific steps:

(1) one-dimensional carbon substances with photo-thermal conversion effect and inorganic compounds are proportionally configured in an organic solvent, and ultrasound is carried out for 2-3 hours at 30-40 ℃ to prepare foaming agent system solution;

(2) completely evaporating the organic solvent in a vacuum oven at 40-50 ℃ to obtain foaming additive particles;

(3) the foaming additive particles and the polymer matrix are melted and blended in an internal mixer according to the proportion and are pressed into a sample, and then a 1064nm laser marking machine is used for carrying out irradiation treatment on the sample, so that local rapid and controllable foaming of the polymer material in a laser irradiation area is realized.

2. The near-infrared laser-induced local foaming method of a polymer material according to claim 1, characterized in that: the one-dimensional carbon substance with the photo-thermal conversion effect is Carbon Nanotubes (CNTs) and Carbon Fibers (CF).

3. The near-infrared laser-induced local foaming method of a polymer material according to claim 1, characterized in that: the inorganic compound is calcium carbonate, zinc carbonate, magnesium carbonate or aluminum carbonate.

4. The near-infrared laser-induced local foaming method of a polymer material according to claim 1, characterized in that: the organic solvent is ethyl acetate, petroleum ether, ethanol and xylene.

5. The near-infrared laser-induced local foaming method of a polymer material according to claim 1, characterized in that: the high polymer matrix material is Polyethylene (PE), polypropylene (PP), Polystyrene (PS) and Polycarbonate (PC).

6. The near-infrared laser-induced local foaming method of a polymer material according to claim 1, characterized in that: the raw material components are as follows by mass:

7. the near-infrared laser-induced local foaming method of a polymer material according to claim 1, characterized in that: the laser is yttrium aluminum garnet crystal pulse laser, the laser power is set to be 10-20W, and the pulse laser wavelength is as follows: 1064 nm.

8. A near-infrared laser-induced polymer foam prepared by the method of any one of claims 1 to 7.

Background

Lightweight materials have become an important field for new material development, and foaming is the most direct means for realizing the lightening of polymer materials. The polymer foam material is a polymer-based microporous material containing a large number of cells therein. With the rapid development of the industries such as aerospace, national defense, energy, traffic, packaging, electrical appliances, sports equipment and the like, the demand for the high polymer foam material with excellent mechanical property, heat insulation, sound insulation and buffering property is more and more urgent. The green controllable preparation of high-quality foaming materials is always a difficult point in the field of polymer foaming. Conventional methods for foaming polymer materials include physical foaming and chemical foaming. Chemical blowing agents often have the disadvantages of chemical residues, low controllability, low expansion ratio and the like, while physical blowing agents also have obvious disadvantages, such as the destruction of chlorofluorocarbons to the environment, the expensive price of fluorocarbons, the flammability and the insecurity of alkanes and the like. In addition, the traditional foaming methods have a common defect that only integral foaming can be realized, but simple local controllable foaming on a micro-nano scale cannot be realized.

Different from the traditional foaming method, the laser irradiation method is to irradiate the surface of a high polymer material by using a pulse laser beam with certain wavelength and energy, the high polymer material can absorb the laser energy and convert the laser energy into heat, and the heat is subjected to a series of reactions such as melting, thermal degradation, carbonization and the like, and gas generated in the process can be partially wrapped in a high polymer melt, so that the macroscopic foaming phenomenon is caused. The laser light generally used for laser irradiation can be classified into three types according to the wavelength: near infrared laser (1064nm), green laser (532nm), and ultraviolet laser (355 nm). The near-infrared laser has low cost, is easy to control and has a prospect of large-scale application.

However, most of the current high molecular materials (polypropylene, polyethylene, etc.) have poor response to near-infrared laser, and cannot generate a series of reactions under the laser. At present, aiming at the problems, laser marking powder sensitive to laser is usually doped in the industry to improve the laser response performance of the laser marking powder, but the laser marking powder is mostly inorganic oxide, has high addition amount, is difficult to decompose, generates less gas and cannot form an obvious foaming structure.

