PLA / PCL composite material and preparation and application thereof

Abstract

The application discloses a PLA / PCL composite material and preparation and application thereof, and the method comprises the following steps: uniformly mixing PLA and PCL, then using a balanced three-screw dynamic extruder to melt blend under vibration, and sequentially subjecting the prepared blend to cold pressing and air cooling to obtain the PLA / PCL composite material. The PLA / PCL composite material is prepared based on the dispersion effect of a vibration force field, under the same filling amount of PCL mass ratio, the vibration force field makes PCL obtain better dispersion effect in PLA, and then makes the PCL phase obtain a larger surface area, so that the compatibility between PLA and the PCL phase is enhanced; under the stretching effect of calendering, the molecular chain of PLA becomes more regular, the crystallinity is improved, the prepared PLA / PCL composite material has great improvement in elongation at break and tensile strength, the applicable scenarios are more abundant, and the application market of the full biodegradable material is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer material preparation, and particularly relates to a PLA / PCL composite material and preparation and application thereof. BACKGROUND

[0002] With the development of the plastic industry and the large-scale application of plastic products, great burden has been brought to the natural ecological environment. In recent years, the white pollution has been increasingly intensified, and the harm of petroleum-based plastics has begun to be increasingly apparent. Therefore, the fully biodegradable plastics have emerged as the times require. The fully biodegradable plastics have the advantages of environmental friendliness and good biocompatibility, and the products thereof can be degraded by microorganisms in the natural environment in a short time, and thus are regarded as potential substitutes for petroleum-based plastics.

[0003] Polylactic acid (PLA) is a kind of fully biodegradable plastic with excellent comprehensive mechanical properties, relatively wide raw material sources and relatively universal application. However, the poor toughness of PLA limits its more extensive application prospect. As a kind of fully biodegradable elastomer plastic, polycaprolactone (PCL) is an ideal filler for toughening PLA, which can ensure the fully biodegradable performance of the composite material and improve the toughness of PLA. On the other hand, the compatibility of PLA and PCL is poor and the cost of PCL is high. Therefore, a relatively high PCL filling amount (30-50%) is often required in the ordinary extrusion processing mode for melt blending extrusion to achieve a relatively considerable toughness improvement. How to effectively toughen PLA with a low PCL content is a problem to be solved in the field of biodegradable materials at present. SUMMARY

[0004] In order to overcome the defects and deficiencies of the prior art, the primary purpose of the present application is to provide a preparation method of a PLA / PCL composite material.

[0005] Another purpose of the present application is to provide a PLA / PCL composite material prepared by the above method.

[0006] Still another purpose of the present application is to provide the application of the above PLA / PCL composite material.

[0007] The purposes of the present application are achieved by the following technical solutions.

[0008] The preparation method of the PLA / PCL composite material comprises the following steps: uniformly mixing PLA and PCL, then using a balanced three-screw dynamic extruder to perform melt blending under vibration, and sequentially subjecting the prepared blend to cold pressing and air cooling, so that the PLA / PCL composite material is obtained.

[0009] Preferably, the balanced three-screw dynamic extruder is described in Chinese patent CN105856530A.

[0010] Preferably, the mixing ratio of the PLA and PCL is 75-95% of PLA and 5-25% of PCL by weight percentage.

[0011] Preferably, the mixing is performed by a mixer, and the mixing time is 3-5 minutes, and the mixer speed is 800-1000 revolutions per minute.

[0012] Preferably, the vibration condition is specifically an amplitude of 0.4-1 mm and a vibration frequency of 3-6 Hz.

[0013] Preferably, the temperature of the melt blending is 100-200℃, and the screw speed is 25-35 revolutions per minute.

[0014] Preferably, when melt blending and extruding, the mixing part of the balanced three-screw dynamic extruder is divided into 9 zones, and the temperatures of zone 1 to zone 9 are set as 100℃-150℃-190℃-190℃-190℃-190℃-190℃-150℃-100℃ in sequence, the temperature of the feeding zone is set as 190℃, the material is fed from both ends of zone 1 and zone 9 to the middle for extrusion, the material moves to zone 5 and is connected to the feeding zone, and after extrusion from zone 5, the material enters the calender for cold pressing processing through the feeding zone.

[0015] Preferably, the gap between the rollers of the calender is 1.0±0.3 mm, and the temperature of the cold pressing processing is 23-25℃, and the linear speed is 0.8-2 m / min.

[0016] Preferably, the diameter of the melt after extrusion through the feeding zone is 20±0.5 mm; and the obtained PLA / PCL composite material is a sheet with a thickness of 1.0±0.3 mm.

[0017] A PLA / PCL composite material prepared by the above preparation method.

[0018] Application of the above PLA / PCL composite material.

