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Toughness


Calculating Toughness of Plastics Toughness of a plastic is measured by its resistance to impacts. It is the ability of a material to resist both fracture and deformation. One common way to discuss the toughness of a polymer is to examine the area underneath the stress - strain curve for the particular polymer.

In general, ‘Hardness’, ‘Toughness’ and ‘Strength’ are similar terms to use, but in material science they are three distinct properties yet also share some overlap. Here are the key differences:

  • Hardness is how well material holds together when friction is applied 

  • Strength is how much force is required before the material deforms. It tells us about the amount of load a material can bear 

  • Toughness is the ability of a material to resist breaking when force is applied 

Toughness is the combination of strength and ductility

To be tough, a material must exhibit both fairly good strength and ductility to resist cracking and deformation under impact loading.
Impact test signifies toughness, or impact strength, of a material that is the
ability of material to absorb energy during plastic deformation. This energy absorption is directly related to the brittleness of the material. Results of impact tests are expressed in terms of either:

  • Amount of energy absorbed (Nm) or 
  • Amount of energy absorbed per unit cross sectional area (Nm/cm2)

Applications include:
  • Measure of the energy required to crack a material
  • Screen materials for impact developments
  • Define uses of materials in automotive applications


Check out more on toughness:

  » Toughness values of Several Plastics
  » How to Calculate the toughness of plastic


How to Measure Toughness of a polymer?


The energy absorption, or toughness, of a material is measured by various techniques and two most commonly used methods are: Izod and Charpy Test.

The two methods are based on common principle of applying the load at high rate and measuring the amount of energy absorbed (Kg/m or Joule) in breaking the sample due to impact. However, there are some difference also in these two methods in terms of:

  • Sample size and shape, 
  • Method of holding of the sample and
  • Maximum energy content of pendulum that hits the sample during test

Toughness Test Sample Holding
Izod Held vertically on anvil as cantilever Cantilever type and notch faces the pendulum
Charpy Held horizontally on anvil as simply supported beam Simply supported type and notch is opposite side of pendulum impact (not facing the pendulum)

Since most of the engineering components are invariably designed with notch and stress raisers, therefore, it becomes important to know the behavior of material with notch under impact loading.

  • Hence, toughness test is usually conducted using sample with notch. 
  • Moreover, un-notched samples can also be used for the toughness test and the results are expresses accordingly. 

These tests can be used as a quick and easy quality control check to determine if a material meets specific impact properties or to compare materials for general toughness.

Values of toughness are not directly used for design purpose, but these only indicate the ability of the material to withstand against shock/impact load. These tests are useful for comparing the resistance to impact loading of different materials or the same material in different processing conditions such as heat treatment, procedure and mechanical working etc.

The toughness of polymers, or resistance to impact, varies with the:

  • Molecular structure, 
  • surrounding temperature and 
  • type of stress applications

Case must be taken in relating flexibility to toughness, but generally, a more rubbery character gives higher elongation at break and better impact resistance values, although such materials would have lower stiffness.


Factors Affecting Toughness of Plastics


  » Degree of Crystallinity - Greater the crystallinity, the harder the polymer
  » Temperature - Change in behavior at ductile - brittle transition temperature
  » Long Chain Branches - Long chain branches may increase the polymer toughness


Toughness Values of Several Plastics


We have selected Notched Izod Impact test performed at room temperature (23°C for ISO and 73°F for ASTM) for different polymers. As discussed above, it measures the energy to be applied to a notched standardized sample to break it.

The result of the Izod test is reported in energy lost during the impact per unit of specimen thickness (such as ft-lb/in or J/cm) at the notch. Tests results, especially in Europe, may be reported as energy lost per unit cross-sectional area at the notch (J/m2 or ft-lb/in2).

Test methods used to measure Notched Izod Impact (Or notch sensitivity) in plastics are ASTM D256 and ISO 180.

