Reactive toughened and reinforced high-crystallization-rate P34HB 3D printing wire and preparation method thereof

Abstract

The invention belongs to the field of new materials, and discloses a preparation method of a reactive toughened and reinforced high-crystallization-rate P34HB 3D printing wire rod, which comprises the following steps: step 1, uniformly mixing dried P34HB resin with a reactive toughening agent, a nucleating agent, a chain extender and an antioxidant to obtain a premix; 2, melting, extruding and granulating the premix; 3, the particles obtained in the step 2 are subjected to wire drawing and crystallization; the reactive toughening agent is a vinyl terpolymer containing an epoxy functional group; the nucleating agent is a hydrazide compound; the chain extender is a styrene-acrylate copolymer containing a plurality of epoxy functional groups. According to the preparation method, a reactive flexibilizer and a chemical chain extender are introduced, the brittleness problem of P34HB with the low 4HB content is solved by utilizing in-situ chemical reaction, and meanwhile, the processing problem is solved by matching with a specific nucleating agent and a process window. Meanwhile, the invention further provides the P34HB 3D printing wire rod prepared on the basis of the preparation method.

Description

Technical Field

[0001] This invention relates to the field of new materials, and in particular to a reactive, toughened, and enhanced high-crystallization-rate P34HB 3D printing filament and its preparation method. Background Technology

[0002] Poly(3-hydroxybutyrate)-co-4-hydroxybutyrate (P34HB) is a polyhydroxy fatty acid ester (PHA) synthesized by microbial fermentation. Its properties vary with the content of 4-hydroxybutyrate (4HB). When the 4HB content is low (e.g., around 5%), the material exhibits high hardness and modulus, but also extremely high brittleness (elongation at break is typically below 10%), making it very difficult to use directly in 3D printing filaments that require flexibility.

[0003] Applying P34HB (especially the low 4HB content specification) to the field of FDM 3D printing faces three major challenges:

[0004] 1. Severe brittleness: P34HB with low 4HB content has almost no toughness, and the wires made from it are extremely easy to break under the pressure of the wire feeding gears of the FDM printer.

[0005] 2. Slow crystallization leads to processing difficulties: Although low 4HB content crystallizes slightly faster than high 4HB content, its crystallization rate is still slower compared to general-purpose plastics such as PP and PE. In wire drawing production, the surface of the wire tends to become sticky after passing through the water tank, leading to tangling during winding.

[0006] 3. Low melt strength: P34HB has a flexible molecular chain and insufficient melt tension, which makes it prone to sagging during extrusion, resulting in inaccurate control of the wire diameter.

[0007] Existing technologies typically employ physical blending (such as incorporating PBAT) to toughen P34HB. However, physical blends exhibit weak interfacial bonding, resulting in limited toughening effects and a tendency for phase separation (delamination) in the already brittle P34HB material. Therefore, developing a modification technique that can significantly improve the toughness and processing performance of P34HB with low 4HB content is of great significance. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing a reactive toughening and enhanced high crystallization rate P34HB 3D printing filament. This method solves the brittleness problem of low 4HB content P34HB by introducing reactive toughening agents and chemical chain extenders and utilizing in-situ chemical reactions. At the same time, it solves processing problems by combining specific nucleating agents and process windows.

[0009] In addition, the present invention also provides P34HB 3D printing filament prepared based on this preparation method.

[0010] The technical solution of this invention is as follows:

[0011] A method for preparing a reactive, toughened, and enhanced high-crystallization-rate P34HB 3D printing filament, characterized by comprising the following steps:

[0012] Step 1: Mix the dried P34HB resin with reactive toughening agent, nucleating agent, chain extender and antioxidant evenly to obtain a premix;

[0013] Step 2: Melt extrusion granulation of the premix;

[0014] Step 3: The particles obtained in Step 2 are drawn into fibers and crystallized;

[0015] The reactive toughening agent is a vinyl terpolymer containing epoxy functional groups;

[0016] The nucleating agent is an acylhydrazine compound;

[0017] The chain extender is a styrene-acrylate copolymer containing multiple epoxy functional groups.

[0018] In the above preparation method, the reactive toughening agent is an ethylene-methyl acrylate-glycidyl methacrylate terpolymer; the nucleating agent is TMC-300; the chain extender is KL-E4370; and the antioxidant is a hindered phenolic antioxidant.

