Description:BACKGROUND

FIELD OF THE DISCLOSURE
[0001] Various embodiments of the disclosure relate generally to acrylonitrile-butadiene-styrene vitrimers. More specifically, various embodiments of the disclosure relate to processing acrylonitrile-butadiene-styrene to form the vitrimers.

DESCRIPTION OF THE RELATED ART

[0002] In the era of globalization, plastics have become an essential part of everyday life, with applications ranging from household items to advanced aerospace materials. Acrylonitrile-butadiene-styrene (ABS) is a versatile terpolymer valued for its high impact strength, durability, and toughness. The acrylonitrile component contributes chemical resistance, the butadiene component provides toughness and impact resistance, while the styrene component adds rigidity and ease of processing, making ABS a widely used polymer.
[0003] ABS is used in a wide range of products, from LEGO® bricks to electrical and electronic equipment. According to a 2020 United Nations (UN) report, 53.6 million metric tonnes of electronic waste were generated in 2019, a figure projected to rise to 74.7 million metric tonnes by 2030. Of this, only 17.4% was recycled, with the remainder discarded, exacerbating the growing environmental concerns.
[0004] In pursuit of a circular plastics economy, recycling plastic waste is crucial to reducing reliance on fossil fuels for the production of virgin plastics. Most current recycling methods focus on open-loop recycling, which often results in products of lower quality, a process known as downcycling. Moreover, these processes typically require the addition of virgin polymers to meet performance standards. In contrast, closed-loop recycling aims to maintain or enhance the quality of recycled materials, producing final products with comparable or superior properties in an upcycling approach. Although ABS can be mechanically recycled due to its thermoplastic nature, the recycled material generally exhibits inferior mechanical strength to virgin ABS. There is an unmet need for a recycling process that can convert ABS waste into high-quality feedstock with mechanical properties comparable to those of virgin ABS.
[0005] Limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of described systems with some aspects of the present disclosure, as set forth in the remainder of the present application and with reference to the drawings.
SUMMARY

[0006] According to embodiments of the present disclosure, an acrylonitrile-butadiene-styrene (ABS)-vitrimer is provided. The acrylonitrile-butadiene-styrene (ABS)-vitrimer comprises a maleic-acrylonitrile-butadiene-styrene comprising a maleic sidechain on butadiene unit of an acrylonitrile-butadiene-styrene (ABS). The acrylonitrile-butadiene-styrene (ABS) vitrimer further comprises a dynamic crosslinker linked to the maleic sidechain and forms covalent adaptive networks to form the acrylonitrile-butadiene-styrene-vitrimer. The dynamic crosslinker comprises 4,4’-methylenebis(N, N-diglycidylaniline) (MDGA), bisphenol A diglycidyl ether (BADGE), or combinations thereof.
[0007] In another embodiment, a method of processing an acrylonitrile-butadiene-styrene (ABS) is provided. The method comprises performing a first extrusion of the acrylonitrile-butadiene-styrene with maleic anhydride at a temperature in a range of 200 to 240 °C to form a maleated acrylonitrile-butadiene-styrene. The method further comprises performing a second extrusion of the maleated acrylonitrile-butadiene-styrene with a dynamic crosslinker at a temperature in a range of 200 to 240 °C to form an acrylonitrile-butadiene-styrene-vitrimer having a tensile strength greater than a tensile strength of the acrylonitrile-butadiene-styrene (ABS). The dynamic crosslinker comprises 4,4’-methylenebis(N, N-diglycidylaniline) (MDGA), bisphenol A diglycidyl ether (BADGE), or combinations thereof.
[0008] In yet another embodiment, an article comprising an acrylonitrile-butadiene-styrene (ABS)-vitrimer is provided. The acrylonitrile-butadiene-styrene (ABS)-vitrimer comprises a maleic-acrylonitrile-butadiene-styrene comprising a maleic sidechain on butadiene unit of an acrylonitrile-butadiene-styrene (ABS). The acrylonitrile-butadiene-styrene (ABS) vitrimer further comprises a dynamic crosslinker linked to the maleic sidechain and forms covalent adaptive networks to form the acrylonitrile-butadiene-styrene-vitrimer. The dynamic crosslinker comprises 4,4’-methylenebis(N, N-diglycidylaniline) (MDGA), bisphenol A diglycidyl ether (BADGE), or combinations thereof.

BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1 is a flow chart that illustrates a method of processing an acrylonitrile-butadiene-styrene (ABS), in accordance with an exemplary embodiment of the disclosure;
[0010] FIG. 2 is a reaction scheme of reaction between acrylonitrile-butadiene-styrene (ABS) and dynamic crosslinkers;
[0011] FIG. 3 corresponds to Fourier transform infrared (FTIR) spectra of acrylonitrile-butadiene-styrene (ABS) and maleated acrylonitrile-butadiene-styrene; and
[0012] FIG. 4 corresponds to Fourier transform infrared (FTIR) spectra of acrylonitrile-butadiene-styrene-vitrimers.
[0013] Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description of exemplary embodiments is intended for illustration purposes only and is, therefore, not intended to necessarily limit the scope of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0014] The following description illustrates some exemplary embodiments of the disclosed disclosure in detail. Those of skill in the art will recognize that there are numerous variations and modifications of this disclosure that are encompassed by its scope. Accordingly, the description of a certain exemplary embodiment should not be deemed to limit the scope of the present disclosure.
[0015] The term “comprising” as used herein is synonymous with “including,” or “containing,” and is inclusive or open-ended and does not exclude additional, unrecited elements, or process steps.
[0016] All numbers expressing quantities of ingredients, property measurements, and so forth used in the specification are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that may vary depending upon the desired properties sought to be obtained.
[0017] These and other features and advantages of the present disclosure may be appreciated from a review of the following detailed description of the present disclosure, along with the accompanying figures in which like reference numerals refer to like parts throughout.
[0018] Plastic recycling refers to a process whereby useful products may be produced from waste plastics after reprocessing, or melting the waste plastics. However, after recycling, the recycled polymer usually possesses inferior properties compared to its virgin counterparts. The extent of degradation may depend on degradation during use, cycle life, and the severity of conditions applied during reprocessing.
[0019] Vitrimers are a class of polymers containing reversible dynamic covalent bonds that can reorganize upon application of external stimuli allowing the material to be reshaped, repaired, or recycled while mostly retaining its original properties. Polymers containing dynamic covalent bonds are known to form covalent adaptable networks (CANs). The acrylonitrile-butadiene-styrene-vitrimers of the present disclosure, form associative CANs, which means that existing covalent bonds are only broken when new ones are formed. The formation of CANs through dynamic crosslinkers renders the acrylonitrile-butadiene-styrene -vitrimers recyclable or reprocessable.
[0020] The acrylonitrile-butadiene-styrene is a terpolymer (hereinafter, referred to as ABS polymer or ABS) comprising repeating units of styrene, acrylonitrile, and butadiene. A typical ABS polymer may have a repeating unit derived from butadiene at a weight percent in a range of 5 to 50%, a repeating unit derived from styrene in a range of 20 to 70 wt%, and a repeating unit derived from acrylonitrile in a range of 5 to 40 wt%, based on the total weight of the ABS polymer. The weight average molecular weight (Mw) of the ABS polymer may vary from 10,000 grams per mole (g/mol) to 500,000 g/mol. ABS, as used herein, also includes filled ABS, ABS blends, ABS copolymers, or combinations thereof.
[0021] As used herein, the term “copolymer” refers to a polymer derived from more than one species of monomer, where the copolymer includes repeating units of each of the monomers.
[0022] As used herein, the term “blend” refers to a mixture of two or more polymers or copolymers that have been blended together to create a new material with different physical properties.
[0023] As used herein, the term “filled ABS” refers to an ABS that has been reinforced with various filler materials to enhance its mechanical, thermal, or electrical properties. Examples of filler material include glass fibers, minerals such as talc, and calcium carbonate, carbon fibers, nanoclays, aramid fibers, or the like.
[0024] According to embodiments of the present disclosure, a method of processing an acrylonitrile-butadiene-styrene (ABS) is provided. The method comprises performing a first extrusion of the acrylonitrile-butadiene-styrene with maleic anhydride at a temperature in a range of 200 to 240 °C to form a maleated acrylonitrile-butadiene-styrene. The method further comprises performing a second extrusion of the maleated acrylonitrile-butadiene-styrene with a dynamic crosslinker at a temperature in a range of 200 to 240 °C to form an acrylonitrile-butadiene-styrene-vitrimer having a tensile strength greater than a tensile strength of the acrylonitrile-butadiene-styrene (ABS). The dynamic crosslinker comprises 4,4’-methylenebis(N, N-diglycidylaniline) (MDGA), bisphenol A diglycidyl ether (BADGE), or combinations thereof.
