CN113801447A - Preparation method of toughened and reinforced polylactic acid composite material - Google Patents
Preparation method of toughened and reinforced polylactic acid composite material Download PDFInfo
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- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y70/00—Materials specially adapted for additive manufacturing
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
- C08F283/02—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polycarbonates or saturated polyesters
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21B1/00—Fibrous raw materials or their mechanical treatment
- D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
- D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
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Abstract
The invention relates to the technical field of 3D printing materials, in particular to a preparation method of a toughened and reinforced polylactic acid composite material. A preparation method of a toughened and reinforced polylactic acid composite material comprises the following steps: (1) preparing a crude grafting product; (2) purifying the grafted product; (3) pretreating bagasse; (4) preparing the PLA composite material. The toughening and enhancement modification of the polylactic acid PLA are realized by utilizing the bifunctional characteristic of GMA, and the selection and application range of FDM 3D printing materials are expanded; and the polylactic acid PLA is prepared by adopting a melt polymerization method during toughening and strengthening, the process steps are simple and easy to operate, the industrial production is favorably realized, the use of chemical solvents is reduced, and the environment is protected.
Description
Technical Field
The invention relates to the technical field of 3D printing materials, in particular to a preparation method of a toughened and reinforced polylactic acid composite material.
Background
The 3D printing technology, also called additive manufacturing technology (AM), can be classified into three-dimensional Stereolithography (SLA), Digital Light Processing (DLP), polymer jetting (Polyjet), continuous liquid interface extraction (3DP), Fused Deposition Modeling (FDM), Direct Ink Writing (DIW), Selective Laser Sintering (SLS), Selective Heat Sintering (SHS), and Rapid Liquid Printing (RLP), according to the difference of the molding methods, and each of the 3D printing technologies has characteristics, and has selectivity for materials and objects to be printed.
Fused Deposition Modeling (FDM) is the earliest and inexpensive 3D printing technology developed and used. FDM material prints intensity higher, is a 3D printing technique that easily industrial production. At present, the materials which can be used for FDM 3D printing comprise polymers and composite materials such as polylactic acid (PLA), ABS plastic and Polycarbonate (PC), and common thermoplastic plastics such as Polyethylene (PE), polypropylene (PP) and nylon 6(PA6) in a common plastic forming mode such as blow molding, wherein the PE and the PP can be easily processed into wires required by FDM 3D printing, but in the actual printing process, the printing requirement cannot be met due to the fact that the delamination cracking phenomenon often occurs; the PA6 is prone to warp during printing, which affects the printing effect and results in poor quality of printed products. Therefore, the FDM 3D printed material is required to have the following characteristics: has better toughness, rigidity, high-temperature fluidity, small molding shrinkage, good adhesiveness and lower melting temperature. The material that can be used for FDM 3D to print at present is less in kind, and the price is higher, only has partial thermoplasticity macromolecular material to satisfy the printing requirement, so, the research and development about neotype FDM 3D printing material has very important meaning to expanding 3D printing technique to more field infiltration and actual industrial application.
PLA is one of biodegradable plastics which are earlier in development and most widely applied, and has a gap with the development of foreign countries, and through recent development in China, the technology is gradually mature, and the application is gradually expanded; PLA is used as a biomass-based degradable material with the highest industrialization level at present, has the characteristics of good biodegradability, small shrinkage rate, difficult warping and the like, and is widely applied to the FDM 3D printing field. However, because of high cost, brittleness and the like, PLA has great limitations when used as FDM 3D printing material, and generally, PLA needs to be physically or chemically modified to improve PLA performance to prepare structural polymer material or composite material; or functional polymer materials or composite materials with special properties (such as piezoelectricity, conductivity and the like).
