Polypropylene-based material synergistically modified by long-chain polypropylene and elastomer as well as preparation method and application of polypropylene-based material

Abstract

The invention discloses a polypropylene-based material synergistically modified by long-chain polypropylene and an elastomer as well as a preparation method and application of the polypropylene-based material. According to the invention, the LCBPP is adopted to carry out synergistic blending on the PP / POE blend, so that the ternary blended polypropylene-based cable main insulation material is obtained. In the ternary blending polypropylene-based cable main insulation material, the LCBPP has a long branch chain structure, so that the compatibility between the PP and the POE can be enhanced. And the LCBPP is spontaneously distributed on a PP / POE interface and plays a coupling role, so that the mechanical and dielectric properties of the material are further improved. The preparation method of the ternary blended polypropylene-based cable main insulation material is simple in process, relatively low in cost and environment-friendly, and the electrical and mechanical properties of the PP / POE blend cable main insulation material are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power material preparation, and in particular to a polypropylene-based cable main insulation material synergistically modified with long-chain polypropylene and an elastomer, and a preparation method and application thereof. Background Art

[0002] With the proposal of the "dual carbon" goal, the power system is gradually developing towards green, environmentally friendly, and recyclable. Polypropylene (PP) has gradually replaced cross-linked polyethylene (XLPE) with its excellent electrical insulation, no need for cross-linking, and recyclability, becoming the main research direction of cable insulation materials in the future. However, PP insulation materials have mechanical properties problems such as high rigidity and poor elongation at break, which cannot meet the requirements for the laying and installation of high-voltage cables. In response to this problem, the mainstream modification technology routes for cable PP insulation include grafting modification, nano-modification, and blending modification. Among them, the physical modification idea of ​​blending elastomers with PP insulation materials to improve mechanical properties has the advantages of strong economy, simple process flow, and obvious performance improvement. It is a more mature physical modification idea in engineering.

[0003] Polyolefin elastomer (POE) is the most commonly used elastomer in polypropylene blending modification. It is low in price and has excellent dielectric and mechanical properties. However, the compatibility and interfacial bonding of the two materials are poor. In particular, POE and PP will phase separate at high temperatures, thereby forming an interface. The uniformity of POE dispersion is further reduced, which reduces the mechanical properties of the blending system. In addition, due to the local relaxation of molecular segments and the increase in free volume at high temperatures, carriers can absorb more energy, thereby accelerating the insulation degradation process of the material and significantly shortening the life of the cable. Therefore, it is urgent to further improve the compatibility of polypropylene and POE.

[0004] At present, there are many reports on the improvement of the compatibility of PP and POE. Some scholars have applied β-nucleating agents to adjust the crystal form of PP / POE cable insulation and improve the compatibility between POE and PP. The results show that during the growth of PP crystals, the molecular chains in the non-crystalline region will pass through the grain boundaries to improve the compatibility. However, POE has an inhibitory effect on the nucleation efficiency of the nucleating agent, and the long-term stability of the system is poor.

[0005] Some scholars introduced ethylene-propylene multi-block copolymer compatibilizers into PP / POE blends to modify the compatibility of PP and POE. After modification, the dispersibility of POE in polypropylene was improved, and the interfacial adhesion between polypropylene and POE was enhanced. However, the introduction of the compatibilizer promoted the migration of the carrier, and the breakdown field strength of the blend was significantly reduced. In, tetravinylpyridine (4-VP) was grafted onto PP and POE, respectively, to prepare PP-g-VP / POEg-VP blends, and the mechanical properties of the blends before and after modification were compared. The experimental results show that grafting enhances the compatibility of PP and POE, thereby improving the mechanical properties of the blends. However, excessive grafting can lead to severe degradation of the PP molecular chain, which has an adverse effect on the mechanical and dielectric properties of the blend system.

[0006] In summary, great progress has been made in the experiments and mechanisms of improving the compatibility of PP and POE through nucleating agents, compatibilizers and grafting. However, there are problems such as reduced purity of insulating materials, low modification success rate and complex preparation process, which make it difficult to put into engineering application.

