CN110229483B - PLA (polylactic acid) nano composite material and preparation method thereof - Google Patents

Abstract

A PLA nanocomposite is prepared by melt blending a mixture comprising PLA particles, and a nanomaterial that associates the PLA particles with a liquid medium. The invention also discloses a preparation method of the PLA nano composite material, which comprises the following specific steps of A, mixing and stirring the nano material and the liquid medium to form a pasty nano material mixture; B. mixing and stirring the nano material mixture in the step A and PLA particles to form a blend; C. and C, melting and blending the blend obtained in the step B to obtain the PLA nanocomposite. The tensile strength and the impact strength of the nano composite material are improved on the basis of the PLA base material, and the nano composite material is simple in preparation method, low in production cost and easy to popularize.

Description

PLA (polylactic acid) nano composite material and preparation method thereof

Technical Field

The invention belongs to the field of nano composite materials and preparation thereof, and particularly relates to a PLA nano composite material and a preparation method thereof.

Background

Polylactic acid (PLA) has good thermal stability, the processing temperature is 170-230 ℃, and the PLA has good solvent resistance, and a product prepared from the PLA can be biodegraded, and has good biocompatibility, glossiness, transparency, hand feeling and heat resistance, so the PLA has wide application, can be used as a packaging material, a fiber, a non-woven fabric and the like, and is mainly used in the fields of clothing (underwear and outerwear), industry (building, agriculture, forestry and paper making), medical sanitation and the like. Although polylactic acid has been widely used, its inherent drawbacks and deficiencies limit its further applications. At this time, the special properties of the nano composite material different from those of the general composite material indicate a new way for the modification research of the polylactic acid. A large number of researches prove that the polylactic acid and the layered nano material are compounded to prepare the nano composite material, so that the comprehensive performance of the nano composite material can be obviously improved. At present, the preparation method of the PLA nanocomposite mainly adopts in-situ intercalation and melt intercalation methods. Because the in-situ intercalation industrial investment is large, the period is long, and the large-scale popularization and application are difficult; the melting intercalation can be carried out in common plastic mixing equipment, the processing is convenient, however, the lamellar nano-material needs to be organized and intercalated in the early stage, and the completely stripped polylactic acid nano-composite material is not easy to obtain. With the development of science and technology, engineering application puts higher requirements on the impact strength, bending strength and tensile strength of polylactic acid materials.

Patent No. CN101081928A proposes a method for preparing a nano composite material, which adopts a water-assisted method to prepare a polyamide/nano montmorillonite master batch, and the preparation method comprises the steps of using deionized water as an intercalation agent, mixing purified montmorillonite and deionized water, fully dispersing to prepare montmorillonite slurry, gradually adding the montmorillonite slurry into polyamide with completely melted components, and then extruding and granulating to obtain the polyamide/nano montmorillonite master batch. The preparation method is simple and low in production cost, but the montmorillonite slurry is added after the polyamide is melted, so that the montmorillonite slurry is not ready to be completely mixed with the copolymer, water between layers is gasified at high temperature, and the montmorillonite cannot be well dispersed into the polyamide, so that the product performance is improved to a limited extent; in addition, the montmorillonite slurry can be injected into the double screws only by increasing a certain pressure in the charging mode, and meanwhile, because the processing section of the double screws is short, the feeding interval of the montmorillonite slurry is increased midway, the length of the double screws needs to be increased, so that the process is more complicated and the cost is higher.

The present invention has been made in view of this situation.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a PLA nanocomposite material which has the advantages of simultaneously improved tensile strength and impact strength, simple preparation method, low production cost and easy popularization and a preparation method thereof.

In order to solve the above technical problems, the present invention provides a PLA nanocomposite, wherein the nanocomposite is prepared by melt-blending a mixture including PLA particles, and a nanomaterial that links the PLA particles and a liquid medium.

In the scheme, the PLA nanocomposite is prepared by feeding PLA particles, the nanomaterial and a liquid medium together. PLA particles are connected with each other through a nanometer material and a liquid medium to form a non-layered blend. The method well solves the problem that in the traditional method, PLA and the nano material are blended and can not be fed together when the nano material slips.

Further, the nano material is a layered nano material, and at least part of lamella of the layered nano material is dispersed in the PLA.

In the scheme, the layered nano material has a unique two-dimensional plate layer structure, the two-dimensional plate layers are arranged in an oriented and ordered manner to form a unique three-dimensional crystal structure, so that a liquid medium can be inserted into gaps between the layers to prop the plate layers open under a certain condition without damaging the original structure of the layered nano material, and the plate layer composition and the layer spacing of the layered nano material have adjustability. When the liquid medium enters the interlayer and the interlayer space is expanded due to the liquid medium, when the temperature is raised to or above the plasticizing temperature of the PLA, the liquid medium entering the interlayer of the layered nano material is further gasified and exploded, the generated huge energy peels off the lamellar layer of the layered material, and the peeled lamellar layer is orderly dispersed into the molten PLA under continuous stirring.

Preferably, the layered nano material comprises one or more of layered silicate, layered titanate, layered phosphate, layered metal hydroxide, transition metal oxyhalide, layered graphite, transition metal sulfide, layered metal oxide, layered metal nitride, layered metal carbide and two-dimensional metal organic framework;

more preferably, when the nano material is an ionic layered material, the XRD diffraction pattern of the nano composite material has no characteristic peak of interlayer spacing in the range of 2 theta angle to 10 degrees.

