CN111675888A - A kind of high-strength and high-toughness polylactic acid-based composite material and preparation method thereof - Google Patents

Abstract

The invention relates to a preparation method of a polylactic acid-based composite material with high tensile strength, high impact strength and high ductility, and belongs to the field of polymer composite materials. The invention provides a high-strength and high-toughness polylactic acid-based composite material. The composite material is prepared by melt blending of polylactic acid and phenolic resin, and the phenolic resin accounts for 1-20 wt% of the mass of the composite material; wherein, the phenolic resin The weight average molecular weight of ≥ 20,000. The present invention adopts the simple method of adding phenolic resin to PLA, and obtains a PLA-based composite material with high tensile strength, high modulus, high ductility and high impact strength, which plays the role of toughening and strengthening PLA.

Description

A kind of high-strength and high-toughness polylactic acid-based composite material and preparation method thereof

technical field

The invention relates to a preparation method of a polylactic acid-based composite material with high tensile strength, high impact strength and high ductility, and belongs to the field of polymer composite materials.

Background technique

Polylactic acid (PLA) is a biodegradable, biocompatible and renewable thermoplastic with excellent processing properties and broad industrial prospects. Strictly speaking, polylactic acid is a family that includes left-handed polylactic acid (PLLA), right-handed polylactic acid (PDLA), and a mixture of two different optically active polylactic acids. But generally speaking, because biofermentation mainly produces L-lactic acid, currently only PLLA is renewable and cheap, and only PLLA has been commercialized on a large scale. Therefore, unless otherwise specified, the polylactic acid (PLA) referred to in the art is PLLA or PLLA containing a small amount of d-lactic acid units. PLLA has high tensile strength and tensile modulus, but due to its low entanglement density and high characteristic ratio of PLLA molecular chains, its impact strength is extremely low and its ductility is extremely low. Therefore, in some scenarios for structural materials or film blowing, PLA materials need to be further toughened.

The toughening method of PLA is usually copolymerized or blended with flexible polymers, among which the typical representatives are PEO/PEG, PPO, PCL, etc. In addition, special processing methods are also a large category of modification methods, of which the typical one is oscillating shearing. , this method promotes PLA to form special structures such as shish-kebab structure to enhance toughness; of course, there are some inorganic modification methods, such as adding modified graphene, modified nano-silica and so on. Among the above series of PLA toughening methods, under standard test methods, except for some special processing methods, which have obvious toughening effect without excessive loss of tensile strength, other methods are generally difficult to take into account the balance of rigidity and toughness. It should also be noted here that special processing methods also have a series of problems. For example, compared with traditional extrusion and injection molding, the production cycle is long, and it is difficult to continuously produce. Therefore, these methods need to be improved in industrial application.

Polyphenoloxy resin or phenoxy resin is a kind of epoxy resin with ultra-high molecular weight (weight average molecular weight 15,000-1,000,000), different from general liquid epoxy resin, phenoxy resin is solid at room temperature. Phenoxy resins are generally linear chain structures, and the main industrial application products are ultra-high molecular weight epoxy resins formed by the polymerization of bisphenol A and epichlorohydrin; their main application scenarios are pipeline coatings, prepregs, structural adhesives , PCB ink and other coatings and adhesives.

At present, there is no relevant report on the modification of PLA with phenolic resin or ultra-high molecular weight epoxy resin at home and abroad.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a high-strength and high-toughness PLA-based composite material modified by phenolic resin, the comprehensive mechanical properties of which are greatly improved compared with ordinary PLA materials.

Technical scheme of the present invention:

The first technical problem to be solved by the present invention is to provide a high-strength and high-toughness polylactic acid-based composite material. The composite material is prepared by melt blending polylactic acid and phenolic resin, and the phenolic resin accounts for 1% of the quality of the composite material. ~20wt%; wherein, the weight-average molecular weight of the phenolic resin is greater than or equal to 20,000.

Further, the phenolic resin accounts for 4-20 wt % of the mass of the composite material; preferably, it is 7-20 wt %.

Further, the phenolic resin satisfies that its repeating unit contains at least one main chain ether bond and at least one hydroxyl side group.