[0007] Therefore, it is necessary to develop an insulating material with better comprehensive performance. Summary of the invention

[0008] The object of the present invention is to provide a polypropylene-based material modified by synergistic modification of long-chain polypropylene and elastomer, and a preparation method and application thereof. The present invention adopts long-chain branched polypropylene (LCBPP) to synergistically blend PP / POE blends to obtain a ternary blended polypropylene-based cable main insulation material. LCBPP can enhance the compatibility between PP and POE due to its long branched chain structure. On the one hand, LCBPP and PP have the same segment structure, resulting in a strong interaction between PP and LCBPP. On the other hand, the chain shuttling effect between the branched chain of LCBPP and the POE molecular chain further reduces the interfacial energy, resulting in good compatibility between LCBPP and POE. LCBPP spontaneously distributes at the PP / POE interface and plays a coupling role, which is conducive to further improving the mechanical and dielectric properties of the material.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] The first aspect of the present invention is to provide a polypropylene-based material synergistically modified with long-chain polypropylene and an elastomer, wherein the material is prepared from raw materials including polypropylene, a polyolefin elastomer and long-chain branched polypropylene.

[0011] As a preferred embodiment, in the material,

[0012] The mass fraction of polypropylene (PP) is 20%-90%;

[0013] The mass fraction of polyolefin elastomer (POE) is 0.1%-50%;

[0014] The mass fraction of the long chain branched polypropylene (LCBPP) is 0.1%-50%.

[0015] In the technical solution of the present invention, for example, the mass fraction of polypropylene (PP) is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%;

[0016] For example, the mass fraction of polyolefin elastomer (POE) is 0.1%, 1, 5, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%;

[0017] For example, the mass fraction of long chain branched polypropylene (LCBPP) is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50%.

[0018] As a preferred embodiment, in the material,

[0019] The mass fraction of polypropylene (PP) is 30%-70%;

[0020] The mass fraction of polyolefin elastomer (POE) is 20%-40%;

[0021] The mass fraction of long chain branched polypropylene (LCBPP) is 2%-30%.

[0022] As a preferred embodiment, in the material,

[0023] The mass fraction of polypropylene (PP) is 50%-70%;

[0024] The mass fraction of polyolefin elastomer (POE) is 20%-40%;

[0025] The mass fraction of long chain branched polypropylene (LCBPP) is 3%-10%.

[0026] As a preferred embodiment,

[0027] The melt index of the polypropylene is 0.5 g / 10min-20 g / 10min, preferably 1 g / 10min-10 g / 10min. For example, the melt index of the polypropylene is 0.5, 1, 3, 5, 10, 15, 18, 20 g / 10min;

[0028] As a preferred embodiment,

[0029] The melt strength of the long-chain branched polypropylene is 5-200 cN; for example, 5, 10, 40, 60, 80, 100, 140, 160, 180, 200 cN; and / or,

[0030] The melt flow rate of long-chain branched polypropylene is 1-10 g / 10 min; for example, 1, 3, 5, 7, 8, 10 g / 10 min;

[0031] and / or,

[0032] The tensile strength of long-chain branched polypropylene is 30-80 MPa; for example, 30, 40, 60, 80 MPa.

[0033] As a preferred embodiment,

[0034] The electrical conductivity of the material is 3×10 -17 s / m~4×10 -13 s / m; preferably 3×10 -17 s / m~1×10 -16 s / m; for example, 3×10 -17 s / m, 1×10 -16 s / m, 1×10 -15 s / m, 1×10 -14 s / m, 1×10 -13 s / m、14×10 -13 s / m.

[0035] As a preferred embodiment,

[0036] Under power frequency, the dielectric constant of the material is 1.8-3; preferably 2.1-2.9; for example, 1.8, 2, 2.1, 2.3, 2.5, 2.7, 2.9, 3.

[0037] As a preferred embodiment,

[0038] When tested at a 1 kV field strength, the power frequency dielectric loss factor of the material is 1×10 -3 ~5×10 -2 ; preferably 1×10 -3 ~4.5×10 -2 ; For example, 1×10 -3 , 3×10 -3 , 5×10 -3 , 8×10 -3 , 1×10 -2 , 5×10 -2 .

[0039] As a preferred embodiment,

[0040] The breakdown strength of the material is 50 kV / mm to 80 kV / mm, preferably 70 kV / mm to 80 kV / mm, for example 50, 55, 60, 65, 70, 75, 80 kV / mm.

