PET / PBAT composite material and preparation method thereof

Abstract

The invention belongs to the technical field of composite materials, and particularly relates to a PET / PBAT composite material and a preparation method thereof.The method comprises the steps that a pre-volume-increasing agent HDI or MDI is added into PBA to react to obtain a prepolymer, then the prepolymer serves as a bulking agent to be added into a mixture of PET and PBAT, and the PET / PBAT composite material is obtained through a reaction. According to the PET / PBAT composite material disclosed by the invention, the recycling of PET is realized, the environmental pressure is reduced, and the interfacial compatibility of PET and PBAT is enhanced by utilizing the prepolymer, so that the PET / PBAT composite material has excellent mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and in particular relates to a PET / PBAT composite material and a preparation method thereof. Background Art

[0002] Polyethylene terephthalate (PET) is a thermoplastic polymer material with many advantages. It has high strength, good chemical resistance, strong stability, good heat resistance and electrical insulation, and low cost. It is one of the main and most commonly used plastic packaging materials. PET is widely used, so the recycling of waste PET is particularly important. Polybutylene adipate / terephthalate (PBAT) is a polyester-based bioplastic with good ductility. In addition, its elongation at break and impact resistance are also good, and its heat resistance is relatively outstanding. PBAT is considered to be a leading environmentally friendly polymer, but compared with other common plastics, the production cost of PBAT is significantly higher. Therefore, the use of PBAT and PET to blend a blended composite material can make the composite material have a certain degree of environmental friendliness, reduce environmental pressure, and also expand the application field of PET and PBAT. However, the interface between PET and PBAT is incompatible, so it is necessary to choose a suitable volume-enhancing modification method to improve the mechanical properties of the composite material.

[0003] At present, adding a compatibilizer to composite materials is one of the simplest and most efficient methods for capacity expansion and modification. Maleic anhydride, polyurethane prepolymer, epoxy coupling agent, etc. are typical reactive compatibilizers. The reaction mechanism is that the compatibilizer can react chemically with the hydroxyl group, carboxyl group, etc. at the end of the polymer to be expanded to form a covalent bond. Polyurethane prepolymer is a reactive semi-finished product made from polyols and polyisocyanates. The polyurethane prepolymer compatibilizer has a significant effect. The document "Preparation and Properties of Polyurethane Prepolymer Compatibilized PLA / TPU Composites" was published in "Plastics" Vol. 48, No. 1, 2019, pp. 11-15. A series of polylactic acid / thermoplastic polyurethane (PLA / TPU) composites were prepared using polylactic acid (PLA), thermoplastic polyurethane (TPU) and polyurethane prepolymer (PUP) as raw materials, which significantly improved the compatibility of PLA and TPU blends. However, the existing technology still has the problem of poor volume expansion effect on PET / PBAT composite materials, resulting in reduced mechanical properties of PET / PBAT composite materials. Summary of the invention

[0004] The purpose of the present invention is to provide a PET / PBAT composite material and a preparation method thereof, in which a prepolymer prepared by PBA and HDI or MDI is used as a compatibilizer to promote the interface compatibility between PBAT and PET, thereby ultimately improving the mechanical properties of the PET / PBAT composite material.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a PET / PBAT composite material, characterized in that:

[0007] S1. Add a pre-compatibilizer to PBA to obtain a prepolymer; the pre-compatibilizer is HDI or MDI;

[0008] S2. First add PBAT to PET, then add prepolymer, and react to obtain a PET / PBAT composite material.

[0009] The reaction temperature in S1 is 80° C. and the reaction time is 1 h.

[0010] The reaction temperature in S2 is 250° C. and the reaction time is 5 min.

[0011] The PET is prepared from waste PET plastic bottles.

[0012] In a second aspect, the present invention provides a PET / PBAT composite material, wherein the PET / PBAT composite material is prepared by the aforementioned preparation method.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The preparation method of the present invention blends PBAT with recycled PET to prepare a PET / PBAT composite material, thereby realizing the recycling of PET and reducing environmental pressure. In order to make the PET / PBAT composite material have better mechanical properties, a prepolymer is prepared by using PBA and a pre-compatibilizer HDI or MDI. Since PBAT is a copolymer of butylene adipate and butylene terephthalate, it has the characteristics of polybutylene adipate and polybutylene terephthalate. Therefore, the prepolymer prepared by using PBA having similar structural units to PBAT and HDI or MDI as a compatibilizer can better form a cross-linking effect with polymer molecules, thereby better promoting the interface compatibility between PBAT and PET, and finally improving the mechanical properties of the PET / PBAT composite material. At the same time, in order to further reduce costs and recycle PET as much as possible, the present invention also explores the influence of PET content on the mechanical properties of the PET / PBAT composite material, thereby determining the optimal addition ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 These are the stress-strain curves of P-PET-H-40, P-PET-H-50, P-PET-H-60, and P-PET-H-70.

