EP4739743A1 - Methods of metallizing polypropylene compounds and metallized articles thereof - Google Patents

Abstract

Disclosed are methods that involve bonding a metal layer to thermoplastic that comprises (a) polypropylene and (b) one or more of the following polar polymers: polyvinylpyrrolidone, polypropyelene acrylic acid, polyethylene acrylic acid, poly(vinyl alcohol), ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, and polymethacrylate, wherein the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%. Also disclosed are articles comprising the metallized thermoplastic.

Description

METHODS OF METALLIZING POLYPROPYLENE COMPOUNDS AND METALLIZED ARTICLES THEREOF

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of priority from European Patent Application No. EP23183981 filed July 6, 2023, the disclosure of which is incorporated herein by reference in its entirety.

FIELD

[0002] The present disclosure generally relates to compounds that comprise propylene (polypropylene compounds). More specially, the present disclosure relates to metallizing polypropylene compounds and metallized articles thereof.

BACKGROUND

[0003] In recent years, manufacturers have increased the use of metallized plastic components in a variety of products. For example, metallized polymer components are used in electrical and electronic (E&E) devices, automotive equipment, computer body parts, office equipment, machinery, and packaging. Typically, metal deposition on plastic surfaces is accomplished by techniques such as electroless plating, electroplating, and the like. Key challenges in electroless plating of plastic’s polymer surface is creating a strong and durable adhesion between metal and the polymer, as they have properties that make them inherently incompatible with each other; for example, they have disparate surface energies and coefficient of thermal expansions (CTEs). Generally, to promote a strong adhesion of metal to a polymer surface, chemical and/or surface morphological changes have to be made to the surface of the polymer substrate.

[0004] The conventional procedure used to make changes to the surface of the polymer substrate involves etching the polymer surface with strong oxidizing solutions such as hexachrome sulfuric acid or acidified potassium permanganate, prior to the electroless plating. This etching step results in (i) the formation of nano/micro-pores that allow the anchoring/nucleation of metal particles and/or the mechanical interlocking and/or (ii) the creation of polar groups such as hydroxyl, carbonyl, and carboxyl groups on the polymer surface. The efficiency of such etching step has been widely proven for certain thermoplastic polymers such as acrylonitrile-butadiene-styrene copolymer (ABS). In the ABS matrix, the butadiene (BD) domains are uniformly dispersed within the styrene acrylonitrile (SAN) in which the double bond of butadiene will get selectively etched with oxidizing agents leading to the formation of micro-cavities and polar groups. On the other hand, in the case of hydrophobic thermoplastic polymers such as polypropylene (PP), the above etching step is generally not effective.

[0005] It appears that several approaches have been explored to improve the adhesion of metal onto polypropylene substrates. For example, pre-treatments such as flame treatment, corona discharge treatment, plasma treatment, grafting of glycidyl methacrylate, and grafting of maleic anhydride have been suggested to enhance the adhesion of metal onto substrate. Melt blending of chelating monomers such as methacrylate, maleimide, and metal-bonding groups in diketone and aspartic acid have also been used with polypropylene to functionalize the polymer and enhance the metal adhesion. Low polarity rubber, and homopolymer or copolymer ethylene, mineral additives and carbon black have also been used to enhance the adhesion of metal onto polypropylene.

BRIEF SUMMARY

[0006] There is a need for polypropylene compounds that are amenable to metallization with standard electroless plating and electroplating processes. The present thermoplastic polypropylene compounds are amenable to etching as a result of polar polymers included in them.

[0007] Some configurations of the disclosure include a method that comprises bonding a metal layer to thermoplastic that comprises (a) polypropylene and (b) one or more of the following polar polymers (which can be copolymers): polyvinylpyrrolidone, polypropylene acrylic acid, polyethylene acrylic acid, poly(vinyl alcohol), ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, and polymethacrylate, wherein the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%.

[0008] Some configurations of the disclosure include a method that comprises etching a surface of a thermoplastic that comprises (a) polypropylene and (b) one or more of the following polar polymers: polyvinylpyrrolidone, polypropylene acrylic acid, polyethylene acrylic acid, poly(vinyl alcohol), ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, and polymethacrylate, wherein the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%; and after etching the surface of the thermoplastic, bonding a metal layer to the thermoplastic.