The preparation of the FDM 3D printing material of the cellulose can not only increase the variety of the 3D printing material, but also provide a feasible path for the high-value utilization of the cellulose. Modifying plastics with natural fibers to enhance the performance of plastic matrices and save costs, replacing glass and other synthetic materials, is a hot spot of current research. However, the natural fiber has poor compatibility with the polymer matrix, and is easy to agglomerate in the processing process, so that the cellulose has low dispersibility in the polymer matrix, the mechanical property of the cellulose/polymer is poor, and the composite material can keep good mechanical property under the condition of low addition of the cellulose. The interaction between the fibers and the matrix is the basis for the transfer of stress from the matrix to the fibers, and the modification of the fiber surface with the multifunctional monomer can be utilized in a secondary reaction with the polymer matrix to provide a stable bonding network between the fibers and the polymer. The wood-plastic composite material effectively combines the advantages of natural plant fibers and plastics, has the high strength and high elasticity of the natural plant fibers, also has the high elasticity and fatigue resistance of the plastics, has high mechanical strength, and is easy to process and form.
At present, the research level about the FDM 3D novel structural material is limited, limited by the performance and cost of the existing printing material, and the development and popularization of FDM 3D printing are hindered. Cellulose as a biodegradable biomass resource can save the cost of 3D printing, and research on composite materials for FDM 3D printing becomes a hotspot. The novel structural 3D printing material is designed from the molecular level, the defects of the existing material are improved, or the composite material with low preparation cost and high strength is prepared, and the method has positive significance for widening the selectable range of the 3D printing material.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide a preparation method of a toughened and reinforced polylactic acid composite material, which aims to solve the problems of the existing 3D printing material.
In order to achieve the purpose, the invention provides the following technical scheme:
a preparation method of a toughened and reinforced polylactic acid composite material comprises the following steps:
(1) preparation of the crude graft product: crushing the PLA master batch, and fully mixing the crushed PLA master batch with a reaction monomer of glycidyl methacrylate GMA and a free radical initiator of tert-butyl peroxybenzoate TBPB; manually feeding the mixture into a micro double-screw extruder, and extruding after the reaction is finished to obtain a coarse grafting product PLA-GMA;
(2) purification of the graft product: completely dissolving the crude grafting product PLA-GMA in chloroform at room temperature, slowly adding excessive absolute ethyl alcohol to precipitate, stirring, filtering, washing with absolute ethyl alcohol for 2-3 times, and vacuum drying at 75 ℃ for 12h to obtain a purified grafting product PLA-GMA;
(3) pretreatment of bagasse: soaking the bagasse in water for 10-14h, draining, washing with deionized water for 2-3 feet, and drying in a 105 ℃ oven to constant weight to obtain bagasse fiber BF; adding the bagasse fiber BF into deionized water, boiling for 40min, then placing in a 105 ℃ oven to dry to constant weight after ultrasonic treatment for 40min, and then obtaining bagasse cellulose BC through alkali treatment, bleaching and screening;
(4) preparing a PLA composite material: uniformly mixing bagasse cellulose BC, purified graft products PLA-GMA and PLA in advance, adding into a double-screw mixing extruder, blending for 4min at 165 ℃ and 30rpm, and performing extrusion molding to obtain the PLA composite material.
Preferably, the content of glycidyl methacrylate GMA relative to PLA in the step (1) is 20 percent; the dosage of tert-butyl peroxybenzoate TBPB relative to PLA is 3 percent; the reaction temperature was 185 ℃.
Preferably, in the step (2), the volume ratio of the mass of the bagasse fiber BF to the deionized water is 1 mg: 20L.
Preferably, the alkali treatment in the step (3) is specifically performed by: in the following steps of 1: stirring with 10% NaOH solution at 70 deg.C for 10 hr to remove hemicellulose under the condition of 20mg/L solid-to-liquid ratio, filtering after the reaction is finished, washing with deionized water until the filtrate is neutral, and drying at 50 deg.C for 12 hr.
Preferably, the specific operations of the bleaching treatment in the step (3) are as follows: in the following steps of 1: 20mg/L of solid-to-liquid ratio, using 20% of H2O2Heating the solution at 75 deg.C for 2h, filtering, washing with deionized water for 4-5 times, washing with ethanol for 5-6 times, and vacuum drying at 60 deg.C for 12 h.
Preferably, the step (3) is carried out by sieving through 80-200 meshes.
