CN113121866B - PCL/PLGA composite foaming oil absorption material and preparation method thereof - Google Patents

PCL/PLGA composite foaming oil absorption material and preparation method thereof Download PDF

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CN113121866B
CN113121866B CN202110435278.1A CN202110435278A CN113121866B CN 113121866 B CN113121866 B CN 113121866B CN 202110435278 A CN202110435278 A CN 202110435278A CN 113121866 B CN113121866 B CN 113121866B
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oil absorption
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CN113121866A (en
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蒋晶
蔡泊志
李倩
王小峰
金志伟
郭海洋
乔玉辉
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Zhengzhou University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
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    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/06—CO2, N2 or noble gases
    • C—CHEMISTRY; METALLURGY
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    • C08J2203/00—Foams characterized by the expanding agent
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    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
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    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2467/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2467/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones

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Abstract

The invention belongs to the field of environmental protection, and particularly discloses a PCL/PLGA composite foaming oil absorption material and a preparation method thereof, wherein the preparation method comprises the following steps: 1) carrying out melt blending on PCL, PLGA and an auxiliary agent, and pressing into a thin plate; (2) placing the thin plate in a reaction kettle, heating to 42-55 ℃, introducing supercritical gas after the temperature is constant, controlling the pressure range to be 1800-2500 psi, then heating to 80-90 ℃, and preserving heat for 3-5 min; (3) after heat preservation, reducing the temperature to 40-45 ℃, and saturating at the temperature for 1-3 h; (4) after saturation, carrying out ultrasonic treatment on the thin plate; (5) after ultrasonic treatment, releasing supercritical fluid in the reaction kettle until the reaction kettle is in a normal pressure state, and then reducing the temperature to 0-10 ℃; (6) and (4) after cooling, taking out the thin plate, and drying to obtain the PCL/PLGA composite foaming oil absorption material. The PCL/PLGA composite foaming oil absorption material prepared by the invention has small cell size, large cell density, biodegradability, strong oil absorption performance and reusability.

Description

PCL/PLGA composite foaming oil absorption material and preparation method thereof
Technical Field
The invention belongs to the field of environmental protection, particularly belongs to the field of processing of polymer materials for oil stain treatment, and more particularly relates to a PCL/PLGA composite foaming oil absorption material and a preparation method thereof.
Background
The rapid development of modern industry, petroleum and products thereof are widely applied, oil spillage accidents of different scales frequently occur, marine organism survival is affected, and the natural ecological environment is destroyed. Meanwhile, the discharge amount of industrial organic wastewater and urban oily wastewater is greatly increased, and a large amount of oil pollutants enter water environments such as rivers, oceans and the like and enter human bodies in a food chain form, so that the health of human beings is seriously threatened. At present, the main methods for treating oil pollution include in-situ combustion, use of oil dispersants or adsorbents, biodegradation and decontamination and the like, wherein the most economical and effective method is to use an oil stain adsorption material.
There are three main types of oil absorbing materials currently commercialized: inorganic minerals, natural organic crops and artificial synthesis. The inorganic mineral material is mostly in powder form, the oil absorption capacity of the inorganic mineral material is limited, the oil absorption capacity needs to be increased through a complicated modification treatment process, the cost is high, and the inorganic mineral material cannot be combusted after oil absorption and is difficult to treat; natural organic materials (such as cotton, fibers and the like) have wide sources and strong lipophilicity, but have the problems of absorbing oil and absorbing water, so that the use efficiency is influenced; the common characteristics of the artificially synthesized high polymer oil absorption materials are that the cost and the density are low, the oil absorption multiplying power is high, but the oil-water selectivity is poor, and the most important problems are that the materials are difficult to degrade under natural conditions, secondary pollution can be caused to the environment after the materials are used, and the materials are not favorable for repeated use and environmental protection requirements.