[0025] The processing of the acrylonitrile-butadiene-styrene, in one instance, relates to recycling of the acrylonitrile-butadiene-styrene. In some embodiments, the processing of the acrylonitrile-butadiene-styrene relates to forming the acrylonitrile-butadiene-styrene-vitrimer. The formation of the acrylonitrile-butadiene-styrene-vitrimer results in an upcycling of the acrylonitrile-butadiene-styrene whereby a mechanical property of the acrylonitrile-butadiene-styrene-vitrimer is on par or superior to a mechanical property of the acrylonitrile-butadiene-styrene it is formed from. As used herein, the term “upcycling” refers to processing of a polymer (recycling) to obtain a recycled polymer having mechanical properties on par, or superior to the parent polymer.
[0026] The mechanical properties of the ABS may be characterized in terms of tensile strength and/or elongation at break. When a tensile strength of the ABS is enhanced upon processing it implies that the processed ABS is of greater mechanical strength than that of the ABS. As used herein, the term “tensile strength” is defined as the maximum tensile load a material can withstand before it breaks. The tensile strength is determined using a tensile test and the tensile strength corresponds to the highest point of the stress-strain curve plotted from the test. “Elongation at break” is the maximum elongation of the material before it breaks/ruptures and is expressed in terms of a ratio between increased length and initial length at break point.
[0027] It is a particular advantage of the present disclosure, that commercially available epoxy monomers (hereinafter epoxy compounds) widely used to make epoxy polymers are employed as dynamic crosslinkers to upcycle acrylonitrile-butadiene-styrene. The economics of using commercial monomers along with melt extrusion process to facilitate the upcycling of ABS into ABS-vitrimers, is a facile, cost-effective, eco-friendly, and industrially adaptable process. As the mechanical properties of the ABS are enhanced upon processing, the ABS may be recycled several times. Thus, the present disclosure provides a method of processing ABS to enhance a cycle life of the ABS. As used herein, the term “cycle life” refers to the number of times a polymer may be recycled.
[0028] FIG. 1 is a flow chart 100 that illustrates a method of processing an acrylonitrile-butadiene-styrene through exemplary steps 102 through 104, according to embodiments of the present disclosure. At step 102, a first extrusion of the acrylonitrile-butadiene-styrene with maleic anhydride is performed to form a maleated acrylonitrile-butadiene-styrene.
[0029] The acrylonitrile-butadiene-styrene (ABS) comprises virgin ABS, post-consumer recycled (PCR) ABS, post-industrial recycled (PIR) ABS, or combinations thereof. Post-consumer recycled (PCR) plastics refer to plastic waste generated by consumers, or after-use plastic products. The composition of PCR plastics can vary significantly due to the diverse mix of polymers and additives used by different manufacturers. This variation in composition makes the recycling of PCR plastics more complex and challenging. In contrast, post-industrial recycled (PIR) plastics are derived from plastic waste produced during industrial and manufacturing processes. PIR plastics are generally easier to recycle as they typically originate from a single source and are of known composition.
[0030] In one embodiment, the acrylonitrile-butadiene-styrene is post-consumer recycled (PCR) acrylonitrile-butadiene-styrene, or PIR ABS. In another embodiment, the acrylonitrile-butadiene-styrene is virgin acrylonitrile-butadiene-styrene. It is preferred that the acrylonitrile-butadiene-styrene be PCR acrylonitrile-butadiene-styrene or PIR ABS as it enhances a cycle life thus rendering the PCR ABS or PIR acrylonitrile-butadiene-styrene recyclable more than once without adverse mechanical property degradation. The virgin ABS may be processed using the inventive method to enhance cycle life however it may critically affect certain mechanical properties such as an elongation at break.
[0031] The acrylonitrile-butadiene-styrene may be in the form of film, granules, flakes, powders, or pellets. The ABS may be a single-layered structure, or a multilayered structure such as the ones used in packaging. The single-layered structure, or the multilayered structure may be made of the same and/or different compositions of ABS and may include additives commonly used during ABS processing.
[0032] In embodiments where the acrylonitrile-butadiene-styrene is PCR ABS, or PIR ABS, the PCR ABS and/or PIR ABS are washed to remove any contaminants or residues and dried to remove moisture before processing. In one embodiment, the ABS is washed with an aqueous detergent solution. The washing is followed by drying in a vacuum oven at a temperature in a range of 50°C to 80°C for a time in a range of 5 to 12 hours before use to remove moisture. Once the ABS is washed and dried, it is cut into smaller pieces for the first extrusion.
