CN111363282B - Surface modified nickel-aluminum hydrotalcite/polyvinyl alcohol nano composite film and preparation method thereof - Google Patents
Surface modified nickel-aluminum hydrotalcite/polyvinyl alcohol nano composite film and preparation method thereof Download PDFInfo
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Abstract
The invention provides a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film and a preparation method thereof, wherein the method comprises the following steps: obtaining nickel-aluminum layered double hydroxide; dispersing the nickel-aluminum layered double hydroxide in water, adding tannic acid powder, stirring for adsorption, adding titanium salt to obtain a reaction solution, reacting the reaction solution for 0.5-3h, cleaning and drying to obtain surface modified nickel-aluminum hydrotalcite; dispersing the surface modified nickel-aluminum hydrotalcite in water, adding polyvinyl alcohol, stirring, heating to 95-120 ℃, heating for 0.5-2h until the polyvinyl alcohol is completely dissolved, and removing bubbles to obtain a mixed solution; and transferring the mixed solution into a polytetrafluoroethylene mold to dry for 12-36h to obtain a uniform film. The TA-Ti particle compound formed by Tannic Acid (TA) and titanium salt is used for coating the modified layered double hydroxide to form a more stable double-crosslinking coating layer, and the composite material has good comprehensive performance in barrier property, antibacterial property and mechanical property.
Description
Technical Field
The invention relates to the technical field of packaging film materials, and in particular relates to a surface modified nickel-aluminum hydrotalcite/polyvinyl alcohol nano composite film and a preparation method thereof.
Background
With the application of the packaging material in the life of people becoming more and more extensive, the demand of people for the packaging material is increasing day by day, and the packaging film material which has good gas barrier property, strong ultraviolet light shielding function and biodegradability will be a great trend for future development. This is the potential and promise of PVA. Polyvinyl alcohol (PVA) is a water-soluble polymeric material with multiple hydroxyl groups, and is increasingly used as a packaging film material, as well as a drug delivery system and an artificial biomedical device because of its excellent biocompatibility, biodegradability, water solubility, and the like [4 ]. However, polyvinyl alcohol is inferior in both water resistance and stability, and its application is limited. To improve its properties, it is conventional to blend it with other materials. However, so far, relatively few studies have been reported on PVA/LDHs composite materials.
The LDHs are also called anions or hydrotalcite-like compounds, and can utilize the intercalation property of a layered compound host under the action of strong polar molecules and the interchangeability of interlayer ions to introduce some functional guest substances into interlayer gaps and spread the interlayer distance so as to form a pillared layered compound. The LDHs-polymer nano composite material is very suitable for improving the performance because of large length-diameter ratio, uniform dispersity and large interface area between the polymer and the nano film. However, the layered structure of LDHs generates strong interlayer electrostatic interaction, so that its dispersion in the PVA matrix becomes a big problem. The LDHs tend to be stacked together to form a layered structure with a thickness of several tens of nanometers, which is disadvantageous for the polymer chain segment to penetrate into the layered structure, and therefore, the LDHs are often required to be modified in order to be inserted into the polymer.
Disclosure of Invention
The invention aims to provide a preparation method of a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film, which is simple and feasible and is easy for industrial production.
The invention also aims to provide a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film which has good barrier property, antibacterial property and mechanical comprehensive performance.
The technical problem to be solved by the invention is realized by adopting the following technical scheme.
The invention provides a preparation method of a surface modified nickel-aluminum hydrotalcite/polyvinyl alcohol nano composite film, which comprises the following steps:
obtaining nickel-aluminum layered double hydroxide;
dispersing the nickel-aluminum layered double hydroxide in water, adding tannic acid powder, stirring for adsorption, adding titanium salt to obtain a reaction solution, reacting the reaction solution for 0.5-3h, cleaning and drying to obtain surface modified nickel-aluminum hydrotalcite;
dispersing the surface modified nickel-aluminum hydrotalcite in water, adding polyvinyl alcohol, heating to 95-120 ℃ under stirring for 0.5-2h until the polyvinyl alcohol is completely dissolved, and removing bubbles to obtain a mixed solution;
and transferring the mixed solution into a polytetrafluoroethylene mold to dry for 12-36h to obtain a uniform film.
