Laser welding method for plastic and silica gel and welded product

Abstract

The invention discloses a laser welding method for plastic and silica gel, and relates to the field of laser plastic welding processes. The method solves the technical problem that the traditional silica gel and plastic cannot realize the welding process. The method comprises the following steps: adopting a TPSIV material, and adding an infrared absorbent into the TPSIV material to modify the TPSIV material so as to adjust the absorption performance; providing a laser-penetrable plastic part as an upper part, and taking the modified TPSIV silica gel part as a light absorption part; after the upper part is matched with the light absorption part, a laser beam is guided to penetrate through the upper part and irradiate the light absorption part, the light absorption part absorbs energy to be melted, and welding combination is achieved through heat conduction. The invention realizes firm connection between the plastic and the silica gel, and is applicable to precise structures such as electronic cigarette cartridges and the like.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, and more particularly to the joining technology of dissimilar materials. More specifically, this invention relates to a laser welding method for plastics and silicone, and welded products. Background Technology

[0002] In modern manufacturing, especially in fields such as medical devices, consumer electronics (such as e-cigarette cartridges) and automotive parts, it is often necessary to combine rigid plastic parts with flexible sealing silicone parts.

[0003] Currently, traditional processes for achieving this bonding mainly rely on mechanical snap-fitting, adhesive bonding, or secondary injection molding. Mechanical snap-fitting has a complex structure, occupies a large space, and is difficult to achieve a reliable airtight seal. Adhesive bonding has a cumbersome process, long curing time, and the adhesive is prone to aging and failure, and may introduce chemical contaminants, making it unsuitable for applications requiring high purity. Although secondary injection molding provides a good bonding effect, the mold cost is extremely high, process control is complex, and material selection compatibility is poor.

[0004] Laser welding, as a high-precision, high-efficiency, and high-cleanliness joining technology, has been widely used in welding plastics to plastics. However, traditional silicone (usually a thermosetting material) and plastics are generally considered incompatible for fusion welding due to their fundamental differences in chemical and physical properties (such as melting point and material polarity). Therefore, the industry urgently needs a new technology that can quickly, firmly, and cleanly join plastics to silicone (or silicone-like elastomers). Summary of the Invention

[0005] The primary technical objective of this invention is to overcome the technical prejudice in the prior art that plastics and silicone cannot be joined by fusion welding, and to provide an innovative laser welding method for plastics and silicone.

[0006] Another technical objective of this invention is to provide a welded article manufactured by the above method, which has high bonding strength and excellent airtightness at the interface between plastic and silicone.

[0007] To achieve the above objectives, the present invention provides a laser welding method for plastic and silicone, characterized by comprising the following steps: providing a first component, the first component being a laser-penetrable plastic component; providing a second component, the second component comprising TPSIV material; modifying the second component, the modification comprising adding an infrared absorber to the TPSIV material; fitting the first component and the modified second component together; and guiding a laser beam through the first component and irradiating the modified second component, causing the modified second component to absorb laser energy and melt, thereby welding the first component and the second component together.

[0008] Furthermore, the present invention also provides a welded article, characterized in that it comprises: a plastic component; and a silicone component, the silicone component comprising TPSIV material and an infrared absorber, wherein the plastic component and the silicone component are seamlessly bonded together by a laser welding interface.

[0009] The beneficial effects of this invention are as follows: Breaking through material limitations: This invention is the first to achieve laser fusion welding between plastics and silicone (like) materials, which are traditionally considered unweldable, solving a long-standing technical problem in the industry.

[0010] High bonding strength and sealing performance: Through material modification and precise control of process parameters, a strong physical interlock and chemical bond are formed at the interface of two heterogeneous materials, which can achieve high-strength airtight sealing, making it particularly suitable for high-requirement products such as e-cigarette cartridges.

[0011] High efficiency and high precision: Utilizing the non-contact and high energy density characteristics of lasers, welding speed is fast, heat-affected zone is small, and automated, high-precision production can be achieved.

[0012] High cleanliness: The welding process requires no adhesives or solvents, leaving no chemical residues, making it particularly suitable for medical, food, and consumer electronics applications.

