CN107881786B - Preparation method of nano montmorillonite/melamine formaldehyde resin modified chopped coconut fiber - Google Patents
Preparation method of nano montmorillonite/melamine formaldehyde resin modified chopped coconut fiber Download PDFInfo
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- 239000000835 fiber Substances 0.000 title claims abstract description 148
- 235000013162 Cocos nucifera Nutrition 0.000 title claims abstract description 102
- 244000060011 Cocos nucifera Species 0.000 title claims abstract description 102
- 229910052901 montmorillonite Inorganic materials 0.000 title claims abstract description 29
- 229920000877 Melamine resin Polymers 0.000 title claims abstract description 23
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 title claims abstract description 18
- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000000725 suspension Substances 0.000 claims abstract description 23
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000006087 Silane Coupling Agent Substances 0.000 claims abstract description 14
- 239000004312 hexamethylene tetramine Substances 0.000 claims abstract description 12
- 235000010299 hexamethylene tetramine Nutrition 0.000 claims abstract description 12
- 239000008098 formaldehyde solution Substances 0.000 claims abstract description 11
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims abstract description 11
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 238000001035 drying Methods 0.000 claims abstract description 8
- 238000001914 filtration Methods 0.000 claims abstract description 8
- 239000000243 solution Substances 0.000 claims description 42
- 238000003756 stirring Methods 0.000 claims description 23
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 239000012153 distilled water Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 16
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims description 9
- 238000007664 blowing Methods 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- 239000011259 mixed solution Substances 0.000 claims description 6
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 2
- 239000002131 composite material Substances 0.000 abstract description 33
- 239000004743 Polypropylene Substances 0.000 abstract description 17
- 229920001155 polypropylene Polymers 0.000 abstract description 17
- -1 polypropylene Polymers 0.000 abstract description 16
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 abstract description 10
- 239000003063 flame retardant Substances 0.000 abstract description 10
- 238000012360 testing method Methods 0.000 abstract description 8
- 238000000354 decomposition reaction Methods 0.000 description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- 238000001514 detection method Methods 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 5
- 229920001911 maleic anhydride grafted polypropylene Polymers 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000005979 thermal decomposition reaction Methods 0.000 description 5
- 238000002411 thermogravimetry Methods 0.000 description 5
- 229920001587 Wood-plastic composite Polymers 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000002861 polymer material Substances 0.000 description 4
- 239000011155 wood-plastic composite Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000013329 compounding Methods 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 229920002488 Hemicellulose Polymers 0.000 description 2
- 229920002678 cellulose Polymers 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 229920005610 lignin Polymers 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229920002994 synthetic fiber Polymers 0.000 description 2
- 239000012209 synthetic fiber Substances 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- IVJISJACKSSFGE-UHFFFAOYSA-N formaldehyde;1,3,5-triazine-2,4,6-triamine Chemical compound O=C.NC1=NC(N)=NC(N)=N1 IVJISJACKSSFGE-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M15/00—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment
- D06M15/19—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment with synthetic macromolecular compounds
- D06M15/37—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
- D06M15/39—Aldehyde resins; Ketone resins; Polyacetals
- D06M15/423—Amino-aldehyde resins
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- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M11/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising
- D06M11/77—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with silicon or compounds thereof
- D06M11/79—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with silicon or compounds thereof with silicon dioxide, silicic acids or their salts
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- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M13/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment
- D06M13/50—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment with organometallic compounds; with organic compounds containing boron, silicon, selenium or tellurium atoms
- D06M13/51—Compounds with at least one carbon-metal or carbon-boron, carbon-silicon, carbon-selenium, or carbon-tellurium bond
- D06M13/513—Compounds with at least one carbon-metal or carbon-boron, carbon-silicon, carbon-selenium, or carbon-tellurium bond with at least one carbon-silicon bond
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- D06M15/00—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment
- D06M15/19—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment with synthetic macromolecular compounds
- D06M15/21—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D06M15/327—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds of unsaturated alcohols or esters thereof
- D06M15/333—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds of unsaturated alcohols or esters thereof of vinyl acetate; Polyvinylalcohol
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- D06M2101/00—Chemical constitution of the fibres, threads, yarns, fabrics or fibrous goods made from such materials, to be treated
- D06M2101/02—Natural fibres, other than mineral fibres
- D06M2101/04—Vegetal fibres
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- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
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Abstract
The invention discloses a preparation method of nano montmorillonite/melamine formaldehyde resin modified chopped coconut fiber. Firstly, mixing A with B, filtering and drying to obtain modified chopped coconut shell fiber, wherein the modified chopped coconut shell fiber is prepared from a formaldehyde solution, a solution A prepared from hexamethylenetetramine and melamine, a PVA solution, nano montmorillonite, a silane coupling agent KH-792 and a suspension B prepared from chopped coconut shell fiber. According to the invention, the modified chopped coconut fiber and polypropylene are mixed to prepare the composite material for testing, and the product obtained through the test has good mechanical property, tribological property and flame retardant grade.