The ideal oil absorption material has good oleophylic property and hydrophobicity, the inside of the material has larger porosity and cell connectivity so as to ensure higher oil absorption efficiency, and meanwhile, the material has certain elasticity and mechanical strength so as to realize repeated circulation oil absorption. A large number of ester lipophilic groups exist in a molecular chain of a biodegradable polymer represented by Polycaprolactone (PCL) and polylactic-co-glycolic acid (PLGA), and oil molecules can diffuse into the molecular chain of the PCL or PLGA based on the principle of similar intermiscibility, but the oil absorption of the effect is limited. Supercritical carbon dioxide (S)CCO2) Foaming is a green pollution-free porous material processing technology, is not limited by chemical foaming decomposition temperature, and does not pollute the environment in the whole process. The good thermoplastic processability of the PCL and PLGA materials enables the material to pass SCCO2The foaming technology can prepare porous materials by changing different material components and SCCO2The process parameters can realize the regulation and control of the size, the density and the foaming multiplying power of the foam holes; in addition, the second biodegradable material with large difference of viscoelasticity can be melt blended in the foaming processThe soft and hard phases interact with each other to realize the cell connection and regulate the internal opening rate.
But the pure PCL material has too high crystallization rate and low melt strength, the nucleation of foam cells in the foaming process is difficult, and the foam cells are easy to collapse in the growing process; the PLGA material has high melt viscosity, poor crystallinity, large steric hindrance required by bubble nucleation and growth, and is not easy to foam. In addition, no matter PCL or PLGA, in the process of singly carrying out the traditional micropore foaming, as the nucleation mode is mainly homogeneous nucleation, the cells are difficult to be mutually communicated, and the preparation of the porous material and the application in the fields of tissue engineering, oil-water separation and the like are seriously restricted. Therefore, a series of biodegradable material systems are urgently needed to be developed based on PCL or PLGA, the traditional micropore foaming process is improved, a micro-nano porous structure with adjustable cell size and density, uniform cell distribution, high foaming multiplying power and highly communicated cell interior is constructed through regulation and control of process parameters and a microstructure, the lightening, hydrophobic and oleophylic properties of the material can be ensured, the porous material can have certain elastic recovery through regulation and control of material components and the cell structure, and the application purpose of multiple and efficient oil-water separation can be met.
In addition, in the prior art, the publication number is CN104987523A, the patent name is a preparation method of a polymer micro-foaming film, ultrasonic treatment is performed in the whole process from saturation to release of a supercritical fluid to normal pressure, and cavitation effect is generated due to overlong ultrasonic time, so that cells collapse in the cell growth process, and the prepared film material has low mechanical strength and cannot be recycled for multiple times; in addition, the method disclosed in the patent is only used for foaming the interior of the polymer film, and cannot enable the surface of the polymer film to generate cells, and the cells in the interior are relatively independent and have poor connectivity, so that quick and efficient oil absorption cannot be realized.
Disclosure of Invention
The invention aims to provide a PCL/PLGA composite foaming oil absorption material and a preparation method thereof.
Based on the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a preparation method of a PCL/PLGA composite foaming oil absorption material, which comprises the following steps:
(1) melting and blending 78-93 wt% of PCL, 5-20 wt% of PLGA and 0-2.5 wt% of an auxiliary agent, and pressing into a thin plate with the thickness of 1 +/-0.2 mm at the temperature of 80-90 ℃;
(2) placing the sheet prepared in the step (1) in a supercritical fluid reaction kettle, heating to 42-55 ℃, introducing supercritical gas after the temperature is constant, controlling the pressure range to be 1800-2500 psi, then heating to 80-90 ℃, and preserving heat for 3-5 min;
(3) after heat preservation, reducing the temperature in the reaction kettle to 40-45 ℃ at a speed of more than 5 ℃/min, and saturating at the temperature for 1-3 h;
(4) after saturation, carrying out ultrasonic treatment on the thin plate in the reaction kettle, so that heterogeneous gas nuclei formed by PCL and PLGA in the thin plate are uniformly distributed in the thin plate; wherein the ultrasonic frequency is 10-30 MHz, and the ultrasonic time is 30-180 s;
(5) releasing supercritical fluid in the reaction kettle to enable the reaction kettle to be in a normal pressure state after ultrasonic treatment, enabling heterogeneous gas nuclei in the sheet to grow to form foam holes in the process, reducing the temperature in the reaction kettle to 0-10 ℃, and shaping the foam holes in the sheet;
(6) and (4) after cooling, taking out the thin plate, and drying to obtain the PCL/PLGA composite foaming oil absorption material.
Furthermore, the foaming ratio of the prepared PCL/PLGA composite foaming oil absorption material is 10-20 times, and the internal aperture ratio is more than 70%.
