Description:TECHNICAL FIELD
The present disclosure relates to a field of polymer recycling and sustainable materials. Moreover, the present disclosure relates to a method for recycling post-consumer recycled (PCR) acrylonitrile butadiene styrene (ABS) into a vitrimer with enhanced mechanical strength and a PCR ABS vitrimer composition.
BACKGROUND
In the current era of globalization, plastics have become an indispensable part of our daily lives, with wide-ranging applications in various industries. However, the increased use of synthetic plastics and the limited options for their efficient end-of-life management have resulted in critical issues, including plastic pollution and significant carbon emissions. The non-biodegradable nature of synthetic plastics contributes to their persistence in the environment and poses environmental and health risks. Plastic production has reached staggering levels, with global estimates exceeding 400 megatons per year. Incineration of plastic waste is a significant contributor to net carbon emissions, projected to reach 16% by 2050. The magnitude of these challenges necessitates integrative interventions to increase plastics recycling rates and reduce production demand growth, offering an alternative solution to mitigate carbon dioxide emissions.
While the adoption of bioplastics as a substitute for petroleum-based plastics has been considered, it does not fully address the plastic waste issue. Commercial biodegradable bioplastics, such as polylactic acid (PLA) and polyhydroxyalkanoates (PHAs), exhibit slow degradation under ambient conditions, even in the presence of microorganisms. The biodegradation of plastics in the environment or landfills can lead to uncontrolled methane emissions and further environmental consequences. Additionally, bioplastics may not possess the desired mechanical strength comparable to petrochemical-based plastics. Thus, there exists a technical problem of recycling of the polymeric waste materials, such as thermoplastics with high thermomechanical toughness and rigidity, into valuable products.
Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks associated with the conventional recycling method of the polymeric waste materials.
SUMMARY
The present disclosure provides a method for recycling post-consumer recycled (PCR) acrylonitrile butadiene styrene (ABS). The present disclosure provides a solution to the technical problem of recycling a polymeric waste material, such as the PCR ABS which is a thermoplastic with high thermomechanical toughness and rigidity in a cost-effective manner and sustainable manner. An aim of the present disclosure is to provide a solution that overcomes at least partially the problems encountered in the prior art and provide an improved method that not only recycles but also upcycles the PCR ABS in terms of its mechanical strength, for example, in each recycling operation in a cost-effective manner. Thus, the method of the present disclosure manifests a technical advancement as well as economic benefits. Additionally, the present disclosure provides an improved PCR ABS vitrimer composition.
One or more objectives of the present disclosure is achieved by the solutions provided in the enclosed independent claims. Advantageous implementations of the present disclosure are further defined in the dependent claims.
In one aspect, the present disclosure provides a method of recycling post-consumer recycled (PCR) acrylonitrile butadiene styrene (ABS). The method includes converting the PCR ABS having a first mechanical strength into oxazoline-modified PCR ABS. The method further includes performing melt mixing of the oxazoline-modified PCR ABS with an imine-containing oil. The method further includes performing melt extrusion of a mixture of the oxazoline-modified PCR ABS and the imine-containing oil to synthesize a PCR ABS vitrimer having a second mechanical strength greater than the first mechanical strength in a first recycling operation.
The method of the present disclosure for recycling and upcycling PCR-ABS using oxazoline modification and vitrimer formation has several significant technical effects.
Beneficially, in a first example, the method enhances the mechanical strength of the PCR ABS vitrimer produced by the method in the first recycling operation. The resulting PCR-ABS vitrimers exhibit the second mechanical strength that is greater than the original PCR-ABS material. This increase in mechanical strength is observed through the analysis of stress-strain properties, including tensile strength and yield strength. The PCR ABS vitrimers demonstrate improved performance and resilience compared to the original PCR-ABS using for recycling, making them suitable for various applications. The mechanical strength of the PCR ABS vitrimers may be further improved in each recycling operation starting from the first recycling operation up to a defined number of recycling operations, for example, about 5-10 recycling operations. Thus, each recycling may be referred to as an upcycling operation as mechanical strength is improved in each recycling operation.
In a second example, advantageously, the upcycling in mechanical strength properties can be attributed to the formation of dynamic covalent bonds through imine exchange reaction within vitrimers of oxazoline-modified PCR ABS. In other words, the synthesized PCR ABS vitrimer includes dynamic covalent adaptable network (CAN) that allows the synthesized material to be melted, reprocessed, and reshaped without loss in mechanical properties. This reprocessing ability overcomes the challenge of recycling waste generated from three-dimensional (3D) printed ABS objects, enabling their transformation into stronger, tougher, and solvent-resistant 3D structures.