[0013] High process flexibility: By adjusting the type of infrared absorber and laser parameters, it can be adapted to different types of plastics and TPSiV materials, and has wide applicability. Attached Figure Description

[0014] Figure 1 This is a partial cross-sectional schematic diagram of the energy guiding structure used in one embodiment of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this application clearer, the integrated tunable spot laser of this application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0016] In the description of this application, unless otherwise stated, "a plurality of" means two or more; the terms "center," "longitudinal," "lateral," "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0017] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019]

Example 1

[0020] The method in this embodiment includes the following steps: Step S101: Provide the first component.

[0021] The first component is the e-cigarette cartridge's reservoir shell, 1919, made of medical-grade polycarbonate (PC). This material boasts excellent biocompatibility, high impact strength, and high transparency. Crucially, this PC material exhibits a laser transmittance greater than 60% in the near-infrared spectral region at 940nm wavelength (meeting the requirement of "infrared transmittance ≥ 50%)", thus fulfilling the condition of "laser penetration." The welding area of ​​this component is designed as a mating surface with a grooved structure.

[0022] Step S102: Provide a second component and modify it.

[0023] The second component is the bottom seal of the electronic cigarette cartridge, and its base material is TPSiV® (thermoplastic silicone vulcanizate) produced by Dow Corning, Inc., specifically the brand name XIAMETER™TPSiV4200-50A.

[0024] Modification steps: One of the core aspects of this invention lies in modifying the optical properties of the TPSiV material. This modification step is not a simple physical mixing process, but rather employs a specific industrial preparation method that ensures highly homogeneous homogenization. (a) Preparation of high-concentration masterbatch: First, a specific infrared absorber is selected. In this example, it is a phthalocyanine-based near-infrared absorbing dye (e.g., the Epolight™ series), whose absorption peak wavelength in DMSO solution is [not specified]. Precisely located at 940 nm. The dye powder is premixed with a low molecular weight polyethylene wax (PE-WAX) carrier and a dispersant (such as zinc stearate) in a high-speed mixer. The premix is ​​then fed into a twin-screw granulator for melt extrusion, followed by granulation to produce an infrared absorber masterbatch with a dye concentration of 5% (wt).

[0025] (b) Melt blending: The masterbatch prepared above (2.0% wt) was premixed with the dried TPSiV4200-50A base material (98.0% wt) in a hopper. The mixture was then fed into a Coperion ZSK26 co-rotating twin-screw extruder for thorough melt blending and dispersion. The extruder temperature was set to 180°C to 220°C, and the screw speed was 300 rpm. This high-shear melt blending ensured that the phthalocyanine dye molecules achieved a uniform nanoscale dispersion within the TPSiV matrix.

[0026] (c) Component preparation: The modified TPSiV mixture is injection molded using an injection molding machine to produce the bottom seal of the electronic cigarette cartridge (i.e., the second component). The modified second component has an infrared transmittance of less than 5% at a wavelength of 940nm (meeting the requirement of "infrared transmittance not exceeding 20%)", thus becoming a "light-absorbing component".

[0027] Step S103: Component assembly.

[0028] Assemble the PC oil storage tank (first component) in step S101 and the modified TPSiV seal (second component) in step S102.

[0029] Interface integration: An energy-directing structure is employed. Specifically, refer to... Figure 1 The energy-directing structure shown features a 0.90 mm deep groove in the PC component and a 1.21 mm high step-joint boss 28 in the modified TPSiV component. After assembly, the tip of the TPSiV boss (1.20 mm wide portion) engages with the groove in the PC component, forming a 0.15 mm interference fit. This design not only provides initial positioning and sealing, but more importantly, it concentrates laser energy at the tip of the boss, guiding the melting process.

[0030] Tooling clamping: A standard machine with an upper and lower structure is used. This machine is equipped with precision tooling featuring automatic leveling and a precision control module. Before welding, the tooling's pressure head (product pressing device) applies a preset clamping pressure of 0.4 MPa to the PC component. This pressure ensures a tight, gapless fit between the PC and TPSiV mating interfaces. Simultaneously, the automatic leveling function ensures uniform pressure distribution, and the precision control module (such as a Z-axis servo motor) ensures that the mating interface is always precisely positioned on the laser's focal plane.

