Environment-friendly cyclic processing and recycling method of glass fibers and mobile phone back shell formed by glass fibers

Abstract

The invention discloses an environment-friendly cyclic processing and recycling method for glass fibers, which comprises the following steps: S1, material recycling and pretreatment: obtaining a glass fiber composite material from a disassembled material, and removing a resin coating through sorting, mechanical crushing and gradient chemical dissolution to obtain pure recycled glass fibers; s2, plate preparation: mixing the recycled glass fiber with a bio-based nylon material; and S21, a composite felt is prepared through an airflow-mechanical composite net forming technology, and then the lightweight glass fiber board is obtained through multi-section type hot press forming. Or S22, the recycled glass fibers and the PC + PMMA material subjected to closed-loop recycling are subjected to hot-pressing composite forming; s3, back cover forming: adopting a one-step mold pressing process, taking the plate obtained in the step S2 as a base material layer, and performing one-time hot melting compounding on the base material layer, a spraying-free decorative layer and a functional layer to form a mobile phone back cover blank, and the mobile phone back cover is a composite plate; and S4, appearance treatment is conducted, specifically, spraying-free plastic containing special-effect pigment is molten on the surface.

Description

Technical Field

[0001] This invention relates to the field of glass fiber recycling and processing methods, and in particular to an environmentally friendly recycling method for glass fiber and the resulting mobile phone back cover. Background Technology

[0002] Glass fiber is an inorganic non-metallic material that can replace metals and has excellent performance. It is prepared by drawing molten glass into fibers under the action of external force. It has the characteristics of high strength, high modulus and low elongation. It also has a series of properties such as corrosion resistance, good chemical stability, large specific surface area, no mold growth and non-flammability, and has been widely used in many fields.

[0003] With the deepening of the circular economy concept, the consumer electronics industry has placed higher demands on the environmental friendliness, recyclability, and carbon footprint of product materials. As an important exterior and structural component, the green transformation of materials and manufacturing processes is particularly crucial for mobile phone back covers. However, current mainstream technologies suffer from the following significant drawbacks: 1. Non-recyclable substrate and high carbon footprint: Currently widely used mobile phone back cover substrates, such as traditional thermosetting epoxy resin-based composite materials (including some glass fiber reinforced boards), are difficult to degrade and recycle at the end of their life cycle. These materials rely on fossil fuels, have high carbon emissions during production, and their non-recyclable nature leads to linear resource consumption ("mining-manufacturing-waste") and environmental pollution, which runs counter to the global green and low-carbon policies. 2. Severe contamination during the appearance manufacturing process: Traditional back cover decoration relies heavily on secondary processing techniques such as spraying, electroplating, and printing. These processes are not only complex and energy-intensive, but also use large amounts of inks and coatings containing volatile organic compounds (VOCs), causing environmental pollution and posing a threat to occupational health in the workplace; the increase in post-processing also means an increase in overall energy consumption and carbon emissions. 3. Insufficient material innovation and supply chain synergy: Improving a single material often fails to achieve optimal carbon reduction throughout its entire lifecycle. Existing technologies lack systematic solutions that extend from material sources (such as recycled materials and bio-based materials) to intermediate processes (such as low-energy molding) and end-of-life recycling (such as closed-loop recycling). Furthermore, cross-industry (such as aerospace and consumer electronics) material recycling and deep collaborative innovation across the supply chain (such as substrate suppliers and surface treatment companies) are insufficient, limiting the industrial application of groundbreaking environmental technologies. Summary of the Invention

[0004] The main objective of this invention is to propose an environmentally friendly recycling method for glass fiber, aiming to achieve the recycling and processing of glass fiber.

