CN116003766B - A high melt strength modified polyhydroxy fatty acid ester material and its preparation and application - Google Patents
A high melt strength modified polyhydroxy fatty acid ester material and its preparation and applicationInfo
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- CN116003766B CN116003766B CN202111230174.3A CN202111230174A CN116003766B CN 116003766 B CN116003766 B CN 116003766B CN 202111230174 A CN202111230174 A CN 202111230174A CN 116003766 B CN116003766 B CN 116003766B
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Abstract
The invention provides a modified polyhydroxyalkanoate material which comprises polyhydroxyalkanoate segments and polyurethane segments, wherein the polyurethane segments are obtained by reacting a fluxing agent with polyhydroxyalkanoate. The melt strength of PHA can be effectively improved and the mechanical property of PHA can be enhanced through continuous reactive extrusion. The invention adopts isocyanate fluxing agent and high-performance catalyst to carry out fluxing modification on polyhydroxyalkanoate, which can crosslink polymer chain segments, effectively reduce the crystallinity of modified PHA and obviously increase the mechanical property elongation and fracture energy of modified PHA.
Description
Technical Field
The invention belongs to the field of biological materials, and particularly relates to a high-melt-strength modified polyhydroxyalkanoate material, and a preparation method and application thereof.
Background
The Polyhydroxyalkanoate (PHA) material is used as a bio-based degradable material prepared by microbial fermentation, and has wide application prospect in the field of degradable materials. The preparation method has the advantages of adjustable molecular structure and performance due to the mode of microbial fermentation, and is expected to realize low-cost production by optimizing an industrial amplification technology. In addition, PHA is composed of aliphatic polyester and is easy to be decomposed by microorganisms after being used, so PHA is an excellent bio-based degradable material with controllable performance, hopeful low cost and easy microbial decomposition .(Brandi H et al.Degradation and applications of polyhydroxyalkanoates.Can.J.Microbiol,1995,41:143-153;Ong S Y et al.Degradation of polyhydroxyalkanoate(PHA):a review.2017;Bugnicourt E et al.Polyhydroxyalkanoate(PHA):Review of synthesis,characteristics,processing and potential applications in packaging.2014).
Compared with the traditional polyester material, the PHA material is different in preparation mode, and has the defects that the melt strength of the prepared polymer is usually low, the processing performance of the produced film is poor, the mechanical property is usually weak, the crystallinity is low, the crystallization period is long, secondary crystallization is easy and the like because the chemical structure is different and the processes of high-temperature melt chain extension and the like of the traditional polyester in a reaction kettle are avoided, and ester bond breakage is generated due to high temperature and screw shearing in the processing and molding process, so that thermomechanical degradation occurs, and the mechanical property (Wang S et al.Modification and potential application of short-chain-length polyhydroxyalkanoate(SCL-PHA).Polymers2016;8:273). of the molding material is further influenced, so that the PHA material usually has the defects of poor mechanical property, narrow processing window, low melt strength and poor processing performance.
The isocyanate is used as a high-activity hydroxyl-terminated agent, so that the hydroxyl-terminated content of PHA can be effectively reduced. The material stability is improved, for example, in Chinese patent CN108377821A, isocyanate is adopted as a blocking agent of a PHA-based multilayer barrier film material, the hydroxyl content of the self terminal is reduced, and the probability of hydrolysis reaction caused by capturing water molecules in the environment by weakening groups is reduced. The stability and the water-blocking performance of the material are improved. However, in this patent, only isocyanate is added as a blocking agent, improving the stability thereof, but not the overall mechanical properties and processability thereof.
In chinese patent CN104245839a, a Thermoplastic Polyurethane (TPU) of adipic acid reacted with diphenylmethane diisocyanate (MDI) is used to modify PHA, and this patent adopts a way of physically blending PHA with TPU to improve its processability, so that impact strength and flexural modulus are greatly improved. However, after modification by this method, the elongation at break of PHA is still low, only about 3%, and it is difficult to achieve film-grade application.
