Two component (2K) injection molding, also referred to as two-shot molding or over-molding, has gained relevance and substituted traditional methods, thanks to its higher productivity and flexibility. Numerous leading manufactures have tied up to enable combinations and develop ingenious solutions according to market needs with sustainability goals.

PA/TPE combination for power tools and home appliances

DOMO and Mitsubishi Chemical Group (MCG) presented a new combined material with polyamide (PA) and thermoplastic elastomer (TPE), for outstanding adhesion and haptics, as well as increased sustainability through the use of recycled material feedstocks.

Developed specifically for MCG, TECHNYL 4EARTH C1E 249 SIL1 V30 RD 3202 is a 30% recycled polyamide (PA) in the color red RAL 3202. 

MCG’s TEFABLOC TG0174465A is a TPE-S compound made of 30% recycled content and capable of bonding to several engineering plastics, including PA6, PA66 and PA6.10. This material can be directly over-molded on PA6 and PA66 without the need for additional adhesive, making it a perfect match with DOMO’s TECHNYL 4EARTH. 

The combination of PA over-molded with TPE brings several advantages: a low-density solution with high chemical resistance and very good mechanical properties provided by PA, combined with the soft touch, a good grip and sound dampening of TPE. 

Both solutions provide superior surface quality typically required in consumer goods applications. Depending on the design, the TPE can also ensure sealing against moisture, dust and air. 

Typical applications for this TPE/PA 2K molding solution include power tool or home appliance handles or bases. Other application fields include medical devices, small appliances, electrical and electronics (E&E), eyeglass frames and sports equipment. 

ABS/TPE over-molding project for consumer products

Making a material selection can be a complicated task when designing consumer products. There are many properties to balance, and the choice is even more complex when including eco-design principles. Selecting two materials for a 2K part is not doubling the difficulty; it is squared. 

To help with this decision, HEXPOL TPE and Polykemi AB have cooperated on 2K sustainable development project that reduces carbon footprint for consumer products.

To demonstrate the possibilities in reducing the product carbon footprint, increasing recyclability and optimising adhesion, HEXPOL TPE’s Sustainable Materials Lab meets Polykemi’s Materialsmart meets to create tested solutions.

HEXPOL TPE and Polykemi have done substantial work in the field of sustainability, allowing them to provide cradle-to-gate Product Carbon Footprints (PCF) and calculate the Global Warming Potential (GWP) per kg of material.

PCF comparison for 2K material combinations. (Source: HEXPOL TPE)

The PCF data shows that switching from a combination using fossil-based acrylonitrile butadiene styrene (ABS) from Polykemi, over-molded with a fossil-based TPE from HEXPOL TPE, to a combination of recycled Polypropylene (PP) and TPE with bio-circular attributed content, can give a 77% reduction in CO2e. This combination can also bring advantages when considering end-of-life and recycling compatibility.

Combinations using mechanically recycled ABS with bio-circular attributed TPE were also tested, which gave a 57% reduction in CO2e compared to the fully fossil-based equivalents. 

Adhesion-synchronized materials for automotive applications

HEXPOL TPE has also partnered with almaak international to optimize 2K material combinations tailored for automotive applications. 

The collaboration between HEXPOL TPE and almaak aims to deliver tested material combinations that ensure chemical compatibility and adhesion performance.

almaak’s products include polycarbonate (PC), acrylonitrile styrene acrylate (ASA), polybutylene terephthalate (PBT), ABS, PC/ABS, PA6, PA6.6 and their blends, including materials with up to 100% recycled content. These have been adhesion tested with HEXPOL TPE’s portfolio of TPE materials.  

The engineering thermoplastics and TPE combinations have been tested according to the VDI 2019 standard, which measures the adhesion between materials. 

TPE is molded onto the thermoplastic and peeled off at a 90° angle. The required adhesion peel force is measured and describes the adhesion quality. 

Even for substrates which make bonding difficult, such as PBT, it is possible to get a good adhesion if the substrate and TPE are compatible. For example, Dryflex UV 65.01B220 TPE achieves an adhesion peel force of 3.3 N/mm on Anjacom PBT 455-GF30.

As processing conditions (2K or insert moulding, temperature, injection speed) as well as tool design (geometry, adhesion area, flow length) can impact adhesion performance, the support package offered by almaak and HEXPOL TPE also includes tooling and processing advice. 

Recycled material portfolio with wide adhesion options

KRAIBURG TPE has launched its latest product line – an expansion of its THERMOLAST R compounds with high percentage of recycled materials and a variety of adhesion properties.

This new product line, now available in the market, focuses on the combination of properties for single, two-component or multi-component parts combined with high proportions of recycled material of up to 79%.

The new high-performance compounds are specially tailored to meet the requirements of different market segments and allow adhesion to PA, PC/ABS or PP. 

KRAIBURG TPE presents recycling content TPEs with various adhesion options. 

There are three new compounds in this new product line. The first one is recycling content TPE with adhesion to PA. It is said to be the first TPE worldwide with a proportion of post-consumer recycled (PCR) and post-industrial recycled (PIR) materials of 43 to 60%, depending on their hardness ranging from 40 to 90 Shore A.  

The second material is recycling content TPE with adhesion to PC and ABS. It is made of 42 and 54% PIR and PCR contents. It is suitable for a wide range of multi-component parts that require adhesion to ABS and PC or other technical thermoplastics. Its hardnesses are available from 40 to 70 Shore A.

The last compound is the second-generation Universal PCR TPE, which is available with a proportion of recycled materials of up to 79% and suitable for applications that require adhesion to PP. Its hardness range is 30 to 90 Shore A.

The new TPEs are intended for applications in industrial market segments such as power tools, E&E, as well as consumer segments, including household, sports and leisure.