EP4719746A1

EP4719746A1 - Polyolefin weldment method and apparatus

Info

Publication number: EP4719746A1
Application number: EP24727432.7A
Authority: EP
Inventors: Hans LEENDERS; Jana HRACHOVA
Original assignee: SABIC Global Technologies BV
Current assignee: SABIC Global Technologies BV
Priority date: 2023-05-26
Filing date: 2024-05-24
Publication date: 2026-04-08
Also published as: WO2024245925A1; CN121175177A

Abstract

A process for preparing of a welded structure. The process includes positioning a first part comprising a polyolefin, and positioning a second part onto the first part to define a weld joint between them. The second part can comprise a polyolefin. The process can include welding the first part to the second part by projecting laser energy of about 980 nm through the first part to a weld joint, wherein the first part has a laser transmittance of less than 18%, measured using a spectrophotometer at wavelength 980 nanometers.

Description

POLYOLEFIN WELDMENT METHOD AND APPARATUS

BACKGROUND

[0001] Polymeric materials can be welded, however it can be a challenge to apply weld energy to a target location when there is a not direct path from the welding apparatus to the weld joint to be welded. Therefore, there is a need for an improved method and apparatus for creating polymer weldments, specifically for welding polyolefin.

[0002] US Published Patent Application 2006/0283544 discloses a laser welding method and apparatus especially suitable for laser welding polymer articles having low light transmissivity at the wavelength used for laser welding, but fails to address the welding of certain polymers.

[0003] US Published Patent Application 2005/203225 discloses a laser-transmissible composition comprising a dynamic crosslinking polyolefin thermoplastic elastomer that has a melting point ranging from 160 to 210 degrees Centigrade in case of non-coloring, and dye salt exhibiting transmission of a laser having a wavelength of 800 to 1200 nm. US Published Patent Application 2005/203225 further discloses a method for laser welding comprising putting a laser-transmissible molded workpiece 1 made from the laser-transmissible composition onto a laser-absorptive molded workpiece having a laser-absorbent, irradiating laser towards the laser-transmissible molded to weld the laser-transmissible molded workpiece and the laser-absorptive molded workpiece.

[0004] JP 2005 139445 discloses a laser beam-permeable colored thermoplastic resin composition containing an anthraquinone acid dye.

[0005] US Published Patent Application 2009/130451 discloses a laser-weldable composition comprising, based on the total weight of the laser-weldable composition, more than zero to 99.95 weight percent of a thermoplastic polymer composition; from 0.00001 to 5 weight percent of a near-infrared absorbing material; from 0.0 to 0.02 weight percent of carbon black; and from 0.05 to 20 weight percent of a white pigment.

DETAILED DESCRIPTION

[0006] To date, it has been understood that use of a first part exhibiting equal to or greater than 18% (laser transmittance) measured using a spectrophotometer at wavelength 980 nanometers (nm) offers a wide operating window for laser welded parts, transparent parts that do not exhibit burning, and welds that meet desired physical properties for strength and/or hermetic seal. It has been further understood that additives like glass fibers and talc fillers used as stiffeners and impact modifiers in plastics can cause the laser light to scatter and diffract, affecting weld times, bond strength, and overall weldability of parts. It has also been understood that as glass fiber content in glass filled materials decreases, laser radiation transmitted therethrough increases, and reducing the glass fiber content from 30 weight percent (wt. %) to 10 wt. % would significantly increase the operating window for welding.

[0007] Prior attempts to weld the polymers disclosed herein by directing the weld energy through a first part to a weld joint between the first part and the second part have failed. However, the present disclosure represents combinations of materials and laser processes that have been discovered that have produced adequate welds. Further, it has been determined that laser energy may even be directed through filled polymers, having for example glass and/or fire retardant filler.

[0008] Provided is a process for preparing of a welded structure including positioning a first part including a polyolefin; positioning a second part onto the first part to define a weld joint, wherein the second part includes a polyolefin; and welding the first part to the second part by projecting laser energy of about 980 nm through the first part to the weld joint. The first part has a laser transmittance of less than 18%, measured using a spectrophotometer at wavelength 980 nm. The second part can be laser absorbing.

