Toughness

1. What is toughness?
2. Which materials show good toughness?
3. How do hardness, toughness, and strength differ?
4. How does the toughness of polymers vary?
5. Which factors affect the toughness of plastics?
6. How to measure the toughness of plastics?
7. What are the types of impact tests?
8. What are the test methods to measure toughness?
9. What are the toughness values of several plastics?

What is toughness?

Toughness is the ability of a material to resist both fracture and deformation. The area underneath the stress-strain curve depicts the toughness of a polymer. The larger the area occupied higher will be the toughness of the material. To be tough, a material must exhibit both good strength and ductility.

Which materials show good toughness?

1. Thermoplastics with Good Toughness - View All Products
2. TPEs/TPVs with Good Toughness - View All Products
3. Rubbers with Good Toughness - View All Products
4. Thermosets with Good Toughness - View All Products

How do hardness, toughness, and strength differ?

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

• Hardness is how well material holds together when friction is applied. Discover more about hardness property here »


• 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.

How does the toughness of polymers vary?

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

• Molecular structure,
• Surrounding temperature, and
• Type of stress applications.

A 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.

Which factors affect the toughness of plastics?

The factors that affect the toughness of plastics are:

  » 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.

How to measure the toughness of plastics?

The toughness of plastics is measured by their resistance to impacts. The impact test is the ability of a material to absorb energy during plastic deformation. It signifies toughness or impact strength of a material. This energy absorption is 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 of impact test

• The measure of the energy required to crack a material
• Screen materials for impact developments
• Define uses of materials in automotive applications

What are the types of impact tests?

The two most common methods to determine toughness include: Izod and Charpy Test.

Key principle

These impact methods are based on the common principle of:

• applying the load at a high rate, and
• measuring the amount of energy absorbed (Kg/m or Joule) in breaking the sample due to impact.

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)

Description of Charpy and Izod Impact Tests
(Source: ResearchGate)

Differences between izod and charpy tests

Some differences between these two methods are in terms of:

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

Notched and unnotched test

Most of the engineering components are designed with notch and stress raisers. Thus, it becomes important to know the behavior of the material with a notch under impact loading.

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

a) Notched and Unnotched Charpy Test; b) Notched and Unnotched Izod Test
(Source: ScienceDirect)
These tests can be used as a quick and easy quality control check. They determine if a material meets specific impact properties or compare materials for toughness.

Key advantages of impact tests

Values of toughness are not directly used for design purposes. They only indicate the ability of the material to withstand 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. These conditions can be heat treatment, procedure, mechanical working, etc.

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

What are the test methods to measure toughness?

Test methods used to measure Notched Izod Impact (or notch sensitivity) and Charpy Impact in plastics are:

• ASTM D256-10(2018): Plastics — Determination of Izod pendulum impact resistance


• ISO 180:2019: Plastics — Determination of Izod impact strength


• ISO 179-1:2010: Plastics — Determination of Charpy impact properties — Part 1: Non-instrumented impact test


• ISO 179-2:2020: Plastics — Determination of Charpy impact properties — Part 2: Instrumented impact test

Source: Tinius Olsen

What are the toughness values of several plastics?

Click to find polymer you are looking for:
A-C     |      E-M     |      PA-PC     |      PE-PL     |      PM-PP     |      PS-X

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 - Polyamide 6-6	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