Furthermore, the diameter of the inner cells of the prepared PCL/PLGA composite foaming oil absorption material is 23.5-50.6 microns; cell density of 2X 108～6×108cells/cm3。
Further, the auxiliary agents in the step (1) comprise an antioxidant, a lubricant and an anti-hydrolysis agent; wherein the addition amount of the antioxidant is 0 to 0.5 weight percent; the addition amount of the lubricant is 0-1 wt%; the addition amount of the hydrolysis resistant agent is 0 to 1 weight percent.
Further, the supercritical fluid is supercritical CO2A fluid.
Further, the specific process of drying the thin plate in the step (6) is as follows: and (3) drying the thin plate at 40 ℃ for 4h in vacuum to obtain the PCL/PLGA composite foaming oil absorption material.
In a second aspect, the invention provides a PCL/PLGA composite foaming oil absorption material, which is prepared by the method.
Furthermore, the foaming ratio of the prepared PCL/PLGA composite foaming oil absorption material is 10-20 times, and the internal aperture ratio is more than 70%.
Furthermore, the diameter of the inner cells of the prepared PCL/PLGA composite foaming oil absorption material is 23.5-50.6 microns; cell density of 2X 108～6×108cells/cm3。
In a third aspect, the invention provides an application of a PCL/PLGA composite foaming oil absorption material in oil stain treatment, wherein the PCL/PLGA composite foaming material is the PCL/PLGA composite foaming material or the PCL/PLGA composite foaming material prepared by the method.
Further, the PCL/PLGA composite foaming material applied to oil stain treatment has a single oil absorption multiplying power of 10-18 g/g; the oil absorption multiplying power is reduced by no more than 10 percent after 10 times of compression.
Compared with the prior art, the invention has the following beneficial effects:
(1) compared with the prior art that the sheet material to be foamed is placed in a supercritical fluid reaction kettle and is directly heated to the saturation temperature of the supercritical fluid, the sheet material to be foamed is firstly kept at the constant temperature for a certain time at the temperature higher than the melting point of the sheet material, and then is cooled to the temperature higher than the crystallization temperature of the sheet material to be foamed, and the temperature is used as the saturation temperature of the supercritical fluid; the invention adopts the high-temperature constant-temperature treatment in advance to the thin plate material to be foamed, aims to eliminate the influence of the self thermal history of the thin plate material on the subsequent cell nucleation, and then reduces the temperature to be higher than the crystallization temperature of the thin plate material for saturation, so that the influence of the material crystallization on the cell nucleation and the growth process can be effectively reduced, and the foamed material prepared by the method has higher cell nucleation density.
(2) Compared with the prior art that the supercritical fluid reaches permeation swelling saturation in the sheet material, and the ultrasonic treatment is continuously carried out in the processes of recovering the normal pressure of the reaction kettle and cooling the reaction kettle until the supercritical fluid is released to the reaction kettle, the ultrasonic treatment is started after the supercritical fluid is saturated, and the ultrasonic treatment is stopped before pressure release and cooling, so that the ultrasonic vibration only acts on the cell nucleation stage, the cavitation effect caused by long-time ultrasonic vibration is avoided, and the cells collapse in the cell growth process, thereby improving the overall mechanical strength of the sheet material, remarkably improving the nucleation rate and nucleation point uniformity, reducing the cell size, and increasing the cell density by 1 order of magnitude.
(3) The PCL/PLGA composite foaming material prepared by the method has the internal aperture ratio of not less than 70 percent and the foaming ratio of 10-20 times; the diameter of the inner foam hole of the material is 23.5-50.6 μm; cell density of 2X 108～6×108cells/cm3。
(4) The PCL/PLGA composite foaming material for oil stain treatment provided by the invention has a single oil absorption multiplying power of 10-18 g/g; after multiple times of compression, the oil absorption multiplying power is reduced by no more than 10%, and the effects of high efficiency and multiple times of circulating oil absorption can be achieved.
(5) PCL and PLGA are biodegradable materials, and the PCL/PLGA composite foaming material prepared from PCL and PLGA also has biodegradability, and can avoid causing secondary pollution to the environment when adsorbing oil stains.