Disclosure of Invention

The invention provides a near-infrared laser-induced local foaming method for a high polymer material, which can realize rapid and controllable foaming under laser irradiation and is suitable for application in the field of light materials in the high polymer material. The near-infrared laser-induced local foaming method for the high polymer material provided by the invention has the characteristics of low cost, quick foaming, controllable foaming structure, simple operation in the foaming process and the like.

The invention provides a near-infrared laser induced local foaming method of a high polymer material, which comprises the following specific steps:

(1) preparing one-dimensional carbon substances with photo-thermal conversion effect and inorganic compounds into an organic solvent according to a proportion, and carrying out ultrasonic treatment for 2-3 hours at the temperature of 30-40 ℃ to prepare an easy foaming agent system solution;

(2) completely evaporating the organic solvent in a vacuum oven at 40-50 ℃ to obtain foaming additive particles;

(3) and melting and blending the foaming additive particles and the polymer matrix in an internal mixer according to a proportion, and pressing into a sample. And then, carrying out irradiation treatment on the prepared sample by using a 1064nm laser marking machine, and realizing local rapid and controllable foaming of the high polymer material in a laser irradiation area by regulating and controlling conditions such as laser parameters, the ratio of one-dimensional carbon substances to inorganic compounds and the like.

The material composition comprises the following components in parts by weight:

in the present invention, the carbon substance having the photo-thermal conversion effect includes, but is not limited to, Carbon Nanotubes (CNTs) and Carbon Fibers (CF).

In the present invention, the inorganic compound is calcium carbonate, zinc carbonate, magnesium carbonate, or aluminum carbonate.

In the invention, the organic solvent is ethyl acetate, petroleum ether, ethanol and xylene.

In the present invention, the foaming additive is a mixture of a carbon substance having a photothermal conversion effect and an inorganic compound, and the ratio thereof can be adjusted according to the effect required for foaming.

The foaming additive prepared by the invention is used for lightening foaming of high polymer products under the condition of laser irradiation.

In the invention, the laser is yttrium aluminum garnet crystal pulse laser, the laser power is set to be 10-20W, and the pulse laser wavelength is as follows: 1064nm

In the present invention, the polymer material refers to all polymers with poor absorption to laser with 1064nm wavelength, including but not limited to Polyethylene (PE), polypropylene (PP), Polystyrene (PS), and Polycarbonate (PC).

The principle of the invention is as follows: (1) one-dimensional carbon substances which can easily absorb near-infrared laser energy can be constructed into a three-dimensional cooperative network structure under the condition of extremely low addition amount, and a small amount of thermal decomposition is firstly generated under the irradiation action of laser to generate gases such as carbon monoxide, carbon dioxide and the like; (2) the one-dimensional carbon substance can instantly generate a large amount of heat while absorbing the laser energy, and quickly transfer the heat to the surrounding inorganic compounds, so that the thermal decomposition phenomenon can be quickly generated, a large amount of gas can be generated, and the foaming phenomenon of the polymer matrix can be generated in the laser irradiation area; (3) the local controllable foaming of the high polymer material in the laser irradiation area is realized by regulating and controlling the conditions of laser parameters, the ratio of the one-dimensional carbon substance to the inorganic compound and the like.

The foaming additive prepared by the invention has simple process, and can realize local rapid and controllable foaming of the high polymer material by utilizing the emerging laser irradiation technology (the schematic diagram of the principle is shown in figure 1).

Compared with other traditional high polymer material foaming, the invention has the following advantages:

1. according to the method, local foaming in the laser irradiation area can be realized, and the traditional polymer material foaming technology can only realize integral foaming of the material.

2. The laser irradiation method adopted by the invention is more convenient to operate, has low energy consumption and no pollution, can foam at any position on the surface of the material, and has more flexible means. The one-dimensional carbon substance adopted by the invention is easy to construct a three-dimensional cooperative network, and has low integral addition amount and low cost. The invention carries out laser-induced foaming on the surface of the high polymer material, has regular foaming structure and visible foaming height, and has more advantages than the traditional high polymer material integral foaming technology.