[0009] Some configurations of the disclosure include a metallized article that comprises a metal layer bonded to thermoplastic that comprises (a) polypropylene and (b) one or more of the following polar polymers (which can be copolymers): polyvinylpyrrolidone, polypropylene acrylic acid, polyethylene acrylic acid, poly(vinyl alcohol), ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, and polymethacrylate, wherein the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%.

[0010] Some configurations of the disclosure include a metallized thermoplastic article that comprises a metal layer bonded to thermoplastic that comprises (a) polypropylene; (b) an inorganic additive; and (c) one or more of the following polar polymers: polyvinylpyrrolidone, polypropylene acrylic acid, polyethylene acrylic acid, poly(vinyl alcohol), ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, and polymethacrylate, wherein the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%.

[0011] The following includes definitions of various terms and phrases used throughout this specification.

[0012] The terms “about” or “approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1%, and most preferably, within 0.5%.

[0013] For the purposes of this disclosure, “X, Y, and/or Z” can be construed as X only,

Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XY, XZ, YZ). [0014] The terms “wt. %”, “vol. %” or “mol. %” refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol. % of component.

[0015] The term “substantially” and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0016] The terms “inhibiting” or “reducing” or “preventing” or “avoiding” or any variation of these terms, when used in the claims and/or the specification, include any measurable decrease or complete inhibition to achieve a desired result.

[0017] The term “effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0018] The use of the words “a” or “an” when used in conjunction with the term “comprising,” “including,” “containing,” or “having” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

[0019] The words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0020] The process of the present disclosure can “comprise,” “consist essentially of,” or “consist of’ particular ingredients, components, compounds, etc., disclosed throughout the specification.

[0021] The term “primarily,” as that term is used in the specification and/or claims, means greater than any of 50 wt. %, 50 mol. %, and 50 vol. %. For example, “primarily” may include 50.1 wt. % to 100 wt. % and all values and ranges there between, 50.1 mol.% to 100 mol.% and all values and ranges there between, or 50.1 vol. % to 100 vol. % and all values and ranges there between. [0022] Other objects, features and advantages of the present disclosure will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the disclosure, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0024] FIG. 1 depicts a conceptual flowchart of an example of the present methods of preparing polypropylene compounds for metallization and metallization of such compounds.

[0025] FIG. 2 is a graph depicting peel strength with respect to different metallized polypropylene compounds.

DETAILED DESCRIPTION

[0026] In implementations of this disclosure, polypropylene is melt blended with adhesion promoting additives such as one or more of polyethylene acrylic acid, polypropylene acrylic acid, butadiene grafted styrene acrylonitrile, poly(vinyl alcohol), polyvinylpyrrolidone, ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, and styrene maleic anhydride; and/or reinforcing additives (fillers) such as one or more of aluminum oxide, zinc oxide, titanium dioxide, zirconium oxide, calcium carbonate, talc, silica, glass beads, hallow glass beads, glass fibers, aluminum oxide fibers, carbon fibers, graphene, and alumina trihydrate. An optimal loading of one or more of these additives can result in polypropylene compounds that exhibit high metal adhesion as well as mechanical, thermal and electrical properties necessitated for the target application. [0027] It is expected that incorporation of one or more of polyethylene acrylic acid, polypropylene acrylic acid, butadiene grafted styrene acrylonitrile, poly(vinyl alcohol), polyvinylpyrrolidone, ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, and styrene maleic anhydride, into polypropylene can help to increase the surface polarity (due to preferential migration of these additive to the surface) to make the surface of polypropylene amenable to etching, which can involve the use of any of hexa-chrome sulfuric acid (HCSA), tri-chrome, potassium permanganate, and manganese-based etching solutions, or a combination thereof.

[0028] With respect to polypropylene compounds that comprise one or more of aluminum oxide, zinc oxide, titanium dioxide, zirconium oxide, calcium carbonate, talc, silica, glass beads, hallow glass beads, glass fibers, aluminum oxide fibers, carbon fibers, graphene, and alumina trihydrate as reinforcing additives.