(7) According to the invention, two biodegradable materials of PCL and PLGA with large viscoelasticity difference are selected, and in the foaming process, the cell communication is realized through the interaction of soft and hard phases, the internal opening rate is regulated and controlled, and the oil absorption effect is improved.
In conclusion, the PCL/PLGA composite foaming material which has stronger oil absorption performance and can be repeatedly used is prepared by taking two biodegradable materials with larger difference in viscoelasticity as main raw materials and improving the supercritical fluid foaming technology, and the secondary pollution to the environment is effectively avoided while the oil stain treatment effect is improved.
Drawings
FIG. 1 is a scanning electron micrograph of sample 1 and control 1 in example 2; wherein, (a) is a scanning electron micrograph of the sample 1, and (b) is a scanning electron micrograph of the control 1;
FIG. 2 is a scanning electron micrograph of sample 2 and control 2 in example 3; wherein, (a) is a scanning electron micrograph of the sample 2, and (b) is a scanning electron micrograph of the control 2;
FIG. 3 is a scanning electron microscope image of samples 3-1 to 3-5 with different component ratios in example 4; wherein, (a) is a scanning electron micrograph of the sample 3-1, and (b) is a scanning electron micrograph of the sample 3-2; (c) is an SEM image of sample 3-3, (d) is an SEM image of sample 3-4, and (e) is an SEM image of sample 3-5.
Detailed Description
Example 1: preparation method of PCL/PLGA composite foaming oil absorption material
The preparation method of the PCL/PLGA composite foaming oil absorption material comprises the following steps:
(1) the PCL and the PLGA are melted and blended to be made into a thin plate
Melting and blending 78wt% of PCL (number average molecular weight 50000), 20wt% of PLGA (weight average molecular weight 100000, the ratio of lactic acid LA to glycolic acid GA is 50: 50), 0.5wt% of antioxidant 1010, 1.0 wt% of lubricant polytetrafluoroethylene and 0.5wt% of hydrolysis-resistant agent Bio additive 100 on a double-screw extruder, and granulating to prepare PCL/PLGA blended particles; placing the PCL/PLGA blended particles on a vacuum hot press, hot-pressing for 5min under the conditions that the temperature and the pressure are respectively 100 ℃ and 1200psi, and supporting the PCL/PLGA blended particles on thin plates with the length, the width and the height of 300mm, 200mm and 1mm respectively.
(2) High temperature heat treatment before saturation treatment
Placing the thin plate in a supercritical fluid reaction kettle mold cavity, heating the reaction kettle mold to 50 ℃, introducing 2000psi of supercritical CO after the temperature is constant2And continuously heating to 85 ℃, keeping the temperature constant for 5min at the temperature, and eliminating the thermal history of the sheet so that the temperature at each part inside the sheet is uniform and constant.
(3) Saturation treatment
Introducing cooling water into the reaction kettle, reducing the temperature in the mold cavity to 40 ℃ within 30s, and after the temperature is saturated for 2.0h, thinning the mold cavityPlate pair supercritical CO2The gas reaches saturation adsorption, and PCL/PLGA polymer and CO2A homogeneous system is formed.
(4) Ultrasonic treatment to form heterogeneous gas nuclei
And after saturation is reached, two ultrasonic probes arranged on the surface of the die are started, the frequency of ultrasonic waves is controlled to be 20MHz, and the ultrasonic probes are closed after ultrasonic waves are performed for 60 s.
(5) Pressure relief foaming and cell stabilization
Opening the pressure release valve of the mold to ensure that the gas in the mold cavity is reduced to the atmospheric pressure at the pressure release rate of 5MPa/s, and during the pressure release process, the heterogeneous gas core formed in the thin plate is grown to form a bubble hole; and opening cooling water, reducing the temperature in the die cavity to 5 ℃, then closing the cooling water, and shaping the foam holes formed in the sheet in the cooling process.
(6) Drying to obtain the final product
And taking the thin plate out of the reaction kettle mold, placing the thin plate in a vacuum drying oven, and drying for 4 hours at 40 ℃ to obtain the PCL/PLGA composite foaming oil absorption material.
Example 2: influence of high-temperature thermal pretreatment before saturation on performance of PCL/PLGA composite foaming oil absorption material
1. Sample preparation
Sample 1: the PCL/PLGA composite foaming oil absorption material prepared by referring to the method steps (1) to (6) in the example 1, wherein the temperature of the high-temperature heat treatment in the step (2) is 85 ℃, and is marked as a sample 1.
