CN112646329A

CN112646329A - Carbon fiber reinforced PBT composite material for laser welding and composite molded body

Info

Publication number: CN112646329A
Application number: CN202011327574.1A
Authority: CN
Inventors: 严兵; 吴世超; 祁震; 张永喜; 张德胜; 唐许; 张可可; 施刘生; 张继维
Original assignee: Jiangsu Aosheng Composite Materials Hi Tech Co ltd
Current assignee: Jiangsu Aosheng Composite Materials Hi Tech Co ltd
Priority date: 2020-11-24
Filing date: 2020-11-24
Publication date: 2021-04-13
Anticipated expiration: 2040-11-24
Also published as: CN112646329B

Abstract

The invention relates to a carbon fiber reinforced PBT composite material for laser welding and a composite forming body, wherein the PBT composite material comprises the following components in parts by weight: 100 parts of polybutylene terephthalate; 1-100 parts of carbon fiber; 20-80 parts of polycarbonate; 10-40 parts of polyacrylic resin. According to the invention, the polybutylene terephthalate and the carbon fiber are mixed, and the polycarbonate and the polyacrylic resin are combined, so that the laser transmittance of the PBT composite material is improved, and the dispersion state of the carbon fiber in the PBT composite material is changed, so that the advantages and characteristics of the polybutylene terephthalate and the carbon fiber are retained, and finally, the PBT composite material has the characteristics of high tensile strength, high heat resistance (load temperature), good laser welding property and high laser welding strength. And the PBT composite material has a simple formula.

Description

Carbon fiber reinforced PBT composite material for laser welding and composite molded body

Technical Field

The invention belongs to the technical field of composite materials, and particularly relates to a carbon fiber reinforced PBT composite material for laser welding and a composite forming body.

Background

The laser welding is an efficient precision welding method using a laser beam with high energy density as a heat source, can replace the technical scheme of using adhesive for combination, and has the advantages of three-dimensional connection, non-contact processing and no adhesive overflow.

Polybutylene terephthalate (PBT) has excellent and balanced moldability, mechanical strength, heat resistance, insulation properties, and the like, and is widely used in the fields of automobiles, electric parts, and the like.

Laser welding has been applied to the adhesion of polybutylene terephthalate resins. However, the polybutylene terephthalate resin has a low laser transmittance, and therefore, the welding strength of the laser-welded portion of the polybutylene terephthalate resin is low compared to other resins with the same thickness.

The prior art has been studied to improve the weld strength of a laser welded portion of polybutylene terephthalate resin. For example, chinese patent publication No. CN101735577A discloses a polybutylene terephthalate material with high weld mark strength and its preparation method, wherein the material comprises the following components by weight percent: (1) 30-90% of polybutylene terephthalate resin; (2) 5-50% of glass fiber treated by surface treatment agent; (3) 0.5-5% of mineral filler treated with a surface treatment agent; (4) 0.5-25% of other additives. According to the preparation method, polybutylene terephthalate (PBT) resin is used as a matrix, and the viscosity of a disperse phase is improved through the ingenious combination of a mineral filler, a surface modifier and glass fibers, so that the orientation of a polybutylene terephthalate (PBT) molecular chain and the glass fibers along the vertical flow direction is hindered, and a high weld mark strength reinforced polybutylene terephthalate (PBT) material is obtained. However, the addition of glass fiber to PBT improves the welding strength of the material, but the mechanical properties and heat resistance of the material of the patent still need to be improved.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an improved PBT composite material for laser welding, which has excellent comprehensive properties of heat resistance, weldability, welding strength, mechanical strength and the like.

The invention also provides a composite molded body.

In order to achieve the purpose, the invention adopts the technical scheme that:

the PBT composite material for laser welding comprises the following raw material components in parts by weight:

the polybutylene terephthalate, also known as polytetramethylene terephthalate, PBT for short, is a polyester prepared by polycondensation of terephthalic acid and 1, 4-butanediol. Is a milky translucent to opaque, semi-crystalline thermoplastic polyester. It has low friction coefficient, high heat resistance, toughness, fatigue resistance, self-lubricating property and weather resistance, can work for a long time at 140 ℃ and has organic solvent resistance. Because of these excellent properties, they are widely used in the fields of automobiles, mechanical equipment, precision instrument parts, electronic and electrical appliances, textiles, and the like.