[0005] To achieve the above objectives, the present invention proposes the following steps: S1. Material recycling and pretreatment: Fiberglass composite materials are obtained from dismantled materials, and the resin coating is removed through sorting, mechanical crushing and gradient chemical dissolution to obtain pure recycled fiberglass. S2. Sheet preparation: The recycled glass fiber is mixed with bio-based nylon material; S21. Composite felt is made through airflow-mechanical composite web forming process, and then lightweight fiberglass board is obtained through multi-stage hot pressing. Alternatively, in step S22, the recycled fiberglass sheet and the closed-loop recycled PC+PMMA material are hot-pressed together to form a composite material. S3. Back cover molding: A one-step molding process is adopted, in which the board obtained in step S2 is used as the base material layer, and is hot-melted and composited with the paint-free decorative layer and the functional layer in one step to form a mobile phone back cover blank. The mobile phone back cover is a composite board. S4. Appearance treatment: For the mobile phone back cover blank obtained in step S3, a paint-free plastic containing special effect pigments is melted and molded onto the surface through an injection molding process integrating nano-imprinting technology (it can be done by transfer printing or injection molding, wherein the injection molding method can inject molten plastic color particles at a predetermined position).

[0006] The core objective is to reduce weight and lower the carbon footprint; The above steps achieved the following technical effects: 1. Bio-based fiberglass sheets: lightweight, tough, and low-consumption; Material Composition: Recycled aerospace fiberglass and Yipin Bio-based Nylon 56 yarn are processed into composite felt using a special process. Yipin Bio's Nylon 56 is USDA certified, with a bio-based content of 48%. This bio-based nylon is derived from renewable biomass, replacing petroleum-based epoxy resin and reducing the consumption of non-renewable resources at the source.

[0007] Lightweighting mechanism: Utilizing the porous and fluffy structure of felt, a lightweight sheet material with lower density (down to below 1.5 g / cm³) is formed during hot pressing while retaining high strength. The combination of the high strength of glass fiber and the toughness of nylon gives the sheet material good impact resistance while being lightweight.

[0008] Carbon Reduction Contribution: The production process of bio-based materials helps reduce carbon emissions. For example, the production of bio-based polyamide can reduce carbon emissions by up to 50% per unit compared to traditional petroleum-based nylon. Combining this with the recycling of aerospace fiberglass further reduces carbon emissions at the raw material stage. The carbon reduction effect is even more significant when bio-based materials are produced using renewable energy sources.

[0009] 2. Closed-loop composite panels: cyclical energy saving; Material composition: The material is a composite sheet made of PC (polycarbonate) and PMMA (polymethyl methacrylate). PMMA provides high hardness and wear resistance, while PC contributes toughness.

[0010] Closed-loop recycling: PC+PMMA scraps and waste boards generated during the production process can be recycled and reprocessed on-site for use in the production of new composite boards. This closed-loop recycling system can significantly improve material utilization (up to 95% or more) and reduce carbon emissions from new material input and waste disposal.

[0011] Carbon reduction and lightweighting: PC / PMMA composite sheets have a density advantage over many metal materials. Closed-loop recycling further reduces the carbon footprint over the entire lifecycle. For example, Covestro's post-consumer recycled (PCR) polycarbonate materials reduce carbon emissions by approximately 30% compared to virgin materials.

[0012] 3. Integrated and stain-reducing design of the decorative layer; The key innovation in the decorative layer lies in reducing energy consumption and pollution in subsequent processing steps.

[0013] No-coating process: Reduces pollution and saves time; By using paint-free plastics (such as masterbatches containing specific effect pigments) and through technologies such as nanoimprinting, colors and textures (such as flow lines and spots) are integrally formed with the back cover substrate during injection molding or imprinting. This directly replaces traditional secondary processing processes such as spraying and electroplating.

[0014] Environmental benefits: It fundamentally avoids the use of paint and the emission of volatile organic compounds (VOCs) in traditional spraying processes, reducing environmental pollution. For example, the shell of Huawei 5G CPE Pro uses a paint-free material, which has the advantages of being green and environmentally friendly, forming in one step without spraying, and shortening the production cycle.

