Heat Deflection Temperature of Plastics

1. What is heat deflection temperature (HDT)?
2. What are the two common loads used in HDT testing?
3. What materials show high heat deflection temperature?
4. What factors affect heat deflection temperature?
5. What are the applications of HDT?
6. How is HDT different from VST and Tg?
7. What test methods measure HDT of plastics?
8. What are the HDT values of several plastics?

What is heat deflection temperature (HDT)?

The heat deflection temperature (HDT) is a measure of the polymer’s resistance to distortion under a given load at an elevated temperature. In other words, it is the temperature at which a given polymer test bar will be bent by 0.25 mm under a given load. It is one of the two basic methods for assigning value to the performance of plastics at high temperatures. The value of 0.25 mm is an arbitrary value and has no specific significance.

The deflection temperature is also known as the:

• Deflection Temperature Under Load (DTUL),
• Heat Deflection Temperature Under Load (HDTUL), or
• Heat Distortion Temperature (HDT).

Note: Although tests performed at higher loads such as 5.0 MPa (725 psi) or 8.0 MPa (1160 psi) are occasionally encountered. They are not discussed here.

What are the two common loads used in HDT testing?

1. HDT @0.46 MPa (67 psi)

In the case of the HDT @0.46 MPa, the load value is 0.46 MPa (67 psi). Practically, the test bar is immersed in an oil bath that is heated. It leads to a continuous increase in the bath temperature (usually 2°C per minute).

HDT @0.46 MPa is often more accurate than HDT @1.8 MPa. The latter is useful when final parts are used under high mechanical loads.

2. HDT @1.8 MPa (264 psi)

In the case of the HDT @1.8 MPa, the load value is exactly 1820 kPa. It is commonly referenced as 1.8 MPa (264 psi). Practically, the test bar is immersed in an oil bath. It is heated in such a way that the increase of the bath temperature is continuous (usually 2°C per minute).

As compared to HDT @ 0.46 MPa, the HDT @1.8 MPa is often useful when predicting the maximum service temperature of parts submitted to high mechanical loads.

What materials show high heat deflection temperature?

1. Thermoplastics with High HDT — View All Products
2. Thermosets with High HDT — View All Products
3. Rubbers with High HDT — View All Products

What factors affect heat deflection temperature?

HDT measures the effect of temperature on stiffness. However, this is only an estimate and cannot predict how the final part will perform. Several factors influencing HDT are:

• Extrusion conditions — Higher orientation levels generally lead to higher HDT values.


• Morphology — Higher crystallinity levels mean higher HDT values.


• Filler loadings — An increase in filler loadings leads to an increase in the HDT. For e.g., reinforced and filled grades have high HDT (harder and stiffer under the heat).


• Presence of plasticizers — They decrease HDT by making the polymer softer and more flexible.


• Other factors that significantly influence the final thermal performance of an application are the:
  • Time of exposure to elevated temperature
  • Rate of temperature increase
  • Part geometry
  • Presence of base resin

What are the applications of HDT?

• It is used to screen materials for injection molding developments. Higher HDT means a faster molding process.
• It is used in many aspects of product design, engineering, and manufacture of products. This uses thermoplastic components.
• It is used for defining the use of materials in heating elements.
• It represents a value that can be used to compare different materials with each other.

Limitations that are associated with the determination of the HDT are that:

• the sample is not thermally isotropic and
• thick samples will contain a temperature gradient.

How is HDT different from VST and Tg?

Property Name	Description
Heat deflection temperature (HDT)	HDT is a measure of the stiffness of the material as the temperature increases. HDT test measures the temperature at which the specimen loses its “load-bearing” capability. A material can have only “one” HDT. HDT for material is affected by the addition of reinforcement, fillers, plasticizers, or any other type of additive.
Vicat softening temperature (VST)	The vicat test is used to identify a temperature at which a needle of specified dimensions penetrates a plastic specimen at a specified distance under a given load. It reveals the temperature at which the specimen loses its “stability-form” and softens. The vicat point is closer to the actual melting or softening point of the polymer. The Vicat number will typically be higher.
Glass transition temperature (Tg)	The glass transition temperature is the temperature at which a crystalline or semi-crystalline portion of the polymer melts. It then changes from an ordered structure to an amorphous structure. A material can have more than one Tg. One for each structurally distinct crystalline phase. Tg for material is very little affected by the addition of reinforcement, fillers, plasticizers, or any other type of additive. This is because it depends primarily on the polymer structure or morphology.

What test methods measure HDT of plastics?