Description
Technical Field
The invention belongs to the technical field of natural fiber modification, and relates to a preparation method of nano montmorillonite/melamine formaldehyde modified chopped coconut shell fiber.
Background
Compared with a large amount of synthetic fibers sold on the market at present, the coconut shell fiber has strong toughness, degradability and small pressure on the ecological environment, and is expected to replace the synthetic fibers to be used as a reinforcing base of a composite material. The commercialized coconut fiber contains 46-63% of cellulose, 31-36% of lignin, 0.15-0.25% of hemicellulose, and also contains mineral substances and the like. The microstructure of the fiber can be regarded as that cellulose with higher crystalline content forms a main tubular structure, hemicellulose forms an intertube spiral structure, and lignin is filled in a gap between the tubular structure and the spiral structure to realize reinforcement. The natural reinforcing mechanism enables the coconut shell fiber to have excellent mechanical properties in natural fibers, however, in practical application, the mechanical advantages of the coconut shell fiber are not fully improved, mainly because the compatibility of the fiber and a wood-plastic composite material prepared by compounding the high polymer material is poor, the interface of the prepared composite material is weak, and the mechanical properties and the tribological properties of the composite material are poor. In addition, the coconut fiber is flammable, and the flame retardant property of the wood-plastic composite material prepared by compounding the coconut fiber with high polymer is poor.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides a preparation method of nano montmorillonite/melamine formaldehyde resin modified chopped coconut shell fiber, so that the groups and heat resistance on the surface of the modified fiber are changed, the interface bonding capability with a high polymer material is enhanced, and the prepared composite material has good mechanical property and wear resistance; a large amount of nitrogen elements generated on the surface of the fiber through chemical reaction can effectively promote the improvement of the flame retardant property of the composite material. The invention adopts nano montmorillonite and melamine formaldehyde resin to jointly modify the chopped coconut shell fiber by a three-step method, improves the wear resistance and the flame retardant property of the coconut shell fiber by melamine, and realizes the interface enhancement after the compounding with a high polymer material by the lamellar structure of the nano montmorillonite.
The technical scheme adopted by the invention for solving the technical problem comprises the following steps:
the method comprises the following steps: firstly, mixing a formaldehyde solution, hexamethylenetetramine and melamine at the temperature of 60-80 ℃ to form a mixed solution, adjusting the pH value of the mixed solution to 8.5-9.0 by using 1mol/L NaOH solution, and stirring for 5-10 minutes to obtain a transparent solution A;
step two: mixing and stirring a PVA solution, nano-montmorillonite and a silane coupling agent KH-792, adding distilled water, adding short-cut coconut shell fibers at 50-60 ℃, treating for 5-10 s at 50 ℃ by using an ultrasonic dispersion instrument, and mechanically stirring for 5-10 min to prepare a milky white suspension B;
step three: adding the milky white suspension B into the transparent solution A, and mechanically stirring for 0.5-1 h at 80 ℃; adding triethanolamine, filtering the obtained suspension, washing with distilled water, and drying by blowing at 60-80 ℃ for 1-2 h to obtain the modified chopped coconut shell fiber product.
In the first step, the mass fraction of formaldehyde in the formaldehyde solution is 35-40%, and the solvent is water.
In the first step, the mass ratio of the formaldehyde solution to the hexamethylenetetramine to the melamine is 46.8-52.3: 0.1-0.2: 47.6 to 53.1.
