A polypropylene composite and its preparation method and application

Abstract

The present invention relates to a polypropylene composite and a preparation method and application thereof. The polypropylene composite comprises the following components: polypropylene resin, polyamide resin, compatibilizer, glass fiber, silicone, epoxy resin, nucleating agent and stabilizer. The polypropylene composite has a small change rate of elongation at break before and after thermal oxidative aging, meeting the use requirements of corresponding scenarios (e.g., materials for cooling systems).

Description

Technical Field

[0001] The present invention relates to the technical field of modified plastics, and more specifically to a polypropylene composite and a preparation method and application thereof. Background Art

[0002] With the development of the automobile industry towards new energy, lightweighting has become one of the main development trends of automobile manufacturers. On this basis, the development trend of automobile materials is also lightweight, mainly including thin-walled, low-density, plastic-to-steel and engineering plastic olefinization. For engineering plastic olefinization materials, glass fiber reinforced polypropylene is one of the most important candidate materials. Glass fiber reinforced polypropylene has the characteristics of low density, excellent mechanical properties and low cost, and has been widely used in automotive functional parts. However, parts in the engine compartment such as cooling systems and air intake systems still face some difficulties, among which the most important difficulty is to enhance the thermal oxidative aging performance of polypropylene. Patent CN104927193B uses a compound compatibilizer and an acrylic copolymer to prepare a reinforced polypropylene, and the thermal oxidative aging performance retention rate of 150℃ / 1000h can be above 85%; CN110016182B prepares a long glass fiber reinforced polypropylene material that is resistant to aging and precipitation, and the thermal oxidative aging performance retention rate of 120℃ / 1000h is above 80%. These patents can prepare materials with good thermal oxidative aging performance, which can be applied to automobiles and other fields. However, the evaluation of thermal oxidative aging performance in these patents is limited to appearance evaluation or conventional mechanical evaluation (such as tensile strength, flexural strength / flexural modulus, notched impact strength), and no research has been conducted on the evaluation of elongation at break.

[0003] Elongation at break is one of the indicators that characterize the cracking performance of materials. Since there are many factors affecting the elongation at break and the test results fluctuate greatly, many OEMs do not put forward indicator requirements for the size of the elongation at break of the material, but put forward technical requirements for the change of the elongation at break of the material, such as technical requirements for the retention rate of the elongation at break after thermal oxidative aging; especially for materials used in cooling systems, such as low-temperature water chambers, expansion tanks, water manifolds, etc., OEMs require that the change rate of elongation at break of the material before and after thermal oxidative aging at 150℃ / 1000h is ≤15%, because only when the change rate of elongation at break before and after thermal oxidative aging is within this range, can it be said that the performance stability of the parts made of the material is good under the corresponding conditions, thereby ensuring the safety of the parts during use. So far, no relevant research has been conducted to solve this problem.

[0004] Therefore, it is necessary to develop relevant technologies to solve the current problem of large change rate of elongation at break of glass fiber reinforced polypropylene before and after thermal oxidative aging, so as to meet the needs of automobile OEMs. Summary of the invention

[0005] The primary purpose of the present invention is to overcome the problem that the elongation at break of glass fiber reinforced polypropylene before and after thermal oxidative aging has a large change rate, and to provide a polypropylene composite.

[0006] A further object of the present invention is to provide a method for preparing the above polypropylene composite.

[0007] A further object of the present invention is to provide application of the polypropylene compound in functional parts of automobiles.

[0008] The above-mentioned object of the present invention is achieved by the following technical solutions:

[0009] A polypropylene composite comprises the following components in parts by weight:

[0010]

[0011] The glass fiber of the polypropylene composite has a retention length D90 of 980-1250 μm, a retention length D10 of 360-460 μm, and a difference (D90-D10) between the retention length D90 and the retention length D10 of ≤800 μm.

[0012] The invention uses polypropylene resin as a matrix, and adds a stabilizer, a nucleating agent and an epoxy resin, wherein the stabilizer imparts a certain thermal oxidative aging resistance to the polypropylene composite; the nucleating agent imparts uniform crystallization performance to the polypropylene resin matrix, so that the stabilizer can be evenly distributed in the polypropylene resin matrix, thereby making the thermal oxidative aging resistance of the polypropylene composite more uniform; and the epoxy group of the epoxy resin can absorb free radicals, thereby further improving the thermal oxidative aging resistance of the polypropylene composite.

