Physical and Mechanical Properties of Electrospun PLA Nanofibers in the Presence of Silicone Rubber Nanoparticles

Hypothesis: 

Nowadays, polymer nanofibers have been extensively used in different industries especially for medical applications. Electrospinning is a simple, versatile and cost-effective technique to prepare nanofibers. For biomedical applications such as tissue engineering poly(lactic acid) (PLA), a biocompatible and biodegradable polymer, has gained great interest. To improve the physical and mechanical properties of electrospun PLA, nanofibers and nanoparticles can be included.

PLA nanofibers were prepared through electrospinning. Silver nitrate was added to increase the conductivity of electrospinning solution, resulting in finer nanofibers. To improve morphology and mechanical properties of the electrospun fibers, silicone rubber nanoparticles (NSR) were added into the electrospinning solution. Scanning and transmission electron microscopies (SEM and TEM) were employed to investigate the morphology of electrospun nanofibers and dispersion of nanoparticles, respectively. To investigate thermal and mechanical properties of the obtained nanofibers, differential scanning calorimetry (DSC) and tensile test were used.

To obtain poly(lactic acid) electrospun nanofibers with fine and defect-free morphology, PLA was dissolved in a mixture of dichloromethane and dimethylformamide (DCM/DMF) solvents with a volumetric ratio of 3/2 Electrospinning solution with 7% poly(lactic acid) containing 0.5% (by wt) silver nitrate led to defect-free nanofibers with a diameter of less than 200 nm. Inclusion of silicone rubber nanoparticles of 1% resulted in finer nanofibers with a diameter of about 123 nm. This was attributed to enhanced elasticity of the solution with addition of elastomeric nanoparticles. Adding silicone rubber nanoparticles increased the cold crystallization temperature and decreased the crystallinity of polylactic acid. Toughness of nanofibers considerably increased in the presence of silicone rubber nanoparticles without sacrificing modulus and strength, indicating high capability of NSR as an impact modifier