[0029] After the etching step, colloidal palladium/tin can be deposited into the micropores by a chemical redox reaction, then metallization can be carried out as per standard electroless and/or electroplating processes. Additives such as hollow glass beads, glass and other ceramic fibers can also be included as a component in the thermoplastic polypropylene compound to accomplish better mechanical, thermal and electrical properties as required for a particular end-use application.

[0030] The thermoplastic polypropylene compounds of the present disclosure can be made by various methods known in the art. For example, components, such as polypropylene, polar polymer(s), reinforcing additive(s), and processing additive(s), can be mixed together and then melt-blended to form the polypropylene compound. The melt blending of the components can include use of shear force, extensional force, compressive force, ultrasonic energy, electromagnetic energy, thermal energy or combinations comprising at least one of the foregoing forces or forms of energy.

[0031] In some aspects, the one or any foregoing components described herein may be first blended such as dry blended with each other such as by hand mixing or in a high-speed mixer. The blend can then be fed into the throat of a twin-screw extruder via a hopper. In some aspects, at least one of the components can be incorporated by feeding it directly into the extruder at the throat and/or downstream through a side stuffer, or by being compounded into a master batch with polypropylene and fed into the extruder. The extruders used in the present disclosure may have a single screw, multiple screws, intermeshing co-rotating or counter rotating screws, non-intermeshing co-rotating or counter rotating screws, reciprocating screws, screws with pins, screws with screens, barrels with pins, rolls, rams, helical rotors, co-kneaders, disc-pack processors, various other types of extrusion equipment, or combinations comprising at least one of the foregoing. The extruder can generally be operated at a temperature higher than that necessary to cause the composition to melt and flow. In some aspects, the temperature of the melt in the extruder barrel can be maintained as low as possible in order to avoid excessive thermal degradation of the components. The melted compound exits the extruder through small exit holes in a die. The extrudate can be quenched in a water bath and pelletized. The pellets so prepared can be of any desired length (e.g., one-fourth inch long or less). Such pellets can be used for subsequent molding, shaping, or forming.

[0032] Mixtures including any combination of the foregoing mentioned components can be subjected to multiple blending and forming steps if desirable. For example, the thermoplastic polypropylene compound may first be extruded and formed into pellets. The pellets may then be fed into a molding machine where it may be formed into any desirable shape or product. In some aspects, the thermoplastic polypropylene compound emanating from a single melt blender may be formed into sheets or strands and subjected to post-extrusion processes such as annealing, uniaxial or biaxial orientation.

[0033] Shaped, formed, casted, or molded articles comprising the thermoplastic polypropylene compounds are also provided. The thermoplastic polypropylene compounds can be molded into useful shaped articles by a variety of methods, such as injection molding, compression molding, extrusion, rotational molding, blow molding, 3D printing, additive manufacturing and thermoforming. The article can be a molded article, a thermoformed article, an extruded film, an extruded sheet, a honeycomb structure, one or more layers of a multi-layer article, a substrate for a coated article, and a substrate for a metallized article (e.g, an article that includes the thermoplastic polypropylene compound coated with a metal layer).

[0034] Referring to FIG. 1 , aspects of the disclosure include a method 10 of metallizing a polypropylene compound. As shown in FIG. 1, method 10 includes, at block 100, meltblending of polypropylene with one or more of polar polymers and inorganic additives to form a thermoplastic polypropylene compound. In some configurations, the polar polymers that are melt-blended and thereby comprised in the thermoplastic polypropylene compound can be one or more of polyethylene acrylic acid, polypropylene acrylic acid, butadiene grafted styrene acrylonitrile, poly(vinyl alcohol), polyvinylpyrrolidone, ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, and styrene maleic anhydride. In some configurations, the thermoplastic polypropylene compound comprises 0.5 wt. % to 30 wt. % or any range therein, including 0.5 wt. % to 5 wt. %, 5 wt. % to 10 wt. %, 10 wt. % to 15 wt. %, 15 wt. % to 20 wt. %, 20 wt. % to 25 wt. %, 25 wt. % to 30 wt. %, 5 wt. % to 25 wt. %, and 10 wt. % to 20 wt. % of the one or more polar polymers. In some configurations, the thermoplastic polymer compound comprises one or more polar polymers where the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%, or any range therein, including 5% to 10%, 10% to 15%, 15% to 20%, 20% to 25%, 25% to 30%, 30% to 35%, 35% to 40%, 40% to 45%, 45% to 50%, 50% to 55%, 55% to 60%, 60% to 65%, 65% to 70%, 70% to 75%, 75% to 80%, 80% to 85%, 85% to 90%, 90% to 95%, 95% to 100%, 10% to 95%, 15% to 90%, 20% to 85%, 25% to 80%, 30% to 75%, 35% to 70%, 40% to 75%, 45% to 70%, and 50% to 65%. The percentage of polar groups in the polar copolymer indicates the weight percentage of polar comonomer present in the copolymer.