[0013] The addition of epoxy resin has another effect: epoxy resin is a substance containing polar groups, while polypropylene resin is a non-polar substance. The two can form initiation points to trigger fracture during the elongation at break test. The initiation effect remains unchanged before and after thermal oxidative aging, thereby reducing the change rate of elongation at break before and after thermal oxidative aging to a certain extent. However, simply adding epoxy resin cannot significantly reduce the change rate of elongation at break before and after thermal oxidative aging, and cannot significantly reduce the change rate of elongation at break.

[0014] The inventor of the present invention has found through many studies that by further adding silicone and polyamide resin and controlling the difference between the retention length D90 and D10 of the glass fiber within a specific range, the change rate of the elongation at break of the polypropylene composite can meet the requirement of ≤15%. The reason is that silicone is a high molecular substance with siloxy groups and has a lubricating effect, which can improve the lubricity of the polypropylene composite, and can also form an initiation point with the polypropylene resin during the elongation at break test to induce fracture, and the effect of the initiation effect before and after the thermal oxidative aging remains unchanged, thereby reducing the change rate of the elongation at break before and after the thermal oxidative aging; polyamide resin is a polar substance, which can form an initiation point with the non-polar polypropylene resin during the elongation at break test to induce fracture, and the polyamide resin can make the initiation point uniformly dispersed in the polypropylene composite, thereby making the change of the elongation at break before and after the thermal oxidative aging more uniform; and controlling the difference between the retention length D90 and D10 of the glass fiber within a specific range can avoid the support effect formed by the larger part of the glass fiber retention length, and can also avoid the defect of poor reinforcement effect of the smaller part of the glass fiber retention length, thereby maintaining the stability of the elongation at break.

[0015] That is, the present invention combines stabilizers, nucleating agents, epoxy resins, polyamide resins and silicones, as well as the difference between the glass fiber retention lengths D90 and D10, so that the change rate of the elongation at break of the polypropylene composite before and after thermal oxidative aging is less than 15%, meeting the use requirements of corresponding scenarios (such as materials for cooling systems).

[0016] In the present invention, the polypropylene resin is used as the main resin, and its content is at least 30% of the mass of the polypropylene composite.

[0017] Optionally, the melt flow rate of the polypropylene resin measured at 230° C. and 2.16 kg is 0.5 to 60 g / 10 min.

[0018] Preferably, the melt flow rate of the polypropylene resin measured at 230° C. and 2.16 kg is 0.5 to 12 g / 10 min.

[0019] When the melt flow rate is in the range of 0.5 to 12 g / 10 min, the change rate of the elongation at break of the obtained polypropylene composite before and after thermal oxidative aging is smaller.

[0020] The melt flow rate of the polypropylene resin of the present invention can be measured according to GB / T 3682-2018.

[0021] Optionally, the polypropylene resin is a homopolymer polypropylene resin.

[0022] Optionally, the relative viscosity of the polyamide resin is 2.45-2.8.

[0023] Optionally, the polyamide resin includes but is not limited to at least one of polyamide 6, polyamide 66, polyamide 610 or polyamide 6T.

[0024] The relative viscosity of the polyamide resin of the present invention can be measured in accordance with GB / T 1632-2008 under the condition of 96% concentrated sulfuric acid solution at 25°C.

[0025] Optionally, the silicone is at least one of dimethyl polysiloxane or vinyl polysiloxane.

[0026] Optionally, the epoxy resin includes but is not limited to at least one of bisphenol A epoxy resin, bisphenol F epoxy resin or polyphenol epoxy resin.

[0027] Optionally, the epoxy equivalent of the epoxy resin is 160 to 500 g / eq.

[0028] Preferably, the epoxy equivalent of the epoxy resin is 160 to 280 g / eq.

[0029] By selecting epoxy resin with epoxy equivalent of 160-280 g / eq, the change rate of elongation at break of the obtained polypropylene composite before and after thermal oxidative aging is smaller.

[0030] The epoxy equivalent of the epoxy resin of the present invention can be measured according to the method of GB / T 4612-2008.

[0031] Preferably, the nucleating agent is an organic salt nucleating agent.

[0032] Optionally, the organic salt nucleating agent is at least one of organic carboxylates or organic phosphates.

