Surface modification treating agent, modified calcium hydroxide and microporous polyurethane elastic material
阅读说明：本技术 一种表面改性处理剂、改性氢氧化钙及一种微孔聚氨酯弹性材料 (Surface modification treating agent, modified calcium hydroxide and microporous polyurethane elastic material ) 是由 滕向 李鑫 刘赵兴 赵国平 杨洗 张聪颖 俞涛 于 2020-12-14 设计创作，主要内容包括：本发明提供一种氢氧化钙表面改性处理剂、一种改性氢氧化钙及一种微孔聚氨酯弹性材料。所述氢氧化钙表面处理剂,能使氢氧化钙粒子表面锚定多胺类扩链剂与反应型叔胺催化剂,使该粒子区域内异氰酸酯基团的凝胶与发泡反应得以高效进行。所述表面锚定多胺类扩链剂与反应型叔胺催化剂改性氢氧化钙粒子可在聚醚多元醇中均匀分散,并可吸收二氧化碳生成化学发泡剂水,充当发泡核心,使发泡反应高效、均匀地进行。所述微孔聚氨酯弹性材料施工稳定性高,制品泡孔均匀,冲击吸收性能性能良好。(The invention provides a calcium hydroxide surface modification treatment agent, modified calcium hydroxide and a microporous polyurethane elastic material. The calcium hydroxide surface treating agent can anchor polyamine chain extender and reactive tertiary amine catalyst on the surface of calcium hydroxide particles, so that the gel and foaming reaction of isocyanate groups in the particle region can be efficiently carried out. The surface anchoring polyamine chain extender and the reactive tertiary amine catalyst modified calcium hydroxide particles can be uniformly dispersed in polyether polyol, and can absorb carbon dioxide to generate chemical foaming agent water serving as a foaming core, so that the foaming reaction is efficiently and uniformly carried out. The microporous polyurethane elastic material has high construction stability, uniform product pores and good impact absorption performance.)
1. A polyamine chain extender has a structural formula as follows:
2. the polyamine-based chain extender according to claim 1, which is prepared by the following steps:
reacting 4, 4' -bis (aminomethyl) diphenylmethane with acetone in the presence of hydrogen and a catalyst to obtain the product;
preferably: the molar ratio of 4, 4' -bis (aminomethyl) diphenylmethane to acetone is 1: 3.0-5.0;
the catalyst is a palladium/hydrogen type zeolite catalyst, and the using amount of the catalyst is 1-4% of the mass of the 4, 4' -bis (aminomethyl) diphenylmethane;
the hydrogen pressure is 2-5 MPa;
the reaction temperature is 100-150 ℃.
3. A surface modification treating agent comprises a polyamine chain extender and a reactive tertiary amine catalyst, wherein the mass ratio of the polyamine chain extender to the reactive tertiary amine catalyst is (2-9): 1, the polyamine-based chain extender being the polyamine-based chain extender described in claim 1 or 2,
preferably, the reactive tertiary amine catalyst is selected from one or more of N, N ', N "-tetramethyl-N" -3-aminopropyldiethylenetriamine, bis (tetramethyldiethylenetriaminopropyl) amine, N ' -trimethyl-N ' -hydroxyethylbisaminoethyl ether, N ' -trimethyl-N ' -aminopropylbisaminoethyl ether, N ' -trimethyl-N ' -hydroxyethylethylenediamine.
4. A modified calcium hydroxide, which is obtained by the reaction of calcium oxide under the action of the surface modification treatment agent and deionized water as described in claim 3,
preferably, the mass ratio of calcium oxide to surface modifying treatment agent is 10: 0.5-3, wherein the mass ratio of calcium oxide to deionized water is 1: 10-30 ℃, the reaction temperature is 50-95 ℃, and the reaction time is 1-4 h.
5. A microporous polyurethane elastic material comprises an isocyanate prepolymer component, a combined material component and a catalyst component;
the isocyanate prepolymer component comprises the following components in parts by weight:
polyether polyols 30 to 70, preferably 40 to 60;
plasticizers 1 to 30, preferably 5 to 15;
10-40, preferably 15-35, of polyisocyanate;
the composite material comprises the following components in parts by weight:
wherein the modified calcium hydroxide is the modified calcium hydroxide according to claim 4.