Control 1: referring to step (1) of example 1, the sheet was prepared by heating the mold to 40 ℃ in step (3) and introducing 2000psi of supercritical CO2Saturation for 2.0h to form PCL/PLGA polymer and CO2The PCL/PLA composite foaming oil absorption material prepared by the steps (4) to (6) is recorded as a reference 1.
Control 1 differs from sample 1 in the preparation process only in that control 1 has not undergone the high-temperature thermal pretreatment process before saturation in step (2) of example 1.
2. Performance testing
The performance test indexes of the PCL/PLGA composite foaming oil absorption material comprise foaming multiplying power, opening rate, cell diameter, cell density and oil absorption multiplying power, and the specific test methods are respectively as follows:
(1) expansion ratio
Foaming ratio R of samplevThe volume change of the sample before and after foaming is calculated, and the calculation formula is as follows: rv＝ρp/ρf(ii) a Where ρ ispThe density of the sample before foaming is the density of a thin plate prepared by melting and blending PCL and PLGA; rhofThe density of the PCL/PLGA composite foaming oil absorption material thin plate is finally prepared by foaming the thin plate.
Density p before and after foaming of the samplep、ρfAll measured according to the water displacement method described in ASTM D792.
(2) Open porosity of sample
The open cell content of the sample was measured directly by a fully automatic vacuum densitometer, Quantachrome, model ULTRAPYC 1200 e.
(3) Cell diameter and cell density
The diameter and the density of the cells are calculated according to a scanning electron microscope Image of the cell structure and Image J software, and the formulas are respectively as follows:
Figure BDA0003032719930000061
Figure BDA0003032719930000062
wherein D is the average cell diameter, n is the number of cells in the SEM picture, DiFor the diameter of each cell, NfTo average cell density, A is the area occupied by all cells in the picture.
(4) Oil absorption multiplying power
The test process of the oil absorption multiplying power is as follows: cutting the PCL/PLGA composite foaming oil absorption material thin plate into a cube sample with the side length of 10mm, placing the cube sample in a beaker filled with sufficient silicone oil, taking out the sample every 30s, removing oil stains on the surface, and weighing until the weight is unchanged.
Oil absorption multiplying power
Figure BDA0003032719930000063
The calculation formula of (2) is as follows: expansion ratio
Figure BDA0003032719930000064
Wherein m is1For the cube sample, stable and constant weight after oil absorption, m0The weight of the cube sample before oil absorption.
The method for testing the cyclic compression oil absorption multiplying power comprises the following steps: taking a cube sample with the side length of 3mm to measure the mass and recording the mass as m0After immersed in oil for a period of time, taken out and weighed as m1The weight m is measured after squeezing the oil out of the sample with tweezers1', this process is described as 1 cycle, and the oil absorption rate after 10 cycles is tested according to the above formula.
3. Analysis and discussion of results
The scanning electron micrographs of the sample 1 and the control 1 are shown in FIG. 1, in which (a) is the scanning electron micrograph of the sample 1 and (b) is the scanning electron micrograph of the control 1.
As can be seen from fig. 1, the cell size in sample 1 is small and the cell density is higher by 1 order of magnitude than that in control 1. The reason is that the comparative sample 1 is not subjected to high-temperature pretreatment, the PCL material has strong crystallization performance, and partial PCL molecular chains are crystallized in the saturation process, so that the nucleation of foam cells is inhibited to a certain extent, and the final foaming nucleation density is reduced and the size of the foam cells is increased. The thermal history of the PCL is eliminated after the sample 1 is pretreated at high temperature, when the temperature is reduced to be higher than the PCL crystallization temperature (40 ℃), the PCL material starts homogeneous and heterogeneous nucleation process without starting crystallization, the generation of a large number of nucleation points is ensured, more nucleation points are generated by means of the cavitation effect generated by ultrasonic waves, and the distribution is more uniform, so that the material generates a large number of small and dense nucleation points which are uniformly distributed in the nucleation stage. The results of the tests of the sample 1 and the control 1 by the methods of the above-mentioned foaming ratio, opening ratio, cell diameter, cell density, oil absorption ratio, etc. are shown in Table 1.
