Polyester elastomers that fuse to a wide range of polar resins.

To achieve both the desired "tactile feel" and design aesthetics required for grips on electronic devices and home appliances, there is a growing need for integral molding of hard resins such as PC, ABS, PBT, and PA with elastomers without the use of adhesives. This article will explain the heat fusion mechanism of the polyester elastomer "Tefabloc™ TPC" with polar resins, as well as the suitable grades.

Reasons for the Need for Adhesion to Rigid Resins

In the development of electronic devices and consumer goods, there is a growing need to "firmly integrate soft elastomers with rigid engineering plastics such as PC, ABS, PBT, POM, and PA."

For example, in electronic devices, camera grips, game controller handles, the backs of remote controls, PC peripherals (such as mice and keyboard palm rests), and handles on home appliances, the “feel”—including ease of grip and slip resistance—is a key factor that determines a product’s value.

However, in the past, combining rigid resins and elastomers required surface modification—such as using adhesives, plasma treatment, or corona treatment—or mechanical interlocking. These methods present numerous challenges, including an increase in the number of process steps, higher costs, risks associated with residual solvents and leachables, and assembly variations. In the electronics industry in particular, there is a strong demand to ensure consistent appearance and tactile quality while avoiding cost increases associated with surface treatments; consequently, there is a growing need for integrated molding that does not rely on adhesives or complex assembly processes.

This has drawn attention to the one-piece molding of “rigid resin + elastomer” using two-component molding (2K molding), and Mitsubishi Chemical’s polyester-based thermoplastic elastomer “Tefabloc™ TPC” was developed specifically for this purpose.

Characteristics of polyester elastomers

Tefabloc™ TPC is a material classified as a polyester thermoplastic elastomer (TPEE), a block copolymer in which hard segments (polyester) and soft segments (polyether) are linked together alternately. It has various characteristics, but the one we will discuss here is its excellent thermal bonding properties with polar resins.

Its greatest feature is its high melt-bonding ability with polar resins and engineering plastics such as PC, ABS, PA, PBT, and POM, which provides a significant advantage in two-color molding of electronic equipment casings and grip parts.

Why TPC can be adhered with rigid resins

The basic process for two-color molding (2K molding) is as follows:

① Primary molding: Molding of hard resins such as PC or PC/ABS.

② Mold opening → The mold is reversed and slid to move the primary molded product into the secondary cavity.

③ Secondary molding: Molten Tefabloc™ TPC is injected and allowed to flow over the surface of the primary molded product.

At this time, the following phenomenon occurs at the interface between Tefabloc™ TPC and the hard resin.

① The molten, high-temperature Tefabloc™ TPC flows while wetting the surface of the hard resin.

② Heat and pressure cause the molecules near the surface of the hard resin to become slightly fluid.

③ The molecular chains of Tefabloc™ TPC and the molecular chains of the hard resin side diffuse and intertwine with each other.

④ As it cools, this molecular entanglement is fixed, and a strong thermal fusion interface is formed.

Unlike bonding using adhesives, which involves sandwiching another material at the interface, this method creates a "welded" state where the resins are directly bonded together, resulting in a bond with superior sealing properties, durability, and aesthetic reliability.

Range of rigid resins that can be welded

Tefabloc™ TPC can be heat-fused with a wide range of rigid resins, including the following:

Amorphous resins: PC, ABS, AES, AS, GPPS, HIPS, PMMA, PPE/PS, etc.

Crystalline resins: PBT, PET, PET-G, PA6, PA66, PA12, PA-MXD, etc.

Biodegradable resin: PLA, PBSL, etc.

Cellulose-based resins: Cellulose proonate, cellulose acetate, etc.

For glass fiber reinforced and flame-retardant grades, optimization of drying and preheating conditions is necessary, but combinations with various resins used in electronic equipment casings and internal structural components can be considered.

Reccomend Grades

Grades that have been confirmed to adhere to various hard resins in adhesion tests are indicated in red.

Adhesion has been confirmed for many grades of PC and ABS.

PMMA has good adhesion to many TPCs. Other grades not listed can also be fused.

PA fusion is preferably performed using A1610N and A1710N.

For PBT and POM, EPO-18 and EPO-20 are suitable for development purposes.

For detailed data and samples, please feel free to contact us using the information below.