A polydopamine-halloysite composite material, preparation method and application thereof

Abstract

A method for forming polydopamine-halloysite composite material, where a nano-halloysite is heated, to 50 °C or less, and agitated with deionised water, to form suspension, component A. Dopamine hydrochloride is dissolved in deionised water to form component B. Components A and B are mixed and sonicated before centrifugation to obtain a solid material. The solid material is washed and dried to yield polydopamine-nano-halloysite composite material. The mass ratio of nano-halloysite to dopamine hydrochloride is between 1:1 and 6:1. The material may be used in polyurethane elastomers up to 1 wt%.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a polydopamine-halloysite composite material, a preparation method and an application thereof, which belongs to the technical field of composite material. BACKGROUND

[0002] Halloysite is a natural mineral with promising perspectives for application, which has unique morphology structure and excellent physical and chemical properties such as favorable water dispersion, different properties in inner and outer walls, high adsorption, biocompatibility, etc., thus has become a hotspot of research in recent years. As a typical kandite, which exhibits a tubular morphology in most cases, it has recently been widely used as slow-release container, catalyst carrier, organic polymer filler, hydrogen storage material and nanomaterial template, etc., having important application value. The small size and large specific surface area of halloysite can produce quantum and surface effects, and interfacial interaction with polymers, which can be used as fillers to improve the mechanical properties, flame retardant, thermal stability, and other properties of polymers. Based on its characteristics, halloysite is often used as a carrier template and composited with other materials, playing a synergistic role by modification and other means, to further enhance the reinforcing effect of the filler in polymer materials.

[0003] Dopamine (DA, or 3-hydroxytyramine, 3,4-dihydroxyphenylethylamine) is an endogenous nitrogen-containing organic compound, which is an intermediate product of tyrosine (an aromatic amino acid) during the metabolism of dihydroxyphenylalanine, and also known as catechol ethylamine or hydroxytyramine, one of the catecholamines, having a molecular formula of CTHnNCU It is a white or off-white crystals, easily soluble in water. Under alkaline conditions, the dopamine quinone can be formed after deprotonation and oxidation of the dopamine monomer catechol, however, the dopamine quinone is structurally unstable so it will be further oxidized and undergo intramolecular rearrangement and cross-linking to form dark brown or black polydopamine. Due to its adhesion, reducibility and biocompatibility, dopamine and composite materials derived therefrom have been gradually used in various fields. In addition to simple coating of the matrix, based on its diverse binding sites, poly dopamine generated by oxidation and polymerization of dopamine can be modified to secondary modification, accomplishing functionalization of material surface, which has a promising application perspective.

[0004] Usually when contacted with air under weakly alkaline conditions (pH 8.5) or catalyzed by weakly acid conditions (pH 4.0) accompanied by a small amount of substances, dopamine (DA) can be polymerized on the surface of a carrier almost anywhere, forming polydopamine (PDA) nanofilms, which eventually generate polydopamine-filler reinforced composites. In other words, the preparation of polydopamine-filler reinforced composites usually requires acid or alkali treatments, and the effluent generated during the process presents issues of environmental pollution.

[0005] Dopamine hydrochloride has a morphology of white crystalline powder, with the chemical formula of CsHnCINOz, melting point of 248 °C~250 °C, easily soluble in water, soluble in methanol and 95% ethanol(heated), and also soluble in sodium hydroxide solution; however, it is insoluble in ether, chloroform, and benzene. Dopamine hydrochloride is an organic compound, which is prepared into the form of hydrochloride for preservation since the free form of dopamine is unstable and easy to be oxidized. There are no studies that utilize dopamine hydrochloride as a source of coating in filler reinforced system, and halloysite power as carrier template, completing self-polymerization reaction under non-alkaline conditions. SUMMARY

[0006] In view of the above, the purpose of the present disclosure is to provide a polydopamine-halloysite composite material, a preparation method, and an application thereof. The present invention takes halloysite as the carrier template in filler reinforcement system, and dopamine as the adhesive material, which are combined by means of the specific combination of halloysite structure and morphology and with the aid of an aqueous solution, and then via interlayer interactions as well as hydrogen bonding. For the first time, the oxidative self-polymerization reaction of dopamine with halloysite carrier template as a binder under non-alkaline conditions has been realized, where polydopamine-halloysite composite fillers have been prepared.

