Characteristics Test method Condition Unit OKP4 OKP4HT (For reference) (For reference) PMMA PC (for optics) COP Physical property Specific gravity Density method — g/cm3 1.22 1.26 1.2 1.01 1.19 Water absorption JIS K7209 — % 0.2 0.2 0.2 < 0.01 0.3 Glass transition temperature DSC — ℃ 121 143 145 138 110 Heat distortion temperature JIS K7207 18.5kgf/cm2 ℃ 105 128 126 123 100 Coefficient of thermal expansion JIS K7197 30?120℃ 10-5/K 7.2 6.9 7 7 6 Optical properties Light transmittance JIS K7105 700nm, 3mmT % 90 90 89 92 93 Refractive index (nd) Abbe refractometer 589nm(20℃) — 1.607 1.632 1.585 1.525 1.49 Temperature dependence coefficient Abbe refractometer — 10-5/K -13 -11 -12 -10 -10 Abbe number Abbe refractometer — — 27 23 29 56 58 Mechanical properties Tensile strength JIS K7113 — MPa 71 65 52 59 73 Tensile elongation JIS K7113 — % 9 10 110 40 5 Flexural modulus JIS K7203 — MPa 2.7 2.5 2.4 2.1 3.3 Flexural strength JIS K7203 — MPa 120 115 96 94 120 Impact strength ASTM D256 — J/m 58 43 78 24 15.7 Pencil hardness JIS K5401 — — 2H H B H 2H Moldability properties MFR JIS K6719 230℃, g/10min 12 3 65 (300℃, 1.2kg) 21 (280℃, 2.16kg) 2 (230℃, 2.16kg 3.8kg