CN108327301B

CN108327301B - Method for laser welding of plastics

Info

Publication number: CN108327301B
Application number: CN201810069385.5A
Authority: CN
Inventors: 张洪吉; 宋雨方; 东为富; 马丕明; 施冬健; 李小杰; 陈明清
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2018-01-24
Filing date: 2018-01-24
Publication date: 2020-10-30
Anticipated expiration: 2038-01-24
Also published as: CN108327301A

Abstract

The invention discloses a method for laser welding plastics, which comprises the following steps: (1) applying water to the area to be welded of the plastic to be welded to keep the surfaces to be welded of the plastic to be welded in close contact; (2) and irradiating the area to be welded by adopting a laser, namely completing the welding of the plastic. The invention takes water as a welding agent (photo-thermal conversion carrier), does not need to be doped with any other light absorption filler or pigment, achieves the purposes of green, environmental protection, no toxicity, no harm and the like in the real sense, and has great application value in the fields of food packaging, medical appliances, welding of precise and complex plastic parts and the like.

Description

Method for laser welding of plastics

Technical Field

The invention relates to the technical field of laser welding, in particular to a method for welding plastics by laser.

Background

Laser welding of plastics has become a new endeavor in the field of welding. With laser welded plastics, the material must be laser light absorbing. In a general laser transmission welding method, a suitable light absorber is generally applied to the contact surface of two parts to be welded or a suitable filler or pigment is previously doped in the lower-layer welded part to be used as the light absorber, and then welding is completed. Carbon black, as a commonly used light absorber, has high photothermal conversion efficiency, but also causes the welding surface or the welding part to have to be dyed; on the other hand, some non-staining commercial cleaning light absorbers are either expensive or present a safety risk, and their application fields are limited.

Disclosure of Invention

In view of the above problems of the prior art, the applicant of the present invention provides a method for laser welding plastics. The invention realizes the purpose of welding by melting (softening) the contact surface of the plastic to be welded through the photo-thermal conversion action of water. The invention takes water as a welding agent (photo-thermal conversion carrier), does not need to be doped with any other light absorption filler or pigment, achieves the purposes of green, environmental protection, no toxicity, no harm and the like in the real sense, and has great application value in the fields of food packaging, medical appliances, welding of precise and complex plastic parts and the like.

The technical scheme of the invention is as follows:

a method of laser welding plastic, the method comprising the steps of:

(1) applying water to the area to be welded of the plastic to be welded to keep the surfaces to be welded of the plastic to be welded in close contact;

(2) and irradiating the area to be welded by adopting a laser, namely completing the welding of the plastic.

The plastic to be welded in the step (1) is thermoplastic plastic, thermoplastic elastomer or a mixture of the thermoplastic plastic and the thermoplastic elastomer.

The melting point of the plastic is less than or equal to 100 ℃.

The plastic is one or more of EVA, EAA, PEG, PVC, PVAc, PCL, PU, PHA polyester, PPC and PCL/PU composite material.

The application mode in the step (1) is spraying, brushing, wiping or rolling.

The amount of water applied in step (1) is not less than 2. mu.l/cm²。

And (3) the laser wavelength emitted by the laser in the step (2) is 1.2-2.9 μm.

The plastic is pretreated by performing frosting treatment on the surface of the plastic to make the surface rough.

The plastic is in the shape of a film, a sheet, a plate, a pipe, a special-shaped section or a precise complex plastic part.

The beneficial technical effects of the invention are as follows:

the invention creatively uses water with the most extensive source in nature as a medium for energy conversion to further realize the laser welding of plastics, uses water as a welding agent (photo-thermal conversion carrier), does not need to be doped with any other light absorption filler or pigment, achieves the purposes of green, environmental protection, no toxicity, no harm and the like in the true sense, and has great application value in the fields of food packaging, medical appliances, the welding of precise and complex plastic parts and the like.

The invention uses water as a photo-thermal conversion carrier, the water temperature is rapidly raised by the light energy absorbed by the water, the water temperature can reach 100 ℃ at most, the plastic with the melting point or the softening point less than or equal to 100 ℃ is softened, the plastic melts (softens) and expands in volume to flow in the welding process, and the water is extruded out from the welding contact area spontaneously (or can apply a certain force), thereby achieving the purpose of welding.

Drawings

FIG. 1 is a schematic view of a lap joint welding process of the present invention;

FIG. 2 is a schematic view of a butt joint welding process of the present invention;

FIG. 3 is a schematic view showing samples before and after welding in example 1 of the present invention;

fig. 4 is a stress-strain curve of the sample before and after welding in example 1 of the present invention.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings and examples.

Example 1

A method for laser welding plastic parts comprises using polycaprolactone (T) with molecular weight of 50000g/mol and thickness of 0.2mm_m60 ℃ C. for the example of welding, the method comprises the following steps:

(1) brushing the area to be welded of the two plastic parts with 10 mul/cm²The water is butted with the joint and keeps the close contact of the joint surfaces to be welded;

(2) and (3) irradiating the welding area by using a laser with the wavelength of 1470nm, adjusting the output power of the laser to be 0.5W, melting the welding area after 5s, forming a melting surface with the size of a facula after 10s, then closing the laser, naturally cooling and solidifying to form a welding area, and finishing welding.

