Preparation and Evaluation Recycling Waste Polymers Composites

2.1 Materials preparation

The Waste materials of tires compositions are shown in Table 1.

Table 1. shows the components of tires for cars and trucks

Figure 1, consists of two images marked A and B. Both images are intended to depict different aspects of PVC (Polyvinyl Chloride) materials. Image A shows waste of PVC pipes, before it undergoes processing for recycling or for use as a raw material in creating new products or for experimentation. These pipes are commonly used for various plumbing and drainage applications. Image B shows a close-up view of a surface with red spots marked in circles, described as the grain size of PVC after milling. This a microscopic view that shows the granularity of the PVC material. The circled areas indicate points of particular grains. Grain size can be an important factor in determining the physical properties of materials, such as their strength, durability, or suitability for certain applications.

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Figure 1. (a) Waste of PVC pipes, (b) Grain size of PVC

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Figure 2. (a) Steel waste in tire, (b) Grain size of tire

In this research, crushed waste tire with a granular size (0.185 mm) was used and it contains (13.8%) steel (shown in the Figure 2), that has a number of properties that make it perfectly suitable for use as a basic material in the manufacture of bumps: Light weight, low-pressure, free-draining, good thermal insulators durable, and low-price.

Crushed waste PVC pipe with a granular size (0.275 mm) was used in the manufacture of bumps due to its properties: Extremely resistant to chemicals, thermal and electrical insulators, very lightweight, and low cost.

Figure 2, contains two images marked A and B, illustrating aspects of tire waste and its characteristics. Image A displays a collection of steel fibers or filaments that have been extracted from tire waste. These steel elements are often part of the internal structure of tires, providing reinforcement and contributing to the overall durability and shape retention of the tire under the stress of use. This image shows the steel waste as it appears after being separated from the rubber and other tire components, which part of a recycling material. Image B seems to be a close-up view of a surface with small fragments scattered across it, some of which are circled in red, described as the grain size of tire. This shows the rubber granules that result from grinding down tire waste, which can be used for various applications such as playground surfaces, athletic tracks, or as an additive in new tire manufacturing. The red circles indicate specific particles being examined for size, grain size can affect the physical properties and suitability for reuse in different applications, these images in Figure 2 appear to demonstrate the components recovered from tire waste and the detailed examination of the rubber granules' size, contributing to understanding the recycling process or the potential uses of the recovered materials.

Silicon rubber used in this work is a liquid with a slightly heavy texture. Base material (liquid rubber) and hardener, where for every 100 g of silicon, 2.65 g of hardener is added to it. Often shortened to grinder, is one of power tools or machine tools used for grinding, it is a type of machining using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a small chip from the workpiece via shear deformation.

There are two methods for obtaining grains of polymeric waste materials:

-The method of freezing and then grinding into small parts,

-Grinding method by grinding wheel.

Where the grinding method was used in the preparation of the for the two materials tire and PVC.

Figure 3, features two images marked A and B, each displaying a different type of powder. Image A shows a white powder labeled as PVC, which stands for Polyvinyl Chloride. This type of plastic is known for its versatility and is used in a wide array of products from plumbing pipes to insulation for electrical wires. The white powder could be in the form of PVC resin, which is the base material for a lot of PVC products and is often processed further to produce various PVC goods. Image B displays a black powder "tire". This is likely to be ground rubber from used tires. Ground tire rubber is commonly recycled and used in various applications, such as in the creation of asphalt, artificial turf, or as an additive to new rubber products to improve certain properties or reduce costs.

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Figure 3. The powder (a) PVC, (b) Tire

Table 2 appears to show the varying weights of different materials (Tire or PVC, silicon rubber, and hardener) associated with different percentages of waste. The materials are measured in grams, and there are four distinct categories based on the percentage of waste (10%, 20%, 30%, and 40%).

Table 2. Weight of (Tire, PVC, Silicon rubber, and Hardener) with percentage of waste

The pattern in the data indicates that as the percentage of waste increases, the weight of tire or PVC also increases, whereas the weight of silicon rubber and hardener decreases. This indicates that the process described in the table is substituting tire or PVC for silicon rubber and hardener as the waste percentage increases where the proportion of tire or PVC is being increased relative to the other components at higher waste percentages.

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Figure 4. Shapes of samples

Figure 4 displays a lineup of cylindrical samples, each marked with a label that appears to indicate a number. These samples represent various mixtures or composites made from different materials, possibly including some of the materials mentioned in the earlier tables and figures, such as PVC or tire rubber. The different colors of the samples may be indicative of their composition, they include different proportions of materials or different types of additives. The black samples are typical of rubber composites, which are often black due to the addition of carbon black during processing to improve strength and durability. The white and other colored samples refer to the different fillers or the absence of carbon black.

