Although thermosetting elastomers (TSE) are currently the most commonly used elastomers, thermoplastic elastomers (TPE) have become increasingly important due to their rapid growth and advantages in processing. We use injection molding here to make a basic comparison between TSE and TPE, as injection molding is suitable for both materials. Compared to this, blow molding is basically a patent of TPE.

Before TPE became an important force in the elastomeric industry, there was a clear market differentiation between the elastomer and plastic industries. Although each market has its advantages and disadvantages, the increasing applicability and use of TPE materials have attracted the attention of the elastomer and plastic industries. TSE has a long history of supplying formed components to the automotive industry, which is also an important application field of TSE materials. The drawback of TSE in terms of molding is its lack of processing technologies similar to TPE, which are commonly used in the plastic industry. During the processing, the TSE material is heated and vulcanized at high temperatures in the mold to produce the product. On the contrary, traditional plastic product processors need to cool the melt in the mold for a long enough time to harden the product. The other significant difference is that they also have significant differences in equipment.

Although the plastic industry has knowledge of TPE equipment and processing, they are not very familiar with the traditional uses and other applications of TPE in the automotive industry. Therefore, it is not surprising that both TSE and the plastic industry are competing with a rapidly growing TPE industry.

raw material

Despite the difficulty and high cost of recycling TSE materials, some progress has been made in this field. For example, sulfurized TSE components can be obtained from fragmented vulcanized materials through high-pressure sintering processing. Another type of TSE, EPDM rubber, may also lose the market for automotive door seals to TPE materials, partly because TPE's processing time can be significantly reduced from 2 minutes to 30 seconds.

Although TPE has many advantages compared to TSE and shows some outstanding advantages, its maximum effective temperature limits its application in many aspects. For example, the lower glass transition temperature of polystyrene and SBS blends at around 100 ℃ significantly limits their application at high temperatures, as the polystyrene phase becomes soft. Thermoplastic ethylene propylene adhesive is relatively good in this regard, but it also tends to soften above 135 ℃. Therefore, TSE is still the material choice for high-temperature applications.

We know that the farther the glass transition temperature of the rubber phase in amorphous TPE is from that of the plastic phase, the higher its effective use temperature. For TPE with crystalline phases, the farther the glass transition temperature of the rubber phase is from that of the crystalline phase, the wider the effective use temperature range.

Increasing the softening temperature of the plastic phase will help to increase the effective use temperature of TPE, but this will also require a corresponding increase in the processing temperature of TPE, which is also a factor leading to TPE decomposition at higher molding temperatures. For TSE, the thermal stability of the skeleton and cross-linked structure determines the effective usage temperature.

Performance and cost are key considerations for every application. A comparison of several formed products shows that both TSE and TPE have cost advantages and disadvantages. For example, a TPE formed hole ring has a lower cost than TSE, although the mold used in TPE is significantly more expensive than the mold used in TSE. Other advantages include the ability to easily add gray to TPE and the convenience of installing TPE hole rings. Another example is a small plug that may come into contact with engine oil frequently. Comparing oil resistant TPE with NBR, NBR is more economical. Of course, the entire TPE industry is continuing to innovate, improve performance, and enhance product processability.

machining

Since TPE entered the field of traditional TSE and plastics, everyone has had to accept the differences in design, materials, processing, and applications between TPE and TSE. The difference in processing temperature between TPE and TSE is used as an important point to describe the difference in the forming process between these two materials. In injection molding, TSE is extracted from a hot material barrel and then cured through a hot mold, while TPE is extracted from a hot material barrel and then cured through a cold mold.