[0033] Further optionally, the organic carboxylate is at least one of disodium bicyclo[2,2,1]heptane-2,3-dicarboxylate, cadmium bicyclo[2,2,1]-5-heptene-2,3-dicarboxylate, or hydroxyaluminum bis(p-tert-butylbenzoate).

[0034] Further optionally, the organic phosphate is at least one of sodium phenylphosphinate, sodium phenyl phosphite, sodium 2,2'-methylene-bis(4,6-di-tert-butylphenyl) phosphate, basic 2,2'-methylene-bis(4,6-di-tert-butylphenyl phosphate) aluminum or bis[2,2'-methylene-bis(4,6-di-tert-butylphenyl)]aluminum phosphate.

[0035] Optionally, the glass fiber is chopped E glass round fiber, chopped E7 glass round fiber or chopped E glass flat fiber.

[0036] Preferably, the chopped length of the glass fiber is 3 to 4.5 mm; the diameter of the cross section is 4 to 32 μm.

[0037] Preferably, the difference between the retention length D90 and the retention length D10 of the glass fiber is 550-800 μm.

[0038] Optionally, the compatibilizer is maleic anhydride grafted polyolefin.

[0039] Further optionally, the maleic anhydride grafted polyolefin includes but is not limited to at least one of maleic anhydride grafted POE or maleic anhydride grafted polypropylene.

[0040] Further optionally, the maleic anhydride grafting rate of the maleic anhydride grafted polyolefin is 0.4-1.5%.

[0041] Preferably, the stabilizer is composed of a hindered phenol antioxidant, a phosphite antioxidant, a thioether antioxidant and a metal passivator in a mass ratio of (1-2):(1-2):(1-2):1.

[0042] Optionally, the hindered phenol antioxidant includes but is not limited to at least one of 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione or 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene.

[0043] Optionally, the phosphite antioxidant includes but is not limited to at least one of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite or bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0044] Optionally, the thioether antioxidant includes but is not limited to at least one of pentaerythritol tetrakis (3-laurylthiopropionate), distearyl thiodipropionate or didodecyl thiodipropionate.

[0045] Optionally, the metal passivator includes but is not limited to at least one of N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, 1,2-bis(3,5-di-tert-butyl-4-hydroxy-phenylpropionic acid)hydrazine, THANOX MD-697 (2,2-oxalylamino-bis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate) or ADK STAB CDA-1 (3-salicylicylamido-1,2,4-triazole).

[0046] Preferably, the polypropylene compound further comprises 0.4 to 2 parts of other additives.

[0047] Optionally, the other auxiliary agent is at least one of a lubricant or a toner.

[0048] Optionally, the lubricant includes but is not limited to at least one of zinc stearate, erucamide or calcium stearate.

[0049] Optionally, the color powder includes but is not limited to at least one of titanium dioxide, carbon black or titanium yellow.

[0050] Preferably, the polypropylene composite comprises the following components in parts by weight:

[0051]

[0052] The method for preparing the above-mentioned polypropylene composite optionally includes the following steps: mixing other components except glass fiber to obtain a mixture; adding the mixture from the main feed port of the extruder, adding the glass fiber from the side feed port of the extruder, melt-extruding, and granulating to obtain the polypropylene composite.

[0053] A person skilled in the art can adjust the degree of shearing experienced by the glass fiber by various means, so as to control the difference between the retention length D90 and the retention length D10 (D90-D10) of the glass fiber in the polypropylene composite to be below 800 μm, for example, a certain amount of glass fiber can be added to the feed ports at different positions of the extruder, or glass fibers of different lengths can be added to the feed ports at different positions, or glass fibers can be added in the form of glass fiber masterbatch, etc.

[0054] Preferably, by adding a certain amount of glass fiber from different side feed ports, the difference (D90-D10) between the retention length D90 and the retention length D10 of the glass fiber in the polypropylene compound can be conveniently controlled to be below 800 μm, and the process is relatively simpler. Optionally, the glass fiber is added from the first side feed port and the second side feed port of the twin-screw extruder, the mass ratio of the glass fiber added from the first side feed port to the second side feed port is 1:(1-2), the first side feed port is located at the 3rd to 6th section of the barrel, and the second side feed port is located at the 7th to 10th section of the barrel.