[0035] In some configurations, the inorganic additives that are melt-blended and thereby comprised in the thermoplastic polypropylene compound can be one or more of aluminum oxide, zinc oxide, titanium dioxide, zirconium oxide, calcium carbonate, talc, silica, glass beads, hallow glass beads, glass fibers, aluminum oxide fibers, carbon fibers, graphene, and alumina trihydrate. In some compositions that comprise one or more inorganic additives, the one or more inorganic additives improve peel strength of a bond between the metal layer and the thermoplastic (see TABLE 2 below). The inorganic additives, in some compositions, act as reinforcing agents that enhance the mechanical (tensile modulus and strength) and thermal (heat deflection temperature, warpage, coefficient of thermal expansion) properties of the compositions. A combination of polar additives and inorganic additives, in some compositions, can also help to improve metal adhesion to thermoplastic when such thermoplastic is metallized. The melt-blending can be carried out in an extruder or in a melt blender. In some configurations, the thermoplastic polypropylene compound comprises 5.0 wt. % to 40 wt. % or any range therein, including 5 wt. % to 10 wt. %, 10 wt. % to 15 wt. %, 15 wt. % to 20 wt. %, 20 wt. % to 25 wt. %, 25 wt. % to 30 wt. %, 30 wt. % to 35 wt. %, 35 wt. % to 40 wt. %, 10 wt. % to 35 wt. %, and 15 wt. % to 30 wt. % of the one or more inorganic additives. [0036] In some configurations, the thermoplastic polypropylene compound comprises 28 wt. % to 95 wt. %, or any range therein, including 28 wt. % to 94.5 wt.%, 30 wt. % to 95 wt. %, 28 wt. % to 93 wt. %, 30 wt. % to 35 wt. %, 35 wt. % to 40 wt. %, 40 wt. % to 45 wt. %, 45 wt. % to 50 wt. %, 50 wt. % to 55 wt. %, 55 wt. % to 60 wt. %, 60 wt. % to 65 wt. %, 65 wt. % to 70 wt. %, 70 wt. % to 75 wt. % 75 wt. % to 80 wt. %, 80 wt. % to 85 wt. %, 85 wt. % to 90 wt. %, and 90 wt. % to 95 wt. %, 30 to 94.5 wt. %; 30 to 70 wt. %; 40 to 70 wt. %; 40 to 60 wt. %; 45 to 60 wt. %; 47 to 59 wt. %, 47 to 55 wt. %, and 47 to 50 wt. % of polypropylene. In some aspects, the thermoplastic polypropylene compound comprises 30 wt. % to 95 wt. % polypropylene, along with 2 wt. % of processing additives comprising: 0. 1 wt. % of antioxidant (for example, Irganox-1010), 0.1 wt. % of heat stabilizer (for example, Irgafos-168), 0.2 wt. % of nucleating agent (for example, talc), and 1.6 wt. % of coupling agent (for example, maleic anhydride functionalized polypropylene such as Exxelor™ P0 1020).