6. The microcellular polyurethane elastomer material according to claim 5, wherein the catalyst component is an organic metal catalyst, preferably one or more of zinc neodecanoate, bismuth neodecanoate and dibutyltin didodecylthio, and the amount of the catalyst component is 0.1 to 0.6 percent of the mass of the composition component.
7. A microcellular polyurethane elastomeric material according to claim 5 or 6, said polyether polyol having a functionality of from 2 to 3 and a molecular weight of from 1000 to 6500; and/or
The plasticizer is selected from one or more of long-chain chlorinated paraffin, tributyl citrate, acetyl tributyl citrate, dioctyl terephthalate, chlorinated palm oil methyl ester and epoxy soybean oil methyl ester.
8. The microcellular polyurethane elastomeric material according to any one of claims 5 to 7, the polyisocyanate is diisocyanate diphenylmethane and a derivative thereof; and/or
The chain extender is selected from dimethylthiodiaminotoluene, 3, 5-diethyltoluenediamine, 4' -bis-sec-butylaminodiphenylmethane and 1, 4-bis-sec-butylaminobenzene.
9. The microcellular polyurethane elastomeric material according to any one of claims 5 to 8, wherein the conventional solid filler is selected from one or more of calcium carbonate, talc, kaolin, white carbon black and magnesium oxide; and/or
The carbon dioxide trapping agent is one or more of monoethanolamine, diethanolamine, triethanolamine, diisopropanolamine and methyldiethanolamine.
10. A microcellular polyurethane elastomeric material according to any one of claims 5 to 9 having an isocyanate index of from 1 to 1.5.
Technical Field
The invention relates to the field of modified fillers and polyurethane, in particular to a calcium hydroxide surface modification treating agent, modified calcium hydroxide and a microporous polyurethane elastic material.
Background
The polyurethane paving material has both protection and decoration characteristics, and most manufacturers fill a large amount of inorganic filler in the formula system from the consideration of cost optimization, so that the impact absorption performance of the material is reduced.
A foam hole structure is created in the paving material structure through a foaming technology, and an air bag in the structure has the functions of energy absorption and buffering, so that the motion protection function of the material can be improved; meanwhile, the foaming structure reduces the material density and optimizes the raw material cost.
Common polyurethane foaming techniques include physical foaming and chemical foaming.
In the patent CN108064254A, dimethyl ether is used as a physical foaming agent and is added during construction, but the dimethyl ether is a flammable and explosive chemical, and the addition in a construction site has safety risk. And the physical foaming agent has higher price, so that the physical foaming method has higher cost.
In addition, the common polyurethane chemical foaming method is that isocyanate groups react with water to generate carbon dioxide gas for foaming, and is safe and low in cost compared with a physical method. In the prior art, water is directly added into a combined material as a chemical foaming agent (patent CN1081020620A), but the raw materials of the combined material contain more oleophilic substances, so that water is difficult to uniformly and effectively disperse in a system, and the foaming uniformity is influenced; in addition, esters with a certain acid value are used as plasticizers in common combined materials, such as acetyl tributyl citral, chlorinated palm oil methyl ester and the like, so that the reactivity of isocyanate groups and water is reduced, and the foaming efficiency is influenced; furthermore, the existence of water in the system forms a competitive reaction to the gel reaction of the system, which affects the curing performance of the system and prolongs the surface drying and actual drying time of the system.
Therefore, the construction stability of the microporous polyurethane paving material at the present stage is not high, the microporous polyurethane paving material is sensitive to the environmental temperature and humidity conditions, incomplete or uneven foaming is easy to occur, and the quality of the material is difficult to effectively control on site.
Disclosure of Invention
The invention aims to solve the problems that a microporous polyurethane elastic material is low in construction stability, sensitive to environmental temperature and humidity conditions, easy to foam incompletely or unevenly and the like.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
the first aspect of the present invention provides a polyamine chain extender, wherein the polyamine chain extender is 4, 4' -bis-sec-isopropylaminomethyl diphenylmethane, and the structural formula of the polyamine chain extender is:
the preparation method of the 4, 4' -bis-sec-isopropylaminomethyl diphenylmethane comprises the following steps:
(a) reacting 4,4 '-bis (aminomethyl) diphenylmethane with acetone in the presence of hydrogen and a catalyst to produce 4, 4' -bis-sec-isopropylaminomethyl diphenylmethane;
the reaction scheme is as follows:
in the step (a), the molar ratio of 4, 4' -bis (aminomethyl) diphenylmethane to acetone is 1: 3.0-5.0, preferably 1: 3.5-4.5.