[0055] The application of the above polypropylene compound in the preparation of automotive functional parts also falls within the protection scope of the present invention.

[0056] Preferably, the automobile functional part is an expansion tank, a water manifold or a low-temperature water chamber.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] The present invention reduces the rate of change of the elongation at break of the polypropylene composite before and after thermal oxidative aging by combining a stabilizer, a nucleating agent, an epoxy resin, a polyamide resin and a silicone as well as the difference between the retention lengths D90 and D10 of the glass fiber, thereby meeting the use requirements of corresponding scenarios (e.g., materials for a cooling system). DETAILED DESCRIPTION

[0059] In order to more clearly and completely describe the technical solution of the present invention, the present invention is further described in detail through specific embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention. Various changes can be made within the scope of the rights of the present invention.

[0060] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0061] Polypropylene resin 1#: homopolymer polypropylene resin, B1101, melt flow rate of 0.5 g / 10 min at 230 °C and 2.16 kg, Taiwan Chemical Fiber;

[0062] Polypropylene resin 2#: homopolymer polypropylene resin, PP T30S, melt flow rate at 230°C, 2.16kg is 2.6g / 10min, Lanzhou Petrochemical;

[0063] Polypropylene resin 3#: homopolymer polypropylene resin, PP 6012, melt flow rate of 12 g / 10 min at 230 °C and 2.16 kg, Tianjin United;

[0064] Polypropylene resin 4#: homopolymer polypropylene resin, PP H9018, melt flow rate of 60 g / 10 min at 230 °C and 2.16 kg, Lanzhou Petrochemical;

[0065] Polyamide resin 1#: PA6, M2400, Xinhui Meida, relative viscosity is 2.45;

[0066] Polyamide resin 2#: PA6, M2800, Xinhui Meida, relative viscosity is 2.8;

[0067] Compatibilizer: Maleic anhydride grafted POE, KT-915, Shenyang Ketong, grafting rate 1.0%;

[0068] Glass fiber: ECS13-04-508A, chopped E glass round fiber, chopped length 4.0mm, cross-sectional diameter 13μm, Jushi glass fiber;

[0069] Silicone 1#: dimethyl polysiloxane, Shanghai Jizhi;

[0070] Silicone 2#: Vinyl polysiloxane, Shanghai Jizhi;

[0071] Epoxy resin 1#: CYD-011, bisphenol A type epoxy resin, epoxy equivalent weight 450-500g / eq, Sinopec;

[0072] Epoxy resin 2#: DER354, bisphenol F type epoxy resin, epoxy equivalent weight is 164-174g / eq, DOW;

[0073] Epoxy resin 3#: E-42, bisphenol A type epoxy resin, epoxy equivalent weight 230-280g / eq, Bluestar New Materials;

[0074] Nucleating agent 1#: organic carboxylates, sodium (1R,2R,3S,4S)-rel-bicyclo[2.2.1]heptane-2,3-dicarboxylate, HPN-68L, Milliken;

[0075] Nucleating agent 2#: organic phosphate, 2,2'-methylene-bis(4,6-di-tert-butylphenyl phosphate) basic aluminum, NA-21, Aidico;

[0076] Stabilizer 1#: composed of a hindered phenol antioxidant, a phosphite antioxidant, a thioether antioxidant, and a hydrazide metal passivator in a mass ratio of 1:1:1:1, wherein the hindered phenol antioxidant is 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid, the thioether antioxidant is pentaerythritol tetrakis(3-laurylthiopropionate), the phosphite antioxidant is bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, and the hydrazide metal passivator is N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, all of which are commercially available products;

[0077] Stabilizer 2#: The difference from stabilizer 1# is that it is composed of hindered phenol antioxidant, phosphite antioxidant, thioether antioxidant and hydrazide metal passivator in a mass ratio of 2:2:2:1.

[0078] Other additives 1#: lubricant, zinc stearate, commercially available;

[0079] Other additives 2#: color powder, carbon black, commercially available;

[0080] Unless otherwise specified, the components (such as compatibilizer) selected in each parallel embodiment and comparative example are the same commercially available products.