[0016] Figure 2These are the stress-strain curves of P-PET-H-50 and P-PET-M. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with specific implementations and drawings.

[0018] A method for preparing a PET / PBAT composite material, the preparation method comprising:

[0019] S1. Add a pre-compatibilizer to PBA to obtain a prepolymer; the pre-compatibilizer is HDI or MDI;

[0020] S2. First add PBAT to PET, then add prepolymer, and react to obtain a PET / PBAT composite material.

[0021] The reaction temperature in S1 is 80° C. and the reaction time is 1 h.

[0022] The reaction temperature in S2 is 250° C. and the reaction time is 5 min.

[0023] The PET is prepared from waste PET plastic bottles.

[0024] A PET / PBAT composite material is prepared by the above-mentioned preparation method.

[0025] Sources of reagents: PBA (polybutylene adipate-1,4-diol, purchased from Xuzhou Yihuiyang New Materials Co., Ltd.); HDI (hexamethylene-1,6-diisocyanate, CAS: 822-06-0, purchased from China National Pharmaceutical Group); PBAT (purchased from Xinjiang Lanshan Tunhe Degradable Materials Co., Ltd.); MDI (4,4-diphenylmethyl diisocyanate, CAS: 101-68-8, purchased from China Pharmaceutical Group); PET: collect discarded PET plastic bottles, clean them, cut them into long strips, and dry them for later use.

[0026] Embodiment 1:

[0027] S1. According to the reaction molar ratio of -OH hydroxyl group in PBA and -NCO isocyanate in pre-compatibilizer of 1:2, weigh 100g PBA into a flask and heat it to 110°C in an oil bath. Stir and evacuate to remove impurities. After 30 minutes, cool the reaction system to 60°C, slowly add 16.8g HDI within 5 minutes, and then control the reaction system to heat to 80°C. React for 1 hour to obtain a colorless, transparent and viscous prepolymer, which is named PBAPU-H.

[0028] S2. Set the temperature of the internal mixer (model QE-70c, purchased from Wuhan Qien Technology Co., Ltd.) to 250° C., first add 32 g of PET to the internal mixer, add 48 g of PBAT after the PET is melted, and add 8 g of PBAPU-H after the PBAT is melted and mix for 5 minutes to obtain a slightly yellow PET / PBAT composite material. The obtained PET / PBAT composite material is named P-PET-H-40.

[0029] Embodiment 2:

[0030] The difference from Example 1 is that:

[0031] The added amounts of PET and PBAT in S2 were 40 g and 40 g, respectively. The obtained PET / PBAT composite material was named P-PET-H-50.

[0032] Embodiment 3:

[0033] The difference from Example 1 is that:

[0034] The added amounts of PET and PBAT in S2 were 48 g and 32 g, respectively. The obtained PET / PBAT composite material was named P-PET-H-60.

[0035] Embodiment 4:

[0036] The difference from Example 1 is that:

[0037] The added amounts of PET and PBAT in S2 were 56 g and 24 g, respectively. The obtained PET / PBAT composite material was named P-PET-H-70.

[0038] Embodiment 5:

[0039] The difference from Example 2 is that:

[0040] HDI was replaced with 25g MDI. The prepolymer obtained by the reaction of MDI and PBA was named PBAPU-M. The obtained PET / PBAT composite material was named P-PET-M.

[0041] Comparative Example 1:

[0042] The temperature of the internal mixer was set at 250°C and the speed was set at 10 r / min. 32 g of PET raw material was added into the internal mixer. After it was melted, 48 g of PBAT was slowly added and mixed evenly to obtain a PET / PBAT composite material, which was named P-PET.

