CN114986771A - Processing method for simultaneously improving elongation at break and dielectric strength of polypropylene cable material - Google Patents
Processing method for simultaneously improving elongation at break and dielectric strength of polypropylene cable material Download PDFInfo
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- CN114986771A CN114986771A CN202210509760.XA CN202210509760A CN114986771A CN 114986771 A CN114986771 A CN 114986771A CN 202210509760 A CN202210509760 A CN 202210509760A CN 114986771 A CN114986771 A CN 114986771A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
- B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
- B29C43/32—Component parts, details or accessories; Auxiliary operations
- B29C43/58—Measuring, controlling or regulating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
- B29C43/32—Component parts, details or accessories; Auxiliary operations
- B29C43/58—Measuring, controlling or regulating
- B29C2043/5808—Measuring, controlling or regulating pressure or compressing force
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
- B29C43/32—Component parts, details or accessories; Auxiliary operations
- B29C43/58—Measuring, controlling or regulating
- B29C2043/5816—Measuring, controlling or regulating temperature
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
- B29K2023/10—Polymers of propylene
- B29K2023/12—PP, i.e. polypropylene
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
Abstract
The invention discloses a processing method for simultaneously improving the elongation at break and the dielectric strength of a polypropylene cable material, which is a thermal field induced forming processing method and comprises the following steps: calculating and weighing polypropylene cable material sample granules to be processed according to the volume of the mould and the density of the polypropylene cable material, and paving the polypropylene cable material sample granules on the mould; preheating the die paved with the polypropylene cable material sample granules; performing compression molding treatment on the polypropylene cable material sample granules subjected to preheating treatment until a sample forms a film; after the pressure of the processed film forming sample is increased, the film forming sample is continuously subjected to compression molding treatment and then cooled to room temperature, so that a film sample is obtained; and drying the film sample and cooling to room temperature to prepare the polypropylene cable material with the elongation at break and the dielectric strength simultaneously improved. The elongation at break of the treated polypropylene cable material can be improved by about 50%, the alternating current breakdown strength can be improved by about 35%, and the polypropylene cable material has important value for optimizing and improving the polypropylene cable insulation processing technology.
Description
Technical Field
The invention belongs to the technical field of insulating materials for power cables, and particularly relates to a processing method for simultaneously improving the elongation at break and the dielectric strength of a polypropylene cable material.
Background
The common thermoplastic power cable insulation materials at present comprise polyethylene, ethylene propylene rubber, polypropylene-based compound and the like. The polyethylene and the ethylene propylene rubber have lower softening temperature and cannot meet the requirement of high-temperature environment of the high-voltage cable for a long time in the long-distance and large-capacity power transmission process, so that the polypropylene-based composite material becomes the main research direction of a new-generation environment-friendly cable insulating material.
Common polypropylene-based composites include polypropylene/elastomer blends, polypropylene/elastomer/nanofiller blends, polypropylene/surface graft modified nanoparticle blends, directly synthesized impact co-polypropylene, and the like. Among them, polypropylene/elastomer blends can achieve optimization of polypropylene high modulus, but tend to cause a decrease in dielectric strength. The polypropylene-based composite material containing the nano particles can optimize the mechanical property and simultaneously provide guarantee for the dielectric strength, but no better solution is provided for the agglomeration problem of the nano particles when the cable is extruded actually, particularly on a high-voltage-grade cable with a thicker insulating layer, the agglomeration phenomenon is particularly prominent, and the cable is difficult to be applied practically. The direct-synthesized impact-resistant co-polypropylene can realize the remarkable optimization of tensile modulus, but due to the complexity of an aggregation structure, the dielectric strength of the impact-resistant co-polypropylene is greatly influenced by thermal history, and a unified hot processing method aiming at the direct-synthesized impact-resistant co-polypropylene cable material is not formed at present.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a treatment method for simultaneously improving the elongation at break and the dielectric strength of a polypropylene cable material, which can effectively and pertinently solve the technical problems of low elongation at break and low dielectric strength of impact-resistant co-polypropylene directly synthesized under the conventional processing process conditions.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
the invention discloses a processing method for simultaneously improving the elongation at break and the dielectric strength of a polypropylene cable material, which comprises the following steps:
1) calculating and weighing polypropylene cable material sample granules to be processed according to the volume of the mould and the density of the polypropylene cable material, and flatly paving the polypropylene cable material sample granules on the mould;
2) preheating the die paved with the polypropylene cable material sample granules;
3) performing compression molding treatment on the polypropylene cable material sample granules subjected to preheating treatment until a sample forms a film;
4) after the pressure of the film forming sample obtained by the step 3) is increased, continuing compression molding treatment, and then cooling to room temperature to obtain a film sample;
5) and drying the film sample and cooling to room temperature to prepare the polypropylene cable material with the elongation at break and the dielectric strength simultaneously improved.