Disclosure of Invention
In order to solve the above problems, the present invention adopts a continuous reaction extrusion method to modify PHA (polyhydroxyalkanoate). Under the action of high-efficiency catalyst, adding polybasic isocyanate to make melt enhancement modification of PHA, and making the hydroxyl-terminated groups of different PHA molecules implement urethanization connection, and introducing chemical structure with polyurethane-like bond between PHA molecules so as to greatly raise its mechanical extensibility and melt strength, and finally raise the processing property and mechanical property of PHA material.
The invention aims to provide a modified polyhydroxyalkanoate material which comprises a polyhydroxyalkanoate segment and a polyurethane segment, wherein the polyurethane segment is obtained by reacting a fluxing agent and polyhydroxyalkanoate, and the fluxing agent is a reactive functional auxiliary agent capable of increasing melt strength. The content of the polyurethane chain segment in the modified polyhydroxyalkanoate material is 0.05-25%, preferably 0.5-10% in terms of mass percent.
Specifically, the solvent is selected from at least one of binary or polybasic isocyanate compounds, preferably Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene Diisocyanate (HDI) and dicyclohexylmethane-4, 4' -diisocyanate (HMDI), and more preferably Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI) and Hexamethylene Diisocyanate (HDI).
The second purpose of the invention is to provide a preparation method of the modified polyhydroxyalkanoate material, which comprises the step of reacting components comprising polyhydroxyalkanoate and a fluxing agent to obtain the modified polyhydroxyalkanoate material. Preferably, the preparation method specifically comprises the following steps:
step 1, pre-mixing components including a fluxing agent and a catalyst;
And 2, carrying out a melting reaction on the premix obtained in the step 1 and the polyhydroxyalkanoate to obtain the modified polyhydroxyalkanoate material, wherein the premix obtained in the step 1 and the polyhydroxyalkanoate can be fed together or respectively.
In the above preparation method, the solvent is selected from polyisocyanate compounds, preferably at least one selected from Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene Diisocyanate (HDI) and dicyclohexylmethane-4, 4' -diisocyanate (HMDI), more preferably one selected from Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI) and Hexamethylene Diisocyanate (HDI);
The catalyst is at least one of tertiary amine and organic tin catalysts, preferably at least one of triethylamine, triethylenediamine, dimethylaniline, stannous octoate, dibutyl tin dilaurate, stannous chloride and dibutyl tin dioctoate, more preferably at least one of triethylamine, triethylenediamine, stannous chloride, stannous octoate and dibutyl tin dioctoate;
The polyhydroxyalkanoate is selected from homo-or copolymer of hydroxy fatty acid with 4-18 carbon atoms, and has a structure shown in a formula (I):
wherein R is alkyl with carbon chain length of 1-15,
Preferably, the polyhydroxyalkanoate is at least one selected from poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-co-4-hydroxybutyrate), poly (3-hydroxybutyrate-co-3-hydroxyvalerate) and poly (3-hydroxybutyrate-co-3-hydroxyhexanoate);
The polyhydroxyalkanoate has a weight average molecular weight M w of 50000g/mol or more, preferably M w of 100000g/mol or more.
In the preparation method, the amount of the fluxing agent is 0.01-5 parts, preferably 0.1-2 parts, and the amount of the catalyst is 0.001-5 parts, preferably 0.01-1 part, based on 100 parts by mass of the polyhydroxyalkanoate.
The preparation method comprises the following steps:
The components including the flux and the catalyst may be premixed by mixing means and equipment commonly used in the art, such as a kneader or a high-speed mixer.
The preparation method comprises the following step 2:
The melting reaction can be carried out by adopting a melting reaction process, process conditions and equipment which are commonly used in the field of polymer material processing, and can be carried out by adopting a screw melting extrusion mode, preferably adopting a twin-screw extruder, wherein the melting reaction can be carried out in the same direction or in different directions, preferably, the melting reaction temperature is 50-300 ℃, preferably 100-200 ℃, and the screw rotating speed of the melting reaction is 5-1200 rpm, preferably 20-400 rpm.
The twin-screw extruder used in the present invention includes, but is not limited to, micro 27 twin-screw extruder manufactured by Leistritz, germany, which has a function of switching the same direction/different direction, polyLab, euroLab type same-direction twin-screw extruder manufactured by Thermo FISHER SCIENTIFIC, U.S. A., ZSK 30 type same-direction parallel twin-screw extruder manufactured by Coperion, germany, etc.