TABLE 1 results of Performance test of sample 1 and control 1
Figure BDA0003032719930000071
As can be seen from the results in table 1, compared with the control sample 1, the foaming ratio, the internal opening ratio, the cell density, the cell size and the oil absorption ratio of the sample 1 are all superior to those of the control sample 1, and the oil absorption ratio of the sample 1 after 10 times of cyclic compression can still reach 16.1g/g, which is only reduced by 8.5% relative to the initial oil absorption ratio, while the oil absorption ratio of the control sample 1 after 10 times of cyclic compression is reduced by 37.5% because the high cell density and the high foaming ratio have stronger capillary acting force, which is more beneficial for oil drops to be absorbed into the cell structure and remain in the cell structure under the action of the surface tension and the capillary force; and the sample with high aperture ratio can provide a smoother internal channel for oil drops, and the oil absorption rate is improved. The result shows that the sample 1 prepared by the invention not only has good oil absorption performance, but also can be recycled.
Example 3: influence of ultrasonic treatment at different stages on performance of PCL/PLGA composite foaming material
1. Sample preparation
1) Sample No. 2
The PCL/PLGA composite foaming oil absorption material sample prepared by the preparation method in example 1 is referred to as sample 2, wherein the sample is prepared by using 88 wt% of PCL (number average molecular weight 50000), 10 wt% of PLGA (weight average molecular weight 100000, the ratio of lactic acid LA to glycolic acid GA is 50: 50), 0.5wt% of antioxidant 1010, 1.0 wt% of lubricant polytetrafluoroethylene and 0.5wt% of hydrolysis-resistant agent Bio additive 100 as raw materials. In the process, the ultrasound only acts in the stage after saturation and before decompression.
2) Control 2
The starting material for preparation of control 2 was the same as that of sample 2, and the same was applied to the preparation method given in example 1, except that the ultrasonication was applied to step (4) and step (5) in the preparation of control 2, that is, the ultrasonication was applied to the whole period after the supercritical fluid was saturated until the end of the depressurization.
The specific procedures of step (4) and step (5) in the preparation of control 2 are as follows:
(4) ultrasonic treatment to form heterogeneous gas nuclei: after saturation is reached, two ultrasonic probes arranged on the surface of the die are started, the ultrasonic frequency is controlled to be 20MHz, and ultrasonic treatment is carried out.
(5) Pressure relief foaming and cell stabilization: meanwhile, opening a pressure release valve of the mold to ensure that the gas in the mold cavity of the mold is released at a pressure release rate of 5MPa/s, so that the pressure in the mold cavity of the mold is reduced to the atmospheric pressure; and opening cooling water, reducing the temperature in the mold cavity to 5 ℃, closing the cooling water, and stopping ultrasound.
2. Analysis and discussion of results
The electron microscope scans sample 2 and control sample 2, respectively, and their scanning electron micrographs are shown in fig. 2, in which (a) is the scanning electron micrograph of sample 2, and (b) is the scanning electron micrograph of control sample 2.
As can be seen from fig. 2, the sample 2 is subjected to ultrasonic oscillation only in the cell nucleation stage, and the cavitation effect generated by the ultrasonic oscillation can assist in generating more nucleation points, and the distribution is more uniform, so that a large number of uniformly distributed, small and dense nucleation points are generated in the material in the nucleation stage. In the subsequent cell growth and shaping stages of the comparison sample 2, the ultrasonic action exists all the time, and the strong cavitation effect brought by the long-time ultrasonic oscillation causes overlarge local energy in the cell growth process and partial cell walls collapse.
The results of the performance test of sample 2 and control 2 with reference to the performance test method in example 2 are shown in Table 2.
TABLE 2 results of Performance test of sample 2 and control 2
Figure BDA0003032719930000081
As can be seen from Table 2, the cell size, cell density, foaming ratio and oil absorption ratio of the sample 2 are all superior to those of the comparative sample 2, because the cavitation effect of ultrasonic oscillation is acted on the comparative sample 2 for too long time, the cell wall is obviously collapsed due to the action of local high temperature, and the foaming ratio of the sample is lower. In addition, the difference in the opening ratio between the sample 2 and the control 2 was not so large, because the cavitation effect had a large influence on the degree of opening of both. The PLGA content in the sample 2 is 10%, the overall elasticity of the sample is reduced less than that of a pure PCL material, and the oil absorption multiplying power of the sample is reduced by only 10% after 10 times of cyclic compression; and part of the cells in the reference sample 2 collapse under the action of strong cavitation effect, so that the overall strength of the sample is reduced, and the oil absorption rate is greatly reduced by about 27 percent after 10 times of cyclic compression.
