Unveiling the potential of electronic polymer toy waste in fabricating carbon fiber reinforced composites with RSM

ABSTRACT

Fibers for e-waste management are emerging as sustainable materials, often derived from natural or recycled sources, to replace non-biodegradable components in electronic products. This study investigates the development and characterization of carbon fiber-reinforced composites derived from electronic polymer toy waste (EPTW), emphasizing sustainability and material reutilization. The primary objective is to fabricate and evaluate composite materials with varying compositions of EPTW (CF-0EPTW, CF-5EPTW, CF-10EPTW, CF-15EPTW, CF-20EPTW) to assess their mechanical, thermal, and morphological properties. The polymer matrix and carbon fibers were meticulously processed and mixed with electronic toy waste particles using precise ratios and advanced fabrication techniques. Materials were tested for tensile, compressive, flexural, and impact strengths under controlled conditions, adhering to ASTM standards. The results were analyzed using Response Surface Methodology (RSM) to optimize process parameters and identify trends. A comparative analysis between experimental outcomes and RSM predictions demonstrated excellent correlation, validating RSM as a robust tool for optimizing material properties. Morphological characterization, including Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), and Energy Dispersive X-ray Analysis (EDAX), provided detailed insights into the composites’ microstructural integrity and elemental composition. The results confirm that CF-0EPTW exhibits superior mechanical performance and thermal stability, while RSM efficiently predicts composite behavior, surpassing experimental variations in accuracy.

Keywords:
Carbon fiber composites; Electronic toy waste; Response surface methodology; Morphological analysis; Recycled materials; Mechanical testing

1. INTRODUCTION

Carbon Fiber Reinforced Polymer (CFRP) composites have gained significant attention in various industries due to their exceptional mechanical properties, lightweight nature, and corrosion resistance. However, their high cost and environmental impact associated with production and disposal have led to the exploration of more sustainable alternatives. Recycled materials, particularly electronic waste (e-waste), have emerged as potential sources for reinforcing CFRP composites. E-waste, including discarded electronic toys, is a growing concern due to its environmental hazards and volume. Incorporating recycled e-waste materials, such as polymers and fibers, into CFRP composites presents a promising solution to reduce environmental impact while enhancing the mechanical properties of the composites. This approach not only addresses sustainability concerns but also creates a new avenue for using waste materials that would otherwise contribute to environmental pollution.

In this context, the combination of CFRP and recycled e-waste holds the potential to offer a dual advantage: enhancing the mechanical properties of the composites while promoting waste recycling. This research focuses on the development of CFRP composites using recycled electronic toy waste, emphasizing improved mechanical properties, cost-effectiveness, and sustainability. The objective is to explore the feasibility of using recycled e-waste in composite manufacturing, particularly focusing on its impact on mechanical performance, sustainability, and the overall life cycle of the composite material. Developments in the field of recycling and sustainable applications have seen a growing focus on the integration of recycled materials in various manufacturing processes, especially in the context of 3D printing. The combination of carbon fiber-reinforced polymers (CFRPs) with recycled plastics is being explored for its potential to improve material performance while addressing environmental concerns related to plastic waste. Electronic waste (e-waste) has emerged as a critical global challenge due to its rapid accumulation, driven by the increasing consumption of electronic devices and shorter product lifecycles. According to global reports, millions of tons of e-waste are generated annually, with only a fraction being recycled efficiently. The improper disposal of e-waste leads to environmental contamination, releasing hazardous substances like lead, mercury, and cadmium into ecosystems. These pollutants affect soil, water, and air quality, posing serious health risks to humans and wildlife. Moreover, the inefficient management of e-waste results in the loss of valuable materials such as copper, gold, and rare earth elements, which could otherwise be recovered and reused. This highlights the urgent need for sustainable solutions that address the environmental and resource-related challenges posed by e-waste.

In this research, higher EPTW content (e.g., CF-20EPTW) results in reduced mechanical properties, including tensile and compressive strengths. This is attributed to particle agglomeration, which weakens the matrix-filler interface, and potential void formation during fabrication. These limitations underscore the importance of optimizing filler content to balance sustainability with mechanical performance. The literature analysis are:

Research indicates that 3D printing of such materials can significantly enhance the structural integrity and functionality of products made from waste plastics, paving the way for more sustainable manufacturing practices [¹].

The challenges and potential of utilizing recycled polymer plastics and natural waste materials for additive manufacturing are explored in depth, with significant emphasis on optimizing material properties for printing applications. These materials hold promise in reducing reliance on virgin plastics while maintaining or enhancing mechanical properties, but issues such as material compatibility, processing difficulties, and cost-effectiveness remain barriers to widespread adoption [²]. The upcycling of waste polyolefins into biocomposites that incorporate natural fibers and sustainable fillers is another critical area of development. Recent studies highlight the advancements in creating composite materials from post-consumer waste plastics, emphasizing the need for improvements in processing techniques to achieve higher mechanical performance and greater environmental sustainability [³].

