Preparation method of polylactic acid flame-retardant thermal-insulation composite material

Abstract

The invention relates to a preparation method of a polylactic acid flame-retardant thermal-insulation composite material, which is characterized in that a thermal-insulation and heat-resistant multifunctional flame retardant FAC-KH550-PA-MEL is added into a biodegradable polylactic resin matrix, and is synthesized by modifying waste fly ash hollow microspheres (FAC) with a silane coupling agent (KH550), phytic acid (PA) and melamine (MEL), the halogen-free flame-retardant elements phosphorus and nitrogen are sequentially introduced to the surface of the FAC, so that the carbon forming ability and flame-retardant effect of the FAC are improved. The prepared FAC-KH550-PA-MEL and polylactic acid are subjected to melt blending in a HAAKE rheometer and then are subjected to injection molding through an injection molding machine to obtain the polylactic acid composite material, the limit oxygen index (LOI) of PLA / 5FAC-KH550-PA-MEL reaches 31.8%, the UL-94 test reaches the V-0 level, and the pH RR and the THR in the cone calorimetry test are respectively reduced by 28.06% and 33.12% compared with pure PLA. The prepared modified fly ash hollow microspheres have the advantages of being good in processing effect, good in flame retardant effect, low in heat conductivity coefficient and the like in polylactic acid, and have wide application prospects and markets.

Description

Technical Field

[0001] The invention belongs to the technical field of polylactic acid flame retardancy, and specifically relates to a polylactic acid flame retardant thermal insulation composite material and a preparation method thereof. Background Art

[0002] Environmental pollution and non-renewability of petroleum-based polymer materials force us to develop biodegradable polymers and polymer composites. Polylactic acid (PLA), as a biodegradable polymer material, has been widely used in packaging, construction, cushioning, heat insulation, sound insulation, automobiles, and electronic appliances due to its good mechanical properties, easy processing, and good thermal stability. However, PLA exhibits flammability and is accompanied by continuous molten droplets, which limits its promotion and application. Therefore, PLA must be flame-retardant treated.

[0003] Fly ash hollow microspheres (FAC) are the main solid waste from coal-fired power plants. After screening, it shows low density, high specific strength, low thermal conductivity and high temperature resistance. FAC is usually composed of SiO2, Al2O3, Fe2O3, CaO, MgO and SO3. The silicon-oxygen tetrahedral structure of FAC shows inherent non-flammability. Therefore, modified FAC has great potential as an additive flame retardant in improving the flame retardancy and thermal insulation of polylactic acid. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a polylactic acid flame retardant thermal insulation composite material in view of the deficiencies of the flame retardant performance of polylactic acid. In order to improve the flame retardancy and thermal insulation of the polylactic acid composite material and increase the comprehensive performance of the polylactic acid composite material, the present invention uses polylactic acid and phytic acid melamine modified fly ash hollow microspheres for blending to prepare a polylactic acid flame retardant thermal insulation composite material, which improves the flame retardancy of the polylactic acid composite material and has a low thermal conductivity, so that the polylactic acid composite material has broad application prospects and market demand.

[0005] In order to achieve the above purpose, the technical solution adopted is: A method for preparing a polylactic acid flame retardant thermal insulation composite material, characterized in that the specific steps are as follows: The modified FAC is added into the biodegradable polylactic acid resin matrix, and the mixture is melt-blended in a HAAKE rheometer, and the blended material is injection-molded to obtain a polylactic acid composite material.

