Recycled Polymers

Characterization of recycled plastic materials of municipal solid waste in Hafr Al-Batin, Saudi Arabia, for industrial applications

 

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The recycling of plastic products after their life cycle can contribute a great deal to the reduction of environmental and economic impacts. To produce high-quality recycling products a proper characterization of waste polymers is required. The project aims to give new life (recycle or reprocess) post-consumer mixed plastics waste into a new product. The initial objective is to characterize the recycled plastics and manage them by making chips and granules through the extrusion process for industrial applications.

 

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The recycling of polymeric materials is a global orientation since the increased risks of wastes on the environment through decompose waste. The decomposition of waste can lead to the leakage of toxins into groundwater, surface water, and the soil for cultivation. Moreover, soil pollution is affecting the cycle of food as well as pollution of drinking water and thus risk to the safety of the people. The Municipal of Hafr Al Batin collects tons of solid waste every day and a reasonable amount of this waste is plastic materials. The environmental impact of these plastic materials is much greater than the other waste. This material i.e. 'thin' polythene, when discarded after use (20 and less micron thickness), will remain in the soil for at least 100 years and creates numerous types of problems. According to world surveys by every ten years, plastic consumption increases by three times. This poses a great challenge as well as a threat to the environment of the earth. An appropriate methodology for recycling plastic and a proper characterization for industrial applications can reduce the threat to the environment. In this present research, recycled plastic will be characterized as for the requirement of industrial applications. The aim of recycling the plastics is the proper utilization of the waste, to preserve the planet, safety issue of human, and the formation of a clean environment which will be free of contaminants. Otherwise, all these plastics could cause damage to the beauty of mother earth, pollute the environment, and the whole society. Thus, this project could be reasonably justifiable as a very important and environmentally viable project.

 

 

Polymer recycling has become a high priority from an environmental, economical, and legislative point of view. The numbers are quite impressive: just one ton of recycled plastic can save up to 2,604 liters of crude oil, reduce energy consumption by 80–90% compared to the production of virgin plastics and help to avoid 22 cubic meters of landfill. The potential of polymer recycling is thus enormous. On average less than half of plastics waste were recovered every year. Most of the plastic waste occurs in the field of packaging while the electronics sector and the automotive industry are growing producers of post-consumer plastics waste with rather poor recycling rates of approximately less than 10%.

 

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The step by step objectives will be as follows:

 

a). Collecting samples of waste plastic will be shredded in our lab.

b). The shredded plastic will be characterized and classified according to its physical, optical, thermal, and mechanical properties.

c). The classified plastic will be further process by extrusion process in our lab for industrial applications.

 

Experimental Design and Research Methodology:

a) Detection of the recycled polymer type and impurities.

b) Use of thermogravimetric analysis for additional insight

c) Sorting of recycled polymer-based on mechanical properties for high-quality industrial applications.

d) Sorting of recycled polymer-based on the molecular structure using Raman Spectroscopy.

e) Management of recycled polymer by making chips and granules through the extrusion process for industrial applications.

 

a) Detection of the recycled polymer type and impurities.

Plastic waste can be mainly classified as (1) Municipal Waste (2) Industrial Waste Plastic wastes represent a considerable part of municipal wastes, while huge amounts of plastic waste arise as a by-product or faulty product in industry and agriculture. Of the total plastic waste, over 78 wt% of this total corresponds to thermoplastics and the remaining to thermosets. The delivered polymer waste stream contained a mixture of different colored re-granulates. Differential scanning calorimetry measurements will be carried out with a heating and cooling rate of 10oC/min in an N2 atmosphere to verify the nature of the polymer type. A software Identify feature will be used to compare the measurement data with the standard database, which stores individual measurement curves, literature data, and statistical classes of polymers and other materials. A comparison will be made based on glass transition temperature, melting temperature, and recrystallization effects, and the similarity of the re-granule will be identified.

 

Additionally, differently colored granules will be also analyzed. The impurities of the granule will be identified by comparing the melting, crystallization, recrystallization, and re-melting curve. The source of contamination in the re-granulate can be identified by the DSC curve analysis. The nature of the impurities and their quantitative amount will be identified.