Further, in a preferred embodiment of the present invention, the obtaining of the nickel aluminum layered double hydroxide specifically includes:
dispersing nickel-containing metal salt, aluminum-containing metal salt and urea in water, reacting for 6-36 h at 120-180 ℃, and cleaning and drying to obtain the nickel-aluminum layered double hydroxide.
Further, in a preferred embodiment of the present invention, the nickel-containing metal salt is selected from at least one of nickel chloride, nickel sulfate, nickel nitrate and hydrates thereof; the aluminum-containing metal salt is selected from at least one of aluminum chloride, aluminum sulfate, aluminum nitrate and aluminum acetate.
Further, in the preferred embodiment of the present invention, the ratio of the amount of the nickel metal salt, the aluminum metal salt and the urea is 1.05-2:1: 4.
Further, in a preferred embodiment of the present invention, the mass concentration of the nickel aluminum layered double hydroxide in the reaction solution is 0.1 to 1 g/L.
Further, in a preferred embodiment of the present invention, the mass concentration of the tannic acid powder in the reaction solution is 0.1 to 1 g/L.
Further, in a preferred embodiment of the present invention, the titanium salt is selected from at least one of titanium tetrachloride, titanium tetraiodide, titanium tetrabromide, titanium sulfate, and titanyl sulfate; the mass concentration of the titanium salt in the reaction liquid is 0.01-0.05 g/L.
Further, in a preferred embodiment of the present invention, the mass percentage of the surface-modified nickel aluminum hydrotalcite in the surface-modified nickel aluminum hydrotalcite/polyvinyl alcohol nanocomposite film is 0.5 to 5 wt%.
Further, in a preferred embodiment of the present invention, the adding of polyvinyl alcohol and stirring are performed while raising the temperature to 95-120 ℃ and heating for 0.5-2h until all polyvinyl alcohol is dissolved, specifically comprising the following steps:
stirring at room temperature for 10-20min, heating to 95-100 deg.C, stirring for 20-60min, heating to 100 deg.C and 110 deg.C, stirring for 10-20min, and heating to 110 deg.C and 120 deg.C until the polyvinyl alcohol is completely dissolved.
The invention also provides a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film, which is prepared by the preparation method.
The surface modified nickel-aluminum hydrotalcite/polyvinyl alcohol nano composite film and the preparation method thereof have the following beneficial effects:
the preparation method provided by the invention coats the modified layered double hydroxide by using a TA-Ti particle compound formed by Tannic Acid (TA) and titanium salt. Different from the common single TA-metal ion complexing system, the hydrolysis reaction and the chelation reaction of the titanium salt occur simultaneously, and TiO2And TA-Ti (IV) complex can be used as a cross-linking agent and simultaneously introduced into the reticular coating layer, so that a more stable double cross-linked coating layer can be formed. Among them, Tannic Acid (TA) is a typical natural polyphenol substance, and is rich in catechol and kaolinite groups. The functional groups not only help to improve the adhesion of the complex on the surface of the material, but also have active crosslinking sites for certain metal ions and organic molecules. The TA-metal ion complex coated film will show better performance and the coating is more stable.
The invention utilizes titaniumTitanium dioxide (TiO) produced in hydrolysis reactions of salts2) Loaded on LDHs in situ. TiO 22The LDHs is a common inorganic antibacterial agent, and the LDHs is endowed with antibacterial property in the process of coating and modifying the LDHs, so that the composite material has good comprehensive performance in barrier property, antibacterial property and mechanical property.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is an SEM image of NiAl-LDHs in example 1 of the present invention;
FIG. 2 is an SEM image of LDHs @ TA-Ti in example 1 of the present invention;
FIG. 3 is a graph showing mechanical properties of example 1 of the present invention and comparative example 1;
FIG. 4 is a stress-strain curve for inventive examples 1-5 and comparative example 1;
FIG. 5 is a UV spectrum of example 1 of the present invention and comparative example 1;
fig. 6 is the result of the antibacterial performance test of example 2 of the present invention and comparative example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are not indicated by manufacturers and are commercially available.
The surface-modified nickel aluminum hydrotalcite/polyvinyl alcohol nanocomposite film and the preparation method thereof according to the embodiment of the present invention are specifically described below.
