Plastic Material: Density & Specific Gravity

Definition: Density v.s. Specific Gravity
Density and specific gravity sound quite similar, some even say that they are synonyms; however, they are actually not the same, below we are going to introduce the differences of them.

What's the meaning of "Density"?
Density is mass or weight of a substance per unit volume under normal temperature and pressure.

First, we have to know that the formula of density is:

D = M / V
D = Density ; M = Mass ; V = Volume

As formula shown, density is total mass of the object divided by total volume of object, which means: 1 gram per cubic centimetre or 1 kilogram per cubic metre.
Density of water is 1 gram per cubic centimeter (1 g/cm3), but actually, the exact density of water is not really 1 g/cm3, but rather a bit less (very, very little less) than 1, so we can say that generally the weight and volume of water is the same.

What's the meaning of "Specific Gravity"?
Specific Gravity means specific value of an object under normal temperature and pressure.

The formula or specific gravity is:

Specific Gravity = Dobject / DH2O
DobjectDensity of the objectDH2ODensity of water

The difference of Density & Specific Gravity

"Density" has its own unit of measurement, 1 g/cm3 or 1 kg/m3, in contrast, specific gravity has no unit of measurement goes with it; nevertheless, although they don't have the same meaning, they have the same value because density of water is quite close to 1g/cm3.


i.e. 1 cm3 water weighs 1 g (as mentioned, density of water is 1g/cm3), and 1cm3 aluminum weighs 2.7 g (the density is 2.7 g/cm3), thus specific gravity of aluminum is 2.7 ÷ 1 = 2.7 (which has the same value with density)