In the second step, the diameter of the short-cut coconut shell fiber is 20-50 um, and the length is 3-8 mm.
In the second step, the PVA solution has a PVA mass fraction of 5% and the solvent is water.
In the second step, the mass ratio of the PVA solution to the nano montmorillonite to the silane coupling agent KH-792 is 70-85: 4.4-6.9: 10-20 percent of distilled water, the adding mass of the distilled water is 1-1.2 times of the total mass of the PVA solution, the nano-montmorillonite and the silane coupling agent KH-792, and the adding mass of the short coconut shell fiber accounts for 20-30 percent of the total weight of the mixed solution of the PVA solution, the nano-montmorillonite and the silane coupling agent KH-792.
In the third step, the weight ratio of the milky white suspension B to the transparent solution A is 1:1, and the mass ratio of the triethanolamine to the hexamethylenetetramine in the first step is 1: 1-1: 1.2.
The invention directly tests that the nano montmorillonite/melamine formaldehyde resin modified short-cut coconut fiber prepared by the method has the following advantages compared with untreated fiber after being blended with polypropylene to prepare the wood-plastic composite material: the tensile strength is improved by 50 to 90 percent; the elongation at break is improved by 20 to 40 percent; the impact strength is improved by 11.8 to 32.4 percent; the friction coefficient is reduced by 12.5 to 62.5 percent; the wear rate is reduced by 61.5 to 84.4 percent; the flame retardant rating (UL94) can be improved to V-1 grade at most.
The invention has the beneficial effects that:
(1) the invention uses the chopped coconut fiber, is derived from agricultural product waste, can be degraded in natural environment, and is an environment-friendly material.
(2) The modified chopped coconut fiber has good mechanical property, tribological property and flame retardant property after being compounded with polypropylene.
(3) The preparation process of the nano montmorillonite/melamine formaldehyde resin modified chopped coconut shell fiber is operated under the water-based condition, and the preparation method does not use a solvent, so that the preparation method is environment-friendly.
(4) The modified chopped coconut fiber prepared by the invention has good heat resistance and surface characteristics, and has good interface compatibility with polypropylene; the polypropylene/polypropylene composite material has good mechanical property, tribological property and flame retardant grade.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
The examples of the invention are as follows:
example 1
The preparation method of the modified chopped coconut fibers adopted in the following examples is prepared in the following manner:
step 1:
firstly, 50g of formaldehyde solution with the mass fraction of 35%, 0.18g of hexamethylenetetramine and 56g of melamine are mixed at the temperature of 60-80 ℃, the PH value of the solution is adjusted to 8.5 by 1mol/L NaOH, and the solution is stirred for 5 minutes to obtain transparent solution A.
Step 2:
stirring 75g of 5% PVA solution, 5g of nano-montmorillonite and 20g of silane coupling agent KH-792, adding distilled water, adding 20g of unmodified chopped coconut shell fibers at 50 ℃, quickly treating for 5s at 50 ℃ by using an ultrasonic disperser, and mechanically stirring for 5min to prepare milky white suspension B;
the unmodified chopped coconut fibers of this example were 20-30um in diameter and 3-5mm in length.
And step 3:
adding 50g of the suspension B into 50g of the transparent solution A, and mechanically stirring for 0.5h at 80 ℃; adding 0.18g of triethanolamine, filtering the obtained suspension, washing with distilled water, and drying by blowing at 60 ℃ for 1h to obtain the modified chopped coconut fiber.
Analyzing the surface element content of the fiber by using an energy dispersion X-ray spectrometer to obtain the unmodified chopped coconut shell fiber, wherein the unmodified chopped coconut shell fiber comprises the following elements: 53.88 wt% of C; 44.92 wt% of O; 1.08 wt% of Si; 0.12 wt% of P.
The modified chopped coconut fiber comprises the following elements: 38.71 weight percent of C; 49.35 percent by weight of O; 5.21 wt% of Si; 0.12 wt% of P; 5.34 wt% of N; 0.45 wt% of Mg; 0.82 wt% of Al.