[0015] Carbon reduction contribution: It simplifies the production process and reduces energy consumption and emissions caused by multiple processing steps. The paint-free process also avoids carbon emissions that may be generated during the painting process and the environmental burden of subsequent treatment. Attached Figure Description

[0016] Figure 1 A schematic diagram of the morphology of the material being processed; Figure 2 A diagram illustrating the fabrication process for a mobile phone back cover; Figure 3 This is a schematic diagram of the phone's back cover. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, top, bottom, inside, outside, vertical, horizontal, longitudinal, counterclockwise, clockwise, circumferential, radial, axial, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0019] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0020] like Figures 1 to 3 As shown, an environmentally friendly recycling method for glass fiber is characterized by comprising the following steps: S1. Material recycling and pretreatment: Fiberglass composite materials are obtained from dismantled materials, and the resin coating is removed through sorting, mechanical crushing and gradient chemical dissolution to obtain pure recycled fiberglass. S2. Sheet preparation: The recycled glass fiber and bio-based nylon material are melt-mixed and molded into thermoplastic glass fiber; S21. Composite felt is made through airflow-mechanical composite web forming process, and then lightweight fiberglass board is obtained through multi-stage hot pressing. Alternatively, in S22, the recycled fiberglass sheet and the closed-loop recycled PC+PMMA material (where both materials are existing technologies, i.e., mixed and then processed) are hot-pressed together to form a composite material. S3. Back cover molding: A one-step molding process is adopted, in which the board obtained in step S2 is used as the base material layer, and is hot-melted and composited with the paint-free decorative layer and the functional layer in one step to form a mobile phone back cover blank. The mobile phone back cover is a composite board. S4. Appearance processing: The mobile phone back cover blank obtained in step S3 is processed by injection molding with nano-imprinting technology to melt and mold paint-free plastic containing special effect pigments onto the surface (either by transfer printing or injection molding, wherein the injection molding method can inject molten plastic color particles into a predetermined position and then solidify after the predetermined flow molding) to form a preset appearance texture.

[0021] Specifically, in S1: aerospace fiberglass materials are recycled and pretreated; S11. Sorting and classification of recycled aviation fiberglass materials: Before mechanical crushing, an automatic sorting process based on near-infrared spectroscopy or X-ray fluorescence spectroscopy is added to accurately classify aviation waste according to resin type (such as epoxy resin, polyurethane) and fiberglass fabric type, avoiding cross-contamination between different materials and ensuring the targeted and efficient chemical dissolution of subsequent materials.

[0022] S12, gradient chemical dissolution: A stepwise, low-concentration, environmentally friendly solvent (such as a mild alkanolamine solution) is used for dissolution at specific temperatures and pressures, and dissolution parameters are dynamically adjusted by monitoring the solution viscosity and composition in real time. This minimizes damage to the glass fiber itself, preserving its original length and strength.

[0023] S13, Fiber purification and surface activation: After dissolution, the pure glass fiber is cleaned in multiple stages until neutral, and then the fiber surface is activated by low-temperature plasma treatment technology. This improvement can significantly enhance the interfacial bonding force between the fiber and the subsequent bio-based nylon matrix and reduce the risk of interlayer separation.

[0024] S14. Quality Control Points and Effects: Control points: Sorting accuracy > 98%; fiber damage rate < 5%; fiber surface energy improvement ≥ 20%.

[0025] Results: Ensuring the uniformity and high performance of recycled fiberglass materials from the source lays the foundation for the preparation of high-strength boards and meets the requirements for traceability and quality of recycled materials in GRS certification.

[0026] Specifically, in S2: preparation of glass fiber filaments and sheets; S21. Mixing Uniformity Control: During the preparation of the composite felt, a combination of air-flow web formation and mechanical web laying is employed to ensure uniform mixing of recycled glass fiber chopped strands and bio-based nylon yarn in three-dimensional space. This can be understood as a hybrid weaving process (avoiding the fiber damage caused by secondary heat processing required in existing hot-melt structures). An online visual inspection system is introduced to monitor the felt's basis weight and fiber distribution uniformity in real time, automatically adjusting the web laying parameters accordingly.

[0027] S22. Hot pressing process: adopts a multi-stage precise temperature and pressure control step of "preheating-pressurizing-holding-cooling"; Introducing ultrasonic vibration during the hot pressing process promotes resin flow and fiber impregnation, reduces internal bubbles and pores, thereby improving the density and mechanical properties of the board. S23. Closed-loop recycled material blending ratio control: For PC+PMMA composite sheets, a dynamic viscosity monitoring system was developed to monitor the mixed viscosity of recycled and virgin materials in the molten state online, thereby accurately controlling the blending ratio (for example, ensuring that the proportion of recycled material is stable between 30% and 50%) and guaranteeing batch-to-batch performance stability.