[0019] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0020] (1) The PLA / PCL composite material is prepared based on the dispersion effect of the vibration force field, and under the same filling amount of PCL mass ratio, the vibration force field makes PCL obtain better dispersion effect in PLA and thus makes the PCL phase obtain a larger surface area, thereby enhancing the compatibility between the PLA and PCL phases. Since the present application adopts a pure physical compatibilization method, the prepared sheet has the characteristics of environmental friendliness.

[0021] (2) The PLA / PCL melt after melt blending and extrusion is in a cylindrical shape, and after the cold pressing process, the material becomes a sheet with a uniform cross section. During the calendering process, the cross-sectional shape changes greatly, and a stretching flow field is generated in the melt. Under the action of the stretching flow field, the dispersed PCL droplets change from spherical to ellipsoidal and are fixed in the continuous PLA phase, forming a special in-situ fiber-forming morphology, greatly increasing the interfacial bonding force, and thus the mechanical properties of the prepared PLA / PCL composite material are obviously improved.

[0022] (3) Under the stretching action of the calendering machine, the molecular chain of PLA becomes more regular, and the crystallinity is improved. The improvement of crystallinity has a positive promoting effect on the tensile strength and modulus of the composite material.

[0023] (4) The preparation process and formula of the present application are simple, and the PLA / PCL composite material prepared has a great improvement in elongation at break and tensile strength, so it can be applied to more scenarios, increasing the application market of fully biodegradable materials. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The cross-sectional morphology of the PLA / PCL composite sheet prepared in Examples 1-6, wherein (a), (b), (c), (d), (e), and (f) correspond to Examples 1, 2, 3, 4, 5, and 6, respectively.

[0025] Figure 2 The DSC first heating curve of the PLA / PCL composite sheet prepared in Examples 1-6. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below in conjunction with examples, but the embodiments of the present application are not limited thereto. The raw materials involved in the present application can be directly purchased from the market, and for the process parameters not specifically mentioned, the conventional technology can be referred to.

[0027] The PLA used in the examples is 4032D from the United States Nature Works Company, and the PCL is 6800 from the Perstorp Company in Switzerland.

[0028] The calendering machine used in the examples is purchased from Guangzhou Pudong Experimental Analysis Instrument Co., Ltd., and the model is MPSM-32 / 35; the balanced three-screw dynamic extruder is described in Chinese patent CN105856530A.

[0029] Example 1

[0030] The present embodiment provides a PLA / PCL composite material and a preparation method thereof.

[0031] The dry PLA 90%, PCL 10% by weight is weighed and mixed in a high-speed mixer for 180 s at a speed of 1000 rpm. Then, the PLA and PCL are melt blended in a balanced three-screw dynamic extruder under vibration conditions. The vibration conditions are specifically an amplitude of 0.4 mm and a vibration frequency of 3 Hz. The balanced three-screw dynamic extruder has a mixing section divided into 9 zones, and the temperatures of the 1st zone to the 9th zone are set to 100℃-150℃-190℃-190℃-190℃-190℃-190℃-150℃-100℃, respectively. The temperature of the feeding zone is set to 190℃, and the screw speed is 25 rpm. The material is fed from both ends of the 1st zone and the 9th zone to the middle of the extruder. The material moves to the 5th zone and then to the feeding zone. After being extruded from the 5th zone, the material enters a calender for cold pressing. The extruded melt has a diameter of 20 mm. The gap between the rollers of the calender is set to 0.8 mm, the temperature is set to 23℃, and the linear speed is set to 1 m / min. After air cooling and sampling, the PLA / PCL composite material is obtained. The obtained PLA / PCL composite material is a sheet with a thickness of 0.8±0.1 mm.

[0032] Example 2

[0033] This example serves as a comparative example and provides a PLA / PCL composite material and a preparation method thereof without applying vibration.

[0034] The dry PLA 90%, PCL 10% by weight is weighed and mixed in a high-speed mixer for 180 s at a speed of 1000 rpm. Then, the PLA and PCL are melt blended in a balanced three-screw dynamic extruder under vibration conditions. The vibration conditions are specifically an amplitude of 0.4 mm and a vibration frequency of 3 Hz. The balanced three-screw dynamic extruder has a mixing section divided into 9 zones, and the temperatures of the 1st zone to the 9th zone are set to 100℃-150℃-190℃-190℃-190℃-190℃-190℃-150℃-100℃, respectively. The temperature of the feeding zone is set to 190℃, and the screw speed is 25 rpm. The material is fed from both ends of the 1st zone and the 9th zone to the middle of the extruder. The material moves to the 5th zone and then to the feeding zone. After being extruded from the 5th zone, the material enters a calender for cold pressing. The extruded melt has a diameter of 20 mm. The gap between the rollers of the calender is set to 0.8 mm, the temperature is set to 23℃, and the linear speed is set to 1 m / min. After air cooling and sampling, the PLA / PCL composite material is obtained. The obtained PLA / PCL composite material is a sheet with a thickness of 0.8±0.1 mm.