In the step (a), the catalyst is a palladium/hydrogen type zeolite catalyst, wherein the content of palladium in the catalyst accounts for 0.2-1%, preferably 0.5% of the mass of the catalyst; the amount of the catalyst is 1-4%, preferably 2-3% of the mass of the 4, 4' -bis (aminomethyl) diphenylmethane.
In the step (a), hydrogen is used for pressure adjustment, and the pressure is 2-5MPa, preferably 2.5-4 MPa;
the reaction temperature in the step (a) is 100-150 ℃, preferably 110-140 ℃;
the pressure in the invention is relative pressure.
In a second aspect of the present invention, there is provided a surface modification treatment agent, which is composed of the polyamine chain extender and the reactive tertiary amine catalyst, wherein the mass ratio of the polyamine chain extender to the reactive tertiary amine catalyst is 2 to 9: 1, preferably 3 to 8: 1;
the reactive tertiary amine catalyst simultaneously contains active hydrogen groups (-OH, -NH)2NH-) and a tertiary amine structure selected from one or more of N, N, N ', N "-tetramethyl-N" -3-aminopropyldiethylenetriamine, bis (tetramethyldiethylenetriaminopropyl) amine, N, N, N ' -trimethyl-N ' -hydroxyethylbisaminoethyl ether, N, N, N ' -trimethyl-N ' -aminopropylbisaminoethyl ether, N, N, N ' -trimethyl-N ' -hydroxyethylethylenediamine.
In a third aspect of the present invention, there is provided a modified calcium hydroxide, which is prepared by the following steps: the calcium oxide reacts under the action of the surface modification treatment agent and the deionized water to generate modified calcium hydroxide;
wherein the mass ratio of the calcium oxide to the surface modification treatment agent is 10: 0.5-3, preferably 10: 1-2;
the mass ratio of calcium oxide to deionized water is 1: 10-30, preferably 1: 15-25;
the reaction temperature is 50-95 ℃, preferably 60-80 ℃, and the reaction time is 1-4 hours, preferably 2-3 hours.
The invention also provides a microporous polyurethane elastic material, which comprises an isocyanate prepolymer component, a combined material component and a catalyst component;
the isocyanate prepolymer component comprises the following components in parts by weight:
polyether polyols 30 to 70, preferably 40 to 60;
plasticizers 1 to 30, preferably 5 to 15;
10-40, preferably 15-35, of polyisocyanate;
the composite material comprises the following components in parts by weight:
the catalyst component is an environment-friendly organic metal catalyst, such as one or more of zinc neodecanoate, bismuth neodecanoate and dibutyltin didodecyl sulfide, and the dosage of the catalyst component is 0.1-0.6% of the mass of the component of the combined material, and the catalyst component represents that the grades of BiCAT8018 and BiCAT Z which are the leading parts in the United states, Bi2010, Zn1910, Valikat14H2 and the like in the American department in Belgium.
In the microporous polyurethane elastic material, the polyether polyol in the isocyanate prepolymer component and the composite material component generally has an average functionality of 2-3 and an average molecular weight of 1000-6500, and represents products with trademarks of Wanhua chemical C2010, C2020, C2040, C2140, F3135, F3056D and the like.
In the microporous polyurethane elastic material, the plasticizer in the isocyanate prepolymer component and the combined material component is one or more of environment-friendly long-chain chlorinated paraffin (52# chlorinated paraffin), tributyl citrate (TBC), acetyl tributyl citrate (ATBC), dioctyl terephthalate (DOTP), chlorinated palm oil methyl ester, epoxy soybean methyl oleate and the like.
In the microporous polyurethane elastic material, diisocyanate diphenylmethane and derivatives thereof are selected as polyisocyanates in an isocyanate prepolymer component, and the representative brands are MDI-50, MDI-100 and MDI-100LL of Wanhua chemistry.
In the microporous polyurethane elastic material, the chain extender in the composition material components is selected from liquid arylamine chain extenders dimethylthiodiaminotoluene (DMTDA), 3, 5-diethyltoluenediamine (DETDA), 4' -bis-sec-butylaminodiphenylmethane, 1, 4-bis-sec-butylaminobenzene and the like, and the representative brands are E300 and E100 of the Yabao company, Wanalink6200 and Wanalink1104 of Wanhua chemistry.
