HIGH STRENGTH POLYMER METAL COMPOSITES AND METHODS OF MAKING THEREOF

Abstract

The present invention provides polymer-metal composites free of adhesives and methods of making same. In particular, the present invention takes advantage of a unique metallic bonding surface created by exposure to a laser whereby micron-sized fragments are fixed to the metallic bonding surface such that a high strength bond with polymeric material is created upon exposure to a second laser.

Claims

1. A polymeric-metallic composite material, the composite comprising a metallic substrate characterized by a bulk portion and a bonding surface, the surface including a plurality of fragments fixed thereto with interstices there between; the fragments characterized by having (i) a maximum measureable dimension less than 50 microns, and (ii) substantially the same composition as the bulk portion; and a polymeric substrate characterized by a portion thereof inhabiting at least a portion of the interstices, wherein the composite is further characterized by the absence of any adhesive and its cohesive rather than adhesive failure when subjected to standard strength tests.

2. The polymeric-metallic composite material of claim 1, wherein the fragments are arranged in a plurality of ranks.

3. The polymeric-metallic composite material of claim 1, wherein the bonding surface prior to its combination with the polymeric substrate is characterized by a contact angle less than 10.

4. The polymeric-metallic composite material of claim 1, wherein the metallic substrate is selected from the group of metals including steel, titanium and nitinol.

5. The polymeric-metallic composite material of claim 1, wherein the metallic substrate is selected from the group of metals including aluminum, aluminum oxide and other aluminum alloys.

6. The polymeric-metallic composite material of claim 4, wherein the bonding surface prior to its combination with the polymeric substrate is characterized by an Rz range from 4 and 8.5 microns.

7. The polymeric-metallic composite material of claim 4, wherein the bonding surface prior to its combination with the polymeric substrate is characterized by an Ra range from 0.5 and 1.6 microns.

8. The polymeric-metallic composite material of claim 5, wherein the bonding surface prior to its combination with the polymeric substrate is characterized by an Rz value around 38 microns.

9. The polymeric-metallic composite material of claim 5, wherein the bonding surface prior to its combination with the polymeric substrate is characterized by an Ra range from 6.7 to 7 microns.

10. The polymeric-metallic composite material of claim 1, wherein the bonding surface is characterized by 75% or more of the fragments having a maximum measurable dimension less than 10 microns.

11. The polymeric-metallic composite material of claim 1, wherein the bonding surface is characterized by 90% or more of the fragments haying a maximum measureable dimension less than 10 microns.

12. The polymeric-metallic composite material of claim 1, wherein the bond between the two substrates is characterized by a maximum load greater than 380 N.

13. A method of creating polymeric-metallic composites, the method comprising; exposing a surface of a metallic substrate with a laser energy sufficient to create a treated surface characterized by micron-sized particulate structures thereon, the particulate structures having the same composition as the substrate and fixed thereto; positioning a pre-determined polymeric material adjacent the treated surface; exposing the adjacent polymer metallic components with a laser energy sufficient to melt the polymeric material such that portions thereof flow between the micron-sized particulate structures on the treated surface such that a high strength mechanical bond is created there between.

14. The method of claim 13, wherein the metallic substrate is exposed to a pulse laser.

15. The method of claim 14, wherein the pulsed laser has pulse widths greater between 5 ns and 200 ns.

16. The method of claim 14, wherein the metallic substrate is exposed to pulse widths in a range from 150 ps to 5 ns.

17. The method of claim 13, wherein the metallic substrate is exposed by the laser in a boustrophedonic pattern.

18. The method of claim 13, wherein the laser used to melt the polymeric materials is a thulium fiber laser.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention provides improved polymeric-metallic composites and methods for producing same. Set forth below are the data supporting both the compositions and methods used to produce the novel compositions.

[0016] The texturing of the metallic substrates investigated provided some subtle differences. In particular, the present inventors discovered that no universal laser energy, nor universal laser, provided the bonding surface sufficient to create the high strength mechanical bonds that were the object of the present invention. Particularly, the present inventors found a distinction between two groups of metallic substrates: the first being a group of stainless steel, titanium and nitinol and the second group being aluminum and anodized aluminum. As the data set forth below provides, the second group required much higher Ra and Rz measurements to provide the strengths needed. In order to provide such higher roughness characteristics, the present inventors experimented with other lasers and found a second laser that was able to produce a more desirable bonding surface.

[0017] The optimum texture for the first group of metallic substrates was produced by a YLPP-1-150V-30 laser produced by IPG Photonics of Oxford, Mass. This 1064 pulsed laser provided pulses with a 5 ns width at a pulse repetition rate of 100 kHz. The speed was set for 1000 mm/s with a fill of 0.1 mm and was operated in a Boustrophedonic pattern.

[0018] While the laser used for the first group could provide serviceable bonding to create metallic-polymeric composites, the optimum texture for the second group of metallic substrates was produced by a second laser, a YLP-V2-1-100-50-50-LM laser produced by IPG Photonics of Oxford, Mass. This 1064 pulsed laser provided pulses with a 100 ns width at a pulse repetition rate of 150 kHz. The speed was 1000 mm/s with a fill of 0.0055 mm and was operated in a Boustrophedonic pattern.

[0019] FIG. 1 provides a scanning electron micrograph of 304 stainless steel sample surface after texturing but before bonding. Note the fragments on the surface being arranged in ranks due to the Boustrophedonic pattern in which the laser was operate. Further note the small, fairly uniform particle size of the fragments, all of which are substantially smaller than 25 microns in diameter.