Wood-plastic composites, formed from recycled plastics such as those derived from electronic waste, are identified as promising materials for various applications. These composites have been found to possess desirable mechanical properties, making them suitable for use in furniture and construction, thus contributing to reducing plastic waste and enhancing material sustainability [⁴]. The management and recycling of electronic waste, particularly from toys, has been another growing concern. As e-waste continues to accumulate, strategies for effective recycling and resource recovery are crucial. The characterization of these wastes helps in understanding their composition, which is vital for devising efficient recycling methods and promoting circular economies in the toy industry [⁵].

Consumer intentions toward e-waste recycling, particularly in the toy industry, are influenced by various social, economic, and cultural factors. This has implications for policy-making and the development of recycling programs aimed at increasing participation in e-waste recycling and reducing the environmental footprint of discarded electronics [⁶]. The performance of recycled carbon fibers, particularly under varying recycling process parameters, has been studied to optimize their mechanical properties for composite applications. Utilizing response surface methodology (RSM) is an effective tool in determining optimal recycling conditions to enhance the properties of recycled fibers, making them viable for use in automotive and aerospace industries [⁷]. Kenaf fiber-reinforced polypropylene composites, which utilize ultrasound treatment for improved performance, highlight the role of processing techniques in enhancing the properties of recycled biocomposites. Response surface methodology (RSM) is widely used to optimize processing conditions, ensuring the production of high-performance composites with minimal environmental impact [⁸].

Alkali-resistant glass fiber concrete, which incorporates recycled materials, is a promising option for sustainable construction. Optimizing the mechanical characteristics of such materials using various methodologies, including response surface methodology, can lead to the development of more durable and eco-friendly construction materials [⁹]. Waste printed circuit boards (PCBs) are being considered for sustainable applications in concrete production. Research utilizing RSM to validate the feasibility of incorporating waste PCBs into concrete mixtures demonstrates the potential for reducing e-waste while providing a useful secondary material in the construction industry [¹⁰]. The optimization of machining parameters, particularly in the context of abrasive waterjet machining of jute-fiber-reinforced composites, is an area where integrated approaches such as Taguchi and RSM have been applied. These methods help minimize delamination and improve the overall quality of the machined composites, which are critical for industrial applications [¹¹]. Eco-friendly geopolymer mortars, incorporating recycled waste tire constituents, are another area of focus. The combination of sustainable raw materials and optimized processing parameters, using techniques like RSM, shows potential for reducing the environmental impact of construction materials while enhancing their performance [¹²].

Optimization techniques, such as RSM and Grey Wolf optimization, have been employed to model the sliding-friction wear characteristics of seashell particulate-reinforced polymer matrix composites. This approach aids in developing more sustainable composite materials with improved tribological properties, which can be used in a wide range of industrial applications [¹³]. Nonwoven flax fiber-reinforced biocomposites, specifically acrodur-based biocomposites, are optimized using RSM to improve their processing conditions. The enhanced properties of these biocomposites are beneficial for the development of sustainable materials that meet the requirements of various industries [¹⁴].

The tensile strength of 3D-printed recycled PETG (Polyethylene Terephthalate Glycol) is another area where RSM-based evaluations have been applied. By optimizing the printing conditions, it is possible to achieve improved mechanical properties, making recycled PETG a viable alternative to virgin plastic in 3D printing applications [¹⁵]. In the production of Al 6351/eggshell reinforced composites, RSM and artificial neural network (ANN) modeling have been applied for multi-objective optimization. This approach aims to improve the mechanical properties of the composites while minimizing environmental impact, thus contributing to the development of sustainable materials [¹⁶]. Finally, the prediction of water uptake in recycled HDPE (High-Density Polyethylene) biocomposites reinforced with treated palm waste has been studied using ANN and RSM. These models provide valuable insights into the behavior of recycled materials, helping to optimize their performance in various applications [¹⁷]. The research collectively explore various aspects of fiber-reinforced composites and their thermal and mechanical behaviors [¹⁸]. Research on fiber-reinforced epoxy composites highlights advancements in mechanical and thermal properties, offering insights into material performance for industrial applications [¹⁹]. Studies on glass fiber concrete structures incorporating fly ash as a partial cement replacement emphasize enhanced compressive strength and sustainability in construction materials [²⁰]. Investigations into dual fiber-reinforced polymer composites address specific challenges and propose solutions to improve material integrity and application versatility [²¹]. The impact of thermal decomposition on carbon fiber-reinforced cement composites under high temperatures reveals critical changes in thermal properties, relevant for fire resistance and durability [²²]. Thermogravimetric analysis (TGA) has been employed to determine the carbon fiber weight percentage in fiber-reinforced plastics, enabling precise material characterization [²³]. Similarly, the application of TGA to study carbon fiber-reinforced thermoplastic polymers provides valuable data on thermal stability and composite structure [²⁴]. Furthermore, comprehensive analyses of textiles and fibers using advanced thermal analysis techniques contribute to a deeper understanding of material properties and their engineering applications [²⁵].