[0007] For the purposes above, the present disclosure provides the following technical solutions. A method of preparing a polydopamine-halloysite composite material, wherein the method comprises the steps of: (1) mixing nano-halloysites and adding the mixture into water with a purity above the purity of deionized water (water with a purity greater than or equal to the purity of deionized water, such as deionized water, ultrapure water, etc.), and heating, stirring and dispersing evenly, then obtaining a component A; (2) mixing dopamine hydrochlorides and water with a purity above the purity of deionized water, and obtaining a component B; (3) mixing the component A and the component B, resting after ultrasonic vibration for even dispersion, and obtaining a suspension C; and (4) centrifugally separating the suspension C, collecting, washing, and drying precipitates, then obtaining a polydopamine-halloysite composite material; wherein the structure of the nano-halloysites is selected from one or more of the following shapes: sheet, disk and feather; the mass ratio of the nano-halloysites to the dopamine hydrochlorides is 1-6:1.

[0008] Preferably, in the step (1), the mass ratio of the nano-halloysites to the dopamine hydrochlorides is 2-4:1.

[0009] Preferably, in the step (1), the amount ratio of the nano-halloysites to the water is 0.1-0.2 g: 15-25 mL.

[0010] Preferably, in the step (1), the temperature of the heating is 50 °C or less, and the time of the stirring is 0.5-2 h.

[0011] Preferably, in the step (2), the dopamine hydrochlorides are preserved in the form of hydrochloride of dopamine, referred to as CsHnNOi HC1, and the amount ratio of the dopamine hydrochlorides to the water is 0.05-0.1 g: 15-25 mL.

[0012] Preferably, in the step (3), the time of the ultrasonic vibration is 0.5-2 h.

[0013] Preferably, in the step (4), the centrifugal speed of the centrifugally separating is 4000 r / min or more, and the temperature of the drying is 70 °C or more.

[0014] A polydopamine-halloysite composite material, wherein the composite material is prepared by the above-mentioned methods.

[0015] Preferably, the composite material is formed by combining the nanohalloysites, the dopamine hydrochlorides and the water via interlayer interaction and hydrogen bonding, where the polydopamine is adhesively coated on the surface of the nano-halloysites, forming a lamellar structure.

[0016] Use of the polydopamine-halloysite composite material, wherein the composite material is used as a filler for polyurethane elastomers.

[0017] Preferably, the composite material is added in the amount of 0.2%~l%.

[0018] Benefits

[0019] The present invention provides a polydopamine-halloysite composite material, preparation method and application thereof, wherein the method does not involve any acid or alkali solution, instead, carries out the self-polymerization reaction of dopamine completely under neutral conditions, and ultimately produces a polydopamine-halloysite composite filler. The entire process is simple, convenient, environmentally friendly and pollution-free. The specific structure of nano-halloysites after surface modification by polydopamine has improved dispersity in high-molecular polymers, and the prepared polydopamine-halloysite composites can be used as fillers to enhance the mechanical properties of polyurethane, and elongation at break has been increased. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The invention is described in further details in combination with specific examples in the following.

[0021] Example 1

[0022] 2 parts by mass of nano-halloysites (in the shape of sheet, disk and / or feather) and 250 parts by mass of distilled water were added into a glass container, stirred and heated and dispersed by ultrasonic vibration, and the temperature of the reactor was controlled to be no more than 50 °C, stirred at preserved temperature for 1 h, and a white or off-white solution A was obtained. 1 part by mass of dopamine hydrochlorides and 250 parts by mass of water were added into a glass container, and an evenly mixed solution B was obtained after stirring for 1 hour. Mix the solution A and the solution B and introduce into a centrifugal tube, and the mixture was rested after dispersion by ultrasonic vibration for 0.5 h. Then the suspension C with black powder was obtained. Suspension C was separated by centrifugation in a centrifuge for 5 min, with the speed of over 4000r / min, after which it was washed several times by distilled water and ethanol, and subject to another centrifugation, repeated for 3 cycles, then followed by drying in an oven at 70 °C, and polydopamine-halloysite composite filler was thus obtained.

