High toughness grades with improved heat shock resistance

Polyphenylene sulfide (PPS) resin is a highly heat-resistant resin that is categorized as a super engineering plastic. It exhibits outstanding flame retardancy, mechanical properties, dimensional stability and chemical resistance. PPS demonstrates a high level of chemical resistance comparable to fluororesins, a feature demonstrated by the fact that there is no organic solvent that can dissolve it at temperatures of 200℃ or below. It also exhibits excellent heat resistance, illustrated by a melting point of 280℃ and a continuous service temperature range of 200 – 240℃. As there is none of the hydrolysis that occurs with polyamide resins and polyester resins, excellent long-term reliability is another feature that makes it hugely attractive for product design.

Global demand for PPS resin was estimated to be approximately 100,000 tons in 2016. The automotive sector has seen particularly strong growth in demand in recent years, driven by electronic components for next-generation vehicles (hybrid electric vehicles, electric vehicles, and fuel cell vehicles). There has also been additional demand generated by the substitution of metals used in components, due to downsizing and weight reduction. Here we introduce our efforts to develop new high-filled, high toughness grades with greatly improved heat shock resistance, for which there is a particularly high demand within the automotive sector.

PPS resin typically has outstanding heat shock resistance, and one of the reasons for this is believed to be its low coefficient of linear thermal expansion, which is close to that of metal. Linear type PPS, in comparison to cross-link type, has particularly outstanding heat shock resistance thanks to its high toughness, and is suitable for use in metal insert parts. Furthermore, high toughness grades refined with impact modifiers or other such additives are ideal in cases where advanced heat shock resistance is required. DURAFIDE® 1130T6 (30% glass fiber/high toughness) and DURAFIDE® 6150T6 (high filler content/high toughness) are leading grades for this requirement. Their heat shock resistance properties are shown in Figure 1. 1130T6 and 6150T6 exhibit excellent heat shock resistance in comparison to 1130A6 (30% glass fiber/standard).  

However, these grades with improved heat shock resistance generate large quantities of mold deposits, which are caused by gases originating from the impact modifiers. Therefore, increased frequency of maintenance of the metal mold is an issue associated with them. The trend toward reduction of product thickness and weight has also resulted in an increased requirement for materials with higher flowability. However, the acts of increasing flowability and improving toughness to give heat shock resistance normally have a conflicting effect. For that reason, designing a PPS material that has both high flowability and high heat shock resistance has traditionally been a difficult task.

Polyplastics has now developed new high-filled, high toughness grades DURAFIDE PPS 6150T73 and 6150T8. With these grades, Polyplastics has overcome the abovementioned problems by re-examining the various raw materials used in their manufacture—including the PPS base polymer—and by improving compounding technique. DURAFIDE PPS 6150T8 exhibits high flowability and improved heat shock resistance, while DURAFIDE PPS 6150T73 benefits from even higher heat shock resistance. Additionally, both grades demonstrate low outgassing (low mold deposit) characteristics, and they are expected to be applicable to a wide range of fields and a large variety of items.  For more details, visit: https://www.polyplastics.com/en/product/lines/pps_hs/index.vm.