Impact-resistant hard PP plate and preparation method thereof

Abstract

The invention relates to an impact-resistant hard PP plate and a preparation method thereof, and belongs to the technical field of polymer composite materials. The hard PP plate is prepared from the following components: 25 to 40 weight percent of soft core-hard shell filler, 0.8 to 1.2 weight percent of lubricant, 0.15 to 0.2 weight percent of antioxidant and the balance of PP resin, the whole soft core-hard shell filler is of a spherical hard structure, has high structural stability, is similar to a traditional solid hard filler and has an obvious promoting effect on improvement of the strength and rigidity of a composite system, and under external impact force, a shell layer composed of rigid particles disperses stress and microcosmic deformation among the rigid particles, so that the strength and rigidity of the composite system are improved. In addition, a polyester organic structure of the core layer absorbs impact energy, microcracks formed by the PP matrix are reduced, and particularly, under non-destructive repeated impact, the soft core-hard shell filler forms stable release impact force, so that the board keeps excellent mechanical properties, and rigid-tough balance optimization of the board is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer composite materials, and in particular, relates to an impact-resistant hard PP board and a preparation method thereof. Background Art

[0002] Polypropylene (PP) sheets are widely used in the automotive, packaging, construction, electronics and other fields due to their advantages such as light weight, chemical corrosion resistance and easy processing. However, there is a significant performance contradiction between the rigidity (bending strength, modulus) and toughness (impact strength) of traditional PP sheets. Especially under frequent impact or complex stress environments, the material is prone to brittle fracture or performance degradation, which seriously limits its application in high-intensity scenarios.

[0003] At present, the reinforcement and modification of rigid PP sheets mainly adopts the method of adding rigid fillers. The bending strength and modulus are improved by introducing inorganic rigid particles. However, the interface bonding between the rigid filler and the PP matrix is ​​weak, and stress concentration induces crack propagation, resulting in a decrease in impact resistance. Adding toughening agents can improve the impact resistance to a certain extent, but the modulus difference between the toughening agent and the PP matrix is ​​large, resulting in a decrease in the strength and bending modulus of the sheet, which cannot meet the load-bearing requirements of the structural parts. Moreover, under repeated impacts, the rigid filler and the PP matrix produce irreversible deformation and debonding, forming a large number of imperceptible microcracks, which leads to the deterioration of the mechanical properties of the sheet and poses serious safety hazards. Summary of the invention

[0004] In order to solve the technical problems mentioned in the background technology, the object of the present invention is to provide an impact-resistant rigid PP board and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions: An impact-resistant hard PP board comprises: 25-40wt% of a soft core-hard shell filler, 0.8-1.2wt% of a lubricant, 0.15-0.2wt% of an antioxidant, and the balance being PP resin.

[0006] The preparation method of soft core-hard shell filler is as follows: Step 1, synthesis of modified intermediate: premix mercaptoethanol, azobisisobutyronitrile and ethyl acetate, heat to 40-60°C and stir to activate for 15-20 min, then add polydipentaerythritol hexaacrylate and photosensitizer and mix at 600-800 mW / cm 2 The reaction was stirred for 1-1.5 hours under UV irradiation intensity, and ethyl acetate was removed to prepare a modified intermediate.

[0007] In the above reaction, the feed ratio of polydipentaerythritol hexaacrylate, mercaptoethanol, azobisisobutyronitrile, photosensitizer and ethyl acetate is 10mmol:65-70mmol:40-50mg:80-100mg:45-60mL, mercaptoethanol is added to polydipentaerythritol hexaacrylate, and an alcoholic hydroxyl group with a thioether structure is introduced for end modification.

[0008] Preferably, the photosensitizer is selected from α-hydroxyketone photoinitiators, which have high UV response activity and are conducive to efficient reaction.

[0009] Step 2, synthesis of an organic soft core matrix: the modified intermediate, triethylamine and dimethyl sulfoxide are mixed, heated to 60-80° C. in a dry gas atmosphere, γ-glycidyloxypropyltrimethoxysilane is added, stirred and reacted for 4-5.5 hours, and dimethyl sulfoxide is removed to prepare an organic soft core matrix.

[0010] In the above reaction, the feed ratio of the modified intermediate, γ-glycidyloxypropyltrimethoxysilane, triethylamine and dimethyl sulfoxide is 10mmol:0.15-0.2mol:10-15mL:80-110mL, the epoxy group of γ-glycidyloxypropyltrimethoxysilane and the terminal hydroxyl group of the modified intermediate are ring-opened, and a polymethoxysilane structure is introduced at the outer end of the molecule of the modified intermediate.