Carbon fiber is a special fiber composed of carbon elements. The graphite fiber has the characteristics of high temperature resistance, friction resistance, electric conduction, heat conduction, corrosion resistance and the like, is fibrous and soft in appearance, can be processed into various fabrics, and has high strength and modulus along the fiber axis direction due to the preferred orientation of the graphite microcrystalline structure along the fiber axis. The carbon fibers have a low density and thus a high specific strength and a high specific modulus. The carbon fiber in the PBT composite material mainly plays a role in increasing the strength and the heat resistance.

Polycarbonates are high molecular weight polymers containing carbonate groups in the molecular chain. The polycarbonate is colorless and transparent, heat-resistant, impact-resistant and flame-retardant at BI level, and has good mechanical properties at common use temperature. Compared with polymethyl methacrylate with similar performance, the polycarbonate has good impact resistance, high refractive index and good processability, and has flame retardance without additives. In the present invention, the polycarbonate serves to increase the strength of the composite material and also to improve the laser transmissivity of the composite material. In addition, the inventor also finds that the addition of polycarbonate can influence the dispersion of carbon fibers in the composite material, and can further improve the welding strength.

Polyacrylic resins are a generic term for polymers of acrylic acid, methacrylic acid and derivatives thereof. Examples thereof include sodium polyacrylate, polyacrylic acid, polymethacrylic acid, and polymethylmethacrylate. In the present invention, the polyacrylic resin can improve the laser transmittance of the composite material together with the polycarbonate, and influence the dispersion of the carbon fibers in the composite material, thereby further improving the weld strength.

Preferably, the carbon fibers have an average length of not more than 1 mm; when the average length of the carbon fibers is greater than 1mm, the laser weldability of the composite material is significantly reduced.

Preferably, the weight part of the carbon fiber is 40-80 parts. The proper amount of carbon fiber has obvious help for enhancing the heat resistance of the composite material, the carbon fiber is too little, and the enhancement of the heat resistance of the composite material has no significance; the carbon fiber is excessive, and the laser weldability of the composite material is reduced.

Preferably, the polycarbonate is 30 to 50 parts by weight; the weight portion of the polyacrylic resin is 15-25 portions. Proper amount of polycarbonate and polyacrylic resin has obvious effect on improving the viscosity of the disperse phase of the composite material, and improving the laser welding property and the welding strength. Too high or too low a weight fraction of polycarbonate and polyacrylic resin may result in a composite with reduced properties.

Preferably, the load temperature of the polybutylene terephthalate is 50-58 ℃; further preferably, the load temperature of polybutylene terephthalate is 55 ℃. The load temperature of polybutylene terephthalate is too high, and the laser welding property is poor; the load temperature of the polybutylene terephthalate is too low, and the heat resistance of the composite material is poor.

Preferably, the loading temperature of the polycarbonate is 121-126 ℃, and more preferably, the loading temperature of the polycarbonate is 123 ℃. The polycarbonate has too high load temperature and poor laser weldability; the load temperature of the polycarbonate is too low, and the heat resistance of the composite material is poor.

Preferably, the loading temperature of the polyacrylic resin is 85-95 ℃, more preferably 86 ℃, and the laser weldability and heat resistance of the composite material can be affected by the too high or too low loading temperature of the polyacrylic resin.

According to some preferred embodiment aspects of the invention, the raw material formula of the PBT composite material further comprises an organic salt, wherein the organic salt is 0.01-1 part by weight; further preferably, the weight part of the organic salt is 0.3-0.5; still more preferably, the organic salt is 0.4 parts by weight.

The organic salt is a salt formed by neutralizing an organic acid. In the composite material, the organic salt plays a catalytic role, so that the ester exchange of each polymer can be promoted, the crystallinity is reduced, and the laser solubility is improved. When the organic salt is too little, the catalytic efficiency is low; when the organic salt is excessive, waste is caused and the cost is increased.

