A significant advance in polyolefin based thermoplastic elastomer TPVs resulted from the discovery that EPDM rubber, when selectively crosslinked under shear (dynamic vulcanization) during melt mixing with a compatible plastic, namely isotactic homopolypropylene, results in a thermoplastic elastomer with mechanical properties and manufacturing capacity, far superior to those obtained from a simple mixture of elastic and plastic materials. Vulcanized thermoplastics (TPVs) are a series of high performance elastomers that combine the desirable characteristics of vulcanized rubber, such as flexibility and low compression, with the ease of processing thermoplastics. It combines the typical performance of a thermoset rubber together with the advantages of a thermoplastic compound. Embedded in the middle range costs and the development spectrum of both thermoplastics and thermoset rubbers. TPV polymer is accepted for a wide range of utilities in industrial and consumer products. Its unique combination of material properties and ease of processing allow the producer to achieve both critical objectives such as low production costs, consistent quality and improved production performance. TPV polymer has an environmental resistance comparable to the EPDM rubber compound, while the fluid resistance is comparable to that of polychloroprene rubber compounds for general use; a unique combination that allows for a wide range of applications. Its unparalleled colorability, sensation and aesthetics opens up new design opportunities in consumer applications. TPVs are highly resistant to abrasion, have a reduced absorption of oils and their cost is low with respect to TPU.
Shore hardness from 35 A to 50 D
Operating temperature of -40 ÷ 130 ° C
Density of 0.89 ÷ 1.20 gr / cm3
Good weather resistance
Excellent resistance to UV rays
Good chemical resistance
Excellent compression set
Good resistance all'abrasioe
good processing capacity
Compatible with PP
Resistance to the weather
Resistant to bending fatigue
Very good chemical resistance to acids, alkalis, solvents and oils
Excellent electrical insulation properties.
Very good elastic memory
TPV physic and mechanical properties
TPV elastomers TPV plastic has excellent strength to shorten growth while it is flexible, high density and excellent fatigue resistance, and good resistance to many acids and base and aqueous solutions. The flexibility of TPV varies from elastic, 35 on the Shore A scale, to hard, 50 on the D scale. The TPV has a rubber elasticity outstanding at high temperatures, with a recovery of the deformation superior to the vulcanized rubber in the tests of Long-term compression sets. The general purpose grades are appropriate for many utilities, and also available in FDA, on the NSF list and medical degrees.
The TPV is ideal for use in high temperature applications with superior heat resistance to other elastomers. The pieces made of TPV offer a range of constant service temperature from -60 ÷ 135ºC without cracking or stickiness. Excellent heat aging combines with resistance to oils and greases for exceptional durability. The degrees of fire resistance meet the requirements of UL94. These grades are UL 94 V-0 or UL 94 HB.
TPV has excellent resistance to shorten growth while being flexible, high density and excellent fatigue resistance, and good resistance to many acids and base and aqueous solutions. Excellent resistance to water, acids, alkalis, alcohols, acetone and vegetable oils. However, care must be taken because it is susceptible to being attacked by aromatic organic solvents, gasoline, mineral oil, etc.
TPV Electrical properties
Like polyethylene and polypropylene, TPV granules have excellent electrical insulation performance. They are good electrical insulators, with constant electrical properties over a wide range of temperatures and frequencies. They are generally used in overmolding rigid elements in electrical systems.
Due to the cured or crosslinked elastomer phase, the TPV compounds pellets can be very difficult to color. The addition of separate color as a masterbatch can also have an unexpected effect on the physical properties and functionality of the composite, therefore we have available several predetermined mass colors, as well as in black or natural that can be processed with uniform color without loss of properties or performance.
TPV can be processed in standard thermoplastic equipment. It can be injection molded, extruded, blow molded and thermoformed with the efficiency and economy associated with thermoplastic materials. Additionally, clean waste from these operations can be reprocessed.
Overmolding - 2k
Due to its chemical affinity with polyolefin polymers, it easily adheres to polypropylene or polyethylene without the need for adhesives or surface treatments. The ability to adhere to a variety of substrates by two-shot or overmolding allows for ease of processing with excellent adhesion. Transparent and translucent products are easily available. TPV is offered soft with chemical adhesion on most polymers, including: PP, ABS, PC, PMMA, PBT, PA, etc.
Dynamic vulcanization is the process of producing a thermoplastic elastomer by selective cross-linking of the rubber phase during the mixing of a technologically compatible or compatibilized rubber and plastic mixture of high rubber content, while minimally affecting the plastic phase. Rubber cross-linking is achieved only after a mixture of well-mixed molten polymers is formed and the mixing of intensive mixtures is continued during the curing process. The elastomeric thermoplastic vulcanizate thus formed should ideally consist of a matrix plastic which is filled with crosslinked rubber particles of 1 to 5 amstrong.