[0081] The properties of the polypropylene composites provided in the embodiments and comparative examples of the present invention were measured according to the following test methods:

[0082] The polypropylene compound was injection molded into test specimens, and each embodiment and comparative example was divided into group A and group B. The test specimens of group A were tested after conditioning for 24 hours under standard conditions (23±2°C, 50±5%RH), and the test was carried out according to GB / T 1040-2008 for initial elongation at break, with a tensile rate of 10mm / min and a clamp spacing of 50mm. The test specimens of group B were placed in a 150°C oven for 1000 hours, taken out, and conditioned for 24 hours under standard conditions (23±2°C, 50±5%RH), and then tested according to GB / T1040-2008 for elongation at break after thermal oxidation aging, with a tensile rate of 10mm / min and a clamp spacing of 50mm.

[0083] The calculation formula for the change rate of elongation at break is: change rate of elongation at break = (initial elongation at break - elongation at break after thermal oxidation aging) / initial elongation at break * 100%.

[0084] Retention length of glass fiber: The test method adopts ISO 22314-2006.

[0085] The polypropylene composites of Examples 1 to 15 of the present invention are prepared by the following preparation method:

[0086] Weigh each component according to the formula; add the other components except glass fiber to a high mixer and mix them evenly to obtain a mixture; add the mixture to the main feed port of a twin-screw extruder, and add the glass fiber from the first side feed port and the second side feed port of the twin-screw extruder, wherein the mass ratio of the glass fiber added from the first side feed port to the second side feed port is 1:1; perform melt extrusion and granulation at 180-230°C to obtain a polypropylene compound. The first side feed port is located at the 3rd to 6th section of the barrel, and the second side feed port is located at the 7th to 10th section of the barrel.

[0087] Generally speaking, the retention length of the fixed length of glass fiber added to each feeding port after screw shearing shows a wide normal distribution, and the difference between the retention length D90 and the retention length D10 is large. Adjusting the screw shearing alone will change the retention length D90 and D10 of the glass fiber, and increase or decrease at the same time, but the change range of D90 is much larger than that of D10. According to this principle, in order to control the difference between the retention length D90 and the retention length D10 of the glass fiber to be small, the glass fiber can be separated for side feeding. The glass fiber of the first feeding port passes through a stronger screw shearing, which reduces the value of the retention length D90 of the glass fiber, while the glass fiber of the second feeding port passes through a weaker screw shearing, which increases the value of the retention length D10 of the glass fiber, and finally achieves the purpose of the difference between the retention length D90 and the retention length D10 of the glass fiber (D90-D10) ≤ 800μm.

[0088] Examples 1 to 15

[0089] Examples 1 to 15 provide a series of polypropylene compounds, whose formulations are shown in Tables 1 and 2.

[0090] Table 1 Formulas of Examples 1 to 7 (parts by weight)

[0091]

[0092]

[0093] Table 2 Formulations of Examples 8 to 15 (parts by weight)

[0094]

[0095] Example 16

[0096] This embodiment provides a polypropylene composite, and its preparation method and formula are basically the same as those of Example 1, except that: in the preparation method, the mass ratio of the glass fiber added from the first side feeding port to the second side feeding port is 1:2.

[0097] Embodiment 17

[0098] This embodiment provides a polypropylene compound, and its formula is basically the same as that of embodiment 1, except that: 70 parts of polypropylene resin 1# are first divided into first polypropylene resin 1# (30 parts) and second polypropylene resin 1# (40 parts); then other components except glass fiber, polyamide and first polypropylene resin 1# are added to a high mixer for uniform mixing, and then added to the main feed port of a twin-screw extruder; glass fiber is added from the second side feed port of the twin-screw extruder, and extruded to obtain glass fiber masterbatch; finally, polyamide resin and second polypropylene resin 1# are added to a high mixer for uniform mixing, and then added to the main feed port of the twin-screw extruder, and the above glass fiber masterbatch is added to the second side feed port, and melt extrusion and granulation are performed at 180-230°C to obtain a polypropylene compound. In this embodiment, glass fiber is first made into glass fiber masterbatch, and then melt extrusion granulation of the polypropylene compound is performed, and the difference (D90-D10) between the retention length D90 and the retention length D10 of the glass fiber can also be controlled to be ≤800μm.

[0099] Comparative Example 1

[0100] This comparative example provides a polypropylene composite, the preparation method and formulation of which are substantially the same as those of Example 1, except that no polyamide resin 1# is added.

[0101] Comparative Example 2

[0102] This comparative example provides a polypropylene composite, and its preparation method and formula are basically the same as those of Example 1, except that: silicone 1# is not added.

