Strength at Break (Tensile)

What is the definition of tensile strength?
What are the three types of tensile strength?
What is tensile strength at break?
What are the units of tensile strength?
Which materials show high tensile strength?
How stress-strain curve measures the tensile strength?
What is the significance of tensile properties?
What are the factors affecting the tensile strength?
What are the test methods to measure tensile properties?
What are the tensile strength at break values of several plastics?

What is the definition of tensile strength?

Tensile strength is the ability of plastic material to withstand a maximum amount of tensile stress without failure. The stress occurs while the material is being pulled or stretched. It is the point when a material goes from elastic to plastic deformation.

While removing the stress, the plastic material undergoes:

Elastic deformation: The material returns to its original dimensions. Deformation is reversible and non-permanent. Valid for small strains.
Plastic deformation: The material does not return to its original dimensions. This process is permanent and irreversible.

What are the three types of tensile strength?

There are three types of tensile strength:

Yield strength (A) - The stress a material can withstand without permanent deformation. Know more »
Ultimate strength (B) - The maximum stress a material can withstand
Breaking strength (C) - The stress coordinate on the stress-strain curve at the point of rupture

Stress-strain curve showing tensile strength at points Yield (A), Ultimate Strength (B) and Break (C)

In other words, materials first deform elastically - when you release the stress they return to their original shape. Then with more force they deform plastically, this is yield - when you release the stress they have permanently been stretched into a new shape. Finally, they break; this is ultimately tensile stress or breaking point.

Tensile strength is often referred to as ultimate tensile strength

What is tensile strength at break?

Tensile strength (TS) at break measures the maximum stress a plastic specimen can withstand while being stretched before breaking. Some materials can break sharply (brittle failure). While others will deform or elongate before breaking. It is measured as the tensile or compressive load required to fracture something. It is also known as break strength.

Hence, it is one of the important mechanical properties for:

Material evaluation
Quality control
Structure design
Modeling, and
Failure analysis

What are the units of tensile strength?

Tensile strength is measured in units of force per cross-sectional area. In the International System, the units of Tensile Strength are:

Pascal (Pa)
Megapascals (MPa)
Gigapascals (GPa)

In the US, the commonly used units for convenience when measuring tensile strengths are:

Pounds-force per square inch (lbf/in² or psi)
Kilo-pounds per square inch (kpsi)

Which materials show high tensile strength?

Thermoplastics with High Tensile Strength – View Product List

Thermoplastic Elastomers with High Tensile Strength – View Product List

Thermosets with High Tensile Strength – View Product List

Rubbers with High Tensile Strength – View Product List

How stress-strain curve measures the tensile strength?

When a stretching force or tensile force is applied to an object, it extends. Its behavior can be obtained using a stress-strain curve in the elastic deformation region. This is known as Hooke’s Law. The extension that a force produces depends on the plastic material and dimensions of the object.

Definition of stress

Stress is defined as the force per unit area of plastic. The units of stress are N/m² or Pa.

σ = F/A

where,

σ is the stress,
F is the force, and
A is the cross-sectional area of the sample.

Definition of strain

Strain is defined as extension per unit length. And, since it is a ratio of lengths, the strain has no units.

ε = ΔL/L0; ΔL = L-L0

where,

ε is the strain,
L0 is the original length of a bar being stretched,
L is the length after it has been stretched, and
ΔL is the extension of the bar, the difference between these two lengths.

Stress-Strain Plots for a Typical Elastomer, Flexible Plastics, Rigid Plastic, and Fiber
(Source: Principles of Polymerization, Fourth Edition, George Odian)

What is the significance of tensile properties?

Tensile properties provide useful data for plastics engineering design purposes.
They are frequently included in material specifications to ensure quality.
They are often measured during the development of new materials and processes. This is done to compare different materials and processes.
They predict the behavior of a material under various forms of loading other than uniaxial tension.

What are the factors affecting the tensile strength of plastics?

The strength of polymers is further governed by:

Molecular weight

The strength of the polymer rises with the increase in molecular weight. It reaches the saturation level at some value of the molecular weight.

At lower molecular weight: The polymer chains are loosely bonded by weak van der Waals forces. The chains can move easily and are responsible for low strength. Although crystallinity is present.
At higher molecular weight: The polymer chains become large. Hence, crosslinking takes place giving strength to the polymer.

Crosslinking between polymer chains

The crosslinking restricts the motion of the chains. This increases the strength of the polymer.

Crystallinity

The crystalline phase of the polymer increases the tensile strength. Hence the intermolecular bonding is more significant. Therefore, the polymer deformation can result in higher strength leading to oriented chains.