[0006] Furthermore, the preparation method of the polylactic acid flame retardant thermal insulation composite material is characterized in that the preparation method of the modified FAC comprises the following specific synthesis steps: 1) Take 10 mL of silane coupling agent KH550 and add it dropwise to 100 mL of ethanol-water (volume ratio = 9:1) mixed solution, and stir at room temperature for 60 min to fully hydrolyze KH550. Disperse 5 g of activated FAC in it, stir and react at 80 °C for 8 h, wash with anhydrous ethanol and deionized water, and dry in vacuum at 110 °C. The prepared sample is marked as FAC-KH550; 2) 5 g FAC-KH550, 20 g PA and 40 mL anhydrous ethanol were stirred at 40 °C for 8 h, the obtained product was washed with anhydrous ethanol, and vacuum dried at 50 °C for 12 h. The obtained product was labeled as FAC-KH550-PA; 3) 3.5 g MEL was added to 40 mL deionized water and stirred at 80 °C for 10 min. Then 5 g FAC-KH550-PA was added to 10 mL deionized water and dropped into the above solution and stirred for 30 min. The obtained product was filtered and washed with 60 °C deionized water and vacuum dried at 50 °C for 24 h. The obtained product was labeled as FAC-KH550-PA-MEL. Furthermore, the method for preparing a polylactic acid flame retardant thermal insulation composite material is characterized in that in the preparation method of activated FAC in step (1), the 100-mesh activated FAC is rinsed in deionized water, and the activation steps are as follows: 1) Take 5 g of rinsed FAC and place it in a 250 mL three-necked flask; 2) Add 100 mL of 10 wt% hydrochloric acid solution and ultrasonicate for 60 min to remove impurities on the FAC surface; 3) The sample was washed with deionized water until neutral, dried in an oven at 110 °C for 3 h, and cooled in a desiccator for later use.

[0007] Furthermore, the raw material components are calculated by weight: 99-95 parts of polylactic acid and 1-5 parts of modified FAC.

[0008] Furthermore, the method for preparing the polylactic acid flame retardant thermal insulation composite material is characterized in that the specific preparation steps are as follows: 1) Dry 99-95 parts of polylactic acid in an oven at 80°C for 24 hours; 2) Mix the dried polylactic acid with 1-5 parts of modified FAC in a high-speed mixer for 10 minutes; 3) The mixed polylactic acid was placed in a HAAKE rheometer and blended at 180 °C and 40 rpm for 5 min to obtain a polylactic acid composite material; 4) The blended polylactic acid composite material was injected at a temperature of 180 °C and an injection pressure of 750 Kgf / cm 2 Samples of different sizes were injection molded.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: the polylactic acid flame retardant thermal insulation material prepared by the present invention has a small amount of modified fly ash hollow microsphere flame retardant added, which is melt-blended with the polylactic acid matrix to have an excellent flame retardant effect, and achieves a polylactic acid flame retardant grade of V-0 at a low addition amount, and the limiting oxygen index reaches 31.8% while having a thermal insulation function, thereby broadening the application scope of polylactic acid composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Peak heat release rate pHRR (a) and total heat release THR (b) curves of polylactic acid and its composites. DETAILED DESCRIPTION

[0012] In order to further illustrate the preparation method of a polylactic acid flame retardant thermal insulation composite material of the present invention, the preparation method of a polylactic acid flame retardant thermal insulation composite material of the present invention will be further described in detail below in combination with specific embodiments: In the embodiment, a method for preparing a polylactic acid flame retardant thermal insulation composite material comprises the following raw material components by weight: 99-95 parts of polylactic acid and 1-5 parts of modified fly ash hollow microspheres.

[0013] Comparative Example 1. 100 parts of the polylactic acid matrix was dried in a vacuum oven at 80 °C for 24 hours and then added to the HAAKE rheometer. The pure polylactic acid material was obtained by blending at 180 °C and 40 rpm for 5 min. The injection temperature was 180 °C and the injection pressure was 750 Kgf / cm 2 Samples of different sizes were injection molded.

[0014] Comparative Example 2. Add 1 part of FAC polylactic acid flame retardant insulation material, the specific steps are as follows: 1) Take 1 part of rinsed FAC and 99 parts of polylactic acid and dry them in an oven at 80℃ for 24 hours; 2) Mix the dried polylactic acid with 1 part of FAC in a high-speed mixer for 10 min; 3) The mixed polylactic acid was placed in a HAAKE rheometer and blended at 180 °C and 40 rpm for 5 min to obtain a polylactic acid composite material; 4) The blended polylactic acid composite material was injected at a temperature of 180 °C and an injection pressure of 750 Kgf / cm 2 Samples of different sizes were injection molded.

