Polyester resin composition with excellent impact resistance and light reliability and molded article using the same
A polyester resin composition and a molded article produced using the same. The polyester resin composition includes: (A) two polyester resins including an aliphatic ring structure and having different trans/cis isomer ratios in the aliphatic ring; (B) a white pigment; and (C) an inorganic filler, wherein the polyester resin composition has a crystallization temperature (Tc) of about 230° C. to about 250° C., as measured by differential scanning calorimetry (DSC) while cooling the resin composition at a cooling rate of −100° C./min.
1. A polyester resin composition, comprising:
(A-1) a first polyester resin comprising poly(1,4-cyclohexylene dimethylene terephthalate) (PCT) resin having a trans/cis isomer ratio of about 2.6 to about 3.0; and
(A-2) a second polyester resin comprising poly(1,4-cyclohexylene dimethylene terephthalate) (PCT) resin having a trans/cis isomer ratio of about 1.8 to about 2.1;
(B) a white pigment comprising titanium oxide; and
(C) an inorganic filler,
wherein a weight ratio of the first polyester resin (A-1) to the second polyester resin (A-2) ranges from about 1:4 to about 4:1,
wherein the inorganic filler (C) comprises (C-1) a first inorganic filler and (C-2) a second inorganic filler, and wherein the first inorganic filler (C-1) comprises glass fibers and the second inorganic filler (C-2) comprises wollastonite,
wherein a weight ratio of the first inorganic filler (C-1) to the second inorganic filler (C-2) ranges from about 1:3 to about 3:1, and
wherein the polyester resin composition has a crystallization temperature (Tc) of about 230° C. to about 250° C., as measured by differential scanning calorimetry (DSC) while cooling the resin composition at a cooling rate of −100° C./min.
2. The polyester resin composition according to claim 1 , further comprising: (D) an impact modifier.
3. The polyester resin composition according to claim 1 , comprising:
about 10 wt % to about 40 wt % of the first polyester resin (A-1);
about 10 wt % to about 40 wt % of the second polyester resin (A-2);
about 10 wt % to about 60 wt % of the white pigment (B); and
about 5 wt % to about 40 wt % of the inorganic filler (C).
4. The polyester resin composition according to claim 1 , wherein each of the first polyester resin (A-1) and the second polyester resin (A-2) comprises a poly(1,4-cyclohexylene dimethylene terephthalate) (PCT) resin represented by Formula 1:
wherein m is an integer from 50 to 500.
5. The polyester resin composition according to claim 1 , wherein a total amount of the first polyester resin (A-1) and the second polyester resin (A-2) ranges from about 30 wt % to about 70 wt % based on the total weight of (A-1), (A-2), (B), and (C).
6. The polyester resin composition according to claim 1 , wherein each of the first polyester resin (A-1) and the second polyester resin (A-2) has an intrinsic viscosity (TO) of about 0.4 dl/g to about 1.5 dl/g, as measured in an o-chlorophenol solution at 25° C.
7. The polyester resin composition according to claim 1 , wherein the titanium oxide has an average particle diameter of about 0.05 μm to about 2.0 μm.
8. The polyester resin composition according to claim 1 , further comprising an additive selected from the group consisting of antioxidants, photostabilizers, fluorescent brighteners, antistatic agents, release agents, heat stabilizers, dyes, nucleating agents, plasticizers, admixtures, colorants, stabilizers, lubricants, flame retardants, and mixtures thereof.
9. A molded article produced using the polyester resin composition according to claim 1 .
10. The molded article according to claim 9 , wherein the molded article is a reflector for LEDs.
11. The molded article according to claim 9 , wherein the molded article has an Izod impact strength of about 15 kgf·cm/cm to about 20 kgf·cm/cm, as measured on a ⅛″ thick unnotched Izod specimen in accordance with ASTM D256, and an initial reflectance (R 0 ) of about 90% or higher, as measured at a wavelength of 450 nm using a colorimeter.
12. The molded article according to claim 11 , wherein the molded article has a reflectance retention rate of about 85% to about 99%, as calculated by Equation 1:
Reflectance retention rate ( R V ) (%)={( R 1 /R 0 )}×100
wherein R 0 is initial reflectance of the molded article as measured at a wavelength of 450 nm using a colorimeter, and R 1 is reflectance of the molded article after irradiation at a wavelength of 450 nm for 1,000 hours using an LED light source in a thermos-hygrostat oven at 85° C./85% RH.