[0011] Step 3, composite of soft core-hard shell filler: add organic soft core matrix, metal oxide powder and ethanol aqueous solution and ultrasonically disperse them, acidify them with hydrochloric acid and stir them for 1-1.5 hours, let them stand and separate, remove the liquid phase, wash and dry them to obtain soft core-hard shell filler.

[0012] In the above reaction, the feed ratio of metal oxide micropowder, organic soft core matrix and ethanol aqueous solution is 50g:3.5-5g:120-150mL, the sulfide structure and oxygen-containing structure in the organic soft core matrix molecule form a chelating effect, enriched on the metal oxide micropowder in the dispersion, and then combined with the metal oxide micropowder by hydrolysis coupling of methoxysilane to form a composite structure with metal oxide micropowder as the shell and the organic soft core matrix as the core.

[0013] Preferably, the metal oxide powder is selected from nano-scale powder, and the particles of the formed shell layer are tightly bound to each other, which is beneficial to maintain the strengthening effect on the matrix polypropylene.

[0014] A method for preparing an impact-resistant hard PP board is as follows: Mixing and granulation: PP resin, lubricant and antioxidant are premixed and plasticized, and then soft core-hard shell filler is added and extruded and granulated to obtain modified masterbatch; Compression molding: The modified masterbatch is melted and extruded into a flat plate mold, and then hot-pressed, precision-pressed, and cooled to form a blank. Post-processing: Cut and trim the burrs on the blank plate, and send it to the annealing furnace for annealing and stress relief treatment to obtain an impact-resistant hard PP plate.

[0015] Furthermore, the annealing process parameters are set as follows: temperature is 120° C., and annealing time is 10 min / mm.

[0016] Beneficial effects of the present invention: The invention discloses a soft core-hard shell filler. The soft core-hard shell filler comprises a modified intermediate containing a thioether structure and a terminal alcohol hydroxyl group obtained by addition reaction of mercaptoethanol and polydipentaerythritol hexaacrylate, and then a polymethoxysilane structure is introduced into the outer end of the modified intermediate molecule by opening the ring of the terminal hydroxyl group of the modified intermediate by γ-glycidyloxypropyl trimethoxysilane, so as to obtain an organic soft core matrix, and the organic soft core matrix is ​​compounded with metal oxide micropowder by chelation formed by the thioether structure and the oxygen-containing structure in the organic soft core matrix molecule, and then the methoxysilane is combined with the metal oxide micropowder by hydrolysis coupling to form a soft core-hard shell filler with metal oxide micropowder as the shell and an organic soft core matrix as the shell. The composite structure is a spherical hard structure with a core; the soft core-hard shell filler is a spherical hard structure as a whole, which has high structural stability. Similar to traditional solid hard fillers, it significantly promotes the improvement of the strength and stiffness of the composite system. Under external impact, the shell layer composed of rigid particles disperses stress, the rigid particles undergo micro deformation, and the core layer polyester organic structure absorbs impact energy, reducing the formation of micro cracks in the PP matrix. Especially under non-destructive repeated impacts, the soft core-hard shell filler forms a stable release of impact force, so that the board maintains excellent mechanical properties and achieves optimization of the rigid-toughness balance of the board. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0018] Figure 1 This is an electron microscope image of the soft core-hard shell filler prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Example 1, preparing an impact-resistant hard PP plate, specifically as follows: (1) Preparation of soft core-hard shell fillers Synthesis of modified intermediates: mercaptoethanol, azobisisobutyronitrile and ethyl acetate were premixed, heated to 60°C and stirred at 120 rpm for 15 min, then polydipentaerythritol hexaacrylate and photosensitizer were added and mixed, stirred at 60 rpm at 800 mW / cm 2 The reaction was carried out under UV irradiation intensity for 1 hour, wherein the photosensitizer was selected from α-hydroxyketone photoinitiator 1173, and the feed ratio of polydipentaerythritol hexaacrylate, mercaptoethanol, azobisisobutyronitrile, photosensitizer and ethyl acetate was 10 mmol: 70 mmol: 50 mg: 100 mg: 60 mL, and then the ethyl acetate was removed by rotary evaporation to prepare a modified intermediate.

[0021] Synthesis of organic soft core matrix: Take the modified intermediate, triethylamine and dimethyl sulfoxide, mix them, introduce dry air until a stable gas flow is precipitated, heat to 80°C, stir at 180rpm, add γ-glycidyloxypropyltrimethoxysilane and react for 4h, wherein the feed ratio of the modified intermediate, γ-glycidyloxypropyltrimethoxysilane, triethylamine and dimethyl sulfoxide is 10mmol:0.2mol:15mL:110mL, then remove dimethyl sulfoxide by reduced pressure rotary evaporation to prepare an organic soft core matrix.