[0023] 45.01 g of diphenylmethane diisocyanate and 55.01 g of polytetrahydrofuran ether glycol were added into a 250 mL three necked flask, and the temperature was elevated to 80 °C, and the stock was stirred at a rate of 200 r / min to mix evenly, and after reaction for 4 h the polyurethane prepolymer was obtained. 0.3225 g of the prepared prepolymer was taken and mixed with 25mL of di-n-butylamine in toluene solution, and heated in water bath at 50 °C for 20 min for complete reaction, then 6 drops of bromocresol blue indicator were added and followed by 50 mL of isopropanol to completely dissolve the indicator. 0.1 mol / L of dilute hydrochloric acid was used for titration, indicating that the content of isocyanate in the prepolymer was 12.46%. At room temperature, 35.99 g of polytetrahydrofuran ether glycol (molecular weight 2000), 10.01 g of polyether 330N polyol (molecular weight 4950) and 3.76 g of 1,4-butanediol 5 were sequentially added into a container, and after adding 44.02 g of the prepared polymer and 0.476 g of the polydopamine-halloysite composite filler, the materials were stirred at a stirring rate of 2000 r / min for 20 s, and then it was poured to a polytetrafluoroethylene container, followed by curing in an oven at 70 °C for 2 h. And the polyurethane elastomer sample 1 with 0.5% mass fraction of polydopamine-halloysite composite filler was obtained.

[0024] The tensile strength as well as the elongation at break of the polydopamine-halloysite composite filler reinforced polyurethane elastomer sample 1 were tested with reference to the standard GB / T1040.3-2006. It was determined that the tensile strength of the prepared polydopamine- halloysite-polyurethane elastomer sample was 19.46 MPa and elongation at break was 515.28%.

[0025] Example 2

[0026] 4 parts by mass of nano-halloysites in multiple morphologies (in the shape of sheet, disk and / or feather) and 250 parts by mass of distilled water were added into a glass container, stirred and heated and dispersed by ultrasonic vibration, and the temperature of the reactor was controlled to be no more than 50 °C, stirred at preserved temperature for 1 h, and a white or off-white solution A was obtained. 1 parts by mass of dopamine hydrochlorides and 250 parts by mass of water were added into a glass container, and an evenly mixed solution B was obtained after stirring for 1 hour. Mix the solution A and the solution B and introduce into a centrifugal tube, and the mixture was rested after dispersion by ultrasonic vibration for 0.5 h Then the suspension C with black powder was obtained. Suspension C was separated by centrifugation in a centrifuge for 5 min, with the speed of over 4000 r / min, after which it was washed several times by distilled water and ethanol, and subject to another centrifugation, repeated for 3 cycles, then followed by drying, and polydopamine-halloysite composite filler was thus obtained.

[0027] 45.01 g of diphenylmethane diisocyanate and 55.01 g of polytetrahydrofuran ether glycol were added into a 250 mL three necked flask, and the temperature was elevated to 80 °C, and the stock was stirred at a rate of 200 r / min to mix evenly, and after reaction for 4 h the polyurethane prepolymer. 0.3225 g of the prepared prepolymer 6 was taken and mixed with 25 mL of di-n-butylamine in toluene solution, and heated in water bath at 50 °C for 20 min for complete reaction, then 6 drops of bromocresol blue indicator were added and followed by 50 mL of isopropanol to completely dissolve the indicator. 0.1 mol / L of dilute hydrochloric acid was used for titration, indicating that the content of isocyanate in the prepolymer was 12.46%. At room temperature, 35.99 g of polytetrahydrofuran ether glycol (molecular weight 2000), 10.01 g of polyether 330N polyol (molecular weight 4950) and 3.76 g of 1,4-butanediol were sequentially added into a container, and after adding 44.02 g of the prepared polymer and 0.476 g of the polydopamine-halloysite composite filler, the materials were stirred at a stirring rate of 2000 r / min for 20 s; and then it was poured to polytetrafluoroethylene container, followed by curing in an oven at 70 °C for 2 h. And the polyurethane elastomer sample 2 with 0.5% mass fraction of polydopamine-halloysite composite filler was obtained.

[0028] The tensile strength as well as the elongation at break of the polydopamine-halloysite composite filler reinforced polyurethane elastomer sample 2 were tested with reference to the standard GB / T1040.3-2006. It was determined that the tensile strength of the prepared polydopamine- halloysite-polyurethane elastomer sample was 18.57 MPa and elongation at break was 501.34%.