In the above scheme, the layered nanomaterial comprises an anionic layered nanomaterial, a cationic layered nanomaterial, and a nonionic layered nanomaterial, wherein: anionic nanomaterials include hydrotalcite like;

the cationic nano material comprises montmorillonite, inorganic phosphate, layered silicate, kaolin, sepiolite, titanate and the like;

the non-ionic nano material comprises:

(1) carbon material: graphene;

(2) graphene analogs: elements of the fourth main group of the periodic table, such as silylene, germylene, boracene, arsylene, etc., black phosphorus;

(3) transition Metal Sulfides (TMDs): transition Metal Sulfides (TMDs) may form insulators (HfS2), semiconductors (MoS2), semimetals (TiSe2), and all metals (NbSe2) based on the coordination environment and oxidation state of metal atoms, and Transition Metal Sulfides (TMDs) may exhibit superconductivity even under low temperature conditions. More than 40 lamellar transition metal sulfides are reported in the literature;

(4) layered metal oxide: MoO3, V2O3, V2O5, Al2O3, chromium oxide, TiO2, BiOCl, MnO 2;

(5) layered metal hydroxides, perovskite oxides;

(6) metal nitrides, carbides: h-BN, nitrogen carbide (g-C3N 4);

(7) two-dimensional metal-organic framework material: MOFs that have been stripped include: [ Cu2Br (IN)2] N (IN ═ isonicotinic acid), Zn-BDC (BDC ═ terephthalic acid), manganese-2, 2-dimethylsuccinic acid (MnDMS) bulk crystals were exfoliated IN ethanol, [ Zn2(bim)4] (bim ═ benzimidazole) IN a mixed solvent of methanol and propanol, MOF growth was controlled by diffusion IN a mixed solvent of N, N-dimethylformamide and acetonitrile to give ultrathin 2D CuBDC and ZnBDC MOF materials. M-TCPP ultrathin nanosheets (M ═ Zn, Cu, Cd, Co; TCPP ═ 5,10,15, 20-tetrakis (4-carboxyphenyl) porphine);

(8) transition metal oxyhalides: LiCoO2, FeOCl, etc.;

preferably montmorillonite, phyllosilicate, kaolin, graphene, hydrotalcite, and black phosphorus.

Further, the liquid medium enters the interlayer of the layered nano material to form a paste with certain consistency to connect the PLA particles; the consistency of the paste is 0-100 mm but not 0;

preferably, the mass part ratio of the liquid medium to the layered nano material is 3-100: 1; preferably 5-50: 1; more preferably 5 to 20: 1.

Compared with the process of modifying, filtering and drying the nano material by interlayer polymerization in the prior art, the process has the advantages that the continuous paste with certain self-adhesiveness is formed after the liquid medium is injected between the layers of the layered nano material, the paste has certain consistency but the consistency is not 0mm, and the paste represents that the paste is combined with the liquid medium, so that the nano material paste combined with the liquid medium can be uniformly adhered to the surface of PLA particles and is fed to a melting and blending device together with the PLA particles, and the processability is improved.

Further, the paste also contains an auxiliary agent, wherein the auxiliary agent comprises one or more of a carboxylate surfactant, a sulfate surfactant, a sulfonate surfactant, a phosphate surfactant, an amine salt surfactant, a quaternary ammonium salt surfactant, a heterocyclic surfactant, a nonionic surfactant, a natural water-soluble polymer, a synthetic water-soluble polymer and a prepolymer thereof; wherein, one or more of synthetic water-soluble macromolecule and prepolymer thereof are preferred;

preferably, the mass part ratio of the auxiliary agent to the nano material is 0.01-50: 1; preferably 0.1 to 5: 1; more preferably 0.2 to 1: 1.

In the scheme, the addition of the auxiliary agent can improve the capability of a liquid medium entering the nano material, so that the consistency of the nano material mixture is increased; in addition, the addition of the auxiliary agent can also increase the boiling point of the liquid medium and prevent the liquid medium from gasifying and escaping in advance. The reaction temperature for generating the paste-like nano material in the invention can be at room temperature, and the requirement on the auxiliary agent is not high, so that the auxiliary agent applicable to the invention has wider alternative range. The auxiliary agent comprises one or more of a surfactant, a water-soluble polymer and a prepolymer thereof, preferably the water-soluble polymer and the prepolymer thereof, more preferably polyaspartic acid, lecithin, sodium alginate, polyacrylic acid, polyvinylamine and hyaluronic acid;

wherein the surfactant comprises:

1. anionic surfactant: classified into carboxylates, sulfate ester salts, sulfonates, and phosphate ester salts.

(1) The soap is higher fatty acid salt, and the molecular structure general formula is (RCOO) -nMn +. Stearic acid, oleic acid, lauric acid and the like are commonly used. Depending on the metal ion (Mn +) thereof, there are alkali metal soaps, alkaline earth metal soaps, organic amine soaps and the like.

(2) The sulfated product is mainly sulfated oil and sulfate of higher fatty alcohol, and has molecular structure formula of ROSO3-M +, and commonly used sodium dodecyl sulfate (also known as "sodium lauryl sulfate"), sodium hexadecyl sulfate (also known as "sodium cetyl sulfate"), and sodium octadecyl sulfate (also known as "sodium stearyl sulfate").

(3) The sulfonic acid compound is mainly aliphatic sulfonic acid compound, sulfoaryl sulfonic acid compound, sulfonaphthalene sulfonic acid compound, etc

2. Cationic surfactant: the hydrophilic group ion of the cationic surfactant contains a nitrogen atom, and is classified into amine salts and heterocyclic types according to the position of the nitrogen atom in the molecule.

3. Zwitterionic surfactant: lecithin, amino acid type, betaine type

4. Nonionic surfactant: fatty glyceride, sorbitan fatty acid, polysorbate, alkylphenol polyoxyethylene, fatty alcohol polyoxyethylene, fatty acid methyl ester polyoxyethylene, and detergent.

The water-soluble polymer comprises

1. Natural polymer

Starches;

marine algae species: sodium alginate and agar;

vegetable gums: gum arabic, gum tragacanth, locust bean gum, tamarind seed polysaccharide gum, sesbania gum, carrageenan, guar gum, pectin;

animal glue: gelatin, casein, chitosan;

microbial glue: xanthan gum, gellan gum, hyaluronic acid.