[0028] S24. Quality control points and effects: Control points: Felt weight deviation <±3%; Board porosity <1%; Recycled material ratio control accuracy ±2%.

[0029] Results: Significantly improves the consistency of mechanical properties and lightweighting of the board material, ensures stable compliance with bio-based carbon content standards (refer to the Beta lab report: bio-based carbon content reaches 48%), and enables reliable closed-loop production. The board material is lightweight (density ≤1.5g / cm³) and has excellent dielectric properties.

[0030] Specifically, in S3: multi-layer board composite pressing and mobile phone back cover molding; S31. Interlayer alignment and tension control: Before the one-step pressing process, a high-precision CCD vision positioning system is used to ensure the precise alignment of the substrate layer, decorative layer, and functional layers (such as the NVCM ink layer and the compression-resistant layer). For the roll-to-die process, a constant tension control system is introduced to prevent the material from being stretched or wrinkled during transport.

[0031] S32. In-mold pressure and temperature field monitoring: Multiple pressure and temperature sensors are embedded in key locations of the mold to monitor the pressure distribution and temperature field within the mold cavity in real time. Algorithms dynamically adjust the pressure output of different hydraulic cylinders to ensure uniform heating and pressure distribution throughout the entire back cover, especially at the edges and uneven structures, preventing defects such as material shortages and warping.

[0032] S33. Online Defect Detection: Immediately after demolding, a 3D laser scanner or high-resolution industrial camera is set up to quickly detect the dimensional tolerances, surface flatness, and presence of obvious defects of the back cover, enabling immediate sorting of defective products.

[0033] S34. Quality Control Points and Effects: Control points: interlayer alignment accuracy ±0.05mm; in-mold temperature difference <5°C; first-pass yield >99%.

[0034] Results: Significantly reduces processing steps and energy consumption (by 25%), while ensuring interlayer bonding strength and product dimensional accuracy through precise control; impact resistance is superior to traditional back covers. Closed-loop recycling achieves a material utilization rate of over 95%.

[0035] Specifically, in S4: paint-free melt-forming appearance. S41. Pigment Particle Dispersion and Metering: A twin-screw extruder is used for the blending and granulation of paint-free masterbatch (containing flow and spot effect pigments), and the screw configuration and shear rate are optimized to ensure that the pigment particles achieve an ideal dispersion state in the plastic matrix (neither excessively broken down and losing their effect, nor agglomerating). A loss-in-weight weighing scale is used for precise feeding to ensure batch stability of color and texture.

[0036] S42. Anti-sticking and maintenance of nanoimprint molds: A layer of diamond-like carbon (DLC) ultra-hard, wear-resistant and low surface energy coating is deposited on the surface of the nanoimprint mold to effectively prevent molten material from sticking to the mold, extend the service life of the mold, and maintain the transfer accuracy of micro-nano textures.

[0037] S43. Texture Effect Prediction and Optimization: Using computational fluid dynamics (CFD) software to simulate the flow behavior of pigment particles during injection molding / imprinting, predicting the final molded flow pattern or spot pattern, thereby optimizing process parameters such as mold flow channel design and injection speed, and realizing the pre-control and proactive design of the final appearance effect.

[0038] S44. Quality Control Points and Effects: Control points: Pigment dispersion uniformity CV value <10%; texture transfer rate >95%; VOC emission test meets the standard (≤50g / ㎡).

[0039] Results: Successfully avoids VOC pollution from traditional spraying, fully complying with LCA's full-cycle carbon reduction requirements. Precise control of texture achieves a natural, unique, and high-end appearance, enhancing product added value and market competitiveness.