[0031] Step S104: Guide the laser beam for welding.

[0032] After assembly and clamping, start the laser welding program.

[0033] Laser system: It employs a TRUMPF TruDiode151 semiconductor laser and is equipped with a galvanometer scanning system 36.

[0034] Wavelength matching: Laser operating wavelength It was precisely set to 940 nm. This wavelength corresponds to the 940 nm absorption peak of the phthalocyanine dye selected in step S102. Highly matched. The range is much smaller than the 20nm limit. This matching allows the modified TPSiV component to absorb laser energy with the highest efficiency, while the PC component is almost completely transparent.

[0035] Laser mode: To precisely control heat input and prevent excessive heat accumulation that could lead to TPSiV material degradation or PC component deformation, this embodiment employs a pulsed laser beam. The parameters are set as follows: peak power 120W, pulse width 5ms, and repetition frequency 100Hz (i.e., 10% duty cycle). This "cumulative heating" mode melts the interface while allowing for minute cooling during the pulse intervals, effectively controlling the heat-affected zone (HAZ).

[0036] Closed-loop feedback control: The welding system in this embodiment is also equipped with an advanced closed-loop feedback control system. A pyrometer (thermal radiation detector) is arranged coaxially with the laser beam to monitor the infrared thermal radiation characteristics of the welding interface (i.e., the PC-TPSiV contact point) in real time. This signal is sent back to the control system (e.g., the control system and software) and compared with a preset welding temperature (e.g., 230°C, which is higher than the melting point of TPSiV but lower than the degradation temperature of PC). The PID controller adjusts the laser pulse width (or peak power) in real time based on the error signal, thereby precisely maintaining the welding temperature within the target range (e.g., ±5°C). This overcomes the influence of individual workpiece differences (such as fit clearance and slight fluctuations in dye concentration) on the welding quality.

[0037] Welding process: The laser beam scans along the path of the stepped joint. The 940nm laser passes through the PC component and is instantaneously absorbed by the phthalocyanine dye in the modified TPSiV component, generating highly concentrated heat at the interface. The tips of the modified TPSiV bosses melt first, and the heat, through thermal conduction, melts the surface of the grooves in the PC component. Under a continuous pressure of 0.4MPa from the tooling, the melts of the two materials undergo interdiffusion of molecular chains and physical entanglement. After the laser scan, the interface rapidly cools and solidifies.

[0038] Step S105: Obtain the product.

[0039] After welding, the tooling is depressurized, and the workpiece is removed (either manually or by a robotic arm). A welded product (Claim 10) is obtained, which is an electronic cigarette cartridge component seamlessly joined by a PC oil reservoir and a modified TPSiV seal through laser welding. This joint forms a high-strength airtight seal (Claim 8). In semi-automatic equipment, this step can also be performed simultaneously with airtightness testing (simultaneous welding and inspection).

[0040]

Example 2

[0041] The difference from Example 1 is as follows: The first component is made of PMMA (polymethyl methacrylate), which has high transmittance at a wavelength of 808nm.

[0042] The second component: the base material is TPSiV4000-60A.

[0043] Modification (Claim 1): The infrared absorber uses a naphthalocyanine-based dye with an absorption peak value of [missing information]. Located at 808 nm. The modification step involved a simple dry blending followed by granulation using a single-screw extruder. Although the homogeneity was not as good as in Example 1 (Claim 3 is not supported), the basic objectives of the invention were still achieved.

[0044] Claim4: Employs a left-right lap joint rather than a stepped joint.

[0045] Laser system (Claim2): Employs an 808nm wavelength semiconductor laser. Wavelength matching ( It still meets the requirements of Claim2.

[0046] Laser mode (Claim1): Continuous wave (CW) mode (Claim6 not supported), power 50W, scanning speed 100mm / s.

[0047] Control (Claim1): Open-loop control is used, meaning power and speed are constant (Claim7 is not supported).

[0048] result: This embodiment also yielded a robust welded article (Claim 10). This demonstrates that the invention is not limited to specific materials, absorbents, laser modes, or control methods; it can be achieved as long as the core steps of claim 1 are satisfied.