[0103] Comparative Example 3

[0104] This comparative example provides a polypropylene composite, and its preparation method and formula are basically the same as those of Example 1, except that: epoxy resin 1# is not added.

[0105] Comparative Example 4

[0106] This comparative example provides a polypropylene composite, and its preparation method and formula are basically the same as those of Example 1, except that: no nucleating agent 1# is added.

[0107] Comparative Example 5

[0108] This comparative example provides a polypropylene composite, whose preparation method and formulation are basically the same as those of Example 1, except that all glass fibers are added to the first side feed port of the twin-screw extruder.

[0109] The properties of the polypropylene composites of the embodiments and comparative examples were measured according to the above-mentioned test methods. The test results are shown in Table 3.

[0110] Table 3 Performance test results of polypropylene composites of various embodiments and comparative examples

[0111]

[0112]

[0113] From Table 3, we can see that:

[0114] The change rate of the elongation at break of the polypropylene composites of Examples 1 to 17 before and after thermal oxidative aging is less than 15%, indicating that the polypropylene composite of the present invention can solve the problem of the large change rate of the elongation at break of the polypropylene composite before and after thermal oxidative aging through the combination of various components, and meet the corresponding usage requirements.

[0115] In Comparative Examples 1 to 4, no polyamide resin, silicone, epoxy resin and nucleating agent are added respectively, and the change rate of the elongation at break of the polypropylene composite before and after thermal oxidative aging is large, which cannot meet the requirement of a change rate of less than 15%; the difference between the glass fiber retention length D90 and D10 of the polypropylene composite material of Comparative Example 5 is improperly regulated (greater than 800 μm), and the change rate of the elongation at break of the polypropylene composite after thermal oxidative aging is too large, which cannot meet the requirement of a change rate of less than 15%.

[0116] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A polypropylene composite, characterized in that The composition comprises the following components in parts by weight: 41~92 parts of polypropylene resin, 2~10 parts of polyamide resin, Compatibilizer 2~8 parts, Glass fiber 5~40 parts, Silicone 0.5~2 parts, Epoxy resin 0.1~1 part, Nucleating agent 0.1~0.5 parts, Stabilizer 0.6~2 parts; The glass fiber of the polypropylene composite has a retention length D90 of 980-1250 μm, a retention length D10 of 360-460 μm, and a difference between the retention length D90 and the retention length D10 (D90-D10) ≤ 800 μm; The retention length of glass fiber is measured using ISO 22314-2006.

2. The polypropylene composite according to claim 1, characterized in that: The melt flow rate of the polypropylene resin measured at 230° C. and 2.16 kg is 0.5-60 g / 10 min.

3. The polypropylene composite according to claim 1, characterized in that: The relative viscosity of the polyamide resin is 2.4-2.

8.

4. The polypropylene composite according to claim 1, characterized in that: The epoxy equivalent of the epoxy resin is 160-500 g / eq.

5. The polypropylene composite according to claim 1, characterized in that: The nucleating agent is an organic salt nucleating agent.

6. The polypropylene composite according to claim 1, characterized in that: The difference between the retention length D90 and the retention length D10 of the glass fiber is 550-800 μm.

7. The polypropylene composite according to claim 1, characterized in that: The polypropylene compound further comprises 0.2 to 0.8 parts of other additives.

8. The polypropylene composite according to claim 1, characterized in that: The polypropylene composite comprises the following components in parts by weight: Polypropylene resin 56~83 parts, 4-8 parts of polyamide resin, 3~6 parts of compatibilizer, Glass fiber 10~30 parts, Silicone 0.7~1.5 parts, Epoxy resin 0.3~0.7 parts, Nucleating agent 0.2~0.3 parts, Stabilizer 0.8~1.6 parts.

9. The method for preparing the polypropylene composite according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: mixing other components except glass fiber to obtain a mixture; adding the mixture from a main feeding port of an extruder, adding glass fiber from a first side feeding port and a second side feeding port of a twin-screw extruder, melting and extruding, and granulating to obtain the polypropylene composite; the mass ratio of the glass fiber added from the first side feeding port to the second side feeding port is 1:(1-2).

10. Use of the polypropylene compound according to any one of claims 1 to 8 in the preparation of automotive functional parts.

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