[0009] Also provided is an apparatus, including a first part formed of polyolefin; a second part formed of polyolefin adjacent the first part defining a seam between them; and a weldment comprised of material from at least one of the first and second part, wherein at least a portion of the weldment is enveloped between the first part and the second part, spaced apart from the seam. The first part has a laser transmittance of less than 18%, measured using a spectrophotometer at wavelength 980 nm. The second part can be laser absorbing. The weldment can be formed by a process including applying a laser of 980 nm to the second part through the first part.

[0010] FIG. 1 discloses an exemplary embodiment. A laser beam 102 can be directed through a laser transmissive first layer or part 104. The first part can be translucent or transparent or colored. In an embodiment, the first part is not colored black using carbon black. The first part can be a polyolefin, and can optionally be glass-filled and/or fire-retardant filled polyolefin. The first part can be a natural color. The laser beam 102 can be directed toward a weld joint 106 between the first part 104 and a laser absorbing second layer or part 108. The second part 108 can be a polyolefin, and can optionally be glass- filled and/or fire-retardant filled polyolefin. The second part can be colored black using, e.g., carbon black. Clamping pressure 110 can be optionally provided.

[0011] The first part and the second part can be adjacent one another defining a seam 112 between them. A weldment 116 can be comprised of material from at least one of the first part 104 and second part 108. At least a portion of the weldment 116 can be enveloped between the first part 104 and the second part 108, spaced apart from the seam 112, which is present at intersecting surfaces of the first part 104 and the second part 108. The weldment 116, spaced apart from intersecting surfaces of the first part 104 and the second part 108 and internal to the welded structure, is formed through the first part 104 rather than at a side of the welded structure or through the seam 112. As shown in FIG. 1, the weldment 116 can be spaced apart from a side surface of the second part 108 by a distance D.

[0012] Laser welding is based on characteristics of plastics on laser-transmission, -reflection, and -absorption. The laser beam energy is absorbed at an interface of two or more parts to connect the two or more parts together. In a typical laser welding process, the laser penetrates through the laser transmissive part to reach the absorbing surface where the laser beam energy is converted into heat where the polymers start to melt. The melted polymers mix and connect to each other to create a weldment. This can happen under pressure where the parts are not able to move.

[0013] The inventors were surprised that the approaches disclosed here resulted in welds having a desirable strength. In some examples, a tension test to test the weld resulted in the material of one part failing before the weldment failed.

[0014] FIGS. 2A-2C disclose an exemplary embodiment. A laser beam 202 can be directed through a first part 204 which can be translucent or transparent or colored. The laser beam 202 can be directed toward a weld joint 206 between the first part 204 and a second part 208. Clamping pressure 210 can be optionally provided. Welding the weld joint 206 can result in the weldment 216. [0015] One or both the first part 204 and the second part 208 can be formed of a polyolefin. Polyolefin parts, i.e., a first polyolefin part and/or a second polyolefin part, can comprise a polyolefin chosen from the group of propylene-based polymers (polypropylenes), elastomers of ethylene and a-olefin comonomer having 4 to 8 carbon atoms, and any mixtures thereof. Preferably, the polyolefin comprises a propylene- based polymer. Preferably, the thermoplastic polymer composition comprises at least 80 wt. % of the propylene-based polymer, for example, at least 90 wt. %, at least 93 wt. %, at least 95 wt. %, at least 97 wt. % at least 98 wt. % or at least 99 wt. % of the propylene-based polymer based on the thermoplastic polymer composition. In a special embodiment, the thermoplastic polymer composition consists of the propylene-based polymer.

[0016] The propylene-based polymer can be at least one selected from the group consisting of a propylene homopolymer, a propylene random copolymer and a heterophasic propylene copolymer and mixtures thereof, preferably wherein the polyolefin comprises a propylene random copolymer; a propylene homopolymer and a heterophasic propylene copolymer; or a propylene homopolymer and a propylene random copolymer.

[0017] A propylene homopolymer can be obtained by polymerizing propylene under suitable polymerization conditions. A propylene copolymer can be obtained by copolymerizing propylene and one or more other a-olefins, preferably ethylene, under suitable polymerization conditions. The preparation of propylene homopolymers and copolymers is, for example, described in Moore, E. P. (1996) Polypropylene Handbook. Polymerization, Characterization, Properties, Processing, Applications, Hanser Publishers: New York.