3. The laser-induced foaming method adopted by the invention can effectively reduce the cost, the process procedure and the environmental pollution. The industrial, continuous, efficient and large-scale foaming of the high polymer material can be realized by utilizing a newly developed laser marking machine to perform laser-induced foaming. By regulating and controlling conditions such as laser parameters, the proportion of one-dimensional carbon substances to inorganic compounds and the like, the local rapid and controllable foaming of the high polymer material in a laser irradiation area can be realized.

Description of the drawings:

FIG. 1 is a schematic diagram of the operation of laser induced foaming.

FIG. 2 is a scanning electron microscope morphology of the composite foaming agent particles of example 1.

FIG. 3 is a digital photograph of the front surface of the polypropylene foam pattern of example 1 (the foaming agent contains 100 parts of calcium carbonate).

FIG. 4 is a photograph showing a side view of the polypropylene foam pattern of example 1 (the foaming agent contains 100 parts of calcium carbonate).

FIG. 5 is a digital photograph of the front surface of the polypropylene foam pattern of example 1 (the foaming agent contains 70 parts of calcium carbonate).

FIG. 6 shows Raman spectra of polypropylene before (A) and after (B) laser-induced foaming in example 1.

FIG. 7 is a scanning electron micrograph of the surface topography of the foamed region of example 1.

Fig. 8 is a schematic view of the embodiment 1 in which the foamed region is visually represented in white.

Fig. 9 is a front digital photograph of the polyethylene foam pattern of example 2.

Fig. 10 is a front digital photograph of the polystyrene foam pattern of example 3.

Fig. 11 is a front digital photograph of the polypropylene foam pattern of comparative example 1.

Fig. 12 is a front digital photograph of the polyethylene foam pattern of comparative example 2.

Detailed Description

The invention is described in more detail below with reference to the following examples:

example 1

The working principle of foaming is generated by irradiating the high polymer material with laser as shown in fig. 1.

Mixing 2 parts of Carbon Nanotubes (CNTs) and 100 parts of calcium carbonate (CaCO)₃) The mixture was put in 2000 parts of ethanol and sonicated at 30 ℃ for 2 hours to prepare a foaming agent system solution. Completely evaporating ethanol in a vacuum oven at 50 ℃ to obtain CNTs/CaCO₃The scanning electron microscope morphology of the composite foaming agent particles is shown in figure 2.

The prepared composite foaming agent particles are added into a polypropylene (PP) substrate according to a proportion of five percent, a semiconductor laser marking machine is adopted, the laser power is 15W, the pulse laser wavelength is 1064nm, the foaming pattern is set to be a number of 2020, the front and side photos of the foaming pattern are respectively shown in figures 3 and 4, the polypropylene displays a white foaming pattern which can be identified by naked eyes, and the definition and the contrast are obvious.

If the amount of calcium carbonate added is reduced to 70 parts, the foaming pattern is unchanged for the rest of the steps, as shown in fig. 5, and the polypropylene still shows a white foaming pattern recognizable to the naked eye, but the contrast and the foaming height are reduced, because the amount of gas generated is reduced due to the reduction of the calcium carbonate content in the foaming agent, resulting in the reduction of the foaming degree. Therefore, it is possible to form a foaming structure to various degrees by adjusting the content of the foaming additive.

Analysis (five percent addition) was performed on the specified area before and after foaming by raman spectroscopy, and the raman spectra were plotted as shown in fig. 6, where fig. 6(a) is the raman spectrum before laser-induced foaming and fig. 6(B) is the raman spectrum after laser-induced foaming, and it can be seen that the foamed area was 1000cm^-1To 2000cm^-1The region produces a diffuse broad absorption peak, which is representative of the formation of an amorphous carbon structure. Indicating that the polypropylene surface forms a certain degree of carbon structure after foaming.

The surface topography of the foamed region was observed by scanning electron microscopy as shown in fig. 7. After laser-induced foaming of the polypropylene surface, arrayed "bulges" are formed, which are generated by gas generated by thermal decomposition of the foaming additive during laser irradiation, and the gas is wrapped by the polypropylene melt. Due to the gas wrapped inside the "bump", light is refracted and reflected on the surface of the "bump", so that the "bump" appears white under the observation of naked eyes, and the schematic diagram is shown in fig. 8.