Advantageously, when the melt extrusion of the mixture of the oxazoline-modified PCR ABS and the imine-containing oil is performed, reversible crosslinking of polymer chains are formed through covalent adaptable networks in the synthesized PCR ABS vitrimer. This reversible crosslinking of polymer chains through covalent adaptable networks allows the synthesized material (i.e., the synthesized PCR ABS vitrimer) to be reprocessed multiple times without degradation of its mechanical properties, which is not possible with traditional thermoplastics. During melt mixing, at first the PCR-ABS is functionalized to PCR-ABS oxazoline (PCR-ABS Ox) using ethanolamine. At the second step –COOH of imine containing oil (e.g., bio-based non-edible oil) attacks the oxazoline ring and opens up to form amide and esters within the system. Thus, a crosslinked -network is formed where imine (-C=N-) can act as the covalent adaptable network. As a result, the synthesized PCR ABS vitrimer is developed as high-performance material with superior mechanical properties and upcycling capabilities as compared to conventional methods.
In a third fourth example, by utilizing the upcycling process, the method contributes to the establishment of a closed-loop circular plastics economy. The ability to transform waste 3D printing materials (i.e., the PCR ABS) into high-performing vitrimers with improved properties reduces the reliance on virgin plastics and minimizes plastic waste generation. The method of the present disclosure is thus a sustainable approach and has potential to significantly reduce the environmental impact of plastic disposal.
In a fifth example, the method of the present disclosure enables achieving resource efficiency in the synthesis of the PCR ABS vitrimer as the imine-containing oil is used in the synthesis process. Further, the imine-containing oil is derived from a non-edible, bio-based oil. These oils offer advantages such as renewability, cost-advantage due to abundance, and low environmental impact.
In another aspect, the present disclosure provides a post-consumer recycled (PCR) acrylonitrile butadiene styrene (ABS) vitrimer composition. The PCR ABS vitrimer composition includes 98.5 to 99.9 percent by weight of oxazoline-modified PCR ABS. The PCR ABS vitrimer composition further includes 0.1 to 1.5 percent by weight of an imine-containing oil.
The PCR ABS vitrimer composition of the present disclosure has same technical effects as described above for the method. For example, the PCR ABS vitrimer composition exhibits higher mechanical performance compared to conventional PCR ABS, expanding its range of applications. The oxazoline modification of PCR ABS in the composition enhances its mechanical properties, resulting in improved strength, toughness, and resilience.
It is to be appreciated that all the aforementioned implementation forms can be combined. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative implementations construed in conjunction with the appended claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a flowchart depicting a method of recycling post-consumer recycled (PCR) acrylonitrile butadiene styrene (ABS), in accordance with an embodiment of the present disclosure;
FIG. 2 is a flowchart for conversion of the PCR ABS into the oxazoline-modified PCR ABS, in accordance with an embodiment of the present disclosure;
FIGs. 3A and 3B collectively depict a flowchart for preparation of a PCR ABS vitrimer, in accordance with an embodiment of the present disclosure;
FIGs. 4A and 4B collectively depict a flowchart for preparing the imine containing oil, in accordance with an embodiment of the present disclosure;
FIG. 5A is a graph depicting Fourier Transform Infrared (FTIR) spectrum of oxazoline-modified PCR ABS, in accordance with an embodiment of the present disclosure; and
FIG. 5B is a graph depicting Fourier Transform Infrared (FTIR) spectrum of PCRABS vitrimer, in accordance with an embodiment of the present disclosure.
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those skilled in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION OF EMBODIMENTS
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
FIG. 1 is a flowchart depicting a method of recycling post-consumer recycled (PCR) acrylonitrile butadiene styrene (ABS), in accordance with an embodiment of the present disclosure. With reference to FIG. 1, there is shown a flowchart of a method 100. In some implementations, the method 100 is executed by a skilled person. The method 100 may include steps 102 to 106.
There is provided the method 100 of recycling the PCR ABS, the PCR ABS is a plastic that is produced by recycling and reprocessing waste ABS materials that have been used by consumers. ABS is a common thermoplastic known for its excellent mechanical properties, impact resistance, and heat resistance, which make the ABS suitable for various applications such as automotive parts, electronic housings, and consumer products. The process of post-consumer recycling involves collecting used ABS products, such as discarded plastic items, and processing them to remove impurities and contaminants. The resulting recycled ABS material is then transformed into the PCR ABS through various techniques, including melting and extrusion. The PCR ABS offers several environmental benefits compared to virgin ABS, as it reduces the demand for new plastic production and minimizes the amount of waste sent to landfills. By recycling and upcycling ABS materials, the PCR ABS contributes to a more sustainable and circular economy by extending the lifespan of the plastic and reducing the overall environmental impact associated with plastic waste.