The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned high-strength and high-toughness polylactic acid-based composite material. A composite material; wherein, the phenolic resin accounts for 1-20 wt% of the mass of the composite material, and the weight-average molecular weight of the phenolic resin is ≥20,000.

Further, the preparation method is as follows: uniformly mixing polylactic acid and phenolic resin (PKHH) to obtain a premix, and then melt-blending the premix at 170-190° C. to obtain a polylactic acid-based composite material.

Further, in the above method, the polylactic acid and the phenolic resin are blended at a high speed of 250-350 r/min (300 r/min) for 1-10 min (preferably 5 min) to obtain a premix.

Further, in the above method, the premix is extruded and pelletized in an extruder at 170-190° C., and then dried to obtain a blended pellet, that is, a polylactic acid-based composite material.

The third technical problem to be solved by the present invention is to provide a polylactic acid reinforcing and toughening agent, which is a phenolic resin with a weight average molecular weight of ≥20,000.

Further, the added amount of the reinforcing and toughening agent is 1-20wt% of the mass of the polylactic acid; preferably 4-20wt%; more preferably 7-20wt%.

The fourth technical problem to be solved by the present invention is to provide the use of a phenolic resin, which can be used to strengthen and toughen polylactic acid, and the weight-average molecular weight of the phenolic resin is ≥20,000.

Further, when the phenolic resin is used to strengthen and toughen the polylactic acid, its usage amount is 1-20wt% of the mass of the polylactic acid; preferably 4-20wt%; more preferably 7-20wt%.

Beneficial effects of the present invention:

The invention adopts the simple method of adding phenolic resin to PLA, and obtains a PLA-based composite material with high tensile strength, high modulus, high ductility and high impact strength, which plays the role of toughening and strengthening PLA; The pendant hydroxyl groups of the phenolic resin can form hydrogen bonds with the carbonyl groups on PLA, and can also undergo transesterification with PLA, which can greatly improve the compatibility with PLA. After adding 10% phenolic resin to PLA, the tensile strength of the obtained PLA-based composite material can reach 56.8MPa, which is only 9.7% lower than that of pure PLA; the Young's modulus can reach 2.6GPa, which is comparable to that of pure PLA. Compared with PLA, it is only 6.9% lower; however, the elongation at break can reach 205.1%, which is 2872.5% higher than that of pure PLA; the impact strength can reach 7.4kJ/m ² , which is 138.7% higher than that of pure PLA.

Description of drawings

Figure 1.a is the infrared spectrum of pure PLA, pure phenolic resin and their mixture; Figure 1.b is the rheological time scan of each formula; Figure 1.c is the variation law of torque with time during the banburying process; As shown in Figure 1a, after PLA is blended with the phenolic resin, the phenolic hydroxyl groups of the phenolic resin will be red-shifted, which indicates that the intermolecular hydrogen bonds of the phenolic resin are diluted or an ester occurs between PLA and the phenolic resin. exchange reaction; further from Figure 1b, it can be seen that with the gradual increase of the content of phenolic resin, the decrease of storage modulus caused by the degradation of PLA molecular chain is gradually balanced by the grafting reaction of phenolic resin and PLA, and the curve law is shown as phenolic resin. The higher the content, the smaller the downward slope of the curve, and it can be reasonably determined to be the grafting caused by the transesterification reaction; in addition, it can be seen from the torque versus time curve during banburying (as shown in Figure 1c), which is marked by a dotted circle. The increase of torque at 1 is the stage of the reaction, which once again shows that the PLA and the phenolic resin have undergone a transesterification reaction.

Fig. 2a is a graph showing the variation of tensile strength and impact strength of samples with the content of phenolic resin in the embodiment, and Fig. 2b is a graph showing the variation of Young's modulus and elongation at break of the sample with the content of phenolic resin in the embodiment; It can be seen that when the content of phenolic resin is less than 4wt.%, there is basically no toughening effect; when the content is further increased and does not exceed 10wt.%, the comprehensive mechanical properties of the composite material are in the optimal region, that is, the material's The toughness is high and the strength is also high; when the content exceeds 20wt.%, the toughening effect is the same as that of the traditional toughening agent, the toughness is improved, and the tensile strength is decreased.