[0037] In the depicted example, block 101 includes etching the surface of the thermoplastic polypropylene compound with an oxidizing agent. The oxidizing agent can include any of hexa-chrome sulfuric acid (HCSA), tri-chrome, potassium permanganate, and manganese-based etching solutions, or a combination thereof. In some configurations, the etching of the surface, at block 101, is carried out at a temperature of 25 to 80 °C and any range therein, including 25 to 30 °C, 30 to 35 °C, 35 to 40 °C, 40 to 45 °C, 45 to 50 °C, 50 to 55 °C, 55 to 60 °C, 60 to 65 °C, 65 to 70 °C, 70 to 75 °C, 75 to 80 °C, 30 to 75 °C, 35 to 70 °C, 40 to 65 °C, and 45 to 60 °C for a period in a range of 5 to 60 minutes and any range therein, including 5 to 10 minutes, 10 to 15 minutes, 15 to 20 minutes, 20 to 25 minutes, 25 to 30 minutes, 30 to 35 minutes, 35 to 40 minutes, 40 to 45 minutes, 45 to 50 minutes, 50 to 55 minutes, and 55 to 60 minutes, 10 to 55 minutes, 15 to 50 minutes, 20 to 45 minutes, and 25 to 40 minutes.

[0038] In the depicted example, method 10, at block 102, can comprise depositing colloidal palladium/tin into micro-pores on the surface of the thermoplastic polypropylene compound via a chemical redox reaction. In some configurations, the depositing of the colloidal palladium/tin, at block 102, is carried out at a temperature of 25 to 50 °C for 1 to 10 minutes. In the depicted example, in method 10 after each of block 101 and block 102, the thermoplastic polypropylene compound can be rinsed with water before proceeding to the next step.

[0039] In the depicted example, block 103 involves attaching a metal layer to the etched surface of the thermoplastic polypropylene compound. In this way, the attaching or bonding is between the metal layer and the etched surface. Such bonding can be carried out by electroless plating or a combination of electroless plating and electroplating. In some configurations, the attaching of the metal layer to the thermoplastic polypropylene compound includes an electroless process. And in some configurations, the attaching of the metal layer includes an electroplating process. The metal that is attached to the thermoplastic polypropylene compound can be any one of nickel, copper, chromium, aluminum, silver, gold, platinum, and an alloy thereof.

[0040]

[0041] One suitable measure of the success of bonding between the metal layer and the thermoplastic polypropylene compound is by measuring the peel strength, where the greater the peel strength the better is the adherence of the metal on the thermoplastic polypropylene compound. In some configurations, the peel strength of the bond between the metal layer and the etched surface of the thermoplastic polypropylene compound is >0.10 N/mm, or any range therein, including 0.10 to 2 N/mm, 0.10 to 0.20 N/mm, 0.20 to 0.30 N/mm, 0.30 to 0.40 N/mm, 0.40 to 0.50 N/mm, 0.50 to 0.60 N/mm, 0.60 to 0.70 N/mm, 0.70 to 0.80 N/mm, 0.80 to 0.90 N/mm, 0.90 to 1.0 N/mm, 1.0 to 1.10 N/mm, 1.10 to 1.20 N/mm, 1.20 to 1.30 N/mm, 1.30 to 1.40 N/mm, 1.40 to 1.50 N/mm, 1.50 to 1.60 N/mm, 1.60 to 1.70 N/mm, 1.70 to 1.80 N/mm, 1.80 to 1.90 N/mm, and 1.90 to 2.0 N/mm, 0.20 to 1.9 N/mm, 0.30 to 1.8 N/mm, 0.40 to 1.7 N/mm, 0.50 to 1.6 N/mm, 0.60 to 1.5 N/mm, 0.70 to 1.4 N/mm, 0.80 to 1.3 N/mm, and 0.90 to 1.2 N/mm, 0.20 to 2 N/mm, 0.30 to 1.9 N/mm, 0.40 to 1.80 N/mm, 0.50 to 1.70 N/mm, 0.60 to 1.60 N/mm, 0.70 to 1.50 N/mm, 0.80 to 1.40 N/mm, 0.90 to 1.30N/mm, and l.O to 1.20 N/mm.

[0042] The metallized polypropylene compounds disclosed herein can be used to make a metallized article such as plurality of different components in one or more of the following: a component used in an electrical or electronic device, a component of a telecommunication device, radio-frequency (RF) filter, EMI shielding, wave-guide, antenna substrate, frequency selective surfaces, components of appliance, packaging, automotive interior components, automotive exterior components, badges, trims, electrical vehicle battery cover, and thermal management component.