In some examples, the ABS is used as a printing material for 3D printing or additive manufacturing. To obtain the PCR ABS from waste 3D printing materials, the cleaning and cutting process is employed. Firstly, the waste materials are washed using an aqueous solution of detergent to remove any contaminants or residues. Once the washing process is complete, the PCR ABS is dried to remove any moisture. This is achieved by placing the washed materials in a vacuum oven and subjecting them to a temperature of 70°C for a duration of six to twelve hours (e.g., overnight). The vacuum environment helps in efficient drying by reducing the boiling point of water. After the drying process, the PCR ABS is prepared for further use by cutting it into small pieces. This chopping step facilitates easier handling and processing of the material in subsequent manufacturing or recycling processes. The cleaning and cutting process ensures that the PCR ABS obtained from waste 3D printing materials is free from impurities and moisture, making it suitable for recycling.
In some other examples, the PCR ABS is used in automotive parts, electrical and electronic enclosures, toys, pipes and fittings. In such examples, the same cleaning and cutting process may be employed prior to the execution of the steps of the method 100.
At step 102, the method 100 includes converting the PCR ABS having a first mechanical strength into oxazoline-modified PCR ABS. The first mechanical strength refers to the original strength of the PCR ABS before it undergoes the conversion process to become the oxazoline-modified PCR ABS. It represents the strength characteristics of the PCR ABS material in its untreated state, prior to any modifications or enhancements. In some examples, the first mechanical strength represents the mechanical properties that may include, but are not limited to, Young’s modulus, percentage recovery in the Young’s modulus, yield strength (MPa), percentage recovery in yield strength, percentage elongation at break, and percentage recovery in elongation at break. The term "oxazoline-modified PCR ABS" refers to the PCR ABS material that has undergone a modification process where oxazoline groups have been introduced into its molecular structure. This modification involves incorporating oxazoline molecules or functional groups into the PCR ABS, which may lead to improved properties or characteristics of the PCR ABS material, such as enhanced reprocessability, recyclability, or other desired performance attributes. The addition of oxazoline groups alters the chemical composition and structure of the PCR ABS, providing it with new capabilities or functionalities.
In an implementation, the converting of the PCR ABS into the oxazoline-modified PCR ABS includes feeding a mixture of mono-ethanol amine, zinc acetate, and the PCR ABS into a melt mixer. In some implementation, the converting of the PCR ABS into the oxazoline-modified PCR ABS further includes homogenizing the mixture for 5 to 20 minutes at a temperature ranging from 200 to 230 degrees Celsius (°C) with a uniform screw speed ranging from 60 to 100 rotations per minute (RPM). The melt mixer refers to a processing equipment or device utilized for mixing and melting the materials involved, such as the PCR ABS and other components, at elevated temperatures. The melt mixer is designed to achieve thorough blending and homogenization of the materials, ensuring that they are uniformly mixed and melted together. The melt mixer may employ various mechanisms, such as rotating blades or screws, to promote efficient mixing and melting of the materials. This process facilitates the formation of a homogeneous melt or mixture that is further processed or utilized in subsequent steps of the method 100.
In an example, in order to convert the PCR ABS into the oxazoline-modified PCR ABS, 6% by weight of ethanol amine, 0.05% by weight of zinc acetate, and waste ABS materials is introduced into the melt mixer and allowed to homogenize for 5 minutes at 150 °C with a screw speed of 60 RPM. When the screw speed is reaches a uniform speed, then the temperature is increased to 220 °C and mixed for 20 min with an integrated recirculation channel under a continuous nitrogen flow. Further, extrusive ABS strips are then injection molded simultaneously to get ASTM standard samples for investigation of mechanical properties.
At step 104, the method 100 further includes performing melt mixing of the oxazoline-modified PCR ABS with an imine-containing oil. In an implementation, the imine-containing oil is pre-synthesized before melt mixing with the oxazoline-modified PCR ABS. In an implementation, the imine-containing oil is a non-edible bio-based oil. This ensures that the imine-containing oils used in the step 104 of the method 100 of recycling PCR ABS do not compete with the food supply chain, minimizing any potential impact on food security. In some examples, the imine-containing oil may be derived from at least one of castor oil, rubber seed oil, jatropha oil, pongamia oil, and tung oil. Such bio-based oils are non-edible and available in the environment in abundance. Further, non-edible bio-based oils, when sourced and processed responsibly, may have a lower environmental impact compared to petroleum-based oils and may be obtained at a relatively low cost. In some other examples, the imine-containing oil is an edible bio-based oil. In some other examples, the imine-containing oil may include a petroleum-based oil.