In the microporous polyurethane elastic material, the conventional solid filler in the composition material component is one or more of calcium carbonate, talcum powder, kaolin, white carbon black, magnesium oxide and the like.
In the microporous polyurethane elastic material, the modified calcium hydroxide in the composition is the modified calcium hydroxide.
In the microporous polyurethane elastic material, the carbon dioxide catcher in the composition material components is one or more of monoethanolamine, diethanolamine, triethanolamine, diisopropanolamine, methyldiethanolamine and the like.
In the microporous polyurethane elastic material, the isocyanate index is 1-1.5, preferably 1.1-1.4.
The preparation method of the microporous polyurethane elastic material of the invention can be as follows: and adding the isocyanate prepolymer component, the combined material component and the catalyst component into a stirrer according to a ratio, dispersing for 1-2 min, pouring the uniformly dispersed materials into a mold, and standing and curing to obtain the microporous elastomer material sample block.
The invention has the beneficial effects that:
(1) the surface modification treating agent provided by the invention has a hydrogen bond anchoring functional group and can modify the surface of calcium hydroxide.
(2) The modified calcium hydroxide provided by the invention is well dispersed in a combined material system, and carbon dioxide is absorbed to release water during construction and then reacts with isocyanate groups to generate carbon dioxide, so that in-situ foaming is realized, and the uniformity of foam holes is improved.
(3) The surface of the modified calcium hydroxide provided by the invention is anchored with a reactive tertiary amine catalyst, and the modified calcium hydroxide can be hydrogen-bonded with water molecules generated in the process of generating calcium carbonate from calcium hydroxide, so that the reaction of water and isocyanate groups is promoted, and the foaming efficiency is improved; and in the reaction process, the reactive tertiary amine catalyst can react with NCO groups and is chemically linked to a polyurethane molecular chain, so that the TVOC cannot be contributed.
(4) The surface of the modified calcium hydroxide provided by the invention is anchored with a polyamine chain extender, which can react with isocyanate groups first to decover the calcium hydroxide and release reaction heat, thereby promoting the reaction of calcium hydroxide for absorbing carbon dioxide and the reaction of the isocyanate groups with water.
(5) The microporous polyurethane elastic material prepared by using the modified calcium hydroxide has the advantages of high construction stability, uniform material pores, and good impact absorption performance and mechanical property.
Drawings
FIG. 1 is a nuclear magnetic spectrum of 4, 4' -bis-sec-isopropylaminomethyl diphenylmethane of the product of example 1.
Detailed Description
The invention is further illustrated by the following examples, but is not limited to the examples set forth.
The conditions for gas chromatography were: an Agilent DB-5 chromatographic column, wherein the injection port temperature is 280 ℃, the FID detector temperature is 300 ℃, the column flow rate is 1.5ml/min, the hydrogen flow rate is 35ml/min, the air flow rate is 350ml/min, the temperature programming mode is that the temperature is kept for 2min at 50 ℃, and the temperature is increased to 280 ℃ at 10 ℃/min and kept for 10 min.
Example 1
Preparation of 4, 4' -bis-sec-isopropylaminomethyl diphenylmethane:
113g of 4, 4' -bis (aminomethyl) diphenylmethane (warham elmer corporation), 113g of acetone and 2.6g of a palladium/hydrogen type zeolite catalyst (palladium content 0.5%, Changsha Yirui chemical materials Co., Ltd.) were put into a high-pressure reactor, and the air in the reactor was replaced 3 times with nitrogen gas at 0.3 MPa; then, hydrogen gas was introduced to replace the nitrogen gas in the reactor for 3 times, and hydrogen gas was introduced to pressurize the reactor to 3 MPa. Heating and stirring the mixture at the temperature of 130 ℃, and keeping the hydrogen pressure unchanged in the reaction process. After 5h of reaction, the temperature is reduced and the material is discharged if the hydrogen pressure is observed not to be reduced any more. And distilling the reaction solution at normal pressure and 105 ℃ to remove impurities to obtain the target product. Carbon spectrum analysis was performed using a Bruker AVANCE iii 400Hz nmr spectrometer with CDCl3 as the solvent, and the results are shown in fig. 1.