The embodiment of the invention provides a preparation method of a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film, which comprises the following steps:
first, a nickel-aluminum layered double hydroxide (NiAl-LDHs) was obtained. The NiAl-LDHs can be obtained by coprecipitation, urea, ion exchange, hydrothermal synthesis and the like, and the invention is not particularly limited. Compared with common MgAl-LDHs, ZnAl-LDHs and other layered double hydroxides, NiAl-LDHs has better ultraviolet shielding property, can be used for active packaging materials, and prevents food from being oxidized and deteriorated.
Preferably, the method for obtaining the nickel-aluminum layered double hydroxide by adopting a urea method comprises the following steps: dispersing nickel-containing metal salt, aluminum-containing metal salt and urea in water, reacting for 6-36 h at 120-180 ℃, and cleaning and drying to obtain the nickel-aluminum layered double hydroxide. The urea method utilizes that urea is neutral at low temperature after being dissolved and can form a uniform solution with other metal salts, when the temperature exceeds 90 ℃, the urea starts to decompose and slowly releases ammonia, the ammonia is dissolved to gradually increase the pH of the solution, and CO decomposed from the urea reaches a certain degree2Dissolved in water to form CO3 2-As interlayer anions. In the synthesis process, the pH inside the solution is always kept consistent, and the prepared product has good crystallinity and larger size.
Further, the nickel-containing metal salt is selected from at least one of nickel chloride, nickel sulfate, nickel nitrate and hydrates thereof; the aluminum-containing metal salt is selected from at least one of aluminum chloride, aluminum sulfate, aluminum nitrate and aluminum acetate.
Further, the amount ratio of the nickel metal salt, the aluminum metal salt and the urea is 1.05-2:1: 4. The raw material ratio has the best value for synthesizing high-performance NiAl-LDHs, and the synthesized LDHs have complete structure and high regularity and can achieve better interface performance and barrier effect. Wherein the molar mass of the aluminium-containing metal salt is generally not more than half the molar mass of the nickel-containing metal salt. Proper excess of the precipitant is beneficial to better coprecipitation, but the use amount of the precipitant is too high, impurities are easily obtained, precipitation is too fast, other phases are easily formed, and the crystallinity is poor. At this ratio, the product yield is optimized.
And then dispersing the nickel-aluminum layered double hydroxide in water, adding tannic acid powder, stirring and adsorbing, then adding titanium salt to obtain a reaction solution, reacting the reaction solution for 0.5-3h, and cleaning and drying to obtain the surface modified nickel-aluminum hydrotalcite (LDHs @ TA-Ti).
In the process, Tannic Acid (TA) containing abundant catechol and kaolinite groups is utilized, so that the strong adhesion of the complex on the surface of the material is facilitated, and the complex has active crosslinking sites for certain metal ions and organic molecules. TA is fully adsorbed on the surface of NiAl-LDHs, then titanium salt is added, after the titanium salt is dissolved in water, hydrolysis reaction and complexation simultaneously occur, and formed TiO2And the TA-Ti (IV) complex can be used as a cross-linking agent and simultaneously introduced into the reticular coating layer, so that a more stable double cross-linked coating layer can be formed, the structure is more stable, the complex is used as a nano particle additive to be compounded with PVA, the toughening and the reinforcement of the nano composite film are facilitated, and the mechanical property of the nano composite film is improved.
Further, the mass concentration of the nickel aluminum layered double hydroxide in the reaction liquid is 0.1-1 g/L.
Further, the mass concentration of the tannic acid powder in the reaction liquid is 0.1-1 g/L.
Further, the titanium salt is selected from at least one of titanium tetrachloride, titanium tetraiodide, titanium tetrabromide, titanium sulfate and titanyl sulfate. The mass concentration of the titanium salt in the reaction solution is 0.01-0.05 g/L.
And then dispersing the surface modified nickel aluminum water-skiing (LDHs @ TA-Ti) stone in water, adding polyvinyl alcohol, heating to 95-120 ℃ under stirring, heating for 0.5-2h until the polyvinyl alcohol is completely dissolved, and removing bubbles to obtain a mixed solution.
Further, the mass percent of the surface modified nickel aluminum hydrotalcite in the surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film is 0.5-5 wt%. More preferably, the mass percent of the surface modified nickel aluminum hydrotalcite is 0.1-0.3 wt%. The strength of a composite depends on the size and distribution of defects in the specimen, which in turn determines the amount of load it can withstand before failing. When a certain amount of surface modified nickel aluminum hydrotalcite is added, the toughness of the composite material is improved through heterogeneous nucleation and interface interaction of the system. When more LDHs @ TA-Ti (> 5 wt%) is added to the LDHs @ TA-Ti/PVA nanocomposite film, the probability of forming defects (e.g., agglomeration, etc.) will increase. Therefore, the PVA matrix treated by the proper LDHs @ TA-Ti has better mechanical property than that of the untreated PVA matrix.
