CN113103560A - High-strength polyurethane material and preparation method thereof - Google Patents

High-strength polyurethane material and preparation method thereof Download PDF

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Publication number
CN113103560A
CN113103560A CN202110401784.9A CN202110401784A CN113103560A CN 113103560 A CN113103560 A CN 113103560A CN 202110401784 A CN202110401784 A CN 202110401784A CN 113103560 A CN113103560 A CN 113103560A
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polyurethane
strength
strain
polyurethane material
stretching
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CN113103560B (en
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王志刚
徐翠
张娟
王学会
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University of Science and Technology of China USTC
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University of Science and Technology of China USTC
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/005—Shaping by stretching, e.g. drawing through a die; Apparatus therefor characterised by the choice of materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2075/00—Use of PU, i.e. polyureas or polyurethanes or derivatives thereof, as moulding material

Abstract

The invention relates to the technical field of high polymer materials, in particular to a high-strength polyurethane material and a preparation method thereof. The preparation method of the high-strength polyurethane material provided by the invention comprises the following steps: circularly stretching the polyurethane sample strip to obtain a high-strength polyurethane material; during the cyclic stretching treatment, the stretching strain increases in a gradient manner. Compared with the original polyurethane material, the high-strength polyurethane material is obtained by a cyclic stretching treatment mode, the tensile strength and the later modulus of the high-strength polyurethane material are both obviously improved, the strain hardening is obvious, the method is simple, convenient and easy to implement, the reinforcing effect is obvious, and the application range of the polyurethane material can be widened.

Description

High-strength polyurethane material and preparation method thereof
Technical Field
The invention relates to the technical field of high polymer materials, in particular to a high-strength polyurethane material and a preparation method thereof.
Background
Polyurethane elastomer is an important high molecular material, and is generally prepared by gradually polymerizing hydroxyl-terminated oligomers such as polyester, polyether, polyolefin and the like, isocyanate and low molecular alcohols or amines. The polyurethane elastomer not only has the elasticity of rubber, but also has the strength of plastic, thereby receiving wide attention and having wide application prospect in the living and industrial fields of rubber, plastic, paint, adhesive, sealing gasket and the like.
At present, with the continuous development of society and economy, higher requirements are put forward on the mechanical properties of polyurethane, and polyurethane materials with higher strength are needed. The common method for improving the strength of polyurethane is by blending with other resins, increasing the crystallinity of soft and hard segments, or adjusting the content of soft and hard segments. Chinese patent CN109294251A discloses a high-strength and high-modulus polyurethane material formed by a polyurethane resin composition and application thereof. Stirring, mixing and thermally curing the epoxy functionalized polyphenyl ether microsphere particles, polyol, isocyanate and the like to obtain the high-strength high-modulus polyurethane material. However, the method needs to perform epoxy functional modification on the polyphenylene oxide microsphere particles, and the process is complex. Chinese patent CN109369877A discloses a high-strength polyurethane waterproof paint and a preparation method thereof. The amide group is introduced into a polyurethane molecular chain, and can form intermolecular hydrogen bonds with ester groups and urethane groups in molecules by utilizing the strong polarity of the amide group and the hydrogen bond action between the amide group and the polyurethane molecular chain, so that the breaking strength of the polyurethane resin is obviously improved. Although the method can improve the mechanical property of the polyurethane material to a certain extent, the effect is not obvious.
Disclosure of Invention
In view of this, the technical problem to be solved by the present invention is to provide a high-strength polyurethane material and a preparation method thereof.
The invention provides a preparation method of a high-strength polyurethane material, which comprises the following steps:
circularly stretching the polyurethane sample strip to obtain a high-strength polyurethane material;
during the cyclic stretching treatment, the stretching strain increases in a gradient manner.
Preferably, the breaking strength of the polyurethane sheet for preparing the polyurethane sample strip is 33-38 MPa, and the breaking elongation is 520-730%.