[0033] The first extrusion 102 is performed in an extruder such as a single-screw extruder, or a twin-screw extruder. The processing parameters of the extruder may be varied to facilitate extrusion of the acrylonitrile-butadiene-styrene with maleic anhydride by optimizing one or more of melting of the acrylonitrile-butadiene-styrene, homogeneous mixing of the acrylonitrile-butadiene-styrene and the maleic anhydride, and efficient reaction between the acrylonitrile-butadiene-styrene and the maleic anhydride. Examples of such process parameters include, but are not limited to, type of extruder, geometrical design of the extruder, screw speed, residence time of material in the extruder, feed rate of the material into the extruder, temperature, and die geometry through which a product is extruded. In one embodiment, the extruder is a twin-screw extruder that facilitates enhanced mixing between the maleic anhydride and the acrylonitrile-butadiene-styrene when compared to a single-screw extruder. The first extrusion may be performed at a temperature corresponding to the melting temperature of the acrylonitrile-butadiene-styrene. In some embodiments, the melting temperature is in a range of 200 to 240°C. In some embodiments, the residence time is in a range of 1 to 10 minutes, preferably 1 to 5 minutes. In some embodiments, screw speed is in a range of 100 to 150 rotations per minute (rpm) in a twin-screw extruder. The first extrusion, in one embodiment, is performed in a twin-screw extruder at a temperature of 220°C, at screw speeds of 100-150 rotations per minute (rpm), and at a residence time of 10 minutes.
[0034] A concentration of maleic anhydride extruded with ABS, at step 102, is in a range of 1 weight percent (wt %) to 20 wt%. In some embodiments, the concentration of maleic anhydride extruded with ABS is in a range of 1 wt % to 6 wt %.
[0035] The first extrusion 102, in some embodiments, is performed in presence of a free radical initiator such as peroxides. Examples of free radical initiators include, but are not limited to, benzoyl peroxide, lauryl peroxide, dicumyl peroxide (DCP), or combinations thereof. In one embodiment, the free radical initiator is DCP. A concentration of the free radical initiator is in a range of 0.1 wt % to 1 wt %.
[0036] The first extrusion 102 produces a maleated acrylonitrile-butadiene-styrene (mABS) comprising a maleic anhydride grafted onto a butadiene unit of the acrylonitrile-butadiene-styrene. A grafting yield of the maleated acrylonitrile-butadiene-styrene provides an extent of grafting on the acrylonitrile-butadiene-styrene. The term “grafting yield”, as used herein, is defined as an amount of maleic anhydride grafted per 100 repeating units of butadiene and is expressed in percentage. In some embodiments, the grafting yield is in a range of 0.3% to 5%. In one embodiment, the grafting yield is in a range of 1% to 3%. In another embodiment, the grafting yield is in a range of 2% to 2.4%. The grafting yield may be obtained from an intensity of a characteristic infrared (IR) band of maleic anhydride moiety to an intensity of a characteristic band of the acrylonitrile-butadiene-styrene from IR spectrum of the maleated acrylonitrile-butadiene-styrene. In one embodiment, 1780 cm-1 band corresponding to carbonyl symmetric stretching of maleic anhydride is considered to determine the grafting yield. From the grafting yield, an estimate of maleic anhydride available for crosslinking with dynamic crosslinkers may be estimated.
[0037] At step 104, a second extrusion is performed of the maleated acrylonitrile-butadiene-styrene with a dynamic crosslinker to form an acrylonitrile-butadiene-styrene-vitrimer. The dynamic crosslinker forms covalent adaptive networks based on transesterification to form the acrylonitrile-butadiene-styrene-vitrimer on second extrusion.
[0038] The second extrusion like the first extrusion is performed in an extruder such as a single-screw extruder, or a twin-screw extruder. The processing parameters of the extruder, as discussed with reference to the first extrusion, may be varied to facilitate reactive extrusion of the maleated acrylonitrile-butadiene-styrene and the dynamic crosslinker. In one embodiment, the extruder is a twin-screw extruder that facilitates enhanced mixing between the maleated acrylonitrile-butadiene-styrene and the dynamic crosslinker when compared to a single-screw extruder. The second extrusion may be performed at a temperature corresponding to the melting temperature of the maleated acrylonitrile-butadiene-styrene. In some embodiments, the melting temperature is in a range of 200 to 240°C. In some embodiments, the residence time is in a range of 1 to 10 minutes, preferably 1 to 5 minutes. The second extrusion, in one embodiment, is performed in a twin-screw extruder at a temperature of 220°C, at screw speeds in a range of 100-150 rpm and at a residence time of 10 minutes.
[0039] The dynamic crosslinkers comprise 4,4’-methylenebis(N, N-diglycidylaniline) (MDGA), bisphenol A diglycidyl ether (BADGE), or combinations thereof.
[0040] The dynamic crosslinker 4,4’-methylenebis(N,N-diglycidylaniline) (MDGA) has the structure [I]. MDGA on second extrusion at step 104 forms ABS-MDGA vitrimer.