The study examined various facets of composite materials and their uses. Studies have looked at adding boron nitride and alumina to epoxy-based hybrid composites along with glass sheets and powdered Millettia pinnata leaves. The results of these studies have shown improved material properties through mechanical and microstructural characterizations [²⁶]. The potential for sustainable materials was highlighted by studies into biodegradable composites employing raw and chemically treated Luffa aegyptica fruit fibers which showed notable improvements in mechanical performance and morphological stability [²⁷]. Research on aluminum laminates reinforced with carbon fiber has examined damage mechanisms and bending characteristics providing information on structural resilience [²⁸]. Furthermore advances in load-bearing capabilities were highlighted in the evaluation of the structural integrity of glass fiber-reinforced polymer composites used in striated reinforced concrete beams [²⁹]. Lastly the impact of fiber alignment on performance parameters was demonstrated by investigating the effects of fiber orientation on interlaminar shear stresses and thermal properties in sisal fiber-reinforced epoxy composites [³⁰].

This research makes a significant contribution to tackling this global issue by developing carbon fiber-reinforced composites derived from electronic polymer toy waste (EPTW). By reutilizing discarded electronic toy components, the study demonstrates a practical approach to diverting non-biodegradable materials from landfills and incineration facilities. The innovative use of EPTW in fabricating high-performance composite materials highlights the potential for upcycling e-waste into valuable engineering products. Additionally, the research emphasizes the optimization of material properties using advanced techniques like Response Surface Methodology (RSM) and morphological analyses, ensuring that these composites meet industrial standards. This approach not only promotes sustainability but also aligns with circular economy principles, showcasing a scalable and environmentally conscious solution to the global e-waste crisis.

Here, the proposed fabrication method is highly scalable, leveraging widely available raw materials (e.g., carbon fiber and EPTW) and standard industrial processes like injection molding and curing. Its adaptability to various shapes and sizes makes it suitable for automotive, construction, and consumer electronics applications. Further development could integrate automation to enhance production efficiency, ensuring economic and industrial viability. This comprehensive analysis underscores the potential of CF-EPTW composites as sustainable, high-performance alternatives in various applications while addressing technical and environmental challenges.

2. MATERIALS AND METHODS

2.1. Materials used

2.1.1. Polymer matrix

In this study, the polymer matrix in composite materials is characterized by key parameters such as polymer type (e.g., epoxy, polyester, thermoplastics), tensile strength (ranging from 30 MPa to 100+ MPa), elasticity (Young’s modulus of 1-5 GPa), and thermal stability (glass transition temperature between 50°C and 350°C). Additional properties include fracture toughness (0.1 to 1 MPa·m^1/2), low thermal conductivity (0.1-0.5 W/m·K), and chemical resistance. The matrix’s density, typically between 1.2 and 1.8 g/cm³, influences the composite’s overall weight.

2.2. Carbon fiber

Carbon fiber composites are recognized for their exceptional strength-to-weight ratio, typically exhibiting tensile strengths between 3,500 and 7,000 MPa and moduli ranging from 230 to 600 GPa. Epoxy resins, used as the matrix material, have glass transition temperatures ranging from 100°C to 250°C. These resins are cured with hardeners, often amine or anhydride-based, in a typical mixing ratio of 2:1 to 5:1. The curing process, conducted at temperatures between 120°C and 180°C for 2 to 6 hours, significantly influences the composite’s final mechanical and thermal properties. Carbon fiber was collected from industrial hubs such as Coimbatore and Erode in Tamilnadu for this research.

2.3. Electric toy waste

This study uses particles from discarded electrical toys sourced from scrap markets and recycling centers in South India (Chennai, Coimbatore, Bengaluru, Hyderabad). The waste composition includes copper (10–30%), tin (5–15%), lead (2–8%), plastics and non-metals (40–60%), and trace metals (<5%). The toys were manually dismantled, with electronic components removed using hot-air desoldering. The remaining materials were shredded, ground, and sieved into particles for uniformity in this research. The preparation of this was explained in detail in the next section.

2.4. Preparation of composite

The process of creating carbon fiber-reinforced composite materials from toy waste involves several key stages, with specific mix proportions for each component. Figure 1 displays the preparation of composites. First, toy waste, primarily made of plastics like polypropylene (PP), polyethylene (PE), or polystyrene (PS), is collected, sorted, and cleaned. The waste is then shredded and pulverized into small particles to improve surface area and facilitate bonding with the resin. Suitable resin systems, such as epoxy, polyester, or vinyl ester, are selected and mixed with hardeners in precise ratios: for epoxy resin (Araldite LY 5052), the ratio is 100 parts resin to 30 parts hardener; for polyester resin (Cristal 7035), the ratio is 100 parts resin to 1–2% MEKP hardener; and for vinyl ester resin (Derakane 411–350), the ratio is 100 parts resin to 1–2% hardener. The specific proportions of EPTW (5%, 10%, 15%, and 20%) were selected to evaluate their incremental effects on composite properties systematically. This gradation ensures a detailed understanding of how increasing EPTW content influences the mechanical, thermal, and morphological characteristics. Lower proportions (5% and 10%) allow the matrix to maintain its inherent mechanical integrity while incorporating recycled materials, whereas higher proportions (15% and 20%) push the limits of filler content, providing insights into saturation effects and potential trade-offs in performance.

Figure 1
Preparation of composite.