Preferably, the amount of the bagasse cellulose BC used in the step (4) is 10-50% relative to the PLA; the amount of PLA-GMA as a purified graft product is 10-30% relative to PLA.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention fully utilizes the bifunctional property of GMA to realize toughening, reinforcing and modifying of polylactic acid PLA, and expands the selection and application range of FDM 3D printing materials.
(2) The polylactic acid PLA is prepared by a melt polymerization method during toughening and strengthening, the process steps are simple and easy to operate, the industrial production is favorably realized, the use of chemical solvents is reduced, and the polylactic acid PLA is environment-friendly.
(3) The polylactic acid composite material has high cellulose load, reduces the usage amount of polylactic acid, realizes high-value utilization of bagasse resources, and saves the production cost.
Drawings
FIG. 1 is a stress-strain plot of various composite materials;
FIG. 2 is a DSC plot of the temperature rise of different composites to 200 ℃ at a 100 ℃/min temperature rise rate;
FIG. 3 is a stress-strain plot of composite materials with different amounts of PLA-GMA added;
FIG. 4 is a DSC graph of the temperature rise of the composite material to 200 ℃ at a temperature rise rate of 100 ℃/min for different amounts of PLA-GMA added;
FIG. 5 is a stress-strain curve of composite materials of different bagasse cellulose BC particle sizes;
FIG. 6 is a DSC curve graph of temperature rise of composite materials with different bagasse cellulose BC particle sizes to 200 ℃ at a temperature rise rate of 100 ℃/min;
FIG. 7 is a stress-strain curve of composite materials with different amounts of bagasse cellulose BC added;
FIG. 8 is a DSC curve chart of the temperature rise of the composite material with different amounts of bagasse cellulose BC to 200 ℃ at a temperature rise rate of 100 ℃/min;
fig. 9 is a graph of the thermal weight loss of different composites.
Detailed Description
In the following, the technical solutions of the present invention will be described clearly and completely, and it is obvious that the described embodiments are some, not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1: preparation of the graft product PLA-GMA
(1) Preparation of the crude graft product: crushing the PLA master batch, and fully mixing the crushed PLA master batch with a reaction monomer of glycidyl methacrylate GMA and a free radical initiator of tert-butyl peroxybenzoate TBPB; manually feeding the mixture into a micro double-screw extruder, and extruding after the reaction is finished to obtain a coarse grafting product PLA-GMA;
the influence rule of the reaction temperature, the reaction time, the using amount of glycidyl methacrylate GMA and the using amount of tert-butyl peroxybenzoate TBPB on the grafting rate of PLA-GMA is explored through a single-factor experiment, and the process conditions for obtaining the highest grafting rate are as follows: the reaction temperature is 185 ℃; the using amount of the glycidyl methacrylate GMA relative to the PLA is 20 percent; the using amount of tert-butyl peroxybenzoate TBPB relative to PLA is 3%, the finally obtained grafting rate is 10.33%, Mn is 125286g/mol, Mw is 196520g/mol, PDI is 1.57, and the molecular weight distribution is relatively uniform; the tensile strength is 15.94MPa, the elastic modulus is 969.01MPa, the elongation at break is 278.17%, and the toughness of the chemically grafted GMA and PLA is greatly improved;
(2) purification of the graft product: completely dissolving the crude grafting product PLA-GMA in chloroform at room temperature, slowly adding excessive absolute ethyl alcohol to precipitate, stirring, filtering, washing with absolute ethyl alcohol for 2-3 times, and vacuum drying at 75 ℃ for 12h to obtain a purified grafting product PLA-GMA; wherein the volume ratio of the mass of the bagasse fiber BF to the deionized water is 1 mg: 20L.