[0040] Specifically, in step S1, the sorting is performed using near-infrared spectroscopy or X-ray fluorescence spectroscopy. The gradient chemical dissolution uses environmentally friendly alcohol amine solvents, supplemented by low-temperature plasma technology to perform surface activation treatment on the dissolved glass fibers; In step S2, During the web forming and hot pressing processes, an online visual inspection system is used to monitor the uniformity of the felt, and ultrasonic vibration is used to assist hot pressing to reduce the porosity of the board. For PC+PMMA composite boards, an online viscosity monitoring system is used to precisely control the blending ratio of closed-loop recycled materials. In step S3, The one-step molding process employs a high-precision CCD vision system for interlayer alignment and embeds multiple sensors within the mold to monitor the pressure and temperature fields in real time. Dynamic pressure adjustment ensures uniform heating and pressure distribution. Online 3D scanning and inspection are performed immediately after demolding. In step S4, a coating-free masterbatch is prepared using a twin-screw extruder with an optimized screw configuration, and a loss-in-weight weighing scale is used for feeding. The surface of the nanoimprint mold is coated with a diamond-like carbon coating; and the process parameters are optimized based on CFD simulation to control the texture effect.

[0041] Specifically, the formula for controlling the density and mechanical properties of the sheet material is: ρ = k * (P / T) * (1 / V_f) + C; ρ: Target board density (g / cm³); P: Hot-pressing pressure (MPa); T: Hot pressing temperature (°C); V_f: Fiber volume content (%); k, C: Material constants.

[0042] Based on the fitting of experimental data, it was found that for the recycled glass fiber / bio-based nylon system, k≈0.15, C≈0.8.

[0043] This allowed for control over the proportion of glass fiber.

[0044] Specifically, the bio-based nylon is derived from bio-based nylon 56 yarn, and its bio-based carbon content is not less than 48%.

[0045] Specifically, the substrate of the back cover contains no less than 30% recycled glass fiber material, and the overall density is no greater than 1.5 g / cm³.

[0046] The algorithm and adjustment formula in this application are existing technologies. By combining various existing technologies, energy-saving and environmentally friendly glass fiber material recycling and utilization can be achieved, which improves green environmental protection. In particular, for some regions with production requirements, such as plastic materials that must reach a certain percentage of environmentally friendly recycled materials, it is beneficial for product entry and thus improves market competitiveness.

[0047] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An environmentally friendly method for the recycling and processing of glass fiber, characterized in that, Includes the following steps: S1. Material recycling and pretreatment: Fiberglass composite materials are obtained from dismantled materials, and the resin coating is removed through sorting, mechanical crushing and gradient chemical dissolution to obtain pure recycled fiberglass. S2. Sheet preparation: The recycled glass fiber and bio-based nylon material are melt-mixed and molded into thermoplastic glass fiber; S21. Composite felt is made through airflow-mechanical composite web forming process, and then lightweight fiberglass board is obtained through multi-stage hot pressing. Alternatively, in step S22, the recycled fiberglass sheet and the closed-loop recycled PC+PMMA material are hot-pressed together to form a composite material. S3. Back cover molding: A one-step molding process is adopted, in which the board obtained in step S2 is used as the base material layer, and is hot-melted and composited with the paint-free decorative layer and the functional layer in one step to form a mobile phone back cover blank. The mobile phone back cover is a composite board. S4. Appearance processing: The mobile phone back cover blank obtained in step S3 is subjected to injection molding process with nano-imprinting technology, in which paint-free plastic containing special effect pigments is melted and molded onto the surface to form a preset appearance texture.

2. The environmentally friendly recycling method for glass fiber as described in claim 1, characterized in that, In S1: Recycle aerospace fiberglass materials and perform pretreatment; S11. Sorting and classification of recycled aviation fiberglass materials: Before mechanical crushing, an automatic sorting step based on near-infrared spectroscopy or X-ray fluorescence spectroscopy is added, according to resin type; S12, gradient chemical dissolution: The solution is dissolved using a stepwise, low-concentration, environmentally friendly solvent at specific temperatures and pressures, and the dissolution parameters are dynamically adjusted by real-time monitoring of the solution viscosity and composition. S13, Fiber purification and surface activation: After dissolution, the pure glass fiber is cleaned in multiple stages until it is neutral, and then the fiber surface is activated by low-temperature plasma treatment technology.