Fig. 3 is a scanning electron microscope image of some embodiments of the present invention; as can be seen from Fig. 3: as the content of phenolic resin increases, the degree of microphase separation from the matrix becomes more and more serious, and the dispersed phase particles become larger and larger. At a certain value (about 10wt.%), the phase separation is serious, which reduces the comprehensive mechanical properties of the material.

FIG. 4 is a physical diagram of each embodiment of the present invention after stretching; it can be seen from FIG. 4 that the ductility of the obtained sample of the present invention is very good, which is beneficial to the application of blown film.

Detailed ways

Phenoxy resin generally refers to an ultra-high molecular weight epoxy resin with a weight average molecular weight greater than 15,000, which is also called a phenolic resin or a polyphenolic resin; the phenolic resin in the present invention does not require its specific monomer structure. , it is only required that its repeating units contain at least one main chain ether bond and at least one hydroxyl side group. The key content of the present invention is that PLA contains the above-mentioned phenolic resin.

In the present invention, the phenolic resin can form a strong hydrogen bond with PLA or undergo a transesterification reaction to form a graft copolymer; the above two cases can increase the compatibility between the two; at the same time, it will form a relatively rigid Hard interface layer, so as to strengthen and toughen PLA at the same time, that is, to improve the comprehensive mechanical properties of PLA.

The embodiments of the present invention will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer. The resins or instruments used without specifying the manufacturer are conventional products that can be purchased from the market.

Example 1

1. Extrusion to obtain pure PLA pellets, which is the blank sample described below, and the formula is abbreviated as PLA in the chart.

3kg of PLA raw material was extruded and pelletized in an extruder at 170-190°C, and finally dried to obtain pellets.

2. Preparation of characterization samples and their characterization

1) Injection molding the pellets obtained in step 1 at 190° C. to obtain stretched national standard splines and national standard impact splines that automatically generate gaps. In 2006, its tensile properties were tested, and its impact strength was tested by JXUD5.5 pendulum impact tester and in accordance with the national standard GB/T1843-2008;

2) Banburying (190°C) to obtain a blend of PLA and phenolic resin with a ratio of 1:1, and recording the change spectrum of its torque with time; NICOLET 6700MAGNA infrared tester and TADHR-3 dynamic rheology tester for infrared characterization and time scanning;

3) The splines obtained by injection molding were subjected to liquid nitrogen embrittlement, and then the morphology of the cross-section of the samples was observed under a scanning electron microscope.

The mechanical properties of the composites tested by 5569 Instron universal testing machine and JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10 mm/min. As can be seen from Table 1, the tensile strength was 62.9 MPa, the elongation at break was 6.9%, the automatic Young's modulus was 2.9 GPa, and the impact strength was 3.2 kJ/m ² .

Table 1 shows the mechanical properties of pure PLA and PLA composites with different formulations.

Example 2

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using phenolic resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

3kg of PLA and 15g of phenolic resin (PKHH) with a weight-average molecular weight of 850,000 were added to a high-speed blender (rotating speed of 300r/min), and a premix was obtained after initial mixing for 5min, and then it was mixed at 170- The extruder at 190° C. was extruded into pellets, and finally dried to obtain blended pellets. The formula (0.5 wt. % phenolic resin) is abbreviated as PLA/0.5PKHH in the figures and tables.

2. Preparation of characterization samples and their characterization

1) Injection molding the pellets obtained in step 1 at 190° C. to obtain stretched national standard splines and national standard impact splines that automatically generate gaps. In 2006, its tensile properties were tested, and its impact strength was tested by JXUD5.5 pendulum impact tester and in accordance with the national standard GB/T1843-2008;

2) Press the blended sample into a film, and use the TA DHR-3 dynamic rheology tester to perform time scanning;

3) The splines obtained by injection molding were subjected to liquid nitrogen embrittlement, and then the morphology of the cross-section of the samples was observed under a scanning electron microscope.