Other factors that impact the tensile strength values of plastics

Velocity of testing,
Orientation level of fibers,
Temperature,
Filler content, etc.

What are the test methods to measure tensile properties of plastics?

In general, “tensile test methods” measure the modulus of elasticity of materials. The common methods used are:

ASTM D638 - Standard Test Method for Tensile Properties of Plastics
ISO 527-1:2012 - Determination of tensile properties. General principles

These methods determine the tensile properties of plastics and plastic composites. This is done under defined conditions that can range from:

pretreatment,
temperature,
humidity, and
machine speed

The test specimens are in the form of a standard dumbbell shaped.

For ASTM D638, the test speed is determined by the material specification. For ISO 527, the test speed is typically 5 or 50 mm/min for measuring strength and elongation, and 1 mm/min for measuring modulus.

Watch this Interesting Video on Micro Tensile Strength Test of Plastics per ASTM D638
(Source: ADMET)

Apart from Tensile strength at break, the tensile test results can also calculate:

What are the tensile strength at break values of several plastics?

Polymer Name	Min Value (MPa)	Max Value (MPa)
ABS - Acrylonitrile Butadiene Styrene	29.8	43.0
ABS Flame Retardant	30.0	50.0
ABS High Heat	30.0	60.0
ABS High Impact	30.0	45.0
ABS/PC Blend - Acrylonitrile Butadiene Styrene/Polycarbonate Blend	40.0	50.0
ABS/PC Blend 20% Glass Fiber	75.0	80.0
ABS/PC Flame Retardant	40.0	55.0
Amorphous TPI Blend, Ultra-high heat, Chemical Resistant (High Flow)	105.0	105.0
Amorphous TPI Blend, Ultra-high heat, Chemical Resistant (Standard Flow)	160.0	160.0
Amorphous TPI, High Heat, High Flow, Lead-Free Solderable, 30% GF	147.0	147.0
Amorphous TPI, High Heat, High Flow, Transparent, Lead-Free Solderable (High Flow)	74.0	74.0
Amorphous TPI, High Heat, High Flow, Transparent, Lead-Free Solderable (Standard Flow)	70.0	70.0
Amorphous TPI, Highest Heat, Chemical Resistant, 260C UL RTI	119.0	119.0
Amorphous TPI, Moderate Heat, Transparent	78.0	78.0
Amorphous TPI, Moderate Heat, Transparent (Food Contact Approved)	78.0	78.0
Amorphous TPI, Moderate Heat, Transparent (Mold Release grade)	78.0	78.0
Amorphous TPI, Moderate Heat, Transparent (Powder form)	78.0	78.0
ASA - Acrylonitrile Styrene Acrylate	47.0	56.0
ASA/PC Blend - Acrylonitrile Styrene Acrylate/Polycarbonate Blend	45.0	50.0
ASA/PC Flame Retardant	48.0	48.0
ASA/PVC Blend - Acrylonitrile Styrene Acrylate/Polyvinyl Chloride Blend	45.0	50.0
CA - Cellulose Acetate	24.0	52.0
CAB - Cellulose Acetate Butyrate	18.0	48.0
CP - Cellulose Proprionate	14.0	50.0
COC - Cyclic Olefin Copolymer	46.0	63.0
CPVC - Chlorinated Polyvinyl Chloride	45.0	60.0
ETFE - Ethylene Tetrafluoroethylene	45.0	45.0
ECTFE	45.0	54.0
EVA - Ethylene Vinyl Acetate	7.0	30.0
EVOH - Ethylene Vinyl Alcohol	30.0	205.0
FEP - Fluorinated Ethylene Propylene	19.0	21.0
HDPE - High Density Polyethylene	30.0	40.0
HIPS - High Impact Polystyrene	20.0	45.0
HIPS Flame Retardant V0	15.0	30.0
Ionomer (Ethylene-Methyl Acrylate Copolymer)	11.0	37.0
LCP - Liquid Crystal Polymer	175.0	175.0
LCP Carbon Fiber-reinforced	190.0	240.0
LCP Glass Fiber-reinforced	160.0	220.0
LCP Mineral-filled	110.0	180.0
LDPE - Low Density Polyethylene	10.0	20.0
