| 要約: | Every year, the rate of accident involving bone fractures increases rapidly and most
fractures need to be fixed with surgical bone implants. Most implants are made from
medical grade metal such as stainless steel, cobalt, titanium and others. One of the
characters of a good short term implant is its ability to be degraded after bones have
healed. However, most of the temporary implants are made from non-biodegradable
metals. In consequence, magnesium alloys has potential to be used as short term
implants due to their ability to degrade in chloride containing solution and properties
similar to human bones. However, its high degradation rate limits its clinical
applications. This study has introduced an approach to control the corrosion rate of high
purity magnesium (HP Mg) and AZ91 by coating them with polymeric membrane of
poly-L-lactic acid (PLLA) by electrospinning. An 8 wt % of PLLA was magnetic stirred
to dissolve in the chloroform at room temperature. The prepared PLLA solution was
then fed into a 10 ml syringe with thin needle. The electrospun coating of PLLA on HP
Mg and AZ91 samples were done at feed rate of 1 ml/hr, voltage of 10 kV and distance
of 15 cm between the syringe tip and collector. Scanning electron microscope (SEM)
and microscratch test were done to characterize the thickness and adhesiveness of the
coating on HP Mg and AZ91. In addition ASTM 3359 standard test and surface profiler
were also performed to study the adhesiveness and thickness of the coating respectively.
The corrosion behaviour of uncoated Mg and Mg coated PLLA samples were studied by
immersing them in Hank’s solution for 14 days at human body temperature (37 °C). The
pH of Hank’s solution was maintained at 7. The corrosion rate was calculated from
evolved hydrogen during the immersion and weight loss after immersion. The surface of
the samples before and after immersion was evaluated by scanning electron microscope
(SEM). It was observed that PLLA was successfully coated the HP Mg and AZ91
samples. The corrosion rates of HP Mg and AZ91 coated PLLA samples without hole
were found lower than uncoated samples. PLLA coating on HP Mg and AZ91 by
electrospinning has improved the corrosion resistance by delaying the corrosion
initiation.
Keywords: Magnesium, PLLA coating, Hydrogen Evolution, Weight loss, SEM.
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