• ASTM D 648 — It determines the deflection temperature for plastics under flexural load in the edgewise position. ASTM D 648 is equivalent to ISO 75.
• ISO 75 — It determines the temperature of deflection under load.

Procedure

• A test bar of a specific thickness and width is molded.
• The test sample is submerged in oil for which the temperature is raised at a uniform rate (usually 2°C per minute).
• The load is applied to the midpoint of the test bar that is supported near both ends.
• The temperature at which a bar of material is deformed 0.25mm is recorded as the HDT.

The test is performed using an apparatus as shown below.

Source: The Effect of Long Term Thermal Exposure on Plastics and Elastomers by Laurence W. McKeen

What are the HDT values of several plastics?

Click to find polymer you are looking for:
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Polymer Name	HDT @0.46 MPa		HDT @1.8 MPa
	Min Value (°C)	Max Value (°C)	Min Value (°C)	Max Value (°C)
ABS - Acrylonitrile Butadiene Styrene	68.0	100.0	88.0	100.0
ABS Flame Retardant	90.0	120.0	80.0	110.0
ABS High Heat	100.0	125.0	85.0	120.0
ABS High Impact	90.0	110.0	80.0	100.0
ABS/PC Blend - Acrylonitrile Butadiene Styrene/Polycarbonate Blend	105.0	130.0	100.0	110.0
ABS/PC Blend 20% Glass Fiber	130.0	130.0	115.0	115.0
ABS/PC Flame Retardant	90.0	110.0	80.0	110.0
Amorphous TPI Blend, Ultra-high heat, Chemical Resistant (High Flow)	263.0	263.0	240.0	240.0
Amorphous TPI Blend, Ultra-high heat, Chemical Resistant (Standard Flow)	260.0	260.0	238	238
Amorphous TPI, High Heat, High Flow, Lead-Free Solderable, 30% GF	257.0	257.0	254.0	254.0
Amorphous TPI, High Heat, High Flow, Transparent, Lead-Free Solderable (High Flow)	250.0	250.0	235.0	235.0
Amorphous TPI, High Heat, High Flow, Transparent, Lead-Free Solderable (Standard Flow)	250.0	250.0	235.0	235.0
Amorphous TPI, Highest Heat, Chemical Resistant, 260°C UL RTI	278.0	278.0	254.0	254.0
Amorphous TPI, Moderate Heat, Transparent	237.0	237.0	230.0	230.0
Amorphous TPI, Moderate Heat, Transparent (Food Contact Approved)	237.0	237.0	217.0	217.0
Amorphous TPI, Moderate Heat, Transparent (Mold Release grade)	237.0	237.0	230.0	230.0
Amorphous TPI, Moderate Heat, Transparent (Powder form)	237.0	237.0	230.0	230.0
ASA - Acrylonitrile Styrene Acrylate	80.0	95.0	75.0	80.0
ASA/PC Blend - Acrylonitrile Styrene Acrylate/Polycarbonate Blend	125.0	130.0	105.0	110.0
ASA/PC Flame Retardant	130.0	130.0	115.0	115.0
ASA/PVC Blend - Acrylonitrile Styrene Acrylate/Polyvinyl Chloride Blend	80.0	85.0	75.0	77.0
CA - Cellulose Acetate	50.0	100.0	44.0	90.0
CAB - Cellulose Acetate Butyrate	54.0	108.0	45.0	94.0
CP - Cellulose Proprionate	60.0	120.0	44.0	110.0
COC - Cyclic Olefin Copolymer	127.0	170.0	116.0	151.0
CPVC - Chlorinated Polyvinyl Chloride	100.0	120.0	85.0	110.0
ECTFE - Ethylene Chlorotrifluoroethylene	90.0	92.0	63.0	67.0
ETFE - Ethylene Tetrafluoroethylene	105.0	105.0	70.0	100.0
EVA - Ethylene Vinyl Acetate	37.0	37.0	23.0	23.0
EVOH - Ethylene Vinyl Alcohol	80.0	100.0	-	-