[0019] The basic principle of toughening modification in this invention is as follows: In the modified P34HB system, KL-E4370 epoxy chain extender, EMA-GMA toughening agent, and TMC-300 nucleating agent significantly improve the FDM 3D printing adaptability of the material through multi-dimensional synergy of chemical reaction, crystallization kinetics, and macroscopic physical properties. During melt blending, the epoxy groups of the multifunctional epoxy chain extender KL-E4370 and EMA-GMA react with the P34HB end groups (carboxyl and hydroxyl groups): KL-E4370 induces the matrix to form a long-chain branched structure, thereby greatly improving the melt strength, while EMA-GMA is anchored in the P34HB matrix and branched network through chemical cross-linking to achieve in-situ compatibilization, significantly strengthening the interfacial bonding force between the two phases and maximizing the toughening effect, effectively solving the problem of brittle fracture of the printing filament at the filament feed gear under stress. Furthermore, although the introduction of long-chain branched structures and the elastomeric phase exacerbated molecular chain entanglement and further slowed down the chain segment movement of P34HB, the highly efficient nucleating agent TMC-300 provided a large number of heterogeneous nucleation sites, forcibly inducing and accelerating the arrangement and crystallization of polymer chains in the complex network topology, forming a crucial kinetic compensation. Ultimately, the three components achieved complementary advantages in macroscopic printing performance: the high melt strength provided by KL-E4370 suppressed extrusion drooling and bridging collapse; the rapid crystallization promoted by TMC-300 ensured the rapid solidification of the extruded melt and the dimensional stability (anti-warping) of the printed parts; and the high toughness provided by EMA-GMA not only ensured the smooth winding of the filament but also comprehensively improved the interlayer bonding and overall impact resistance of the final printed parts.

[0020] In the above preparation method, the weight percentage of each raw material is as follows:

[0021] P34HB matrix resin: 88.2%~95.7%;

[0022] Reactive toughening agent: 2.5%~10%;

[0023] Nucleating agent: 0.5%~1.5%;

[0024] Chain extender: 0.1%~1.0%;

[0025] Antioxidant: 0.1%~0.5%.

[0026] In the above preparation method, step 2 is carried out using a twin-screw extruder, and the temperature of each zone of the twin-screw extruder is set as follows: 120℃, 165℃, 165℃, 168℃, 168℃, 168℃, 168℃, 168℃.

[0027] In the above preparation method, step 2 is carried out using a single-screw extruder;

[0028] Step 2 specifically involves: adding the granulated particles from step 2 into a single-screw extruder, and obtaining FDM printing wire through melt extrusion, constant temperature water bath cooling and crystallization, laser diameter measurement, and traction winding.

[0029] The temperature of the constant temperature water bath is 40℃-45℃;

[0030] The wire diameter is monitored in real time by a laser diameter gauge, and the control range of the wire diameter is 1.75mm ± 0.05mm.

[0031] In the above preparation method, the content of 4-hydroxybutyrate in the P34HB matrix resin is 4~5wt%.

[0032] Meanwhile, this invention also discloses a P34HB 3D printing filament, which is prepared using any of the methods described above.

[0033] This application has at least the following beneficial effects:

[0034] To address the issues of brittleness and warping during printing in P34HB materials with low 4HB content (around 5%), this invention specifically selects ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA) as a toughening agent. The in-situ reaction of its epoxy groups with the P34HB end groups achieves compatibility toughening. A chain extender is used to construct a long-branched structure to improve melt strength. Simultaneously, a hydrazide-based nucleating agent is used to promote rapid crystallization at a specific water temperature. The resulting wire exhibits excellent toughness (unnotched impact strength reaches 19.6 kJ / m). 2 The wire diameter is uniform, which solves the technical problems of easy breakage and tangling of traditional P34HB wire. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating the preparation process of the P34HB 3D printing filament of the present invention;

[0036] Figure 2A A photograph of the filament material obtained in Example 1 of the present invention;

[0037] Figure 2B This is an enlarged photograph of the filament material obtained in Example 1 of the present invention;

[0038] Figure 3 A magnified photograph of the filament obtained as Comparative Example 3 of the present invention;