[0018] The random propylene copolymer may comprise as the comonomer ethylene and/or an a-olefin chosen from the group of a-olefins having 4 to 10 C-atoms, preferably ethylene, 1 -butene, 1 -hexene or any mixtures thereof. The amount of the comonomer is preferably at most 10 wt. % based on the random propylene copolymer, for example, in the range from 2 to 7 wt. % based on the random propylene copolymer.

[0019] Polypropylenes can be made by any known polymerization technique as well as with any known polymerization catalyst system. Regarding the techniques, reference can be given to slurry, solution or gas phase polymerizations; regarding the catalyst system reference can be given to Ziegler-Natta, metallocene or single-site catalyst systems. All are, in themselves, known in the art.

[0020] Heterophasic propylene copolymers are generally prepared in one or more reactors, by polymerization of propylene in the presence of a catalyst and subsequent polymerization of an ethylene-a-olefin mixture. The resulting polymeric materials are heterophasic, but the specific morphology usually depends on the preparation method and monomer ratios used.

[0021] The heterophasic propylene copolymers can be produced using any conventional technique known to the skilled person, for example, multistage process polymerization, such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization or any combinations thereof. Any conventional catalyst systems, for example, Ziegler-Natta or metallocene may be used. Such techniques and catalysts are described, for example, in W006/010414; Polypropylene and other Polyolefins, by Ser van der en, Studies in Polymer Science 7, Elsevier 1990; W006/010414, US4399054 and US4472524.

[0022] The polymers or thermoplastic materials may be linear polymers or branched polymers or combinations thereof. The plastic can optionally be reinforced, e.g., with fibers, particles, flakes, as well as combinations comprising at least one of the foregoing, such as especially for example, long glass fibers, short glass fibers, glass beads, talc, mica, inorganic fillers, natural fibers, conductive fillers and/or carbon fibers. For example, the thermoplastic second and/or first part can be formed from STAMAX™ materials, a long glass fiber reinforced polypropylene commercially available from SABIC.

[0023] The polymer can comprise an additive, such as stabilizers, antioxidants, pigments; wherein the polymer preferably comprises at most 5 wt. % of the additive. The combination can be a blend or a copolymer. The polymer can be filled with a mineral filler, e.g., talc, or glass fibers; for example, the polymer can comprise at most 45 wt. % of the filler, such as for example, at most 40 wt. % of the filler, based on the total weight of the polymer. In an embodiment, the polymer can comprise a flame retardant additive such as a nitrogen-phosphorus based flame retardant.

[0024] In an embodiment, the polymer can comprise 10 to 40 wt. % or 15 to 40 wt. % or 20 to 40 wt. % or 25 to 30 wt. % of long glass fibers; 10 to 40 wt. % or 15 to 40 wt. % or 20 to 40 wt. % or 25 to 30 wt. % of short glass fibers; or 30 to 50 wt. % or 35 to 45 wt. % of long glass fibers, based on a total weight of the polymer.

[0025] The glass fibers used as filler in the polymer can be long and/or short glass fibers. Short glass fibers in the polymer may have an average length of up to 1.0 millimeter (mm). Long glass fibers in the polymer may have an average length of 1.0 to 4.5 mm, for example, 2.0 to 4.0 mm. The diameter of the glass fibers can be 5.0 to 50.0 micrometers, specifically, 8.0 to 30.0 micrometers, more specifically, 10.0 to 20.0 micrometers. The lengths and the diameters of the glass fibers can be determined based on the photo images by an image analysis software. The term “average” refers to an arithmetic average.

[0026] For example, the polyolefin is polypropylene or a combination of polypropylene and polyethylene, wherein preferably the polyolefin comprises at least 45 wt. % of polypropylene based on the total weight of the polyolefin.

[0027] For example, the polyolefin parts, i.e., first polyolefin part and/or second part, comprise a polyolefin filled with at most 40 wt. % of a filler based on the total weight of the polyolefin, wherein the polyolefin comprises a polypropylene or a combination of polypropylene and polyethylene, wherein preferably the polyolefin comprises at least 45 wt. % of polypropylene based on the total weight of the polyolefin.

[0028] With “a combination of polypropylene and polyethylene” is meant a heterophasic propylene copolymer or polypropylene impact copolymer, which is a polypropylene blended with an elastomer impact modifier, such as polyethylene particles, C2-C8 (ethylene-octene copolymer) elastomer impact modifier or C2-C4 (ethylene-butene copolymer) impact modifier.