The invention further aims to provide a high-melt-strength modified polyhydroxyalkanoate material, which is prepared by the preparation method, wherein the melt strength of the modified polyhydroxyalkanoate material is more than 5cN. By adopting the preparation method, after the Polyhydroxyalkanoate (PHA) is subjected to melt enhancement and modification, the PHA melt strength is improved to 5-30 cN, the stretching speed is improved to 50-150 mm/s, the breaking elongation of the PHA is improved by 15 times and can be improved to 300%, and the breaking energy of the PHA is improved by more than 15 times and can be improved to 6.72J/m 3.
The fourth object of the present invention is to apply the above-mentioned high melt strength modified polyhydroxyalkanoate material to a biodegradable film material.
According to the invention, the continuous reaction extrusion method is adopted to lead isocyanate fluxing agent and PHA molecular chain segments to generate reactions such as PHA intermolecular chain extension, crosslinking and the like under the action of a catalyst, so that PHA is subjected to in-situ modification to form a polyurethane structure, the mechanical property (such as elongation at break) and melt strength of the PHA are greatly enhanced, the elongation at break of the PHA is enhanced by 15 times to 300%, the energy at break of the PHA is enhanced by more than 15 times to 6.72J/m 3, the melt strength and mechanical property of the PHA are remarkably enhanced, and the parameters such as the melt strength, the elongation at break, the energy at break and the like of the PHA are remarkably enhanced, so that the processability of the PHA is effectively improved.
Compared with the prior art, the invention has the following beneficial effects:
1. The invention adopts isocyanate fluxing agent and high-performance catalyst to carry out fluxing modification on polyhydroxyalkanoate, and the introduction of the catalyst can greatly enhance the fluxing effect of PHA, so that PHA chain is extended and crosslinked. Thereby remarkably reducing the melt index, improving the melt strength and leading the melt to have better processing performance;
2. After the isocyanate type flux is adopted to carry out the melting modification on the polyhydroxyalkanoate, the mechanical property of the modified polyhydroxyalkanoate material is obviously improved, and the breaking elongation and breaking energy of the modified polyhydroxyalkanoate material are obviously improved;
3. the preparation method provided by the invention is simple and feasible, can be used for continuous production, is environment-friendly, and is easy to realize industrialization.
Drawings
FIG. 1 is a DSC cooling profile of blank examples and modified PHA particles in examples 1-5;
FIG. 2 is a graph of the total reflection infrared curve of unmodified PHA versus HDI modified PHA particles of varying amounts added;
FIG. 3 melt strength of modified PHA particles of examples 1-5;
FIG. 4 XRD with different amounts of HDI modified PHA particles added;
FIG. 5 elongation at break of the injection molded bars of blank example, examples 1-5 and comparative examples 1-2.
Detailed Description
The present invention is described in detail below with reference to specific embodiments, and it should be noted that the following embodiments are only for further description of the present invention and should not be construed as limiting the scope of the present invention, and some insubstantial modifications and adjustments of the present invention by those skilled in the art from the present disclosure are still within the scope of the present invention.
The test instruments and test conditions used in the examples are as follows:
The melt index (MFR) was measured according to ISO 1133 using a Lloyd Davenport MFI-10/230 melt index apparatus, the barrel temperature was 150℃and the mass load was 2.16kg, the die diameter was 2.095mm, the length was 8mm, the preheating time was 4 minutes, the sample was automatically cut at set intervals, the average value was obtained 5 times, and the measurement result was expressed in grams per 10 minutes (g/10 minutes).