[I]
[0041] The dynamic crosslinker bisphenol A diglycidyl ether (BADGE) has the structure [II]. BADGE on second extrusion at step 104 forms ABS-BADGE vitrimer.

[II]

[0042] FIG. 2 provides a reaction scheme 200 for the formation of ABS-MDGA and ABS-BADGE vitrimer, respectively. In FIG. 2, “x”, “y” and “z” correspond to number of repeating units of acrylonitrile, butadiene and styrene, respectively.
[0043] On second extrusion, at step 104, maleic anhydride of the maleated ABS (mABS) undergoes ring-opening to form maleic-acrylonitrile-butadiene-styrene (maleic-ABS) having a maleic side chain. The dynamic crosslinkers MDGA and BADGE form reversible transesterification CAN through the maleic side chain to form ABS-MDGA vitrimer and ABS-BADGE vitrimer, respectively.
[0044] The second extrusion 104 is performed, in some embodiments, in presence of a catalyst. Examples of catalysts include, but are not limited to, triazobicyclodecene, triphenylphosphine, or zinc acetylacetonate. In one embodiment, the catalyst is zinc acetylacetonate (Zn(OAc)2). A concentration of the catalyst used in the second extrusion of step 104 is in a range of 0.1 wt % to 2 wt %. When the catalyst is Zn(OAc)2, it is believed that zinc ions of the catalyst promote ring opening of the maleic anhydride to form the maleic side chain on maleic-ABS, as shown in FIG. 2, and generate ester bonds which can undergo CAN at high temperature to form the vitrimers. CANs present in ABS-vitrimers make them easily reprocessable or recyclable through conventional polymer processing methods like extrusion and injection moulding.
[0045] In one embodiment, a concentration of the dynamic crosslinker extruded with the maleated acrylonitrile-butadiene-styrene is in a range of 1 to 30% by weight. In some embodiments, the concentration of the dynamic crosslinker extruded with the maleated acrylonitrile-butadiene-styrene (mABS) is in a range of 5 to 10% by weight. The concentration of the dynamic crosslinker may be decided based on the crosslinking desired and also on a desired property (for example mechanical property) of the resultant acrylonitrile-butadiene-styrene-vitrimer. For example, by varying the concentration of the dynamic crosslinker, choice of the dynamic crosslinker, or using combinations of dynamic crosslinker, mechanical properties of the acrylonitrile-butadiene-styrene-vitrimer such as tensile strength, and/or elongation at break may be varied.
[0046] The extruded acrylonitrile-butadiene-styrene-vitrimer after the second extrusion at step 104 may be immediately quenched in a water bath and pelletized. Such pellets can be used for subsequent molding, or shaping. The acrylonitrile-butadiene-styrene-vitrimers of the present disclosure may be shaped in the form of films, sheets, foams, particles, granules, beads, rods, plates, strips, stems, tubes, etc. via any process known to those skilled in the art. Example of such processes include extrusion, casting, compression molding, injection molding, and the like.
[0047] The inventive method of processing an acrylonitrile-butadiene-styrene has a recovery rate of greater than 90%. In another embodiment, the inventive method for acrylonitrile-butadiene-styrene processing has a recovery rate of greater than 94%. As used herein, the term “recovery rate” corresponds to a percentage of an amount of product recovered to an amount of reactants.
[0048] The inventive method of processing an acrylonitrile-butadiene-styrene provides the acrylonitrile-butadiene-styrene-vitrimers having a mechanical strength greater than a mechanical strength of acrylonitrile-butadiene-styrene. The ABS-vitrimers may be recycled along with virgin acrylonitrile-butadiene-styrene, in one embodiment. In another embodiment, the ABS-vitrimers may be recycled with PCR ABS or PIR ABS. As the acrylonitrile-butadiene-styrene-vitrimers formed according to the inventive method of the present disclosure exhibit superior mechanical strength after reprocessing or recycling, they may be used along with PCR or PIR acrylonitrile-butadiene-styrene. This contributes further to a closed-loop plastics economy minimizing dependence on virgin acrylonitrile-butadiene-styrene and minimizing plastic waste generation. The present disclosure thus provides a sustainable solution to address plastic waste and reduce the environmental impact of plastic waste and dependence on fossil fuels.
[0049] The acrylonitrile-butadiene-styrene-vitrimers may be reprocessed multiple times without degradation of their mechanical properties when compared to acrylonitrile-butadiene-styrene not containing the inventive acrylonitrile-butadiene-styrene-vitrimers. In one embodiment, the acrylonitrile-butadiene-styrene-vitrimer has a cycle life of more than 3 times. Hence, the ABS-vitrimers may be blended with virgin ABS, filled ABS, PCR ABS, PIR ABS or ABS copolymers during subsequent recycling steps. It is desirable that a melt flow index (MFI) of the reprocessed polymer is within permissible limits. Virgin ABS has MFI value in the range of 20 grams per 10 minutes (g/10 min) to 25 g/10 min. ABS vitrimer has MFI in the range of 10 g/10 min to 15 g/10 min. The term, “melt flow index”, as used herein, is defined as the mass of a thermoplastic polymer passing through a die of specified dimensions and properties at a specified temperature and under a known load within a time period of 10 minutes and can be measured using the International Organization for Standardization (ISO) 1133-1 or American Society for Testing and Materials (ASTM) D1238 test methods. Melt flow index (MFI) indicates flowability of the thermoplastic polymer.
[0050] It is an advantage of the present disclosure, irrespective of the additives present in PCR or PIR acrylonitrile-butadiene-styrene, the acrylonitrile-butadiene-styrene may be reprocessed using the disclosed method and the inventive crosslinkers to result in an upcycled acrylonitrile-butadiene-styrene.
[0051] The inventive acrylonitrile-butadiene-styrene (ABS)-vitrimer comprises a maleic-acrylonitrile-butadiene-styrene comprising a maleic sidechain on butadiene unit of acrylonitrile-butadiene-styrene. The dynamic crosslinker is linked to the maleic sidechain to form covalent adaptive networks to form the vitrimers. The dynamic crosslinker comprises 4,4’-methylenebis(N, N-diglycidylaniline) (MDGA), bisphenol A diglycidyl ether (BADGE), or combinations thereof.
[0052] In some embodiments, the acrylonitrile-butadiene-styrene (ABS)-vitrimer may further comprise additives such as carbon fibers, silica, glass fibers, UV additives, flame retardant additives, antimicrobial additives, lubricant additives, pigments, colors, and the like to enhance the mechanical properties and improve certain aspects of performance.
[0053] In some embodiments, an article is formed using the acrylonitrile-butadiene-styrene-vitrimers of the present disclosure. The articles may be formed by molding, blow molding, injection molding, filament winding, continuous molding, film-insert molding, infusion, pultrusion, RTM (resin transfer molding), RIM (reaction-injection molding), 3D printing, or any other method known to those skilled in the art. The article may further contain ABS, virgin ABS, PIR ABS, PCR ABS, filled ABS, ABS blends, ABS copolymers, and other additives.

