Preparation And Properties Of Enteromorpha Prolifera Nanocellulose/Polylactic Acid Composites

Nanocellulose has the advantages of large specific surface area,high strength,high crystallinity,extensive chemical modification and biocompatibility,and is excellent candidate materials for functional composite materials.However,at present,the raw materials for the preparation of nanocellulose are mainly terrestrial plants,and there are few related studies on marine algae cellulose.In order to realize the rational utilization of marine biomass resources,in this paper,nanofibrillated cellulose(NFC)was prepared from Enteromorpha prolifera cellulose,and NFC was esterified with acrylic acid(AA)and citric acid(CA),respectively.KH550 was used for silanization modification of NFC.AA-NFC/PLA,CA-NFC/PLA,KH550-NFC/PLA nanocomposite films were prepared by solution blending method,and the influence of the amount of nanocellulose on the composite materials' properties was discussed.Firstly,NFC was prepared by alkali treatment,bleaching,acid treatment and ultrasonic treatment with Enteromorpha prolifera as raw material,and hydrophobic modification of NFC was performed.The prepared NFC had a diameter of about 30-50 nm and a length of several micrometers,which were entangled with each other to form a network structure.The water contact angle test analysis showed that the functionalized NFC had significantly improved hydrophobicity,and KH550-NFC showed the best modification effect.KH550-NFC had a contact angle of 97.5%,which was 28.2%higher than NFC.XRD test analysis showed that NFC presents typical cellulose I crystal forms with a crystallinity of 57.2%.The crystal forms of the modified NFC had not been substantially destroyed,but the crystallinity had decreased.The crystallinity of AA-NFC and CA-NFC was 46.9%and 42.1%respectively;the crystallinity of KH550-NFC was 50.3%.AA-NFC/PLA nanocomposite films were prepared by solution blending.FT-IR test results showed that nanocellulose and polylactic acid were mainly bound by physical interaction.SEM and mechanical properties analysis showed that when the NFC content was less than 0.5 wt%,NFC could be uniformly dispersed in the PLA matrix,and the elastic modulus and tensile strength of the 0.5-NFC/PLA nanocomposite film were improved 85.49%and 16.78%,respectively,compared to pure PLA films.DSC test analysis showed that lower NFC helped to accelerate the crystallization rate of PLA and increase the crystallinity of composite materials.The degradation properties test analysis showed that with the increase of NFC content,the degradation rate increased significantly.When the NFC addition amount reached 1.2 wt%,the degradation mass loss of the composite film(at 50? environment)was increased by 250%compared to the pure PLA film.CA-NFC/PLA nanocomposite films were prepared by solution blending.FT-IR test results showed that nanocellulose and polylactic acid were mainly bound through physical interaction,but there was also weak chemical action.SEM and mechanical properties analysis showed that when the NFC content was less than 1.0 wt%,NFC was tightly bound to the PLA matrix and had great compatibility,the toughness of NFC/PLA nanocomposite film was 37.91%higher than that of pure PLA film.DSC test analysis showed that the addition of NFC helped to accelerate the crystallization rate of PLA and increase the crystallinity of composite materials.The degradation properties test analysis showed that with the increase of NFC content,the degradation rate increased significantly.When the NFC addition amount reached 2.0 wt%,the degradation mass loss of the composite film(at 50? environment)was increased by 52.2%compared to the pure PLA film.KH550-NFC/PLA nanocomposite films were prepared by solution blending.FT-IR test results showed that nanocellulose and polylactic acid were mainly bound through physical interaction,but there was also weak chemical action.SEM and mechanical properties test analysis showed that lower NFC could uniformly penetrated in the PLA matrix so that its section showed ductile fracture.When the NFC content was 0.3 wt%,the tensile strength and elongation at break of the composite film are respectively increased by 13.49%and 85.80%,and the toughness was increased by 108.13%compared with the pure PLA film.DSC test analysis showed that NFC could be used as a nucleating agent to accelerate the crystallization rate of PLA and increase the crystallinity of composite materials.The crystallinity of 0.5-NFC/PLA composite film improved 24.53%compared to the pure PLA.The degradation properties test analysis showed that with the increase of NFC content,the degradation rate increased significantly.When the amount of NFC reached 1.2 wt%,the degradation mass loss of the composite film(at 50? environment)was increased by 242.9% compared to the pure PLA film.