Author: Mustafa Dedeoglu

This comparison presents the key properties of unfilled PET in its amorphous and semi-crystalline forms. The table covers physical, mechanical, thermal, electrical, optical, processing, durability, environmental, and recycling-related properties.

Property	PET – Unfilled, Amorphous	PET – Unfilled, Semi-Crystalline
Designation	Polyethylene Terephthalate (unfilled, amorphous)	Polyethylene Terephthalate (unfilled, semi-crystalline)
Typical uses	Blow molded bottles, packaging film, film, photographic and x-ray film, audio/visual tapes, industrial strapping, capacitor film, drawing office transparencies, fibers.	Electrical fittings and connectors, audio/visual tapes, industrial strapping, capacitor film, fibers.
Compositional summary	(CO-(C6H4)-CO-O-(CH2)2-O)n	(CO-(C6H4)-CO-O-(CH2)2-O)n
Material family	Plastic (thermoplastic, amorphous)	Plastic (thermoplastic, semi-crystalline)
Base material	PET (Polyethylene terephthalate)	PET (Polyethylene terephthalate)
Polymer code	PET	PET
Polymer	100 %	100 %
Density	1.29 – 1.39 g/cm³	1.37 – 1.4 g/cm³
Young’s modulus	2.8 – 3 GPa	2.76 – 3.1 GPa
Specific stiffness	2.06 – 2.28 MN.m/kg	1.99 – 2.24 MN.m/kg
Yield strength (elastic limit)	50 – 55 MPa	65 – 70 MPa
Tensile strength	55 – 60 MPa	70 – 75 MPa
Specific strength	36.9 – 41.6 kN.m/kg	46.9 – 50.6 kN.m/kg
Elongation	280 – 320 % strain	65 – 75 % strain
Compressive modulus	2.76 – 4.14 GPa	2.76 – 4.14 GPa
Compressive strength	50 – 60 MPa	75.8 – 103 MPa
Flexural modulus	2.41 – 3.09 GPa	2.99 – 3.09 GPa
Flexural strength (modulus of rupture)	50 – 60 MPa	70 – 75 MPa
Shear modulus	0.994 – 1.49 GPa	0.994 – 1.49 GPa
Bulk modulus	4.94 – 5.19 GPa	4.94 – 5.19 GPa
Poisson’s ratio	0.381 – 0.396	0.381 – 0.396
Shape factor	5.6	4.9
Hardness – Vickers	2 – 5 HV	17 – 20 HV
Hardness – Rockwell M	28 – 30	82 – 87
Hardness – Rockwell R	45 – 50	120 – 125
Elastic stored energy (springs)	430 – 524 kJ/m³	709 – 853 kJ/m³
Fatigue strength at 10^7 cycles	19.3 – 29 MPa	19.3 – 29 MPa
Fracture toughness	4.75 – 5.25 MPa.m^0.5	4.75 – 5.25 MPa.m^0.5
Toughness (G)	7.76 – 9.54 kJ/m²	7.62 – 9.54 kJ/m²
Impact strength, notched 23 °C	6.19 – 6.83 kJ/m²	2.86 – 3.15 kJ/m²
Impact strength, unnotched 23 °C	590 – 600 kJ/m²	590 – 600 kJ/m²
Melting point	NA (Amorphous PET does not have a melting temperature because it lacks a long-range, ordered crystalline structure.)	255 – 265 °C
Glass temperature	60 – 84 °C	68 – 80 °C
Heat deflection temperature 0.45MPa	70 – 74 °C	105 – 115 °C
Heat deflection temperature 1.8MPa	68 – 72 °C	70 – 80 °C
Maximum service temperature	55 – 65 °C	115 – 120 °C
Minimum service temperature	-58 – -38 °C	-58 – -38 °C
Thermal conductivity	0.138 – 0.151 W/m.°C	0.138 – 0.151 W/m.°C
Specific heat capacity	1.15e3 – 1.25e3 J/kg.°C	1.1e3 – 1.2e3 J/kg.°C
Thermal expansion coefficient	115 – 119 µstrain/°C	75 – 80 µstrain/°C
Thermal shock resistance	145 – 164 °C	276 – 321 °C
Thermal distortion resistance	0.00117 – 0.0013 MW/m	0.00176 – 0.00197 MW/m
Electrical resistivity	3.3e20 – 3e21 µohm.cm	3.3e20 – 3e21 µohm.cm
Electrical conductivity	5.75e-20 – 5.22e-19 %IACS	5.75e-20 – 5.22e-19 %IACS
Dielectric constant (relative permittivity)	3.5 – 3.7	3.5 – 3.7
Dissipation factor (dielectric loss tangent)	0.003 – 0.007	0.002 – 0.003
Dielectric strength (dielectric breakdown)	36 – 44 MV/m	16.5 – 18 MV/m
Comparative tracking index	200 – 325 V	200 – 325 V