[0041] As a preferred embodiment,

[0042] The tensile strength of the material is 20 MPa to 40 MPa, preferably 35 MPa to 40 MPa, for example 20, 25, 30, 35, 40 MPa.

[0043] As a preferred embodiment,

[0044] The elongation at break of the material is 600% to 1500%, preferably 1350% to 1500%, for example 600%, 700%, 800%, 900%, 1000%, 1100%, 1200%, 1300%, 1400%, 1500%.

[0045] The second aspect of the present invention is to provide a method for preparing a polypropylene-based material synergistically modified with long-chain polypropylene and an elastomer as described in the first aspect of the present invention, comprising the following steps:

[0046] After the polypropylene, polyolefin elastomer and long-chain branched polypropylene are melt-blended, they are optionally hot-pressed into thin sheet samples; and they are cooled and crystallized to obtain the polypropylene-based material synergistically modified by the long-chain polypropylene and the elastomer.

[0047] As a preferred embodiment,

[0048] The melt blending temperature is 170-230°C, and the melt blending time is 20-40 minutes; and / or,

[0049] The cooling crystallization refers to cooling from 170°C-210°C to 110-120°C; preferably cooling from 170°C-210°C to 110-120°C within 3-60 minutes.

[0050] As a preferred embodiment,

[0051] When the step of hot pressing into a thin sheet sample is included,

[0052] The temperature of the hot pressing is 170°C-210°C; and / or,

[0053] The hot pressing pressure is 8MPa-20MPa; and / or,

[0054] The heat pressing time is 5 min-60 min.

[0055] The third aspect of the present invention is to provide a use of the polypropylene-based material synergistically modified with the long-chain polypropylene and elastomer as described in the first aspect of the present invention as the main insulating material of the cable.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] (1) The present invention proposes a preparation method for synergistically blending a long-chain polypropylene (LCBPP) with a PP / POE blend cable main insulation material, thereby obtaining a polypropylene-based cable main insulation material of a LCBPP / PP / POE ternary blend. The introduction of a long-chain branched structure improves the compatibility of PP and POE by enhancing molecular chain entanglement.

[0058] (2) The present invention proposes a preparation method for synergistically blending a long-chain polypropylene (LCBPP) with a PP / POE blend cable main insulation material, and obtains a polypropylene-based cable main insulation material of a LCBPP / PP / POE ternary blend. When the amount of LCBPP added is appropriate, the introduction of the long-chain branched structure in the LCBPP can enhance the entanglement of the PP and POE molecular chains and the intermolecular force, thereby enhancing the breakdown performance of the PP / POE blend.

[0059] (3) When the amount of LCBPP added is appropriate, the introduction of long-chain branched structures in LCBPP can reduce the conductivity of the blending system, especially the conductivity of the blending system at high temperature (90°C).

[0060] (4) When the amount of LCBPP added is appropriate, the introduction of long-chain branched structure in LCBPP can increase the compatibility of the various components in the PP / POE blended polypropylene cable material and reduce the dielectric loss of the cable main insulation system.

[0061] (5) When the amount of LCBPP added is appropriate, the longer side chains in LCBPP can be entangled with the main chain, which increases the friction resistance of the blend molecular chain during sliding, thereby improving the tensile strength and elongation at break.

[0062] (6) This method has simple process, low cost, and environmental friendliness, and effectively improves the electrical and mechanical properties of the main insulation of PP / POE blend cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 The scanning electron microscope images of the cross section of the samples of each embodiment after liquid nitrogen brittle fracture;

[0064] Figure 2 is the conductivity of the samples of each embodiment at 30°C and 90°C;

[0065] Figure 3 is the breakdown field strength of the samples of each embodiment at 30°C and 90°C;

[0066] Figure 4 The dielectric constant and loss tangent value Tanδ of the samples in each embodiment at 30°C;

[0067] Figure 5 The dielectric constant and loss tangent value Tanδ of the samples in each embodiment at 90°C;

[0068] Figure 6 The tensile strength of the samples of each embodiment;

[0069] Figure 7 Elongation at break of the samples of each example.

[0070] in, Figure 1 middle, Figure 1 (a) represents the PPO sample, Figure 1 (b) represents PP5 sample, Figure 1 (c) represents the PP10 sample, Figure 1 (d) represents the PP15 sample, Figure 1 (e) represents the PP20 sample, Figure 1 (f) represents the PP30 sample. DETAILED DESCRIPTION

[0071] The present invention is further described in detail below through the accompanying drawings and specific embodiments.