[0029] For example, the welded structure can comprise a first polyolefin part and a second part, each independently comprising a polymer selected from the group consisting of: polypropylene, a combination of polypropylene and polyethylene, and combinations thereof. The polymer can be filled with a mineral filler, e.g., talc, or glass fibers, wherein the polymer comprises at most 45 wt. % of the filler, such as for example, at most 40 wt. % of the filler, based on the total weight of the polymer.

[0030] The first polyolefin part and the second part may comprise, for example, consist of the same polymer. [0031] The first part can have a thickness of, for example, 1 to 2 mm, for example, 1 to 1.6 mm, greater than 1 to 1.6 mm, 1 to less than 1.6 mm, greater than 1 to less than 1.6 mm, 1.6 to 2 mm, greater than 1.6 to 2 mm, 1.6 to less than 2 mm, or greater than 1.6 to less than 2 mm. The first part can have a laser transmittance of less than 18%, for example, less than or equal to 15%, less than or equal to 11.6%, less than or equal to 10.5%, less than or equal to 9.3%, less than or equal to 9.0%, less than or equal to 8.3%, less than or equal to 8.0%, less than or equal to 7.4%, less than or equal to 7.3%, less than or equal to 7.0%, less than or equal to 5.8%, less than or equal to 5.3%, less than or equal to 4.4%, or less than or equal to 3.4%, measured using a spectrophotometer at wavelength 980 nm. A laser transmittance of 0% means no light is transmitted through the part and a light transmittance of 100% means full light transmittance through the part.

[0032] The first part can include, for example, 10 to 40% by weight, preferably 15 to 30% by weight of glass fibers, based on a total weight of the first part. The process can include filling the first part with 10 to 40% by weight, preferably 15 to 30% by weight of glass fibers, based on a total weight of the first part.

[0033] The first part can include, for example, 10 to 30% by weight, preferably 20% by weight of flame retardant based on a total weight of the first part. The process can include filling the first part with 10 to 30% by weight, preferably 20% by weight of flame retardant based on a total weight of the first part.

[0034] The second part can include, for example, 10 to 40% by weight, preferably 15 to 30% by weight of glass fibers, based on a total weight of the second part. The process can include filling the second part with 10 to 40% by weight, preferably 15 to 30% by weight of glass fibers, based on a total weight of the second part.

[0035] The second part can include, for example, 10 to 30% by weight, preferably 20% by weight of flame retardant, based on a total weight of the second part. The process can include filling the second part withlO to 30% by weight, preferably 20% by weight of flame retardant, based on a total weight of the second part.

[0036] Weldment strength of the first part and the second part in lap shear test performed on bars can be greater than 5 megapascals (MPa). Weldment strength of the first part and the second part in burst pressure tests performed on welded pipes and plates can be greater than 0.5 MPa. [0037] A gap can be included in the weld joint 206 with T-joint design. The gap can be created between the first and second part. A design feature 214, e.g. a rim or a spacer, can be on the laser absorbing part. A rim or a spacer collapses during the laser welding. The rims or spacers can have a Z-axis height of from 0.3 to 1 mm. However, the weld joint 206 can be defined by the first part 204 abutting the second part 208 along the weld target.

[0038] Clamping can be used to clamp the first part 204 to the second part 208. Clamping force can be from about 2000 N to about 3000 newtons (N), preferably about 2600 N, even more preferably about 2592 N. Clamping pressure can be 3 to 5 newtons per square meter (N/mm²), preferably 4 N/mm². Clamping can result in a clamping pressure between the first part 204 and the second part 208 of from 5 to 7 bar (0.5 to 0.7 MPa), preferably about 6 bar (0.6 MPa), even more preferably 6.0 bar (0.6 MPa).

[0039] The laser emitter 212 can comprise a laser light source, a laser irradiator for irradiating the work to be welded, and an optical fiber for connecting the laser light source with the laser irradiator. These structural elements may be integrated. Examples of the laser light sources that can be used in the present invention include diode lasers (including those having a wavelength in a near-infrared region of 808 nm, 940 nm, or 980 nm), or the like.

