دانلود گزارش کارورزی و کار آموزی

چکیده : 

We investigated the spinning of hydroalcoholic chitosan solutions. The dope composition was optimizedin order to obtain a continuous alcogel fiber by water evaporation on heating the extruded hydroalcoholicsolution. This alcogel fiber was then neutralized in aqueous alkali baths and washed in water to eliminatethe residual alcohol and salts before final drying. Depending on the alcohol content in the filament atthe neutralization step, on specific alcohol–chitosan interactions and on the nature and concentrationof the coagulation base, the process yielded semicrystalline chitosan fibers with different proportionsof anhydrous and hydrated allomorphs. Contrarily to the classical annealing method, the formation ofmainly anhydrous crystals was obtained without significant molecular weight decrease by neutralizingthe polymer in hydrophobic conditions. The control of allomorph content was shown to be related to thehydrophobicity of the solvent (alcohol fraction) at the neutralization step.