 

b) Use of thermogravimetric analysis for additional insight

For confirmation and distinction between different polymer types, a second method will be applied. TGA measurement and evaluation will be done by the unique Auto Evaluation software feature followed by the identification of the components. Identify Differential Scanning Calorimetry (DSC) is a fast, reliable, and easy way to control the quality of recycled plastic materials in the manufacturing industry. The unique features of the Proteus® software additionally support a cost-efficient quality control process by automatically detecting and identifying impurities. With this method, the Identify software feature can also be used to detect and identify the different polymer types using TGA curves or using a combined TGA and DSC database search.

 

c) Sorting of recycled polymer based on mechanical properties for high-quality industrial applications.

With the development of science and technology, the requirements on the mechanical properties of new materials were increasing, polymer materials become one kind of important material type which has been widely used in the current human social activity. Due to its high properties such as strength, elasticity, and toughness, polymeric materials with high mechanical properties are now applied for the household item and sports. The recycled polymer will be tested mechanically for sorting as being "strong" and "tough" or even "ductile". Strength, toughness, and ductility are all mechanical properties that can be well characterized for high-quality industrial applications.

Mechanical properties were tested by the Universal Tester equipped with computer control, data acquisition, and data analysis system. Tensile tests will be conducted at a crosshead speed of 5 mm/min with a data acquisition rate of 10 points/s as described earlier1. A minimum of five specimens per sample will be tested and the data averaged will be used to calculate yield stress, yield strain, and modulus. Young’s modulus will be calculated from the slope of the least square linear fit of the steepest linear region of the load-displacement data.

 

d) Sorting of recycled polymer based on the molecular structure using Raman Spectroscopy.

Similar to near-infrared (NIR) spectroscopy, Raman spectroscopy can be applied to identify polymers based on their molecular structure2. It makes use of the inelastic (Raman) scattering of monochromatic light from a laser source in the visible, NIR, or near-ultraviolet range3. As an advantage over conventional NIR spectroscopy, H2O and CO2 in the air or on the sample surface cause less negative effects and Raman spectra of polymers exhibit narrow-band peaks. The Raman Spectroscopy analysis will give more experimental evidence of sorting polymer type. 

 

e) Management of recycled polymer by making chips and granules through the extrusion process for industrial applications.

Currently, we are fabricating the extrusion machine in our lab for making chips and granules of characterized plastics. Different shapes with the required dimension of chips and granules will be made for the requirement of high-quality industrial applications.

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6. Expected Results and their Utilization:

The manufacture of plastic lumber exists almost solely because of recycling polymers. The use of recycled alternatives to virgin plastic ensures that the product is more commercially competitive for industrial applications. Plastic lumber is typically made from recycled PE that may contain other plastics and/or fillers. Commingled plastics used with PE may include PVC, PS, PP, PET, and other materials. Fillers used in these systems may include glass fibers, PS fibers, or cellulosic fillers such as wood fibers. The principal use of plastic lumber is to replace wood in areas where weathering is an issue such as in decking, road barriers, or railroad ties.

From all of the above discussion, it is clear that the plastic recycling project would be highly justified from both a financial and an economic point of view. Besides, from an environmental point of view, the project is highly viable by emphasizing that this type of project should be focused more on social and environmental impacts with the financial returns.

 

List of References:

            (1)        Mamun, A.; Mahmood, R. Journal of Polymer Science Series A 2020, 62, 624.

            (2)        Tsuchida, A.; Kawazumi, H.; Kazuyoshi, A.; Yasuo, T. In SENSORS, 2009 IEEE 2009, p 1473.

           (3)        Merrington, A. In Applied Plastics Engineering Handbook; Kutz, M., Ed.; William Andrew Publishing: Oxford, 2011, p 177.

            (4)        Mamun, A. J. Polym. Sci. 2020, 58, 3283.

            (5)        Mamun, A. Polymer Engineering & Science 2020, 60, 2702.