LLDPE - Linear Low Density Polyethylene	25.0	45.0
PA 11 - (Polyamide 11) 30% Glass fiber reinforced	80.0	136.0
PA 11, Conductive	37.0	37.0
PA 11, Flexible	43.0	59.0
PA 11, Rigid	37.0	58.0
PA 12 (Polyamide 12), Conductive	39.0	-
PA 12, Fiber-reinforced	72.0	145.0
PA 12, Flexible	50.0	56.0
PA 12, Glass Filled	37.0	50.0
PA 12, Rigid	56.0	69.0
PA 46 - Polyamide 46	65.0	85.0
PA 46, 30% Glass Fiber	128.0	132.0
PA 6 - Polyamide 6	50.0	95.0
PA 6-10 - Polyamide 6-10	50.0	65.0
PA 66 - Polyamide 6-6	50.0	95.0
PA 66, 30% Glass Fiber	100.0	125.0
PA 66, 30% Mineral filled	45.0	200.0
PA 66, Impact Modified, 15-30% Glass Fiber	90.0	120.0
PA 66, Impact Modified	40.0	50.0
Polyamide semi-aromatic	60.0	60.0
PAI - Polyamide-Imide	190.0	195.0
PAI, 30% Glass Fiber	210.0	210.0
PAI, Low Friction	125.0	165.0
PAN - Polyacrylonitrile	50.0	65.0
PAR - Polyarylate	25.0	65.0
PARA (Polyarylamide), 30-60% glass fiber	190.0	280.0
PBT - Polybutylene Terephthalate	40.0	50.0
PBT, 30% Glass Fiber	135.0	140.0
PC (Polycarbonate) 20-40% Glass Fiber	90.0	160.0
PC (Polycarbonate) 20-40% Glass Fiber Flame Retardant	90.0	140.0
PC - Polycarbonate, high heat	55.0	77.0
PC/PBT Blend - Polycarbonate/Polybutylene Terephthalate Blend Glass Filled	62.0	110.0
PCTFE - Polymonochlorotrifluoroethylene	32.0	40.0
PE - Polyethylene 30% Glass Fiber	52.0	63.0
PEEK - Polyetheretherketone	90.0	150.0
PEEK 30% Carbon Fiber-reinforced	200.0	220.0
PEEK 30% Glass Fiber-reinforced	150.0	180.0
PEI - Polyetherimide	90.0	100.0
PEI, 30% Glass Fiber-reinforced	150.0	160.0
PEI, Mineral Filled	90.0	100.0
PEKK (Polyetherketoneketone), Low Crystallinity Grade	89.5	89.5
PESU - Polyethersulfone	70.0	90.0
PESU 10-30% glass fiber	75.0	140.0
PET - Polyethylene Terephthalate	45.0	70.0
PET, 30% Glass Fiber-reinforced	140.0	160.0
PET, 30/35% Glass Fiber-reinforced, Impact Modified	100.0	110.0
PETG - Polyethylene Terephthalate Glycol	40.0	40.0
PE-UHMW - Polyethylene -Ultra High Molecular Weight	39.0	49.0
PFA - Perfluoroalkoxy	27.0	30.0
PGA - Polyglycolides	68.9	68.9
PHB - Polyhydroxybutyrate	25.0	27.0
PHB-V(5% valerate)	35.0	37.0
PI - Polyimide	72.0	120.0
PLA - Polylactide	52.0	54.0
PLA - Polylactide High heat films	102.2	104.2
PMMA - Polymethylmethacrylate/Acrylic	38.0	70.0
PMMA (Acrylic) High Heat	65.0	79.0
PMMA (Acrylic) Impact Modified	35.0	65.0
PMP - Polymethylpentene	16.0	18.0
PMP 30% Glass Fiber-reinforced	60.0	68.0
PMP Mineral Filled	17.0	18.0
Polyamide 66 (Nylon 66)/Carbon Fiber, Long, 30% Filler by Weight	290.0	290.0
Polyamide 66 (Nylon 66)/Carbon Fiber, Long, 40% Filler by Weight	305.0	305.0
Polyamide 66 (Nylon 66)/Glass Fiber, Long, 40% Filler by Weight	230.0	230.0
Polyamide 66 (Nylon 66)/Glass Fiber, Long, 40% Filler by Weight	210.0	210.0
Polyamide 66 (Nylon 66)/Glass Fiber, Long, 50% Filler by Weight	270.0	270.0
Polyamide 66 (Nylon 66)/Glass Fiber, Long, 50% Filler by Weight	230.0	230.0
Polyamide 66 (Nylon 66)/Glass Fiber, Long, 60% Filler by Weight	270.0	270.0
Polyamide 66 (Nylon 66)/Glass Fiber, Long, 60% Filler by Weight	250.0	250.0
Polypropylene Homopolymer (PP Homopolymer)/Glass Fiber, Long, 30% Filler by Weight	120.0	120.0
Polypropylene Homopolymer (PP Homopolymer)/Glass Fiber, Long, 40% Filler by Weight	130.0	130.0
Polypropylene Homopolymer (PP Homopolymer)/Glass Fiber, Long, 40% Filler by Weight	120.0	120.0