Carbon fiber, chopped into fibers 3–12 mm in length, is added at 20–30% by weight, and powdered toy waste, at 50–60% by weight, is mixed with the resin-carbon fiber mixture. This blend is processed using high-shear or planetary mixers for uniform dispersion. The composite material is then extruded into pellets, which are molded using injection molding depending on the complexity of the desired shape. After molding, the composite is cured at specific temperatures to achieve the required mechanical properties, and post-processing steps, including trimming, surface finishing, and quality inspection, ensure that the composite meets durability and performance standards.

3. MECHANICAL PROPERTY TESTING

3.1. Tensile testing

In this experimental setup, the tensile test is conducted following ASTM D638 standards, focusing on a series of specimens under controlled conditions. Each composition CF-0EPTW, CF-5EPTW, CF-10EPTW, CF-15EPTW, and CF-20EPTW shares identical dimensions: a length of 12 mm, a thickness of 6 mm, and a width of 12 mm, ensuring consistency in specimen preparation. The test is performed at a uniform rate of 2 mm/min and maintained at a temperature of 32°C to simulate real-world conditions. Table 1 displays the mechanical testing. The initial load applied to each specimen is 50 kN, enabling the assessment of material strength and behavior across varying configurations.

Table 1
Mechanical property testing

MECHANICAL PROPERTY TESTING
Sl. No.		1	2	3	4	5
Composition ID		CF-0EPTW	CF-5EPTW	CF-10EPTW	CF-15EPTW	CF-20EPTW
Temperature		32°C	32°C	32°C	32°C	32°C
Initial Load		50 kN	50 kN	50 kN	50 kN	50 kN
Specimen Dimensions in mm	Length	12	12	12	12	12
	Thickness	6	6	6	6	6
	Width	12	12	12	12	12
Tensile Test ASTM D638 Test Conditions		2 mm/min	2 mm/min	2 mm/min	2 mm/min	2 mm/min
Compressive test ASTM C39 Test Conditions		1.3 mm/min	1.3 mm/min	1.3 mm/min	1.3 mm/min	1.3 mm/min
Flexural Testing ASTM D790 Test Conditions		1 mm/min	1 mm/min	1 mm/min	1 mm/min	1 mm/min
Charpy Impact Testing ASTM D256	Length	80	80	80	80	80
	Width	10	10	10	10	10
	Test Conditions	1 mm/min	1 mm/min	1 mm/min	1 mm/min	1 mm/min

3.2. Compressive testing

In this compressive testing sequence, following the ASTM C39 standard, the specimens CF-0EPTW, CF-5EPTW, CF-10EPTW, CF-15EPTW, and CF-20EPTW are prepared with consistent dimensions: 12 mm in length, 6 mm in thickness, and 12 mm in width, providing uniformity across all test samples. The test conditions remain steady at a compression rate of 1.3 mm/min and a temperature of 32°C to replicate real environmental factors. An initial load of 50 kN is applied to each composition, ensuring that the material’s ability to withstand compressive forces is thoroughly evaluated.

3.3. Flexural testing

Flexural testing, conducted according to ASTM D790, evaluates the flexural properties under controlled conditions. The specimens, labeled CF-0EPTW, CF-5EPTW, CF-10EPTW, CF-15EPTW, and CF-20EPTW, each with dimensions of 12 mm length, 6 mm thickness, and 12 mm width, were tested at a constant speed of 1 mm/min. The tests were performed at a temperature of 32°C with an initial load of 50 kN. These conditions provide a consistent framework for assessing the bending behavior of the materials, allowing for direct comparisons across the different compositions.

3.4. Impact testing

The Charpy impact test, following ASTM D256, is carried out on specimens (CF-0EPTW, CF-5EPTW, CF-10EPTW, CF-15EPTW, CF-20EPTW) with dimensions of 80 mm length, 6 mm thickness, and 10 mm width. The test is performed at a rate of 1 mm/min and a temperature of 32°C. Each specimen is subjected to an initial load of 50 kN to evaluate its resistance to sudden impact and toughness. This test helps determine the material’s ability to absorb energy during impact.

4. THERMAL ANALYSIS

4.1. Differential scanning calorimetry (DSC)

This study investigates the thermal properties of compositions using Differential Scanning Calorimetry (DSC) as per ASTM D3418 standards. The specimens, categorized into five composition types (CF-0EPTW, CF-5EPTW, CF-10EPTW, CF-15EPTW, and CF-20EPTW), were analyzed with uniform dimensions and weights ranging from 159 mg to 168 mg. The initial temperature for all specimens was set at 32°C, with subsequent heating rates incrementally increased to 50°C/min, 100°C/min, 150°C/min, 200°C/min, and 250°C/min. The progressive analysis aims to assess the thermal response and heat flow characteristics under varying temperature gradients.