Analyzing the thermal decomposition curve of the fiber by a thermogravimetric analysis method to obtain the unmodified chopped coconut shell fiber with the initial decomposition temperature as follows: 159 ℃ C; maximum decomposition temperature: 361 ℃; the carbon residue amount is: 17.1 wt%.
The initial decomposition temperature of the modified chopped coconut shell fiber is as follows: 203 ℃; maximum decomposition temperature: 375 ℃; the carbon residue amount is: 20.5 wt%.
Since no feasible method and standard exist in the field of current academia for directly testing the mechanical strength and the tribological performance of the chopped fibers, the examples respectively blend the unmodified chopped coconut fibers and the modified chopped coconut fibers obtained as above with polypropylene to prepare the fiber composite material, and the products are respectively marked as unmodified fiber composite material and modified fiber composite material. The preparation process of the composite material is as follows: setting the weight ratio of the fiber to the polypropylene and the maleic anhydride grafted polypropylene (compatilizer) to be 20:75:5, carrying out melt blending under the conditions of 185 ℃ and 60r/min of rotor speed, extruding and preparing a sample, and carrying out performance detection, wherein the results are as follows:
the experimental result shows that the modified fiber composite material has good mechanical property, tribological property and flame retardant property, and the compatibility of the modified fiber composite material and macromolecules is enhanced mainly due to the increase of oxygen-containing groups on the surface of the modified fiber, so that the mechanical property and the tribological property of the modified fiber composite material are improved; surface element analysis shows that montmorillonite and nitrogen-containing groups are poured into the surface of the modified fiber through chemical grafting, so that the heat resistance of the modified fiber is greatly improved, and therefore, the modified chopped coconut fiber prepared by the method can effectively enhance the mechanical property, the tribological property and the flame retardant property of the prepared composite material.
Example 2
The preparation method of the modified chopped coconut fibers adopted in the following examples is prepared in the following manner:
step 1:
firstly, 55g of formaldehyde solution with the mass fraction of 40%, 0.15g of hexamethylenetetramine and 50g of melamine are mixed at 80 ℃, the PH value of the solution is adjusted to 9 by using 1mol/L NaOH, and the solution is stirred for 10 minutes to obtain transparent solution A.
Step 2:
stirring 85g of 5% PVA solution, 5g of nano-montmorillonite and 10g of silane coupling agent KH-792, adding distilled water, adding 10g of chopped coconut shell fiber at 50 ℃, rapidly treating for 10s at 50 ℃ by using an ultrasonic disperser, and mechanically stirring for 10min to prepare milky white suspension B;
the unmodified chopped coconut fibers of this example were 30-50um in diameter and 3-5mm in length.
And step 3:
adding 50g of the suspension B into 50g of the transparent solution A, and mechanically stirring for 1h at 80 ℃; adding 0.18g of triethanolamine, filtering the obtained suspension, washing with distilled water, and drying by blowing at 80 ℃ for 2h to obtain the modified chopped coconut fiber.
Analyzing the surface element content of the fiber by using an energy dispersion X-ray spectrometer to obtain the unmodified chopped coconut shell fiber, wherein the unmodified chopped coconut shell fiber comprises the following elements: 53.88 wt% of C; 44.92 wt% of O; 1.08 wt% of Si; 0.12 wt% of P.
The modified chopped coconut fiber comprises the following elements: 41.82 wt% of C; 46.78 weight percent of O; 4.82 wt% of Si; 0.11 wt% of P; 5.05 wt% of N; 0.63 wt% of Mg; 0.79 wt% of Al.
Analyzing the thermal decomposition curve of the fiber by a thermogravimetric analysis method to obtain the unmodified chopped coconut shell fiber with the initial decomposition temperature as follows: 159 ℃ C; maximum decomposition temperature: 361 ℃; the carbon residue amount is: 17.1 wt%.
The initial decomposition temperature of the modified chopped coconut shell fiber is as follows: 202 ℃; maximum decomposition temperature: 373 deg.C; the carbon residue amount is: 20.2 wt%.