[0043] Although aspects of the present invention have been described with reference to blocks of FIG. 1 should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIG. 1. Accordingly, aspects of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIG. 1.

[0044] The systems and processes described herein can also include various equipment that is not shown and is known to one of skill in the art of chemical processing. For example, some controllers, piping, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, and the like may not be shown.

[0045] As part of the disclosure, specific examples are included below. The examples are for illustrative purposes only and are not intended to limit the invention. Those of ordinary skill in the art will readily recognize parameters that can be changed or modified to yield essentially the same results.

EXAMPLE

Peel Strength Tests

[0046] A first set of polypropylene compositions were prepared to include components as follows: (1) composition 1: 68 wt. % polypropylene (PP) and 30 wt.% short glass fibers (SGF); (2) composition 2: 58 wt. % polypropylene, 30 wt. % short glass fibers (SGF), and 10 wt. % polyvinylpyrrolidone (PVP); (3) composition 3: 48 wt. % polypropylene, 30 wt. % short glass fibers (SGF), and 20 wt. % polyethylene acrylic acid; and (4) composition 4: 58 wt. % polypropylene, 30 wt. % short glass fibers (SGF), and 10 wt. % poly(vinyl alcohol) (PVOH). All above compositions (1-4) also include 2 wt. % of processing additives comprising of 0.1 wt. % of antioxidant (Irganox-1010), 0.1 wt. % of heat stabilizer (Irgafos-168), 0.2 wt. % of nucleating agent (talc), and 1.6 wt. % of coupling agent (maleic anhydride functionalized polypropylene (Exxelor™ PO 1020)). The peel strength of each of these compositions were tested using the test method of ASTM B533-85 and FIG. 2 shows the results obtained from such tests. No metal plating was evident for the composition 1, which does not contain any polar additives and thus the results for composition 1 are not reflected in FIG. 2. Relatively good metal plating was evident for the composition 2, composition 3, and composition 4, each having a different polar additive. Comparing the different polypropylene compositions with polar additives, the polypropylene compositions comprising polyethylene acrylic acid (composition 3) and poly(vinyl alcohol) (composition-4) possessed a relatively higher peel strength, as compared to that observed with the polypropylene composition comprising polyvinylpyrrolidone (composition 2). The peel strength of each of these compositions were tested using the test method of ASTM B533-85 and FIG. 2 shows the results obtained from such tests.

TABLE 1

[0047] Table 1 shows a summary of the mechanical and thermal performance of the different polypropylene compositions 1 to 4. Dielectric constant of plastic indicates the ability of the plastic to store electrical energy. Dissipation factor indicates the inefficiency of material to hold energy or behave as an insulating material. As can be seen from Table 1, with composition 1 as reference, a significant increase in dielectric constant (Dk) and dissipation factor (DI values was observed with incorporation of PVP and PVOH in compositions 2 and 4 respectively. However, incorporation of PE-AA, in composition 3, did not show much impact on the Dk and Df values, where the values for composition 1 were used as a reference. Tensile modulus is a measure of a material’s stiffness. Heat distortion temperature (HDT) is a measure of a material’s ability to resist force. Table 1 shows that, with composition 1 as a reference, there is a decrease in tensile modulus and HDT in the case of composition 3 (PP with 20% PEAA) as compared to increases observed with the use of other polar polymers such as PVP in composition 2 and PVOH in composition 4. The results in Table 1 suggests that higher tensile modulus and HDT can be achieved using a lower amount of PEAA loading (e.g., 1 to 10) based on the needs of target applications.