EXAMPLES
EXAMPLE 1
Preparation of maleated acrylonitrile-butadiene-styrene
[0054] Commercially available ABS was subjected to cleaning. ABS was washed with an aqueous solution of detergent, followed by repeated washing in cold water. Afterward, the ABS was dried in a vacuum oven at 70°C overnight. Once dried, the ABS was chopped into small pieces, for further processing.
[0055] A DSM Explore Twin screw microcompounder (extruder) 15cc with co-rotating conical screw configuration was used for melt extrusion. The microcompounder has a recirculation channel that permits control over the residence time. The ABS was melt extruded with maleic anhydride in the presence of dicumyl peroxide, a radical initiator to form maleated acrylonitrile-butadiene-styrene (mABS), at a composition as shown in Table 1. The melt extrusion was performed at a temperature of 220 °C with a screw speed of 100 rpm, at a residence time of 10 minutes.
ABS (wt%) maleic anhydride (wt%) dicumyl peroxide (wt%)
94.9 5 0.1

Table 1
EXAMPLE 2
Preparation of acrylonitrile-butadiene-styrene-vitrimers (ABS-vitrimers)
[0056] ABS vitrimers were prepared by the melt extrusion of maleated ABS from Example 1 with dynamic crosslinkers in the presence of zinc acetylacetonate (Zn(acac)2), a catalyst. Two types of dynamic crosslinkers were utilized in this process, namely 4,4’-methylenebis(N, N-diglycidylaniline) (MDGA) and bisphenol A diglycidyl ether (BADGE) to form ABS-MDGA and ABS-BADGE vitrimers, respectively. The compositions for the second extrusion are shown in Table 2.