Preferably, the polyurethane sheet from which the polyurethane splines are made is selected from a first polyurethane sheet or a second polyurethane sheet;
the first polyurethane sheet has a breaking strength of 34MPa and a breaking elongation of 730%;
the second polyurethane sheet had a breaking strength of 37MPa and an elongation at break of 526%.
Preferably, the speed of the cyclic stretching is 5-500 mm/min.
Preferably, the strain increment of the cyclic stretching is 1 to 20%.
Preferably, the temperature of the cyclic stretching is 23 ℃.
Preferably, the cyclic stretching process includes:
cycle stretch to 10% at 1% strain increment, cycle stretch to 20% at 2% strain increment, cycle stretch to 40% at 5% strain increment, cycle stretch to 100% at 10% strain increment, and cycle stretch to maximum strain at 20% strain increment;
the maximum strain is 450-700%.
Preferably, the polyurethane sample strip is a dumbbell-shaped sample strip;
the dumbbell-shaped sample strips are (10-51) mm x (1-4) mm in size.
The invention also provides a high-strength polyurethane material prepared by the preparation method.
The invention provides a preparation method of a high-strength polyurethane material, which comprises the following steps: circularly stretching the polyurethane sample strip to obtain a high-strength polyurethane material; during the cyclic stretching treatment, the stretching strain increases in a gradient manner. Compared with the original polyurethane material, the high-strength polyurethane material obtained by the cyclic stretching treatment method has the advantages that the tensile strength and the later modulus are both obviously improved, the strain hardening is obvious, the method is simple and easy to implement, the reinforcing effect is obvious, and the application range of the polyurethane material can be widened.
Drawings
FIG. 1 is a comparison of the profiles of a comparative example 1 polyurethane sheet of the present invention and a high strength polyurethane material of example 1;
FIG. 2 is an IR spectrum of a polyurethane sheet of comparative example 1 of the present invention;
FIG. 3 is an AFM phase diagram of a polyurethane sheet of comparative example 1 of the present invention;
FIG. 4 is an AFM particle size distribution plot of comparative example 1 of the present invention;
FIG. 5 is a DSC curve of a polyurethane sheet of comparative example 1 of the present invention;
FIG. 6 is a cyclic tensile curve of a comparative example 1 polyurethane material of the present invention;
FIG. 7 is a monotonic tensile stress-strain curve for the high strength polyurethane material of example 1 of the present invention and the polyurethane sheet of comparative example 1;
FIG. 8 is a plot of the small angle X-ray scattering of comparative example 1 polyurethane sheet of the present invention and the high strength polyurethane material of example 1;
FIG. 9 is a cyclic tensile curve of a comparative example 1 polyurethane material of the present invention;
FIG. 10 is a monotonic tensile stress-strain curve along and perpendicular to the stretch direction for the high strength polyurethane material of example 2 of the present invention;
FIG. 11 is a comparison of the profiles of the polyurethane sheet of comparative example 2 of the present invention and the high strength polyurethane material of example 3;
FIG. 12 is an IR spectrum of a polyurethane sheet of comparative example 2 of the present invention;
FIG. 13 is a DSC curve of a polyurethane sheet of comparative example 2 of the present invention;
FIG. 14 is a cyclic tensile curve of a comparative example 2 polyurethane material of the present invention;
FIG. 15 is a monotonic tensile stress-strain curve for the high strength polyurethane material of example 3 of the present invention and the polyurethane sheet of comparative example 2;
FIG. 16 is a plot of the small angle X-ray scattering of comparative example 2 polyurethane sheet of the present invention and the high strength polyurethane material of example 3.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a preparation method of a high-strength polyurethane material, which comprises the following steps:
circularly stretching the polyurethane sample strip to obtain a high-strength polyurethane material;
during the cyclic stretching treatment, the stretching strain increases in a gradient manner.
In the present invention, the cyclic stretching treatment of the polyurethane sample refers to a process in which, when the polyurethane sample is stretched to a predetermined strain, the stretching is stopped until the strain of the polyurethane sample is reduced to zero, and the cycle is repeated. During the cyclic stretching process, the stretching strain is increased in a gradient manner until a preset maximum strain is reached. The predetermined maximum strain is in the strain hardened region of the polyurethane specimen near but not exceeding the elongation at break of the unidirectional tensile of the polyurethane specimen.