[0048] A second set of polypropylene compositions were prepared to include components as follows: (a) composition 5: 98 wt.% polypropylene; (b) composition 6: 78 wt. % polypropylene (PP) and 20 wt.% short glass fibers (SGF); (c) composition 7: 78 wt. % polypropylene, 10 wt. % short glass fibers (SGF), and 10 wt. % poly(vinyl alcohol) (PVOH); (d) composition 8: 68 wt. % polypropylene, 20 wt. % short glass fibers (SGF), and 10 wt. % poly(vinyl alcohol) (PVOH); and (e) composition 9: 76 wt. % polypropylene, 20 wt. % short glass fibers (SGF), and 2 wt. % poly(vinyl alcohol) (PVOH); (f) composition 10: 73 wt. % polypropylene, 20 wt. % short glass fibers (SGF), and 5 wt. % poly (vinyl alcohol) (PVOH). Each of compositions 5 to 10 includes 2 wt. % of processing additives comprising of 0.1 wt. % of antioxidant (Irganox-1010), 0.1 wt. % of heat stabilizer (Irgafos-168), 0.2 wt. % of nucleating agent (talc), and 1.6 wt. % of coupling agent (maleic anhydride functionalized polypropylene (Exxelor™ PO 1020)). The processes of injection molding of samples and coating of the metal surface were the same for all compositions 1 to 10, except that for composition 7, the injection molding was carried out at 220 °C and for the other samples it was carried out at 240 °C. The peel strength of each of these compositions were tested using the test method of ASTM B533-85 and TABLE 2 shows the results obtained from such tests.

TABLE 2

[0049] TABLE 2 shows the plating quality and peel strength with respect to change in SGF content and PVOH content. As can be seen in TABLE 2, as SGF content increases, peel strength increases. However, it should be noted that above a certain level, the amount of SGF may negatively affect other mechanical properties such as brittleness. [0050] In the context of the present disclosure, at least the following 15 aspects are described. Aspect 1 is a method comprising etching a surface of a a metal layer to thermoplastic. The method comprises (a) polypropylene and (b) one or more of the following polar polymers: polyvinylpyrrolidone, polypropylene acrylic acid, polyethylene acrylic acid, poly(vinyl alcohol), ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, and polymethacrylate, wherein the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%; and after etching the surface of the thermoplastic, bonding a metal layer to the thermoplastic. Aspect 2 is the method of aspect 1, wherein the thermoplastic comprises 0.5 wt. % to 30 wt. % of the one or more polar polymers. Aspect 3 is the method of any of aspects 1 and 2, wherein the thermoplastic comprises 5 wt. % to 40 wt.% of an inorganic additive. Aspect 4 is the method of aspect 3, wherein the inorganic additive comprises one or more of the following: aluminum oxide, zinc oxide, titanium dioxide, zirconium oxide, calcium carbonate, talc, silica, glass beads, hallow glass beads and glass fibers, aluminum oxide fibers, carbon fibers, and graphene. Aspect 5 is the method of any of aspects 1 to 4, wherein the thermoplastic comprises 28 wt. % to 93 wt. % polypropylene. Aspect 6 is the method of any of aspects 1 to 5, wherein etching the surface of the thermoplastic comprises etching a surface of the thermoplastic with an oxidizing agent. Aspect 7 is the method of aspect 6, wherein the oxidizing agent comprises any of hexa-chrome sulfuric acid (HCSA), tri-chrome, potassium permanganate, and manganese-based etching solutions, or a combination thereof. Aspect 8 is the method of any of aspects 6 and 7, wherein (i) the bonding is between the metal layer and the etched surface and (ii) the bonding is carried out by electroless plating or a combination of electroless plating and electroplating. Aspect 9 is the method of any of aspects 1 to 8, wherein the bond between the metal layer and the thermoplastic has a peel strength of 0.2 to 2 N/mm.

[0051] Aspect 10 is a metallized thermoplastic article. The metallized thermoplastic article comprises a metal layer bonded to thermoplastic that comprises (a) polypropylene, (b) an inorganic additive, and (c) one or more of the following polar polymers: polyvinylpyrrolidone, polypropylene acrylic acid, polyethylene acrylic acid, poly(vinyl alcohol), ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, and polymethacrylate, wherein the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%. Aspect 11 is the article of aspect 10, wherein the thermoplastic comprises 0.5 wt. % to 30 wt. % of the one or more polar polymers. Aspect 12 is the article of any of aspects 10 and 11, wherein the thermoplastic comprises 5 wt. % to 40 wt.% of the inorganic additive. Aspect 13 is the article of aspect 12, wherein the inorganic additive comprises one or more of the following: aluminum oxide, zinc oxide, titanium dioxide, zirconium oxide, calcium carbonate, talc, silica, glass beads, hallow glass beads and glass fibers, aluminum oxide fibers, carbon fibers, and graphene. Aspect 14 is the article of any of aspects 10 to 13, wherein the thermoplastic comprises 30 wt. % to 95 wt.% polypropylene. Aspect 15 is the article of any of aspects 10 to 14, wherein the article is configured to be comprised in one or more of the following: an electrical or electronic device, a component of a telecommunication device, radio-frequency (RF) filter, EMI shielding, wave-guide, antenna substrate, frequency selective surface, components of appliances, packaging, automotive interior components, automotive exterior components, badges, trims, electrical vehicle battery cover, and thermal management component.