[0015] Comparative Example 3. The preparation method of the polylactic acid composite material of this comparative example is basically the same as that of comparative example 2, except that the ratio of FAC to PLA added is FAC:PLA=3:97 in step (1).

[0016] Comparative Example 4. The preparation method of the polylactic acid composite material of this comparative example is basically the same as that of comparative example 2, except that the ratio of FAC to PLA added is FAC:PLA=5:95 in step (1).

[0017] Example 1. Add 1 part of modified FAC polylactic acid flame retardant insulation material, the specific steps are as follows: 1) Take 5 g of rinsed FAC and place it in a 250 mL three-necked flask; 2) Add 100 mL of 10 wt% hydrochloric acid solution and ultrasonicate for 60 min to remove impurities on the FAC surface; 3) The sample was washed with deionized water until neutral and dried in an oven at 110 °C for 3 h; 4) Take 10 mL of silane coupling agent KH550 and add it dropwise to 100 mL of ethanol-water (volume ratio = 9:1) mixed solution, and stir at room temperature for 60 min to fully hydrolyze KH550. Disperse 5 g of acid-washed FAC in it, stir and react at 80°C for 8 h, wash with anhydrous ethanol and deionized water, and dry in vacuum at 110°C. The prepared sample is marked as FAC-KH550; 5) 5 g FAC-KH550, 20 g PA and 40 mL anhydrous ethanol were stirred at 40 °C for 8 h, the obtained product was washed with anhydrous ethanol, and vacuum dried at 50 °C for 12 h. The obtained product was labeled as FAC-KH550-PA; 6) 3.5 g MEL was added to 40 mL deionized water and stirred at 80 °C for 10 min. Then 5 g FAC-KH550-PA was added to 10 mL deionized water and dropped into the above solution and stirred for 30 min. The obtained product was filtered and washed with 60 °C deionized water and vacuum dried at 50 °C for 24 h. The obtained product was labeled as FAC-KH550-PA-MEL.

[0018] 7) Dry 99 parts of polylactic acid in an oven at 80°C for 24 h; 8) Mix the dried polylactic acid and 1 part of modified FAC in a high-speed mixer for 10 min; 9) The mixed polylactic acid was placed in a HAAKE rheometer and blended at 180 °C and 40 rpm for 5 min to obtain a polylactic acid composite material; 10) The blended polylactic acid composite material was injected at a temperature of 180 °C and an injection pressure of 750 Kgf / cm2 Samples of different sizes were injection molded.

[0019] Example 2. The preparation method of the polylactic acid composite material of this embodiment is basically the same as that of Embodiment 1, except that the ratio of FAC to PLA added is FAC-KH550-PA-MEL:PLA=3:97 in step (1).

[0020] Example 3. The preparation method of the polylactic acid composite material of this embodiment is basically the same as that of Embodiment 1, except that the ratio of FAC to PLA added is FAC-KH550-PA-MEL:PLA=5:95 in step (1).

[0021] The test results of the polylactic acid flame retardant thermal insulation materials of Comparative Examples 1-4 and Examples 1-3 are shown in Table 1.

[0022] Table 1 The composite materials obtained from the above-mentioned embodiments 1-3 and comparative examples 1-4 were subjected to combustion experiments, and the vertical combustion grade and limiting oxygen index value of the materials were detected. The results are shown in Table 1. As can be seen from Table 1, compared with comparative examples 1-4, the flame retardant properties of embodiments 1-3 of the present invention with the addition of modified FAC are significantly improved, and the oxygen index reaches 26.5%-31.8%, and when the addition amount reaches 5 parts, the UL-94 grade is V-0. Compared with comparative example 1, the residual carbon amount of embodiment 3 is increased from 0.70% to 8.05%, indicating that the phytic acid and melamine grafted on FAC play a role in PN synergistic flame retardancy. Moreover, when the addition amount is 5 parts of modified FAC, the thermal conductivity decreases, indicating that the thermal insulation performance is improved.