2. Synthetic organic polymer

(1) Water-soluble polymer of polymerization type

Polyacrylamide, polyacrylic acid, polymethacrylic acid and copolymers thereof, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polymaleic anhydride, polydimethyldiallyl ammonium chloride, polyvinylamine, polydivinyl imidazoline, sodium polystyrene sulfonate, sulfonated styrene maleic anhydride copolymer and Kelvin resin;

(2) condensed water-soluble polymer

Water-soluble amino resin, water-soluble phenolic resin, water-soluble alkyd resin, water-soluble epoxy resin, water-soluble polyurethane resin, polyethyleneimine, polyaspartic acid, polyepoxysuccinic acid, polyamide epichlorohydrin resin, polyamide glyoxal resin, ammonia-epichlorohydrin resin, heavy polyamine epichlorohydrin resin, ammonia-dimethylamine-epichlorohydrin resin, N-dimethyl-1, 3-propanediamine and epichlorohydrin resin;

(3) others

Water-soluble maleic anhydride oil, dicyandiamide-formaldehyde resin, rosin amine-ethylene oxide polycondensate, poly N-vinyl acetamide and water-soluble polysucrose.

3. Semi-synthetic polymer

Modified cellulose and modified starch;

further, the liquid medium has a boiling point below the plasticizing temperature of PLA, preferably a boiling point below 180 ℃, more preferably water.

In the above scheme, the boiling point of the liquid medium needs to be lower than the plasticizing temperature of the PLA, and the liquid medium with the boiling point lower than 180 ℃ is preferred. The liquid medium is selected from: isopentane, n-pentane, petroleum ether, hexane, cyclohexane, isooctane, trifluoroacetic acid, trimethylpentane, cyclopentane, heptane, butyl chloride, trichloroethylene, carbon tetrachloride, trichlorotrifluoroethane, propyl ether, toluene, p-xylene, chlorobenzene, o-dichlorobenzene, diethyl ether, benzene, isobutanol, ethylene dichloride, n-butanol, butyl acetate, propanol, methyl isobutyl ketone, tetrahydrofuran, ethyl acetate, isopropanol, chloroform, methyl ethyl ketone, dioxane, pyridine, acetone, nitromethane, acetonitrile, dimethylformamide, methanol, water, methylamine, dimethylamine, diethyl ether, pentane, dichloromethane, carbon disulfide, 1, 1-dichloroethane, trifluoroacetic acid, 1, 1, 1-trichloroethane, ethanol, butanone, 1, 2-dichloroethane, ethylene glycol dimethyl ether, triethylamine, propionitrile, 4-methyl-2-pentanone, methyl alcohol, ethyl acetate, isopropyl alcohol, ethyl acetate, methyl ether, ethyl acetate, methyl ethyl ketone, ethyl acetate, dimethyl ether, dimethyl formamide, dimethyl, One or more of ethylenediamine, butanol, acetic acid, ethylene glycol monomethyl ether, octane, morpholine ethylene glycol monoethyl ether, xylene, m-xylene, acetic anhydride, o-xylene, N-dimethylformamide, cyclohexanone, cyclohexanol, furfural, N-methylformamide, and the like. Preferably, o-dichlorobenzene, water, trimethylpentane, isopentane, acetic acid, toluene; water is more preferable in view of manufacturing cost and pollution problem to the environment.

Further, the mass part ratio of the nano material to the PLA in the mixed material is 0.1-20: 100; preferably 1-10: 100, respectively; more preferably 3 to 5: 100.

Preferably, the mixture also comprises an anti-aging agent, and the mass part ratio of the anti-aging agent to the PLA is 0.1-1: 100; preferably 0.2-0.8: 100; more preferably 0.3 to 0.6: 100.

In the scheme, an anti-aging agent can be added in the step B to reduce the influence of the liquid medium on the performance of the nano composite material, wherein the mass part ratio of the anti-aging agent to the PLA is 0.1-1: 100; preferably 0.2-0.4: 100; more preferably 0.3 to 0.4: 100.

The anti-aging agent is selected from amine antioxidants, ketone amine condensate, diaryl secondary amine, substituted p-phenylenediamine and hindered amine;

phenolic antioxidants, which can be classified as alkylated monophenols, alkylated polyphenols, thiobisphenols and polyphenols. The main classes of alkylated monophenol and polyphenol antioxidants are antioxidants 264, 1076, 2246, 1035, 1010, 3114 and 1790. The main varieties of thiobisphenols are anti-aging agents 2246 and 300. The main varieties of the polyphenol antioxidant comprise 2, 5-di-tert-butyl hydrogen and 2, 5-di-tert-amyl hydroquinone;

antioxidant of thio dipropyl acetic acid and phosphorous acid vinegar, which is mainly composed of antioxidant TNP, Ultranox624 and tris (2, soul-di-tert-T phenyl) phosphite;

other types of antioxidants, 2-sulfobenzimide under the trade name antioxidant MB, nickel dibutyldithiocarbamate under the trade name antioxidant NBC, and also zinc dialkyldithiophosphate;

the main antioxidants are: one or more of antioxidant RD, antioxidant AW, antioxidant BLE, antioxidant A, antioxidant OD, 4 '-bis (alpha-methylbenzyl) diphenylamine, 4' -bis (alpha, alpha-methylbenzyl) diphenylamine, N, -di-sec-butyl p-phenylenediamine, antioxidant 4030, antioxidant 4010NA, antioxidant 4020, antioxidant 264, antioxidant 1076, antioxidant 2216, antioxidant 1035, antioxidant 1010, antioxidant 3114, antioxidant 1790, antioxidant 2246, 2, 5-di-tert-butylhydroquinone, antioxidant DLTP, antioxidant TNP, Ultranox624, tris (2, 4-di-tert-T-butylphenyl) phosphite, antioxidant MB, antioxidant NBC and zinc dialkyldithiophosphate; preferably, antioxidant RD, antioxidant AW, antioxidant 4010NA, antioxidant 3114 and antioxidant 264.

