Revaluation of pine nutshell waste ( Araucaria angustifolia ) in recycled PP composites: Mechanical and thermal properties and life cycle assessment

The extensive use of plastics in packaging causes several environmental impacts. A promising alternative is the development of composites reinforced with agro-industrial waste. This study investigates the use of pine nutshell (Araucaria angustifolia) waste (PR) as a sustainable filler in recycled polypropylene (PPr) from ice cream packaging, with 10 and 20 wt% PR and a coupling agent (MAPP). The physicochemical, mechanical, morphological, and thermal properties were evaluated, along with a Life Cycle Assessment, to assess the environmental benefits of incorporating PR. FTIR analyses confirmed that the coupling agent (MAPP) significantly improved fiber–matrix interaction with the pine nutshell fiber through covalent or hydrogen bonds. MAPP increased the composites’ glass transition temperature (Tg), limiting polymer chain mobility and enhancing thermal stability, particularly at higher fiber contents. Fiber incorporation resulted in a slight decrease in tensile strength but an increase in tensile modulus, which was influenced by both fiber content and the use of MAPP, as shown by morphological analysis. Flexural tests demonstrated that the addition of fiber and MAPP effectively enhanced the composite’s strength and stiffness by strengthening the interfacial bonding. The life cycle assessment revealed beneficial environmental gains from fiber inclusion, particularly in reducing terrestrial acidification, global warming, human carcinogenicity, and fine particulate matter formation. These composites present sustainable alternatives, particularly with 20 wt% PR and the use of a coupling agent, which demonstrated improved thermal and mechanical performance, in addition to environmental benefits.