In certain embodiments of the present invention, the polyurethane splines are cut from a polyurethane sheet by a cutter.
In some embodiments of the present invention, the breaking strength of the polyurethane sheet for preparing the polyurethane sample strip is 33 to 38MPa, and the breaking elongation is 520 to 730%.
In certain embodiments of the present invention, the polyurethane from which the polyurethane splines are made is a polyether polyurethane or a polyester polyurethane.
In certain embodiments of the present invention, the polyurethane sheet from which the polyurethane splines are made is selected from a first polyurethane sheet or a second polyurethane sheet;
the first polyurethane sheet has a breaking strength of 34MPa and a breaking elongation of 730%;
the second polyurethane sheet had a breaking strength of 37MPa and an elongation at break of 526%.
In the present invention, the sources of the first polyurethane sheet and the second polyurethane sheet are not particularly limited, and may be made by self or may be generally commercially available.
In certain embodiments of the present invention, the first polyurethane sheet is prepared from raw materials comprising polytetrahydrofuran ether glycol, diphenylmethane diisocyanate, and 1, 4-butanediol.
In certain embodiments of the present invention, the weight ratio of polytetrahydrofuran ether glycol, diphenylmethane diisocyanate and 1, 4-butanediol is 40-41: 18-19: 3 to 4. In certain embodiments, the polytetrahydrofuran ether glycol, diphenylmethane diisocyanate, and 1, 4-butanediol are present in a mass ratio of 40: 19: 3.
in certain embodiments of the present invention, the first polyurethane sheet is prepared according to the following method:
A1) vacuumizing polytetrahydrofuran ether glycol at 108-112 ℃;
B1) mixing the polytetrahydrofuran ether glycol obtained in the step A1) and diphenylmethane diisocyanate at the temperature of 58-62 ℃, and stirring under a vacuum condition;
C1) reacting the mixture obtained in the step B1) at 75-85 ℃ for 1.5-2 h under a vacuum condition;
D1) and D) stirring and mixing the product obtained in the step C1) with 1, 4-butanediol, pressing the film at 129-131 ℃ and 5-6 MPa, and curing to obtain a first polyurethane sheet.
Step a 1):
vacuumizing under heating condition for removing water;
in some embodiments of the invention, the temperature of the evacuation is 110 ℃ and the time of evacuation is 3 hours.
Step B1):
in certain embodiments of the invention, the temperature of the mixing is 60 ℃;
the stirring method is not particularly limited in the present invention, and a stirring method known to those skilled in the art may be used. In certain embodiments of the invention, the stirring time is 1 hour.
Step C1):
in certain embodiments of the invention, the reaction is carried out at a temperature of 80 ℃ for a period of 2 hours.
Step D1):
in some embodiments of the invention, the rotation speed of the stirring and mixing is 200-300 r/min, and the time is 1-2 min;
in some embodiments of the invention, the temperature of the pressed film is 130 ℃, the pressure is 5.5MPa, and the time is 10 min; in certain embodiments of the invention, the lamination is performed in a laminator;
in some embodiments of the invention, the curing temperature is 90-110 ℃ and the curing time is 12 h;
in certain embodiments, after the curing, demolding is further included.
In certain embodiments of the present invention, the second polyurethane sheet is prepared from raw materials comprising polycaprolactone diol, diphenylmethane diisocyanate, and 1, 4-butanediol.