Example 2: preparation of bagasse cellulose BC
Soaking the bagasse in water for 12h, draining, washing with deionized water for 2-3 feet, and placing in a 105 ℃ oven to dry to constant weight to obtain bagasse fiber BF; adding the bagasse fiber BF into deionized water, boiling for 40min, then placing in a 105 ℃ oven to dry to constant weight after ultrasonic treatment for 40min, and then obtaining bagasse cellulose BC through alkali treatment, bleaching and screening by 80-200 meshes;
wherein the alkali treatment comprises the following specific operations: in the following steps of 1: stirring with 10% NaOH solution at 70 deg.C for 10 hr to remove hemicellulose under the condition of 20mg/L solid-to-liquid ratio, filtering after the reaction is finished, washing with deionized water until the filtrate is neutral, and drying at 50 deg.C for 12 hr;
the specific operation of the bleaching treatment is as follows: in the following steps of 1: 20mg/L of solid-to-liquid ratio, using 20% of H2O2The solution was heated at 75 ℃ for 2h, filtered after completion, washed 4 times with deionized water, then 5 times with ethanol, and then dried under vacuum at 60 ℃ for 12 h.
Example 3: preparation of PLA composite Material
Uniformly mixing bagasse cellulose BC, purified graft products PLA-GMA and PLA in advance according to the following table 1, adding into a double-screw mixing extruder, blending for 4min at 165 ℃ and 30rpm, and performing extrusion molding to obtain the PLA composite material.
TABLE 1 preparation of PLA composite materials
Note 1: BCA, BCB and BCC are bagasse cellulose sieved by 80 meshes, 120 meshes and 200 meshes respectively; the percentages in table 1 are relative to the amount of PLA added.
1. The influence of bagasse cellulose BC and PLA-GMA on the composite material is explored
Comparative example 1: commercial product (Rambo, PLA 500g, color: WOOD WOOD; diameter: 1.75 mm);
experimental example 1: BCB + PLA, wherein the addition amount of BCB relative to PLA is 10%, and the preparation method is the same as the above and is recorded as 10% BCB/PLA;
experimental example 2: BCB + PLA, wherein the addition amounts of BCB and PLA are equal, and the preparation method is the same as the above and is marked as BCB/PLA;
experimental example 3: BCB + PLA-GMA, wherein the addition amount of BCB relative to PLA-GMA is 10%, and the preparation method is the same as the above and is recorded as 10% BCB/PLA-GMA;
experimental example 4: pure PLA, the preparation method is the same as above;
the properties of each of the composite materials of comparative example 1 and experimental examples 1 to 4 were measured, and the results are shown in table 2 and fig. 1;
the crystallinity of comparative example 1, experimental examples 1-2 and experimental example 4 was measured, and the results are shown in fig. 2.
TABLE 2 results of the Effect of bagasse cellulose BC and PLA-GMA on the composite Properties
| Group of | Modulus of elasticity (MPa) | Tensile Strength (MPa) | Elongation at Break (%) |
| Comparative example 1 | 1503.45 | 21.07 | 2.07 |
| Experimental example 1 | 2287.91 | 37.82 | 2.23 |
| Experimental example 2 | 5204.84 | 45.46 | 1.03 |
| Experimental example 3 | 1510.47 | 25.71 | 4.77 |
Comparing experimental example 1, experimental example 2 and comparative example 1 with fig. 1 and table 2, it can be seen that the elastic modulus and tensile strength of experimental example 1 and experimental example 2 are significantly greater than those of comparative example 1, which illustrates that the addition of BC can improve the elastic modulus and tensile strength of the composite material; comparing the experimental example 1 with the experimental example 2, it can be seen that the elastic modulus and the tensile strength of the experimental example 2 are higher than those of the experimental example 1, but the elongation at break is lower than that of the experimental example 1, and the addition of BC can improve the elastic modulus and the tensile strength of the composite material, but can reduce the elongation at break; comparing experimental example 3 with comparative example 1 and example 1, it can be seen that when BC and PLA-GMA are added together, although the elastic modulus and tensile strength of the composite film are reduced (still higher than comparative example 1), the elongation at break of the composite film is significantly increased. In conclusion, it can be seen that addition of BC alone increases the elastic modulus and tensile strength of the composite film, but decreases its elongation at break; when BC and PLA-GMA are added simultaneously, the elongation at break of the composite film is significantly increased.