[0040] An IPG diode laser at 980 nm and a maximum of 400 watts (W) power can be used with a TS-30 Scanner. Fiber diameter can be 200 micrometers, with collimation of 40. An optical lens Linos 420 can be used. Spot size can be 2 to 3 mm, preferably 2.44 mm. A working distance can be 400 to 700 mm, preferably 400 to 500 mm, more preferably 494.6 mm. Defocus of 0.00 mm can be used. A scale value - z of 300 to 400 can be used, preferably 336. A check distance 1 can be 400 to 700 mm, preferably 400 to 500 mm, more preferably 494.6 mm. A check distance 2 can be 20 to 40 mm, preferably 30 mm. Laser power and movement speed can be varied, t-hold can be 3 seconds. Air purge can be used. One laser pass can be used.

[0041] FIG 3A - FIG. 3B disclose an approach to forming a weld joint. A first part 302 can be disposed on a second part 308. A weldment 316 can be formed between the first part 302 and the second part 308. In such a configuration, the first part 302 can be clamped to the second part 308. The pipe is useful for determining the strength of the weldment 316 via pressurization of the pipe. In an example, a distal end of the pipe is coupled to a pressurizer, and a proximal end with the weldment 316 is pressurized until failure of the vessel.

EXAMPLES

[0042] Various combinations of materials were used. STAMAX™30YH570, STAMAX™40YM240E, and PPcompound H1030 were used in various combinations, with each material paired with a different material comprising the first part and the second part. SABIC PPcompound Hl 030 is a high flow, halogen free flame retardant, homopolymer with 30% glass fiber, developed for electrical and electronics applications, as well as automotive injection molded applications. It has a UL94V0@1.5mm and 5VA@3.0mm flame rating. This material has been designed to combine a good performance profile with good processing and flame resistant (FR) characteristics. A summary of the different polypropylene (PP) materials tested is provided in Table 1.

Table 1

[0043] The laser transmittance of the materials was measured before laser plastic welding using a spectrophotometer at wavelength 980 nanometers (nm). The laser transmittance (%) of the materials used are provided in Table 2. Table 2

[0044] Laser weld strengths of a first part (H1030 natural, laser transmissive material) and a second part (black, absorbing material, 2 mm thickness) were measured. A thickness of the first part 204 was 1.0 mm, 1.6 mm, or 2.0 mm. Table 3 and FIG. 4 provide results.

Lap shear tests according to DIN EN 1465:2009 (Determination of tensile lap-shear strength of welded assemblies) were performed on each sample.

Table 3: Weld strength

SF = substrate failure (fracture of a part adjacent to a weld without breakdown of the weld) CF = cohesion failure (fracture of a part within a weld; internal breakdown of the weld) AF = adhesion failure (failure at interface of parts; parts not adhering to each other) [0045] FIG. 4 shows that first parts having a thickness of 2.0 mm have surprisingly desirable performance, even though they are thicker than first parts having a thickness of 1.0 mm or 1.6 mm. Further, it is surprising that materials filled with glass fibers and/or flame retardant even were able to be welded through.

[0046] The results demonstrate that a polyolefin filled with glass fiber, for example, 20 to 40 wt. % of glass fibers based on a total weight of the polyolefin, and optionally flame retardant additive, for example, 10 to 30 wt. % of flame retardant additive based on a total weight of the polyolefin, despite laser transmittance of less than 15%, measured using a spectrophotometer at wavelength 980 nm can bond with good quality weldment without burning or poor adhesion, resulting in weldment strength greater than 5 MPa in lap shear test performed on bars.

[0047] FIG. 5 A shows a weldment of a 2.0 mm thick STAMAX™30YH570 laser transmissive first part and an Hl 030 black pipe second part. FIG. 5B shows the failure under pressure on the welded structure after accelerated aging.

[0048] FIG. 6A shows a weldment of a 2.0 mm thick STAMAX™30YH570 laser transmissive first part and an Hl 030 black pipe second part. FIG. 6B shows the failure under pressure on the welded structure after initial conditioning.

[0049] FIG. 7A shows a weldment of a 2.0 mm thick STAMAX™30YH570 laser transmissive first part and an Hl 030 black pipe second part. FIG. 7B shows the failure under pressure on the welded structure after initial conditioning.

[0050] FIG 8 A - FIG. 8C show different failure types of welded parts. The failure types include “Lid off,” as shown in FIG. 8A, “Punch out,” as shown in FIG. 8B, and “Weld break,” as shown in FIG. 8C.