In some embodiments of the invention, the mass ratio of the polycaprolactone diol to the diphenylmethane diisocyanate to the 1, 4-butanediol is 25-26: 14-15: 3 to 4. In certain embodiments, the mass ratio of polycaprolactone diol, diphenylmethane diisocyanate, and 1, 4-butanediol is 26: 15: 3.
in certain embodiments of the present invention, the second polyurethane sheet is prepared according to the following method:
A2) vacuumizing polycaprolactone diol at 108-112 ℃;
B2) mixing the polycaprolactone diol obtained in the step A2) with diphenylmethane diisocyanate at the temperature of 58-62 ℃, and stirring under a vacuum condition;
C2) reacting the mixture obtained in the step B2) at 75-85 ℃ for 1.5-2 h under a vacuum condition;
D2) and C2) stirring and mixing the product obtained in the step C2) with 1, 4-butanediol, pressing the film at 129-131 ℃ and 5-6 MPa, and curing to obtain a second polyurethane sheet.
Step a 2):
vacuumizing under heating condition for removing water;
in some embodiments of the invention, the temperature of the evacuation is 110 ℃ and the time of evacuation is 3 hours.
Step B2):
in certain embodiments of the invention, the temperature of the mixing is 60 ℃;
the stirring method is not particularly limited in the present invention, and a stirring method known to those skilled in the art may be used. In certain embodiments of the invention, the stirring time is 1 hour.
Step C2):
in certain embodiments of the invention, the reaction is carried out at a temperature of 80 ℃ for a period of 2 hours.
Step D2):
in some embodiments of the invention, the rotation speed of the stirring and mixing is 200-300 r/min, and the time is 1-2 min;
in some embodiments of the invention, the temperature of the pressed film is 130 ℃, the pressure is 5.5MPa, and the time is 10 min; in certain embodiments of the invention, the lamination is performed in a laminator;
in some embodiments of the invention, the curing temperature is 90-110 ℃ and the curing time is 12 h;
in certain embodiments, after the curing, demolding is further included.
In some embodiments of the present invention, the speed of the cyclic stretching is 5 to 500 mm/min. In certain embodiments, the speed of the cyclic stretching is 10mm/min or 500 mm/min.
In certain embodiments of the invention, the cyclic stretch has a strain increase of 1% to 20%.
In certain embodiments of the present invention, the temperature of the cyclic stretching is 22 to 24 ℃. In certain embodiments of the present invention, the temperature of the cyclic stretching is 23 ℃.
In certain embodiments of the present invention, the cyclic stretching process comprises 5 stages:
the first stage is as follows: gradually cycling the stretch to a strain of 10% in 1% strain increments;
and a second stage: stretching was cycled stepwise to 20% strain in 2% strain increments;
and a third stage: gradually cycle stretch to 40% strain at 5% strain increments;
a fourth stage: gradually cycling the stretch to 100% strain in 10% strain increments;
the fifth stage: the stretch was cycled stepwise to maximum strain at 20% strain increments.
The present invention is explained for stepwise cyclic stretching to a strain of 10% in increments of strain of 1%, and the rest of the description is similar and will not be specifically described. The stretching is gradually cycled to the strain of 10% in the strain increment of 1%, specifically:
stretch to 1%, then recover to zero stress, then stretch to 2%, then recover to zero stress, and so on to stretch to 10%.
In certain embodiments of the invention, the maximum strain is 450% to 700%. In certain embodiments, the maximum strain is 660% or 540%.
In certain embodiments of the present invention, the cyclic stretching process comprises:
the stretch was cycled stepwise to a strain of 500% in 17% strain increments.
In certain embodiments of the invention, the cyclic stretching process is performed on a universal tensile testing machine.
In certain embodiments of the invention, the polyurethane splines are dumbbell-shaped splines.
In some embodiments of the invention, the dumbbell-shaped splines have dimensions of (10-51) mm x (1-4) mm. In certain embodiments, the dumbbell-shaped splines are 50mm by 4mm in size.
The source of the above-mentioned raw materials is not particularly limited in the present invention, and may be generally commercially available.
The invention also provides a high-strength polyurethane material prepared by the preparation method.
In certain embodiments of the present invention, the first polyurethane sheet is prepared according to the above-described method to obtain a high strength polyurethane material having a breaking strength of 88MPa, an initial modulus of 44.3MPa, a late modulus of 91.1MPa, and an elongation at break of 213%. The second polyurethane sheet obtained according to the above-described preparation method was a high-strength polyurethane material having a breaking strength of 72MPa, an initial modulus of 30.6MPa, a late modulus of 60.7MPa, and an elongation at break of 277%.