As can be seen from fig. 2, the relative crystallinity of PLA in both experimental example 1 and experimental example 2 composites was higher than that of experimental example 4; it is shown that the addition of BCB to PLA promotes the crystallization of PLA and increases the strength and hardness of the composite. In addition, in FIG. 2, except for Experimental example 4, the composite materials of comparative example 1, Experimental example 1 and example 2 all showed an upward heat release dispersion peak near 120 ℃, which is a cold crystallization peak of PLA in the composite material, and it is shown that BCB acts as a heterogeneous nucleating agent for PLA in the composite material, and can increase the rigidity and toughness of the composite material.
2. The influence of different PLA-GMA addition amounts on the composite material is researched
The properties of each of the composites of example 2 and examples 8-11 were measured and the results are shown in Table 3 below and FIG. 3;
DSC test graphs of example 2 and examples 8-11 are also prepared, and the results are shown in FIG. 4.
TABLE 3 results of the effect of different amounts of PLA-GMA addition on the composite properties
| Composite material | Modulus of elasticity (MPa) | Tensile Strength (MPa) | Elongation at Break (%) |
| Composite material 8 | 1972.63 | 36.38 | 2.87 |
| Composite material 9 | 2016.34 | 40.64 | 3.27 |
| |
2106.81 | 41.23 | 3.70 |
| |
2112.03 | 41.29 | 4.60 |
| Composite material 11 | 2137.68 | 38.81 | 3.13 |
As can be seen from the combination of FIG. 2 and Table 3, when the amount of PLA-GMA added to PLA was increased from 10% to 25%, the elastic modulus was increased from 1972.63MPa to 2112.03 MPa; the tensile strength increased from 36.38MPa to 41.29 MPa; elongation at break increased from 2.87% to 4.60%; compared with the experimental example 1, the tensile strength of the composite material 2 is improved by 9.18%, and the elongation at break is improved by 106.28%; in conclusion, with the increase of the addition amount of PLA-GMA, various performance indexes of the composite material are enhanced, and when the addition amount is 25%, the tensile strength and the elongation at break reach the optimal values. Compared with the composite material without PLA-GMA, the tensile strength and the elongation at break are both obviously improved.
The relative crystallinity (X) of PLA in various composite materials was calculated by the formulac)。
In the formula:
ΔHm-enthalpy of fusion (J/g) of the composite material;
ΔHm*-melting enthalpy (93.7J/g) of 100% crystalline polylactic acid;
omega-mass fraction (%) of polylactic acid in the composite material.
As can be seen from FIG. 4, as the amount of PLA-GMA added increases, the T of the composite material increasesgPresenting a gradually decreasing trend; melting Point (T) compared to a composite without PLA-GMAm) Cold crystallization exotherm (. DELTA.H)c) Heat absorption by heat fusion (. DELTA.H)m) And degree of crystallinity (X)C) Is reduced to some extent, wherein TmAnd Δ HmThe decrease indicates a decrease in the energy required to melt the composite to which the PLA-GMA is added; Δ HcThe decrease indicates that the addition of PLA-GMA acts as a compatibilizer, increasing the heterogeneous nucleation of PLA by the BCThe PLA-GMA has the best compatibilization effect in the composite material when the addition amount of the PLA-GMA relative to the PLA is 25%, and the strength and the hardness of the composite material can be well improved.
3. The influence of different bagasse cellulose BC particle sizes on the composite material is explored
The properties of each of the composites of examples 1-3 were measured and the results are shown in Table 4 below and FIG. 5;
and DSC graphs of examples 1-3 were prepared, and the results are shown in FIG. 6.
TABLE 4 results of the effect of different bagasse cellulose BC particle sizes on the composite material properties
| Composite material | Modulus of elasticity (MPa) | Tensile Strength (MPa) | Elongation at Break (%) |
| |
2187.13 | 41.36 | 3.6 |
| |
2112.03 | 41.29 | 4.6 |
| |
1987.21 | 38.96 | 5.1 |
As can be seen from the combination of FIG. 5 and Table 4, the elongation at break of the composite increased from 3.6% to 5.1% when the particle size of the BC was from 80 mesh to 200 mesh. Compared with the comparative example 2, the tensile strength of the composite material 2 is improved by 9.18 percent, and the elongation at break is improved by 106.28 percent; compared with comparative example 2, the tensile strength of the composite material 3 is improved by 9.18%, and the elongation at break is improved by 128.70%. From the above, it can be seen that the elastic modulus and the tensile strength tend to decrease with decreasing particle size, but the elongation at break gradually increases; compared with the composite material without PLA-GMA, the tensile strength and the elongation at break are both obviously improved. Overall, the composite material prepared by using 120-mesh BC has moderate elastic modulus, tensile strength and elongation at break.