[0022] Composite of soft core-hard shell filler: Take organic soft core matrix and metal oxide powder, add 40% ethanol aqueous solution by volume, ultrasonically oscillate to form a uniform dispersion, add hydrochloric acid to acidify to pH 3, and rapidly stir at 240rpm for 1h, wherein the metal oxide powder is selected from nano alumina powder, and the feed ratio of metal oxide powder, organic soft core matrix and ethanol aqueous solution is 50g:5g:150mL. Then stand and separate, remove the liquid phase, wash and dry to obtain a soft core-hard shell filler.

[0023] (2) Preparation of hard PP board Mixing and granulation: take 25wt% of the soft core-hard shell filler prepared in this embodiment; 1.2wt% of lubricant, industrial grade calcium stearate; 0.2wt% of antioxidant, antioxidant 1010 and antioxidant 168 are mixed in equal weight ratio; the balance is PP resin, EP300H type resin raw material of Zhejiang Petrochemical is selected; first premix PP resin, lubricant and antioxidant in a high mixer, feed from the main feeding port of a twin-screw extruder, melt plasticize at 230±10°C, add soft core-hard shell filler from the side feeding port, extrude and pelletize to obtain a modified masterbatch.

[0024] Compression molding: The modified masterbatch is melt-extruded, and the melt discharge temperature is controlled to be 210±5°C. The melt is extruded into a flat plate mold, hot-pressed and shaped at 20MPa, and precision-pressed to determine the thickness. During the implementation process, a 5mm thick plate is designed, and then spray-cooled and molded to obtain a blank.

[0025] Post-processing: Cut and trim the burrs on the blank plate, send it into the annealing furnace, control the annealing temperature to 120°C, and the annealing time to 10 min / mm to obtain an impact-resistant hard PP plate.

[0026] Example 2, preparing an impact-resistant hard PP plate, specifically as follows: (1) Preparation of soft core-hard shell fillers Synthesis of modified intermediates: mercaptoethanol, azobisisobutyronitrile and ethyl acetate were premixed, heated to 40°C and stirred at 120 rpm for 20 min, then polydipentaerythritol hexaacrylate and photosensitizer were added, stirred at 60 rpm, and heated to 40°C for 20 min. 2 The reaction was carried out under UV irradiation intensity for 1.5 hours, wherein the photosensitizer was selected from α-hydroxyketone photoinitiator 1173, and the feed ratio of polydipentaerythritol hexaacrylate, mercaptoethanol, azobisisobutyronitrile, photosensitizer and ethyl acetate was 10mmol:65mmol:40mg:80mg:45mL, and then the ethyl acetate was removed by rotary evaporation to prepare a modified intermediate.

[0027] Synthesis of organic soft core matrix: Take the modified intermediate, triethylamine and dimethyl sulfoxide, mix them, introduce dry air until a stable gas flow is precipitated, heat to 60°C, stir at 180rpm, add γ-glycidyloxypropyltrimethoxysilane and react for 5.5h, wherein the feed ratio of the modified intermediate, γ-glycidyloxypropyltrimethoxysilane, triethylamine and dimethyl sulfoxide is 10mmol:0.15mol:10mL:80mL, then remove dimethyl sulfoxide by reduced pressure rotary evaporation to prepare an organic soft core matrix.

[0028] Composite of soft core-hard shell filler: Take organic soft core matrix and metal oxide powder, add 40% ethanol aqueous solution by volume, ultrasonically oscillate to form a uniform dispersion, add hydrochloric acid to acidify to pH 3, and rapidly stir at 240rpm for 1.5h, wherein the metal oxide powder is selected from nano alumina powder, and the feed ratio of metal oxide powder, organic soft core matrix and ethanol aqueous solution is 50g:3.5g:120mL. Then let stand to separate, remove the liquid phase, wash and dry to obtain a soft core-hard shell filler.

[0029] (2) Preparation of hard PP board Mixing and granulation: take 40wt% of the soft core-hard shell filler prepared in this embodiment; 0.8wt% of the lubricant, industrial grade calcium stearate is selected; 0.15wt% of the antioxidant, antioxidant 1010 and antioxidant 168 are mixed in equal weight ratios; the balance is PP resin, EP300H type resin raw material of Zhejiang Petrochemical is selected; first premix the PP resin, lubricant and antioxidant in a high mixer, feed them from the main feeding port of a twin-screw extruder, melt plasticize at 230±10°C, add the soft core-hard shell filler from the side feeding port, extrude and pelletize to obtain a modified masterbatch.