The mechanical properties of the composite materials tested by 5569 Instron universal testing machine and JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10mm/min; it can be seen from Figure 2 and Table 1 that the tensile strength The strength is 63.7MPa, which has no obvious change compared with the blank sample; the elongation at break is 7.1%, which has no obvious change compared with the blank sample; the automatic Young's modulus is 2.9GPa, which has no obvious change compared with the blank sample; the impact strength is 3.1kJ/m ² , There was no significant change compared with the blank sample.

Example 3

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using phenolic resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

3kg of PLA and 30g of phenolic resin (PKHH) with a weight-average molecular weight of 850,000 were added to the high-speed blender, and a premix was obtained after initial mixing for 5 minutes, which was then subjected to an extruder at 170-190°C. Extrusion granulation, and finally drying to obtain blended granules, the formula (1 wt.% phenolic resin) is abbreviated as PLA/1PKHH in the chart.

2. Preparation of characterization samples and their characterization

1) Injection molding the pellets obtained in step 1 at 190° C. to obtain stretched national standard splines and national standard impact splines that automatically generate gaps. In 2006, its tensile properties were tested, and its impact strength was tested by JXUD5.5 pendulum impact tester and in accordance with the national standard GB/T1843-2008;

2) Press the blended sample into a film, and use the TA DHR-3 dynamic rheology tester to perform time scanning;

3) The splines obtained by injection molding were subjected to liquid nitrogen embrittlement, and then the morphology of the cross-section of the samples was observed under a scanning electron microscope.

The mechanical properties of the composites obtained by using the 5569 Instron universal testing machine and the JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10 mm/min. It can be seen from the chart that the tensile strength is 61.7MPa, which has no obvious change compared with the blank sample; the elongation at break is 15.2%, which is about twice as high as that of the blank sample; the automatic Young's modulus is 2.9GPa, which has no obvious change compared with the blank sample; impact The intensity is 3.3kJ/m ² , which has no obvious change compared with the blank sample.

Example 4

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using phenolic resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

3kg of PLA and 120g of phenolic resin (PKHH) with a weight-average molecular weight of 850,000 were added to the high-speed blender, and a premix was obtained after initial mixing for 5 minutes, which was then subjected to an extruder at 170-190°C. Extrusion granulation, and finally drying to obtain blended granules, the formula (4 wt.% phenolic resin) is abbreviated as PLA/4PKHH in the diagram.

2. Preparation of characterization samples and their characterization

1) Injection molding the pellets obtained in step 1 at 190° C. to obtain stretched national standard splines and national standard impact splines that automatically generate gaps. In 2006, its tensile properties were tested, and its impact strength was tested by JXUD5.5 pendulum impact tester and in accordance with the national standard GB/T1843-2008;

2) Press the blended sample into a film, and use the TA DHR-3 dynamic rheology tester to perform time scanning;

3) The splines obtained by injection molding were subjected to liquid nitrogen embrittlement, and then the morphology of the cross-section of the samples was observed under a scanning electron microscope.

The mechanical properties of the composites obtained by using the 5569 Instron universal testing machine and the JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10 mm/min. It can be seen from the chart that the tensile strength is 62.3MPa, which has no obvious change compared with the blank sample; the elongation at break is 18.1%, which is about 1.5 times higher than that of the blank sample; the automatic Young's modulus is 2.7GPa, which is 6.2% lower than that of the blank sample; The intensity is 3.2kJ/m ² , which has no obvious change compared with the blank sample.

Example 5

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using phenolic resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

3kg of PLA and 210g of phenolic resin (PKHH) with a weight-average molecular weight of 850,000 were added to a high-speed blender, and a premix was obtained after initial mixing for 5 minutes, which was then carried out in an extruder at 170-190°C. Extrusion granulation, and finally drying to obtain blended granules, the formula (7 wt.% phenolic resin) is abbreviated as PLA/7PKHH in the diagram.

2. Preparation of characterization samples and their characterization

1) Injection molding the pellets obtained in step 1 at 190° C. to obtain stretched national standard splines and national standard impact splines that automatically generate gaps. In 2006, its tensile properties were tested, and its impact strength was tested by JXUD5.5 pendulum impact tester and in accordance with the national standard GB/T1843-2008;

2) Press the blended sample into a film, and use the TA DHR-3 dynamic rheology tester to perform time scanning;

3) The splines obtained by injection molding were subjected to liquid nitrogen embrittlement, and then the morphology of the cross-section of the samples was observed under a scanning electron microscope.