The organic salt may include salts of various carboxylic acids and sulfonic acids, but it is preferable that the organic salt is one or more of sodium salt, iron salt, zinc salt, and manganese salt having 4 or more carbon atoms, in view of each component of the composite material of the present invention; further preferably, the organic salt is one or more of sodium caprylate, ferric stearate, zinc palmitate and manganese isooctanoate; still more preferably, the organic salt is a compound of zinc palmitate and manganese isooctanoate in a weight ratio of 3: 1.

According to some preferred embodiments of the invention, the raw material formula of the PBT composite material comprises the following components in parts by weight:

in the aspect of a preferred embodiment, the raw material formula of the PBT composite material comprises the following components in parts by weight:

the carbon fiber reinforced PBT composite material suitable for laser welding of the present invention can be molded by a known general thermoplastic resin molding method such as injection molding, extrusion molding, blow molding, etc., and injection molding and extrusion molding are preferred.

According to another technical scheme, the invention provides a composite molded body, which comprises the PBT composite material.

Preferably, the composite molded body is formed by laser welding of the carbon fiber reinforced PBT composite material.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

according to the invention, the polybutylene terephthalate and the carbon fiber are mixed, and the polycarbonate and the polyacrylic resin are combined, so that the laser transmittance of the PBT composite material is improved, and the dispersion state of the carbon fiber in the PBT composite material is changed, so that the advantages and characteristics of the polybutylene terephthalate and the carbon fiber are retained, and finally, the PBT composite material has the characteristics of high tensile strength, high heat resistance (load temperature), good laser welding property and high laser welding strength. And the PBT composite material has a simple formula.

Detailed Description

Compared with the prior art that glass fiber is added into polybutylene terephthalate, the invention discovers that the modified polybutylene terephthalate modified by adding carbon fiber has more advantages of high strength, heat resistance and the like. However, the addition of carbon fibers to glass fibers reduces the adhesive strength of the laser-welded portions of the polybutylene terephthalate resin. Through further research, the inventors of the present invention found that when carbon fibers are added to polybutylene terephthalate, the use of polycarbonate and polyacrylic resin in combination can maintain the advantageous characteristics of PBT and carbon fibers, and also provide a PBT composite material with characteristics of high tensile strength, high heat resistance (load temperature), good laser weldability, high adhesive strength at laser-welded parts, and the like.

The technical solutions of the present invention are described in detail below with reference to specific examples so that those skilled in the art can better understand and implement the technical solutions of the present invention, but the present invention is not limited to the scope of the examples.

The following examples used the following starting materials and their sources:

[ polybutylene terephthalate ]

A1: toray 1401X06, manufactured by Toray corporation, load temperature 60 ℃.

A2: toraycon 5201X10, manufactured by Toray corporation, load temperature 55 ℃.

A3: toraycon 5201X11, manufactured by Toray corporation, load temperature 50 ℃.

[ carbon fiber ]

B: MLD-300, manufactured by Toray corporation, had an average length of 130 μm.

[ polycarbonate ]

C1: panlite SS-2430, Kitiki Kabushiki Kaisha, load temperature 120 ℃.

C2: panlite SS-2525, Kitiki Kabushiki, load temperature 123 ℃.

C3: panlite SS-2525, Kitiki Kaisha, load temperature 125 ℃.

[ polyacrylic acid resin ]

D1: acryset VH, Mitsubishi chemical corporation, load temperature 100 ℃.

D2: acrypt IRH50, Mitsubishi chemical corporation, load temperature 93 ℃.

D3: acrypt IRH50, Mitsubishi chemical, load temperature 86 ℃.

[ organic salts ]

E1: national chemical group chemical agents ltd, sodium caprylate.

E2: chemical reagents of national medicine group, ltd, iron stearate.

E3: the mixture of zinc palmitate and manganese isooctanoate is prepared by the national drug group chemical reagent company Limited, and the weight ratio of the zinc palmitate to the manganese isooctanoate is 3: 1.

Example 1

The raw material formula of the carbon fiber reinforced PBT composite material for laser welding provided in this example is shown in table 1.

The preparation method comprises the following steps: according to the formula, the raw material components are put into a double-screw extruder, a sheet-shaped object is continuously extruded through a die orifice of the extruder, and the sheet-shaped object is obtained after cooling, wherein the temperature of each section of screw is controlled to be 200-270 ℃.