Since no feasible method and standard exist in the field of current academia for directly testing the mechanical strength and the tribological performance of the chopped fibers, the examples respectively blend the unmodified chopped coconut fibers and the modified chopped coconut fibers obtained as above with polypropylene to prepare the fiber composite materials, and the products are respectively marked as unmodified fiber composite materials and modified fiber composite materials. The preparation process of the composite material is as follows: setting the weight ratio of unmodified chopped coconut fiber or modified chopped coconut fiber to polypropylene and maleic anhydride grafted polypropylene (compatilizer) to be 20:8075:5, carrying out melt blending at 185 ℃ and at the rotor speed of 60r/min, extruding a sample to prepare a sample, and carrying out performance detection, wherein the results are as follows:
example 3
The preparation method of the modified chopped coconut fibers adopted in the following examples is prepared in the following manner:
step 1:
58g of formaldehyde solution with the mass fraction of 38%, 0.16g of hexamethylenetetramine and 55g of melamine are mixed at 70 ℃, the pH value of the solution is adjusted to 8.8 by using 1mol/L NaOH, and the solution is stirred for 8 minutes to obtain a transparent solution A.
Step 2:
stirring 70g of 5% PVA solution, 4g of nano-montmorillonite and 16g of silane coupling agent KH-792, adding distilled water, adding 20g of chopped coconut shell fiber at 55 ℃, rapidly processing for 8s at 50 ℃ by using an ultrasonic disperser, and mechanically stirring for 7min to prepare milky white suspension B;
the unmodified chopped coconut fibers of this example were 30-40um in diameter and 5-8mm in length.
And step 3:
adding 50g of the suspension B into 50g of the transparent solution A, and mechanically stirring for 0.8h at 80 ℃; adding 0.17g of triethanolamine, filtering the obtained suspension, washing with distilled water, and drying by blowing at 70 ℃ for 1.5h to obtain the modified chopped coconut shell fiber.
Analyzing the surface element content of the fiber by using an energy dispersion X-ray spectrometer to obtain the unmodified chopped coconut shell fiber, wherein the unmodified chopped coconut shell fiber comprises the following elements: 53.88 wt% of C; 44.92 wt% of O; 1.08 wt% of Si; 0.12 wt% of P.
The modified chopped coconut fiber comprises the following elements: 40.62 weight percent of C; 47.88 weight percent of O; 4.89 wt% of Si; 0.1 wt% of P; 5.18 wt% of N; 0.51 wt% of Mg; 0.82 wt% of Al.
Analyzing the thermal decomposition curve of the fiber by a thermogravimetric analysis method to obtain the unmodified chopped coconut shell fiber with the initial decomposition temperature as follows: 159 ℃ C; maximum decomposition temperature: 361 ℃; the carbon residue amount is: 17.1 wt%.
The initial decomposition temperature of the modified chopped coconut shell fiber is as follows: 299 ℃; maximum decomposition temperature: 371 ℃; the carbon residue amount is: 19.9 wt%.
Since no feasible method and standard for directly testing the mechanical strength and the tribological performance of the chopped fibers exist at present, in the examples, unmodified chopped coconut fibers and the modified chopped coconut fibers obtained as described above are respectively blended with polypropylene to prepare fiber composites, and the products are respectively marked as unmodified fiber composites and modified fiber composites. The preparation process of the composite material is as follows: setting the weight ratio of unmodified chopped coconut fiber or modified chopped coconut fiber to polypropylene and maleic anhydride grafted polypropylene (compatilizer) to be 20:8075:5, carrying out melt blending at 185 ℃ and at the rotor speed of 60r/min, extruding to prepare a sample, and carrying out performance detection, wherein the results are as follows:
example 4
The preparation method of the modified chopped coconut fibers adopted in the following examples is prepared in the following manner:
step 1:
53g of formaldehyde solution with the mass fraction of 38%, 0.17g of hexamethylenetetramine and 60g of melamine are mixed at 75 ℃, the pH value of the solution is adjusted to 8.5 by using 1mol/L NaOH, and the solution is stirred for 5 minutes to obtain a transparent solution A.
Step 2:
stirring 80g of 5% PVA solution, 6g of nano-montmorillonite and 12g of silane coupling agent KH-792, adding distilled water, adding 20g of chopped coconut shell fiber at 55 ℃, rapidly treating for 10s at 50 ℃ by using an ultrasonic disperser, and mechanically stirring for 7min to prepare milky white suspension B;
the unmodified chopped coconut fibers of this example were 40-50um in diameter and 3-6mm in length.