[0072] Among the raw materials used in the following examples and comparative examples of the present invention,

[0073] Polypropylene is PP polypropylene T30S, and the melt index is 3.4g / 10min;

[0074] Polyolefin elastomer (POE) is polyolefin elastomer Solumer 871L;

[0075] The preparation process of long-chain branched polypropylene (LCBPP) is as follows: propylene is polymerized with the assistance of 5-hexenylmethyldichlorosilane (hex-DCS) under a Ziegler-Natta catalyst (MgCl2 / BMMF / TiCl4 catalyst), and then deionized water is added for hydrolysis (for the specific preparation method, refer to the experimental part of the literature: Li K, Zhou HS, Qin YW, et al. ω-Alkenylmethyldichlorosilane-assisted propylene polymerization with Ziegler-Natta catalyst to long chain-branchedpolypropylene[J]. Polymer, 2020, 202: 122737). Its melt strength is 54.8 cN, the melt flow rate is 2 g / 10 min, and the tensile strength is 40 MPa.

[0076] Comparative Example 1

[0077] PP and POE were melt blended for 30 minutes at 170°C and 40 Hz using an internal mixer. Subsequently, they were hot pressed into thin sheet samples at 185°C and a pressure of 15 MPa. The thin sheet sample was cooled from 185°C to 115°C within 17 minutes for a crystallization process, and then cooled to ambient temperature to obtain a film sample. Among them, the mass ratio of POE in the ternary blend is 40%, and the mass ratio of PP and long-chain polypropylene in the ternary mixture is 60%. The mass ratio of long-chain branched polypropylene (LCBPP) in the entire ternary mixture is 0, recorded as PP0 sample.

[0078] Example 1

[0079] Linear PP, POE and LCBPP were mixed and melted in different proportions using an internal mixer at 170°C and a rotation speed of 40 Hz, and the melt blending time was 30 minutes. Subsequently, thin sheet samples were hot pressed at 185°C and a pressure of 15 MPa (the thin sheet samples in the present invention were pressed mainly to facilitate subsequent testing). The thin sheet sample was cooled from 185°C to 115°C within 17 minutes for a crystallization process, and then cooled to ambient temperature to obtain a film sample. The mass ratio of POE to the ternary blend is 40%, and the mass ratio of PP and long-chain polypropylene to the ternary mixture is 60%. The mass ratio of long-chain branched polypropylene (LCBPP) to the entire ternary mixture is 5%, recorded as PP5 sample.

[0080] Example 2

[0081] Linear PP, POE and LCBPP were mixed and melted in different proportions using an internal mixer at 170°C and a rotation speed of 40Hz, and the melt blending time was 30min. Subsequently, thin sheet samples were hot pressed at 185°C and a pressure of 15MPa. The thin sheet sample was cooled from 185°C to 115°C within 17 minutes for a crystallization process, and then cooled to ambient temperature to obtain a film sample. The mass ratio of POE in the ternary blend is 40%, and the mass ratio of PP and long-chain polypropylene in the ternary mixture is 60%. The mass ratio of long-chain branched polypropylene (LCBPP) in the entire ternary mixture is 10%, recorded as PP10 sample.

[0082] Example 3

[0083] Linear PP, POE and LCBPP were mixed and melted in different proportions using an internal mixer at 170°C and a rotation speed of 40Hz, and the melt blending time was 30min. Subsequently, thin sheet samples were hot pressed at 185°C and a pressure of 15MPa. The thin sheet sample was cooled from 185°C to 115°C within 17 minutes for a crystallization process, and then cooled to ambient temperature to obtain a film sample. The mass ratio of POE in the ternary blend is 40%, and the mass ratio of PP and long-chain polypropylene in the ternary mixture is 60%. The mass ratio of long-chain branched polypropylene (LCBPP) in the entire ternary mixture is 15%, recorded as PP15 sample.