Example 2
Preparation of 4, 4' -bis-sec-isopropylaminomethyl diphenylmethane:
100g of 4, 4' -bis (aminomethyl) diphenylmethane (Wuhan Elmer company), 110g of acetone and 2.5g of palladium/hydrogen type zeolite catalyst (palladium content 0.5%, Changsha Yirui chemical materials Co., Ltd.) were put into a high-pressure reactor, and the air in the reactor was replaced 3 times with nitrogen gas at 0.3 MPa; then, hydrogen gas is introduced to replace nitrogen in the reactor for 3 times, and hydrogen gas is introduced to pressurize the reactor to 3.2 MPa. Heating and stirring the mixture at the temperature of 120 ℃, and keeping the hydrogen pressure unchanged in the reaction process. After 5h of reaction, the temperature is reduced and the material is discharged if the hydrogen pressure is observed not to be reduced any more. And distilling the reaction solution at normal pressure and 105 ℃ to remove impurities to obtain the target product.
Example 3
Modified calcium hydroxide X:
4, 4' -bis-sec-isopropylaminomethyl diphenylmethane and bis (tetramethyldiethylenetriaminopropyl) amine [ prepared according to example 1 of CN109456455A ] were mixed in a mass ratio of 5: 1 preparing a surface modification treating agent
10g of ground calcium oxide (commercially available, with the particle size of about 1 mm) is added into a three-neck flask, 1.2g of the surface modification treatment agent is added, 200g of 70 ℃ deionized water is added, the oil bath temperature is 70 ℃, the mixture is stirred for 2 hours at the rotating speed of 250r/min, and then the pressure reduction and the water removal are carried out for 1 hour. The reaction product was dried in a vacuum oven at 100 ℃.
Example 4
Modified calcium hydroxide Y:
4,4 ' -bis-sec-isopropylaminomethyl diphenylmethane and N, N, N ' -trimethyl-N ' -aminopropyl bisaminoethyl ether (commercially available, winning and developing chemical industry) are mixed according to the mass ratio of 6: 1, preparing the surface modification treating agent.
12g of ground calcium oxide (commercially available, with the particle size of about 1 mm) is added into a three-neck flask, 1.2g of the surface modification treatment agent is added, 200g of deionized water with the temperature of 65 ℃ is added, the oil bath temperature is 65 ℃, the mixture is stirred at the rotating speed of 250r/min for 2.5h, and then the water is removed under reduced pressure for 1 h. The reaction product was dried in a vacuum oven at 100 ℃.
Example 5 and comparative examples 1 and 2
Preparing a microporous polyurethane elastic material:
table 1 partial sources of raw materials
Raw materials
Brand/name
Manufacturer of the product
Plasticizer
Acetyl tributyl citrate
Cantonese letter chemical industry
Plasticizer
52# chlorinated paraffin
Shandong rock sea
Plasticizer
Terephthalic acid dioctyl ester
Shandong rock sea
Conventional solid fillers
400 mesh calcium carbonate
Yangshan calcium carbonate plant
Conventional solid fillers
400 mesh talcum powder
Liaoning benxiang mining
The isocyanate prepolymer component (A) has the following formula:
TABLE 2 isocyanate prepolymer component I formulation
Raw materials
Brand/name
Number of parts
Polyether polyols
C2020
42
Polyether polyols
F3056D
21
Plasticizer
ATBC
5
Polyisocyanates
MDI-50
32
Total amount of
100
Polyether polyol C2020 and F3056D are added into the flask according to the formula and dehydrated for 2h under vacuum at 105 ℃. Cooling to 70 ℃, adding MDI-50, heating to 80 ℃, reacting for 2h, adding ATBC, cooling to 50 ℃, and discharging. Obtaining the isocyanate prepolymer component I.
The formula of the combined material (group B) is as follows:
table 3 formulation of the components of the compositions of example 5 and comparative examples 1 and 2
Adding polyether polyol, a plasticizer, a chain extender and a carbon dioxide catcher into a flask according to the formula, heating to 60 ℃, dispersing for 20min, adding a conventional solid filler, heating to 105 ℃, and carrying out vacuum dehydration for 2 h. Wherein, for example 5 and comparative example 2, modified calcium hydroxide and water were added before discharging, and discharged for use after dispersing for 0.5 h.