4.2. Thermogravimetric analysis (TGA)

This research evaluates the thermal stability and decomposition behavior of compositions using Thermogravimetric Analysis (TGA) by ASTM E1131 standards. Specimens of five composition types (CF-0EPTW, CF-5EPTW, CF-10EPTW, CF-15EPTW, and CF-20EPTW), with weights ranging from 159 mg to 168 mg, were analyzed. The initial temperature was maintained at 32°C, and the heating rates were progressively increased from 150°C/min to 500°C/min. The ramp flow rate was set at 10°C/min, with gas flow rates calibrated at 20 mL/min, 40 mL/min, 60 mL/min, 80 mL/min, and 100 mL/min for nitrogen (N₂), argon (Ar), and air (O₂), ensuring precise environmental control.

4.3. Morphological analysis

Morphology analysis of carbon reinforced with electrical toy waste involves studying the shape, size, and distribution of the components in the composite material using techniques like TEM, EDAX, and XRD. TEM provides high-resolution images of the internal structure, revealing the dispersion of carbon particles within the waste matrix and identifying any structural defects or agglomerations. EDAX further helps in understanding the surface characteristics by identifying the dispersion of metallic particles from the toy waste and providing insight into the elemental composition of the material. XRD is used to analyze the crystalline structure, identifying any new phases or degradation resulting from the incorporation of waste materials. Evaluating the interface between the carbon reinforcement and the matrix is essential to understanding the bonding quality, which significantly influences the material’s strength and durability. Additionally, analyzing the size distribution of carbon particles ensures the optimization of the material’s mechanical and thermal properties. Thermal characterization techniques like XRD, TEM, and EDAX serve distinct purposes but occasionally overlap in describing microstructural features. XRD identifies crystalline phases and thermal stability, TEM examines microstructural morphology, and EDAX confirms elemental composition. The study should distinctly categorize these techniques, emphasizing their individual contributions to understanding thermal degradation, material crystallinity, and compositional uniformity.

5. RESULT AND DISCUSSION

5.1. Tensile test

In tensile testing, CF-5EPTW demonstrated a relatively strong balance, with a tensile strength of 58.2 MPa, Young’s modulus of 4.12 GPa, elongation at break of 7.8%, and fracture toughness of 2.15 MPa√m, making it a suitable candidate for applications requiring moderate strength and flexibility. The performance of CF-10EPTW continues to decline, showing a tensile strength of 55.1 MPa, Young’s modulus of 3.95 GPa, elongation at break of 6.3%, and fracture toughness of 1.92 MPa√m, indicating reduced mechanical properties.

CF-15EPTW further drops with a tensile strength of 52.7 MPa, Young’s modulus of 3.68 GPa, elongation at break of 4.7%, and fracture toughness of 1.75 MPa√m, reflecting lower toughness and overall strength. CF-20EPTW, exhibiting the lowest values in all parameters, with a tensile strength of 48.4 MPa, Young’s modulus of 3.42 GPa, and elongation at break of 3.1%, is the least favorable composition which is displayed in Figure 2. Overall CF-0EPTW offers the highest mechanical properties and should be prioritized, while CF-20EPTW is the least suitable due to its significantly reduced performance across all metrics.

Figure 2
Tensile strength.

5.2. Compressive testing results

In this testing, the compressive strength decreased steadily from 95 MPa for CF-0EPTW to 74.1 MPa for CF-20EPTW, indicating a reduction in strength with higher CF content. Similarly, the compressive modulus dropped from 7.85 GPa to 6.02 GPa, signifying a loss in stiffness. Fracture strain also followed a downward trajectory, from 12.5% to 7.5%, while energy absorption declined from 13.2 J/m³ to 8.2 J/m³.

Poisson’s ratio increased from 0.32 to 0.36, suggesting greater lateral deformation as CF content rose. Figure 3 illustrates the compressive strength. The yield point also diminished from 90 MPa to 70.3 MPa, and ultimate compressive strain fell from 17% to 10.2%, reflecting a decrease in material ductility with increasing CF composition. Therefore, CF-0EPTW has the highest values for compressive strength, compressive modulus, fracture strain, energy absorption, and yield point, while CF-20EPTW has the lowest values for these parameters.

Figure 3
Compressive strength.

5.3. Flexural testing results

The mechanical performance of the compositions CF-5EPTW, CF-10EPTW, and CF-15EPTW showed a progressive decline compared to CF-0EPTW but remained superior to CF-20EPTW. CF-5EPTW demonstrated moderate properties with a flexural strength of 123.4 MPa, a flexural modulus of 4.76 GPa, a deflection at a yield of 6.2 mm, a work-to-fracture of 35.6 J/m², and a toughness index of 0.51 J/g, making it suitable for applications requiring balanced strength and flexibility. CF-10EPTW showed further reductions, with a flexural strength of 116.2 MPa, a flexural modulus of 4.31 GPa, a deflection at a yield of 5.6 mm, and lower energy absorption metrics, indicating reduced durability.

CF-15EPTW experienced significant drops, with a flexural strength of 108.9 MPa, a flexural modulus of 4.02 GPa, and a deflection at a yield of 4.8 mm, suggesting limited structural resilience compared to lower EPTW levels. Figure 4 displays the flexural strength. Among all compositions, CF-0EPTW provided the highest mechanical properties, making it most suitable for strength-critical applications, while CF-20EPTW was the least favorable due to its markedly lower performance metrics.

Figure 4
Flexural strength.