Vitrimer mABS (wt%) BADGE
(wt%) MDGA (wt%) Zn(acac)2 (wt%)
ABS-MDGA 88.2 - 10.8 1
ABS-BADGE 90.8 8.2 - 1

Table 2
Fourier Transform Infrared (FTIR) analyses
[0057] FIG. 3 is the FTIR spectra 300, where IR spectrum 302 corresponds to FTIR spectrum of ABS and 304 corresponds to FTIR spectrum of mABS. The appearance of a new IR band at 1780 cm-1 in spectrum 304, which was absent in spectrum 302, confirmed the formation of maleated ABS. The 1780 cm-1 IR band corresponds to the carbonyl stretching band for cyclic anhydrides which occurs due to the grafting of maleic anhydride onto ABS.
[0058] FIG. 4 presents FTIR spectra 400. In FIG. 4, IR spectrum 402 corresponds to FTIR spectrum of mABS, IR spectrum 404 corresponds to FTIR spectrum of ABS-MDGA and IR spectrum 406 corresponds to FTIR spectrum of ABS-BADGE, respectively. On reaction between the dynamic crosslinkers and the maleated ABS, ß-hydroxy esters are formed which can undergo dynamic transesterification network exchange at elevated temperatures. The appearance of a new IR band at 3400 cm-1 corresponds to -OH stretching of the ß-hydroxy esters. The presence of 3400 cm-1 IR band in 404 and 406 confirmed the crosslinking reaction between epoxy and maleic side chain, on vitrimer formation. There was a corresponding decrease in the intensity of the cyclic anhydride band at 1780 cm-1 from spectrum 402 to 404 and 406 due to the consumption of the cyclic anhydrides on crosslinking with the dynamic crosslinkers. A corresponding increase in the ester band intensity at 1740 cm-1 further confirmed ABS vitrimer formation from IR spectra 404 and 406.
Mechanical testing
[0059] According to ASTM D638 (type V) stress-strain properties of the samples given in Table 2 along with ABS using Universal Testing Machine at room temperature. The testing parameters were load cell: 5 kN, preload force: 0.1 N, cross head speed: 50mm/minute, gauge length: 15mm, number of Samples: 5 per batch for consistency, sample dimension: 50 mm length x 3.6 mm width x 3.3 mm thickness. The samples were placed between clamps of the Universal Testing Machine - Tensile Testing Module such that the edges of the samples were parallel to the direction of the load. The grips were then tightened to hold the sample securely within the jig. The test sample was then pulled apart at a tensile speed of 50 mm/min until it broke. Table 3 provides the mechanical testing data of the samples.

Samples
Tensile Strength (MPa)
Elongation at break (%)
ABS 48 ± 0.8 31 ± 4.8
ABS-MDGA 69 ± 1 23 ± 0.6
ABS-BADGE 64± 1 24 ± 3.8

Table 3
[0060] From Table 3, it is observed that both the vitrimers show a higher tensile strength than ABS. ABS-MDGA displayed a tensile strength of 69 megaPascal (MPa) which was a 44% increase compared to ABS. ABS-BADGE displayed a tensile strength of 64 MPa which was a 33% increase compared to ABS. The elongation at break of both the vitrimers, ABS-MDGA and ABS-BADGE was lesser than that of ABS which was expected on crosslinking due to the vitrimer formation.

Recyclability test
[0061] Recyclability tests up to 3 cycles for ABS and ABS-vitrimers were performed by processing them through the extruder. The extruded samples after recycling were mechanically tested. Table 4 provides the recyclability test results of ABS and ABS vitrimers, where R1 and R3 represent recycling cycle numbers 1, and 3, respectively.
Sample Tensile Strength (MPa) Elongation at break (%)
R1 R3 Percentage Retention R1 R3 Percentage Retention
ABS 48 ± 0.8 45± 0.6 93.75% 31 ± 4.8 13± 2.8 42%
ABS-MDGA 69 ± 1 70 ± 3.7 100% 23 ± 0.6 11± 1.8 48%
ABS-BADGE 64± 1 65 ± 2 100% 24 ± 3.8 10± 0.5 42%
Table 4

[0062] ABS vitrimers retained 100% of the tensile strengths even after three cycles of processing, as seen in Table 4, whereas ABS showed a slight decrease in its tensile strength after reprocessing. It was observed that ABS-MDGA and ABS-BADGE retained 48% and 42% of their initial elongation at break, respectively. ABS retained 42% of its initial elongation at break. The recyclability tests revealed mechanical property retention which can be attributed to dynamic covalent adaptable network (CAN) of the ABS-vitrimers which rearrange at elevated temperatures. This confirmed that the ABS-vitrimers of the present disclosure may be reprocessed more than 3 times without any degradation in mechanical properties.
[0063] It is to be understood that the above description is intended to be illustrative, and not restrictive. Furthermore, many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. Although the present disclosure has been described with reference to specific exemplary embodiments, it will be recognized that the disclosure is not limited to the embodiments described, but can be practiced with modification and alteration within the scope of the appended claims.