Thermal performance analysis (DSC) the test was performed on a Discovery series Differential Scanning Calorimeter (DSC) manufactured by TA Instruments, process software TA Instruments Trios version 3.1.5, equipped with REFRIGERATED COOLING SYSTEM mechanical refrigeration accessories. The test atmosphere is 50mL/min of nitrogen, and the sample amount required by the test is 5-10 mg. The test procedure is as follows, the temperature is stabilized at 40 ℃, then 10 ℃/min is raised to 220 ℃ and kept constant for 1min to remove the heat history, then 10 ℃/min is lowered to-50 ℃ and kept constant for 1min, and then 10 ℃/min is raised to 220 ℃. Recording the cooling process and the second heating process to study the thermal performance of the sample. The DSC test can be used for directly obtaining the crystallization temperature ("T c"), the melting temperature ("T m"), the glass transition ("T g"), the enthalpy change ("H") and other information of the sample by software.
Total reflection Infrared test (ATR-FTIR) A total reflection infrared spectroscopic test was performed by the front FTIR (Waltham, mass., USA) manufactured by Perkinelmer, U.S.A., equipped with a universal ATR kit.
Melt strength testing measurements were made using a Rosand RH7/10 capillary rheometer. The diameter of the cylinder hole is 15mm, and the diameter of the oral membrane is 1mm. The test temperature was 155℃with a draw initiation rate of 2m/min, a draw end rate of 100m/min and a time of 5min.
Plastic tensile testing-according to ISO 527-2, using an Instron model 3344 materials tester, processing software Bluehill version 2.31. The film was cut into Type5A Type in ISO 527-2 standard in parallel to the stretching direction (MD) and perpendicular to the stretching direction (CD), and left for 24 hours (h) in a constant temperature and humidity oven (temperature 23 ℃ C., relative humidity 50%) Bluepard BPS-100CB, shanghai-Heng Sci Co., ltd. At the time of testing, the initial fixture spacing was 50mm, the test stretching rate was 10mm/min, and each sample was tested at least 5 times, and the average value was taken.
Wide angle X-ray diffraction (XRD) test XRD test was performed on an XDS-2000 instrument from Scintag. Proper amount of scattering q=1.5-40 nm -1, and wide-angle X-ray diffraction (WAXRD) analysis is performed at room temperature.
The raw materials and sources used in the examples are as follows:
The Hexamethylene Diisocyanate (HDI) used in the present invention was selected from the carbofuran technology, and the polyhydroxyalkanoate (PHA, weight average molecular weight (M w) was 300000 g/mol) was selected from the Tianjin Green Co. Stannous chloride (SnCl 2) is selected from the group of microphone agents. Diphenylmethane diisocyanate (MDI) is selected from Shanghai macelin Biochemical technologies Co.
[ Blank example 1]
In blank 1, PHA was melt extruded using a PolyLab HAAKE TM Rheomx OS PTW16 co-rotating twin screw extruder (screw diameter 16mm, L/D=40) from Thermo Fisher technologies, USA. 100 parts of PHA powder is added into a double-screw extruder according to parts by weight, the extruder is 11 sections from a feeding port to a die, the number is 1-11, and the 1 st section only plays a role of feeding and is not heated. The temperatures of the sections 2 to 11 of the extruder are respectively as follows: 120 ℃,140 ℃,150 ℃,150 ℃,160 ℃, the screw speed was set at 50rpm at 160 ℃,160 ℃ and 140 ℃. The PHA material is fed to the 1 st section of the double-screw extruder by a weightless feeder, wherein the feeding speed is 0.6kg/h. After stable operation, the pressure of twin-screw extrusion is 10-20 bar, and the torque is about 82%. The extruder is provided with two circular outlets with the diameter of 4mm on a die, the sample strip is extruded from the die, then is cut into cylindrical particles with the length of about 5mm by a granulator after passing through a water bath cooling tank, and is vacuumized for 4 hours (h) in a vacuum drying oven at the temperature of 70 ℃, and then is collected and packaged for standby.
Examples 1-5 preparation of high melt strength polyhydroxyalkanoates
In example 1, various amounts of fluxing agent HDI were added. PHA was modified by a PolyLab HAAKE TM Rheomex OS PTW16 co-rotating twin screw extruder (screw diameter 16mm, L/D=40) from Thermo Fisher technologies, USA.
According to the parts by weight, 0.03 part of catalyst stannous chloride, different amounts of HDI and 100 parts of PHA powder are premixed by a stirrer and then injected into a double-screw extruder for melt reaction. Wherein the addition amounts of HDI were 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts and 1 part, respectively.