[0049]

Example 3

[0050] The difference from Example 1 is as follows: Claim 1: Instead of using a dye with a specific wavelength, conductive carbon black is used as the infrared absorber. The concentration added is 0.1% (wt). Carbon black is a broad-spectrum absorber and can be used to prepare black parts 46.

[0051] Laser System (Claim1): Employs a 980nm semiconductor laser. Since carbon black exhibits broad-spectrum absorption, precise wavelength matching is not required (Claim2 is not supported).

[0052] Laser mode (Claim1): Continuous wave (CW) mode, power 55W.

[0053] result: Similarly, an airtight welded article (Claim10) suitable for electronic cigarette cartridges (Claim8) was also obtained. This demonstrates the broad applicability of the absorbent selection in this invention.

[0054] [Comparative Example 1] (Background Technology) Repeat all the steps of Example 1, except that the second component is made of conventional, unmodified thermosetting silicone rubber (platinum vulcanized).

[0055] result: In step S104, the 940nm laser beam passes through both the PC component and the silicone rubber component simultaneously. Since the thermosetting silicone rubber contains no absorbent and does not melt, no change occurs at the interface. After cooling, the two components separate instantly, with a weld strength of 0.

[0056] Conclusion: This proves the fact in the background art that "traditional silicone and plastic cannot achieve welding processes".47

[0057] [Comparative Example 2] (Proving the necessity of the modification step) Repeat all the steps of Example 1, except that the second component uses unmodified TPSiV4200-50A material, i.e., step 48 of "adding infrared absorber" is omitted.

[0058] result: In step S104, the 940nm laser beam passed through the PC component and also through the naturally translucent TPSiV component. No energy absorption occurred at the interface, and no melting took place. The weld strength was 0.

[0059] Conclusion: This demonstrates that "adding an infrared absorber" is an essential technical feature for the establishment of this invention.

[0060] Comparative Example 3 Repeat all the steps of Example 1, with the only difference being: In the modification step S102, the steps of (a) preparing the masterbatch and (b) melt blending in a twin-screw extruder are omitted. Instead, 0.1% (wt) of phthalocyanine dye powder is simply shaken and mixed with TPSiV granules in a plastic bag (dry blending), and then directly fed into the injection molding machine.

[0061] result: Due to the extremely uneven distribution of the dye powder, serious quality problems occurred during the welding process in step S104: (a) Dye aggregation zone: Excessive absorption of laser energy leads to severe degradation, carbonization and bubbling of TPSiV material.

[0062] (b) Dye-deficient areas: Laser energy penetrates without melting.

[0063] (c) The weld interface strength of the obtained product is extremely low and extremely unstable.

[0064] Conclusion: This study demonstrates that the homogenization method of "masterbatch + twin-screw blending" as defined in claim 3 is crucial for achieving stable and high-quality welding and has non-obvious beneficial effects.

[0065] [Experimental Data] (Proving Beneficial Effects) To quantify the beneficial effects of the present invention, tensile peel strength tests were conducted on the samples of the above embodiments and comparative examples (standard tensile specimens were made after welding) (refer to ASTM D1876 standard).

[0066] The test results are as follows: Example 1 (PC / Mod-TPSiV, pulsed, closed-loop, step-joint): The average peel strength was 15.2 N / cm. The weld exhibited high toughness, and the failure mode was TPSiV material bulk tearing, indicating that the weld strength was higher than the strength of the material itself.

[0067] Example 2 (PMMA / Mod-TPSiV, CW, Lap-Joint): Average peel strength was 12.5 N / cm.

[0068] Example 3 (PC / Carbon-TPSiV, CW): Average peel strength was 13.8 N / cm.

[0069] Comparative Example 1 (PC / Traditional Silicone): 0 N / cm 50.

[0070] Comparative Example 2 (PC / unmodified TPSiV): 0 N / cm.

[0071] Comparative Example 3 (PC / non-uniformly modified TPSiV): The strength data are highly discrete, ranging from 0 N / cm to 5 N / cm, with an average value of only 2.8 N / cm.

[0072] Meanwhile, the airtightness of the electronic cigarette cartridge components (Claim8) prepared in Examples 1, 3 and Comparative Example 3 was tested (bubbles were observed when the cartridges were placed in water at a pressure of 50 kPa).

