- What is ductile/brittle transition temperature (DBTT)?
- Which polymer materials are ductile and brittle?
- What factors influence ductile to brittle transition of polymers?
- What are the applications of ductile/brittle transition temperature?
- Which instrument measures ductile/brittle transition temperature?
- What test methods measure ductile/brittle transition temperature?
- What are ductile/brittle transition temperature values of several plastics?
What is ductile/brittle transition temperature (DBTT)?
It is the transition temperature below which a ductile plastic specimen becomes brittle. This is not a specific temperature. It is rather a temperature spreading over the 10°C range. DBTT is expressed in °C.
In the stress-strain curve, brittle materials follow a straight path. Here we can see little or no plastic deformation. Whereas for ductile materials there is a significant plastic deformation under load.
The graph below depicts the area covered by brittle and ductile materials. Brittle materials cover less area as they absorb low energy during fracture. While ductile materials cover a larger area and absorb high energy during fracture.
Ductile and Brittle Materials in Terms of Energy
Source: ResearchGate
Which polymer materials are ductile and brittle?
Complete range of polymers that are ductile
Complete range of polymers that are brittle
What factors influence ductile to brittle transition of polymers?
1. Effect of temperature on polymer structure
The impact behavior of plastic materials depends upon the temperature.
- At high temperatures, materials are more ductile. Thus, they have high impact toughness.
- At low temperatures, some plastics that would be ductile at room temperature become brittle. This is because a decrease in temperature leads to less mobility. This transition is marked more in amorphous polymers near their glass transition temperature (Tg).
Ductile Brittle Transition Temperature Curve
Source: ResearchGate
Note: On the cooling of polymer, the DBTT may not correspond to the DBTT observed on heating of the polymer.
a. Effect of temperature on amorphous polymers
An increase in temperature changes the state of the
amorphous polymers. This, in turn, leads to a change in their tensile behavior. At low temperatures, the
polymers are brittle. As the temperature increases, they become tougher. This happens until they reach the ductile-brittle transition. Above this transition temperature
polymers become ductile. They can exhibit necking. A further increase in temperature produces a rubber-like behavior. This is displayed until mechanical strength breaks down.
Examples of amorphous polymers are:
- polycarbonate (PC),
- general-purpose polystyrene (GPPS),
- polymethyl methacrylate (PMMA),
- polyvinyl chloride (PVC),
- acrylonitrile butadiene styrene (ABS), etc.
b. Effect of temperature on crystalline polymers
At low temperatures,
crystalline polymers behave like amorphous polymers. Hence, their DBTT is based on amorphous content. Thus, the more crystalline a material, the less sensitive it is to the changes brought by the amorphous content.
Examples of crystalline polymers are:
- polyolefins,
- polyether ether ketone (PEEK),
- polyethylene terephthalate (PET),
- acetal (POM), etc.
Note: Crystalline polymers are stronger. But, they are less ductile than amorphous polymers at the same temperature.
c. Effect of temperature on cross-linked polymers
Cross-linked polymers have the same mechanical properties as amorphous polymers. This is true as long as the crosslinking is light. As the crosslinking increases, the mechanical properties are modified. This makes the polymer insensitive to temperature changes. This happens at the extreme end of high crosslinking of the polymer.
Examples of cross-linked polymers are:
- polyester fiberglass,
- polyurethane (PU),
- vulcanized rubber,
- epoxy resins, etc.
2. Stress concentration & design features
Some of the features that tend to make the ductile polymer more brittle are:
- faster stressing,
- cyclic loading,
- triaxial tension
Brittle materials have higher
yield strength than the ductile materials, as depicted in the graph.
3. Crosslink density & addition of additives
An increase in crosslink density restricts molecule mobility. This makes the polymer more likely to be brittle. Changes in proportion in copolymers and blends can lead to changes in the balance of properties. As a result, toughness may suffer.
Plasticizers are used to increase
flexibility. But a decrease in plasticizer concentration (either deliberately or by migration) reduces ductility. Hard particulate fibers that are used to reinforce the polymer may impair the toughness of the composition. This reduces the
elongation at break.
4. Processing features
Melt processing to shape polymers may introduce several features which can promote embrittlement. For example:
- Development of anisotropy. This is due to the alignment of molecules or fibrous fillers,
- Inhomogeneity leads to the distribution of microstructure. This happens throughout the wall thickness of a product, or
- Residual stress by solidification. This happens from the melt during cooling.
Other contributing factors are
chemical contact, degradation, contamination, strain rate, etc.
What are the applications of ductile/brittle transition temperature?
Which instrument measures ductile/brittle transition temperature?
Drop weight impact tester
- It can test plastics under most environmental conditions within a temperature range between -70 °C and 150 °C.
- It can be integrated into an automatic feeding system. This allows the loading of 30 samples simultaneously.
- The samples remain at the desired temperature during testing. This ensures optimal accuracy and repeatability of results.
Source: Research Gate
Charpy impact tester
- It is the most popular method to test ductile to brittle transition temperature.
- It determines the amount of energy dissipated during the fracture of a material under severe loading condition.
- It enables to determine the amount of deformation a plastic can withstand before failure.