The mechanical properties of the composites obtained by using the 5569 Instron universal testing machine and the JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10 mm/min. It can be seen from the chart that the tensile strength is 59.0MPa, which is about 6.3% lower than that of the blank sample; the elongation at break is 110.5%, which is about 15 times higher than that of the blank sample; the automatic Young's modulus is 2.7GPa, which is 6.2% lower than that of the blank sample; The impact strength is 5.8kJ/m ² , which is about 81.2% higher than that of the blank sample.

Example 6

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using phenolic resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

3kg of PLA and 300g of phenolic resin (PKHH) with a weight-average molecular weight of 850,000 were added to the high-speed blender, and a premix was obtained after initial mixing for 5 minutes, which was then subjected to an extruder at 170-190°C. Extrusion granulation, and finally drying to obtain blended granules, the formula (10 wt.% phenolic resin) is abbreviated as PLA/10PKHH in the chart.

2. Preparation of characterization samples and their characterization

1) Injection molding the pellets obtained in step 1 at 190° C. to obtain stretched national standard splines and national standard impact splines that automatically generate gaps. In 2006, its tensile properties were tested, and its impact strength was tested by JXUD5.5 pendulum impact tester and in accordance with the national standard GB/T1843-2008;

2) Press the blended sample into a film, and use the TA DHR-3 dynamic rheology tester to perform time scanning;

3) The splines obtained by injection molding were subjected to liquid nitrogen embrittlement, and then the morphology of the cross-section of the samples was observed under a scanning electron microscope.

The mechanical properties of the composites obtained by using the 5569 Instron universal testing machine and the JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10 mm/min. It can be seen from the chart that the tensile strength is 56.8MPa, which is about 9.6% lower than that of the blank sample; the elongation at break is 194.0%, which is about 27 times higher than that of the blank sample; the automatic Young's modulus is 2.6GPa, which is 10.3% lower than that of the blank sample; The impact strength is 7.4kJ/m ² , which is about 131.3% higher than that of the blank sample.

Example 7

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using phenolic resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

3kg of PLA and 600g of phenolic resin (PKHH) with a weight-average molecular weight of 850,000 were added to the high-speed blender, and a premix was obtained after initial mixing for 5 minutes, which was then subjected to an extruder at 170-190°C. Extrusion granulation, and finally drying to obtain blended granules, the formula (20 wt.% phenolic resin) is abbreviated as PLA/20PKHH in the chart.

2. Preparation of characterization samples and their characterization

1) Injection molding the pellets obtained in step 1 at 190° C. to obtain stretched national standard splines and national standard impact splines that automatically generate gaps. In 2006, its tensile properties were tested, and its impact strength was tested by JXUD5.5 pendulum impact tester and in accordance with the national standard GB/T1843-2008;

2) Press the blended sample into a film, and use the TA DHR-3 dynamic rheology tester to perform time scanning;

3) The splines obtained by injection molding were subjected to liquid nitrogen embrittlement, and then the morphology of the cross-section of the samples was observed under a scanning electron microscope.

The mechanical properties of the composites obtained by using the 5569 Instron universal testing machine and the JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10 mm/min. It can be seen from the chart that the tensile strength is 49.7MPa, which is about 26.6% lower than that of the blank sample; the elongation at break is 226.1%, which is about 32 times higher than that of the blank sample; the automatic Young's modulus is 2.4GPa, which is 17.2% lower than that of the blank sample; The impact strength is 13.2kJ/m ² , which is about 312.5% higher than that of the blank sample.

Example 8

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using phenolic resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

3kg of PLA and 300g of phenolic resin (PKHB) with a weight-average molecular weight of 32,000 were added to a high-speed blender, and a premix was obtained after initial mixing for 5 minutes, which was then subjected to an extruder at 170-190°C. Extrusion and pelletization, and finally drying to obtain blended pellets, the formula (10 wt.% phenolic resin) is abbreviated as PLA/10PKHB in the chart.