[0051] Laser transmissive polypropylene first parts laser welded to polypropylene black pipe second parts were tested for burst pressure after different forms of conditioning. “Initial” conditioning involved conditioning for 168 hours at 23±2°C and 50±6% relative humidity. Samples subjected to “extended” conditioning (also referred to herein as “accelerated aging”) were first subjected to Initial conditioning followed by being subjected to heating and cooling cycles at various relative humidities. Results of the burst pressure tests are shown in FIG. 9, FIG. 10, FIG. 11 A, FIG. 11B, and FIG. [0052] The results demonstrate that a polyolefin filled with glass fiber, for example, 10 to 40 wt. %, or 15 to 40 wt. %, of glass fibers based on a total weight of the polyolefin, and optionally flame retardant additive, for example, 10 to 30 wt. % of flame retardant additive based on a total weight of the polyolefin, despite laser transmittance of less than 15%, measured using a spectrophotometer at wavelength 980 nm can bond with good quality weldment without burning or poor adhesion, resulting in weldment strength greater than 5 bars (0.5 MPa) in burst pressure tests performed on welded pipes and plates.

[0053] A welded structure can be obtained by the process according to the invention. Such welded structure can, for example, be used as an automotive part, such as a tailgate or a roof spoiler or a bumper. The first and/or second part can be a battery part for a vehicle such as an electric vehicle.

[0054] It is further noted that the term ’’comprising” does not exclude the presence of other elements. However, it is also to be understood that a description on a product/composition comprising certain components also discloses a product/composition consisting of these components. The product/composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product/composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps may be advantageous in that it offers a simpler, more economical process. When values are mentioned for a lower limit and an upper limit, ranges made by the combinations of the values of the lower limit and the values of the upper limit are also understood to be disclosed.

[0055] The term “automotive” or “automobile(s)” or “vehicle(s)” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example, both gasoline-powered and electric-powered vehicles.

Claims

1. A process for preparing of a welded structure comprising: positioning a first part comprising a polyolefin; positioning a second part onto the first part to define a weld joint, wherein the second part comprises a polyolefin; and welding the first part to the second part by projecting laser energy of about 980 nm through the first part to the weld joint, wherein the first part has a laser transmittance of less than 18%, measured using a spectrophotometer at wavelength 980 nanometers.

2. The process of any of the preceding claims, wherein the second part is laser absorbing.

3. The process of any of the preceding claims, comprising filling the second part with 10 to 40% by weight, preferably 15 to 30% by weight of glass fibers, based on a total weight of the second part.

4. The process of any of the preceding claims, comprising filling the second part with 10 to 30% by weight, preferably 20% by weight of flame retardant, based on a total weight of the second part.

5. The process of any of the preceding claims, comprising filling the first part with 10 to 40% by weight, preferably 15 to 30% by weight of glass fibers, based on a total weight of the first part.

6. The process of any of the preceding claims, comprising filling the first part with 10 to 30% by weight, preferably 20% by weight of flame retardant based on a total weight of the first part.

7. An apparatus, comprising: a first part formed of polyolefin; a second part formed of polyolefin adjacent the first part defining a seam between them; and a weldment comprised of material from at least one of the first and second part, wherein at least a portion of the weldment is enveloped between the first part and the second part, spaced apart from the seam, wherein the first part has a laser transmittance of less than 18%, measured using a spectrophotometer at wavelength 980 nanometers.

8. The apparatus of claims 8-9, wherein the second part is laser absorbing.

9. The apparatus of claims 8-10, wherein the second part is filled with 10 to 40% by weight, preferably 15 to 30% by weight of glass fibers, based on a total weight of the second part.

10. The apparatus of claims 8-11, wherein the second part is filled with flame retardant 10 to 30% by weight, preferably 20% by weight of flame retardant , based on a total weight of the second part.

11. The apparatus of claims 8-12, wherein the first part is filled with 10 to 40% by weight, preferably 15 to 30% by weight of glass fibers, based on a total weight of the first part.

12. The apparatus of claims 8-13, wherein the first part is filled with flame retardant 10 to 30% by weight, preferably 20% by weight of flame retardant , based on a total weight of the first part.

13. The apparatus of claim 8-14, wherein the weldment is formed by a process comprising applying a laser of 980 nm to the second part through the first part.