Surface behavior and film formation analysis of sisal fiber coated by poly(methyl methacrylate) ultrathin film

Admicellar polymerization was used to modify a sisal fiber surface with poly(methyl methacrylate) (PMMA) in order to improve the compatibility between the sisal fiber and the surrounding polymeric matrix in a composite. The effect of the amount of monomer (methyl methacrylate) and initiator (sodium persulfate) on the hydrophobicity behavior and PMMA film formation of the admicellar-treated sisal surface was studied. The increase in the hydrophobicity of the admicellar-treated sisal fiber was examined by flotation testing, moisture absorption, and electrostatic charge or zeta (ζ) potential. The amount of PMMA film formed on the sisal surface was investigated by the weight loss of the admicellar-treated sisal extracted by acetone and chloroform; and the thermal degradation was studied by thermogravimetric analyses. The admicellar-treated sisal could float on the surface of water for longer than half an hour, and its moisture absorption decreased. The ζ potential of its surface also showed a significant change compared to the untreated sisal. The results from the weight loss indicated that the amount of PMMA formed on the sisal fiber surface depended on the amount of monomer and initiator. The Fourier transform infrared spectrum of the admicellar-treated sisal showed the characteristic peaks of PMMA and the scanning electron micrograph of the treated sisal was clearly different from the untreated sisal, confirming that there was a thin film coating on the admicellar-treated sisal fiber.