[0084] Example 4

[0085] Linear PP, POE and LCBPP were mixed and melted in different proportions using an internal mixer at 170°C and a rotation speed of 40Hz, and the melt blending time was 30min. Subsequently, thin sheet samples were hot pressed at 185°C and a pressure of 15MPa. The thin sheet sample was cooled from 185°C to 115°C within 17 minutes for a crystallization process, and then cooled to ambient temperature to obtain a film sample. The mass ratio of POE in the ternary blend is 40%, and the mass ratio of PP and long-chain polypropylene in the ternary mixture is 60%. The mass ratio of long-chain branched polypropylene (LCBPP) in the entire ternary mixture is 20%, recorded as PP20 sample.

[0086] Example 5

[0087] Linear PP, POE and LCBPP were mixed and melted in different proportions using an internal mixer at 170°C and a rotation speed of 40Hz, and the melt blending time was 30min. Subsequently, thin sheet samples were hot pressed at 185°C and a pressure of 15MPa. The thin sheet sample was cooled from 185°C to 115°C within 17 minutes for a crystallization process, and then cooled to ambient temperature to obtain a film sample. The mass ratio of POE in the ternary blend is 40%, and the mass ratio of PP and long-chain polypropylene in the ternary mixture is 60%. The mass ratio of long-chain branched polypropylene (LCBPP) in the entire ternary mixture is 30%, recorded as PP30 sample.

[0088] Performance comparison of each embodiment and comparative example:

[0089] Microscopic morphology comparison:

[0090] The cross-sectional morphology of the PP / POE / LCBPP blended samples in each example was observed by scanning electron microscopy (SEM). Figure 1 As shown. Figure 1 It can be seen from the results that in the PPO sample of Comparative Example 1, the compatibility of PP and POE is poor, there are obvious differences in the structure and distribution of the two-phase materials of PP and POE, and the interface layer has a clear outline.

[0091] In the sample PP5 of the embodiment of the present invention, the difference in structure and distribution of the two phases of PP and POE is reduced, the interface is more blurred, and the compatibility is significantly enhanced. This shows that LCBPP plays an effective coupling role in the blend, and its molecular chain arrangement promotes the mixing and compatibility between the incompatible PP / POE blend components. However, with the increase of the LCBPP content in the PP / POE / LCBPP blend system, the interface between the PP and POE phases becomes more and more obvious, and the interfacial compatibility between the PP and POE phases deteriorates, which may be caused by the agglomeration of excessive LCBPP. The experimental results show that when the content of LCBPP exceeds 20wt%, the compatibility of PP and POE in the PP / POE / LCBPP blend system decreases most significantly.

[0092] DC conductivity performance comparison:

[0093] DC conductivity tests were conducted at different temperatures, as shown in the following table. Figure 2 As shown. Figure 2 It can be seen from the results that at 30°C, the DC conductivity of the PP5 sample is lower than that of the original sample (PP0), and the DC conductivity of the sample gradually increases with the increase of LCBPP content. The conductivity of PP5 is 1.29×10 -16S / m, which is only 46.24% of PP0. Considering that the leakage current is caused by the directional movement of mobile charges, the introduced long-chain branched structure has a reducing effect on the carrier concentration and mobility, thereby reducing the conductivity of all modified samples. In addition, it is worth noting that with the increase of LCBPP content, the conductivity of the sample increases. It can be concluded that the excessive doping of LCBPP reduces the hopping conduction distance, thereby increasing the leakage current density.

[0094] As the ambient temperature increases from 30°C to 90°C, the conductivity of all samples increases significantly, and the DC conductivity of the sample of PP5 is lower than that of the original sample (PP0). The conductivity of the unmodified sample increases by more than 1000 times. At elevated temperatures, the thermal motion of local segments within the PP molecular chain becomes more obvious, which increases the free volume and leads to enhanced carrier migration. In addition, the high temperature environment leads to an increase in the charge injection of the electrode, resulting in an increase in the carrier concentration inside the medium, which leads to an increase in conductivity. It is worth noting that even at high temperatures, the conductivity of the modified samples remains at a low level. The conductivity of PP5 is 9.09×10 -14 The S / m is only 30.39% of that of PP0. This significant difference may be attributed to the fact that the presence of long-chain branched structures limits the slippage of the molecular chains at high temperatures, thereby hindering the increase of free volume and, in turn, limiting the migration of charge carriers.

[0095] Therefore, the electrical insulation of the modified sample of the present invention at a suitable ratio is better than that of the original sample (PP0) at high temperature.