Further, the preparation method is characterized by comprising the following steps:

A. mixing and stirring the nano material and a liquid medium to form a pasty nano material mixture;

B. mixing and stirring the nano material mixture in the step A and PLA particles to form a blend;

C. and C, melting and blending the blend obtained in the step B to obtain the PLA nanocomposite.

According to the scheme, the liquid medium enters the nano material, the pasty nano material with certain self-adhesiveness is prepared under the condition of full stirring, the pasty nano material and the PLA are uniformly mixed and can be directly added into a feeding area without applying pressure or feeding midway, the process is saved, and the cost is reduced. In addition, the nano material and the PLA are mixed and then added, and then the melting and blending are carried out, the melted PLA can coat the nano material to form a protective layer, when a liquid medium entering the nano material is gasified, and the vapor pressure in the nano material is greater than the melt pressure of the PLA, huge internal violence can be generated to separate the nano material, and the separated nano material is uniformly dispersed into the PLA.

In the above scheme, latex may be further added to coat the pasty nanomaterial mixture obtained in step a, the latex including: the emulsion comprises one or more of styrene-acrylic emulsion, acrylate emulsion, acrylic emulsion, silicone-acrylic emulsion, aqueous polyurethane emulsion, fluorocarbon emulsion, rosin resin emulsion, terpineol, vinyl acetate-acrylic emulsion, aqueous epoxy resin emulsion, styrene-butadiene latex, natural latex, white latex, neoprene latex, pure acrylic latex, carboxylic styrene-butadiene latex and styrene-acrylic latex, and one or more of styrene-acrylic emulsion, silicone-acrylic emulsion, vinyl acetate-acrylic emulsion and styrene-acrylic latex is preferred.

In the scheme, the latex is added to coat the nano material mixture to form a protective layer, when the nano material mixture and the PLA are melted and blended, the liquid medium entering the nano material is gasified, when the vapor pressure in the protective layer is greater than the melt pressure of the PLA, the internal explosion force is generated to separate the agglomerated nano material, and the separated nano material can be highly dispersed in the melted PLA through continuous stirring and/or shearing.

In the above scheme, the melt extrusion process in step C may be banburying, roll mixing, screw (parallel/conical/single/double/triple screw).

In the scheme, when the double-screw extruder is adopted, the problems that the nano material and the PLA are slipped and cannot be fed simultaneously are well solved, the mixed feeding of the PLA and the nano material in the presence of a liquid medium is realized, pressure is not required to be applied during feeding, and in addition, the nano material can be dispersed in the PLA seed more fully through the shearing force of the double-screw extruder and the internal explosion force generated by gasification of the liquid medium in the melting process of the PLA and the nano material.

Wherein the rotating speed of a main machine of the double-screw extruder is 30-80Hz, the rotating speed of a main feeding hopper is 10-30Hz, the extrusion temperature is 150-; preferably, the rotation speed of the host is 60-80Hz, the rotation speed of the main feeding hopper is 20-30Hz, the extrusion temperature is 150-180 ℃ in the first zone, 245-260 ℃ in the second zone, 245-260 ℃ in the third zone, 245-260 ℃ in the fourth zone and 245-260 ℃ in the fifth zone.

Further, an auxiliary agent is added in the step A, and the auxiliary agent can be added at one time or added in batches;

preferably, physical means can be added in the step A to promote the dispersion of the liquid medium among the nano materials, and the physical means comprises colloid milling, ball milling, ultrasound, vortex, etching assistance and airflow impact.

In the scheme, the addition of the auxiliary agent can improve the capability of a liquid medium entering the nano material, so that the consistency of the nano material mixture is increased; in addition, the addition of the auxiliary agent can also increase the boiling point of the liquid medium and prevent the liquid medium from gasifying and escaping in advance.

In the scheme, the dispersion of the liquid medium in the nano material can be promoted by means of a physical mode, wherein the physical mode comprises but is not limited to ultrasonic mode, colloid mill mode, ball milling mode, vortex mode, etching auxiliary mode, airflow impact mode and the like, the ultrasonic frequency is 800-1000 Hz, and the power is 200-1000W.

Further, in the step C, when the temperature is equal to or higher than the PLA plasticizing temperature, the liquid medium in the nano mixed material is gasified, and the gasification separates the agglomerated nano material;

preferably, when the nano material is a layered nano material, the liquid medium enters the interlayer of the layered nano material in the step A to form a paste with self-adhesion, and the liquid medium entering the interlayer is gasified when the temperature is equal to or higher than the plasticizing temperature of PLA in the step C to separate the lamellar nano material.

In the above scheme, when the temperature rises to or above the plasticizing temperature of the PLA, the liquid medium entering the nanomaterial is further gasified, the gasification generates huge energy and separates the agglomerated nanomaterial, and the separated nanomaterial is uniformly dispersed into the molten PLA with continuous stirring.

In the scheme, the layered nano material has a unique two-dimensional plate layer structure, the two-dimensional plate layers are arranged in an oriented and ordered manner to form a unique three-dimensional crystal structure, so that a liquid medium can be inserted into gaps between the layers to prop the plate layers open under a certain condition without damaging the original structure of the layered nano material, and the plate layer composition and the layer spacing of the layered nano material have adjustability. The layered material is selected from one or more of a cationic layered material, an anionic layered material and a non-ionic layered material.

In the scheme, when the nano material is a layered nano material, the liquid medium enters the layers of the nano material and is continuously stirred to form a paste nano material mixture, and when the PLA and the nano material mixture are melted and blended, the PLA is softened in the temperature rising process to coat the layered nano material to form a protective layer, so that the liquid medium is prevented from being gasified and escaping too early. As the temperature rises, the liquid medium that does not enter the layers vaporizes when the boiling point of the liquid medium is reached, and the vaporization causes bubbling in the blend to achieve further agitation. When the temperature rises to or above the plasticizing temperature of the PLA, the liquid medium entering the interlayer of the layered nano material is further gasified and exploded, the generated huge energy peels off the lamellar layer of the layered material, and the peeled lamellar layer is orderly dispersed into the molten PLA under continuous stirring.