[0035] Example 3

[0036] This example provides a PLA / PCL composite material and a preparation method thereof.

[0037] The dry PLA 90%, PCL 10% is weighed according to the weight ratio, and then mixed in a high-speed mixer for 180 s at a speed of 1000 rpm. Then, the PLA and PCL are melt-blended in a balanced three-screw dynamic extruder under vibration conditions. The vibration conditions are as follows: an amplitude of 1 mm and a vibration frequency of 3 Hz. The mixing part of the balanced three-screw dynamic extruder is divided into 9 zones, and the temperatures of the 1st zone to the 9th zone are set to 100℃-150℃-190℃-190℃-190℃-190℃-190℃-150℃-100℃, respectively. The temperature of the feeding zone is set to 190℃, and the screw speed is 25 rpm. The material is fed from both ends of the 1st zone and the 9th zone to the middle. The material moves to the 5th zone and then to the feeding zone. After being extruded from the 5th zone, the material enters a calender for cold pressing. The extruded melt has a diameter of 20 mm. The gap between the rollers of the calender is set to 1.2 mm, the temperature is set to 23℃, and the linear speed is set to 1 m / min. After air cooling and sampling, the PLA / PCL composite material is obtained. The obtained PLA / PCL composite material is a sheet with a thickness of 1.2±0.1 mm.

[0038] Example 4

[0039] The present embodiment provides a PLA / PCL composite material and a preparation method thereof.

[0040] The dry PLA 75%, PCL 25% is weighed according to the weight ratio, and then mixed in a high-speed mixer for 180 s at a speed of 1000 rpm. Then, the PLA and PCL are melt-blended in a balanced three-screw dynamic extruder under vibration conditions. The vibration conditions are as follows: an amplitude of 1 mm and a vibration frequency of 3 Hz. The mixing part of the balanced three-screw dynamic extruder is divided into 9 zones, and the temperatures of the 1st zone to the 9th zone are set to 100℃-150℃-190℃-190℃-190℃-190℃-190℃-150℃-100℃, respectively. The temperature of the feeding zone is set to 190℃, and the screw speed is 25 rpm. The material is fed from both ends of the 1st zone and the 9th zone to the middle. The material moves to the 5th zone and then to the feeding zone. After being extruded from the 5th zone, the material enters a calender for cold pressing. The extruded melt has a diameter of 20 mm. The gap between the rollers of the calender is set to 1.2 mm, the temperature is set to 23℃, and the linear speed is set to 1 m / min. After air cooling and sampling, the PLA / PCL composite material is obtained. The obtained PLA / PCL composite material is a sheet with a thickness of 1.2±0.1 mm.

[0041] Example 5

[0042] The present embodiment provides a PLA / PCL composite material and a preparation method thereof.

[0043] The dry PLA 95%, PCL 5% are weighed according to the weight ratio, and then mixed in a high-speed mixer for 180 s at a speed of 1000 rpm. Then, the PLA and PCL are melt blended in a balanced three-screw dynamic extruder under vibration conditions. The vibration conditions are as follows: an amplitude of 1 mm and a vibration frequency of 3 Hz. The mixing part of the balanced three-screw dynamic extruder is divided into 9 zones, and the temperatures of the 1st zone to the 9th zone are set to 100℃-150℃-190℃-190℃-190℃-190℃-190℃-150℃-100℃, respectively. The temperature of the feeding zone is set to 190℃, and the screw speed is 25 rpm. The material is fed from both ends of the 1st zone and the 9th zone to the middle. The material moves to the 5th zone and then to the feeding zone. After being extruded from the 5th zone, the material is collected through the feeding zone and then cooled by air. The obtained PLA / PCL composite material is a sheet with a thickness of 1.2±0.1 mm.

[0044] Example 6

[0045] This example is a comparative example, which provides a PLA / PCL composite material and a preparation method thereof without cold pressing.

[0046] The dry PLA 90%, PCL 10% are weighed according to the weight ratio, and then mixed in a high-speed mixer for 180 s at a speed of 1000 rpm. Then, the PLA and PCL are melt blended in a balanced three-screw dynamic extruder under vibration conditions. The vibration conditions are as follows: an amplitude of 1 mm and a vibration frequency of 3 Hz. The mixing part of the balanced three-screw dynamic extruder is divided into 9 zones, and the temperatures of the 1st zone to the 9th zone are set to 100℃-150℃-190℃-190℃-190℃-190℃-190℃-150℃-100℃, respectively. The temperature of the feeding zone is set to 190℃, and the screw speed is 25 rpm. The material is fed from both ends of the 1st zone and the 9th zone to the middle. The material moves to the 5th zone and then to the feeding zone. After being extruded from the 5th zone, the material is collected through the feeding zone and then cooled by air. The obtained PLA / PCL composite material is a sheet with a thickness of 1.2±0.1 mm.