FEP - Fluorinated Ethylene Propylene	70.0	70.0	48.0	60.0
HDPE - High Density Polyethylene	60.0	90.0	45.0	60.0
HIPS - High Impact Polystyrene	80.0	100.0	75.0	80.0
HIPS Flame Retardant V0	85.0	100.0	80.0	85.0
Ionomer (Ethylene-Methyl Acrylate Copolymer)	34.0	75.0	40.0	40.0
LCP - Liquid Crystal Polymer	220.0	220.0	190.0	190.0
LCP Carbon Fiber-reinforced	260.0	260.0	220.0	220.0
LCP Glass Fiber-reinforced	250.0	280.0	210.0	240.0
LCP Mineral-filled	220.0	260.0	180.0	220.0
LDPE - Low Density Polyethylene	40.0	50.0	30.0	40.0
MABS - Transparent Acrylonitrile Butadiene Styrene	104.0	106.0	93.0	94.0
PA 11 - (Polyamide 11) 30% Glass fiber reinforced	180.0	180.0	170.0	170.0
PA 11, Conductive	137.0	137.0	46.0	46.0
PA 11, Flexible	86.0	130.0	40.0	50.0
PA 11, Rigid	60.0	145.0	46.0	53.0
PA 12 (Polyamide 12), Conductive	114.0	114.0	50.0	50.0
PA 12, Fiber-reinforced	173.0	175.0	151.0	170.0
PA 12, Flexible	89.0	125.0	46.0	50.0
PA 12, Glass Filled	155.0	160.0	60.0	68.0
PA 12, Rigid	92.0	135.0	45.0	55.0
PA 46 (Polyamide 46)	-	-	150.0	155.0
PA 46, 30% Glass Fiber	285.0	290.0	282.0	285.0
PA 6 - Polyamide 6	150.0	190.0	60.0	80.0
PA 6-10 - Polyamide 6-10	160.0	175.0	80.0	85.0
PA 66 - Polyamide 6-6	180.0	240.0	65.0	105.0
PA 66, 30% Glass Fiber	235.0	255.0	230.0	255.0
PA 66, 30% Mineral filled	229.0	231.0	178.0	182.0
PA 66, Impact Modified, 15-30% Glass Fiber	220.0	250.0	60.0	100.0
PA 66, Impact Modified	160.0	210.0	60.0	100.0
Polyamide semi-aromatic	110.0	150.0	88.0	135.0
PAI - Polyamide-Imide	-	-	275.0	280.0
PAI - 30% Glass fiber-reinforced	-	-	280.0	280.0
PAI -Low Friction	-	-	279.0	280.0
PAN - Polyacrylonitrile	70.0	80.0	66.0	72.0
PAR - Polyarylate	180.0	180.0	110.0	174.0
PARA - Polyarylamide 30-60% Glass Fiber-reinforced	-	-	230.0	230.0
PBT - Polybutylene Terephthalate	115.0	150.0	50.0	85.0
PBT, 30% Glass Fiber	215.0	250.0	195.0	225.0
PC (Polycarbonate) 20-40% Glass Fiber	140.0	155.0	140.0	150.0
PC (Polycarbonate) 20-40% Glass Fiber Flame Retardant	145.0	155.0	140.0	150.0
PC - Polycarbonate, high heat	150.0	190.0	140.0	180.0
PC/PBT Blend - Polycarbonate/Polybutylene Terephthalate Blend	91.0	118.0	60.0	121.0
PC/PBT blend, Glass Filled	135.0	215.0	121.0	193.0
PCTFE - Polymonochlorotrifluoroethylene	120.0	125.0	-	-
PE - Polyethylene 30% Glass Fiber	127.0	130.0	121	121
PEEK - Polyetheretherketone	-	-	150.0	160.0
PEEK - 30% Carbon Fiber-reinforced	-	-	230.0	315.0
PEEK - 30% Glass Fiber-reinforced	-	-	230.0	315.0
PEI - Polyetherimide	195.0	210.0	190.0	200.0
PEI, 30% Glass Fiber-reinforced	205.0	212.0	200.0	210.0
PEI, Mineral Filled	200.0	210.0	200.0	210.0
PESU - Polyethersulfone	205.0	212.0	195.0	203.0
PESU 10-30% glass fiber	215.0	221.0	210.0	216.0
PET - Polyethylene Terephthalate	75.0	115.0	65.0	80.0
PET, 30% Glass Fiber-reinforced	225.0	250.0	220.0	240.0
PET, 30/35% Glass Fiber-reinforced, Impact Modified	245.0	245.0	220.0	220.0
PETG - Polyethylene Terephthalate Glycol	69.0	71.0	63.0	63.0
PFA - Perfluoroalkoxy	70.0	75.0	90.0	90.0
PHB - Polyhydroxybutyrate	130.0	135.0	77.0	79.0