[0029] Comparative example 1

[0030] 2 parts by mass of nano-halloysites in multiple morphologies (in the shape of rod, ball and / or fiber) and 250 parts by mass of distilled water were added into a glass container, stirred and heated and dispersed by ultrasonic vibration, and the temperature of the reactor was controlled to be no more than 50 °C, stirred at preserved temperature for 1 h, and a white or off-white solution A was obtained. 1 parts by mass of dopamine hydrochlorides and 250 parts by mass of water were added into a glass container, and an evenly mixed solution B was obtained after stirring for 1 hour. Mix the solution A and the solution B and introduced into a centrifugal tube, and the mixture was rested after dispersion by ultrasonic vibration for 0.5 h Then the suspension C with white powder was obtained where no dopamine self-polymerization reaction occurred. Suspension C was separated by centrifugation in a centrifuge for 5 min, with the speed of over 4000 r / min, after which it was washed several times by distilled water and 7 ethanol, and subject to another centrifugation, repeated for 3 cycles, then followed by drying, and halloysite nanofiller powder was thus obtained.

[0031] 45.01 g of diphenylmethane diisocyanate and 55.01 g of polytetrahydrofuran ether glycol were added into a 250 mL three necked flask, and the temperature was elevated to 80 °C, and the stock was stirred at a rate of 200 r / min to mix evenly, and after reaction for 4 h the polyurethane prepolymer was obtained. 0.3225 g of the prepared prepolymer was taken and mixed with 25 mL of di-n-butylamine in toluene solution, and heated in water bath at 50 °C for 20 min for complete reaction, then 6 drops of bromocresol blue indicator were added and followed by 50 mL of isopropanol to completely dissolve the indicator; 0.1 mol / L of dilute hydrochloric acid was used for titration, indicating that the content of isocyanate in the prepolymer was 12.46%. At room temperature, 35.99 g of polytetrahydrofuran ether glycol (molecular weight 2000), 10.01g of polyether 330N polyol (molecular weight 4950) and 3.76g of 1,4-butanediol were sequentially added into a container, and after adding 44.02 g of prepared polymer and 0.476 g of the halloysite filler, the materials were stirred at a stirring rate of 2000 r / min for 20 s; and then it was poured to a polytetrafluoroethylene container, followed by curing in an oven at 70 °C for 2 h. And the polyurethane elastomer sample 3 with 0.5% mass fraction of halloysite filler in multiple morphologies was obtained.

[0032] The tensile strength as well as the elongation at break of the halloysite filler reinforced polyurethane elastomer sample 3 were tested with reference to the standard GB / T 1040.3-2006. It was determined that the tensile strength of the prepared halloysite-polyurethane elastomer sample was 18.16 MPa and elongation at break was 486.71%.

[0033] Comparative example 2

[0034] 45.01 g of diphenylmethane diisocyanate and 55.01 g of polytetrahydrofuran ether glycol were added into a 250 mL three necked flask, and the temperature was elevated to 80 °C, and the stock was stirred at a rate of 200r / min to mix evenly, and after reaction for 4 h the polyurethane prepolymer was obtained. 0.3225 g of the prepared prepolymer was taken and mixed with 25 mL of di-n-butylamine in toluene solution, and heated in water bath at 50 °C for 20 min for complete reaction, then 6 8 drops of bromocresol blue indicator were added and followed by 50 mL of isopropanol to completely dissolve the indicator. 0.1 mol / L of dilute hydrochloric acid was used for titration, indicating that the content of isocyanate in the prepolymer was 12.46%. At room temperature, 35.99 g of polytetrahydrofuran ether glycol (molecular weight 2000), 10.01 g of polyether 330N polyol (molecular weight 4950) and 3.76 g of 1,4-butanediol were sequentially added into a container, and after adding 44.02 g of the prepared polymer and 0.476 g of the halloysite filler in multiple morphologies (in the shape of sheet, disk and / or feather), the materials were stirred at a stirring rate of 2000 r / min for 20 s, and then it was poured to polytetrafluoroethylene container, followed by curing in an oven at 70 °C for 2 h. And the polyurethane elastomer sample 4 with 0.5% mass fraction of halloysite filler in multiple morphologies was obtained.