The melt mixing refers to the process of blending and homogenizing materials in a molten or melted state. The melt mixing involves combining different components, such as polymers, additives, fillers, or other ingredients, and subjecting them to heat to melt and become viscous. Mechanical shear forces, such as those generated by rotating blades or screws, are applied to promote thorough mixing and dispersion of the components. The melt mixing may achieve a uniform distribution of the materials and ensure that the materials are well-mixed and incorporated into a homogenous mixture. In some examples, the melt mixing is performed using a specific machine, for example, single-screw or twin-screw extruders, kneaders, or internal mixers. Such specific machine consists of a mixing chamber or vessel where the polymer material, along with any additives or modifiers, is heated and melted. In an implementation, the melt mixing allows for the homogeneous distribution of the oxazoline-modified PCR ABS and the imine-containing oil, ensuring the desired properties and performance of the final material. Specifically, during the melt mixing, -COOH group of the imine-containing oil attacks and opens up the oxazoline ring, forming amide and ester bonds within the overall composition. In other words, the PCR ABS and other components, including the imine-containing bio-based oil, are subjected to elevated temperatures and mechanical shear forces. Such conditions promote chemical reactions and molecular interactions, allowing the -COOH group to react with the oxazoline ring, leading to the formation of amide and ester bonds. Please note that the melt mixing facilitates the dispersion and reaction of the components, ensuring that the desired chemical transformations take place within the material.
In an implementation, the melt mixing of the oxazoline-modified PCR ABS and the imine-containing oil is performed for a time period ranging from 3 to 10 minutes. Further, in such implementation, the melt mixing of the oxazoline-modified PCR ABS and the imine-containing oil is performed at a temperature ranging from 200 to 240 degrees Celsius with a uniform screw speed ranging from 60 to 100 rotations per minute (RPM). In some examples, the melt mixing of the oxazoline-modified PCR ABS and the imine-containing oil is performed at a temperature of 210 °C to 240 °C with a screw speed of 60 RPM for 10 minutes. It should be noted that the parameters during melt mixing, such as temperature, screw speed, and time period of the melt mixing, may vary depending on the specific application requirements. The parameters may be adjusted to optimize the mixing process and achieve the desired properties and characteristics of the resulting material.
At step 106, the method 100 further includes performing melt extrusion of a mixture of the oxazoline-modified PCR ABS and the imine-containing oil to synthesize a PCR ABS vitrimer having a second mechanical strength greater than the first mechanical strength in a first recycling operation. During the melt extrusion process, the mixture is heated at a temperature of 200 °C to 240 °C and subjected to mechanical shearing forces as the mixture passes through an extruder. The elevated temperature and shear forces facilitate the reactions and interactions between the oxazoline-modified PCR ABS and the imine-containing oil. in an implementation, the PCR ABS vitrimer includes 98.5 to 99.9 percent by weight of the oxazoline-modified PCR ABS and 0.1 to 1.5 percent by weight of the imine-containing oil. In some examples, the PCR ABS vitrimer includes 99.75 percent by weight of the oxazoline-modified PCR ABS and 0.25 percent by weight of the imine-containing oil. In some other examples, the PCR ABS vitrimer includes 99.50 percent by weight of the oxazoline-modified PCR ABS and 0.50 percent by weight of the imine-containing oil.
In some implementations, the PCR ABS vitrimer, synthesized by the melt extrusion of the mixture of the oxazoline-modified PCR ABS and the imine-containing oil, includes a dynamic Covalent Adaptable Network (CAN) to impart re-processability to the PCR ABS vitrimer. The dynamic CAN is formed through an imine exchange reaction within the PCR ABS vitrimer using an imine functional group of the imine-containing oil. Such reactions result in the formation of covalent bonds, such as amide and ester bonds, within the material. In other words, the vitrimer formation within the PCR ABS occurs as a result of the dynamic covalent adaptable network (CAN) created by the reaction between the oxazoline groups and the imine-containing oil. The CAN imparts enhanced stability, reprocessability, and improved mechanical properties to the PCR ABS vitrimer. As a result, the PCR ABS vitrimer obtained after the melt extrusion process exhibits the second mechanical strength that is greater than the initial or "first mechanical strength" of the PCR ABS prior to modification. The increase in mechanical strength is a desirable outcome as it enhances the overall performance and durability of the PCR ABS material. Further, allowing the recycling and upcycling of PCR ABS waste into stronger, tougher, and more resilient 3D objects or products, contributing to the closed-loop circular plastics economy.
In an implementation, in each recycling operation starting from the first recycling operation up to a defined number of recycling operations, a mechanical strength of the PCR ABS vitrimer synthesized by the melt extrusion of the mixture of the oxazoline-modified PCR ABS and the imine-containing oil is incrementally increased. Each recycling operation is an upcycling due to the increase in the mechanical strength. For instance, let's consider a scenario where the initial PCR ABS vitrimer obtained after the first recycling operation has the first mechanical strength. In the subsequent recycling operation, the PCR ABS vitrimer from the previous step is further processed through the melt extrusion, resulting in a vitrimer with an increased mechanical strength. This increment in mechanical strength signifies the upcycling nature of the process. Further, the sequence continues with subsequent recycling operations. Each iteration of the melt extrusion process leads to the synthesis of a PCR ABS vitrimer with incrementally improved mechanical strength. Such iterative upcycling approach enables the transformation of the PCR ABS waste material into a series of vitrimers that exhibit increasingly enhanced mechanical properties, contributing to the closed-loop circular plastics economy.
