The Impact of Primary Sludge on the Physical Features of High-Density Polyethylene (HDPE) Composites

Abstract

The cost-efficient reutilization of byproduct materials is a significant global goal, contributing towards the sustainable use of resources. In this study, the effects of including primary sludge in composite materials on their physical performance are examined, in order to achieve more effective reuse. The studied materials were made from high-density polyethylene (HDPE), anhydride-grafted polyethylene (MAPE), lubricants, and either wood flour from spruce (Picea abies) or primary sludge from the side-stream of forest industry processes as a filler. The materials were compounded by agglomeration, followed by manufacturing with a conical twin-screw extruder. The physical properties of the materials were characterized by water absorption and thickness swelling tests; furthermore, impact strength was characterized after the stress of a cyclic freeze-thawing test. The elemental compositions of the materials were also analyzed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). Primary sludge, as a component in the structure of the composite material, resulted in a significant improvement of moisture behaviors in the water absorption and thickness swelling tests. The identified results demonstrate that primary sludge is a technically applicable material for utilization in composite materials.

Implications of Pulp and Paper Mill Primary Sludge Incineration versus Use in Composites Production: Decision-Making Based on Life Cycle Assessment

“…The production of composites using primary sludge was modelled after Mustonen et al (2019) in terms of the recipe and after the study by Liikanen et al (2019) in terms of the inventory data. The environmental impacts were assessed using LCA methodology following the ISO standards (SFS-EN ISO 140-40, 2006;SFS-EN ISO 14044, 2006).…”

“…The production of composites was modelled following the recipe exposed in the study by Mustonen et al (2019). More specifically, the composites comprised of HDPE -50%, dewa-tered primary sludge -44%, maleic anhydride-grafted polyethylene (MAPE) -3.0%, and lubricant -3.0%.…”

“…Primary sludge was proven to be a suitable raw material in the production of high-density polyethylene (HDPE)-based composites (Mustonen et al, 2019). The water adsorption and thickness swelling were significantly improved compared to the reference specimen made of wood flour.…”

“…The goal of this paper is to assess the environmental impacts of using primary sludge in the production of polymer composites. The technical feasibility of composites production was studied extensively in previous studies by the authors (Lahtela et al, 2017;Mustonen et al, 2019). Furthermore, the paper compares this alternative utilization scenario with the baseline scenario of primary sludge incineration so as to facilitate decision-making in companies aiming at the reduction of their environmental impacts and promotion of the circular economy.…”