[0030] Compression molding: The modified masterbatch is melt-extruded, and the melt discharge temperature is controlled to be 210±5°C. The melt is extruded into a flat plate mold, hot-pressed and shaped at 20MPa, and precision-pressed to determine the thickness. During the implementation process, a 5mm thick plate is designed, and then spray-cooled and molded to obtain a blank.

[0031] Post-processing: Cut and trim the burrs on the blank plate, send it into the annealing furnace, control the annealing temperature to 120°C, and the annealing time to 10 min / mm to obtain an impact-resistant hard PP plate.

[0032] Example 3, preparing an impact-resistant hard PP plate, specifically as follows: (1) Preparation of soft core-hard shell fillers Synthesis of modified intermediates: mercaptoethanol, azobisisobutyronitrile and ethyl acetate were premixed, heated to 50°C and stirred at 120 rpm for 20 min, then polydipentaerythritol hexaacrylate and photosensitizer were added and mixed, stirred at 60 rpm at 700 mW / cm 2 The reaction was carried out under UV irradiation intensity for 1.2 hours, wherein the photosensitizer was selected from α-hydroxyketone photoinitiator 1173, and the feed ratio of polydipentaerythritol hexaacrylate, mercaptoethanol, azobisisobutyronitrile, photosensitizer and ethyl acetate was 10mmol:65mmol:50mg:80mg:50mL, and then the ethyl acetate was removed by rotary evaporation to prepare a modified intermediate.

[0033] Synthesis of organic soft core matrix: Take the modified intermediate, triethylamine and dimethyl sulfoxide, mix them, introduce dry air until a stable gas flow is precipitated, heat to 70°C, stir at 180rpm, add γ-glycidyloxypropyltrimethoxysilane and react for 5h, wherein the feed ratio of the modified intermediate, γ-glycidyloxypropyltrimethoxysilane, triethylamine and dimethyl sulfoxide is 10mmol:0.18mol:12mL:100mL, then remove dimethyl sulfoxide by reduced pressure rotary evaporation to prepare an organic soft core matrix.

[0034] Composite of soft core-hard shell filler: Take organic soft core matrix and metal oxide powder, add 40% ethanol aqueous solution by volume, ultrasonically oscillate to form a uniform dispersion, add hydrochloric acid to acidify to pH 3, and stir rapidly at 240rpm for 1.3h, wherein the metal oxide powder is selected from nano alumina powder, and the feed ratio of metal oxide powder, organic soft core matrix and ethanol aqueous solution is 50g:4.5g:130mL. Then let stand to separate, remove the liquid phase, wash and dry to obtain a soft core-hard shell filler.

[0035] (2) Preparation of hard PP board Mixing and granulation: take 32wt% of the soft core-hard shell filler prepared in this embodiment; 1wt% of the lubricant, industrial grade calcium stearate; 0.18wt% of the antioxidant, antioxidant 1010 and antioxidant 168 are mixed in equal weight ratios; the balance is PP resin, EP300H type resin raw material from Zhejiang Petrochemical; first premix the PP resin, lubricant and antioxidant in a high mixer, feed them from the main feeding port of a twin-screw extruder, melt plasticize at 230±10°C, add the soft core-hard shell filler from the side feeding port, extrude and pelletize to obtain a modified masterbatch.

[0036] Compression molding: The modified masterbatch is melt-extruded, and the melt discharge temperature is controlled to be 210±5°C. The melt is extruded into a flat plate mold, hot-pressed and shaped at 20MPa, and precision-pressed to determine the thickness. During the implementation process, a 5mm thick plate is designed, and then spray-cooled and molded to obtain a blank.

[0037] Post-processing: Cut and trim the burrs on the blank plate, send it into the annealing furnace, control the annealing temperature to 120°C, and the annealing time to 10 min / mm to obtain an impact-resistant hard PP plate.

[0038] Comparative Example 1: In this comparative example, the soft core-hard shell filler is replaced with VK-L30S type oleophilic modified nano-alumina.

[0039] Comparative Example 2, referring to Comparative Example 1, adds 5wt% of RX-9051 toughening agent to the components, premixes with PP resin, and the balance is PP resin to make up to 100wt%.