[0052] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, compound of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compounds of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compounds of matter, means, methods, or steps.

Claims

CLAIMS What is claimed is:

1. A method comprising: etching a surface of a thermoplastic that comprises (a) polypropylene and (b) one or more of the following polar polymers: polyvinylpyrrolidone, polypropylene acrylic acid, polyethylene acrylic acid, poly(vinyl alcohol), ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, and polymethacrylate, wherein the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%; and after etching the surface of the thermoplastic, bonding a metal layer to the thermoplastic.

2. The method of claim 1, wherein the thermoplastic comprises 0.5 wt. % to 30 wt. % of the one or more polar polymers.

3. The method of any of claims 1 and 2, wherein the thermoplastic comprises 5 wt. % to 40 wt.% of an inorganic additive.

4. The method of claim 3, wherein the inorganic additive comprises one or more of the following: aluminum oxide, zinc oxide, titanium dioxide, zirconium oxide, calcium carbonate, talc, silica, glass beads, hallow glass beads and glass fibers, aluminum oxide fibers, carbon fibers, and graphene.

5. The method of any of claims 1 to 4, wherein the thermoplastic comprises 30 wt. % to 95 wt. % polypropylene.

6. The method of any of claims 1 to 5, wherein etching the surface of the thermoplastic comprises etching a surface of the thermoplastic with an oxidizing agent.

7. The method of claim 6, wherein the oxidizing agent comprises any of hexachrome sulfuric acid (HCSA), tri-chrome, potassium permanganate, and manganese-based etching solutions, or a combination thereof.

8. The method of any of claims 6 and 7, wherein (i) the bonding is between the metal layer and the etched surface and (ii) the bonding is carried out by electroless plating or a combination of electroless plating and electroplating.

9. The method of any of claims 1 to 8, wherein the bond between the metal layer and the thermoplastic has a peel strength of 0.2 to 2 N/mm.

10. A metallized thermoplastic article comprising: a metal layer bonded to thermoplastic that comprises:

(a) polypropylene;

(b) an inorganic additive; and

(c) one or more of the following polar polymers: polyvinylpyrrolidone, polypropylene acrylic acid, polyethylene acrylic acid, poly(vinyl alcohol), ethylene vinyl alcohol, polypropylene acrylate, polyethylene acrylate, polypropylene methacrylate, polyethylene methacrylate, polyacrylic acid, polymethacrylic acid, polyacrylate, and polymethacrylate, wherein the percentage of polar groups in the one or more polar polymers is in a range of 5% to 100%.

11. The article of claim 10, wherein the thermoplastic comprises 0.5 wt. % to 30 wt. % of the one or more polar polymers.

12. The article of any of claims 10 and 11, wherein the thermoplastic comprises 5 wt. % to 40 wt.% of the inorganic additive.

13. The article of claim 12, wherein the inorganic additive comprises one or more of the following: aluminum oxide, zinc oxide, titanium dioxide, zirconium oxide, calcium carbonate, talc, silica, glass beads, hallow glass beads and glass fibers, aluminum oxide fibers, carbon fibers, and graphene.

14. The article any of claims 10 to 13, wherein the thermoplastic comprises 30 wt. % to 95 wt.% polypropylene.

15. The article of any of claims 10 to 14, wherein the article is configured to be comprised in one or more of the following: an electrical or electronic device, a component of a telecommunication device, radio-frequency (RF) filter, EMI shielding, wave-guide, antenna substrate, frequency selective surface, components of appliances, packaging, automotive interior components, automotive exterior components, badges, trims, electrical vehicle battery cover, and thermal management component.