The invention also provides a mixed material, which comprises: paste and PLA;

the paste comprises: 1 part of nano material, 5-100 parts of liquid medium and 0-50 parts of auxiliary agent by weight but not 0; the paste is adhered to the surface of PLA particles to form a mixed material;

preferably, the nanomaterial and the adjuvant are added to the liquid medium and dispersed in sequence during the preparation of the paste.

In the above scheme, a self-adhesive paste is prepared by mixing the nano material, the liquid medium and a proper amount of the auxiliary agent, the paste adheres to the PLA particles when the PLA base material is mixed with the paste, and the PLA particles adhere to each other through the paste. The nano material, the liquid medium and the PLA particles well solve the problem that the raw materials cannot be fed together due to slipping in the prior art.

After adopting the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. the process is simple, the nano material and the liquid medium are mixed to form paste and PLA to be melted and blended together, so that the nano composite material can be obtained, and the nano material does not need to be subjected to complex organic treatment;

2. in the feeding mode, the invention realizes the simultaneous feeding of the nano material and the PLA in the presence of the liquid medium, saves the problem that the screw length needs to be increased during the feeding of the nano material, has lower production cost and easy popularization, and can reduce the environmental pollution particularly by taking water as the liquid medium.

3. The nanometer material and the PLA are melted and mixed together, so that the nanometer material can be better dispersed into the PLA, and the impact strength and the tensile strength of the nanometer composite material prepared by the method are simultaneously improved.

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Drawings

FIG. 1 is an SEM image of graphene in a paste according to the present invention;

FIG. 2 is a TEM image of graphene in paste of the present invention;

FIG. 3 is a graph of the SRD of a PLA phyllosilicate nanocomposite;

FIG. 4 is an XRD pattern of an undispersed layered silicate.

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 will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and the following embodiments are used for illustrating the present invention and are not intended to limit the scope of the present invention.

Example 1

PLA/graphene nanocomposite

Raw materials: 100 parts of PLA, 40 parts of water, 10 parts of graphene and 1 part of open-chain adhesive

The preparation method comprises the following steps:

1. stirring the water in parts by weight under the ultrasonic condition of 1000HZ and 200W, slowly adding graphene powder, performing ultrasonic treatment for 30min, then adding gelatin, and continuing performing ultrasonic treatment for 60min to finally form a paste-shaped graphene mixed material, wherein the consistency of the mixed material is 51 mm;

2. mixing and uniformly stirring PLA and the paste graphene mixed material, and putting the mixture into a feed inlet of a double-screw extruder;

3. and further melting and mixing the PLA and the graphene, and performing extrusion granulation and drying to obtain the PLA graphene nano composite material.

The rotating speed of a main machine of the extrusion equipment is 30Hz, the rotating speed of a main feeding hopper is 10Hz, the extrusion temperature is 150 ℃ in a first area, 220 ℃ in a second area, 230 ℃ in a third area, 220 ℃ in a fourth area, 230 ℃ in a fifth area, and the linear speed of the rotating speed of the screw is 0.8 m/s.

Example 2

PLA/vanadium pentoxide nanocomposite

Raw materials: 100 parts of PLA, 100 parts of water, 20 parts of vanadium pentoxide and 0.2 part of water-soluble epoxy resin, and 0.2 part of antioxidant RD

1. Stirring the water in parts by weight under the ultrasonic condition of 1000HZ and 1000W, slowly adding vanadium pentoxide powder, performing ultrasonic treatment for 30min, then adding water-soluble epoxy resin, and continuing performing ultrasonic treatment for 60min to obtain a pasty vanadium pentoxide mixed material, wherein the consistency of the mixed material is 71 mm;

2. mixing and stirring PLA and the paste vanadium pentoxide mixed material uniformly, and putting the mixture into a feed inlet of a double-screw extruder;

3. and further melting and mixing the PLA and the vanadium pentoxide, and performing extrusion granulation and drying to obtain the PLA/vanadium pentoxide nanocomposite.

The rotating speed of a main machine of the extrusion equipment is 80Hz, the rotating speed of a main feeding hopper is 30Hz, the extrusion temperature in a first zone is 160 ℃, a second zone is 230 ℃, a third zone is 230 ℃, a fourth zone is 240 ℃ and a fifth zone is 230 ℃; the linear speed of the screw speed was 1 m/s.

Example 3

PLA/montmorillonite nano composite material

Raw materials: 100 parts of PLA, 100 parts of trimethylpentane, 0.5 part of montmorillonite, 2.5 parts of lecithin, 0.3 part of anti-aging agent AW

The preparation method comprises the following steps:

1. stirring trimethylpentane in parts by weight under the ultrasonic condition of 800HZ and 1000W, slowly adding montmorillonite powder into trimethylpentane, adding lecithin after ultrasonic treatment for 30min, and continuing ultrasonic treatment for 60min to obtain a paste montmorillonite mixed material, wherein the consistency of the mixed material is 62 mm;

2. mixing PLA, the paste montmorillonite mixed material and the anti-aging agent RD uniformly, and adding into an internal mixer;

3. further melting and blending PLA and montmorillonite in an internal mixer at 300 ℃, internally mixing and compounding for 3 hours, and granulating and drying to obtain the PLA/montmorillonite nanocomposite.

Example 4

PLA/kaolin nanocomposite

Raw materials: 100 parts of PLA, 30 parts of water, 3 parts of kaolin, 12 parts of sodium alginate and 31140.4 parts of antioxidant

The preparation method comprises the following steps:

1. slowly stirring the water in parts by weight, adding kaolin powder, adding sodium alginate, and fully stirring to form a paste-shaped kaolin mixed material, wherein the consistency of the mixed material is 77 mm;

2. mixing and stirring PLA and kaolin mixed material and an antioxidant 3114 uniformly, and adding the mixture into a feeding area of a double-screw extruder;

3. and further melting and mixing the PLA and the kaolin, and performing extrusion granulation and drying to obtain the PLA/kaolin nano composite material.