As can be seen from FIG. 6, as the particle size of BC decreases, the T of the composite materialgIncreasing, Tm and Δ HmIncreasing with decreasing particle size, XCThe gradual increase is probably because the smaller the particle size of the BC is, the larger the specific surface area is, the more hydrogen bonds are formed between the BC and hydroxyl on PLA-GMA, the better the compatibility of the composite material is, the growth of continuous phase PLA crystalline regions is promoted, and therefore, the relative crystallinity of the PLA is increased, and the strength and the hardness of the composite material are further improved.
4. The influence of different bagasse cellulose BC addition amounts on the composite material is researched
The properties of each of the composites of examples 2 and 4-7 were measured and the results are shown in Table 5 below and FIG. 7;
DSC graphs of example 2 and examples 4-7 were also prepared, and the results are shown in FIG. 8.
TABLE 5 results of the effect of different amounts of bagasse cellulose BC on the properties of the composite materials
| Composite material | Modulus of elasticity (MPa) | Tensile Strength (MPa) | Elongation at Break (%) |
| |
2112.03 | 41.29 | 4.6 |
| |
2236.14 | 41.83 | 3.77 |
| |
2554.53 | 44.79 | 3.4 |
| Composite material 6 | 2608.44 | 46.67 | 3.03 |
| Composite material 7 | 3233.29 | 47.55 | 2.77 |
As can be seen from FIG. 7 and Table 5, as the addition amount of BC increases, the elastic modulus and tensile strength gradually increase, and the elongation at break gradually decreases; when the addition amount of BCB equivalent to PLA reaches 40%, the elastic modulus and the tensile strength reach 2608.44MPa and 46.67MPa respectively, and the breaking tensile rate is reduced to 3.03%. The addition of the bagasse cellulose BC can influence the toughness and the strength of the composite material. Overall, the composite material prepared when the amount of BCB relative to PLA was 30% had moderate elastic modulus, tensile strength and elongation at break.
As can be seen from FIG. 8, the relative crystallinity of continuous phase PLA in the composite material is gradually increased with the increase of the addition amount of BC, which shows that BC can promote the formation of PLA crystallization areas in the composite material, and further increase the strength and hardness of the composite material.
5. Exploring the thermal stability of different composite materials
Comparative example 2: commercial product (Rambo, PLA 500g, color: WOOD WOOD; diameter: 1.75 mm);
experimental example 5: BCB + PLA, wherein the addition amount of BCB relative to PLA is 10%, and the preparation method is the same as the above and is recorded as 10% BCB/PLA;
experimental example 6: BCB + PLA, wherein the addition amounts of BCB and PLA are equal, and the preparation method is the same as the above and is marked as BCB/PLA;
experimental example 7: BCB + PLA-GMA + PLA, wherein the addition amount of BCB relative to PLA is 40%, the addition amount of BCB relative to PLA is 25%, and the preparation method is the same as the above, and the content is recorded as 40% BCB/25% PLA-GMA/PLA;
experimental example 8: BCC-GMA + PLA, wherein the addition amount of BCC relative to PLA is 30 percent, and the preparation method is the same as the above and is recorded as 30 percent BCC-GMA/PLA;
the thermogravimetric plot of the composite material described above was made and the results are shown in figure 9.
As can be seen from fig. 9, comparative example 2 started cracking around 279.61 ℃, at 318.08 ℃ to the maximum mass loss rate to the first stage; in the second decomposition stage, there was a decomposition peak at 548.04 ℃ and 633.79 ℃ respectively.