The twin-screw extruder has 11 sections from the feeding port to the die, with the number of 1-11, wherein the 1 st section only plays a role of feeding and is not heated. The temperatures of the sections 2 to 11 of the extruder are respectively as follows: 120 ℃, 140 ℃, 150 ℃, 160 ℃ and 140 ℃, and the screw rotation speed is set at 50rpm. The PHA mixture is fed to the 1 st section of the double-screw extruder by a weightless feeder, wherein the feeding speed is 0.6kg/h. After stable operation, the pressure of twin-screw extrusion is 10-30 bar, and the torque is about 77% -82%. The extruder is provided with two circular outlets with the diameter of 4mm on a die, the sample strip is extruded from the die, then is cut into cylindrical particles with the length of about 5mm by a granulator after passing through a water bath cooling tank, and is vacuumized for 4 hours (h) in a vacuum drying oven at the temperature of 70 ℃, and then is collected and packaged for standby.
Comparative example 1 modified polyhydroxyalkanoate to which only HDI was added
Comparative example 1 examined the reactive extrusion modification of PHA by the addition of HDI alone. PHA was modified by a PolyLab HAAKE TM Rheomex OS PTW16 co-rotating twin screw extruder (screw diameter 16mm, L/D=40) from Thermo Fisher technologies, USA. 100 parts of PHA powder and 0.8 part of HDI are premixed according to parts by weight, and are subjected to melt reaction extrusion by a double-screw extruder to obtain modified PHA particles, wherein the main reaction temperature of the extruder is 160 ℃, and the screw rotation speed is 50rpm. Other conditions are controlled to be the same as in example 1, and after the operation is stable, the pressure of twin-screw extrusion is 10-30 bar, and the torque is about 65%. The extruder is provided with two circular outlets with the diameter of 4mm on a die, the sample strip is extruded from the die, then is cut into cylindrical particles with the length of about 5mm by a granulator through a water bath cooling tank, and is vacuumized for 4 hours in a vacuum drying oven at 70 ℃, and then is collected and packaged for standby.
Comparative example 2 ADR chain-extended modified polyhydroxyalkanoate
Comparative example 2 examined the case of chain extension of PHA with an epoxy chain extender ADR4468 (Basf, molecular weight 7250, epoxy number: 9), and PHA was extruded with a PolyLab HAAKE TM Rheomx OS PTW16 co-rotating twin screw extruder (screw diameter 16mm, L/D=40) from Thermo Fisher technologies, USA. 100 parts of PHA powder and 0.8 part of ADR are premixed according to parts by weight, and are extruded through a double screw extruder in a melting reaction mode, so that modified PHA is obtained. The extruder main body reaction temperature was 160℃and the screw speed was 50rpm. Other conditions are controlled to be the same as in example 1, and after the operation is stable, the pressure of twin-screw extrusion is 10-30 bar, and the torque is about 70%. The extruder is provided with two circular outlets with the diameter of 4mm on a die, the sample strip is extruded from the die, then is cut into cylindrical particles with the length of about 5mm by a granulator through a water bath cooling tank, and is vacuumized for 4 hours in a vacuum drying oven at 70 ℃, and then is collected and packaged for standby.
[ Comparative example 3] MDI chain-extended modified polyhydroxyalkanoate
Comparative example 3 was a modified PHA by melt-up modification with MDI, and was modified with a PolyLab HAAKE TM rheomix OS PTW16 co-rotating twin screw extruder (screw diameter 16mm, l/d=40) from Thermo Fisher technologies, usa. 100 parts of PHA powder and 0.8 part of MDI are premixed according to parts by weight, and the modified PHA particles are obtained through twin-screw melt reaction extrusion, wherein the reaction temperature of an extruder main body is 160 ℃, and the screw rotating speed is 50rpm. Other conditions are controlled to be the same as in example 1, and after the operation is stable, the pressure of twin-screw extrusion is 10-30 bar, and the torque is about 58%. The extruder is provided with two circular outlets with the diameter of 4mm on a die, the sample strip is extruded from the die, then is cut into cylindrical particles with the length of about 5mm by a granulator through a water bath cooling tank, and is vacuumized for 4 hours in a vacuum drying oven at 70 ℃, and then is collected and packaged for standby.