Density of Plastics

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Plastic Material Density(g/cm3) / Specific Gravity
ABS 1.06
ABS Fire Retardant 1.15 - 1.20
ABS High Heat 1.10 - 1.15
ABS High Impact 1.00 - 1.10
ABS/PC 1.10 - 1.15
ABS/PC + 20% GF 1.25
ABC/PC Fire Retardant 1.17 - 1.19
AS 1.08
ASA 1.05 - 1.07
ASA/PC 1.15
ASA/PC Fire Retardant 1.25
ASA/PVC 1.20
CA 1.22 - 1.34
CAB 1.15 - 1.22
CP 1.17 - 1.24
COC 1.01 - 1.03
CPVC
1.50 - 1.55
ETFE 1.70
EVA 0.92 - 0.94
EVOH 1.10 - 1.20
FEP 2.10 - 2.20
HDPE 0.94 - 0.97
HIPS 1.03 - 1.06
LCP 1.40
LCP + CF 1.50
LCP + GF 1.50 - 1.80
LCP + MF 1.50 - 1.80
LDPE 0.92 - 0.94
LLDPE 0.92 - 0.95
MABS 1.08
MDPE 0.93 - 0.94
PA11 + 30% GF 1.25 - 1.27
PA11 Conductive 1.13
PA11-Flexible 1.03 - 1.05
PA11-Rigid 1.02 - 1.03
PA12 Conductive 1.14
PA12 + GF 1.22 - 1.42
PA12 - Flexible 1.01 - 1.04
PA12 - Rigid 1.01
PA46 1.17 - 1.19
PA46 + 30% GF 1.42 - 1.44
PA6 1.12 - 1.14
PA6-10 1.09 - 1.10
PA66 1.13 - 1.15
PA66 + 30% GF 1.37
PA66 + 30% MF 1.35 - 1.38
PA66 IM 1.05 - 1.10
PA66 IM + 15-30% GF 1.25 - 1.35
PAI 1.40
PAI + 30% GF 1.60
PAI LOW FRICTION 1.40 - 1.50
PAN 1.10 - 1.15
PAR 1.20 - 1.26
PAR + 30-60% GF 1.43 - 1.77
PBT 1.30 - 1.40
PBT + 30% GF 1.50 - 1.60
PC 1.20
PC + 20-40% GF 1.35 - 1.52
PC + 20-40% GF FLAME RETARDANT 1.40 - 1.50
PC HIGH HEAT 1.15 - 1.20
PC/PBT 1.17 - 1.30
PC/PBT + GF 1.30 - 1.59
PCL 1.14
PCTFE 2.10 - 2.20
PE + 30% GF 1.20 - 1.28
PE/TPS 1.00 - 1.05
PEEK 1.26 - 1.32
PEEK + 30% CF 1.40 - 1.44
PEEK + 30% GF 1.49 - 1.54
PEI 1.27 - 1.30
PEI + 30% GF 1.50 - 1.60
PEI + MF 1.40 - 1.50
PEKK LOW CRYSTALLINITY GRADE 1.27 - 1.28
PESU 1.37 - 1.46
PESU + 10-30% GF 1.50 - 1.60
PET 1.30 - 1.40
PET + 30% GF 1.50 - 1.60
PET + 30/35% GF IM 1.50
PETG 1.27 - 1.38
PFA 2.1 - 2.2
PGA 1.40 - 1.60
PHB 1.30 - 1.50
PI 1.31 - 1.43
PLA 1.23 - 1.25
PLA FIBER MELT SPINNING 1.23 - 1.25
PLA INJECTION MOLDING 1.24 - 1.26
PMMA 1.17 - 1.20
PMMA HIGH HEAT 1.15 - 1.25
PMMA IM 1.23 - 1.25
PMP 0.84
PMP + 30% GF 1.05
PMP MF 1.08 - 1.10
POM 1.41 - 1.42
POM IM 1.30 - 1.35
POM LF 1.40 - 1.54
POM MF 1.50 - 1.60
PP Copolymer 0.90 - 0.91
PP Homopolymer 0.90 - 0.91
PP + 10-20% GF 0.97 - 1.05
PP + 10-40% MF 0.97 - 1.25
PP + 10-40% TF 0.97 - 1.25
PP + 30-40% GF 1.10 - 1.23
PP IM 0.88 - 0.91
PPA 1.11 - 1.20
PPA + 33% GF 1.40 - 1.50
PPA + 45% GF 1.58 - 1.60
PPE 1.04 - 1.10
PPE + 30% GF 1.26 - 1.28
PPE FR 1.06 - 1.10
PPE IM 1.00 - 1.10
PPE MF 1.20 - 1.25
PPS 1.35
PPS + 20-30% GF 1.40 - 1.60
PPS + 40% GF 1.60 - 1.70
PPS CONDUCTIVE 1.40 - 1.80
PPS + GF or MF 1.80 - 2.00
PPSU 1.29 - 1.30
PS 1.05
PS Crystal 1.04 - 1.05
PS + 30% GF 1.25
PS HIGH HEAT 1.04 - 1.05
PSU 1.24 - 1.25
PSU + 30% GF 1.40 - 1.50
PSU MF 1.50 - 1.60
PTFE 2.10 - 2.20
PTFE + 25% GF 2.20 - 2.30
PVC PLASTICIZED 1.30 - 1.70
PVC RIGID 1.35 - 1.50
PVC + 20% GF 1.45 - 1.50
PVDC 1.60 - 1.75
PVDF 1.70 - 1.80
SAN 1.06 - 1.10
SAN + 20% GF 1.20 - 1.40
SMA 1.05 - 1.08
SMA + 20% GF 1.20
SMA FR V0 1.20
SMMA 1.05 - 1.13
SRP 1.19 - 1.21
TPS INJECTION MOULDING 1.40 - 1.65
TPS WATER RESISTANT 1.34 - 1.38
UHMWPE 0.93 - 0.95
XLPE 0.92 - 1.40

Remarks: Glass Fiber (GF), Carbon Fiber (CF), Mineral Fiber (MF), Impact Modified (IM), Low Friction (LF), Talc Filled (TF), Ultra High Molecular Weight Polyethylene (UHMWPE), Crosslinked Polyethylene (XLPE)

Density of Chemical Additives for Injection Molding

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Addictive
Density (g/cm3) / Specific Gravity
Glass Fiber (GF) 2.54
Tale 2.8
Carbon Fiber (CF) 2.7
Mica 2.6 - 3.8

Due to the different density of plastic, we can easily identify different plastics by "Buoyancy Test", for more information, please check out in related articles.

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