T in Experimental example 55％、T50％And T100％Respectively as follows: 308.61 deg.C, 349.79 deg.C and 353.98 deg.C;
t in Experimental example 65％、T50％And T100％Respectively as follows: 307.08347.88 ℃ and 347.31 ℃;
t in Experimental example 75％、T50％And T100％Respectively as follows: 308.60 deg.C, 355.02 deg.C and 355.44 deg.C;
t in Experimental example 85％、T50％And T100％Respectively as follows: 329.41 deg.C, 356.45 deg.C and 358.31 deg.C.
From the above, it can be seen that the composite material of the present invention has better thermal stability.
In conclusion, the toughening and enhancement modification of polylactic acid (PLA) are realized by utilizing the bifunctional property of GMA, and the selection and application range of FDM 3D printing materials are expanded; and the polylactic acid PLA is prepared by adopting a melt polymerization method during toughening and strengthening, the process steps are simple and easy to operate, the industrial production is favorably realized, the use of chemical solvents is reduced, and the environment is protected.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.
Claims (7)
1. The preparation method of the toughened and reinforced polylactic acid composite material is characterized by comprising the following steps:
(1) preparation of the crude graft product: crushing the PLA master batch, and fully mixing the crushed PLA master batch with a reaction monomer of glycidyl methacrylate GMA and a free radical initiator of tert-butyl peroxybenzoate TBPB; manually feeding the mixture into a micro double-screw extruder, and extruding after the reaction is finished to obtain a coarse grafting product PLA-GMA;
(2) purification of the graft product: completely dissolving the crude grafting product PLA-GMA in chloroform at room temperature, slowly adding excessive absolute ethyl alcohol to precipitate, stirring, filtering, washing with absolute ethyl alcohol for 2-3 times, and vacuum drying at 75 ℃ for 12h to obtain a purified grafting product PLA-GMA;
(3) pretreatment of bagasse: soaking the bagasse in water for 10-14h, draining, washing with deionized water for 2-3 feet, and drying in a 105 ℃ oven to constant weight to obtain bagasse fiber BF; adding the bagasse fiber BF into deionized water, boiling for 40min, then placing in a 105 ℃ oven to dry to constant weight after ultrasonic treatment for 40min, and then obtaining bagasse cellulose BC through alkali treatment, bleaching and screening;
(4) preparing a PLA composite material: uniformly mixing bagasse cellulose BC, purified graft products PLA-GMA and PLA in advance, adding into a double-screw mixing extruder, blending for 4min at 165 ℃ and 30rpm, and performing extrusion molding to obtain the PLA composite material.
2. The preparation method according to claim 1, wherein the glycidyl methacrylate GMA is used in the step (1) in an amount of 20% relative to the PLA; the dosage of tert-butyl peroxybenzoate TBPB relative to PLA is 3 percent; the reaction temperature was 185 ℃.
3. The preparation method according to claim 1, wherein in the step (2), the mass ratio of the bagasse fiber BF to the deionized water is 1 mg: 20L.
4. The production method according to claim 1, wherein the alkali treatment in the step (3) is specifically performed by: in the following steps of 1: stirring with 10% NaOH solution at 70 deg.C for 10 hr to remove hemicellulose under the condition of 20mg/L solid-to-liquid ratio, filtering after the reaction is finished, washing with deionized water until the filtrate is neutral, and drying at 50 deg.C for 12 hr.
5. The method according to claim 1, wherein the bleaching treatment in the step (3) is carried out by: in the following steps of 1: 20mg/L of solid-to-liquid ratio, using 20% of H2O2Heating the solution at 75 deg.C for 2h, filtering, and removingWashing with water for 4-5 times, washing with ethanol for 5-6 times, and vacuum drying at 60 deg.C for 12 hr.
6. The method according to claim 1, wherein the step (3) is performed by sieving through 80 to 200 mesh.
7. The method according to claim 1, wherein the mass of the bagasse cellulose BC relative to the PLA in the step (4) is 10-50%; the amount of PLA-GMA as a purified graft product is 10-30% relative to PLA.
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