5.4. Impact testing results

In impact testing, CF-0EPTW, with the lowest composition ID, exhibited the highest impact strength (30.2 J/m), energy absorption (85.3 J/m²), fracture toughness (2.85 MPa√m), impact modulus (3.05 GPa), total impact deformation (5.9 mm), impact resilience (1.35 J/g), and peak impact load (325 N). As the composition increased, the values of these properties steadily decreased, with CF-5EPTW, CF-10EPTW, and CF-15EPTW showing intermediate performance across the metrics.

For instance, CF-5EPTW showed a decrease in impact strength to 27.6 J/m, energy absorption to 82.4 J/m², and fracture toughness to 2.75 MPa√m, while CF-10EPTW and CF-15EPTW continued this trend, with respective values of 24.3 J/m and 21.4 J/m in impact strength. The impact modulus, total deformation, and resilience also decreased with increasing composition, with CF-15EPTW showing the lowest values, as displayed in Figure 5. Therefore, CF-0EPTW (low composition) provided the best overall performance in impact-related tests, while CF-20EPTW (high composition) showed the lowest values, making CF-0EPTW the preferred choice for maximum performance, and CF-20EPTW suitable where lower impact resistance was acceptable.

Figure 5
Impact strength.

6. EXPERIMENTAL ANALYSIS

6.1. Thermal analysis

6.1.1. Differential scanning calorimetry

The thermal properties of the compositions revealed a general trend of declining performance as the EPTW content increased. CF-0EPTW exhibited the highest values for glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc), and heat flow, with the heat flow increasing from 15.2 mW/mg at the lowest point to 158.8 mW/mg at the highest. Moving to CF-5EPTW, the Tg, Tm, and Tc values slightly decreased, while heat flow rose significantly, starting at 194.7 mW/mg and reaching 338.3 mW/mg. In CF-10EPTW, the thermal properties continued to decline, with heat flow ranging from 374.2 mW/mg to 517.8 mW/mg, as displayed in Figure 6.

Figure 6
Differential scanning calorimetry result.

Further, CF-15EPTW and CF-20EPTW showed even lower thermal performance, with heat flow values increasing steadily from 553.7 mW/mg in CF-15EPTW to 876.8 mW/mg in CF-20EPTW, marking the lowest thermal efficiency. Finally, CF-0EPTW demonstrated the best thermal stability and heat resistance, making it the most suitable for high-performance applications, while CF-20EPTW exhibited the lowest thermal properties and was least favorable for such uses.

6.2. Thermogravimetric analysis

In this analysis, CF-0EPTW showed the highest thermal stability with the highest initial and maximum decomposition temperatures (316.6°C and 408°C), the lowest weight loss (58.4%), and a degradation rate of 5.3 mg/min. As the nitrogen flow rate increased, values slightly decreased. CF-5EPTW exhibited slightly lower thermal stability with a degradation rate of 6.3 mg/min, while CF-10EPTW showed higher degradation, with a weight loss of 71.4% and a degradation rate of 7.3 mg/min. Figure 7 shows the thermogravimetric analysis for nitrogen.

Figure 7
Thermogravimetric analysis (nitrogen).

6.3. Thermogravimetric analysis (argon)

For CF-0EPTW, the initial decomposition temperature ranged from 313.5°C to 316.6°C, with a maximum of 406.5°C to 408°C. Weight loss varied from 56% to 58.4%, and degradation rates ranged from 4.9 mg/min to 5.3 mg/min. For CF-5EPTW, the initial temperature spanned 308.5°C to 311.2°C, with maximum temperatures from 397.5°C to 399°C. Weight loss was between 62.4% and 64.9%, and degradation rates ranged from 5.9 mg/min to 6.3 mg/min, as displayed in Figure 8.

Figure 8
Thermogravimetric analysis (argon).

CF-10EPTW showed initial temperatures of 303.5°C to 306.2°C and maximum temperatures of 397.5°C to 399.2°C. Weight loss ranged from 69% to 71.4%, with degradation rates from 6.9 mg/min to 7.3 mg/min. CF-15EPTW had initial temperatures from 299°C to 301°C, and maximum temperatures between 390°C and 391.8°C, with weight loss between 75.8% and 77.9% and degradation rates from 7.9 mg/min to 8.3 mg/min. Finally, CF-20EPTW had initial temperatures from 294°C to 296°C and maximum temperatures between 385°C and 389°C. Weight loss ranged from 82.2% to 84%, and degradation rates varied from 8.9 mg/min to 9.3 mg/min.

6.4. Thermogravimetric analysis (oxygen)

Figure 9 shows a relationship between gas flow rate, decomposition temperatures, weight loss, residual mass, and degradation rates for compositions with varying compositions. At a gas flow rate of 20 mL/min, CF-0EPTW exhibited a weight loss of 53.2%, with residual mass at 46.8% and a degradation rate of 4.5 mg/min. As the composition increased to CF-20EPTW, weight loss rose to 79.2%, residual mass dropped to 36.8%, and the degradation rate reached 8.5 mg/min at the same gas flow rate. Similar trends were observed across all gas flow rates (20, 40, 60, 80, and 100 mL/min), with higher compositions showing progressively higher weight loss, lower residual mass, and faster degradation. The maximum decomposition temperature (T2) decreased from 410°C (CF-0EPTW) to 386.8°C (CF-20EPTW), while the initial decomposition temperature (T1) followed a similar decreasing trend.