[0020] FIG. 2 provides a scanning electron micrograph of titanium sample surface after texturing but before bonding. This SEM is at a higher magnification than FIG. 1 and sets forth fragments, substantially all of which have a maximum measurable diameter of less than 10 microns. Per FIG. 1, the fragments are arranged in ranks.

[0021] FIGS. 3-5 are SEMS of aluminum sample surfaces after texturing but before bonding. While the general appearance of the particles in terms of size and orientation are similar to those of FIGS. 1 and 2, upon close inspection of FIG. 3, the fragments themselves are not solid but have further crevices therein, such that they provide even more surface area than that provided by the metal substrates of the first group. Note further that the ranks are not as prominently separated, as they are not truly distinguishable until the magnification is set at 100 microns FIGS. 4-5).

[0022] The parameters used for the bonding of polymeric materials to group one metallic substrates (stainless steel, titanium and nitinol) are set forth herein below. A TLM-120-WC laser, provided by IPG Photonics of Oxford, Mass., was used for this portion of the invention. The 1940.2 nm laser was operated at a speed of 100 mm/s at 61% power level, with the beam scanned over the sample, with a 0.75 mm distance between each lines, with multiple passes (2 or 3) were made, for the boding of high density polyethylene (HDPE) to the group one metallic substrates. With respect to the bonding of the group one substrates to thick poly carbonate (PC), the processing parameters were altered somewhat. Specifically, the line width between passes was narrowed to 0.5 mm, the power was reduced to 33% and the number of passes was increased (5-9 passes).

[0023] With respect to thin PC to the metallic substrates of group one, the laser was operated at 23% with a distance of 0.5 mm between each pass. For this material, a complete single pass was made, with repetitions for as many as 4 times to complete bonding.

[0024] The parameters used for the bonding of HDPE to group two metallic substrates (aluminum and anodized aluminum) are set forth herein below. A TLM-120-WC laser, provided by IPG Photonics of Oxford, Mass., was used for this portion of the invention. The 1940.2 nm laser was operated at a speed of 100 mm/s. The distance between lines was 0.75 mm and the power was varied between 50 and 66%. 1-6 passes were made on each line.

[0025] The parameters used for the bonding of PC to group two metallic substrates (aluminum and anodized aluminum) are set forth herein below. A TLM-120-WC laser, provided by IPG Photonics of Oxford, Mass., was used for this portion of the invention. The 1940.2 nm laser was operated at a speed of 280 mm/s. Where the distance between lines was 0.50 mm and the power was 33%, 45 passes were made on each line. Where the distance between lines was 0.75 mm and the power was 33%, 30 passes per line were made.

[0026] Table 1 set forth below provides the data associated with the above experiments. It sets for the metallic substrate and accompanying polymer, as well as the strength of the maximum load. It accentuates that the materials were tested to a cohesive failure, rather than a failure of the bond.

TABLE-US-00001 TABLE 1 Thickness Thickness max. Sample Metal Polymer max. Load Laser # Metal (mm) Polymer (mm) Load Polymer Used 1 SS 304 0.25 HD-Polyethylene 1.6 1250N 1290N YLPP 2 SS 304 0.25 thick Polycarbonate 2.85 1345N 4810N YLPP 3 SS 304 0.25 thin Polycarbonate 0.25 400N 400N YLPP 4 SS 304 0.25 ABS 40 0.7 830N 890N YLPP 5 SS 304 0.25 Copolyester TRITAN 3.4 960N YLPP Mx711 6 SS 304 0.25 Copolyester Tx 2000 0.25 570N 630N YLPP 7 SS 304 0.25 PVC 0.5 690N YLPP 8 SS 304 0.25 PMMA 1.25 780N YLPP 9 AL66-20 0.5 HD Polyethylene 1.6 850N 1290N YLP 10 AL66-20 0.5 thick Polycarbonate 2.85 4810N YLPP 11 AL66-20 0.5 thin Polycarbonate 0.25 400N YLPP 12 ano Al 0.4 HD Polyethylene 1.6 1065N 1290N YLP 13 ano Al 0.4 thick Polycarbonate 2.85 1375N 4810N YLPP 14 ano Al 0.4 thin Polycarbonate 0.25 400N YLPP 15 ano Al 0.4 Copolyester TRITAN 3.4 980N YLPP Mx711 16 Titanium 0.2 HD Polyethylene 1.6 1090N 1290N YLPP 17 Titanium 0.2 thick Polycarbonate 2.85 1550N 4810N YLPP 18 Titanium 0.2 thin Polycarbonate 0.25 380N 400N YLPP 19 Nitinol 0.25 HD Polyethylene 1.6 1050N 1290N YLPP 20 Nitinol 0.25 thick Polycarbonate 2.85 4810N YLPP 21 Nitinol 0.25 thin Polycarbonate 0.25 400N YLPP

[0027] Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments of the invention described herein. The disclosed experiments and the impetus for the presently disclosed compositions and methods lie in the use of the materials, lasers and testing methodology available to the inventors. It is therefore to be understood that the foregoing embodiments are presented by way of example only and that within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described. The present disclosure is directed to each individual feature, system, material and/or method described herein. In addition, any combination of two or more such features, systems, materials and/or methods, if such features, systems, materials and/or methods are not mutually inconsistent, is included within the scope of the present invention.