[0039] Figure 4 A photograph of the printing material obtained in Embodiment 1 of the present invention;

[0040] Figure 5 A photograph of the printing material obtained in Embodiment 2 of the present invention;

[0041] Figure 6A photograph of the printing material obtained in Embodiment 3 of the present invention;

[0042] Figure 7 A photograph of the printing material obtained in Example 4 of the present invention;

[0043] Figure 8 A photograph of the printing material obtained in Comparative Example 1 of the present invention;

[0044] Figure 9 A photograph of the printing material obtained in Comparative Example 2 of the present invention;

[0045] Figure 10 This is a photograph of the printing material obtained in Comparative Example 3 of the present invention. Detailed Implementation

[0046] The present invention will now be clearly and completely described in conjunction with embodiments thereof. It should be noted that, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0047] The raw materials used in the embodiments of this invention are as follows:

[0048] P34HB resin: 4HB molar content is 5%, weight average molecular weight is 300,000 (indicating high hardness and high brittleness);

[0049] Reactive toughening agent: Arkema Ax8900 (EMA-GMA);

[0050] Nucleating agent: TMC-300 (Shanxi Chemical Research Institute, acylhydrazine nucleating agent);

[0051] Chain extender 1: KL-E4370 (Shanxi Chemical Research Institute);

[0052] Chain extender 2: Polycarboimide (IPDI-PCD, Shanghai Puzhan Industrial Co., Ltd.), its chemical formula is:

[0053]

[0054] Antioxidant: Lrganox 1010.

[0055] Example 1

[0056] A reactive, toughened, and enhanced high-crystallization-rate P34HB 3D printing filament, the preparation process of which is described in reference [reference needed]. Figure 1 The formula is as follows (by weight percentage):

[0057] P34HB resin (4HB=5%): 93.2%;

[0058] Reactive toughening agent (Ax8900): 5%;

[0059] Nucleating agent (TMC-300): 1%;

[0060] Chain extender 1 (KL-E4370): 0.5%;

[0061] Antioxidant (Irganox 1010): 0.3%;

[0062] Preparation steps:

[0063] P34HB resin was vacuum dried at 80°C for 4 hours.

[0064] The raw materials are mixed evenly using a high-speed mixer.

[0065] Twin-screw reactive extrusion, temperature settings: 120℃, 165℃, 165℃, 168℃, 168℃, 168℃, 168℃, 168℃ (die head). During this process, EMA-GMA undergoes an in-situ grafting reaction with the brittle P34HB matrix.

[0066] Single-screw wire drawing, die temperature 160℃, wire enters 40℃ constant temperature water bath.

[0067] Laser diameter measurement and traction winding.

[0068] Example 2

[0069] The formula is largely the same as in Example 1, except that the formula is adjusted to: 91.5% P34HB (4HB=5%), 7% reactive toughening agent, 0.9% nucleating agent, 0.5% chain extender, and 0.1% antioxidant.

[0070] Example 3

[0071] The formula is largely the same as in Example 1, except that the formula is adjusted to: P34HB (4HB=5%) 88.2%, reactive toughening agent 10%, nucleating agent 1%, chain extender 0.5%, and antioxidant 0.3%.

[0072] Example 4

[0073] The formula is largely the same as in Example 1, except that the formula is adjusted to: P34HB (4HB=5%) 95.7%, reactive toughening agent 2.5%, nucleating agent 1%, chain extender 0.5%, and antioxidant 0.3%.

[0074] Comparative Example 1

[0075] The method is largely the same as in Example 1, except that the nucleating agent is replaced by cyanuric acid in equal weight.

[0076] Comparative Example 2

[0077] The method is largely the same as in Example 1, except that the nucleating agent is replaced by nano-silica at the same weight.

[0078] Comparative Example 3

[0079] It is generally the same as Example 1, except that chain extender 1 is replaced by chain extender 2 in equal weight.

[0080] Comparative Example 4

[0081] The method is largely the same as in Example 1, except that the amount of reactive toughening agent (Ax8900) is adjusted to 5.5% and the amount of chain extender (KL-E4370) is adjusted to 0wt%.

[0082] Experimental phenomena: low melt strength, resulting in drooping wire when drawn.

[0083] Comparative Example 5

[0084] The formula is largely the same as Example 1, except that it does not contain nucleating agent TMC-300 and the water bath temperature is 25°C.