The rotating speed of a main machine of the extrusion equipment is 60Hz, the rotating speed of a main feeding hopper is 25Hz, the extrusion temperature in a first zone is 170 ℃, a second zone is 240 ℃, a third zone is 240 ℃, a fourth zone is 230 ℃ and a fifth zone is 230 ℃; the linear speed of the screw speed was 0.8 m/s.

Example 5

PLA/phyllosilicate nanocomposite

Raw materials: 100 parts of PLA, 25 parts of toluene, 5 parts of phyllosilicate, 1 part of polyacrylic acid and 22460.5 parts of anti-aging agent

1. Adding the layered silicate powder into the toluene in parts by weight under slow stirring, adding polyacrylic acid, and fully stirring to form a paste-like layered silicate mixed material, wherein the consistency of the mixed material is 19 mm;

2. mixing PLA, a layered silicate mixed material and an antioxidant 2246 uniformly, and adding into an internal mixer;

3. further melting and blending PLA and phyllosilicate in an internal mixer at 300 ℃, internally mixing and compounding for 3h, discharging, and then granulating and drying to obtain the PLA/phyllosilicate nano composite material.

Example 6

PLA/black phosphorus nanocomposite

Raw materials: 100 parts of PLA, 20 parts of water, 0.1 part of black phosphorus, 1 part of polyvinylamine and 0.6 part of anti-aging agent MB

The preparation method comprises the following steps:

1. stirring the water in parts by weight under the ultrasonic condition of 1000HZ and 500W, slowly adding black phosphorus powder, performing ultrasonic treatment for 30min, then adding polyvinylamine, and continuing performing ultrasonic treatment for 60min to finally form a pasty black phosphorus mixed material, wherein the consistency of the mixed material is 41 mm;

2. mixing PLA, a black phosphorus mixed material and an anti-aging agent MB, uniformly stirring, and adding into a feed inlet of a double-screw extruder;

3. further melting and blending PLA and black phosphorus, extruding, granulating and drying to obtain the PLA/black phosphorus nano composite material.

The rotating speed of a main machine of the extrusion equipment is 60Hz, the rotating speed of a main feeding hopper is 20Hz, the extrusion temperature in a first zone is 180 ℃, a second zone is 230 ℃, a third zone is 230 ℃, a fourth zone is 230 ℃ and a fifth zone is 220 ℃; the linear speed of the screw speed was 0.9 m/s.

Example 7

PLA/montmorillonite/sepiolite nanocomposite

Raw materials: 100 parts of PLA, 16 parts of acetic acid, 2 parts of montmorillonite/sepiolite, 0.6 part of hyaluronic acid, 0.7 part of anti-aging agent 4010NA

Wherein the mass ratio of the montmorillonite to the sepiolite is 1: 1.

The preparation method comprises the following steps:

1. slowly stirring the acetic acid in parts by weight, adding montmorillonite/sepiolite powder, adding hyaluronic acid, and fully stirring to form a paste montmorillonite/sepiolite nano mixed material, wherein the consistency of the mixed material is 9 mm;

2. mixing PLA, montmorillonite/sepiolite nano mixed material and anti-aging agent 4010NA, uniformly stirring, and adding into a feed inlet of a double-screw extruder;

3. further melting and blending PLA and montmorillonite/sepiolite, extruding, granulating and drying to obtain the PLA/montmorillonite/sepiolite nanocomposite.

The rotating speed of a main machine of the extrusion equipment is 70Hz, the rotating speed of a main feeding hopper is 15Hz, the extrusion temperature in a first zone is 170 ℃, a second zone is 200 ℃, a third zone is 200 ℃, a fourth zone is 220 ℃ and a fifth zone is 200 ℃; the linear speed of the screw speed was 1 m/s.

Example 8

PLA montmorillonite/black phosphorus nano composite material

Raw materials: 100 parts of PLA (polylactic acid), 80 parts of toluene, 8 parts of montmorillonite/black phosphorus, 4 parts of lecithin/sodium alginate and 0.8 part of anti-aging agent NBC

Wherein the mass ratio of the montmorillonite to the black phosphorus is 1:1, the mass ratio of the water to the toluene is 1:1, and the mass ratio of the lecithin to the sodium alginate is 1: 1.

The preparation method comprises the following steps:

1. stirring the water and the toluene in parts by weight under the ultrasonic condition of 800HZ and 500W, slowly adding montmorillonite and black phosphorus powder, carrying out ultrasonic treatment for 30min, then adding lecithin and sodium alginate, and carrying out continuous ultrasonic treatment for 60min to finally form a paste montmorillonite/black phosphorus mixed material, wherein the consistency of the mixed material is 19 mm;

2. mixing PLA, montmorillonite/black phosphorus mixed material and an anti-aging agent NBC, uniformly stirring, and adding into a feed inlet of a double-screw extruder;

3. further melting and blending PLA and montmorillonite/black phosphorus, extruding, granulating and drying to obtain the PLA/montmorillonite/black phosphorus composite material.

The rotating speed of a main machine of the extrusion equipment is 30Hz, the rotating speed of a main feeding hopper is 30Hz, the extrusion temperature in a first zone is 165 ℃, a second zone is 250 ℃, a third zone is 250 ℃, a fourth zone is 250 ℃ and a fifth zone is 250 ℃; the linear speed of the screw speed was 1 m/s.

Example 9

PLA/graphene/vanadium pentoxide nanocomposite

Raw materials: 100 parts of PLA (polylactic acid), 75 parts of toluene/acetic acid, 15 parts of graphene/vanadium pentoxide and 6 parts of dicyandiamide-formaldehyde resin/6 parts of polyvinylamine antioxidant 1035/1 part of anti-aging agent NBC (N-butyl rubber)

Wherein the mass ratio of the toluene to the acetic acid is 1:1, the mass ratio of the graphene to the vanadium pentoxide is 1:1, the mass ratio of the dicyandiamide-formaldehyde resin to the polyvinylamine is 1:1, and the mass ratio of the antioxidant 1035 to the antioxidant NBC is 1: 1.

