{"L1_core": {"domain": "material", "category": "polymer", "subcategory": "thermoplastic", "abbreviation": "PMMA", "chemical_name": "poly(methyl methacrylate)"}, "L5_metadata": {"updated": "2026-01-04", "version": "1.0"}, "L3_standards": {"iso": ["ISO 7823"], "astm": ["ASTM D788"]}, "L2_properties": {"physical": {"density_g_cm3": [1.17, 1.20], "refractive_index": 1.49, "glass_transition_c": 105, "light_transmission_pct": 92}, "mechanical": {"elastic_modulus_gpa": [2.4, 3.3], "tensile_strength_mpa": [55, 75]}, "characteristics": ["transparent", "UV-resistant", "shatter-resistant", "weatherable"]}, "L4_applications": ["signage", "aquariums", "lighting", "protective-screens"]}