The group thermoplastic elastomer consists of Soft PVC, thermoplastic rubber (TPR), and thermoplastic polyurethane (TPU). We have addressed Soft PVC separately on this site, as this is historically one of the most used materials. The TPR and TPU materials came later into existence to solve geographical problems for areas where Soft PVC cannot be used and to serve specific market segments.
There are two types of TPR in existence, one a mixture of PP and EDM, the other ethylene-vinyl acetate mixed with vinylidene chloride.
Both types belong to the thermoplastics featuring good rubber-like properties. Both materials are suited to be co-extruded to other thermoplastics, thus creating ample possibilities to develop technical solutions for plastic profiles in various market segments.
Thermoplastic rubber is a material that can be stretched in room temperature conditions to twice the original length. After releasing the material almost immediately returns to nearly its original length. This is where it differs from standard thermoplastics with an added plasticizer. This rubber-like behavior renders the materials extremely suited for seals. Both materials are reasonably well resistant to oil and feature great weather resistant qualities. Both types are available in various hardness gradations. In addition, TPR is exceptionally resilient and will not break easily.
The definition of a thermoplastic rubber is not clearly defined but depends on the rubber-like qualities of the material. Typically, all rubbers possess similar, good to great qualities within the same temperature range. Adding plasticizers can further enhance rubber qualities. An advantage of thermoplastic rubbers is that they can be co-extruded with other thermoplastics.
Various compounds are distinguished:
PP/EDM compounds
Used for sealing profiles and bonding to polypropylene components.
Ethylene-vinyl acetate/vinylidene chloride compounds
Used for co-extrusion with Hard PVC for high-grade applications, this compound is not suited for use with acrylate and polycarbonate.
PVC co-polymer compounds
Used for co-extrusion with Hard PVC and as plasticizer-free for acrylate and polycarbonate plates.
SBS and SEBS compounds
For independent rubber-like profiles as well as for co-extrusion with ABS and SBS.
TPR profiles are commonly used for:
Characteristic about thermoplastic rubbers is the fact that part of the characteristics are combined with the processing properties of thermoplastics. The elastic qualities are established through chemical or physical molecular fusion, just as if the plastic is partially vulcanized. This creates a transition range between stiff plastics onto manufactured elastic thermoplastics, up to fully vulcanized rubbers.
Just like most rubbers, these species come in black. The primary color, however, is beige. By infusing masterbatches, the color can be altered to choice.
TPR’s are not available in transparent form. In case a transparent rubber is required, TPU can be offered as an alternative.
TPR rubbers are flammable. The formula can, however, be altered in such a way that the compound becomes self-extinguishing to inflammable.
In general, TPR seals will not be painted or lacquered; when painting is required, the surface needs to be primed.
Welding of TPR material is generally possible by the mirror welding method, and this is the big difference with vulcanized rubbers.
With the increasing solidity of the rubber, they become more resistant to oil and gasoline. On top of that, the materials also become resistant to watery solutions of acids and alkalis as well as chemicals like ethyl alcohol and ethyl acetate.
The materials are not resistant to aromatic compounds and halogenated hydrocarbons.
TPR’s are outstandingly suited to be bonded with other thermoplastics like co-, tri-, and quad extrusion. Next to the bonding with natural TPR, like with different coloring, it also bonds well with SEBS and SBS compounds: PS, ABS ASA, LDPE, HDPE, HMPE and PP, and certain types containing TPO and TPV compounds.
TPO and TPV compounds: LDPE, HDPE, HMPE, PP, and certain types with SEBS and SBS compounds.
TPU is extremely wear-resistant and possesses good mechanical qualities. This makes the material utterly suitable for applications in dynamic and semi-dynamic seals and gaskets. TPU is also well resistant to mineral oils and greases. The superior tensile strength of TPU allows the use under intense stress.
TPU profiles are commonly used in:
TPU can be colored with masterbatches.
TPU is a transparent material. It is advisable always to add a UV-stabilizer to prevent yellowing and deterioration of the material.
TPU’s are like TPR’s combustible. TPU material can be altered with additives to make the material self-extinguishing to nonflammable.
In general, seals and gaskets are not painted or coated. In case a coating is required, a primer must be used.
TPU can like TPR be welded by mirror welding techniques.
TPU is resistant to oils and greases, lesser against acids and alkalis.
TPU can be bonded with natural TPU, like with different coloring, as well as with Hard PVC, ABS, ASA, PMMA, and PC.