Example 4: influence of weight ratio of different PCL and PLGA on PCL/PLGA composite foaming material performance
1. Sample preparation
The preparation method of the PCL/PLGA composite foaming oil absorption material sample comprises the following steps:
(1) the PCL and the PLGA are melted and blended to be made into a thin plate
Melting and blending 68-98 wt% of PCL and PLGA in different proportions, 0.5wt% of antioxidant 1010, 1.0 wt% of lubricant polytetrafluoroethylene and 0.5wt% of hydrolysis-resistant agent Bio additive 100 on a double-screw extruder, and granulating to obtain PCL/PLGA blended particles; then the blended particles are placed on a vacuum hot press and hot-pressed for 5min under the conditions that the temperature and the pressure are respectively 100 ℃ and 1200psi, and sheets with the length, the width and the height of 300mm, 200mm and 1mm are prepared. The component ratios between PCL and PLGA are shown in table 3.
(2) High temperature heat treatment before saturation treatment
Placing the thin plate in a supercritical fluid reaction kettle mold cavity, heating the reaction kettle mold to 45 ℃, introducing 2200psi of supercritical CO after the temperature is constant2And continuously raising the temperature to 80 ℃, and keeping the temperature constant at the temperature for 5min to eliminate the thermal history of the sheet so that the temperature is uniform and constant at all positions inside the sheet.
(3) Saturation treatment
Introducing cooling water into the reaction kettle, reducing the temperature in the die cavity to 42 ℃ within 30s, and saturating the reaction kettle for 3.0h at the temperature to obtain a sheet pair supercritical CO2The adsorption of gas is saturated, so that the PCL/PLGA polymer and CO are obtained2A homogeneous system is formed.
(4) Ultrasonic treatment to form heterogeneous gas nuclei
And after saturation is reached, two ultrasonic probes arranged on the surface of the die are started, the frequency of ultrasonic waves is controlled to be 20MHz, and the ultrasonic probes are closed after ultrasonic waves are performed for 100 s. The purpose of the ultrasonic treatment is to promote the formation of heterogeneous gas nuclei by the PCL and the PLGA in the thin plate and to ensure that the formation points of the heterogeneous gas nuclei are uniformly distributed in the thin plate.
(5) Pressure relief foaming and cell stabilization
Opening the pressure release valve of the mold to ensure that the gas in the mold cavity is reduced to the atmospheric pressure at the pressure release rate of 5MPa/s, and during the pressure release process, the heterogeneous gas core formed in the thin plate is grown to form a bubble hole; and opening cooling water, reducing the temperature in the die cavity to 5 ℃, then closing the cooling water, and shaping the foam holes formed in the sheet in the cooling process.
(6) Drying to obtain the final product
And taking the thin plate out of the reaction kettle mold, placing the thin plate in a vacuum drying oven, and drying for 4 hours at 40 ℃ to obtain the PCL/PLGA composite foaming oil absorption material.
The PCL/PLGA composite foaming oil absorption materials prepared by different PCL and PLGA ratios are respectively marked as samples 3-1 to 3-5, as shown in Table 3.
2. Analysis and discussion of results
The scanning electron micrographs of the samples 3-1 to 3-5 are shown in FIG. 3, in which (a) is the scanning electron micrograph of the sample 3-1, (b) is the scanning electron micrograph of the sample 3-2, (c) is the scanning electron micrograph of the sample 3-3, (d) is the scanning electron micrograph of the sample 3-4, and (e) is the scanning electron micrograph of the sample 3-5.
As can be seen from fig. 3, the pure PCL cell size is largest and large area collapse of the cells occurs due to the weak melt strength of the pure PCL. Increasing the PLGA content gradually results in a significant increase in cell density and a decrease in cell size due to heterogeneous nucleation of the PLGA dispersed phase. However, when the content of PLGA is 30%, the PLGA in the PCL/PLGA blend exists in the form of a partially co-continuous phase, so that heterogeneous nucleation points at the interface of PCL and PLGA are reduced, the cell density is reduced, and the cell size is increased.