Example 2

The working principle of foaming is generated by irradiating the high polymer material with laser as shown in fig. 1.

5 parts of Carbon Fiber (CF) and 200 parts of aluminum carbonate (AlCO)₃) The mixture was put in 1500 parts of ethyl acetate and sonicated at 40 ℃ for 3 hours to prepare a foaming agent system solution. Completely evaporating the ethyl acetate in a vacuum oven at 50 ℃ to obtain CF/AlCO₃A composite foaming agent.

The prepared composite foaming agent is added into a Polyethylene (PE) substrate according to a ten-percent ratio, a semiconductor laser marking machine is adopted, the laser power is 20W, the pulse laser wavelength is 1064nm, the pattern is set to be a cartoon pattern, the foaming pattern is shown in figure 9, the polyethylene shows a white foaming structure which can be identified by naked eyes, and the definition and the contrast are obvious.

Example 3

The working principle of foaming is generated by irradiating the high polymer material with laser as shown in fig. 1.

10 parts of Carbon Fiber (CF) and 150 parts of magnesium carbonate(MgCO₃) Placing the mixture in 1200 parts of petroleum ether, and carrying out ultrasonic treatment at the temperature of 30 ℃ for 2 hours to prepare foaming agent system solution. Completely evaporating petroleum ether in a vacuum oven at 40 ℃ to obtain CB/MgCO₃A composite foaming agent.

The prepared composite foaming agent is added into a Polystyrene (PS) substrate according to the proportion of eight percent, a semiconductor laser marking machine is adopted, the laser power is 10W, the pulse laser wavelength is 1064nm, the pattern is set as the number of 2020, the foaming pattern is shown in figure 10, the polystyrene displays a white foaming structure which can be identified by naked eyes, and the definition and the contrast are obvious.

Comparative example 1

2 parts of Graphene Oxide (GO) and 100 parts of calcium carbonate (CaCO)₃) The mixture was put in 2000 parts of ethanol and sonicated at 30 ℃ for 2 hours to prepare a foaming agent system solution. Completely evaporating ethanol in a vacuum oven at 50 ℃ to obtain GO/CaCO₃A composite foaming agent.

The prepared composite foaming agent particles are added into a polypropylene (PP) substrate according to a proportion of five percent, a semiconductor laser marking machine is adopted, the laser power is 15W, the pulse laser wavelength is 1064nm, a laser irradiation area is set to be a square pattern, a front photo of the pattern is shown in figure 11, the square pattern is rough and fuzzy, the definition and the contrast are low, the surface appearance is incomplete, and a regular foaming structure cannot be observed. This is because the graphene oxide with a two-dimensional structure cannot construct a three-dimensional cooperative network structure under a low addition amount condition, and the overall laser responsiveness is lower than that of a one-dimensional carbon nanotube, so that the overall effect of the foaming pattern is poor.

Comparative example 2

5 parts of Carbon Black (CB) and 200 parts of aluminum carbonate (AlCO)₃) The mixture was put in 1500 parts of ethyl acetate and sonicated at 40 ℃ for 3 hours to prepare a foaming agent system solution. Completely evaporating the ethyl acetate in a vacuum oven at 50 ℃ to obtain CB/AlCO₃A composite foaming agent.

The prepared composite foaming agent is added into a Polyethylene (PE) substrate according to a ten-percent ratio, a semiconductor laser marking machine is adopted, the laser power is 20W, the pulse laser wavelength is 1064nm, the pattern is set to be a square pattern, the foaming pattern is shown in figure 12, the foaming pattern can not be basically observed by naked eyes, the surface of the polyethylene substrate is only provided with black marks in the shape of the square, and the reason is that carbon black particles are difficult to construct a complete network system under the condition of low addition amount, so the photothermal conversion efficiency under the laser irradiation is low, and a foaming structure can not be formed.