The raw material formulas of the PBT composite materials for laser welding provided by the embodiments 2-12 and the comparative examples 1-4 are shown in the table 1, and the preparation method of the materials is the same as that of the embodiment 1.

Table 1 shows the raw material formulas of PBT composite materials of examples 1 to 12 and comparative examples 1 to 4

The PBT composite materials of examples 1-12 and comparative examples 1-4 were subjected to the following performance tests, and the results are shown in Table 2:

(1) tensile strength

The test method comprises the following steps: the evaluation was carried out by the method of ASTM D638 standard, ASTM D638 being mainly to apply a tensile force to a specimen and to measure its mechanical properties under stress. It is carried out on an electronic universal tester (also called tensile tester) at a tensile speed ranging from 1 to 500 mm/min until the sample fails (yields or breaks).

Sample parameters: the composites of examples 1-12 and comparative examples 1-4 were made into class I flat plate samples 3.2mm thick, 165mm long, 13mm wide, 50mm gauge length.

(2) Temperature of load

The test method comprises the following steps: the evaluation is carried out by adopting a method of ASTM D648 standard, which comprises the following steps:

2.1) measuring the height and width of the sample for multiple times within the span range, and taking an average value;

2.2) placing the sample side on a support;

2.3) ensuring that the sphere of the thermometer or the sensing part of the temperature sensor is close to the sample as much as possible, and fully stirring within 10mm to ensure that the temperature difference of the medium within 10mm around the sample is less than 1.0;

2.4) applying a load to the sample, immersing the sample in a hot bath;

2.5) continuously adding weights to ensure that the bending stress born by the sample is (0.455MPa or 1.82 MPa);

2.6) after applying the load for 5min, the reading of the deflection measuring device is adjusted to zero or the reading is recorded. Heating the heat transfer medium at the speed of (2 +/-0.2)/min;

2.7) record the temperature of the heat transfer medium at a specimen deflection of 0.25 mm.

Sample parameters: the composite materials of examples 1 to 12 and comparative examples 1 to 4 were prepared into test pieces having a length of 127mm, a width of 13mm and a thickness of 10 mm.

(3) Laser weldability

The test method comprises the following steps: the test was carried out using a laser instrument from LEISTER corporation, a laser wavelength of 940nm, a maximum output of 35W, a focal length L of 38mm, a focal diameter D of 0.6mm, and a laser scanning speed of 1-40 mm/sec. The case where the laser beam transmitted through the sample had a lint mark on the light incident surface is indicated by "x", and the case where no lint mark was present and welding was possible was indicated by "o".

Sample parameters: the composites of examples 1-12 and comparative examples 1-4 were made into 3mm thick test specimens.

(4) Laser welding strength

The test method comprises the following steps: the laser-welded sample in test (3) was subjected to a tensile test using a tensile tester (AG-500B) at a tensile speed of 1mm/min and a pitch of 40mm, and 5 cycles of measurement were taken as the average value of the laser welding strengths.

Table 2 shows the results of the performance tests of the composite materials of examples 1 to 12 and comparative examples 1 to 4

As can be seen from the results in Table 2, the tensile strengths of examples 1-12 are 155-187MPa, the tensile strengths of comparative examples 1-4 are 56-145MPa, the tensile strength of the carbon fiber reinforced PBT composite material provided by the invention is obviously optimized, the tensile strength of comparative example 1 is only 56MPa, probably because comparative example 1 is only polybutylene terephthalate, and the tensile strengths of comparative examples 2-4 are obviously lower than those of examples 1-12 probably because a part of the components are absent. The components and the parts by weight of the components of the carbon fiber reinforced PBT composite material provided by the invention are strictly screened, and the components have synergistic effects.

The load temperatures for examples 1-12 were 209-219 deg.C, while the load temperatures for comparative examples 1-4 were 67-204 deg.C. The composite temperature of the carbon fiber reinforced PBT composite material provided by the invention is obviously optimized, the load temperature of comparative example 1 is only 67MPa, probably because the comparative example 1 only contains polybutylene terephthalate, and the load temperature of comparative examples 2-4 is obviously lower than that of examples 1-12 probably because a part of components are lacked. The components and the parts by weight of the components of the carbon fiber reinforced PBT composite material provided by the invention are strictly screened, and the components have synergistic effects.