, Claims:CLAIMS

We Claim:
1. An acrylonitrile-butadiene-styrene (ABS)-vitrimer comprising:
a maleic-acrylonitrile-butadiene-styrene comprising a maleic sidechain on butadiene unit of an acrylonitrile-butadiene-styrene (ABS); and
a dynamic crosslinker linked to the maleic sidechain and forms covalent adaptive networks to form the acrylonitrile-butadiene-styrene-vitrimer, wherein the dynamic crosslinker comprises 4,4’-methylenebis(N, N-diglycidylaniline) (MDGA), bisphenol A diglycidyl ether (BADGE), or combinations thereof.
2. The acrylonitrile-butadiene-styrene (ABS)-vitrimer as claimed in claim 1, wherein a grafting yield of the maleic-acrylonitrile-butadiene-styrene is in a range of 0.3% to 5%.
3. The acrylonitrile-butadiene-styrene (ABS)-vitrimer as claimed in claim 1, wherein a concentration of the dynamic crosslinker in the acrylonitrile-butadiene-styrene (ABS)-vitrimer is in a range of 1 to 30% by weight.
4. The acrylonitrile-butadiene-styrene (ABS)-vitrimer as claimed in claim 1, wherein a tensile strength of the acrylonitrile-butadiene-styrene (ABS)-vitrimer is greater than a tensile strength of the acrylonitrile-butadiene-styrene (ABS).
5. The acrylonitrile-butadiene-styrene (ABS)-vitrimer as claimed in claim 1, wherein the acrylonitrile-butadiene-styrene (ABS) comprises a virgin acrylonitrile-butadiene-styrene (ABS), a post-consumer recycled (PCR) ABS, post-industrial recycled (PIR) ABS, or combinations thereof.
6. A method of processing an acrylonitrile-butadiene-styrene (ABS) comprising:
performing a first extrusion (102) of the acrylonitrile-butadiene-styrene with maleic anhydride at a temperature in a range of 200 to 240 °C to form a maleated acrylonitrile-butadiene-styrene; and
performing a second extrusion (104) of the maleated acrylonitrile-butadiene-styrene with a dynamic crosslinker at a temperature in a range of 200 to 240 °C to form an acrylonitrile-butadiene-styrene-vitrimer having a tensile strength greater than a tensile strength of the acrylonitrile-butadiene-styrene (ABS), and wherein the dynamic crosslinker comprises 4,4’-methylenebis(N, N-diglycidylaniline) (MDGA), bisphenol A diglycidyl ether (BADGE), or combinations thereof.
7. The method as claimed in claim 6, wherein the method of processing the acrylonitrile-butadiene-styrene (ABS) comprises processing a virgin acrylonitrile-butadiene-styrene (ABS), a post-consumer recycled (PCR) ABS, post-industrial recycled (PIR) ABS, or combinations thereof.
8. The method as claimed in claim 6, wherein a grafting yield of the maleated acrylonitrile-butadiene-styrene is in a range of 0.3% to 5%.
9. The method as claimed in claim 6, wherein a concentration of the dynamic crosslinker in the acrylonitrile-butadiene-styrene-vitrimer is in a range of 1 to 30% by weight.
10. The method as claimed in claim 6, wherein the acrylonitrile-butadiene-styrene-vitrimer has a cycle life of more than 3 times.
11. The method as claimed in claim 6, wherein the first extrusion (102) is performed in presence of a free radical initiator, wherein the free radical initiator comprises benzoyl peroxide, lauryl peroxide, dicumyl peroxide, or combinations thereof.
12. The method as claimed in claim 6, wherein the second extrusion (104) is performed in presence of a catalyst, wherein the catalyst comprises triazobicyclodecene, triphenylphosphine, zinc acetylacetonate, or combinations thereof.
13. The method as claimed in claim 6, wherein the first extrusion (102), the second extrusion (104), or both are performed in a twin-screw extruder at a screw speed of 100 to 150 rotations per minute (rpm) and at a residence time in a range of 1 to 10 minutes.
14. An article formed using the acrylonitrile-butadiene-styrene-vitrimer as claimed in any of the claims 1-6.