Find commercial grades matching your target using "Property Search - Izod Impact, Notched" filter in Omnexus Plastics Database:


Omnexus Plastics Database - Property Search



Click to find polymer you are looking for:
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Polymer Name Min Value (J/m2) Max Value (J/m2)
ABS - Acrylonitrile Butadiene Styrene 200.0 215.0
ABS Flame Retardant 70.0 350.0
ABS High Heat 100.0 350.0
ABS High Impact 300.0 500.0
ABS/PC Blend - Acrylonitrile Butadiene Styrene/Polycarbonate Blend 400.0 600.0
ABS/PC Blend 20% Glass Fiber 73.0 76.0
ABS/PC Flame Retardant 250.0 700.0
ASA - Acrylonitrile Styrene Acrylate 100.0 600.0
ASA/PC Blend - Acrylonitrile Styrene Acrylate/Polycarbonate Blend 600.0 700.0
ASA/PC Blend - Flame Retardant 400.0 500.0
ASA/PVC Blend - Acrylonitrile Styrene Acrylate/Polyvinyl Chloride Blend 300.0 600.0
CA - Cellulose Acetate 50.0 400.0
CAB - Cellulose Acetate Butyrate 50.0 500.0
CP - Cellulose Proprionate 25.0 999.0
CPVC - Chlorinated Polyvinyl Chloride 50.0 250.0
ETFE - Ethylene Tetrafluoroethylene 999.0 999.0
EVA - Ethylene Vinyl Acetate 999.0 999.0
EVOH - Ethylene Vinyl Alcohol 50.0 90.0
FEP - Fluorinated Ethylene Propylene 999.0 999.0
HDPE - High Density Polyethylene 20.0 220.0
HIPS - High Impact Polystyrene 50.0 350.0
HIPS Flame Retardant V0 100.0 150.0
Ionomer (Ethylene-Methyl Acrylate Copolymer) 500.0 999.0
LCP - Liquid Crystal Polymer 70.0 450.0
LCP Carbon Fiber-reinforced 70.0 100.0
LCP Glass Fiber-reinforced 80.0 300.0
LCP Mineral-filled 50.0 600.0
LDPE - Low Density Polyethylene 999.0 999.0
LLDPE - Linear Low Density Polyethylene 54.0 999.0
MABS - Transparent Acrylonitrile Butadiene Styrene 60.0 100.0
PA 46 - Polyamide 46 30.0 250.0
PA 46, 30% Glass Fiber 145.0 155.0
PA 6 - Polyamide 6 50.0 160.0
PA 6-10 - Polyamide 6-10 70.0 999.0
PA 66 - Polyamide 6-6 50.0 150.0
PA 66, 30% Glass Fiber 130.0 160.0
PA 66, 30% Mineral filled 40.0 200.0
PA 66, Impact Modified, 15-30% Glass Fiber 150.0 270.0
PA 66, Impact Modified 70.0 999.0
PAI - Polyamide-Imide 100.0 150.0
PAI, 30% Glass Fiber 70.0 80.0
PAI, Low Friction 50.0 80.0
PAN - Polyacrylonitrile 130.0 480.0
PAR - Polyarylate 70.0 290.0
PARA (Polyarylamide), 30-60% glass fiber 70.0 120.0
PBT - Polybutylene Terephthalate 27.0 999.0
PBT, 30% Glass Fiber 50.0 90.0
PC (Polycarbonate) 20-40% Glass Fiber 90.0 200.0
PC (Polycarbonate) 20-40% Glass Fiber Flame Retardant 90.0 110.0
PC - Polycarbonate, high heat 80.0 650.0
PC/PBT Blend - Polycarbonate/Polybutylene Terephthalate Blend 50.0 960.0
PC/PBT blend, Glass Filled 90.0 190.0
PCTFE - Polymonochlorotrifluoroethylene 130.0 250.0
PE - Polyethylene 30% Glass Fiber 60.0 80.0
PEEK - Polyetheretherketone 80.0 94.0