The preparation method comprises the following steps:

1. stirring the toluene and the acetic acid in parts by weight under the ultrasonic condition of 800HZ and 800W, slowly adding graphene and vanadium pentoxide powder, performing ultrasonic treatment for 30min, then adding dicyandiamide-formaldehyde resin and polyvinylamine, and continuing performing ultrasonic treatment for 60min to finally form a paste graphene/vanadium pentoxide mixed material, wherein the consistency of the mixed material is 79 mm;

2. mixing PLA and a graphene/vanadium pentoxide mixed material, an antioxidant 1035 and an anti-aging agent NBC, uniformly stirring, and adding into a feed inlet of a double-screw extruder;

3. and further melting and blending the PLA and the graphene/vanadium pentoxide, and performing extrusion granulation and drying to obtain the PLA/graphene/vanadium pentoxide nanocomposite.

The rotating speed of a main machine of the extrusion equipment is 30Hz, the rotating speed of a main feeding hopper is 30Hz, the extrusion temperature in a first zone is 165 ℃, a second zone is 235 ℃, a third zone is 235 ℃, a fourth zone is 200 ℃ and a fifth zone is 200 ℃; the linear speed of the screw speed was 1 m/s.

Comparative example 1

The PLA/graphene nano composite material is prepared by intercalation polymerization

Raw materials: 100 parts of PLA, 10 parts of water, 0.1 part of graphene, 0.5 part of hexadecyl quaternary ammonium salt and 20.5 parts of catalyst SnCl20

The preparation method comprises the following steps:

1. mixing the graphene and water in parts by weight, placing the mixture in a super constant-temperature water bath at 80 ℃, stirring the mixture at a high speed for 30min, standing the mixture for 2h, adding hexadecyl quaternary ammonium salt into a graphene aqueous solution, stirring the mixture for 2h at 80 ℃, and carrying out suction filtration and drying on a reaction solution to obtain organic graphene;

2. mixing organic graphene and PLA, adding a catalyst SnCl2, putting into a double-screw extruder for melting, mixing, extruding, granulating and drying to obtain the PLA/graphene nanocomposite.

Wherein the process parameters of the twin-screw extruder are the same as in example 1.

Comparative example 2

In the comparative example, on the basis of example 1, the position of graphene added into the extruder is adjusted, and the PLA/graphene nanocomposite material is prepared by a water-assisted method.

Raw materials: PLA 100 parts of water 10 parts of graphene 0.1 part

The preparation method comprises the following steps:

1. mixing the water and the graphene in parts by weight, and fully dispersing to obtain graphene slurry;

2. putting PLA into a feed inlet of a double-screw extruder, and melting the PLA at high temperature;

3. and putting the graphene slurry into the PLA which is completely melted, and extruding, granulating and drying to obtain the PLA/graphene nano composite material.

Wherein the process parameters of the twin-screw extruder are the same as in example 1.

Experimental example 1

In this example, the properties of the nanocomposites obtained in examples 1-10 were compared with those of the corresponding binders, as shown in Table 1.

Table 1:

categories	Tensile Strength (MPa)	Impact Strength (kg. cm/cm)
			Example 1	70	34
Example 2	72	37
			Example 3	75	36
Example 4	73	34
			Example 5	74	35
Example 6	75	36
			Example 7	71	37
Example 8	74	36
			Example 9	75	34
PLA base material	65	30

From the above experimental results, it can be seen that the impact strength and tensile strength of examples 1-9 are greatly improved compared to the PLA base material. The PLA base material and the nano material are fed together in the presence of the liquid medium, the PLA and the nano material are mutually permeated and coated in the PLA melting process, and the nano material is separated and orderly dispersed in the melted PLA by the gasification of the liquid medium, so that the overall performance of the PLA is improved.

Experimental example 2

This experimental example was used to compare the differences in nanomaterial content and properties between PLA/graphene nanocomposites prepared by different methods of example 1, comparative example 1, and comparative example 2 and PLA monomers, as shown in table 2.

Table 2:

performance parameter	PLA monomer	Example 1	Comparative example 1	Comparative example 2
					Content of the nano material%	0	2.2	1.7	1.8
Tensile strength MPa	65	70	68	66
					Bending strength MPa	78	90	81	80
Impact strength Kg cm/cm	30	34	26	28

From the above data, it can be seen that the nanomaterial content in the PLA/graphene nanocomposite prepared by the method of example 1 is higher than that in comparative examples 1 and 2, indicating that graphene can be sufficiently exfoliated and well dispersed in PLA by this method. In addition, the tensile strength, the bending strength and the impact strength of the product prepared in example 1 are all better than those of the PLA monomer, while the impact strength of the products prepared in comparative examples 1 and 2 is reduced though the tensile strength is improved, which further illustrates that the nano material sheets can be highly dispersed in the PLA by the method of example 1, and further, the tensile strength and the impact strength can be improved.

Experimental example 3

1. By testing the SEM image (shown in figure 1) of the graphene in the paste, the sample is seen to be in a relatively transparent state, which indicates that the graphene sheet layer is relatively thin and the agglomeration phenomenon is not obvious;

2. by testing a TEM image (as shown in fig. 2) of graphene in the paste, it can be seen that the sample sheet layer is very thin, and can be regarded as being formed by stacking peeled single-sheet graphene layers, the surface wrinkle of the sample is due to the fact that the material of the two-dimensional structure is not stable and exists alone, and the wrinkle is beneficial to stabilizing graphene, and further, the obtained sample is proved to be single-layer or few-layer graphene.

