Short-term heat performance
When it comes to thermoplastics, properties tend to decrease as temperature increases and brings with it heat aging. In terms of short-term performance, a material is usually measured on its stiffness and strength at temperature range of between 100°C and 290°C – which in turn becomes the critical level to design for, since room temperature levels for stiffness/strength are in general much higher, even after moisture absorption.
Flexural modulus versus temperature
The melting point in combination with the Heat Distortion Temperature (HDT) gives another good impression of the peak temperature resistance under a certain load. We define the HDT as the temperature at which a test bar gets deformed to a given extent at a given load; which in turn is related to a certain level of stiffness at the elevated temperature.
Thanks to its excellent retention of stiffness at higher temperatures, Stanyl's HDT-rating of 190°C (375°F) for unreinforced and 290°C (555°F) for reinforced grades is higher than any other engineering plastic or high performance material.
Long-term heat performance
For designers it’s crucial to know the performance level of the end product and therefore of the material at the end of its lifetime, which often means exposure for thousands of hours to heat in an oxygen environment. This performance - the heat or air aging resistance - can be expressed in various ways, from strength and stiffness to impact resistance and elongation at break.
We can then display the results of these measurements in various ways; in a relative way via retention levels; via relative characteristics like Continuous Use Temperature and Relative Temperature Index; or in an absolute way, using the Absolute Real Operating (ARO) Value concept which shows the absolute value of the property measured, for instance at 150°C (300°F) after aging for several thousands of hours at 150°C
Positioning of thermoplastics according to ARO principle
The Continuous Use Temperature (CUT) is often used in the automotive industry as a selection criterion – and is defined as the temperature at which a given mechanical property (usually tensile strength or impact resistance) decreases by 50% within a certain period of time, usually 500, 1,000, 5,000, 10,000 or 20,000 hours. Stiffness and tensile elongation cannot be used to measure CUT since stiffness only increases after heat aging and tensile elongation shows a too sharp, non-discriminating drop for all materials. The CUT of 30% glass fiber reinforced Stanyl at 5,000 hours is 175°C; the drop in tensile strength is 50% after 5000 hours of aging at 175°C. The different CUTs for different aging times are summarized in the chart below.
Table - Stanyl heat aging resistance (CUT versus ARO concept)
|CUT 5000 hrs (°C)||130-170*||177||185|
|ARO 5000 hrs
Strength at high temp (MPa)
after aging at high temp
*Depending on the exact heat stabilizer package and content used.
Heat aging resistance as expressed by the CUT and ARO-concept and stiffness at elevated temperatures for Stanyl and competitive polyamides (30-33% GF reinforced)
The Relative Temperature Index as given by UL is commonly used in the E&E industry. It can be considered to a certain extent as a CUT for very long half-life times ranging between 60,000 and 100,000 hours. The RTI of heat stabilized Stanyl 30% GF is 140°C (280°F).
The Absolute Real Operating Value after heat aging gives designers more realistic comparisons between the various materials. It overcomes the major drawbacks of the CUT and RTI concepts in that only the retention of properties is considered and these properties are only measured at room temperature after heat aging. Certain materials that start at a very low level but retain this level to a high degree, like for instance PPS (see figure below), are rated better in CUT terms than other materials, which start at a higher level but show more of a reduction. These materials can still outperform the former materials in absolute values after the heat aging exposure.
In addition, the CUT is based on measurements of properties at room temperature, while the more critical design levels usually come in the elevated temperature range.
Tensile strength at 23°C after heat aging at 150°C for Stanyl and competitive thermoplastics
The ARO concept demonstrated above and below, shows the superiority of Stanyl in comparison to PA66, PPA and PPS after heat aging at 150°C (300°F).
Absolute level of tensile strength at real operating temperature (150°C) after heating at 150°C for Stanyl and competitive thermoplastics
New technology for even higher thermal resistance - DIABLO
Our bright scientists have raised the thermal performance of Stanyl even higher to offer better heat resistance. This unique technology interferes with the heat degradation mechanism (see image below), making DIABLO a stand-out performer for heat performance.