Preferably, in the step 1), the polypropylene cable material is an ethylene-propylene copolymer polypropylene cable material, and the base material of the polypropylene cable material comprises a polypropylene-based phase, an ethylene-propylene block copolymer phase and an ethylene-propylene rubber phase.
Preferably, in step 1), the mold size is 100mm × 100mm × 1 mm.
Preferably, in the step 2), the temperature of the preheating treatment is 190-210 ℃, and the treatment time is 4-6 min.
Further preferably, the temperature of the preheating treatment is 200 ℃ and the treatment time is 5 min.
Preferably, in step 3), the compression molding treatment is to treat the sample pellets under a pressure of 5MPa for 5min, during which the venting operation of the opening and closing press is performed once, and then to treat the sample pellets under a pressure of 10MPa for 5min, during which the venting operation of the opening and closing press is performed once again.
Preferably, in the step 4), the pressure is increased to 15Mpa, the temperature is kept at 180-220 ℃, compression molding treatment is carried out for 20-40 min, and the mixture is cooled to room temperature through circulating cooling water.
Further preferably, the pressure is raised to 15MPa, the temperature is maintained at 200 ℃ and the compression molding treatment is carried out for 30 min.
Preferably, in the step 5), the drying treatment is carried out for 10-18 h at 70-90 ℃; the cooling is to cool to room temperature under the natural state.
Further preferably, the drying treatment is carried out at 80 ℃ for 12 hours.
Compared with the prior art, the invention has the following beneficial effects:
the processing method for simultaneously improving the elongation at break and the dielectric strength of the polypropylene cable material disclosed by the invention is a thermal field induced molding processing method, and compared with the traditional crosslinked polyethylene cable insulating material, the polypropylene-based cable material to be processed has the advantages of high melting temperature, excellent dielectric property, environmental protection, recyclability and the like; the heat treatment method adopted by the process is simple and easy to operate, and the cooperative optimization of electrical and mechanical properties can be realized through the heat treatment under different states, so that the heat treatment method is convenient for large-scale application in the actual production of cable lines; meanwhile, the method can fill the blank of the process parameters in the post-treatment stage of the polypropylene-based cable. The elongation at break of the treated polypropylene cable material can be improved by about 50%, the alternating current breakdown strength can be improved by about 35%, and the polypropylene cable material has important value for optimizing and improving the polypropylene cable insulation processing technology.
Furthermore, after the compression molding film forming link is finished, the pressure of the flat plate compression molding machine is increased to 15MPa, and the compression molding treatment is carried out again, because the insulated interior of the impact-resistant co-polypropylene generally comprises a polypropylene matrix, an ethylene-propylene block copolymer and an ethylene-propylene random copolymer, wherein the dispersion uniformity of the ethylene-propylene random copolymer is an important factor for determining the breaking elongation and the dielectric strength of the impact-resistant co-polypropylene. In the impact copolymerization polypropylene granules, part of the ethylene-propylene block copolymer and the ethylene-propylene random copolymer cannot be completely separated, so that the dispersibility uniformity of the ethylene-propylene random copolymer is poor. The stretching and the electric breakdown belong to weak point damage, and the uneven dispersion of the ethylene-propylene random copolymer in the material can cause the reduction of the elongation at break and the dielectric strength. After the compression molding film forming link is finished, the pressure is increased for compression molding again, the separation of the ethylene-propylene random copolymer from the matrix can be promoted, and the increase of the pressure can avoid agglomeration among the separated ethylene-propylene random copolymer to a certain extent, so that the ethylene-propylene random copolymer is uniformly dispersed in the polypropylene matrix in a small size, and the effect of enhancing the elongation at break and the dielectric strength is achieved.
Further, the cooled film sample is placed in a vacuum oven, the temperature is set to be 80-90 ℃, the sample is taken out after being processed for 12-18h and is cooled to room temperature in a natural state, the cooling rate of circulating water after compression molding is high, and a perfect crystal structure is generally difficult to form in the sample. The heat treatment at a certain temperature is helpful for further perfecting the crystal structure, and simultaneously, the perfection of the crystal structure can fix the dispersed ethylene propylene random copolymer phase, avoid the agglomeration of the dispersed ethylene propylene random copolymer phase under external stress to form the structural defect, and further improve the effects of the elongation at break and the dielectric strength of the impact-resistant copolymerized polypropylene.