The cyclic stretching treatment in the invention causes the recombination and orientation of molecular chains or crystal microstructures, the reinforcing effect is obvious, and the polyurethane sample strips still have good toughness in the direction perpendicular to the stretching direction after cyclic stretching.
The preparation method of the high-strength polyurethane material provided by the invention is simple and easy to operate, environment-friendly and low in cost, and meets the requirements of industrial practical application.
Compared with the original polyurethane material, the high-strength polyurethane material obtained by the cyclic stretching treatment method has obvious strain hardening, the tensile strength can be improved from 34MPa to 88MPa, and the later modulus is improved from 6.5MPa to 91.1 MPa. The method is simple and easy to implement, has obvious reinforcing effect, and can widen the application range of the polyurethane material.
In order to further illustrate the present invention, the following examples are provided to describe a high strength polyurethane material and a preparation method thereof in detail, but should not be construed as limiting the scope of the present invention.
Comparative example 1
Polyurethane sheet a (polyurethane sheet having a breaking strength of 34MPa and an elongation at break of 730%) was not subjected to any treatment, and had a size of 50mm × 4 mm;
the preparation method of the polyurethane sheet A comprises the following steps:
40.36g of polytetrahydrofuran ether glycol (PTMG) was placed in a 100mL three-necked flask, and vacuum was applied for 3 hours under 110 ℃ oil bath to remove water. The temperature was adjusted to 60 ℃ and 18.96g of diphenylmethane diisocyanate (MDI) were added, evacuated and mechanically stirred for 1 h. The reaction was continued for 2h under vacuum with the temperature adjusted to 80 ℃. 3.16g of 1, 4-Butanediol (BDO) was added, and after stirring rapidly at a rate of 200r/min for 1.5min, the mixture was poured into a mold. Vacuumizing in a laminator at 130 ℃, standing under 5.5MPa for 10min, and aging in an oven at 100 ℃ for 12 h. And taking out and demolding to obtain the polyurethane sheet A.
Example 1
The polyurethane sheet a of comparative example 1 was subjected to cyclic stretching treatment on a universal testing machine, that is: stretching is first cycled stepwise to 10% strain at 1% strain increment, then to 20% strain at 2% strain increment, then to 40% strain at 5% strain increment, then to 100% strain at 10% strain increment, and finally to 660% maximum strain at 20% strain increment; wherein the speed of the circular stretching is 10mm/min, the temperature is 23 ℃, and the high-strength polyurethane material is obtained.
FIG. 1 is a comparison of the profiles of the polyurethane sheet of comparative example 1 and the high strength polyurethane material of example 1 according to the present invention. Wherein, fig. 1a of fig. 1 is an external view of a polyurethane sheet of comparative example 1 of the present invention, and fig. 1b of fig. 1 is an external view of a high-strength polyurethane material of example 1 of the present invention. As can be seen from fig. 1a in fig. 1, the length of the polyurethane of comparative example 1 is 50.6mm, and as can be seen from fig. 1b in fig. 1, the length of the high strength polyurethane of example 1 is 79.3 mm. After the cyclic stretching treatment, the length of the polyurethane is increased, which is caused by irreversible plastic deformation of the polyurethane, and the change of the internal microstructure of the polyurethane after the cyclic stretching treatment is shown.
FIG. 2 is an IR spectrum of a polyurethane sheet of comparative example 1 of the present invention, wherein 3286cm-1、1530cm-1Respectively has N-H expansion and bending vibration absorption peak of 2936cm-1And 2853cm-1Are each CH2Peak of asymmetric stretching vibration and symmetric stretching vibration of 1731cm-1Is C ═ O stretching vibration peak, 1222cm-1Is the deformation vibration peak of ester group O-C ═ O, 1104cm-1Is an ether bond C-O-C stretching vibration absorption peak. The polyurethane of comparative example 1 is a polyether polyurethane, as the ester group absorption peak area is significantly smaller than the ether bond absorption peak area.