2. Preparation of characterization samples and their characterization

1) Injection molding the pellets obtained in step 1 at 190° C. to obtain stretched national standard splines and national standard impact splines that automatically generate gaps. In 2006, its tensile properties were tested, and its impact strength was tested by JXUD5.5 pendulum impact tester and in accordance with the national standard GB/T1843-2008;

2) Press the blended sample into a film, and use the TA DHR-3 dynamic rheology tester to perform time scanning;

3) The splines obtained by injection molding were subjected to liquid nitrogen embrittlement, and then the morphology of the cross-section of the samples was observed under a scanning electron microscope.

The mechanical properties of the composites obtained by using the 5569 Instron universal testing machine and the JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10 mm/min. It can be seen from the chart that the tensile strength is 57.5MPa, which is about 8.6% lower than that of the blank sample; the elongation at break is 130.5%, which is about 18 times higher than that of the blank sample; the automatic Young's modulus is 2.6GPa, which is 10.3% lower than that of the blank sample; The impact strength is 6.7kJ/m ² , which is about 109.4% higher than that of the blank sample.

Example 9

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using phenolic resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

3kg of PLA and 600g of phenolic resin (PKHB) with a weight-average molecular weight of 32,000 were added to the high-speed blender, and a premix was obtained after initial mixing for 5 minutes, which was then subjected to an extruder at 170-190°C. Extrusion granulation, and finally drying to obtain blended pellets, the formula (20 wt.% phenolic resin) is abbreviated as PLA/20PKHB in the chart.

2. Preparation of characterization samples and their characterization

1) Injection molding the pellets obtained in step 1 at 190° C. to obtain stretched national standard splines and national standard impact splines that automatically generate gaps. In 2006, its tensile properties were tested, and its impact strength was tested by JXUD5.5 pendulum impact tester and in accordance with the national standard GB/T1843-2008;

2) Press the blended sample into a film, and use the TA DHR-3 dynamic rheology tester to perform time scanning;

3) The splines obtained by injection molding were subjected to liquid nitrogen embrittlement, and then the morphology of the cross-section of the samples was observed under a scanning electron microscope.

The mechanical properties of the composites obtained by using the 5569 Instron universal testing machine and the JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10 mm/min. It can be seen from the chart that the tensile strength is 48.7MPa, which is about 22.6% lower than that of the blank sample; the elongation at break is 238.2%, which is about 34 times higher than that of the blank sample; the automatic Young's modulus is 2.3GPa, which is 20.7% lower than that of the blank sample. ; The impact strength is 14.7kJ/m ² , which is about 359.4% higher than that of the blank sample.

Comparative Example 1

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using epoxy resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

3kg of PLA and 300g of epoxy resin (CYD-011) with a weight average molecular weight of 900 were added to the high-speed blender, and the premix was obtained after initial mixing for 5 minutes, and then extruded at 170-190°C in an extruder. Extrusion and granulation were performed, and finally, the blended pellets were obtained by drying. The formulation (10 wt. % epoxy resin) was abbreviated as PLA/10CYD-011 in the chart.

2. Preparation of characterization samples and their characterization

The pellets obtained in step 1 are injected at 190°C to obtain tensile GB splines and GB impact splines that automatically generate notches, and then use 5569Instron universal tensile testing machine and test according to GB/T1040.2-2006 Its tensile properties are tested by JXUD5.5 pendulum impact tester and its impact strength is tested according to the national standard GB/T1843-2008;

The mechanical properties of the composite materials tested by 5569 Instron universal testing machine and JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10mm/min; it can be seen from the chart that the tensile strength is 62.7MPa , there is no obvious change compared with the blank sample; the elongation at break is 8.1%, which has no obvious change compared with the blank sample; the automatic Young's modulus is 3.0GPa, which has no obvious change compared with the blank sample; the impact strength is 3.1, which has no obvious change compared with the blank sample.