Polypropylene Homopolymer (PP Homopolymer)/Glass Fiber, Long, 50% Filler by Weight	130.0	130.0
Polypropylene Homopolymer (PP Homopolymer)/Glass Fiber, Long, 50% Filler by Weight	130.0	130.0
POM - Polyoxymethylene (Acetal)	60.0	70.0
POM (Acetal) Impact Modified	45.0	60.0
POM (Acetal) Low Friction	50.0	70.0
POM (Acetal) Mineral Filled	50.0	75.0
PP - Polypropylene 10-20% Glass Fiber	35.0	56.0
PP, 10-40% Mineral Filled	18.0	24.0
PP, 10-40% Talc Filled	21.0	28.0
PP, 30-40% Glass Fiber-reinforced	42.0	70.0
PP (Polypropylene) Copolymer	30.0	35.0
PP (Polypropylene) Homopolymer	20.0	40.0
PP, Impact Modified	23.0	35.0
PPA - Polyphthalamide	85.0	85.0
PPA, 30% Mineral-filled	79.0	81.0
PPA, 33% Glass Fiber-reinforced	192.0	194.0
PPA, 33% Glass Fiber-reinforced – High Flow	162.0	163.0
PPA, 45% Glass Fiber-reinforced	227.0	229.0
PPE - Polyphenylene Ether	45.0	60.0
PPE, 30% Glass Fiber-reinforced	100.0	130.0
PPE, Flame Retardant	45.0	55.0
PPE, Impact Modified	45.0	55.0
PPE, Mineral Filled	65.0	75.0
PPS - Polyphenylene Sulfide	50.0	80.0
PPS, 20-30% Glass Fiber-reinforced	130.0	150.0
PPS, 40% Glass Fiber-reinforced	120.0	150.0
PPS, Conductive	60.0	140.0
PPS, Glass fiber & Mineral-filled	60.0	150.0
PPSU - Polyphenylene Sulfone	75.8	76.0
PS (Polystyrene) 30% glass fiber	70.0	70.0
PS (Polystyrene) Crystal	35.0	60.0
PS, High Heat	40.0	60.0
PSU - Polysulfone	70.0	80.0
PSU, 30% Glass fiber-reinforced	100.0	125.0
PSU Mineral Filled	65.0	70.0
PTFE - Polytetrafluoroethylene	0.0	10.0
PTFE, 25% Glass Fiber-reinforced	15.0	20.0
PVC (Polyvinyl Chloride), 20% Glass Fiber-reinforced	60.0	90.0
PVC, Plasticized	7.0	25.0
PVC, Plasticized Filled	10.0	25.0
PVC Rigid	35.0	60.0
PVDC - Polyvinylidene Chloride	20.0	35.0
PVDF - Polyvinylidene Fluoride	40.0	50.0
SAN - Styrene Acrylonitrile	65.0	85.0
SAN, 20% Glass Fiber-reinforced	100.0	120.0
SMA - Styrene Maleic Anhydride	35.0	55.0
SMA, 20% Glass Fiber-reinforced	56.0	75.0
SMA, Flame Retardant V0	20.0	25.0
SMMA - Styrene Methyl Methacrylate	30.0	60.7
SRP - Self-reinforced Polyphenylene	159.0	207.0
TPS/PE - Thermoplastic Starch/ Polyethylene Blend (30 micron films tested)	20.0	20.0
XLPE - Crosslinked Polyethylene	11.0	32.0

Disclaimer: all data and information obtained via the Polymer Selector including but not limited to material suitability, material properties, performances, characteristics and cost are given for information purpose only. Although the data and information contained in the Polymer Selector are believed to be accurate and correspond to the best of our knowledge, they are provided without implied warranty of any kind. Data and information contained in the Polymer Selector are intended for guidance in a polymer selection process and should not be considered as binding specifications. The determination of the suitability of this information for any particular use is solely the responsibility of the user. Before working with any material, users should contact material suppliers in order to receive specific, complete and detailed information about the material they are considering. Part of the data and information contained in the Polymer Selector are genericised based on commercial literature provided by polymer suppliers and other parts are coming from assessments of our experts.

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