(629h) Sustainable Use of Recycled Materials for the Cleaner Production of Value-Added Products

In the study, sustainable and low-cost products such as adhesive materials and composite products are prepared by using recycled materials such as post-consumer expanded polystyrene (EPS) and biomass material. To prepare the adhesive product, the EPS was dissolved in suitable solvents such as n-butyl acetate (n-BA), tetrahydrofuran (THF), methyl ethyl ketone (MEK), m-xylene and gasoline, and the corresponding adhesives are coded as A-B, A-T, A-M, A-X and A-G, respectively. Various physico-chemical properties such as solubility, viscosity, adhesive (shear) strength etc. of the in-house prepared adhesives are estimated. The cost-effective and eco-friendly composites are also prepared in the study using EPS and biomass (saw dust as a model compound), and the prepared composites are characterized as per the standard procedures. From the results, it is observed that MEK solvent offered maximum solubility of the EPS among the chosen solvents. The composite study revealed that post-consumer EPS and biomass materials have good candidate to the preparation of wood-plastic composites. We believe that the present study will be useful to the business visionaries / analysts to design a suitable process for mitigating the global problems associated with waste generation and its proper management.

Keywords: Recycled materials; Expanded polystyrene; Biomass; Adhesive; Composite

1. Introduction

In recent years, sustainable management has become the focus of research throughout the world. It includes, among many other things, the development of eco-friendly processes and products. The present research is undertaken on the same line, that is, to prepare eco-friendly and cost-effective products such as adhesive material and composites from the post-consumer (waste) expanded polystyrene (EPS) and biomass. The recycling of waste EPS will reduce the environmental pollution caused by its disposal and will lead to cleaner and greener earth; and also will offer value-added products for various possible applications.

From the thorough literature regarding the utilization of waste EPS, it is observed that a few studies are available on the development of an adhesive / glue material and wood-plastic composites from waste EPS and biomass for various applications. In recent years, the use of wood-plastic composites (WPC) has been lengthened into various applications which includes interior decoration, door and window making, flooring, automotive interior design etc. WPC materials can be prepared from various types of natural fibers and thermoplastics. To the best of our knowledge, from the literature, it is evident that the detailed studies pertaining to the preparations of wood-plastic composites from waste EPS using biomass is scares. Therefore, the objective of the present study is to prepare the sustainable materials out of recycled materials.

2. Preparation and characterization of adhesive product from recycled EPS

The adhesive product is prepared by dissolving the EPS in chosen solvents. Around 30 g of solvent is taken into a 100 mL conical flask and known quantity of EPS is added gradually into it under stirring condition. The addition of EPS is stopped when no more EPS dissolves in the solvent. The in-house prepared adhesives using EPS and different solvents were ascribed with different codes as mentioned in Table 1. The prepared adhesives are used to measure various properties, such as solubility, viscosity, adhesive strength etc. The solubility and viscosity (measured with Brookefield rheometer) data of the EPS adhesive are given in Table 1.

To find the shear/adhesive strength of the in-house prepared adhesives, shear strength test is carried out using a universal testing machine (UTM) equipped with 100 kN load cell. ASTM D5868 method is adopted to determine the adhesive strength of the adhesive products and wood material is used as substrate. To prepare the specimen for the shear test, the substrate material is cut into rectangular (101.6 mm length × 25.4 mm width) shaped structure and then two such structures were fixed in a single lap joint fashion with the prepared adhesives for a fixed overlap length. The specimen is kept under 5 kg load for a duration of 24 hrs to enhance the interaction between the adhesive and the substrate before performing the shear strength test. The test is performed by pulling the specimen at a speed of 2.0 mm/min under auto-trigger mode until the specimen breaks. In most cases, three numbers of specimen samples were prepared for the same experiment and the average value of the analysis results. The obtained results (shear strength values) of the adhesives are shown in Figure 1. The result shows that the shear strength of A-M adhesive is maximum among the four in-house developed adhesives. The order of shear strengths of the tested adhesives is A-X < A-B < A-T < A-M. The average value of the shear strength analysis results of A-X, A-B, A-T and A-M is 1081, 1372, 3791 and 4407 kPa, respectively.

3. Preparation and characterization of wood-plastic composites from recycled EPS and biomass

In the study, the EPS and sawdust materials are used to prepare the wood-plastic composites. The sawdust (size ≤500 µ) and EPS waste (size ≤1400 µ) were mixed at different ratios, and the EPS-sawdust mixture is used to make the composite. Compression moulding process is used to prepare the composites. The moulding temperature is maintained at 160 ±5 °C. The area of the prepared composite sheet is 225 cm² (15 cm × 15 cm). The prepared composite was used to estimate various physico-mechanical properties such as tensile strength, tensile modulus, %elongation, flexural strength, compression strength and water absorption etc. The images of prepared composites are shown in Figure 2. The effect of EPS loading on the properties of the in-house prepared wood-plastic composites are given in Table 2.

The data shows that the properties of the composites increased with the increase of EPS loading. Around 75% increase in tensile strength and %elongation is obtained with the increase in EPS loading from 40-50% by weight. It is also observed that around 60% improvement in tensile modulus; and around 50% improvement in flexural strength are obtained with the increase of EPS loading under present experimental conditions. It is also observed from the data that the water absorption values decreased with the increase of EPS loading.

4. Conclusions

In the study, sustainable and low-cost products such as adhesive materials and composite products are prepared by using recycled materials such as post-consumer expanded polystyrene (EPS) and biomass material. To prepare the adhesive product, the EPS was dissolved in suitable solvents such as n-butyl acetate (n-BA), tetrahydrofuran (THF), methyl ethyl ketone (MEK), m-xylene and gasoline, and the corresponding adhesives are coded as A-B, A-T, A-M, A-X and A-G, respectively. Various physico-chemical properties such as solubility, viscosity, adhesive (shear) strength etc. of the in-house prepared adhesives are estimated. The cost-effective and eco-friendly composites are also prepared in the study using EPS and biomass (saw dust as a model compound), and the prepared composites are characterized as per the standard procedures. From the results, it is observed that MEK solvent offered maximum solubility of the EPS among the chosen solvents. The composite study revealed that post-consumer EPS and biomass materials have good candidate to the preparation of wood-plastic composites. More study is required to explore more sustainable applications from the considered recycled materials in the present study.

Acknowledgments

The authors express their gratitude to B V Raju Institute of Technology (BVRIT)-Narsapur, Medak District, Telangana, India for providing the necessary support for the present study.

References

Abdulkareem SA, Raji SA, Adeniyi AG, (2017). Development of particleboard from waste styrofoam and sawdust. Nigerian Journal of Technological Development, 14 (1): 18-22.

Appala Naidu U, Srikanta D, Bhanu Radhika G, (2020). Scientific and engineering aspects of potential applications of post-consumer (waste) expanded polystyrene: A review. Process Safety and Environmental Protection, 137:140-148.