Fig. 3 is an AFM phase diagram of the polyurethane sheet of comparative example 1 of the present invention, and it is apparent from fig. 3 that two phases exist, illustrating the microphase separation structure of the soft and soft segments of the polyurethane sheet of comparative example 1.
FIG. 4 is an AFM particle size distribution diagram of comparative example 1 of the present invention, and it was found that the hard segment size of polyurethane was intensively distributed at 5 to 15 nm.
FIG. 5 is a DSC curve of the polyurethane sheet of comparative example 1 of the present invention. Wherein, fig. 5a in fig. 5 is a DSC curve of the polyurethane sheet of comparative example 1 of the present invention subjected to a first heating, fig. 5b in fig. 5 is a DSC curve of the polyurethane sheet of comparative example 1 of the present invention subjected to a temperature reduction, and fig. 5c in fig. 5 is a DSC curve of the polyurethane sheet of comparative example 1 of the present invention subjected to a second heating. As can be seen in fig. 5, the first and second heating profiles are substantially identical, indicating that the sample is stable.
FIG. 6 is a cyclic tensile curve of a comparative example 1 polyurethane material of the present invention.
Fig. 7 is a monotonic tensile stress-strain curve for the high strength polyurethane material of example 1 of the present invention and the polyurethane sheet of comparative example 1. As can be seen from FIG. 7, the tensile strength in the tensile direction of the polyurethane sheet of comparative example 1 increased from 34MPa to 88MPa after the cyclic stretching treatment, the initial modulus was slightly decreased, but the late modulus increased from 6.5MPa to 91.1MPa, and the strain hardening was significant. The initial modulus is obtained by fitting data of 0% -5% strain on the tensile curve, and the later modulus is obtained by fitting data of a strain hardening area.
FIG. 8 is a graph of the small angle X-ray scattering of comparative example 1 polyurethane sheet of the present invention and the high strength polyurethane material of example 1. Wherein FIG. 8a is a small angle X-ray scattering diagram of the polyurethane sheet of comparative example 1 of the present invention, and FIG. 8b is a small angle X-ray scattering diagram of the high-strength polyurethane material of example 1 of the present invention (double arrows indicate the direction of cyclic stretching of the high-strength polyurethane material of example 1). As can be seen from fig. 8a, the polyurethane sheet of comparative example 1 has isotropy, and as can be seen from fig. 8b, the high-strength polyurethane material of example 1 has anisotropy, which illustrates that the internal microstructure of the polyurethane system is oriented after the polyurethane sheet of comparative example 1 is cyclically stretched, which is also the main reason for the great improvement of the tensile strength of the high-strength polyurethane material of example 1.
Example 2
The polyurethane sheet of comparative example 1 was subjected to cyclic stretching treatment on a universal testing machine, and was subjected to cyclic stretching stepwise to a strain of 500% in 17% strain increments, wherein the cyclic stretching speed was 500mm/min and the temperature was 23 ℃, to obtain a high-strength polyurethane material.
FIG. 9 is a cyclic tensile curve of a comparative example 1 polyurethane material of the present invention.
Fig. 10 is a monotonic tensile stress-strain curve along and perpendicular to the tensile direction for the high strength polyurethane material of example 2 of the present invention. The machine direction in fig. 10 indicates the direction along the stretching direction, and the transverse direction indicates the direction perpendicular to the stretching direction. As can be seen from fig. 10, after the rapid cycle stretching treatment, the tensile strength of the high-strength polyurethane material in the stretching direction is significantly improved, and the strain hardening is significant; the high-strength polyurethane material can still be stretched to more than 650 percent along the direction vertical to the stretching direction, and keeps excellent toughness.
Comparative example 2
Polyurethane sheet B (polyurethane sheet having a breaking strength of 37MPa and an elongation at break of 526%) had a size of 50mm × 4mm without any treatment.