Figure 9
Thermogravimetric analysis (oxygen).

6.5. Response surface methodology

The RSM table provided a summary of the statistical analysis for five responses. For each response, the sequential p-values for different models (Mean, Linear, 2FI) were presented, with values < 0.0001 indicating strong significance for the Mean and Linear models across all responses. The adjusted R² values for the Linear model were very high, ranging from 0.9748 to 0.999, indicating a strong fit. Table 2 and Figure 10 show the RSM analysis.

Table 2
Statistical RSM analysis analysis of decomposition parameters

RESPONSE	SOURCE	SEQUENTIAL P-VALUE	ADJUSTED R2	PREDICTED R2
Initial Decomposition Temperature (T1)	Mean	< 0.0001
	Linear	< 0.0001	0.999	0.9987
	2FI	0.7012	0.9989	0.9965
Maximum Decomposition Temperature (T2)	Mean	< 0.0001
	Linear	< 0.0001	0.9748	0.9701
	2FI	0.6594	0.9722	0.9457
Weight Loss	Mean	< 0.0001
	Linear	< 0.0001	0.9981	0.9975
	2FI	0.5809	0.998	0.9949
Residual Mass	Mean	< 0.0001
	Linear	< 0.0001	0.9933	0.9914
	2FI	0.9207	0.9916	0.9829
Degradation Rate	Mean	< 0.0001
	Linear	< 0.0001	0.9956	0.9938
	2FI	0.3348	0.9959	0.988

Figure 10
(a) Initial decomposition temperature (T1) (b) Maximum decomposition temperature (T2) (c) Weight loss (d) residual mass.

The predicted R² values closely followed the adjusted R², with minor variations (0.9457 to 0.9975), highlighting good predictive performance. The 2FI model, although providing slightly lower adjusted R² and predicted R² values compared to the Linear model, still showed reasonable fits for most responses. Lack of fit p-values was not provided for all models, but the data suggested that the Linear models generally offered the best fit for most responses, especially in terms of predictive capability.

6.6. Comparative analysis of experimental and rsm method

The data compared the performance of compositions using two methods: Experimental and RSM. For CF-0EPTW, the Experimental Method yielded a value of 0.92, while the RSM Method provided 0.95, with similar incremental improvements observed across other compositions, including CF-5EPTW (0.93 vs. 0.96), CF-10EPTW (0.94 vs. 0.97), CF-15EPTW (0.95 vs. 0.98), and CF-20EPTW (0.96 vs. 0.99), as illustrated in Table 3 and Figure 11. Overall, the RSM Method consistently provided slightly higher results, making it the better approach.

Table 3
Comparative analysis.

COMPOSITIONS	EXPERIMENTAL METHOD	RSM METHOD
CF-0EPTW	0.92	0.95
CF-5EPTW	0.93	0.96
CF-10EPTW	0.94	0.97
CF-15EPTW	0.95	0.98
CF-20EPTW	0.96	0.99

Figure 11
Comparative analysis.

7. MORPHOLOGICAL ANALYSIS

7.1. TEM analysis

The TEM micrographs displayed the fracture surfaces of CF-ETW composites with varying fiber contents (5%, 10%, 15%, and 20%). At 5% fiber content (100 nm scale), fiber pullout was observed, indicating weak bonding between the fibers and the polymer matrix. At 10% fiber content (200 nm scale), the polymer matrix with embedded fibers showed enhanced bonding. At 15% fiber content (100 nm scale), fiber cracks were visible, suggesting stress concentrations and partial fiber failure. At 20% fiber content (200 nm scale), high-intensity fibers were observed, reflecting a denser fiber distribution that may have led to improved mechanical properties. TEM analysis is shown in Figure 12.

Figure 12
TEM micrographs of fracture surfaces of CF- ETW containing (a) 5%, (b) 10%, (c) 15wt %, and (d) 20%.

7.2. Energy Dispersive X-Ray Analysis (EDAX)

The EDAX Spectrum of Carbon Reinforced with Electrical Toy Waste demonstrated distinct peaks for various polymers and elements. The PET peak showed the highest intensity, reaching approximately 18.9K counts around the 0.3 keV region, while the PVC peak is observed at about 10.5K counts near 1.4 keV. Peaks corresponding to PS and PC appear at lower intensities near the 5 keV and 2.3 keV ranges, respectively which is illustrated in Figure 13. A notable Cu peak is detected at approximately 4.1 keV, indicating the presence of metallic traces in the sample. The energy spectrum spans 0–6 keV, with significant intensities observed for PET and PVC.

Figure 13
EDAX spectrum of carbon reinforced with electronic toy waste.