Further, other advantages of the method of recycling of the PCR ABS may include sustainable recycling. Specifically, the composition utilizes PCR ABS, which is obtained from post-consumer waste, thereby promoting the recycling and reuse of plastic materials. By incorporating PCR ABS, the composition contributes to a more sustainable and environmentally friendly approach to plastic waste management.
FIG. 2 is a flowchart for conversion of the PCR ABS into the oxazoline-modified PCR ABS, in accordance with an embodiment of the present disclosure. With reference to FIG. 2, there is shown a flowchart 200 that includes a series of operations from 202-to-204. In some examples, the flowchart 200 may be executed in a twin-screw micro-compounder.
At operation 202, the PCR ABS is fed in the melt mixer. The chemical structure of the PCR ABS is shown in a block of the operation 202. Prior to receiving, the PCR ABS is cleaned and cut into smaller pieces. Further, 6% by weight of ethanol amine and 0.05% by weight of zinc acetate are also added in the melt mixer along with the PCR ABS. After that, at operation 204, the melt mixing is performed at a temperature of about 220 °C with a screw speed of 60 RPM for 5 minutes. As a result, oxazoline-modified PCR ABS 206 is prepared, and ammonia gas is released. The chemical structure of the oxazoline-modified PCR ABS 206 is shown in a block of the operation 204.
FIGs. 3A and 3B collectively depict a flowchart for preparing the PCR ABS vitrimer, in accordance with an embodiment of the present disclosure. FIG. 3 is described in conjunction with elements from FIG. 2. With reference to FIGs. 3A and 3B, there is shown a flowchart 300 that includes a series of operations from 302-to-304. The flowchart 300 may be executed in a twin-screw micro-compounder.
At operation 302, the oxazoline-modified PCR ABS 206 is melt mixed with an imine-containing oil 306. The chemical structures of the oxazoline-modified PCR ABS 206 and the imine containing oil 306 are shown in a block of the operation 302. The imine containing oil 306 used in the operation 302 is pre-synthesized by using castor oil. However, in some other examples, the imine containing oil 306 may be pre-synthesized by using any edible, non-edible, bio based, non bio-based oils. While melt mixing, COOH group of the imine-containing oil 306 attacks and opens up the oxazoline ring, forming amide and ester bonds within the overall composition. Further, the melt mixing is performed at the temperature of 210 °C to 240 °C with the screw speed of 60 RPM for 10 minutes. After that, at operation 304, the mixture of the oxazoline-modified PCR ABS 206 and the imine-containing oil 306 is melt extruded to synthesize a PCR ABS vitrimer 308. The melt extrusion of the mixture is performed in the extruder, subjecting it to elevated temperatures and mechanical shear forces. The chemical structure of the PCR ABS vitrimer 308 is shown in a block of the operation 304. In an implementation, a PCR ABS vitrimer composition (i.e., the composition of the PCR ABS vitrimer 308) includes 98.5 to 99.9 percent by weight of the oxazoline-modified PCR ABS 206, and 0.1 to 1.5 percent by weight of the imine-containing oil 306.
PCR ABS-based plastics are converted to the oxazoline-modified PCR ABS 206 followed by mixing with the imine-containing oils (for example: the imine containing oil 306) to form the synthesized PCR ABS vitrimers (for example: the PCR ABS vitrimer 308) through the melt extrusion. This is industrially feasible based on the dynamic covalent adaptive networks of the imine exchange reaction, featuring malleability and rapid stress relaxation. This may be the first approach to the fabrication of waste PCR ABS vitrimer networks with dynamic crosslinking that exhibit excellent solvent resistance at elevated temperatures due to the presence of preserved interlayer covalent bonds restricting disintegration. Further, the dynamic crosslinks with the capacity of exchangeable bond formation via the imine exchange may impart multi functionalities such as malleability, recyclability, weldability, and reconfigurability of the PCR ABS Vitrimers 308. The existing challenges of recycling waste plastics is minimized by upscaling the process in an industrially viable manner to reduce the carbon footprint significantly and help in achieving a closed-loop circular economy.
FIGs. 4A and 4B collectively depict a flowchart for preparing the imine containing oil, in accordance with an embodiment of the present disclosure. With reference to FIGs. 4A and 4B, there is shown a flowchart 400 that includes a series of operations from 402-to-408.