3. By testing the SRD pattern of the PLA phyllosilicate nanocomposite (as shown in fig. 3), it can be seen from the test results that the interlayer spacing peak of the phyllosilicate is not present between 2 and 10 degrees, while the XRD pattern of the undispersed phyllosilicate (as shown in fig. 4) can see a very distinct interlayer spacing peak, demonstrating that the lamellae of the phyllosilicate in the composite are opened.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (22)

1. A PLA nanocomposite, characterized in that the nanocomposite is made by melt blending a blend comprising PLA particles, and a nanomaterial linking the PLA particles and a liquid medium; the nano material is a layered nano material, and at least part of lamella of the layered nano material is dispersed into PLA;

the nano composite material is prepared by the following method:

A. mixing and stirring the nano material and a liquid medium to form a pasty nano material mixture;

B. mixing and stirring the nano material mixture in the step A and PLA particles to form a blend;

C. melting and blending the blend obtained in the step B to obtain the PLA nanocomposite;

and the liquid medium is water, the boiling point of the liquid medium is lower than the plasticizing temperature of the PLA, and when the temperature of the melt blending step in the step C is increased to be higher than or equal to the plasticizing temperature of the PLA, the vapor pressure in the nano material is higher than the melt pressure of the PLA, so that the liquid medium is gasified, and the agglomerated nano material is separated.

2. A PLA nanocomposite as claimed in claim 1 wherein the layered nanomaterial comprises one or more of layered silicates, layered titanates, layered phosphates, layered metal hydroxides, transition metal oxyhalides, layered graphites, transition metal sulfides, layered metal oxides, layered metal nitrides, layered metal carbides, two-dimensional metal organic frameworks.

3. A PLA nanocomposite as claimed in claim 2 wherein, when the nanomaterial is an ionic layered material, the nanocomposite XRD diffractogram has no characteristic peak of interlayer spacing in the range of 2-10 ° at 2 θ angle.

4. A PLA nanocomposite as claimed in claim 1, wherein the liquid medium enters between the layers of the layered nanomaterial to form a paste with a consistency that links the PLA particles; the paste has a consistency of 0-100 mm but not 0.

5. The PLA nanocomposite material as claimed in claim 4, wherein the ratio of the liquid medium to the layered nanomaterial is 3-100: 1 by mass.

6. The PLA nanocomposite as claimed in claim 5, wherein the ratio of the liquid medium to the layered nanomaterial is 5-50 parts by mass: 1.

7. the PLA nanocomposite material as claimed in claim 6, wherein the mass part ratio of the liquid medium to the layered nanomaterial is 5-20: 1.

8. A PLA nanocomposite as claimed in claim 4 wherein the paste further comprises adjuvants including one or more of carboxylate surfactants, sulfate ester surfactants, sulfonate surfactants, phosphate ester surfactants, amine salt surfactants, quaternary ammonium surfactants, heterocyclic surfactants, nonionic surfactants, natural water-soluble polymers, synthetic water-soluble polymers and prepolymers thereof.

9. A PLA nanocomposite as claimed in claim 8 wherein the adjuvant comprises one or more of synthetic water soluble polymers and prepolymers thereof.

10. The PLA nanocomposite as claimed in claim 8, wherein the mass part ratio of the auxiliary to the nanomaterial is 0.01-50: 1.

11. The PLA nanocomposite as claimed in claim 10, wherein the mass part ratio of the auxiliary to the nanomaterial is 0.1-5: 1.

12. the PLA nanocomposite as claimed in claim 11, wherein the mass part ratio of the auxiliary to the nanomaterial is 0.2-1: 1.

13. The PLA nanocomposite material as claimed in claim 1, wherein the mass part ratio of the nanomaterial to the PLA in the mixed material is 0.1-20: 100.

14. The PLA nanocomposite as claimed in claim 13, wherein the ratio of the nanomaterial to the PLA in the mixture is 1-10 parts by mass: 100.

15. the PLA nanocomposite as claimed in claim 14, wherein the mass part ratio of the nanomaterial to the PLA in the mixed material is 3-5: 100.

16. The PLA nanocomposite as claimed in claim 13, wherein an anti-aging agent is further included in the mixture, and the mass part ratio of the anti-aging agent to the PLA is 0.1-1: 100.

17. The PLA nanocomposite as claimed in claim 16, wherein the mass part ratio of the antiaging agent to the PLA is 0.2-0.8: 100.

18. The PLA nanocomposite as claimed in claim 17, wherein the mass part ratio of the antiaging agent to the PLA is 0.3-0.6: 100.

19. A method for preparing a PLA nanocomposite as claimed in any one of claims 1 to 18, comprising the steps of:

A. mixing and stirring the nano material and a liquid medium to form a pasty nano material mixture;

B. mixing and stirring the nano material mixture in the step A and PLA particles to form a blend;

C. melting and blending the blend obtained in the step B to obtain the PLA nanocomposite;

and the liquid medium is water, the boiling point of the liquid medium is lower than the plasticizing temperature of the PLA, and when the temperature of the melt blending step in the step C is increased to be higher than or equal to the plasticizing temperature of the PLA, the vapor pressure in the nano material is higher than the melt pressure of the PLA, so that the liquid medium is gasified, and the agglomerated nano material is separated.

20. The method for preparing a PLA nanocomposite, as claimed in claim 19, wherein an auxiliary agent is further added in step A, and the auxiliary agent can be added in a single step or in multiple steps.

21. The method for preparing a PLA nanocomposite as claimed in claim 19, wherein physical means including colloid milling, ball milling, ultrasound, vortex, etching aid, and air impingement are added in step A to promote dispersion of the liquid medium between the nanomaterials.

22. The method as claimed in claim 19, wherein when the nanomaterial is a layered nanomaterial, the liquid medium enters between layers of the layered nanomaterial to form a self-adhesive paste in step a, and the liquid medium entering between layers is gasified at a temperature equal to or higher than the PLA plasticizing temperature to separate the layers of the layered nanomaterial.

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