Source: Research Gate
What test methods measure ductile/brittle transition temperature?
The test methods used to measure ductile/brittle transition temperature are:
- ISO 6603-1— It determines the puncture impact behavior of rigid plastics. It involves non-instrumented impact testing.
- ISO 6603-2 — It determines the puncture impact behavior of rigid plastics. It involves instrumented impact testing.
What are ductile/brittle transition temperature 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 (°C) |
Max Value (°C) |
| ABS - Acrylonitrile Butadiene Styrene |
-25.00 |
-40.00 |
| ABS Flame Retardant |
-40.00 |
-20.00 |
| ABS High Heat |
-40.00 |
-20.00 |
| ABS High Impact |
-40.00 |
-20.00 |
| ASA/PVC Blend - Acrylonitrile Styrene Acrylate/Polyvinyl Chloride Blend |
0.00 |
8.00 |
| CA - Cellulose Acetate |
-30.00 |
-30.00 |
| ECTFE - Ethylene Chlorotrifluoroethylene |
-76.00 |
-76.00 |
| ETFE - Ethylene Tetrafluoroethylene |
-100.00 |
-100.00 |
| EVA - Ethylene Vinyl Acetate |
-69.00 |
-69.00 |
| FEP - Fluorinated Ethylene Propylene |
-150.00 |
-150.00 |
| HDPE - High Density Polyethylene |
-70.00 |
-70.00 |
| HIPS - High Impact Polystyrene |
-40.00 |
-20.00 |
| HIPS Flame Retardant V0 |
-40.00 |
-20.00 |
| Ionomer (Ethylene-Methyl Acrylate Copolymer) |
-110.00 |
-71.00 |
| LCP - Liquid Crystal Polymer |
-200.00 |
-50.00 |
| LCP Carbon Fiber-reinforced |
-200.00 |
-50.00 |
| LCP Glass Fiber-reinforced |
-200.00 |
-50.00 |
| LCP Mineral-filled |
-200.00 |
-50.00 |
| LDPE - Low Density Polyethylene |
-70.00 |
-70.00 |
| LLDPE - Linear Low Density Polyethylene |
-70.00 |
-70.00 |
| MABS - Transparent Acrylonitrile Butadiene Styrene |
-40.00 |
-40.00 |
| PA 66 - Polyamide 6-6 |
-80.00 |
-65.00 |
| PA 66, Impact Modified |
-105.00 |
-85.00 |
| PAI - Polyamide-Imide |
-196.00 |
-196.00 |
| PAR - Polyarylate |
-100.00 |
-95.00 |
| PBT - Polybutylene Terephthalate |
-40.00 |
-40.00 |
| PCTFE - Polymonochlorotrifluoroethylene |
-250.00 |
-250.00 |
| PE - Polyethylene 30% Glass Fiber |
-110.00 |
-110.00 |
| PEEK - Polyetheretherketone |
-65.00 |
-60.00 |
| PEEK 30% Carbon Fiber-reinforced |
-65.00 |
-65.00 |
| PEEK 30% Glass Fiber-reinforced |
-65.00 |
-70.00 |
| PESU - Polyethersulfone |
-98.00 |
-101.00 |
| PET - Polyethylene Terephthalate |
-40.00 |
-40.00 |
| PETG - Polyethylene Terephthalate Glycol |
-40.00 |
-40.00 |
| PFA - Perfluoroalkoxy |
-150.00 |
-150.00 |
| POM - Polyoxymethylene (Acetal) |
-40.00 |
-40.00 |
| POM (Acetal) Impact Modified |
-50.00 |
-40.00 |
| POM (Acetal) Low Friction |
-40.00 |
-40.00 |
| PP - Polypropylene 10-20% Glass Fiber |
-30.00 |
-5.00 |
| PP, 10-40% Mineral Filled |
-20.00 |
-5.00 |
| PP, 10-40% Talc Filled |
-20.00 |
-5.00 |
| PP, 30-40% Glass Fiber-reinforced |
-30.00 |
-5.00 |
| PP (Polypropylene) Copolymer |
-20.00 |
-10.00 |
| PP (Polypropylene) Homopolymer |
-20.00 |
-10.00 |
| PP, Impact Modified |
-40.00 |
20.00 |
| PPE - Polyphenylene Ether |
-50.00 |
-40.00 |
| PS (Polystyrene) Crystal |
20.00 |
20.00
|
| PS, High Heat |
20.00 |
20.00
|
| PSU - Polysulfone
|
-100.00 |
-100.00
|
| PTFE - Polytetrafluoroethylene
|
-200.00 |
-200.00
|
| PVC (Polyvinyl Chloride), 20% Glass Fiber-reinforced
|
-10.00 |
1.00
|
| PVC, Plasticized |
-40.00 |
-5.00
|
| PVC, Plasticized Filled
|
-40.00 |
-5.00
|
| PVC Rigid
|
-10.00 |
1.00 |
| PVDF - Polyvinylidene Fluoride
|
-62.00 |
-30.00
|
| SAN - Styrene Acrylonitrile |
20.00 |
20.00
|
| SAN, 20% Glass Fiber-reinforced
|
20.00 |
20.00
|