Example 6 melt index test
The modified PHA particles prepared in examples 1-5, blank 1 and comparative examples 1-3 were subjected to melt index testing, the measurement method is as described above, and the melt indexes of the PHA particles prepared in examples 1-5 and comparative examples 1-3 were tested at a temperature of 155 ℃ and a mass of 2.16kg, and the measured melt indexes are shown in Table 1.
Table 1.155 ℃ and 2.16kg, melt indices of examples 1 to 5, blank 1 and comparative examples 1 to 3
Comparing blank 1 with examples 1-5 where different amounts of HDI and catalyst were added, it was found that after HDI modification, the melt index (MFR) of the resulting modified PHA was significantly reduced as the amount of HDI added during twin-screw modification was gradually increased, when 0.2% of HDI was added, the MFR was significantly reduced from 2.8g/10min to 0.78g/10min, when 0.8% of HDI was added, the MFR was further reduced to 0.24g/10min, when HDI was further added to 1%, the MFR was slightly increased, indicating that the HDI modification had the best melting effect on PHA when the amount of HDI added reached 0.8%, and the resulting MFR was the smallest. Further addition of HDI may cause transesterification reaction in excess, resulting in an increase in MFR and deterioration in melt strength. Similarly, after MDI modification, the melt index was also lowered.
In contrast, in comparative example 1, the MFR was 3.2g/10min after only 0.8% of HDI was added, and the MFR was not significantly decreased. This suggests that the addition of HDI alone for capping does not achieve the goal of increasing PHA melt strength. The introduction of the catalyst can greatly enhance the melting effect of the PHA, and a polyurethane-like structure is formed between PHA chains, so that the PHA chains are subjected to chain extension and crosslinking, and the melt strength of the PHA chains is improved.
In comparative example 2, ADR is coupled with hydroxyl/carboxyl of polyester through epoxy functional group to generate polyester structure, thereby achieving chain extension effect. After adding 0.8% ADR to comparative example 2, the MFR was slightly reduced to 2.2g/10min. The MFR was still higher compared to examples 1-5 where HDI was added with the catalyst. This suggests that significant melting enhancement was not achieved by chain extension with ADR added to PHA. Therefore, the melt enhancement effect of the PHA in the invention can be verified by side surface, mainly comes from the reaction of HDI and PHA chain under the action of catalyst, isocyanate forms a urethane structure through condensation of isocyanate radical and hydroxyl, molecular chain segments have polyurethane structures, obvious chain extension and crosslinking occur between chains, the elongation rate of PHA material is improved, and the melt strength of PHA material is improved.
Example 7 Differential Scanning Calorimeter (DSC) test
The values of the second melting temperature (T m) melting enthalpy (. DELTA.H2 m), the glass transition temperature (T g) and the recrystallization enthalpy (. DELTA.H2 c) of examples 1-5 and blank 1 were measured by Differential Scanning Calorimetry (DSC) according to the above-mentioned procedure and are shown in Table 2.
TABLE 2 DSC results of examples 1-5, blank example 1
The temperature profile of the high melt strength polyhydroxyalkanoate at various temperatures and rotational speeds is shown in FIG. 1, where the peak crystallization of PHA gradually decreases and is lowest at the addition of 0.8% HDI as the amount of HDI increases. The cooling crystallization enthalpy (. DELTA.H c) was reduced from 22.35J/g to 10.97J/g after the addition of 0.8% HDI. The enthalpy of crystallization increased to 19.26J/g after further addition of HDI. This suggests that HDI causes chain extension and crosslinking of PHA segments under the action of a catalyst, thereby significantly degrading the crystalline structure.
Example 8 Total reflection Infrared test
The particles of examples 1-5 and blank 1 were tested by total reflection infrared spectroscopy using the front FTIR (Waltham, MA, USA) from Perkinelmer, U.S.A., as described above. As shown in FIG. 2, it can be seen that the characteristic peaks at 1059cm -1、1279cm-1 and 1376cm -1, which represent the C-O and-OH stretching vibration peaks, respectively, decrease with increasing HDI addition. This suggests that the introduction of HDI effectively reduces the number of terminal hydroxyl groups.