[0096] Comparison of breakdown strength performance:

[0097] The breakdown strength of the samples in various embodiments at different temperatures is as follows: Figure 3 As shown. Figure 3 It can be seen from the results that at 30 °C, the modified samples showed significantly enhanced breakdown strength compared to the original sample (PP0). PP5 showed the highest breakdown strength of 76.14 kV / mm, an increase of 23.68% compared to PP0. The introduction of long-chain branched structure has a beneficial effect on enhancing the breakdown performance by enhancing molecular chain entanglement and strengthening intermolecular forces. However, the increase in long-chain branched structure may introduce electrical weaknesses as the blending ratio increases. The homogeneity of the mixed samples decreased with the increase in LCBPP content, resulting in electric field distortion and subsequently reduced breakdown strength.

[0098] As the temperature increases, the breakdown strength of each sample shows a significant decrease, which is 7.30% to 14.42% lower than the breakdown strength at 30°C. However, all modified samples show better thermal stability. In particular, the breakdown strength of PP5 at 90°C is 70.58 kV / mm, which is 33.98% higher than that of PP0. This is attributed to the introduction of long-chain branched structures that hinder the separation of POE and PP at high temperatures, thereby improving the compatibility of POE and PP.

[0099] Comparison of dielectric constant and dielectric loss:

[0100] Figure 4 The relative dielectric constant (εr) and dielectric loss factor (tanδ) of each example sample at 30°C are shown, and the test frequency is 10-1-105Hz. Figure 4 It can be seen from the results that at the same frequency, PP0 has the lowest εr, and the slightly increased εr in the modified samples corresponds to the LCBPP content, which may be due to the higher polarity of LCBPP compared to PP. It is worth noting that at the same frequency, tanδ increases significantly with the increase of LCBPP doping content. For samples with high LCBPP content, there are a large number of interfaces between LCBPP and the PP matrix. Due to the change in εr, charge accumulation occurs at the interface, resulting in increased interface polarization losses.

[0101] Figure 5 The εr and tanδ of each example sample at 90°C are shown. Figure 5 It can be seen from the results that when the frequency is at a lower level, a significant increase in εr and tanδ is observed at 90°C compared to that at 30°C. This phenomenon may be attributed to the insufficient compatibility of PP and POE at high temperatures, which leads to an increase in the interface and thus increases the polarizability of the polymers. The εr and tanδ of PP5 remain low. The above results show that the sample doped with 5% LCBPP still has excellent dielectric properties at high temperatures.

[0102] Comparison of tensile strength and elongation at break:

[0103] Figure 6 and Figure 7 The tensile strength and elongation at break of different LCBPP doping contents are shown. Figure 6 and Figure 7It can be seen from the results that with the increase of LCBPP doping amount, the tensile strength and elongation at break first increase and then decrease. Compared with sample PP0, the average tensile strength of sample PP30 decreased from 30.79MPa to 23.57MPa, a decrease of 23.45%. In addition, the average elongation at break of sample PP30 decreased significantly, from 1164.88% to 689.88%, almost halved. However, the doping of an appropriate amount of LCBPP helps to improve the mechanical properties. In particular, the average tensile strength and elongation at break of sample PP5 are 37.09MPa and 1361.53%, respectively, which are 20.46% and 16.88% higher than those of the unmodified sample. The molecular chain of polypropylene is a linear structure, showing better flexibility. The longer side chains in LCBPP can be entangled with the main chain, which increases the friction resistance when the molecular chain slides, thereby improving the mechanical properties of the sample. However, when the LCBPP doping content is too high, the presence of long side chains may increase the distance between the molecular chains, causing the sample to be more easily deformed and broken.

[0104] In summary, the present invention uses LCBPP to synergistically blend PP / POE blends to obtain a ternary blended polypropylene-based cable main insulation material. LCBPP can enhance the compatibility between PP and POE due to its long branched chain structure. Moreover, LCBPP spontaneously distributes at the PP / POE interface and plays a coupling role, which is conducive to further improving the mechanical and dielectric properties of the material.

[0105] The above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. 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 implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A polypropylene-based material modified by long-chain polypropylene and elastomer, characterized in that: The material is prepared from raw materials including polypropylene, polyolefin elastomer and long-chain branched polypropylene.