Further, the steps specifically include: stirring at room temperature for 10-20min, heating to 95-100 deg.C, stirring for 20-60min, heating to 100 deg.C and 110 deg.C, stirring for 10-20min, and heating to 110 deg.C and 120 deg.C until the polyvinyl alcohol is completely dissolved. The multi-stage temperature gradual heating and intermittent stirring heating are adopted to reach the proper temperature, so that excessive generation of bubbles can be reduced, and scorching is avoided.
And finally, transferring the mixed solution into a polytetrafluoroethylene mold and drying for 12-36h to obtain a uniform film. Specifically, the mixed solution is horizontally placed in a polytetrafluoroethylene mold by a solution casting method, and is dried at a constant temperature to obtain a film with uniform thickness.
The embodiment of the invention also provides a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film, which is prepared according to the preparation method. The surface modified nickel aluminum hydrotalcite is compounded in the PVA matrix, so that the composite material has good mechanical property, gas barrier property, strong ultraviolet light shielding property and antibacterial property, and has great application potential and prospect in the field of packaging film materials.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The embodiment provides a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film, which is obtained according to the following steps:
s1, mixing 0.907g of Ni (NO)3)2·6H2O (3.12mmol), 0.585g of Al (NO)3)3·9H2Dispersing O (1.56mmol) and 0.380g urea (6.32mmol) in 32ml distilled water, mixing and carrying out ultrasonic treatment for 5min to uniformly disperse, transferring the mixed solution into an autoclave to react for 24h at 140 ℃, taking out a product, carrying out ultrasonic cleaning and centrifuging three times, and carrying out freeze drying to obtain nickel-aluminum layered double hydroxide NiAl-LDHs;
s2, adding 0.1g of the NiAl-LDHs into 200ml of pure water, performing ultrasonic treatment for 10min to uniformly disperse the NiAl-LDHs, then adding 0.1g of tannin powder, stirring for 15min to fully adsorb the tannin powder, and measuring 2.6 mu L of TiCl by using a liquid transfer gun4Adding the reaction solution into an aqueous solution to obtain a reaction solution, continuously stirring the reaction solution for reaction for 2 hours, carrying out centrifugal washing on a product for three times, and freeze-drying to obtain surface modified nickel-aluminum hydrotalcite LDHs @ TA-Ti;
s3, adding 0.005g of LDHs @ TA-Ti into pure water, adding 0.7g of polyvinyl alcohol, stirring, heating to 98 ℃ for 1h until the polyvinyl alcohol is completely dissolved, and removing bubbles to obtain a mixed solution;
s4, transferring the mixed solution into a polytetrafluoroethylene mold, and drying in a drying oven at 30 ℃ for 24 hours to obtain a uniform film (LATP-0.5%).
Examples 2 to 5
Examples 2-5 provide a surface-modified nickel aluminum hydrotalcite/polyvinyl alcohol nanocomposite film, which is different from example 1 in that the addition amounts of LDHs @ TA-Ti in examples 2-5 are 0.010g (LATP-1%), 0.031g (LATP-3%), 0.053g (LATP-5%), and 0.075g (LATP-7%), respectively.