Magnetic type	Non-magnetic	Non-magnetic
Refractive index	1.57 – 1.58	1.57 – 1.58
Transparency	Optical quality	Opaque
Acoustic velocity	1.43e3 – 1.51e3 m/s	1.41e3 – 1.5e3 m/s
Mechanical loss coefficient (tan delta)	0.00966 – 0.0145	0.00966 – 0.0145
Contains >5wt% critical elements?	No	No
Water absorption @ 24 hrs	0.14 – 0.18 %	0.1 – 0.2 %
Water vapor transmission	0.464 – 0.707 g.mm/m².day	0.464 – 0.707 g.mm/m².day
Permeability (O2)	1.2 – 2.77 cm³.mm/m².day.atm	1.2 – 2.77 cm³.mm/m².day.atm
Polymer injection molding	Acceptable	Acceptable
Polymer extrusion	Limited use	Limited use
Polymer thermoforming	Acceptable	Limited use
Linear mold shrinkage	0.3 – 0.5 %	1.5 – 1.7 %
Melt temperature	260 – 280 °C	260 – 280 °C
Mold temperature	20 – 30 °C	125 – 145 °C
Molding pressure range	13.8 – 48.1 MPa	13.8 – 48.1 MPa
Water (fresh)	Excellent	Excellent
Water (salt)	Excellent	Excellent
Weak acids	Acceptable	Acceptable
Strong acids	Unacceptable	Unacceptable
Weak alkalis	Acceptable	Acceptable
Strong alkalis	Limited use	Limited use
Organic solvents	Limited use	Limited use
Oxidation at 500C	Unacceptable	Unacceptable
UV radiation (sunlight)	Fair	Fair
Flammability	Highly flammable	Highly flammable
Embodied energy, primary production	78.4 – 86.4 MJ/kg	78.4 – 86.4 MJ/kg
CO2 footprint, primary production	2.59 – 2.86 kg/kg	2.59 – 2.86 kg/kg
Water usage	126 – 140 l/kg	126 – 140 l/kg
Polymer extrusion energy	5.82 – 6.43 MJ/kg	5.8 – 6.42 MJ/kg
Polymer extrusion CO2	0.437 – 0.483 kg/kg	0.435 – 0.481 kg/kg
Polymer extrusion water	4.83 – 7.24 l/kg	4.82 – 7.23 l/kg
Polymer molding energy	18.7 – 20.6 MJ/kg	18.2 – 20.1 MJ/kg
Polymer molding CO2	1.4 – 1.55 kg/kg	1.36 – 1.51 kg/kg
Polymer molding water	12.6 – 18.9 l/kg	12.4 – 18.6 l/kg
Coarse machining energy	0.864 – 0.954 MJ/kg	1.08 – 1.19 MJ/kg
Coarse machining CO2	0.0648 – 0.0716 kg/kg	0.0811 – 0.0896 kg/kg
Fine machining energy	4.36 – 4.82 MJ/kg	6.54 – 7.22 MJ/kg
Fine machining CO2	0.327 – 0.361 kg/kg	0.49 – 0.542 kg/kg
Grinding energy	8.25 – 9.11 MJ/kg	12.6 – 13.9 MJ/kg
Grinding CO2	0.618 – 0.684 kg/kg	0.945 – 1.04 kg/kg
Embodied energy, recycling	26.8 – 29.6 MJ/kg	26.8 – 29.6 MJ/kg
CO2 footprint, recycling	1.45 – 1.6 kg/kg	1.45 – 1.6 kg/kg
Recycle fraction in current supply	20 – 22.1 %	20 – 22.1 %
Heat of combustion (net)	23 – 24.2 MJ/kg	23 – 24.2 MJ/kg
Combustion CO2	2.24 – 2.35 kg/kg	2.24 – 2.35 kg/kg

Polycarbonate (PC) is supplied in both high- and low-viscosity molding and extrusion grades, both based on the same bisphenol-A (BPA) homopolymer chemistry. The two grades share identical density, pricing, and the great majority of mechanical, thermal, electrical, and environmental properties – differing chiefly in molecular weight. The high-viscosity grade’s higher molecular weight gives it markedly greater impact toughness (up to roughly three times higher in unnotched impact strength) and a modest edge in heat deflection and maximum service temperature, but it is harder to process, requiring higher melt temperatures and molding pressures. The low-viscosity grade trades some of that toughness for easier processability, slightly better elongation at break, and marginally lower processing energy and emissions. The table below sets the full property sets of both grades side by side, with the properties that actually differ between them highlighted for quick reference.

