Stanyl® temperature performance

Stanyl has a temperature resistance similar to high heat materials like PPS, polysulfones, PEI and LCP's and above the well-known engineering plastics such as polyamide 6 or 66 and polyesters. Stanyl stands out from these other materials through its mechanical performance over the full temperature range. This is a critical factor in today's high-tech world where performance over a wide temperature range can often be of critical importance.

When designing with thermoplastics, the properties of a material for a given set of environmental conditions need to meet the critical design level required of the component. Most properties decrease as temperature increases and heat aging also occurs. Consequently performance at high temperature, either continuous and/or short term, need to be considered when high temperature conditions apply.

Short-term heat performance
An indication for the short term temperature performance of a material is its stiffness and strength level at elevated temperatures, for instance between 100°C and 290°C. This stiffness/strength level at elevated temperatures should be considered as 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. The HDT is defined as the temperature at which a test bar is deformed to a given extent at a given load applied; this is related to a certain level of stiffness at the elevated temperature. Due to its excellent retention of stiffness at higher temperatures, Stanyl's HDT-rating of 190°C (375ºF) for unreinforced and 290°C (555ºF) for reinforced grades is higher than that of other engineering plastics or high performance materials.

HDT of Stanyl versus LCPs.

Long-term heat performance
For designers it is crucial to know the performance level of the end product and therefore of the material at the end of its lifetime, which often means after 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. Different parameters like strength, stiffness, impact resistance, elongation at break can be selected to monitor the performance after heat aging over time and measured either at room temperature or at the elevated temperatures.

The results of these measurements can again be displayed in various ways; in a relative way via retention levels or 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 (300ºF) after aging for several thousands of hours at 150°C.

Positioning of thermoplastics according to ARO principle.

The Continuous Use Temperature (CUT) is frequently used in the automotive industry as a selection criterion. It 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, 1000, 5000, 10000 or 20000 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 5000 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.

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 (280ºF).

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, as 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. Such 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 are to be expected 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 in above table and the figure below, shows the superiority of Stanyl in comparison with PA66, PPA and PPS after heat aging at 150°C (300ºF).

Absolute level of tensile strength at real operating temperature (150°C) after heating at 150° for Stanyl and competitive thermoplastics.