Example 6
The embodiment provides a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film, which is obtained according to the following steps:
s1, mixing 0.476g of Ni (NO)3)2·6H2O (1.638mmol), 0.585g of Al (NO)3)3·9H2Dispersing O (1.56mmol) and 0.380g urea (6.32mmol) in 32ml distilled water, mixing and carrying out ultrasonic treatment for 5min to uniformly disperse, transferring the mixed solution into an autoclave to react for 24h at 140 ℃, taking out a product, carrying out ultrasonic cleaning and centrifuging three times, and carrying out freeze drying to obtain nickel-aluminum layered double hydroxide NiAl-LDHs;
s2, adding 0.1g of the NiAl-LDHs into 200ml of pure water, performing ultrasonic treatment for 10min to uniformly disperse the NiAl-LDHs, then adding 0.1g of tannin powder, stirring for 15min to fully adsorb the tannin powder, and measuring 2.6 mu L of TiCl by using a liquid transfer gun4Adding into water solution to obtain reaction solution, continuously stirring the reaction solution for reaction for 2h, centrifuging the product for three timesWashing with water, and freeze-drying to obtain surface-modified nickel-aluminum hydrotalcite LDHs @ TA-Ti;
s3, adding 0.005g of LDHs @ TA-Ti into pure water, adding 0.7g of polyvinyl alcohol, stirring, heating to 98 ℃ for 1h until the polyvinyl alcohol is completely dissolved, and removing bubbles to obtain a mixed solution;
s4, transferring the mixed solution into a polytetrafluoroethylene mold, and drying in a drying oven at 30 ℃ for 24 hours to obtain a uniform film (LATP-0.5%).
Example 7
The embodiment provides a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film, which is obtained according to the following steps:
s1, mixing 0.907g of Ni (NO)3)2·6H2O (3.12mmol), 0.585g of Al (NO)3)3·9H2Dispersing O (1.56mmol) and 0.380g urea (6.32mmol) in 32ml distilled water, mixing and carrying out ultrasonic treatment for 5min to uniformly disperse, transferring the mixed solution into an autoclave to react for 24h at 140 ℃, taking out a product, carrying out ultrasonic cleaning and centrifuging three times, and carrying out freeze drying to obtain nickel-aluminum layered double hydroxide NiAl-LDHs;
s2, adding 0.1g of NiAl-LDHs into 200ml of pure water, performing ultrasonic treatment for 10min to uniformly disperse, then adding 0.1g of tannic acid powder, stirring for 15min to fully adsorb, measuring 5.8 mu L of TiCl 4 by using a liquid transfer gun, adding the TiCl 4 into an aqueous solution to obtain a reaction solution, continuously stirring the reaction solution for reaction for 2h, performing centrifugal washing on the product for three times, and performing freeze-drying to obtain surface-modified nickel-aluminum hydrotalcite LDHs @ TA-Ti;
s3, adding 0.005g of LDHs @ TA-Ti into pure water, adding 0.7g of polyvinyl alcohol, stirring, heating to 98 ℃ for 1h until the polyvinyl alcohol is completely dissolved, and removing bubbles to obtain a mixed solution;
s4, transferring the mixed solution into a polytetrafluoroethylene mold, and drying in a drying oven at 30 ℃ for 24 hours to obtain a uniform film (LATP-0.5%).
Comparative example 1
This comparative example provides a pure polyvinyl alcohol (PVA) film, obtained according to the following steps:
s1, adding polyvinyl alcohol into pure water, heating to 98 ℃ under stirring, heating for 1h until the polyvinyl alcohol is completely dissolved, and removing bubbles to obtain a solution;
s2, transferring the solution into a polytetrafluoroethylene mold, and drying in a drying oven at 30 ℃ for 24 hours to obtain a uniform film (PVA).
Test example 1
NiAl-LDHs and LDHs @ TA-Ti in example 1 were subjected to liquid nitrogen treatment and brittle fracture to obtain a fracture surface. The microscopic morphology was observed using a Scanning Electron Microscope (SEM) (Sigma500, Zeiss, Germany).
Referring to FIGS. 1-2, FIG. 1 is an SEM image of NiAl-LDHs, and FIG. 2 is an SEM image of LDHs @ TA-Ti. Compared with LDHs, the interface definition of the LDHs @ TA-Ti and the PVA matrix is reduced, which shows that the compatibility is improved, the form of the LDHs @ TA-Ti is rough, and a granular TA-Ti coating layer can be observed on the surface of the LDHs @ TA-Ti.
Test example 2
The tensile strength and elongation at break of the nanocomposite films provided in comparative example 1 and examples 1 to 5 were measured, and the results are shown in fig. 3 to 4.
Fig. 3 is a mechanical property curve of example 1 and comparative example 1. It can be seen that when the content of LDHs @ TA-Ti is increased from 0 to 0.5 wt% compared to pure PVA, the elongation at break of LATP-0.5% is increased by 8.6%, indicating that the system improves the toughness of the material through heterogeneous nucleation and interfacial interaction. It is noted here that when the content of LDHs @ TA-Ti is 1 wt% or less, the tensile strength and elongation at break of the nanocomposite film are generally in an upward trend; when the addition amount exceeds 1 wt%, both are gradually reduced, and at 7 wt%, the tensile strength is lower than that of pure PVA; when the addition amount is not more than 3 wt%, the elongation at break is higher than that of the pure PVA.