Melt Strength test (example 9)
Melt strength measurements were performed in a capillary rheometer as described above for examples 1-5, and the results are shown in FIG. 3. It should be noted that unmodified PHA particles cannot be wound in a capillary rheometer due to too low a melt strength, which is nearly zero and undetectable. It can be seen that as the amount of HDI added was increased from 0.2% to 0.8%, the melt strength of the PHA was significantly enhanced, and the melt strength of the modified PHA was increased from 8cN and a stretching speed of 139mm/s to 23cN and a stretching speed of 137mm/s. When further increased to 1%, its melt strength slightly decreased. The conclusion of melt strength and the mutual validation of melt index in example 6 demonstrate that modification of HDI can significantly increase the melt strength of PHA under the action of the catalyst.
Crystallization Properties example 10
The pellets of examples 1 to 5 and blank 1 were injection molded in a HAAKE MiniLab mini-injection molding machine. The injection molding temperature is 155 ℃, the grinding head temperature is 40 ℃, and the injection molding pressure is 400bar. Cooling time was 30s. The XRD test results of the injection molded bars obtained in the above manner are shown in FIG. 3, and after modification of the HDI, the crystal peak intensity of the modified PHA is significantly reduced, and the minimum value is obtained at the HDI addition amount of 0.8%, which is also verified by DSC results in example 7, and it is demonstrated that the introduction of the HDI can significantly chain-extend or crosslink the PHA chain under the action of the catalyst, so that the mechanical property is improved.
[ Example 11] mechanical Property test
All the particles in examples 1 to 5, blank 1 and comparative examples 1 to 3 were injection molded in a HAAKE MiniLab mini-injection molding machine. The plastic bars obtained by injection molding were subjected to mechanical property testing as described above, and the resulting elongation at break was as shown in fig. 4.
As shown in fig. four, it is evident that the elongation at break of the PHA modified spline was initially maintained stable as the addition amount of HDI was increased, and the elongation at break began to increase from 20% to 55% when the addition amount of HDI was 0.6%, and increased significantly to 300% when the addition amount was 0.8%, which is 15 times the elongation of unmodified PHA. And as the HDI amount was further increased to 1%, the elongation was slightly decreased. In addition, the modified PHA bars of comparative examples 1 and 2 did not significantly increase the elongation at break compared to unmodified PHA, only 3% and 10%. This further suggests that the significant increase in elongation at break at this time is caused by the introduction of HDI to allow reaction between PHA chains, increasing entanglement between PHA molecular chains. This is also consistent with the conclusions in examples 7-10. And after HDI modification, the breaking energy of the modified PHA spline is obviously improved from unmodified 0.37J/m 3 to 6.72J/m 3 after 0.8% of HDI modification. But the mechanical property of PHA can be greatly improved by adding MDI, and the elongation rate is improved to 169%.
Mechanical tests prove that under the action of the catalyst, after HDI modification by reaction extrusion, the mechanical elongation and fracture energy of the modified PHA are obviously improved.
[ Comparative example 4]
According to chinese patent CN104245839a, modified PHA materials are obtained by modifying PHA with Thermoplastic Polyurethane (TPU) of adipic acid reacted with MDI (see example 14), the processability, impact strength, flexural modulus are improved. However, after the modified PHA obtained by the method is modified, the fracture elongation of the modified PHA is still low and is only about 10%, and the application of a film grade is difficult to achieve. Therefore, the fracture elongation of the PHA modified by the polyurethane physical blending method is still lower and is far lower than the fracture elongation of the modified PHA material provided by the invention to achieve the effect of nearly 300%.
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| CN101450989A (en) * | 2008-12-19 | 2009-06-10 | 东华大学 | Method for synthesizing poly hydroxy fatty acid ester block copolymers in situ |
| CN113150515A (en) * | 2020-12-25 | 2021-07-23 | 青岛科技大学 | Degradable poly (4-hydroxybutyrate) low-temperature 3D printing wire and preparation method thereof |
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