[0047] The PLA / PCL composite sheets obtained in Examples 1-6 are cut into standard samples using a standard cutting tool. The tensile strength and elongation at break of the PLA / PCL composite sheets obtained in Examples 1-6 are tested according to GB / T 1040-2006. The test results are shown in Table 1.

[0048] The PLA / PCL composite sheets obtained in Examples 1-6 were subjected to crystallinity test using a differential scanning calorimeter (DSC) Netzsch DSC204 produced by Netzsch Company of Germany, and the test results are shown in Table 1. Figure 2

[0049] Table 1: Mechanical properties of PLA / PCL composite sheets of various examples

[0050] PLA / PCL composite sheet Tensile strength / MPa Elongation at break / % Example 1 81.5 70.5 Example 2 62.3 62.5 Example 3 64.9 359.0 Example 4 51.1 452.0 Example 5 66.3 208.5 Example 6 50.7 11.8

[0051] Figure 1 Cross-sectional morphologies of PLA / PCL composite sheets prepared in Examples 1-6, wherein (a), (b), (c), (d), (e), (f) correspond to Examples 1, 2, 3, 4, 5, and 6, respectively. Figure 1 Compared with (b), the PLA / PCL composite material prepared in the present application based on the dispersion effect of vibration force field has better dispersion effect of PCL in PLA under the same filling amount of PCL mass ratio, and thus the PCL phase has larger surface area, thereby enhancing the compatibility between PLA and PCL phases. Figure 1 Compared with (f), the PCL droplets after dispersion change from spherical shape to ellipsoidal shape under the action of the stretching flow field of the calendering process and are fixed in the continuous PLA phase, forming a special in-situ fiber-forming morphology, which greatly increases the interfacial bonding force, thereby significantly improving the mechanical properties of the prepared PLA / PCL composite material.

[0052] Figure 2 DSC first heating curves of PLA / PCL composite sheets prepared in Examples 1-6, under the stretching action of the calendering machine, the molecular chains of PLA become more regular, and the crystallinity is improved, and the improvement of crystallinity has a positive promoting effect on the tensile strength and elongation at break of the composite material.

[0053] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.​

Claims

1. A method for preparing a PLA / PCL composite material, characterized in that, Includes the following steps: PLA and PCL are mixed evenly, and then melt-blended under vibration conditions using a balanced three-screw dynamic extruder. The resulting blend is then subjected to cold pressing and air cooling to obtain the PLA / PCL composite material. The vibration conditions are specifically an amplitude of 0.4–1 mm and a frequency of 3–6 Hz. The gap between the rolls of the calender is 1.0±0.3mm, the temperature of the cold pressing process is 23~25℃, and the linear speed is 0.8~2m / min; The mixing ratio of PLA and PCL is 75-95% PLA and 5-25% PCL by weight percentage.

2. The method for preparing PLA / PCL composite material according to claim 1, characterized in that, The mixing is carried out using a mixer, with a mixing time of 3 to 5 minutes and a mixer speed of 800 to 1000 revolutions per minute.

3. The method for preparing PLA / PCL composite material according to claim 1, characterized in that, The melt blending temperature is 100–200°C, and the screw speed is 25–35 rpm.

4. The method for preparing the PLA / PCL composite material according to claim 1, characterized in that, During the melt blending extrusion, the mixing section of the balanced three-screw dynamic extruder is divided into 9 zones. The temperatures of zones 1 to 9 are set sequentially as follows: 100℃-150℃-190℃-190℃-190℃-190℃-150℃-100℃. The temperature of the feeding zone is set to 190℃. The material is fed from both ends of zones 1 and 9 and extruded towards the middle. The material moves to zone 5 and then to the feeding zone. After being extruded from zone 5, the material enters the calender through the feeding zone for cold pressing.

5. The method for preparing PLA / PCL composite material according to claim 1, characterized in that, The melt of the melt blend is 20±0.5mm in diameter after being extruded through the feeding zone; the resulting PLA / PCL composite material is a sheet with a thickness of 1.0±0.3mm.

6. A PLA / PCL composite material, characterized in that, It is prepared by the method for preparing PLA / PCL composite material according to any one of claims 1 to 5.

7. The application of the PLA / PCL composite material according to claim 6 in fully biodegradable materials.

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