[0023] for Figure 1 The peak pHRR of heat release rate of polylactic acid and its composites ( Figure 1 a) and total heat release THR ( Figure 1 b) Curve, from Figure 1 The cone test results show that the pHRR value of pure polylactic acid is 505.57 kW / m 2 , THR value is 87.04MJ / m 2 Compared with pure polylactic acid, the pHRR values ​​of comparative examples 2-4 did not change much, but the THR values ​​decreased, because the addition of FAC enhanced the carbon layer, thereby improving the fire resistance of the composite material. Compared with pure polylactic acid, the pHRR values ​​and THR values ​​of examples 1-3 decreased, and the pHRR value of example 3 decreased by 28.06% and the THR value decreased by 33.12%, indicating that the flame retardant properties of the composite material were improved by adding 5 parts of modified FAC.

[0024] The present invention and its implementation methods are described schematically above, which is not restrictive. The drawings are only one of the implementation methods of the present invention. Therefore, if a person skilled in the art is inspired by the invention and designs a structure and implementation method similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a polylactic acid flame retardant thermal insulation composite material, characterized in that: The specific steps are as follows: Modified fly ash hollow microspheres are added into a biodegradable polylactic acid resin matrix, the mixture is melt-blended in a HAAKE rheometer, and the blended material is injection-molded to obtain a polylactic acid composite material.

2. The method for preparing a polylactic acid flame retardant thermal insulation composite material according to claim 1, characterized in that: The preparation method of modified FAC, the specific synthesis steps are as follows: 1) Take 10 mL of silane coupling agent KH550 and add it dropwise to 100 mL of ethanol-water (volume ratio = 9:1) mixed solution, and stir at room temperature for 60 min to fully hydrolyze KH550. Disperse 5 g of activated FAC in it, stir and react at 80 °C for 8 h, wash with anhydrous ethanol and deionized water, and dry in vacuum at 110 °C. The prepared sample is marked as FAC-KH550; 2) 5 g FAC-KH550, 20 g PA and 40 mL anhydrous ethanol were stirred at 40 °C for 8 h, the obtained product was washed with anhydrous ethanol, and vacuum dried at 50 °C for 12 h. The obtained product was labeled as FAC-KH550-PA; 3) 3.5 g MEL was added to 40 mL deionized water and stirred at 80 °C for 10 min. Then, 5 g FAC-KH550-PA was added to 10 mL deionized water and dropped into the above solution and stirred for 30 min. The obtained product was filtered and washed with 60 °C deionized water and vacuum dried at 50 °C for 24 h. The obtained product was labeled as FAC-KH550-PA-MEL.

3. The method for preparing a polylactic acid flame retardant thermal insulation composite material according to claim 2, characterized in that: In the preparation method of activated FAC in step (1), the 100-mesh activated FAC is rinsed in deionized water, and the activation steps are as follows: 1) Take 5 g of rinsed FAC and place it in a 250 mL three-necked flask; 2) Add 100 mL of 10 wt% hydrochloric acid solution and ultrasonicate for 60 min to remove impurities on the FAC surface; 3) The samples were washed with deionized water until neutral and dried in an oven at 110 °C for 3 h.

4. The method for preparing a polylactic acid flame retardant thermal insulation composite material according to claim 1, characterized in that: The raw material components are calculated by weight: 99-95 parts of polylactic acid and 1-5 parts of modified FAC.

5. A method for preparing the polylactic acid flame retardant thermal insulation composite material according to any one of claims 1 to 4, characterized in that: The specific preparation steps are as follows: 1) Dry 99-95 parts of polylactic acid in an oven at 80°C for 24 hours; 2) Mix the dried polylactic acid with 1-5 parts of modified FAC in a high-speed mixer for 10 minutes; 3) The mixed polylactic acid was placed in a HAAKE rheometer and blended at 180 °C and 40 rpm for 5 min to obtain a polylactic acid composite material; 4) The blended polylactic acid composite material is injected at a temperature of 180°C and an injection pressure of 750 Kgf / cm 2 Samples of different sizes were injection molded.

Images