Drawings
FIG. 1 is a comparison of elongation at break of examples of the present invention and comparative examples;
FIG. 2 is a comparison of the AC breakdown strength of the examples of the present invention and the comparative examples.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is described in further detail below with reference to the accompanying drawings:
the polypropylene cable materials used in the embodiments and the comparative examples of the invention are all Yanshan petrochemical K8303 impact-resistant co-polypropylene.
Example (b):
the sample preparation method comprises the following specific steps:
(1) the size of the mould is 100mm multiplied by 1mm, and after the required sample granules are calculated and weighed according to the volume of the mould and the density of the sample, the sample is flatly paved on the mould, and the uniform distribution of the sample is ensured as much as possible. And (3) placing the die on a flat plate compression molding machine for preheating, wherein the preheating temperature is set to be 200 ℃, and the preheating time is 5 min. And after preheating, applying pressure of 5MPa for compression molding, wherein the compression molding time is 5min, performing primary air exhaust operation of the opening and closing press, then increasing the pressure to 10MPa for compression molding, wherein the compression molding time is 5min, and performing primary air exhaust operation of the opening and closing press again.
(2) After the compression molding film forming link is finished, the pressure of a flat plate compression molding machine is increased to 15MPa, the temperature is kept at 200 ℃, the flat plate compression molding machine is taken out after 30min of compression molding, and then the flat plate compression molding machine is cooled to the room temperature through circulating water.
(3) And (3) placing the cooled film sample in a vacuum oven, setting the temperature to be 80 ℃, treating for 12h, taking out the sample, and cooling to room temperature in a natural state.
Comparative example 1
(1) The size of the mould is 100mm multiplied by 1mm, and after the required sample granules are calculated and weighed according to the volume of the mould and the density of the sample, the sample is flatly paved on the mould, and the uniform distribution of the sample is ensured as much as possible. And (3) placing the die on a flat plate compression molding machine for preheating, wherein the preheating temperature is set to be 200 ℃, and the preheating time is 5 min. And after preheating, applying pressure of 5MPa for compression molding, wherein the compression molding time is 5min, performing primary air exhaust operation of the open-close press during the compression molding, then increasing the pressure to 10MPa for compression molding, wherein the compression molding time is 5min, performing primary air exhaust operation of the open-close press during the compression molding, and cooling to room temperature by circulating water.
Comparative example 2
(1) The size of the mould is 100mm multiplied by 1mm, and after required sample granules are calculated and weighed according to the volume of the mould and the density of the sample, the sample is flatly paved on the mould, and the uniform distribution of the sample is ensured as much as possible. And (3) placing the die on a flat plate compression molding machine for preheating, wherein the preheating temperature is set to be 200 ℃, and the preheating time is 5 min. And after preheating, applying pressure of 5MPa for compression molding, wherein the compression molding time is 5min, performing primary air exhaust operation of the opening and closing press, then increasing the pressure to 10MPa for compression molding, wherein the compression molding time is 5min, and performing primary air exhaust operation of the opening and closing press again.
(2) After the compression molding film forming link is finished, the pressure of a flat plate compression molding machine is increased to 15MPa, the temperature is kept at 200 ℃, the flat plate compression molding machine is taken out after 30min of compression molding, and then the flat plate compression molding machine is cooled to room temperature through circulating water.
The performance test method comprises the following steps:
(1) mechanical property test methods were performed according to ASTM D638, and sheet specimens of about 1mm thickness were processed into standard dumbbell-shaped bars using a punch machine. The neck region is 4mm wide and 20mm long. The test was carried out using a Meits CMT-4503 electronic universal tensile tester, with a tensile rate set at 50 mm/min.
(2) Breakdown strength tests were carried out with reference to the standard IEC 60243. The power frequency alternating current breakdown experiment is carried out by adopting an HJC-100kV type computer control voltage breakdown experiment instrument, a ball-ball electrode is used for the experiment, the material is brass, the diameter of the electrode is 20mm, the experiment environment is room temperature, the whole experiment process is carried out in transformer oil, the boosting rate is set to be 2kV/s, and the thickness of a sample is about 1 mm.