3. The environmentally friendly recycling method for glass fiber as described in claim 1, characterized in that, In S2: Preparation of glass fiber filaments and boards; S21. Mixing uniformity control: When preparing composite felt, a process combining airflow web formation and mechanical web laying is adopted to ensure that recycled glass fiber short chopped fibers and bio-based nylon yarn are uniformly mixed in three-dimensional space, which can be understood as a mixed weaving process. S22. Hot pressing process: adopts a multi-stage precise temperature and pressure control step of "preheating-pressurizing-holding-cooling"; Introducing ultrasonic vibration during hot pressing helps to promote resin flow and fiber impregnation, and reduces internal bubbles and pores. S23. Closed-loop control of the blending ratio of recycled materials.

4. The environmentally friendly recycling method for glass fiber as described in claim 1, characterized in that, In S3: Multi-layer composite pressing and mobile phone back cover molding; S31. Interlayer alignment and tension control: Before the one-step pressing process, a high-precision CCD vision positioning system is used to ensure the precise alignment of the substrate layer, decorative layer, and functional layer. S32. Monitoring of intramold pressure and temperature field: Multiple pressure and temperature sensors are embedded in key locations of the mold to monitor the pressure distribution and temperature field within the mold cavity in real time. By dynamically adjusting the pressure output of different hydraulic cylinders, it is ensured that the entire back cover, especially the edges and concave and convex structures, is heated and pressured evenly, avoiding defects such as material shortage and warping.

5. The environmentally friendly recycling method for glass fiber as described in claim 1, characterized in that, In S4: Spray-free melt-forming appearance S41. Pigment particle dispersion and metering: A twin-screw extruder is used for the blending and granulation of the paint-free masterbatch, and the screw configuration and shear rate are optimized to ensure that the pigment particles achieve an ideal dispersion state in the plastic matrix. S42. Anti-sticking and maintenance of nanoimprint molds: A layer of diamond-like carbon ultra-hard wear-resistant and low surface energy coating is deposited on the surface of the nanoimprint mold to effectively prevent molten material from sticking to the mold, extend the service life of the mold, and maintain the transfer accuracy of micro-nano textures. S43. Texture Effect Prediction and Optimization: Using computational fluid dynamics software to simulate the flow behavior of pigment particles during injection molding / imprinting, predicting the final flow pattern or spot pattern.

6. The environmentally friendly recycling method for glass fiber as described in claim 1, characterized in that, In step S1, the sorting is performed using near-infrared spectroscopy or X-ray fluorescence spectroscopy. The gradient chemical dissolution uses environmentally friendly alcohol amine solvents, supplemented by low-temperature plasma technology to perform surface activation treatment on the dissolved glass fibers; In step S2, During the web forming and hot pressing processes, an online visual inspection system is used to monitor the uniformity of the felt, and ultrasonic vibration is used to assist hot pressing to reduce the porosity of the board. For PC+PMMA composite boards, an online viscosity monitoring system is used to precisely control the blending ratio of closed-loop recycled materials. In step S3, The one-step molding process employs a high-precision CCD vision system for interlayer alignment and embeds multiple sensors within the mold to monitor the pressure and temperature fields in real time. Dynamic pressure adjustment ensures uniform heating and pressure distribution. Online 3D scanning and inspection are performed immediately after demolding. In step S4, a coating-free masterbatch is prepared using a twin-screw extruder with an optimized screw configuration, and a loss-in-weight weighing scale is used for feeding. The surface of the nanoimprint mold is coated with a diamond-like carbon coating; and the process parameters are optimized based on CFD simulation to control the texture effect.

7. The environmentally friendly recycling method for glass fiber as described in claim 1, characterized in that, The formula for controlling the density and mechanical properties of sheet metal is: ρ = k * (P / T) * (1 / V_f) + C; ρ: Target board density (g / cm³); P: Hot-pressing pressure (MPa); T: Hot pressing temperature (°C); V_f: Fiber volume content (%); k, C: Material constants.

8. The environmentally friendly recycling method for glass fiber according to any one of claims 1 to 5, characterized in that, The bio-based nylon is derived from bio-based nylon 56 yarn, and its bio-based carbon content is not less than 48%.

9. A mobile phone back cover made by an environmentally friendly recycling method for glass fiber according to any one of claims 1 to 6, characterized in that, The substrate of the back cover contains no less than 30% recycled glass fiber material, and the overall density is no greater than 1.5 g / cm³.

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