And step 3:
adding 50g of the suspension B into 50g of the transparent solution A, and mechanically stirring for 1h at 80 ℃; adding 0.19g of triethanolamine, filtering the obtained suspension, washing with distilled water, and drying by blowing at 75 ℃ for 1.5h to obtain the modified chopped coconut shell fiber.
Analyzing the surface element content of the fiber by using an energy dispersion X-ray spectrometer to obtain the unmodified chopped coconut shell fiber, wherein the unmodified chopped coconut shell fiber comprises the following elements: 53.88 wt% of C; 44.92 wt% of O; 1.08 wt% of Si; 0.12 wt% of P.
The modified chopped coconut fiber comprises the following elements: 39.03 percent by weight of C; 48.63 wt% of O; 5.34 wt% of Si; 0.11 wt% of P; 5.48 wt% of N; 0.52 wt% of Mg; 0.89 wt% of Al.
Analyzing the thermal decomposition curve of the fiber by a thermogravimetric analysis method to obtain the unmodified chopped coconut shell fiber with the initial decomposition temperature as follows: 159 ℃ C; maximum decomposition temperature: 361 ℃; the carbon residue amount is: 17.1 wt%.
The initial decomposition temperature of the modified chopped coconut shell fiber is as follows: 206 ℃; maximum decomposition temperature: 378 ℃; the carbon residue amount is: 24.5 wt%.
Since no feasible method and standard exist in the field of current academia for directly testing the mechanical strength and the tribological performance of the chopped fibers, the examples respectively blend the unmodified chopped coconut fibers and the modified chopped coconut fibers obtained as above with polypropylene to prepare the fiber composite materials, and the products are respectively marked as unmodified fiber composite materials and modified fiber composite materials. The preparation process of the composite material is as follows: setting the weight ratio of unmodified chopped coconut fiber or modified chopped coconut fiber to polypropylene and maleic anhydride grafted polypropylene (compatilizer) to be 20:8075:5, carrying out melt blending at 185 ℃ and at the rotor speed of 60r/min, extruding a sample to prepare a sample, and carrying out performance detection, wherein the results are as follows:
example 5
The preparation method of the modified chopped coconut fibers adopted in the following examples is prepared in the following manner:
step 1:
firstly, 55g of formaldehyde solution with the mass fraction of 35%, 0.17g of hexamethylenetetramine and 60g of melamine are mixed at 70 ℃, the PH value of the solution is adjusted to 9.0 by using 1mol/L NaOH, and the solution is stirred for 10 minutes to obtain a transparent solution A.
Step 2:
stirring 78g of 5% PVA solution, 7g of nano-montmorillonite and 17g of silane coupling agent KH-792, adding distilled water, adding 20g of chopped coconut shell fiber at 50 ℃, rapidly treating for 10s at 50 ℃ by using an ultrasonic disperser, and mechanically stirring for 8min to prepare milky white suspension B;
the unmodified chopped coconut fibers of this example were 35-45um in diameter and 3-7mm in length.
And step 3:
adding 50g of the suspension B into 50g of the transparent solution A, and mechanically stirring for 0.65h at 80 ℃; adding 0.19g of triethanolamine, filtering the obtained suspension, washing with distilled water, and drying by blowing at 65 ℃ for 2 hours to obtain the modified chopped coconut fiber.
Analyzing the surface element content of the fiber by using an energy dispersion X-ray spectrometer to obtain the unmodified chopped coconut shell fiber, wherein the unmodified chopped coconut shell fiber comprises the following elements: 53.88 wt% of C; 44.92 wt% of O; 1.08 wt% of Si; 0.12 wt% of P.
The modified chopped coconut fiber comprises the following elements: 40.73 wt% of C; 47.67 wt% of O; 5.02 wt% of Si; 0.1 wt% of P; 5.06 wt% of N; 0.51 wt% of Mg; 0.91 wt% of Al.
Analyzing the thermal decomposition curve of the fiber by a thermogravimetric analysis method to obtain the unmodified chopped coconut shell fiber with the initial decomposition temperature as follows: 159 ℃ C; maximum decomposition temperature: 361 ℃; the carbon residue amount is: 17.1 wt%.