2. The polypropylene-based material modified by synergistic long-chain polypropylene and elastomer according to claim 1, characterized in that: Among the materials, The mass fraction of polypropylene is 20%-90%; The mass fraction of polyolefin elastomer is 0.1%-50%; The mass fraction of the long-chain branched polypropylene is 0.1%-50%.

3. The polypropylene-based material modified by synergistic long-chain polypropylene and elastomer according to claim 2, characterized in that: Among the materials, The mass fraction of polypropylene is 30%-70%; The mass fraction of polyolefin elastomer is 20%-40%; The mass fraction of the long-chain branched polypropylene is 2%-30%.

4. The polypropylene-based material modified by synergistic long-chain polypropylene and elastomer according to claim 3, characterized in that: Among the materials, The mass fraction of polypropylene is 50%-70%; The mass fraction of polyolefin elastomer is 20%-40%; The mass fraction of the long-chain branched polypropylene is 3%-10%.

5. The polypropylene-based material modified by synergistic long-chain polypropylene and elastomer according to claim 1, characterized in that: The melt index of the polypropylene is 0.5 g / 10 min-20 g / 10 min, preferably 1 g / 10 min-10 g / 10 min.

6. The polypropylene-based material synergistically modified with long-chain polypropylene and elastomer according to claim 1, characterized in that: The melt strength of the long-chain branched polypropylene is 5-200 cN; and / or, The melt flow rate of the long-chain branched polypropylene is 1-10 g / 10 min; and / or, The tensile strength of long-chain branched polypropylene is 30-80 MPa.

7. The polypropylene-based material modified by synergistic long-chain polypropylene and elastomer according to claim 1, characterized in that: The electrical conductivity of the material is 3×10 -17 s / m~4×10 -13 s / m; preferably 3×10 -17 s / m~1×10 -16 s / m.

8. The polypropylene-based material modified by synergistic long-chain polypropylene and elastomer according to claim 1, characterized in that: The dielectric constant of the material is 1.8 to 3, preferably 2.1 to 2.

9.

9. The polypropylene-based material synergistically modified with long-chain polypropylene and elastomer according to claim 1, characterized in that: The power frequency dielectric loss factor of the material is 1×10 -3 ~5×10 -2 ; preferably 1×10 -3 ~4.5×10 -2 .

10. The polypropylene-based material modified by synergistic long-chain polypropylene and elastomer according to claim 1, characterized in that: The breakdown strength of the material is 50 kV / mm to 80 kV / mm, preferably 70 kV / mm to 80 kV / mm.

11. The polypropylene-based material modified by synergistic long-chain polypropylene and elastomer according to claim 1, characterized in that: The tensile strength of the material is 20 MPa to 40 MPa, preferably 35 MPa to 40 MPa.

12. The polypropylene-based material modified by synergistic long-chain polypropylene and elastomer according to claim 1, characterized in that: The elongation at break of the material is 600% to 1500%, preferably 1350% to 1500%.

13. A method for preparing a polypropylene-based material synergistically modified with long-chain polypropylene and an elastomer as claimed in any one of claims 1 to 12, characterized in that: The following steps are involved: After the polypropylene, polyolefin elastomer and long-chain branched polypropylene are melt-blended, they are optionally hot-pressed into thin sheet samples; and they are cooled and crystallized to obtain the polypropylene-based material synergistically modified by the long-chain polypropylene and the elastomer.

14. The method for preparing a polypropylene-based material synergistically modified with long-chain polypropylene and an elastomer according to claim 13, characterized in that: The melt blending temperature is 170-230°C, and the melt blending time is 20-40 minutes; and / or, The cooling crystallization refers to cooling from 170°C-210°C to 110-120°C; preferably cooling from 170°C-210°C to 110-120°C within 3-60 minutes.

15. The method for preparing a polypropylene-based material synergistically modified with long-chain polypropylene and an elastomer according to claim 13, characterized in that: When the step of hot pressing into a thin sheet sample is included, The temperature of the hot pressing is 170°C-210°C; and / or, The hot pressing pressure is 8MPa-20MPa; and / or, The heat pressing time is 5 min-60 min.

16. Use of a polypropylene-based material synergistically modified with a long-chain polypropylene and an elastomer as claimed in any one of claims 1 to 12 as a main insulating material for a cable.

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