The preparation method of the polyurethane sheet B comprises the following steps:
25.80g of polycaprolactone diol (PCL) was put in a 100mL three-necked flask, and vacuum was applied for 3 hours at 110 ℃ in an oil bath to remove water. The temperature was adjusted to 60 ℃ and 14.98g of diphenylmethane diisocyanate (MDI) were added, evacuated and mechanically stirred for 1 h. The reaction was continued for 2h under vacuum with the temperature adjusted to 80 ℃. 3.06g of 1, 4-Butanediol (BDO) was added, and after stirring rapidly at a rate of 200r/min for 1.5min, the mixture was poured into a mold. Vacuumizing in a laminator at 130 ℃, standing under 5.5MPa for 10min, and aging in an oven at 100 ℃ for 12 h. And taking out and demolding to obtain the polyurethane sheet B.
Example 3
The polyurethane sheet B of comparative example 2 was subjected to cyclic stretching treatment on a universal tester, that is: stretching is first cycled in steps to 10% strain at 1% strain increments, then to 20% strain at 2% strain increments, then to 40% strain at 5% strain increments, then to 100% strain at 10% strain increments, and finally to 540% maximum strain at 20% strain increments; wherein the speed of the circular stretching is 10mm/min, the temperature is 23 ℃, and the high-strength polyurethane material is obtained.
FIG. 11 is a comparison of the profiles of the polyurethane sheet of comparative example 2 of the present invention and the high strength polyurethane material of example 3. Wherein, fig. 11a of fig. 11 is an external view of the polyurethane sheet of comparative example 2 of the present invention, and fig. 11b of fig. 11 is an external view of the high-strength polyurethane material of example 3 of the present invention. As can be seen from fig. 11a in fig. 11, the length of the polyurethane of comparative example 2 is 51.0mm, and as can be seen from fig. 11b in fig. 11, the length of the high-strength polyurethane of example 3 is 67.1 mm.
FIG. 12 is an IR spectrum of a polyurethane sheet of comparative example 2 of the present invention, wherein 3286cm-1And 1530cm-1Respectively has N-H expansion and bending vibration absorption peaks of 2942cm-1And 2864cm-1Are each CH2Peak of asymmetric stretching vibration and symmetric stretching vibration of 1731cm-1Is C ═ O stretching vibration peak, 1218cm-1Is the hard segment ester group O-C ═ O deformation vibration peak, 1161cm-1Is a soft segment ester group O-C ═ O deformation vibration peak, 1068cm-1Is the stretching vibration peak of the ester group O-C ═ O, indicating that the polyurethane of comparative example 2 is a polyester polyurethane.
FIG. 13 is a DSC curve of the polyurethane sheet of comparative example 2 of the present invention. Wherein, fig. 13a in fig. 13 is a DSC curve of the polyurethane sheet of comparative example 2 of the present invention subjected to a first heating, fig. 13b in fig. 13 is a DSC curve of the polyurethane sheet of comparative example 2 of the present invention subjected to a temperature reduction, and fig. 13c in fig. 13 is a DSC curve of the polyurethane sheet of comparative example 2 of the present invention subjected to a second heating. As can be seen from FIG. 13, during the first heating, there is a small and broad endothermic peak at 60-120 ℃, which may be the dissociation of short-range ordered hard segment; the sample is crystallized at 84.2 ℃ in the process of temperature reduction; in the second heating process, the melting point of the sample is obviously lower than that of the first heating process, which indicates that the soft segment is completely crystallized in the sample preparation process.
FIG. 14 is a cyclic tensile curve of a comparative example 2 polyurethane material of the present invention.
Fig. 15 is a monotonic tensile stress-strain curve for the high strength polyurethane material of example 3 of the present invention and the polyurethane sheet of comparative example 2. As can be seen from FIG. 15, the polyurethane sheet of comparative example 2, after being subjected to the cyclic stretching treatment, had an increased tensile strength in the stretching direction from 37MPa to 72MPa, a decreased initial modulus from 59.2MPa to 30.6MPa, and an increased late modulus from 10.7MPa to 60.7 MPa. The initial modulus is obtained by fitting data of 0% -5% strain on the tensile curve, and the later modulus is obtained by fitting data of a strain hardening area. In addition, the samples after cyclic stretching still have good toughness perpendicular to the stretching direction.