[0040] The prepared rigid PP board was subjected to relevant performance tests, specifically: tensile test according to ASTM D638-2022 standard, bending test according to ASTM D790-2017 standard, and unnotched impact test according to ASTM D256-1997 standard; the specific test results are shown in Table 1: Table 1 Tensile strength / MPa Flexural modulus / MPa <![CDATA[Impact strength / kJ·m -2 > Example 1 40.2 2070 46.5 Example 2 45.9 2255 43.2 Example 3 43.7 2140 50.7 Comparative Example 1 46.5 2215 37.9 Comparative Example 2 38.1 1780 45.0 From the test results in Table 1, it can be seen that the PP board material prepared in the embodiment has good tensile and bending strength properties, meets the use requirements of hard board materials, and the impact strength is up to 50 kJ / m 2 , with excellent impact resistance.

[0041] According to the ASTM D3763-2002 standard, the sample was subjected to high-frequency continuous impact to simulate the actual plate under repeated impact conditions. The force level was 60% of the impact strength of the above test, the impact frequency was 5 times / min, and the number of tests was 200 times. The sample after repeated impact was subjected to tensile, bending and impact tests again, and compared with the data in Table 1, the corresponding strength retention rate was calculated. The specific test results are shown in Table 2: Table 2 Tensile strength retention rate / % Flexural modulus retention rate / % Impact strength retention rate / % Example 1 91.05 80.74 84.50 Example 2 86.13 72.90 77.39 Example 3 90.47 83.15 81.96 Comparative Example 1 62.95 55.46 60.51 Comparative Example 2 80.12 63.97 69.73 It can be seen from the test results in Table 2 that after repeated impacts, the tensile, bending and impact strength retention rates of the PP board of the embodiment are maintained at a high level, showing excellent impact resistance compared with the comparative example.

[0042] Based on the above test results, the soft core-hard shell filler prepared in Example 3 was observed by electron microscope. Figure 1 As shown by Figure 1 It can be seen that the soft core-hard shell filler has uniform particle size and presents a multi-particle composite spherical structure.

[0043] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0044] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. An impact-resistant hard PP board, characterized in that: Its components are: 25-40wt% soft core-hard shell filler, 0.8-1.2wt% lubricant and 0.15-0.2wt% antioxidant, and the balance is PP resin; The preparation method of the soft core-hard shell filler is as follows: Step 1: premix mercaptoethanol, azobisisobutyronitrile and ethyl acetate and activate them by heating, then add polydipentaerythritol hexaacrylate and photosensitizer, and perform addition reaction under UV irradiation to obtain a modified intermediate; Step 2: uniformly mix the modified intermediate, triethylamine and dimethyl sulfoxide, and slowly add γ-glycidyloxypropyltrimethoxysilane under heating and stirring conditions to react with the modified intermediate to form an organic soft core matrix; Step 3: Ultrasonic dispersion of the organic soft core matrix, metal oxide powder and ethanol aqueous solution, acidification of the reaction system with hydrochloric acid, and chelation coupling of the metal oxide powder and the organic soft core matrix under ultrasonic oscillation to form a soft core-hard shell filler.

2. The impact-resistant hard PP board according to claim 1, characterized in that: The feed ratio of polydipentaerythritol hexaacrylate, mercaptoethanol, azobisisobutyronitrile, photosensitizer and ethyl acetate is 10mmol: 65-70mmol: 40-50mg: 80-100mg: 45-60mL.

3. The impact-resistant hard PP board according to claim 2, characterized in that: The photosensitizer is an α-hydroxyketone photoinitiator.

4. The impact-resistant hard PP board according to claim 2, characterized in that: The feed ratio of the modified intermediate, γ-glycidyloxypropyltrimethoxysilane, triethylamine and dimethyl sulfoxide is 10mmol: 0.15-0.2mol: 10-15mL: 80-110mL.

5. The impact-resistant hard PP board according to claim 4, characterized in that: The feed ratio of metal oxide micropowder, organic soft core matrix and ethanol aqueous solution is 50g:3.5-5g:120-150mL.

6. The impact-resistant hard PP board according to claim 5, characterized in that: The metal oxide powder is nano-scale powder.

7. A method for preparing an impact-resistant rigid PP board according to any one of claims 1 to 6, characterized in that: The details are as follows: Mixing and granulation: PP resin, lubricant and antioxidant are premixed and plasticized, and then soft core-hard shell filler is added and extruded and granulated to obtain modified masterbatch; Compression molding: The modified masterbatch is melted and extruded into a flat plate mold, and then hot-pressed, precision-pressed, and cooled to form a blank. Post-processing: Cut and trim the burrs on the blank plate, and send it into the annealing furnace for annealing and stress relief treatment to obtain an impact-resistant hard PP plate.

8. The method for preparing an impact-resistant rigid PP board according to claim 7, characterized in that: The annealing process parameters are set as follows: temperature is 120°C, annealing time is 10min / mm.

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