Examples 1 to 12 all had laser welding performed, and the welding strength was 38 to 56 MPa. Comparative example 2 could not be laser welded, and comparative examples 1, 3, and 4 had weld strengths of only 36MPa, 25MPa, and 18MPa, although laser welding could be performed.

In conclusion, the carbon fiber reinforced PBT composite materials prepared by the components and the parts by weight of the invention in examples 1-12 have obvious advantages in tensile strength, load temperature, laser weldability and laser welding strength compared with comparative examples 1-4.

Further analyzing the test results of Table 2, the four test results of example 5 are all the best, wherein the tensile strength is 187MPa, the load temperature is 219 ℃, and the laser welding strength is 56 MPa; next, in example 10, the tensile strength was 179MPa, the load temperature was 217 ℃ and the laser welding strength was 52 MPa; example 11, tensile strength 183MPa, load temperature 219 ℃, laser welding strength 50 MPa; example 12 had a tensile strength of 181MPa, a load temperature of 216 ℃ and a laser welding strength of 55 MPa. The advantage of the test results of examples 5, 10, 11, 12 indicates that it can be a more preferred option for carbon fiber reinforced PBT composites.

Examples 11 and 12 differed from example 5 only in the loading temperature of the polycarbonate, that is, the loading temperature of the polycarbonate of example 11 was 125 ℃, the loading temperature of the polycarbonate of example 12 was 120 ℃, the loading temperature of the polycarbonate of example 5 was 123 ℃, and it was found that the optimum loading temperature of the polycarbonate was 123 ℃. The polycarbonate had an excessively high temperature under load and had poor laser weldability (example 11); the polycarbonate load temperature was too low and the PBT composite had poor heat resistance (example 12).

Further, the test results of examples 1 to 12 were compared with the test results of publication Nos. CN101735577A and CN 1690121A. The high weld mark strength reinforced polybutylene terephthalate material disclosed in the publication number CN101735577A has the tensile strength of 130-135MPa and the laser welding strength of 55-61 MPa. The colored resin composition for laser welding disclosed in publication No. CN1690121A has a tensile strength of 124-140MPa, a load temperature of 201-209 ℃ and a laser welding strength of 37-38 MPa. Therefore, the carbon fiber reinforced PBT composite material disclosed by the embodiments 1-12 of the invention has obvious advantages in tensile strength, load temperature, laser weldability and laser welding strength.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

Claims

1. The PBT composite material for laser welding is characterized by comprising the following raw material components in parts by weight:

100 parts of polybutylene terephthalate;

1-100 parts of carbon fiber;

20-80 parts of polycarbonate;

10-40 parts of polyacrylic resin.

2. The PBT composite for laser welding according to claim 1, wherein: the carbon fibers have an average length of not more than 1 mm.

3. The PBT composite for laser welding according to claim 1, wherein: the addition amount of the carbon fiber is 40-80 parts.

4. The PBT composite for laser welding according to claim 1, wherein: the addition amount of the polycarbonate is 30-50 parts; the addition amount of the polyacrylic resin is 15-25 parts.

5. The PBT composite for laser welding according to claim 1, wherein: the load temperature of the polybutylene terephthalate is 50-58 ℃, the load temperature of the polycarbonate is 121-126 ℃, and the load temperature of the polyacrylic resin is 85-95 ℃.

6. The PBT composite for laser welding according to claim 1, wherein: the PBT composite material also comprises 0.01-1 part of organic salt.

7. The PBT composite material for laser welding according to claim 6, wherein: the organic salt is one or more of sodium salt, ferric salt, zinc salt and manganese salt with more than 4 carbon atoms.

8. The PBT composite for laser welding according to claim 7, wherein: the organic salt is one or a combination of more of sodium caprylate, ferric stearate, zinc palmitate and manganese isooctanoate.

9. The PBT composite material for laser welding according to claim 6, wherein: the PBT composite material comprises the following raw material components in parts by weight:

100 parts of polybutylene terephthalate;

40-80 parts of carbon fiber;

30-50 parts of polycarbonate;

15-25 parts of polyacrylic resin;

0.01-1 part of organic salt.

10. A composite molded body, characterized in that: the composite molded body comprises the PBT composite material according to any one of claims 1 to 9.