[0035] The tensile strength as well as the elongation at break of the halloysite filler reinforced polyurethane elastomer sample 4 were tested with reference to the standard GB / T 1040.3-2006. It was determined that the tensile strength of the prepared halloysite-polyurethane elastomer sample was 17.13 MPa and elongation at break was 489.53%.

[0036] Comparing the experimental results and mechanical properties performed by the samples in examples 1-2 and comparative examples 1-2, it can be concluded that surface modification can be carried out on the specific morphology of halloysite filler (sheet, disk and / or feather) by dopamine hydrochlorides, and the polydopamine-halloysite composite filler can be thus prepared under conditions without acid or alkali treatment, and the preparation process of which is environmentally friendly and pollution-free; whereas under aqueous conditions, none of the halloysite fillers with rod-shapes, ball-shaped and fiber-shaped halloysite filler react with dopamine hydrochlorides and they are unable to generate and prepare polydopamine-halloysite composite filler. Overall, the generation of polydopamine allows it to coat and modify the surface of halloysite filler (in the shape of sheet, disk and / or feather), which increases the interfacial compatibility between filler reinforced phase and the polyurethane matrix, and further releases and strengthens the properties of the halloysite-polyurethane composite material.

[0037] In summary, the present disclosure includes but not limited to the embodiments above. Any equivalent substitution or partial improvement under the protection scope and principle of the present disclosure should be deemed as within in the scope of protection of the present disclosure.

Claims

1. A method of preparing a polydopamine-halloysite composite material, wherein the method comprises the steps of:(1) mixing nano-halloysites and adding the mixture into water with a purity above the purity of deionized water (water with a purity greater than or equal to the purity of deionized water or above, such as deionized water, ultrapure water, etc.), and heating, stirring and dispersing evenly, and obtaining a component A;(2) mixing dopamine hydrochlorides and water with a purity above the purity of deionized water, and obtaining a component B;(3) mixing the component A and the component B, resting after ultrasonic vibration for even dispersion, and obtaining a suspension C; and(4) centrifugally separating the suspension C, collecting, washing and drying precipitates, then obtaining a polydopamine-halloysite composite material; andwherein the structure of the nano-halloysites are selected from one or more of the following shapes: sheet, disk and feather;the mass ratio of the nano-halloysites to the dopamine hydrochlorides is 1-6:1.

2. The method of preparing the polydopamine-halloysite composite material of claim 1, wherein in the step (1), the mass ratio of the nano-halloysites to the dopamine hydrochlorides is 2-4:1.

3. The method of preparing the polydopamine-halloysite composite material of claim 1, wherein in the step (1), the amount ratio of the nano-halloysites to the water is 0.1-0.2 g: 15-25 mL.

4. The method of preparing the polydopamine-halloysite composite material of claim 1, wherein in the step (1), the temperature of the heating is 50 °C or less, and the time of the stirring is 0.5-2 h.

5. The method of preparing the polydopamine-halloysite composite material of claim 1, wherein in the step (2), the dopamine hydrochlorides are preserved in the form of hydrochloride of dopamine, referred to as QHnXCh HC1, and the amount ratio of the dopamine hydrochlorides to the water is 0.05-0.1 g: 15-25 mL.

6. The method of preparing the polydopamine-halloysite composite material of claim 1, wherein in the step (3), the time of the ultrasonic vibration is 0.5-2 h.

7. he preparation method for polydopamine-halloysite composite material of claim 1, wherein in the step (4), the centrifugal speed of the centrifugally separating is 4000 r / min or more, and drying temperature is 70 °C or more.

8. A polydopamine-halloysite composite material, wherein the composite material is prepared by the method of any one of claims 1-7; andthe composite material is formed by combining the nano-halloysites, the dopamine hydrochlorides and the water via interlayer interaction and hydrogen bonding, where the polydopamine is adhesively coated on the surface of the non-halloysites, forming a lamellar structure.

9. Use of the polydopamine-halloysite composite material of claim 8, wherein the composite material is used as a filler for polyurethane elastomers.

10. Use of the polydopamine-halloysite composite material of claim 9, wherein the composite material is added in the amount of 0.2%~l%.