[0085] Experimental phenomena: Due to the delayed crystallization of 5% 4HB P34HB, the wire surface is sticky and sticks together when wound up.

[0086] Performance testing

[0087] The wires prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were printed into standard test strips and their performance was tested. The results are shown in Table 1.

[0088] The test items include: wire drawing process stability, tensile strength, bending strength, cantilever beam unnotched impact strength, and wire flexibility;

[0089] The testing methods for each test item are as follows:

[0090] Fiber drawing stability: The fiber drawing stability of the samples was characterized by measuring the melt strength of the material at 160 °C using a Goteford tensile rheometer. After the polymer melt was extruded through a capillary die, it was uniaxially drawn downwards by a pair of counter-rotating traction rollers below. During this drawing process, a high-precision mechanical sensor connected to the traction rollers recorded the drawing force and drawing speed applied to the melt filament in real time. The maximum tensile force measured before fracture was characterized as the melt strength of the sample.

[0091] Tensile strength: The tensile properties of FDM 3D printed Type IV B dumbbell-shaped specimens were tested on a universal testing machine according to ASTM D638 standard. After conditioning in a standard environment (23±2°C, 50±5% RH) for 40 h, the specimens were vertically clamped and stretched axially at a constant rate of 5 mm / min until fracture. The maximum breaking load was recorded and divided by the initial narrow cross-sectional area of ​​the specimen to calculate the tensile strength. The average value of 5 parallel specimens in each group was taken.

[0092] Bending strength: Rectangular specimens measuring 80 mm × 10 mm × 4 mm were tested using a universal testing machine via the three-point bending method, according to ISO 178 standard. The lower support span was set to 16 times the specimen thickness (64 mm). A vertical load was applied at the center of the specimen span at a constant rate of 2 mm / min until the specimen fractured or the deformation reached the specified deflection. The average value of five parallel specimens tested in each group was taken.

[0093] Unnotched impact strength of cantilever beam: Following ISO 180 standard, the impact performance of a rectangular unnotched printed specimen with dimensions of 80 mm × 8 mm × 4 mm was determined using a cantilever beam impact testing machine. The lower end of the specimen was vertically and firmly clamped in a bench vise. A 5.5 J pendulum was used, calibrated in dry run, and released from a fixed height to break the cantilever end of the specimen in one swing. The absorbed energy at fracture was read and divided by the cross-sectional area of ​​the specimen to obtain the unnotched impact strength (kJ / m²). The arithmetic mean of 5 parallel specimens in each group of tests was taken.

[0094] Wire flexibility: At room temperature, the wire is knotted and gradually tightened. Observe and record whether brittle fracture occurs at the knots, or whether stress whitening, microcracks, or other damage appears on the surface. The wire's ability to form a tight knot without significant structural damage indicates excellent flexibility.

[0095] The test results can be found in Table 1.

[0096] Table 1 Test Results

[0097] Test Project Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Stability of the drawing process Optimal Figure 2A and Figure 2B ) excellent excellent excellent excellent good Good (filament roughness, Figure 3 ) Tensile strength (MPa) 22 19.5 18.7 24.3 18.8 18.1 19 Bending strength (MPa) 43.8 45 47.6 44 40 41 37 Unnotched impact strength of a cantilever beam (kJ / m²) 13.7 14.6 16.2 19.6 12.0 11.5 10.8 Wire flexibility Flexibility Flexibility Flexibility Flexibility Flexibility Flexibility Flexibility Printed photo number Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

[0098] Results analysis:

[0099] 1. As can be seen from Examples 1 to 4, for P34HB material with high hardness and high brittleness of 5% 4HB content, the brittleness problem of low 4HB content P34HB can be solved by introducing reactive toughening agents and chemical chain extenders and utilizing in-situ chemical reactions. At the same time, processing difficulties can be solved by using specific nucleating agents and process windows.

[0100] 2. As can be seen from Comparative Examples 1 and 2, toughening agents containing epoxy functional groups of vinyl terpolymers are more effective than other types of toughening agents; as can be seen from Comparative Examples 3 and 4, the use of chain extenders containing multiple epoxy functional groups is particularly important for improving product performance.