2.2 Shore hardness test

Shore hardness test is a measure of the resistance a material has to indentation. There are different Shore hardness scales for measuring the hardness of different materials, such as soft rubbers, rigid plastics and super soft gels. Shore hardness, using either the Shore A or Shore D scale, is the preferred method for rubbers and thermoplastic elastomers – and is also commonly used for ‘softer’ plastics such as polyolefin, fluoropolymers, and vinyl's. The Shore A scale is used for ‘softer’ rubbers while the Shore D scale is commonly used for ‘harder’ ones. Hardness value is determined by the penetration of the Durometer indenter foot into the sample being tested, in this work used shore hardness type A.

2.3 Thermal conductivity coefficient test

Figure 5 illustrates the operation of the device used for measuring the thermal conductivity coefficient, a material property that indicates how efficiently a material conducts heat. The figure consists of two images, each highlighting different components of the measuring setup.

On the left side of the figure, an electronic device is shown, likely a power supply or a specialized instrument designed for thermal conductivity testing. It features various knobs and a digital display, allowing for precise adjustments and accurate measurements.

The right side of the figure depicts the practical application of the device, where it is connected to a sample using probes. Additionally, a vernier caliper is being used to measure the thickness of the sample, a crucial parameter in calculating thermal conductivity.

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Figure 5. The thermal conductivity coefficient measuring device

Thermal conductivity coefficient of the sample can be estimated by the equation:

$\begin{gathered}\text { Ksample }=k^{\prime} \frac{t\left(T_2-T_0\right)\left(T_1^{\prime}-T_2^{\prime}\right) A^{\prime}}{t^{\prime}\left(T_2^{\prime}-T_0^{\prime}\right)\left(T_1-T_2\right) A} \\ \mathrm{~K}^{\prime}=0.23 \frac{\mathrm{w}}{\mathrm{m}^2 \cdot{ }^{\circ} \mathrm{C}}, \mathrm{A}^{\prime}=\frac{\pi}{4}(\mathrm{~d})^2=\frac{\pi}{4}(25)^2, \\ \mathrm{~A}=\frac{\pi}{4}(\mathrm{~d})^2=\frac{\pi}{4}(35)^2 \\ \mathrm{~d}^{\prime}=25 \mathrm{~mm}, \mathrm{~d}=35 \mathrm{~mm}, \\ \mathrm{t}^{\prime}=6 \mathrm{~mm}, \mathrm{~T}_0^{\prime}=28^{\circ} \mathrm{C}, \mathrm{T}_1^{\prime}=100^{\circ} \mathrm{C}, \mathrm{T}_2^{\prime}=60^{\circ} \mathrm{C}\end{gathered}$

where, $\mathrm{K}=$ Thermal conductivity coefficient of the sample, $\mathrm{K}^{\prime}=$ Thermal conductivity coefficient of the standard material (Brian), $A^{\prime}=$ Area of the standard material (Brian), $\mathrm{d}^{\prime}=$ Diameter, f the standard material, $\mathrm{t}^{\prime}=$ thickness of the standard material, $\mathrm{T}_0^{\prime}=$ constant surface temperature of the standard material, $\mathrm{T}_1^{\prime}=$ first temperature of the standard material, $\mathrm{T}_2^{\prime}=$ second temperature of the standard material, $\mathrm{T}_0=$ $40^{\circ} \mathrm{C}$ constant surface temperature of the sample, $\mathrm{T}_1=$ first surface temperature of the sample, and $T_2=$ second surface temperature of the sample.

2.4 Compression test

A compressive test involves subjecting a material to a force applied from opposite sides, leading to its compression, crushing, or flattening. In this test, two plates cover the entire surface area of two opposite faces of the test specimen. These plates are positioned within a universal testing machine, which exerts a load on both faces, resulting in the flattening of the specimen. As the compressive forces are applied, the test specimen typically undergoes shortening and expansion perpendicular to the applied forces.

The study comprehensively analyzes the impact of waste percentages on the mechanical and thermal properties of three waste materials; Tire, PVC, and silicon rubber. Hardness increases significantly for Tire, from 14.56 at 10% waste to 34.94 at 40%, and for PVC, from 16.02 to 37.96 within the same range. Simultaneously, the Elastic Modulus for Tire climbs from 0.548987 MPa to 1.391695 MPa, and for PVC, it ascends from 0.595757 MPa to 1.563672 MPa, both at 40% waste. Conversely, compression resistance for both Tire and PVC demonstrates a decline with escalating waste percentages, indicating decreased resistance to compression. Thermal conductivity coefficient (K) unveils a noteworthy increase in Tire, ascending from 0.233 W/m.K to 0.317 W/m.K, while PVC exhibits a more intricate pattern, initially peaking at 0.29 W/m.K and subsequently dropping to 0.111 W/m.K at 40% waste.