FIG. 16 is a plot of the small angle X-ray scattering of comparative example 2 polyurethane sheet of the present invention and the high strength polyurethane material of example 3. Wherein FIG. 16a is a small angle X-ray scattering diagram of the polyurethane sheet of comparative example 2 of the present invention, and FIG. 16b is a small angle X-ray scattering diagram of the high-strength polyurethane material of example 3 of the present invention (double arrows indicate the direction of cyclic stretching of the high-strength polyurethane material of example 3). As can be seen from fig. 16a, the polyurethane sheet of comparative example 2 has isotropy, and as can be seen from fig. 16b, the high-strength polyurethane material of example 3 has anisotropy, which illustrates that the microstructure in the polyurethane system is oriented after the polyurethane sheet of comparative example 2 is cyclically stretched, which is also the main reason why the tensile strength of the high-strength polyurethane material of example 3 is greatly improved.
Table 1 shows the statistical tensile properties of the polyurethane sheets of comparative examples 1-2 and the high strength polyurethane materials of examples 1-3. Wherein the initial modulus is obtained by fitting data of 0% -5% strain on a stretching curve, and the later modulus is obtained by fitting data of a strain hardening area.
TABLE 1 tensile Property parameters of the polyurethane sheets of comparative examples 1-2 and the high-strength polyurethane materials of examples 1-3
Figure BDA0003020581980000121
As can be seen from table 1, the initial modulus and the late modulus of the polyurethane sheet of comparative example 2 are higher than those of the polyurethane sheet of comparative example 1, because the polyurethane sheet of comparative example 2 is easily crystallized and a crystalline structure exists in the soft segment. The initial modulus of the polyurethane sheet of comparative example 1 and the polyurethane sheet of comparative example 2 decreased after cyclic stretching, but the modulus at the later stage increased significantly. After cyclic stretching, the tensile strength of the high-strength polyurethane material of example 1 and the high-strength polyurethane material of example 3 is significantly enhanced, which is related to the rearrangement of molecular chain or crystal microstructure and the orientation of microstructure inside the system caused by cyclic stretching.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. A preparation method of a high-strength polyurethane material comprises the following steps:
circularly stretching the polyurethane sample strip to obtain a high-strength polyurethane material;
during the cyclic stretching treatment, the stretching strain increases in a gradient manner.
2. The method according to claim 1, wherein the polyurethane sheet from which the polyurethane sample strip is produced has a breaking strength of 33 to 38MPa and an elongation at break of 520 to 730%.
3. The production method according to claim 1, wherein the polyurethane sheet from which the polyurethane spline is produced is selected from a first polyurethane sheet or a second polyurethane sheet;
the first polyurethane sheet has a breaking strength of 34MPa and a breaking elongation of 730%;
the second polyurethane sheet had a breaking strength of 37MPa and an elongation at break of 526%.
4. The method according to claim 1, wherein the speed of the cyclic stretching is 5 to 500 mm/min.
5. The method of claim 1, wherein the cyclic stretching has a strain increment of 1% to 20%.
6. The production method according to claim 1, wherein the temperature of the cyclic stretching is 23 ℃.
7. The production method according to claim 1, wherein the cyclic stretching treatment includes:
cycle stretch to 10% at 1% strain increment, cycle stretch to 20% at 2% strain increment, cycle stretch to 40% at 5% strain increment, cycle stretch to 100% at 10% strain increment, and cycle stretch to maximum strain at 20% strain increment;
the maximum strain is 450-700%.
8. The production method according to claim 1, wherein the polyurethane splines are dumbbell-shaped splines;
the dumbbell-shaped sample strips are (10-51) mm x (1-4) mm in size.
9. The high-strength polyurethane material prepared by the preparation method of any one of claims 1 to 8.
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