Effects of Coagulation Conditions on the Properties of Regenerated Cellulose Films Prepared in NaOH/Urea Aqueous Solution

Abstract

Effects of coagulant components and coagulation conditions on the structure and properties of regenerated cellulose (RC) films prepared from cellulose in 7.5 wt % NaOH/11 wt % urea aqueous solution were investigated by 13C NMR, X-ray diffraction, scanning electron micrograph, tensile testing, etc. The uniform design method based on theoretical accomplishments in the number-theoretic method was used to optimize the coagulation conditions of H2SO4 aqueous solution with various concentrations (from 1 to 15 wt %), time (from 1 to 15 min), and temperature (from 25 to 55 °C). Moreover, a series of RC films coagulated, with 5 wt % H2SO4/Na2SO4, Na2SO4, HOAc, and (NH4)2SO4, respectively; different concentrations (from 1 to 20 wt %) and times (from 1 to 20 min) at 25 °C were also investigated. The results indicated that the optimal coagulant concentrations and coagulation times of the RC films are 5 wt % H2SO4 for 5 min, 5 wt % H2SO4/5 wt % Na2SO4 for 5 min, 5 wt % Na2SO4 for 15 min, 3 wt % HOAc for 5 min, and 5 wt % (NH4)2SO4 for 3 min, respectively, at 25 °C. The RC film that coagulated with 5 wt % H2SO4/5 wt % Na2SO4 aqueous solution exhibited a higher optical transmittance, more homogeneous structure, and better mechanical properties than that coagulated with others on the whole. Moreover, the tensile strength of the RC films in the wet and dry states increased simultaneously with a drop in coagulation temperature. The coagulation mechanism can be described as a two-phase separation, namely a cellulose-rich phase in the gel and a cellulose-poor phase in solution.

Pembuatan Partikel Selulosa Menggunakan Larutan Alkalin

“…Pada kasus tersebut kecepatan adukan tidak menghasilkan ukuran-ukuran partikel yang lebih kecil karena tidak cukup kuat untuk memecahkan koagulasi yang terjadi. Hal lain yang terjadi adalah proses koagulasi yang terjadi sangat cepat dikarenakan konsentrasi larutan garam yang tinggi [18,19]. Terlihat larutan selulosa yang dimasukkan langsung mengeras ketika menyentuh larutan garam.…”

Membran Selulosa Kenaf Terjana Semula daripada Larutan Akues NaOH/Urea yang Digumpal Menggunakan Asid Sulfurik

“…Oleh itu, membran selulosa yang mempunyai ciri fizikal yang baik boleh diperoleh dengan menggunakan penggumpal yang mempunyai kepekatan yang rendah pada masa penggumpalan yang sederhana. Menurut Zhang (2005), kepekatan yang tinggi dan masa penggumpalan yang lebih lama bukan sahaja memudahkan lagi proses penguraian selulosa, tetapi merupakan faktor kepada peningkatan saiz liang membran yang menyebabkan penurunan sifat mekanik. Di samping itu, kepekatan yang rendah dan masa penggumpalan yang singkat dapat mengawal kadar resapan antara penggumpal dan pelarut NaOH/urea yang membawa kepada kesukaran dalam proses penjanaan semula selulosa daripada penggumpalan.…”

Synthesis and Alignment of Iron Oxide Nanoparticles in a Regenerated Cellulose Film

“…[32] The resulting solution was centrifuged at 8 000 rpm for 20 min at 10-15 8C for degasification. The cellulose solution was cast on a glass plate and then immersed into 5 wt.-% H 2 SO 4 bath for 5 min for coagulation and regeneration of the cellulose films.…”

“…In our previous work, we have developed a novel solvent for cellulose, namely NaOH/urea aqueous solution, [29,30] and the regenerated cellulose films and fibers with excellent mechanical properties have been successfully prepared. [31][32][33] The excellent mechanical properties, microporous structure, chemical stability, biological compatibility, and remarkable hydrophilic properties of the cellulose films make them suitable templates for fabricating organic-inorganic nanocomposites.…”