At operation 402, a non-edible bio-based oil is taken as the starting material. This step involves selecting the non-edible bio-based oil, which refers to an oil derived from plant sources that is not typically used for human consumption. The specific type of non-edible bio-based oil may vary depending on the application and availability. The chemical structure of the non-edible bio-based oil, for example the castor oil, is shown in a block of the operation 402. At operation 404, the imine-containing oil 306 is pre-synthesized by preparing a maleated oil by reacting the bio-based oil with maleic anhydride and a peroxide initiator under pre-defined conditions, resulting in a maleated oil product. The chemical structure of the maleated oil product is shown in a block of the operation 404. After that, at operation 406, the imine-containing oil 306 is pre-synthesized further by causing amination of the maleated oil by reacting the maleated oil product with an amine compound in the presence of an initiator and a solvent, followed by purification to obtain an aminated oil product. The chemical structure of the aminated oil product is shown in a block of the operation 406. Further, at operation 408, the imine-containing oil 306 is pre-synthesized further by reacting the aminated oil product with an aldehyde compound in the presence of a solvent, followed by removal of excess solvent to obtain the imine-containing oil 306. The chemical structure of the imine-containing oil 306 synthesized from the castor oil is shown in a block of the operation 408.
FIG. 5A is a graph depicting Fourier Transform Infrared (FTIR) spectrum of oxazoline-modified PCR ABS, in accordance with an embodiment of the present disclosure. With reference to FIG. 5A, there is shown a graph 500A depicting an exemplary FTIR spectra of a sample strip of the oxazoline-modified PCR ABS prepared using the method 100 (shown in FIG. 1). Specifically, the graph 500A depicts the absorption of infrared light by the sample strip of the oxazoline-modified PCR ABS at different wavelengths, typically measured in wavenumbers. Wavenumber is expressed in reciprocal centimetre (cm-1) in an abscissa axis. Transmittance is expressed in arbitrary units in an ordinate axis.
The graph 500A includes a curve 502A depicting the FTIR spectrum that indicate the absorption of infrared light. Each peak or band in the curve 502A corresponds to the vibration of specific chemical bonds within the sample strip of the oxazoline-modified PCR ABS. The curve 502A includes a section 504A. The section 504A is represented in an enlarged view, displays a distinctive feature known as a shoulder peak 506A. The shoulder peak 506A is at 1664 cm-1 which attributes to the oxazoline groups, confirming the successful conversion of the PCR- ABS to the oxazoline-modified PCR ABS.
FIG. 5B is a graph depicting Fourier Transform Infrared (FTIR) spectrum of PCRABS vitrimer, in accordance with an embodiment of the present disclosure. With reference to FIG. 5B, there is shown a graph 500B depicting an exemplary FTIR spectra of a sample strip of the PCR ABS vitrimer prepared using the method 100 (shown in FIG. 1). Specifically, the graph 500B depicts the absorption of infrared light by the sample strip of the PCR ABS vitrimer at different wavelengths, typically measured in wavenumbers. Wavenumber is expressed in reciprocal centimetre (cm-1) in an abscissa axis. Transmittance is expressed in arbitrary units in an ordinate axis.
The graph 500B includes a curve 502B depicting the FTIR spectrum that indicate the absorption of infrared light. Each peak or band in the curve 502B corresponds to the vibration of specific chemical bonds within the sample strip of the PCR ABS vitrimer. The curve 502B includes a section 504B. The section 504B is represented in an enlarged view, displays a distinctive feature known as a shoulder peak 506B. The shoulder peak 506B is at 1664 cm-1 which attributes to the imine groups, confirming the successful synthesis of the PCR- ABS vitrimer.
Example 1
Let's consider an example illustrating the synthesis of imine-containing bio-based oil through a series of steps:
Step 1: Synthesis of Maleated Bio-based Oil: To begin, 75 g of non-edible bio-based oil, such as castor oil, and 23.52 g of maleic anhydride were combined in a 250 ml one-necked round-bottom flask. To initiate the reaction, 0.324 g of dicumyl peroxide was added to the mixture. The resulting mixture was continuously stirred at 120 °C for 5 hours. After completion, the final product was cooled and used without further purification. This step yielded a product with a 97% yield.
Step 2: Amination of Maleated Bio-based Oil: In the second step, 5 g of the maleated bio oil obtained from Step 1 and 0.6 g of AIBN were dissolved in 25 mL of THF (tetrahydrofuran). To this solution, 4.45 g of cysteamine was added, and the mixture was stirred at 85 °C for 24 hours. Following the reaction, the product was washed with distilled water and dried at 80 °C overnight. This step resulted in a product with a yield of 95%.
Step 3: Synthesis of Imine-Containing Bio-based Oil: In the final step, 2 g of the aminated bio oil obtained from Step 2 and terephthaldehyde were mixed with 20 ml of THF. The resulting mixture was stirred overnight at room temperature, leading to the formation of the imine product. Excess solvent was removed using a rotary evaporator. This step achieved a yield of 98%.