PLA - Polylactide	53.0	56.0	-	-
PI - Polyimide	-	-	240.0	360.0
PMMA - Polymethylmethacrylate/Acrylic	80.0	110.0	70.0	100.0
PMMA (Acrylic) High Heat	90.0	170.0	85.0	160.0
PMMA (Acrylic) Impact Modified	75.0	100.0	70.0	95.0
PMP - Polymethylpentene	80.0	90.0	49.0	55.0
PMP 30% Glass Fiber-reinforced	121.0	177.0	149.0	166.0
PMP Mineral Filled	90.0	110.0	-	-
POM - Polyoxymethylene (Acetal)	158.0	172.0	110.0	136.0
POM (Acetal) Impact Modified	145.0	160.0	64.0	90.0
POM (Acetal) Low Friction	168.0	172.0	118.0	136.0
POM (Acetal) Mineral Filled	158.0	175.0	100.0	140.0
PP - Polypropylene10-20% Glass Fiber	110.0	140.0	90.0	127.0
PP, 10-40% Mineral Filled	85.0	113.0	50.0	68.0
PP, 10-40% Talc Filled	100.0	127.0	56.0	75.0
PP, 30-40% Glass Fiber-reinforced	140.0	155.0	125.0	140.0
PP (Polypropylene) Copolymer	85.0	104.0	50.0	60.0
PP (Polypropylene) Homopolymer	100.0	120.0	50.0	60.0
PP, Impact Modified	75.0	88.0	46.0	57.0
PPA - Polyphthalamide	-	-	120.0	138.0
PPA, 30% Mineral-filled	157.0	159.0	278.0	280.0
PPA, 33% Glass Fiber-reinforced	284.0	286.0	296.0	298.0
PPA, 33% Glass Fiber-reinforced – High Flow	279.0	280.0	-	-
PPA, 45% Glass Fiber-reinforced	286.0	288.0	200.0	200.0
PPE - Polyphenylene Ether	110.0	138.0	90.0	130.0
PPE, 30% Glass Fiber-reinforced	138.0	154.0	134.0	144.0
PPE, Flame Retardant	100.0	150.0	90.0	150.0
PPE, Impact Modified	100.0	120.0	90.0	120.0
PPE, Mineral Filled	100.0	120.0	90.0	110.0
PPS - Polyphenylene Sulfide	140.0	160.0	100.0	135.0
PPS, 20-30% Glass Fiber-reinforced	270.0	278.0	250.0	260.0
PPS, 40% Glass Fiber-reinforced	270.0	280.0	260.0	270.0
PPS, Conductive	230.0	260.0	225.0	230.0
PPS, Glass fiber & Mineral-filled	200.0	280.0	170.0	260.0
PS (Polystyrene) 30% glass fiber	82.0	113.0	77.0	122.0
PS (Polystyrene) Crystal	75.0	100.0	70.0	90.0
PS, High Heat	90.0	110.0	85.0	100.0
PSU - Polysulfone	176.0	182.0	160.0	174.0
PSU, 30% Glass fiber-reinforced	180.0	190.0	175.0	185.0
PSU Mineral Filled	180.0	185.0	175.0	180.0
PTFE - Polytetrafluoroethylene	70.0	120.0	45.0	50.0
PTFE - 25% Glass Fiber-reinforced	-	-	200.0	200.0
PVC (Polyvinyl Chloride), 20% Glass Fiber-reinforced	75.0	80.0	75.0	78.0
PVC, Plasticized	30.0	56.0	30.0	53.0
PVC, Plasticized Filled	30.0	56.0	30.0	53.0
PVC Rigid	57.0	80.0	54.0	75.0
PVDC - Polyvinylidene Chloride	80.0	90.0	54.0	65.0
PVDF - Polyvinylidene Fluoride	70.0	150.0	50.0	125.0
SAN - Styrene Acrylonitrile	105.0	115.0	90.0	100.0
SAN, 20% Glass Fiber-reinforced	105.0	115.0	95.0	100.0
SMA - Styrene Maleic Anhydride	-	-	35.0	45.0
SMA, 20% Glass Fiber-reinforced	-	-	105.0	120.0
SMA, Flame Retardant V0	-	-	110.0	110.0
SMMA - Styrene Methyl Methacrylate	100.0	100.0	80.0	95.0
TPI-PEEK Blend, Ultra-high heat, Chemical Resistant, High Flow, 240°C UL RTI	270.0	270.0	235.0	235.0
TPS, Injection General Purpose	35.0	45.0	-	-
TPS, Water Resistant	45.0	45.0	-	-
SRP - Polyphenylene (Self reinforced)	-	-	154.0	159.0
UHMWPE - Ultra High Molecular Weight Polyethylene	68.0	82.0	40.0	50.0
XLPE - Crosslinked Polyethylene	54.0	107.0	40.0	63.0