FIG. 4 is a stress-strain curve of LDHs @ TA-Ti/PVA nanocomposites and pristine PVA, the resulting mechanical parameters are shown in Table 1. As can be seen from this figure, the material initially undergoes elastic deformation, followed by no significant plastic deformation and necking stages, followed by fracture after strain hardening. The σ - ε image further illustrates that when LDHs @ TA-Ti is added in an amount of not more than 1 wt%, the tensile strength gradually increases and is maximal at 1 wt% (49.6 MPa); then increasing LDHs @ TA-Ti, but decreasing the strength. In Table 1, the parameters of the nanofilm are generally increased relative to neat PVA for the elastic modulus and increase with increasing LDHs @ TA-Ti content in the nanocomposite. The modulus of elasticity of the fillers (nanoscale LDHs) is 2470MPa, so this increasing tendency is also a consequence of the high modulus of the fillers. Therefore, the LDHs @ TA-Ti plays a role in strengthening and toughening the film.
TABLE 1 mechanical Property parameters
Test example 3
The UV spectrums of example 1 and comparative example 1 were measured, and the results are shown in FIG. 5. As can be seen, the pure PVA film has higher ultraviolet transmittance within the wavelength range of 190-400nm, and the transmittance of the pure PVA film to the ultraviolet light at the wavelength of 261nm is 58.08 percent; with the increase of LDHs @ TA-Ti, the transmittance of the material to ultraviolet light is gradually reduced; when the content is more than 1 wt%, the transmittance is almost decreased to 0.
In the wavelength range of visible light (400-800nm), the light transmittance of the pure PVA film exceeds 65 percent; when more LDHs @ TA-Ti is added, the transmittance of the film is reduced. Indicating that the material can effectively shield light. The light barrier property is also an important factor for food preservation, and can avoid the photo-oxidation of organic compounds and the degradation of pigments such as vitamins and the like.
Test example 4
The oxygen transmission and water vapor transmission rates of comparative example 1 and example 2 were measured, and the results are shown in table 2.
TABLE 2 Barrier Property measurements
From the above table, it can be seen that, compared with the unmodified pure PVA film of comparative example 1, the TA-Ti particle composite of example 2 coated with the modified layered double hydroxide has the water vapor transmission rate reduced by 52%, the oxygen transmission rate reduced by 41%, and the barrier property improved significantly.
Test example 5
Counting the colony number in the culture dish soaked with different films by using a colony counter, and evaluating and determining the antibacterial property of NiAl-LDHs, LDHs @ TA-Ti and LDHs @ TA-Ti/PVA-1% in a blank control group, a comparative example 1 and an example 2 on escherichia coli by the colony number. Specifically, the Escherichia coli strain was inoculated into LB solid medium using an inoculating loop and cultured in an incubator at 37 ℃ for 24 hours. Inoculating the grown bacterial colony in LB liquid culture medium, carrying out constant temperature shaking culture in a constant temperature culture shaker at 37 ℃ for 24h, diluting through the LB liquid culture medium, adjusting the corresponding bacterial concentration to be 1 × 108 CFU/mL, continuously culturing in the LB liquid culture medium for 12h, and diluting the bacterial suspension until the absorbance value at 600nm is-0.1. 150 μ l of the inoculum was dropped into a conical flask containing 15mL of liquid medium at a inoculum concentration of 1X 105 CFU/mL. The film samples (diameter: 10mm) were immersed in the flasks containing the bacterial solution, respectively, to allow the films to be sufficiently soaked in the bacterial solution, incubated at 37 ℃ for 24 hours with shaking, spread on a solid medium, and placed in a constant temperature incubator shaker for further incubation for 24 hours, the results are shown in Table 3 and FIG. 6.
