Ionizing radiation resistant thermoplastic resin composition and article comprising the same
A thermoplastic resin composition and a molded article formed of the same. The thermoplastic resin composition includes: a thermoplastic resin including a rubber-modified vinyl graft copolymer and an aromatic vinyl copolymer resin; polyalkylene glycol; and zinc oxide, wherein the zinc oxide has an average particle diameter of about 0.5 μm to about 3 μm and a BET specific surface area of about 1 m 2 /g to about 10 m 2 /g. The thermoplastic resin composition and the molded article formed thereof can have good properties in terms of discoloration resistance, antibacterial activity, and the like even after being irradiated with ionizing radiation.
1. A thermoplastic resin composition comprising:
about 100 parts by weight of a thermoplastic resin comprising about 5 wt % to about 60 wt % of a rubber-modified vinyl graft copolymer and about 40 wt % to about 95 wt % of an aromatic vinyl copolymer resin;
about 0.1 parts by weight to about 5 parts by weight of polyalkylene glycol having a number average molecular weight of 1,500 g/mol to 5,000 g/mol as measured by gel permeation chromatography (GPC), based on about 100 parts by weight of the thermoplastic resin; and
about 0.1 parts by weight to about 30 parts by weight of zinc oxide, based on about 100 parts by weight of the thermoplastic resin,
wherein the zinc oxide has an average particle diameter of about 0.5 μm to about 3 μm and a BET specific surface area of about 1 m 2 /g to about 10 m2/g.
2. The thermoplastic resin composition according to claim 1 , wherein the rubber-modified vinyl graft copolymer is obtained by grafting a monomer mixture comprising an aromatic vinyl monomer and a vinyl cyanide monomer to a rubber polymer.
3. The thermoplastic resin composition according to claim 1 , wherein the aromatic vinyl copolymer resin is a copolymer of an aromatic vinyl monomer and a monomer copolymerizable with the aromatic vinyl monomer.
4. The thermoplastic resin composition according to claim 1 , wherein the zinc oxide has a peak intensity ratio (B/A) of about 0.01 to about 1, where A indicates intensity of the peak in the wavelength range of 370 nm to 390 nm and B indicates intensity of the peak in the wavelength range of 450 nm to 600 nm in photoluminescence measurement.
5. The thermoplastic resin composition according to claim 1 , wherein the zinc oxide has a peak position degree (20) in the range of 35° to 37° and a crystallite size of about 1,000 Å to about 2,000 Å in X-ray diffraction (XRD) analysis, as calculated by Equation 1:
Crystallite
size
(
D
)
=
K
λ
β
cos
θ
[
Equation
1
]
where K is a shape factor, λ is an X-ray wavelength, β is an FWHM value (degree) of an X-ray diffraction peak, and θ is a peak position degree.
6. The thermoplastic resin composition according to claim 1 , wherein the thermoplastic resin composition has a difference in yellow index (ΔYI) of about 0.5 to about 5, as calculated on a 3.2 mm thick specimen according to Equation 2:
[Equation 2]
ΔYI=YI 1 −YI 0
where YI 0 is a yellow index (YI) of the specimen before irradiation with gamma rays, as measured in accordance with ASTM D1925, and YI 1 is a yellow index (YI) of the specimen, as measured in accordance with ASTM D1925 after the specimen is irradiated with 40 kGy gamma rays and allowed to stand for 21 days.
7. The thermoplastic resin composition according to claim 1 , wherein the thermoplastic resin composition has an antibacterial activity of about 2 to about 7 against Staphylococcus and an antibacterial activity of about 2 to about 7 against Escherichia coli , as measured on a 5 cm×5 cm specimen in accordance with JIS Z 2801 after the specimen is subjected to inoculation with each of Staphylococcus aureus and Escherichia coli , followed by culturing under conditions of 35° C. and 90% RH for 24 hours.
8. The thermoplastic resin composition according to claim 7 , wherein the thermoplastic resin composition has an antibacterial activity of about 4 to about 7 against Staphylococcus and about 2.4 to about 7 against Escherichia coli , as measured on a 5 cm×5 cm specimen in accordance with JIS Z 2801 after the specimen is subjected to inoculation with each of Staphylococcus aureus and Escherichia coli , followed by culturing under conditions of 35° C. and 90% RH for 24 hours.
9. A molded article formed of the thermoplastic resin composition according to claim 1 .
10. The molded article according to claim 9 , wherein the molded article is an ionizing radiation resistant medical supply.
11. The thermoplastic resin composition according to claim 1 , wherein the polyalkylene glycol has a number average molecular weight of 2,000 g/mol to 5,000 g/mol as measured by gel permeation chromatography (GPC).