Referring to the performance test method in example 2, the performance tests were performed on samples 3-1 to 3-5, and the results are shown in Table 3:
TABLE 3 test results of sample structure and performance test of different PCL and PLGA mass ratios
Figure BDA0003032719930000091
As can be seen from Table 3, compared with the pure PCL material, the PCL/PLGA blend foaming material prepared by adding PLGA with different contents has better performance indexes. Along with the increase of the PLGA content, the melt strength of the blend is increased, which is more beneficial to the nucleation and growth of foam cells and the expansion ratio is increased. However, when PLGA is increased to 30%, PCL content available for foaming decreases due to excessive melt strength, and foaming ratio decreases. In addition, although the pure PCL foaming material has high aperture ratio, the oil absorption ratio is not high and the oil absorption of multiple cycles cannot be realized due to the low foaming ratio and serious collapse of cells. After 10-20% of PLGA material is added, according to the process of the invention, the once foaming multiplying power of the foaming samples with different component ratios is above 10g/g, the reduction rate of the oil absorption multiplying power after 10 times of cyclic compression is not more than 10%, and the effect of high efficiency and multiple oil absorption can be realized. However, when the PLGA content was further increased to 30%, the indexes such as the open cell content and the oil absorption were all decreased.

Claims (8)

1. A preparation method of a PCL/PLGA composite foaming oil absorption material is characterized by comprising the following steps:
(1) melting and blending 78-93 wt% of PCL, 5-20 wt% of PLGA and 0-2.5 wt% of an auxiliary agent, and pressing into a thin plate with the thickness of 1 +/-0.2 mm at the temperature of 80-90 ℃; the auxiliary agent comprises an antioxidant, a lubricant and an anti-hydrolysis agent; the addition amount of the antioxidant is 0 to 0.5 weight percent; the addition amount of the lubricant is 0-1 wt%; the addition amount of the hydrolysis resistant agent is 0-1 wt%;
(2) placing the sheet prepared in the step (1) in a supercritical fluid reaction kettle, heating to 42-55 ℃, introducing supercritical gas after the temperature is constant, controlling the pressure range to be 1800-2500 psi, then heating to 80-90 ℃, and preserving heat for 3-5 min;
(3) after heat preservation, reducing the temperature in the reaction kettle to 40-45 ℃ at a speed of more than 5 ℃/min, and saturating at the temperature for 1-3 h;
(4) after saturation, carrying out ultrasonic treatment on the thin plate in the reaction kettle; wherein the ultrasonic frequency is 10-30 MHz, and the ultrasonic time is 30-180 s;
(5) after ultrasonic treatment, releasing supercritical fluid in the reaction kettle until the reaction kettle is in a normal pressure state, and then reducing the temperature in the reaction kettle to 0-10 ℃;
(6) and (4) after cooling, taking out the thin plate, and drying to obtain the PCL/PLGA composite foaming oil absorption material.
2. The method of claim 1, wherein the supercritical fluid is supercritical CO2A fluid.
3. The method according to claim 2, wherein the step (6) of drying the sheet comprises the following steps: and (3) drying the thin plate at 40 ℃ for 4h in vacuum to obtain the PCL/PLGA composite foaming oil absorption material.
4. The PCL/PLGA composite foaming oil absorption material prepared by the preparation method of any one of claims 1 to 3.
5. The PCL/PLGA composite foaming oil absorption material as claimed in claim 4, wherein the foaming ratio of the PCL/PLGA composite foaming oil absorption material is 10-20 times, and the internal aperture ratio is more than 70%.
6. The PCL/PLGA composite foaming oil absorption material of claim 5, wherein the diameter of the cells inside the PCL/PLGA composite foaming oil absorption material is 23.5-50.6 μm; cell density of 2X 108～6×108 cells/cm3。
7. The use of the PCL/PLGA composite foamed oil absorbent material of claim 5 or 6 in oil stain treatment.
8. The use according to claim 7, wherein the PCL/PLGA composite foaming material has a single oil absorption rate of 10 to 18 g/g; the reduction rate of oil absorption multiplying power after 10 times of cyclic compression is within 10 percent.
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