[0043] Performance Test:

[0044] Take 25g of the composite materials prepared in Examples 1-5 and Comparative Example 1 for hot pressing, and set the hot pressing conditions to a temperature of 250°C, a pressure of 20 MPa, and a hot pressing time of 5 min to obtain a sheet plate, which is then cut into dumbbell-shaped strips according to GB / T1040-200. At least 5 strips are prepared for each composite material. After the strips are stored at room temperature for one week, a mechanical property tensile test is performed.

[0045] Mechanical properties tensile test: A universal tensile tester (model CMT6503, purchased from Shenzhen Xinsansi Metrology Co., Ltd.) was used to perform tensile tests on the specimens according to the national standard GB / T1040.2-2006, with a tensile rate of 50 mm / min. The elongation at break and tensile strength of the samples were measured, and the average value and deviation were calculated. The tensile test data of Examples 1-5 and Comparative Example 1 are shown in Table 1, and the stress-strain curves of P-PET-H-40, P-PET-H-50, P-PET-H-60, and P-PET-H-70 are shown in Table 1. Figure 1 As shown, the stress-strain curves of P-PET-H-50 and P-PET-M are drawn as shown in Figure 2 shown.

[0046] Table 1 Mechanical properties test data of different composite materials

[0047] Spline Name Elongation at break (%) Tensile strength(MPa) P-PET-H-40 49.45±6.96 11.52±0.17 P-PET-H-50 16.99±0.75 22.77±0.49 P-PET-H-60 258.61±5.38 32.05±1.52 P-PET-H-70 4.35±0.51 28.9±0.9 P-PET-M 7.98±0.87 18.37±0.16 P-PET 3.7±0.95 21.8±1.36

[0048] (1) Comparing P-PET-H-40, P-PET-H-50, P-PET-H-60 and P-PET-H-70, it can be seen from Table 1 that when the PET content reaches 60%, the elongation at break of the composite material reaches a significant peak. Compared with P-PET-H-40, the elongation at break of P-PET-H-60 increased by about 5.2 times; compared with P-PET-H-50, the elongation at break of P-PET-H-60 increased by about 15.2 times; compared with P-PET-H-70, the elongation at break of P-PET-H-60 increased by about 59.45 times. This shows that when the PET content is 60%, the compatibilizer PBAPU-H has the best compatibilization effect on the PBAT and PET matrix. In addition, as the PET content increases, the tensile strength of the composite material increases first and then decreases; this is because PET itself has strong rigidity. As the PET content increases, the compatibility between PET and PBAT becomes worse, which is manifested in the decrease of elongation at break and tensile strength, and the increase of brittleness of the composite material. Figure 1 It can also be seen that P-PET-H-60 has better toughness than P-PET-H-40, P-PET-H-50 and P-PET-H-70.

[0049] (2) Comparing P-PET-H-50 with P-PET-M, it can be seen from Table 1 that when the PET content and the content of the compatibilizer are the same, the elongation at break of P-PET-H-50 is greater than that of P-PET-M. It is speculated that this is because the molecular structure of PBAPU-H is a straight chain, and the product after the reaction with the PET / PBAT material is also a straight chain, so the elongation at break of P-PET-H-50 is larger; while the molecular structure of PBAPU-M contains benzene rings, which have high rigidity. As a compatibilizer, after being blended with PET / PBAT, the rigidity of the composite material P-PET-M is also enhanced, so the tensile strength of P-PET-M is relatively small. Figure 2 It can also be seen that P-PET-H-50 has better toughness than P-PET-M.

Claims

1. A method for preparing a PET / PBAT composite material, characterized in that: The preparation method comprises: S1. Add a pre-compatibilizer to PBA to obtain a prepolymer; the pre-compatibilizer is HDI or MDI; S2. First add PBAT to PET, then add prepolymer, and react to obtain a PET / PBAT composite material.

2. The method for preparing a PET / PBAT composite material according to claim 1, characterized in that: The reaction temperature in S1 is 80° C. and the reaction time is 1 h.

3. The method for preparing a PET / PBAT composite material according to claim 1, characterized in that: The reaction temperature in S2 is 250° C. and the reaction time is 5 min.

4. The method for preparing a PET / PBAT composite material according to claim 1, characterized in that: The PET is prepared from waste PET plastic bottles.

5. A PET / PBAT composite material, characterized in that: The PET / PBAT composite material is prepared by the preparation method according to any one of claims 1 to 4.

Images