Property	PC High Viscosity	PC Low Viscosity	Unit	Difference
General Information
Designation	High Viscosity, Unfilled, Molding and Extrusion	Low Viscosity, Unfilled, Molding and Extrusion	—	Grade designation differs
Compositional note	Higher molecular weight; less processable but more tough	Lower molecular weight; more processable but less tough	—	High-visc = tougher/less processable; Low-visc = more processable/less tough
Material family	Plastic (thermoplastic, amorphous)	Plastic (thermoplastic, amorphous)	—	Identical
Base material	PC (Polycarbonate)	PC (Polycarbonate)	—	Identical
Polymer code	PC	PC	—	Identical
Polymer content	100	100	%	Identical
Physical Properties
Density	1.19 – 1.21	1.19 – 1.21	g/cm³	Identical
Mechanical Properties
Young’s modulus	2.32 – 2.44	2.32 – 2.44	GPa	Identical
Specific stiffness	1.93 – 2.04	1.93 – 2.04	MN.m/kg	Identical
Yield strength (elastic limit)	59.1 – 65.2	59.1 – 65.2	MPa	Identical
Tensile strength	62.7 – 72.4	62.7 – 72.4	MPa	Identical
Specific strength	49.2 – 54.4	49.2 – 54.4	kN.m/kg	Identical
Elongation	110 – 120	110 – 150	% strain	Low visc. has higher max elongation (up to 150 vs 120)
Compressive modulus	2.35 – 2.47	2.35 – 2.47	GPa	Identical
Compressive strength	69 – 86.2	69 – 86.2	MPa	Identical
Flexural modulus	2.27 – 2.34	2.27 – 2.34	GPa	Identical
Flexural strength (modulus of rupture)	86.2 – 93.1	82.7 – 96.5	MPa	Low visc. range is wider (lower min, higher max)
Shear modulus	0.829 – 0.872	0.829 – 0.872	GPa	Identical
Bulk modulus	3.83 – 4.03	3.83 – 4.03	GPa	Identical
Poisson’s ratio	0.391 – 0.407	0.391 – 0.407	—	Identical
Shape factor	4.6	4.6	—	Identical
Hardness – Vickers	18 – 20	18 – 20	HV	Identical
Hardness – Rockwell M	70 – 75	70 – 75	—	Identical
Hardness – Rockwell R	104 – 115	104 – 115	—	Identical
Elastic stored energy (springs)	734 – 894	734 – 894	kJ/m³	Identical
Fatigue strength at 10^7 cycles	23.7 – 30.8	23.7 – 30.8	MPa	Identical
Impact & Fracture Properties
Fracture toughness	2.1 – 2.3	2.1 – 2.3	MPa.m^0.5	Identical
Toughness (G)	1.85 – 2.23	1.85 – 2.23	kJ/m²	Identical
Impact strength, notched, 23 °C	69.7 – 102	10.1 – 83.1	kJ/m²	High visc. is notably tougher (min 69.7 vs 10.1)
Impact strength, notched, -30 °C	12.6 – 15	5.65 – 23.3	kJ/m²	Low visc. has a much wider/lower range at min
Impact strength, unnotched, 23 °C	590 – 600	188 – 226	kJ/m²	High visc. is dramatically tougher (~3x higher)
Impact strength, unnotched, -30 °C	590 – 600	183 – 220	kJ/m²	High visc. is dramatically tougher (~3x higher)
Thermal Properties
Glass temperature	142 – 158	142 – 158	°C	Identical
Heat deflection temperature, 0.45 MPa	138 – 142	134 – 138	°C	High visc. slightly higher
Heat deflection temperature, 1.8 MPa	121 – 132	121 – 132	°C	Identical
Maximum service temperature	104 – 119	101 – 116	°C	High visc. slightly higher
Minimum service temperature	-47 – -37	-47 – -37	°C	Identical
Thermal conductivity	0.189 – 0.205	0.193 – 0.218	W/m.°C	Low visc. slightly higher
Specific heat capacity	1150 – 1250	1150 – 1250	J/kg.°C	Identical
Thermal expansion coefficient	120 – 125	120 – 125	µstrain/°C	Identical
Thermal shock resistance	201 – 226	201 – 226	°C	Identical
Thermal distortion resistance	0.00154 – 0.00168	0.00157 – 0.00179	MW/m	Low visc. slightly higher
Electrical Properties
Electrical resistivity	1e20 – 1e21	1e20 – 1e21	µohm.cm	Identical
Electrical conductivity	1.72e-19 – 1.72e-18	1.72e-19 – 1.72e-18	%IACS	Identical
Dielectric constant (relative permittivity)	3.1 – 3.3	3.1 – 3.3	—	Identical
Dissipation factor (dielectric loss tangent)	8.6e-4 – 9.4e-4	8.6e-4 – 9.4e-4	—	Identical