The samples before and after welding were respectively cut into dumbbell shapes, and tensile tests were performed, wherein the samples before testing are shown in fig. 3, and fig. 4 is a stress-strain curve of the samples before and after welding at room temperature.

From fig. 3, it can be seen that the comparison of the welded sample with the original sample shows a flat welded surface without severe burn.

As can be seen from FIG. 4, the mechanical properties of the welded sample are basically unchanged from those of the original sample, the tensile strength of the original sample is 40.87MPa, the elongation at break is about 1800%, the tensile strength of the welded sample is 43.88MPa, the elongation at break is about 1900%, and the welding efficiency is nearly 100%.

Example 2

A method for laser welding plastic parts, such as Polycaprolactone (PCL) plastic parts with a molecular weight of 50000g/mol and a thickness of 1mm, comprising the steps of:

(1) spraying 10 mu l/cm on the area to be welded of the two plastic parts²And keeping the contact of the joint surfaces to be welded;

(2) and (3) irradiating the welding area by using a laser with the wavelength of 1910nm, adjusting the output power of the laser to be 0.5W, melting the welding area after 5s, forming a melting surface with the size of a light spot after 10s, then closing the laser, naturally cooling and solidifying to form a welding area, and finishing welding.

Example 3

A method for laser welding plastic parts comprises mixing polycaprolactone (T) with molecular weight of 80000g/mol and thickness of 0.2mm_mApproximately 60 ℃) plastic part welding, for example, the method comprises the following steps:

(1) 6 mul/cm are wiped on the area where the two plastic parts are to be welded²And keeping the contact of the joint surfaces to be welded;

(2) and (3) irradiating the welding area by using a laser with the wavelength of 1470nm, adjusting the output power of the laser to be 0.5W, melting the welding area after 5s, forming a melting surface with the size of a light spot after 10s, then closing the laser, naturally cooling and solidifying to form a welding area, and finishing welding.

Example 4

A method of laser welding plastic parts, for example PCL/PU blended plastic product plastic parts having a thickness of 0.2mm, comprising the steps of:

(1) spraying 10 mu l/cm on the area to be welded of the two plastic parts²And the close contact of the junction surfaces to be welded is kept.

(2) And (3) irradiating the welding area by using a laser with the wavelength of 1470nm, adjusting the output power of the laser to be 0.5W, melting the welding area after 10s, forming a melting surface with the size of a light spot after 20s, then closing the laser, naturally cooling and solidifying to form a welding area, and finishing welding.

Example 5

A method for laser welding plastic parts, such as Polycaprolactone (PCL) plastic parts having a molecular weight of 50000g/mol and a thickness of 0.2mm, comprising the steps of:

(1) placing the two plastic parts in water, and keeping the welding joints in close contact by the lap joint;

(2) and (3) irradiating the welding area by using a laser with the wavelength of 1910nm, adjusting the output power of the laser to be 0.4W, melting the welding area after 20s, forming a melting surface with the size of a light spot after 30s, then closing the laser, naturally cooling and solidifying to form a welding area, and finishing welding.

Example 6

A method of laser welding plastic articles, such as Ethylene Vinyl Acetate (EVA) plastic articles having a thickness of 0.2mm, comprising the steps of:

(1) after roughening the areas to be welded of the two plastic parts, 6. mu.l/cm were wiped²And the welding joint is kept in close contact;

(2) and (3) irradiating the welding area by using a laser with the wavelength of 1470nm, adjusting the output power of the laser to be 0.6W, melting the welding area after 10s, forming a melting surface with the size of a light spot after 25s, then closing the laser, naturally cooling and solidifying to form a welding area, and finishing welding.

The above embodiments are only for embodying the inventive concept of the inventor, and any type of evolution and improvement based on the inventive concept of the invention are within the protection scope of the invention.

Claims

1. A method of laser welding plastics, characterized in that the method comprises the steps of:

(1) applying water to the area to be welded of the plastic to be welded to keep the surfaces to be welded of the plastic to be welded in close contact; the plastic is one or more of PVC, PVAc, PCL, PU, PHA polyester, PPC and PCL/PU composite materials; the amount of water applied is not less than 2. mu.l/cm²(ii) a The application mode is spraying, brushing, wiping or rolling; the plastic is pretreated by a method of pretreating a plastic watchSanding the surface to make the surface rough;

(2) irradiating the area to be welded by adopting a laser, namely completing the welding of the plastic; the laser wavelength emitted by the laser is 1.2-2.9 mu m; the melting point of the plastic is less than or equal to 100 ℃;

water is used as a photo-thermal conversion carrier, and the water temperature is rapidly raised by light energy absorbed by the water, so that the plastic with the melting point less than or equal to 100 ℃ is softened, and welding is realized.

2. A method according to claim 1, characterized in that in step (1) the plastic to be welded is a thermoplastic, a thermoplastic elastomer or a mixture of both.

3. The method of claim 1, wherein the plastic is in the form of a film, sheet, plate, tube, profile, or precision complex plastic part.