PEEK 30% Carbon Fiber-reinforced 85.0 120.0
PEEK 30% Glass Fiber-reinforced 95.0 130.0
PEI - Polyetherimide 50.0 60.0
PEI, 30% Glass Fiber-reinforced 90.0 100.0
PEI, Mineral Filled 40.0 60.0
PESU - Polyethersulfone 70.0 100.0
PESU 10-30% glass fiber 55.0 90.0
PET - Polyethylene Terephthalate 140.0 140.0
PET, 30% Glass Fiber-reinforced 70.0 130.0
PET, 30/35% Glass Fiber-reinforced, Impact Modified 100.0 230.0
PETG - Polyethylene Terephthalate Glycol 50.00 50.00
PFA - Perfluoroalkoxy 10.0 35.0
PI - Polyimide 60.0 112.0
PMMA - Polymethylmethacrylate/Acrylic 10.0 25.0
PMMA (Acrylic) High Heat 10.0 25.0
PMMA (Acrylic) Impact Modified 20.0 130.0
PMP - Polymethylpentene 100.0 150.0
PMP 30% Glass Fiber-reinforced 30.0 80.0
PMP Mineral Filled 30.0 80.0
POM - Polyoxymethylene (Acetal) 60.0 120.0
POM (Acetal) Impact Modified 90.0 250.0
POM (Acetal) Low Friction 10.00 70.00
POM (Acetal) Mineral Filled 25.0 60.0
PP - Polypropylene 10-20% Glass Fiber 50.0 145.0
PP, 10-40% Mineral Filled 38.0 110.0
PP, 10-40% Talc Filled 30.0 200.0
PP, 30-40% Glass Fiber-reinforced 45.0 160.0
PP (Polypropylene) Copolymer 60.0 500.0
PP (Polypropylene) Homopolymer 20.0 60.0
PP, Impact Modified 110.0 999.0
PPA - Polyphthalamide 960.0 1065.0
PPE - Polyphenylene Ether 130.0 300.0
PPE, 30% Glass Fiber-reinforced 90.0 130.0
PPE, Flame Retardant 200.0 300.0
PPE, Impact Modified 150.0 400.0
PPE, Mineral Filled 150.0 200.0
PPS - Polyphenylene Sulfide 5.0 25.0
PPS, 20-30% Glass Fiber-reinforced 35.0 100.0
PPS, 40% Glass Fiber-reinforced 60.0 100.0
PPS, Conductive 40.0 80.0
PPS, Glass fiber & Mineral-filled 25.0 70.0
PPSU - Polyphenylene Sulfone 133.0 690.0
PS (Polystyrene) 30% glass fiber 11.0 150.0
PS (Polystyrene) Crystal 20.0 25.0
PS, High Heat 20.0 25.0
PSU - Polysulfone 60.0 100.0
PSU, 30% Glass fiber-reinforced 55.0 90.0
PSU Mineral Filled 35.0 55.0
PTFE - Polytetrafluoroethylene 160.0 200.0
PTFE, 25% Glass Fiber-reinforced 150.0 150.0
PVC (Polyvinyl Chloride), 20% Glass Fiber-reinforced 50.0 100.0
PVC Rigid 20.0 110.0
PVDC - Polyvinylidene Chloride 20.0 50.0
PVDF - Polyvinylidene Fluoride 130.0 400.0
SAN - Styrene Acrylonitrile 20.0 30.0
SAN, 20% Glass Fiber-reinforced 50.0 150.0
SMA - Styrene Maleic Anhydride 20.0 100.0
SMA, 20% Glass Fiber-reinforced 100.0 140.0
SMA, Flame Retardant V0 40.0 70.0
SMMA - Styrene Methyl Methacrylate 18.0 160.0
SRP - Self-reinforced Polyphenylene 43.0 59.0
UHMWPE - Ultra High Molecular Weight Polyethylene 999.0 999.0
XLPE - Crosslinked Polyethylene 10.0 220.0

Find commercial grades matching your target using "Property Search - Izod Impact, Notched" filter in Omnexus Plastics Database:


Omnexus Plastics Database - Property Search

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