[0101] 3. As can be seen from Comparative Example 5, nucleating agents are also a very important factor in improving the crystallization properties of materials.

[0102] 4. Through Figure 2A , Figure 2B , Figure 3 It is evident that the filament obtained by the formulation of this invention has a smooth surface, while the filament obtained by Comparative Example 3 has a rough surface. We believe that this is related to the interfacial compatibility. Although PCD chain extender has a certain chain-extending effect, it is not as easy as polyepoxy chain extender to participate in interfacial reaction and in-situ compatibility at the same time, resulting in a larger size of the dispersed phase EMA-GMA, which in turn leads to a rough filament.

[0103] 5. Same Figures 4 to 10 As can be seen, the printed parts obtained by this invention have a smooth and flat surface without warping; the printed parts obtained by Comparative Examples 1-3 exhibit a certain degree of warping. This is because cyanuric acid (Comparative Example 1) and nano-silica (Comparative Example 2) have high specific surface areas, providing a large number of heterogeneous nucleation sites, thus significantly accelerating the polymer crystallization process. For processing methods like FDM molding, which involve significant temperature gradients, excessively rapid crystallization causes the material to undergo crystallization-induced shrinkage earlier during the cooling stage, exacerbating uneven shrinkage between layers and regions, thereby increasing residual stress levels and ultimately leading to increased warping. Under the same nucleating agent conditions, PCD chain extender (Comparative Example 3) is more likely to cause warping of the printed parts than epoxy chain extender, mainly because the two have different mechanisms for regulating the polymer molecular structure and rheological behavior. Multifunctional epoxy chain extenders can react with both the terminal carboxyl and hydroxyl groups of polyester simultaneously, making it easier to form long branched structures and significantly improving melt viscosity, elasticity, and entanglement density, thereby enhancing the resistance of the printed melt to cooling shrinkage stress. In contrast, PCD chain extenders are more inclined to react with carboxyl groups, mainly exhibiting linear chain extension and hydrolysis stabilization, with relatively limited improvement on melt strength and branched structure. Therefore, they are more likely to undergo uneven shrinkage and warping during cooling and crystallization.

[0104] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a reactive, toughened, and enhanced high-crystallization-rate P34HB 3D printing filament, characterized in that, Includes the following steps: Step 1: Mix the dried P34HB resin with reactive toughening agent, nucleating agent, chain extender and antioxidant evenly to obtain a premix; Step 2: Melt extrusion granulation of the premix; Step 3: The particles obtained in Step 2 are drawn into fibers and crystallized; The reactive toughening agent is a vinyl terpolymer containing epoxy functional groups; The nucleating agent is an acylhydrazine compound; The chain extender is a styrene-acrylate copolymer containing multiple epoxy functional groups.

2. The preparation method according to claim 1, characterized in that, The reactive toughening agent is an ethylene-methyl acrylate-glycidyl methacrylate terpolymer; the nucleating agent is TMC-300; the chain extender is KL-E4370; and the antioxidant is a hindered phenolic antioxidant.

3. The preparation method according to claim 1, characterized in that, The weight percentage of each raw material is as follows: P34HB matrix resin: 88.2%~95.7%; Reactive toughening agent: 2.5%~10%; Nucleating agent: 0.5%~1.5%; Chain extender: 0.1%~1.0%; Antioxidant: 0.1%~0.5%.

4. The preparation method according to claim 1, characterized in that, Step 2 is performed using a twin-screw extruder, with the temperature settings for each zone of the twin-screw extruder as follows: 120℃, 165℃, 165℃, 168℃, 168℃, 168℃, 168℃, 168℃.

5. The preparation method according to claim 1, characterized in that, Step 2 is performed using a single-screw extruder; Step 2 specifically involves: adding the granulated particles from step 2 into a single-screw extruder, and obtaining FDM printing wire through melt extrusion, constant temperature water bath cooling and crystallization, laser diameter measurement, and traction winding. The temperature of the constant temperature water bath is 40℃-45℃; The wire diameter is monitored in real time by a laser diameter gauge, and the control range of the wire diameter is 1.75mm ± 0.05mm.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The content of 4-hydroxybutyrate in the P34HB matrix resin is 4~5wt%.

7. A P34HB 3D printing filament, characterized in that, It is prepared by the method described in any one of claims 1 to 5.

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