Dielectric strength (dielectric breakdown)	16 – 19.2	16 – 19.2	MV/m	Identical
Comparative tracking index	175 – 325	175 – 325	V	Identical
Magnetic Properties
Magnetic type	Non-magnetic	Non-magnetic	—	Identical
Optical, Aesthetic & Acoustic Properties
Refractive index	1.58 – 1.59	1.58 – 1.59	—	Identical
Transparency	Optical quality	Optical quality	—	Identical
Acoustic velocity	1.39e3 – 1.43e3	1.39e3 – 1.43e3	m/s	Identical
Mechanical loss coefficient (tan delta)	0.0164 – 0.0172	0.0164 – 0.0172	—	Identical
Critical Materials Risk
Contains >5wt% critical elements?	No	No	—	Identical
Absorption & Permeability
Water absorption @ 24 hrs	0.135 – 0.165	0.135 – 0.165	%	Identical
Water vapor transmission	1.1 – 2.05	1.1 – 2.05	g.mm/m².day	Identical
Permeability (O2)	91.6 – 105	91.6 – 105	cm³.mm/m².day.atm	Identical
Processing Properties
Polymer injection molding	Excellent	Acceptable	—	High visc. rated better for injection molding
Polymer extrusion	Acceptable	Acceptable	—	Identical
Polymer thermoforming	Excellent	Excellent	—	Identical
Linear mold shrinkage	0.5 – 0.7	0.5 – 0.7	%	Identical
Melt temperature	226 – 322	205 – 298	°C	High visc. requires higher melt temperature
Mold temperature	70 – 100	70 – 100	°C	Identical
Molding pressure range	69 – 138	55 – 103	MPa	High visc. requires higher molding pressure
Durability
Water (fresh)	Excellent	Excellent	—	Identical
Water (salt)	Excellent	Excellent	—	Identical
Weak acids	Excellent	Excellent	—	Identical
Strong acids	Excellent	Excellent	—	Identical
Weak alkalis	Acceptable	Acceptable	—	Identical
Strong alkalis	Unacceptable	Unacceptable	—	Identical
Organic solvents	Limited use	Limited use	—	Identical
Oxidation at 500 °C	Unacceptable	Unacceptable	—	Identical
UV radiation (sunlight)	Fair	Fair	—	Identical
Flammability	Slow-burning	Slow-burning	—	Identical
Primary Production Energy, CO2 & Water
Embodied energy, primary production	100 – 111	100 – 111	MJ/kg	Identical
CO2 footprint, primary production	4.53 – 4.99	4.53 – 4.99	kg/kg	Identical
Water usage	165 – 182	165 – 182	l/kg	Identical
Processing Energy, CO2 Footprint & Water
Polymer extrusion energy	5.82 – 6.43	5.78 – 6.39	MJ/kg	High visc. marginally higher
Polymer extrusion CO2	0.437 – 0.483	0.434 – 0.48	kg/kg	High visc. marginally higher
Polymer extrusion water	4.83 – 7.24	4.81 – 7.22	l/kg	High visc. marginally higher
Polymer molding energy	18.7 – 20.6	17.6 – 19.5	MJ/kg	High visc. higher
Polymer molding CO2	1.4 – 1.55	1.32 – 1.46	kg/kg	High visc. higher
Polymer molding water	12.6 – 18.9	12.2 – 18.2	l/kg	High visc. higher
Coarse machining energy (per unit wt removed)	1.09 – 1.2	1.09 – 1.2	MJ/kg	Identical
Coarse machining CO2 (per unit wt removed)	0.0814 – 0.09	0.0814 – 0.09	kg/kg	Identical
Fine machining energy (per unit wt removed)	6.58 – 7.27	6.58 – 7.27	MJ/kg	Identical
Fine machining CO2 (per unit wt removed)	0.494 – 0.546	0.494 – 0.546	kg/kg	Identical
Grinding energy (per unit wt removed)	12.7 – 14	12.7 – 14	MJ/kg	Identical
Grinding CO2 (per unit wt removed)	0.951 – 1.05	0.951 – 1.05	kg/kg	Identical
Recycling & End of Life
Recycle	Yes	Yes	—	Identical
Embodied energy, recycling	35 – 38.7	35 – 38.7	MJ/kg	Identical
CO2 footprint, recycling	2.32 – 2.56	2.32 – 2.56	kg/kg	Identical
Recycle fraction in current supply	0.672 – 0.742	0.672 – 0.742	%	Identical
Downcycle	Yes	Yes	—	Identical
Combust for energy recovery	Yes	Yes	—	Identical
Heat of combustion (net)	30.3 – 31.8	30.3 – 31.8	MJ/kg	Identical
Combustion CO2	2.7 – 2.84	2.7 – 2.84	kg/kg	Identical
Landfill	Yes	Yes	—	Identical
Biodegrade	No	No	—	Identical