[0073] Example 1: 0 out of 100 samples leaked (100% pass rate).

[0074] Example 3: 2 out of 100 samples leaked (98% pass rate).

[0075] Comparative Example 3: 77 out of 100 samples leaked (23% pass rate).

[0076] Data conclusions: The technical solutions of this invention (Examples 1-3) successfully achieved high-strength, high-airtightness welding between plastic and TPSiV, with performance far exceeding that of the comparative examples. Meanwhile, Example 1 (which employs preferred features of Claims 3, 5, 6, 7, and 9) exhibits the best performance and consistency, demonstrating the further inventive technical effects brought about by the dependent claims.

[0077] Summarize This invention provides a welded article comprising a plastic component (such as PC, PMMA) and a silicone component. The silicone component is unique in that it contains TPSiV material and an infrared absorber. These two originally incompatible components are seamlessly bonded at the interface using the laser welding method of this invention.

[0078] The scope of protection of this invention is not limited to the embodiments described above. For example, the first component (plastic component) is not limited to PC or PMMA, but can be any other thermoplastic material that is transparent at the selected laser wavelength, such as ABS, SAN, PBT, etc. The second component (TPSiV) is also not limited to a specific grade. The infrared absorber is also not limited to phthalocyanine or carbon black, but can be any additive capable of efficiently absorbing energy and converting it into heat at that wavelength. The laser is also not limited to 940nm or 808nm.

[0079] The tooling structure of the present invention is not limited to the standard machine with an upper and lower structure. It can also be a standard machine with a left and right structure or a semi-automatic machine with a multi-station rotating mechanism to achieve higher production efficiency.

[0080] In summary, the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although this application has disclosed the preferred embodiment as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method of laser welding of plastic and silicon, characterized by, The method comprises the following steps: providing a first component, which is a laser-permeable plastic component; providing a second component, which comprises a TPSIV material; modifying the second component, which comprises adding an infrared absorber to the TPSIV material; matching the first component with the modified second component; and directing a laser beam to pass through the first component and irradiate on the modified second component, so that the modified second component absorbs laser energy and melts, thereby welding the first component and the second component together.

2. The method of claim 1, wherein, The infrared absorber is a near-infrared absorbing dye with a specific absorption peak; and the wavelength of the laser beam matches the absorption peak wavelength of the dye, so that the absolute value of the difference between the wavelength of the laser beam and the absorption peak wavelength of the dye is less than or equal to 20 nm.

3. The method according to claim 1 or 2, characterized in that, The modification step further comprises: preparing a high-concentration master batch of the infrared absorber, and then melt blending the master batch with the TPSIV material through a twin-screw extruder to achieve uniform dispersion of the infrared absorber in the second component.

4. The method of claim 1, wherein, The interface between the first component and the second component is configured as an energy guiding structure.

5. The method of claim 4, wherein, The energy guiding structure is a stepped joint, in which a protruding part of the second component is fitted and embedded into a groove part of the first component.

6. The method of claim 1, wherein, The laser beam is a pulsed laser beam, and by adjusting its pulse width and repetition frequency, cumulative melting of heat is achieved in the modified second component while minimizing the thermal influence area on the first component.

7. The method of claim 1, wherein, The method further comprises: in the step of directing the laser beam, monitoring the thermal radiation characteristics of the welding interface in real time; and based on the thermal radiation characteristics, closed-loop feedback controls the power or scanning speed of the laser beam to maintain the welding temperature of the interface within the preset melting temperature range of the modified TPSIV material.

8. The method of claim 1, wherein, The first component is the shell or frame of a cartridge, and the second component is a silica gel seal that seals the cartridge; the welding combination is used to form an airtight seal between the shell and the silica gel seal.

9. The method of claim 1, wherein, The method uses a tooling with an automatic leveling function and a precision control module; the matching step comprises: using the tooling to apply a predetermined clamping pressure to the first component and the second component to ensure that the focal point of the laser beam is accurately located on the matching interface of the components.

10. A soldered article characterized by, comprises: a plastic component; and a silica gel component, which comprises a TPSIV material and an infrared absorber, wherein the plastic component and the silica gel component are seamlessly combined through a laser welding interface.

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