By following these steps, the imine-containing bio-based oil is successfully synthesized. Each step involves specific reactants, reaction conditions, and yields, leading to the production of the imine containing castor oil for further use.
Example 2
Let's consider an example of preparing oxazoline-modified PCR ABS (interchangeably referred to as PCR ABS Ox) and vitrimers (interchangeably referred to as PCR ABS Ox V1/V2) using waste ABS materials:
Step 1: Cleaning and Cutting of PCR ABS: The PCR ABS, obtained from waste 3D printing materials, underwent a cleaning process. The PCR ABS was initially washed with an aqueous solution of detergent, followed by repeated washing in cold water. Afterward, the material was dried in a vacuum oven at 70°C for overnight. Once dried, the PCR ABS was chopped into small pieces, ready for further processing.
Step 2: Preparation of Oxazoline-modified PCR ABS (PCR ABS Ox): In this step, a sufficient amount of ethanolamine (6%), zinc acetate (0.05%), and the waste ABS materials were introduced into a melt mixer. The mixture was homogenized for 5 minutes at 150°C with a screw speed of 60 rpm. Once the screw speed was stable, the temperature was increased to 220°C, and the mixture was further mixed for 20 minutes. The process took place under a continuous nitrogen flow in an integrated recirculation channel. Extrusive ABS strips were then injection molded simultaneously to obtain ASTM standard samples for investigating the mechanical properties.
Step 3: Preparation of Vitrimer with PCR ABS Batches: In this step, the PCR ABS vitrimers were prepared using a twin-screw micro-compounder. The compounding system had a 15 cm3 capacity and featured a co-rotating conical screw profile and a recirculation channel, allowing control over the residence time. The melt mixing of PCR ABS Ox (oxazoline-modified PCR ABS) with the imine bio-based oil was performed at temperatures ranging from 210 °C to 240 °C. The screw speed was set at 60 RPM, and the mixing process lasted for 10 minutes. Different PCR ABS vitrimer batches were prepared, consisting of 98.5 to 99.9 wt% (percentage by weight) PCR ABS Ox and 0.1 to 1.5 wt% of the modified imine-containing bio-based oil derivatives.
Example 3
Several batches of PCR ABS were subjected to injection molding at a pressure of 3 Psi and temperatures ranging from 220 to 240 °C for a duration of 10 minutes. This was done to characterize the vitrimer samples. The formulation of the PCR ABS based vitrimer samples are shown in Table 1.
Table 1: Formulation Table of PCR ABS based Vitrimer.
Compound Name Wt.% of PCR ABS-Ox Wt.% of imine containing bio-based oil
PCR ABS Ox-V1 99.75% 0.25%
PCR ABS Ox-V2 99.50% 0.50%
FTIR analysis was performed on both the injection molded samples of PCR ABS Ox and the vitrimers. In the case of PCR ABS Ox, a distinct shoulder peak was observed at 1664 cm-1, which is attributed to the presence of oxazoline groups. This peak confirmed the successful conversion of PCR ABS to PCR ABS-Ox. Additionally, during the formation of PCR ABS Ox vitrimers with imine bio-based oil, the opening of the oxazoline ring and the formation of amide bonds occurred. A significant peak at 1640 cm-1 indicated the presence of imine within the PCR ABS Ox vitrimer.
Mechanical testing was conducted according to ASTM D638 (type V) to evaluate the stress-strain properties of the compounds. Tensile strength, elastic modulus, and elongation at break were among the parameters studied. The testing procedure involved applying a preload force of 0.1 N and using a cross-head speed of 50 mm/min for each specimen. The specimens, with dimensions of approximately 15 mm (gauge length) × 4.12 mm (width) × 2.1 mm (thickness), were tested multiple times for accuracy. The specimens were placed between clamps and pulled apart at a tensile speed of 50 mm/min until they broke. Results of the mechanical testing is shown in Table 2 provided below.
Table 2: Mechanical data for PCR ABS and their vitrimers with multiple recycle.