TABLE 3 measurement of antibacterial Properties
| Sample processing | Bacterial count (CFU/cm)2) | Antibacterial ratio (%) |
| Blank control | 7.4×107 | - |
| NiAl-LDHs | 4.2×107 | 43.24 |
| LDHs@TA-Ti | 1.2×104 | 99.98 |
| Comparative example 1 | 4.6×107 | 37.84 |
| LDHs@TA-Ti/PVA-1％ | 2.5×105 | 99.66 |
As can be seen, the bacterial concentration of the pure PVA film reached 4.6X 107CFU/cm2. The bacterial concentration of the nickel-aluminum layered double hydroxide reaches 4.2 multiplied by 107CFU/cm2. After the NiAl-LDHs is subjected to surface coating modification, the concentration of the bacteria of the LDHs @ TA-Ti is reduced to 1.2 multiplied by 104CFU/cm2. Compared with a pure PVA film, the concentration of bacteria in the LDHs @ TA-Ti/PVA film with LDHs @ TA-Ti is further reduced to 2.5 multiplied by 105CFU/cm2And exhibits excellent antibacterial activity.
In conclusion, the modified layered double hydroxide is coated by the TA-Ti particle compound formed by the Tannic Acid (TA) and the titanium salt, and TiO is generated in the hydrolysis reaction of the titanium salt2And TA-Ti (IV) complex forms a double cross-linked net-shaped coating layer, so that the stability and the mechanical comprehensive performance of the PVA film are improved. With titanium dioxide (TiO)2) As a sterile antibacterial agent, the composite film is loaded on LDHs in situ, so that the composite film has excellent antibacterial property and barrier property, and has good performance in the field of packaging materialsThe application prospect of (1).
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
Claims (4)
1. A preparation method of a surface modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film is characterized by comprising the following steps:
obtaining nickel-aluminum layered double hydroxide;
dispersing the nickel-aluminum layered double hydroxide in water, adding tannic acid powder, stirring for adsorption, adding titanium salt to obtain a reaction solution, reacting the reaction solution for 0.5-3h, cleaning and drying to obtain surface modified nickel-aluminum hydrotalcite;
dispersing the surface modified nickel-aluminum hydrotalcite in water, adding polyvinyl alcohol, heating to 95-120 ℃ under stirring for 0.5-2h until the polyvinyl alcohol is completely dissolved, and removing bubbles to obtain a mixed solution;
transferring the mixed solution into a polytetrafluoroethylene mold and drying for 12-36h to obtain a uniform film;
wherein the mass concentration of the nickel-aluminum layered double hydroxide in the reaction solution is 0.1-1 g/L;
wherein the mass concentration of the tannic acid powder in the reaction liquid is 0.1-1 g/L;
wherein the titanium salt is selected from at least one of titanium tetrachloride, titanium tetraiodide, titanium tetrabromide, titanium sulfate and titanyl sulfate; the mass concentration of the titanium salt in the reaction liquid is 0.01-0.05 g/L;
wherein, the obtaining of the nickel-aluminum layered double hydroxide specifically comprises the following steps: dispersing nickel-containing metal salt, aluminum-containing metal salt and urea in water, reacting for 6-36 h at 120-180 ℃, and cleaning and drying to obtain nickel-aluminum layered double hydroxide;
wherein the amount ratio of the nickel metal salt, the aluminum metal salt and the urea is 1.05-2:1: 4;
wherein the mass percent of the surface modified nickel-aluminum hydrotalcite in the surface modified nickel-aluminum hydrotalcite/polyvinyl alcohol nano composite film is 0.5-5 wt%.
2. The method for preparing the surface-modified nickel aluminum hydrotalcite/polyvinyl alcohol nanocomposite film according to claim 1, wherein the nickel-containing metal salt is at least one selected from nickel chloride, nickel sulfate, nickel nitrate and hydrates thereof; the aluminum-containing metal salt is selected from at least one of aluminum chloride, aluminum sulfate, aluminum nitrate and aluminum acetate.
3. The method for preparing the surface-modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film according to claim 1, wherein the polyvinyl alcohol is added, stirred, heated to 95-120 ℃ for 0.5-2h until the polyvinyl alcohol is completely dissolved, and the method specifically comprises the following steps:
stirring at room temperature for 10-20min, heating to 95-100 deg.C, stirring for 20-60min, heating to 100 deg.C and 110 deg.C, stirring for 10-20min, and heating to 110 deg.C and 120 deg.C until the polyvinyl alcohol is completely dissolved.
4. A surface-modified nickel aluminum hydrotalcite/polyvinyl alcohol nano composite film, which is characterized by being prepared according to the preparation method of any one of claims 1 to 3.
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