Preparation of adhesive from polymer waste and its property enhancement (2021)

Introduction: In recent years, sustainable management has become the focus of research throughout the world. It includes, among many other things, the development of environment-friendly processes and products. The present research was undertaken on the same line, that is, to prepare an environment-friendly and cost-effective adhesive material from the post-consumer (waste) expanded polystyrene (PCEPS). The recycling of PCEPS 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. For the sustainable management, PCEPS material can be recycled to yield value added chemicals and fuels (1), construction materials, value added and economical light weight composite materials (2), carbonaceous materials, and adhesive materials (3). In the present study, value added and environment-friendly adhesive material is prepared from post-consumer expanded polystyrene (PCEPS) for possible applications. The physico-chemical properties of the prepared adhesives, such as, solubility, viscosity, shear strength / bonding strength, moisture content are estimated as per the standard procedures.
Methods: In the study, solubility method was used to prepare the adhesive materials. The moisture content of the adhesive products was determined using a Karl-Fischer (K-F) Titrator. The rheological properties of the adhesives were measured using a Brookfield Rheometer. To estimate the adhesive strength / shear strength of the adhesives, shear strength test was carried out using a universal testing machine (UTM).
Results & Discussions: The study shows that PCEPS is sufficiently soluble in various solvents, such as, m-xylene, n-BA, THF, MEK etc. Various substrate materials, such as, paper, wood, cement and clay bricks, and ceramic tiles are considered to check the suitability of the prepared adhesive to bind them. The study showed that the prepared adhesive (PCEPS-MEK) is suitable to bind the chosen substrate materials. The study further extended to bind the metal (iron) substrates with PCEPS adhesive. From the results, it is noticed that PCEPS adhesive offered lower bonding strength over commercial adhesive Araldite. Therefore, the study furthermore extended to enhance the PCEPS adhesive bonding strength using two different additives. The result shows that the bonding strength of the EPS adhesive decreased drastically with the increase of Additive-1. However, the bonding strength of EPS adhesive increased in presence of Additive-2 and its loading. Around 66% increment in bonding strength of PCEPS adhesive is obtained when the Additive-2 loading is increased from 10-50 wt.% under present experimental conditions. Therefore, Additive-2 can be used as one of the suitable additives to enhance the PCEPS adhesive properties especially bonding strength.
Conclusions: The prepared adhesive is suitable to bind the chosen substrate materials. Further it can be said that Additive-2 can be used as one of the suitable additives to enhance the PCEPS adhesive properties especially bonding strength. From the obtained results, it can be concluded that further in-depth study is needed to enhance the EPS adhesive properties, especially bonding strength by considering more suitable additives and their loading. 
Keywords: Adhesive, Viscosity, Additive, Bonding strength.
References

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