The initial decomposition temperature of the modified chopped coconut shell fiber is as follows: 200 ℃; maximum decomposition temperature: 372 deg.C; the carbon residue amount is: 20 wt%.
Since no feasible method and standard exist in the field of current academia for directly testing the mechanical strength and the tribological performance of the chopped fibers, the examples respectively blend the unmodified chopped coconut fibers and the modified chopped coconut fibers obtained as above with polypropylene to prepare the fiber composite materials, and the products are respectively marked as unmodified fiber composite materials and modified fiber composite materials. The preparation process of the composite material is as follows: setting the weight ratio of unmodified chopped coconut fiber or modified chopped coconut fiber to polypropylene and maleic anhydride grafted polypropylene (compatilizer) to be 20:8075:5, carrying out melt blending at 185 ℃ and at the rotor speed of 60r/min, extruding a sample to prepare a sample, and carrying out performance detection, wherein the results are as follows:
the embodiment shows that the chopped coconut fiber is modified by selecting proper reaction conditions and reaction reagents, so that the nitrogen content of the surface can be increased, the polarity of the surface can be increased, the interface strength of the chopped coconut fiber and a polypropylene polymer material composite material can be improved, and the chopped coconut fiber has excellent mechanical property and tribological property; the existence of the montmorillonite of the nitrogen element on the surface of the modified fiber can effectively improve the thermal property of the modified fiber, further improve the flame retardant grade of the composite material, and meet the use requirement of the wood-plastic composite material.
Claims (4)
1. A preparation method of nano montmorillonite/melamine formaldehyde resin modified chopped coconut fiber is characterized by comprising the following steps:
the method comprises the following steps: firstly, mixing a formaldehyde solution, hexamethylenetetramine and melamine at the temperature of 60-80 ℃ to form a mixed solution, adjusting the pH value of the mixed solution to 8.5-9.0 by using 1mol/L NaOH solution, and stirring for 5-10 minutes to obtain a transparent solution A;
step two: mixing and stirring a PVA solution, nano-montmorillonite and a silane coupling agent KH-792, adding distilled water, adding short-cut coconut shell fibers at 50-60 ℃, treating for 5-10 s at 50 ℃ by using an ultrasonic dispersion instrument, and mechanically stirring for 5-10 min to prepare a milky white suspension B;
in the second step, the diameter of the short-cut coconut shell fiber is 20-50 um, and the length of the short-cut coconut shell fiber is 3-8 mm;
step three: adding the milky white suspension B into the transparent solution A, and mechanically stirring for 0.5-1 h at 80 ℃; adding triethanolamine, filtering, washing with distilled water, and drying by blowing air at 60-80 ℃ for 1-2 h to obtain the modified chopped coconut shell fiber product.
2. The preparation method of the nano montmorillonite/melamine formaldehyde resin modified chopped coconut fiber according to claim 1, which is characterized by comprising the following steps: in the first step, the mass ratio of the formaldehyde solution to the hexamethylenetetramine to the melamine is 46.8-52.3: 0.1-0.2: 47.6 to 53.1.
3. The preparation method of the nano montmorillonite/melamine formaldehyde resin modified chopped coconut fiber according to claim 1, which is characterized by comprising the following steps: in the second step, the mass ratio of the PVA solution to the nano montmorillonite to the silane coupling agent KH-792 is 70-85: 4.4-6.9: 10-20 percent of distilled water, the adding mass of the distilled water is 1-1.2 times of the total mass of the PVA solution, the nano-montmorillonite and the silane coupling agent KH-792, and the adding mass of the short coconut shell fiber accounts for 20-30 percent of the total weight of the mixed solution of the PVA solution, the nano-montmorillonite and the silane coupling agent KH-792.
4. The preparation method of the nano montmorillonite/melamine formaldehyde resin modified chopped coconut fiber according to claim 1, which is characterized by comprising the following steps: in the third step, the weight ratio of the milky white suspension B to the transparent solution A is 1:1, and the mass ratio of the triethanolamine to the hexamethylenetetramine in the first step is 1: 1-1: 1.2.
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