Compound Name No. of Recycle Young Modulus % recovery in Y. M. Yield Strength (MPa) % recovery in Y.S. Elongation at Break (%) % recovery in EB
PCR ABS R1 9.4 -- 49 -- 31.6 --
R5 10.8 >100% 52 >100% 18.2 56%
PCR ABS Ox R1 10.9 -- 50 -- 28.6 --
R5 10.4 95.5% 52 ˃100% 22.1 78%
PCR ABS Ox-V1 R1 10.4 -- 52 -- 18.5 --
R5 10.8 ˃100% 53 ˃100% 19.2 ˃100%
PCR ABS Ox-V2 R1 10.7 -- 56 -- 6.8 --
R5 11.0 ˃100% 60 ˃100% 10.3 ˃100%
The broken PCR ABS Ox vitrimers were subsequently cut into small pieces and subjected to extrusion and injection molding for several cycles. The mechanical data, as shown in Table-2, compares the properties of PCR ABS and its vitrimers at different recycling stages. Notably, for PCR ABS-Ox vitrimers, the yield strength showed a surprising increase from the first to the fifth cycle (R1 to R5). Both PCR ABS Ox-V1 and PCR ABS Ox-V2 exhibited yield strength recovery rates exceeding 100% even after the fifth recycle (R5). This can be attributed to the formation of dynamic covalent bonds through imine exchange reactions within the vitrimers of PCR ABS Ox.
Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments. The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the present disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination or as suitable in any other described embodiment of the disclosure. , Claims:1. A method (100) of recycling post-consumer recycled (PCR) acrylonitrile butadiene styrene (ABS), the method (100) comprising:
converting the PCR ABS having a first mechanical strength into oxazoline-modified PCR ABS (206);
performing melt mixing of the oxazoline-modified PCR ABS (206) with an imine-containing oil (306); and
performing melt extrusion of a mixture of the oxazoline-modified PCR ABS (206) and the imine-containing oil (306) to synthesize a PCR ABS vitrimer (308) having a second mechanical strength greater than the first mechanical strength in a first recycling operation.

2. The method (100) as claimed in claim 1, wherein the converting of the PCR ABS into the oxazoline-modified PCR ABS (206) comprises:
feeding a mixture of mono-ethanol amine, zinc acetate, and the PCR ABS into a melt mixer; and
homogenizing the mixture for 5 to 20 minutes at a temperature ranging from 200 to 230 degrees Celsius with a uniform screw speed ranging from 60 to 100 rotations per minute (RPM).

3. The method (100) as claimed in claim 1, wherein the imine-containing oil (306) is a non-edible bio-based oil.

4. The method (100) as claimed in claim 1, wherein the imine-containing oil (306) is pre-synthesized before melt mixing with the oxazoline-modified PCR ABS (206), and wherein the imine-containing oil (306) is pre-synthesized by preparing a maleated oil by reacting a bio-based oil with maleic anhydride and a peroxide initiator under pre-defined conditions, resulting in a maleated oil product.

5. The method (100) as claimed in claim 4, wherein the imine-containing oil (306) is pre-synthesized further by causing amination of the maleated oil by reacting the maleated oil product with an amine compound in the presence of an initiator and a solvent, followed by purification to obtain an aminated oil product.

6. The method (100) as claimed in claim 5, wherein the imine-containing oil (306) is pre-synthesized further by reacting the aminated oil product with an aldehyde compound in the presence of a solvent, followed by removal of excess solvent to obtain the imine-containing oil (306).

7. The method (100) as claimed in claim 1, wherein the melt mixing of the oxazoline-modified PCR ABS (206) and the imine-containing oil (306) is performed for a time period ranging from 3 to 10 minutes.

8. The method (100) as claimed in claim 7, wherein the melt mixing of the oxazoline-modified PCR ABS (206) and the imine-containing oil (306) is performed at a temperature ranging from 200 to 240 degrees Celsius with a uniform screw speed ranging from 60 to 100 rotations per minute (RPM).

9. The method (100) as claimed in claim 1, wherein in each recycling operation starting from the first recycling operation up to a defined number of recycling operations, a mechanical strength of the PCR ABS vitrimer (308) synthesized by the melt extrusion of the mixture of the oxazoline-modified PCR ABS (206) and the imine-containing oil (306) is incrementally increased, and wherein each recycling operation is an upcycling due to the increase in the mechanical strength.

10. The method (100) as claimed in claim 1, wherein the PCR ABS vitrimer (308), synthesized by the melt extrusion of the mixture of the oxazoline-modified PCR ABS (206) and the imine-containing oil (306), comprises a dynamic Covalent Adaptable Network (CAN) to impart re-processability to the PCR ABS vitrimer (308), and wherein the dynamic CAN is formed through an imine exchange reaction within the PCR ABS vitrimer (308) using an imine functional group of the imine-containing oil (306).

11. The method (100) as claimed in claim 1, wherein the PCR ABS vitrimer (308) comprises 98.5 to 99.9 percent by weight of the oxazoline-modified PCR ABS (206) and 0.1 to 1.5 percent by weight of the imine-containing oil (306).

12. A post-consumer recycled (PCR) acrylonitrile butadiene styrene (ABS) vitrimer composition, comprising:
98.5 to 99.9 percent by weight of oxazoline-modified PCR ABS (206); and
0.1 to 1.5 percent by weight of an imine-containing oil (306).