Comparative Example 2

A method for improving the comprehensive properties of PLA such as mechanical properties and heat resistance by using epoxy resin, the specific steps are as follows:

1. Extrusion to obtain blended pellets

Add 3kg of PLA and 300g of epoxy resin (DER-669) with a weight-average molecular weight of 900 into a high-speed blender. After initial mixing for 5 minutes, a premix is obtained, and then it is extruded at 170-190 ° C in an extruder. Extrusion granulation was performed, and finally, the blended pellets were obtained by drying. The formulation (10 wt. % epoxy resin) was abbreviated as PLA/10DER-669 in the diagram.

2. Preparation of characterization samples and their characterization

The pellets obtained in step 1 are injected at 190°C to obtain tensile GB splines and GB impact splines that automatically generate notches, and then use 5569Instron universal tensile testing machine and test according to GB/T1040.2-2006 For its tensile properties, JXUD5.5 pendulum impact tester was used to test its impact strength in accordance with the national standard GB/T1843-2008.

The mechanical properties of the composites obtained by using the 5569 Instron universal testing machine and the JXUD5.5 pendulum impact tester are shown in Table 1 and Figure 2, and the tensile rate is 10 mm/min. It can be seen from the chart that the tensile strength is 63.5MPa, which has no obvious change compared with the blank sample; the elongation at break is 6.6%, which has no obvious change compared with the blank sample; the automatic Young's modulus is 3.0GPa, which has no obvious change compared with the blank sample; the impact strength 3.1, there is no obvious change compared with the blank sample.

Table 1. Different PLA formulations and their various mechanical properties.

Claims (10)

1. The high-strength high-toughness polylactic acid-based composite material is characterized by being prepared by melting and blending polylactic acid and phenoxy resin, wherein the phenoxy resin accounts for 1-20 wt% of the composite material; wherein the weight average molecular weight of the phenoxy resin is more than or equal to 2 ten thousand.

2. The high-strength high-toughness polylactic acid-based composite material according to claim 1, wherein the phenoxy resin accounts for 4-20 wt% of the mass of the composite material; preferably 7 to 20 wt%.

3. The high-strength high-toughness polylactic acid-based composite material according to claim 1 or 2, wherein said phenoxy resin satisfies the following conditions: the repeating unit contains at least one backbone ether linkage and at least one pendant hydroxyl group.

4. The preparation method of the high-strength high-toughness polylactic acid-based composite material as claimed in any one of claims 1 to 3, wherein the method comprises the following steps: melting and blending polylactic acid and phenoxy resin to prepare the polylactic acid-based composite material; wherein the phenolic resin accounts for 1-20 wt% of the composite material, and the weight average molecular weight of the phenolic resin is more than or equal to 2 ten thousand.

5. The preparation method of the high-strength high-toughness polylactic acid-based composite material according to claim 4, wherein the preparation method comprises the following steps: and uniformly mixing polylactic acid and phenoxy resin to obtain a premix, and then melting and blending the premix at 170-190 ℃ to obtain the polylactic acid-based composite material.

6. The preparation method of the high-strength high-toughness polylactic acid-based composite material according to claim 5, wherein the polylactic acid and the phenoxy resin are blended at a high speed of 250-350 r/min for 1-10 min to obtain a premix.

7. The preparation method of the high-strength high-toughness polylactic acid-based composite material according to claim 5 or 6, wherein the pre-mixture is extruded and pelletized in an extruder at 170-190 ℃, and then dried to obtain blended pellets, namely the polylactic acid-based composite material.

8. The polylactic acid reinforced toughening agent is characterized in that the reinforced toughening agent is phenoxy resin with the weight average molecular weight of more than or equal to 2 ten thousand.

9. The polylactic acid reinforced toughening agent according to claim 8, wherein the addition amount of the reinforced toughening agent is 1-20 wt% of the mass of the polylactic acid; preferably 4 to 20 wt%; more preferably 7 to 20 wt%.

10. The phenolic oxygen resin is used for reinforcing and toughening polylactic acid, and the weight average molecular weight of the phenolic oxygen resin is more than or equal to 2 ten thousand;

further, when the phenoxy resin is used for reinforcing and toughening the polylactic acid, the using amount of the phenoxy resin is 1-20 wt% of the mass of the polylactic acid; preferably 4 to 20 wt%; more preferably 7 to 20 wt%.

Images