Catalyst component (group c): valikat14H2, Eimeridae, Belgium.
Determining the proportion of the group A and the group B according to the isocyanate index of 1.25, wherein the dosage of the group C is 0.4 percent of the mass of the group B, uniformly stirring the three components, pouring, preparing a sample block and carrying out related performance test.
The test of the impact absorption and vertical deformation performance of the material is carried out according to the requirements in GB 36246-2018.
Table 4 block property testing of example 5 and comparative examples 1 and 2
Test items
Example 5
Comparative example 1
Comparative example 2
Surface drying time/h
5
6
8
Actual drying time/h
15
16
20
Surface hardness/A after 24h
35
35
26
Core Density/(g/cm)3)
1.32
1.52
1.41
Impact absorption/%)
41.3
24.4
36.5
Standard deviation of shock absorption
3％
3％
8％
Vertical deformation/mm
1.76
0.97
1.43
Standard deviation of vertical deformation
3％
3％
7％
Cross-sectional state of the article
Uniform pores
Almost without bubble holes
The pores have different sizes
As can be seen from table 4, also as a micro-foaming formulation, example 5 has better curing property, better density reduction efficiency, and more uniform cell structure than comparative example 2, thereby having more stable, uniform and superior impact absorption properties.
Examples 6 and 7
Preparing a microporous polyurethane elastic material:
the plasticizer and conventional solid filler sources are as in table 1.
The isocyanate prepolymer component (A) has the following formula:
TABLE 5 isocyanate prepolymer component II formulation
Raw materials
Brand/name
Number of parts
Polyether polyols
C2020
43.5
Polyether polyols
F3056D
22.5
Plasticizer
DOTP
5
Polyisocyanates
MDI-50
29
Total amount of
100
Polyether polyol C2020 and F3056D are added into the flask according to the formula and dehydrated for 2h under vacuum at 105 ℃. Cooling to 70 ℃, adding MDI-50, heating to 80 ℃, reacting for 2h, adding DOTP, cooling to 50 ℃, discharging to obtain the isocyanate prepolymer component II.
The formula of the combined material (group B) is as follows:
table 6 formulation of the composition of example 6
Table 7 formulation of the composition of example 7
Raw materials
Brand/name
Number of parts
Polyether polyols
F3056D
8
Polyether polyols
C2020
5
Plasticizer
52# chlorinated paraffin
15
Plasticizer
DOTP
15
Chain extender
Wanalink6200
1.5
Chain extender
E100
0.2
Conventional solid fillers
White carbon black
0.47
Conventional solid fillers
400 mesh talcum powder
25
Conventional solid fillers
400 mesh calcium carbonate
30
Carbon dioxide scavenger
Triethanolamine
0.2
Modified calcium hydroxide
Example 4 modified calcium hydroxide Y
0.5
Adding polyether polyol, a plasticizer, a chain extender and a carbon dioxide catcher into a flask according to the formula, heating to 60 ℃, dispersing for 20min, adding conventional solid fillers, heating to 105 ℃, carrying out vacuum dehydration for 2h, adding modified calcium hydroxide before discharging, dispersing for 0.5h, and discharging for later use.
Catalyst component (group c): the American leading BiCAT8108 and BiCAT Z are selected for compound use, and the mass ratio of BiCAT8108 to BiCAT Z in the compound catalyst is 3: 7, the C groups used in examples 6 and 7 were obtained.
Determining the proportion of the group A and the group B according to the isocyanate index of 1.2, wherein the dosage of the group C is 0.1 percent of the mass of the group B, uniformly stirring the three components, pouring, preparing a sample block and carrying out related performance test.
The test of the impact absorption and vertical deformation performance of the material is carried out according to the requirements in GB 36246-2018.
Table 8 test of sample block properties of examples 6 and 7
Test items
Example 6
Example 7
Surface drying time/h
4.5
5
Actual drying time/h
14
16
Surface hardness/A after 24h
38
35
Core Density/(g/cm)3)
1.37
1.30
Impact absorption/%)
40.1
41.2
Standard deviation of shock absorption
3％
2％
Vertical deformation/mm
1.66
1.78
Standard deviation of vertical deformation
3％
2％
Cross-sectional state of the article
Uniform pores
Uniform pores