The thermoplastic vulcanizate is a vulcanized thermoplastic elastomer developed with resin and synthetic rubber technology. The TPV elastomer is derived from olefin-based rubber and olefin-based resin and does not require compounding or vulcanization processes such as rubber. Similar to a general purpose resin, it can be molded and its natural grade can be easily colored. Dynamic vulcanization is a widely used method for preparing thermoplastic elastomers comprising elastomer particles partially or totally crosslinked in a melt processable thermoplastic matrix. Thermoplastic vulcanizates are prepared by melt blending the elastomer and the thermoplastic in an internal mixer or in a twin screw extruder. After a well mixed mixture has formed, in the second stage, vulcanizing agents are added as crosslinkers or curatives. The vulcanization of the rubber polymer takes place during the continuation of the mixing process under conditions of high temperature and high shear. The most common used compositions are based on EPDM and vulcanized polyolefins, like our TPPR XPRENE
TPV vs. TPO
In the transformation from TPO to TPV there is a substantial improvement in desirable elastomeric physical properties, such as elastic recovery (compression set, tension set) and tensile strength. This is counterintuitive, since the compatibility between rubber and plastic should decrease in rubber cross-linking and result in poorer TPV properties compared to the corresponding TPO. The observed properties of the TPV can be explained if the particulate rubber is firmly anchored in the amorphous part of the plastic phase. The change of hardness in the transformation from TPO to TPV is dependent after the change in the morphology of the product and the crystallinity in the plastic phase, also due to the cross-linking of the rubber phase. Because iPP is the main component of impact modified plastic and the impact modification of iPP by cross-linked rubber particles have a dramatic effect on the structure of the plastic glass, it is reasonable to propose that the increase in impact resistance observed in the The transformation of TPO to TPV is due to the modification of the crystal structure of the plastic phase. In the TPV, the homogeneous distribution of discrete rubber particles allows the material to behave more like rubber. A key attribute associated with rubber materials is their ability to recover from an imposed load. This is especially necessary in the area of sealing and stretching under a wide variety of service conditions. The TPO materials, although they are flexible, do not have good recovery properties. Both the lack of crosslinking in the rubber phase which is combined with the flow behavior of the PP causes a permanent and unrecoverable "set" in the material even at room temperature. This excludes its use in many sealing areas and other applications where the recovery of applied load is important. The discrete rubber particles in the TPV cause a comparative drop in tear resistance compared to TPO but only under ambient conditions. The POS continues to provide acceptable tear resistance even at elevated temperatures. Flex fatigue of the TPV is an excellent performance superior to chloroprene, EPDM and thermoses chlorosulfonated rubbers. The thermal properties of TPO and TPV for example the point of fragility at low temperature is comparable between the TPV and the soft TPO, but the stronger influence of the PP phase on the hard TPO significantly increases the point of fragility. Although not shown, the impact performance at low temperature is good for both TPO and TPV. Due to the lack of cross-linking of the rubber in the TPO material, the upper service temperature is limited. The melting temperature has a much lower influence on the flow with TPV than with TPO. Comparing a standard grade of TPV with TPO, it can be seen that the TPO has a lower melt viscosity and a higher melt flow capacity. Both the TPO and TPV show a thinning behavior of linear cut in the melting condition. It is possible to generate MFR values of melt flow rate for TPO, but due to the different rheological characteristics of TPV, it is not possible to achieve a constantly repeatable MFR value.
TPV vs. SEBS
The TPV is characterized by a high resistance to various media and high temperatures. Due to its highly crosslinked EPDM particles, components made of TPV as opposed to components made of different types of TPE have better mechanical properties and temperature loads. Thermoplastic vulcanizates (TPV) share many of the same characteristics as TPE compounds based on styrene block copolymers (TPS), such as attractiveness to touch, flexibility, recycling, etc. In certain applications, the higher thermal stability and chemical resistance of a TPV is not required and the TPS-based compounds will perform very well under these circumstances. Similarly, there are times when a TPS compound does not have the strength and durability for a demanding environment. Compared with SEBS compounds, TPV PP / EPDM exhibit better elastic recovery at a higher service temperature (100 ° C vs. 70 ° C). In "static" applications, PP / EPDM TPV can provide service at 135 ° C, compared to 100 ° C for SEBS compounds. Very soft TPE (0-5 Shore A) are based on SEBS; PP / EPDM TPVs with a hardness below 35 Shore A are not available.
The TPV is an ideal replacement for thermoplastic rubber and PVC-based elastomers in a wide variety of applications that require highly elastic properties. In addition to exceeding other competitive thermoplastic elastomers in scratch and tear resistance along with an elastic behavior, faraprene is also an ultra low extractable material, which makes it ideal for many industrial and consumer applications. The POS is 100 percent recyclable and does not contain phthalates found in PVC-based materials. It is a superior choice for molders and manufacturers that try to reduce their environmental impact. Automotive industry: steering bellows, shock absorber bellows, air intake system ducts, spark plug wires, body plugs, burglary, glass encapsulation, command cables, fuel supply pipes, airbag covers and housings, armrests and surfaces of doors, buttons and knobs, coasters, mats, instrument panels, touch screens. Electrical industry: high flexibility cables for ranges up to 30000V. Electrical connectors, insulated grips, food industry, cutlery and disposable tableware, kitchen food containers, toys, refrigerator trays, transparent plates.