Effect of alkali treatment on composites made from recycled polyethylene and chestnut cupula

The objective of this study is to investigate the effects of alkali treatment on themechanical, physical properties of cupula fibers reinforced recycled high density poly-ethylene (r-HDPE) composites. The composites were produced with different chestnut(Castanea sativaMill.) cupula fiber contents, up to 50%, and polyethylene-graftedmaleic anhydride. The mechanical, physical, thermal, and morphological properties ofthe treated and untreated samples were investigated. In addition, the Fourier transforminfrared spectroscopy (FTIR) was used toobserve the interactions and functionalgroups between cupula fiber and r-HDPE inthe composite samples. The alkali treat-ment with 5 wt% NaOH solution had an affirmative effect on the tensile and flexuralproperties. It was found that an increase of 20% in flexural strength values with up to40 wt% alkali treated cupulafiber loading in polymer matrixcomparedtothatofuntreated samples. After 5 wt% NaOH treatment, the crystallinity decreased with theincrease of the chestnut cupula fiber ratio. As excepted, the FTIR analysis showed thatthe alkali treatment resulted in removal of hemicellulose, and lignin from cupula fiber.The results revealed that the alkali treatedchestnut cupula fiber can be used success-fully in polymer composites as a natural fiber fille