The experimental results are shown in fig. 1 and 2:
as can be seen in fig. 1 and 2, the elongation at break and the breakdown strength of the three samples are, in order from small to large: comparative example 1, comparative example 2, and examples. The compression molding treatment is performed after the compression molding link is finished, so that the elongation at break and the breakdown strength of the material are favorably improved, because the phase separation and the stability in the impact-resistant co-polypropylene need longer time, the further compression molding treatment provides conditions for the phase separation and the stability in the material, a phase structure which is more favorable for the elongation at break and the breakdown strength is formed in the material, and the elongation at break and the breakdown strength are further promoted to be improved. The elongation at break and the breakdown strength of the material can be further improved by carrying out heat treatment on the basis of secondary compression molding, and the heat treatment can promote the perfection of the crystal structure in the impact-resistant co-polypropylene, improve the crystallinity and enhance the stability of a phase structure, so that the elongation at break and the breakdown strength are further improved.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (10)
1. A processing method for simultaneously improving the elongation at break and the dielectric strength of a polypropylene cable material is characterized by comprising the following steps:
1) calculating and weighing polypropylene cable material sample granules to be processed according to the volume of the mould and the density of the polypropylene cable material, and paving the polypropylene cable material sample granules on the mould;
2) preheating the die paved with the polypropylene cable material sample granules;
3) performing compression molding treatment on the polypropylene cable material sample granules subjected to preheating treatment until a sample forms a film;
4) after the pressure of the film forming sample obtained by the processing in the step 3) is increased, the film forming sample is continuously subjected to compression molding, and then the film forming sample is cooled to room temperature to obtain a film sample;
5) and drying the film sample and cooling to room temperature to prepare the polypropylene cable material with the elongation at break and the dielectric strength simultaneously improved.
2. The processing method for simultaneously improving the elongation at break and the dielectric strength of a polypropylene cable material according to claim 1, wherein in the step 1), the polypropylene cable material is an ethylene-propylene copolymer polypropylene cable material, and the base material of the polypropylene cable material comprises three phases of a polypropylene-based phase, an ethylene-propylene block copolymer phase and an ethylene-propylene rubber phase.
3. The processing method for simultaneously improving the elongation at break and the dielectric strength of a polypropylene cable material according to claim 1, wherein in the step 1), the mold size is 100mm x 1 mm.
4. The processing method for simultaneously improving the elongation at break and the dielectric strength of the polypropylene cable material according to claim 1, wherein the preheating treatment temperature in the step 2) is 190-210 ℃ and the treatment time is 4-6 min.
5. The treatment method for simultaneously increasing the elongation at break and the dielectric strength of a polypropylene cable material according to claim 4, wherein the temperature of the preheating treatment is 200 ℃ and the treatment time is 5 min.
6. The processing method for simultaneously improving the elongation at break and the dielectric strength of the polypropylene cable material according to claim 1, wherein in the step 3), the compression molding process comprises processing the sample pellets under a pressure of 5MPa for 5min, performing a venting operation of the open-close press during the processing, increasing the pressure to 10MPa for 5min, and performing a venting operation of the open-close press again during the processing.
7. The processing method for simultaneously improving the elongation at break and the dielectric strength of the polypropylene cable material according to claim 1, wherein in the step 4), the pressure is increased to 15MPa, the temperature is kept at 180-220 ℃, the compression molding treatment is carried out for 20-40 min, and the polypropylene cable material is cooled to room temperature by circulating cooling water.
8. The process of claim 7, wherein the pressure is increased to 15MPa, the temperature is maintained at 200 ℃, and the compression molding treatment is carried out for 30 min.
9. The processing method for simultaneously improving the elongation at break and the dielectric strength of the polypropylene cable material according to claim 1, wherein in the step 5), the drying treatment is carried out at 70-90 ℃ for 10-18 h; the cooling is to cool to room temperature under the natural state.
10. The processing method for simultaneously improving the elongation at break and the dielectric strength of the polypropylene cable material according to claim 9, wherein the drying process is carried out at 80 ℃ for 12 h.
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| CN112873670A (en) * | 2020-12-23 | 2021-06-01 | 天津大学 | Polypropylene film insulation characteristic improving method based on crystallization morphology regulation and control |
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| US5281376A (en) * | 1990-10-12 | 1994-01-25 | Sumitomo Chemical Company, Limited | Method for producing polypropylene resin article having skin material lined with foamed layer |
| EP1800769A1 (en) * | 2005-12-22 | 2007-06-27 | Abb Research Ltd. | Press die with a contactless power supply, production system comprising same and method for supplying electrical power to said die |
| CN102115558A (en) * | 2010-12-29 | 2011-07-06 | 四川大学 | High-conductivity polymer carbon nanotube composite material and micro-processing method thereof |
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