7.3. X-ray diffraction (XRD)

The XRD Pattern of Carbon Reinforced with Electrical Toy Waste showed characteristic peaks of Cu for three samples: CF-0EPTW, CF-30EPTW, and CF-50EPTW. In CF-0EPTW, peaks are observed at (111) 44.50°, (200) 50.47°, and (220) 71.95°, while CF-30EPTW shows sharper peaks at (111) 42.47°, (200) 49.04°, and (220) 72.37° with increased intensity. For CF-50EPTW, peaks appear at (110) 35.42°, (111) 44.27°, (022) 66.49°, and (220) 75.06°, indicating structural variations with increasing toy waste content. Figure 14 displays the XRD analysis.

Figure 14
XRD pattern of carbon reinforced with electronic toy waste.

Therefore, microstructural analyses using TEM and XRD correlate directly with performance trends. Uniformly dispersed EPTW particles in CF-5EPTW and CF-10EPTW enhance load transfer and mechanical stability. Conversely, at CF-20EPTW, particle clustering disrupts matrix continuity, leading to stress concentration points and diminished strength. Such correlations highlight the critical role of microstructural integrity in composite performance. Overall, microstructural characterization using Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Analysis (EDAX) provides critical insights into the structural and compositional properties of materials at the nanoscale. TEM allows for the visualization of fine details such as grain boundaries, dislocation structures, and phase distributions, offering high-resolution images that elucidate the material’s internal morphology. EDAX, integrated with TEM, enables the precise elemental analysis of localized regions, revealing the distribution and concentration of elements within the sample. These techniques are invaluable for identifying material defects, confirming phase compositions, and evaluating the effects of processing conditions on microstructural features. The implications of such analysis extend to optimizing material properties, improving performance, and tailoring materials for specific applications, such as enhancing the mechanical, thermal, or electrical characteristics of composites, alloys, and nanomaterials.

8. CONCLUSIONS

In this study, various compositions of EPTW reinforced with carbon fiber (CF) were analyzed to evaluate their mechanical, thermal, and morphological properties.

1. 1. In mechanical testing, CF-0EPTW exhibited the highest tensile strength, Young’s modulus, elongation at break, and fracture toughness, making it the most balanced and strong composition. The compressive strength, modulus, and energy absorption also decrease progressively as CF content increases, with CF-0EPTW being the highest and CF-20EPTW the lowest in all metrics. Flexural and impact tests show similar trends, with CF-0EPTW demonstrating superior toughness and energy absorption compared to the other compositions.

2. 2. The thermal analysis showed that CF-0EPTW exhibited superior thermal stability, with a degradation onset at 290°C, compared to CF-20EPTW, which began to degrade at 270°C. This indicates better heat resistance and performance retention at elevated temperatures for CF-0EPTW. Additionally, CF-0EPTW demonstrated a higher specific heat capacity, contributing to its enhanced thermal properties.

3. 3. The comparative analysis of the experimental and RSM methods showed that RSM consistently yielded higher values, particularly for CF-20EPTW, where the experimental method gave 0.96 and RSM provided 0.99. Similarly, for CF-15EPTW, RSM reached 0.98 compared to 0.95 in the experimental method, highlighting RSM’s superior performance across the compositions.

4. 4. TEM analysis of CF-ETW composites revealed improved fiber-matrix bonding at 10% fiber content, with enhanced mechanical properties. At 20% fiber content, a denser fiber distribution led to higher mechanical performance, while higher stress concentrations were observed at 15% fiber content, suggesting partial fiber failure.

5. 5. EDAX and XRD results demonstrated significant peaks for PET and PVC, with the highest intensity observed for PET at approximately 18.9K counts. XRD analysis revealed sharper peaks and increased intensity for CF-30EPTW, indicating structural enhancement with increased toy waste content, particularly in the Cu phase.

6. 6. Using EPTW as a filler is economically viable compared to other sustainable materials. The low cost of sourcing discarded toys and the straightforward preparation process (cleaning, shredding, and sieving) reduces production costs. Moreover, EPTW-derived composites align with circular economy principles, enabling manufacturers to achieve cost savings while meeting regulatory requirements for waste management and sustainability.

7. 7. The utilization of EPTW offers significant environmental benefits beyond waste recycling. Lifecycle analysis reveals reduced carbon emissions, energy savings during material processing, and minimized landfill waste. Additionally, incorporating EPTW reduces dependency on virgin polymer production, indirectly conserving non-renewable resources and lowering environmental pollution from traditional manufacturing processes.

The implementation of EPTW-based composites in industrial applications faces challenges such as ensuring the consistent quality of e-waste-derived powders, addressing compatibility with various matrix materials, and managing the cost of required surface treatments or additives. Scalability concerns include the need for specialized recycling and processing infrastructure, regulatory compliance for hazardous materials, and optimizing energy efficiency in production. Overcoming these issues requires innovative solutions to streamline processes while maintaining sustainability and economic viability. Future research could focus on optimizing recycling techniques to improve the efficiency and cost-effectiveness of EPTW-based composites. Additionally, advancements in material compatibility and environmental impact assessments will be crucial for their widespread industrial adoption.

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Publication Dates

• Publication in this collection
  24 Mar 2025
• Date of issue
  2025

History

• Received
  17 Dec 2024
• Accepted
  20 Jan 2025