Recycling pressure to spur auto TPEs.

With thermoplastic elastomers (TPEs) representing a global market of about 600,000 metric tons and the automotive sector accounting for about one-third of total usage (figure 1), the pressure for recycling will result in strong growth potential for TPEs in automotive applications. Each year the U.S. scraps almost 13 million cars and light trucks, generating 151,000 metric tons of scrap nontire rubber containing 3.2 billion different TSR and TPE parts.

As indicated in figure 1, TPOs and olefinic TPVs are the major categories of automotive TPEs, representing between 60 and 80% of global automotive use.

Importance of recycling to TPEs

An automotive recycling infrastructure capable of segregating and recycling plastics and elastomers will have important primary and secondary effects on automotive TPEs:

* Volume effects - Significant volumes of materials could be generated and their use could be mandated as in Germany, thereby affecting supply and demand and the pricing of virgin automotive TPEs.

* Material selection criteria - Recyclability could become an important material selection criterion (which could favor TPEs at the expense of thermoset elastomers).

* Monomaterials systems - The problems and costs associated with separation of mixed plastics and elastomers will encourage a narrowing of the range of autopolymers in use. Polymers capable of functioning in automotive parts based on closely related or easily compatible polymer families will be preferred over multimaterial systems.

* Design for disassembly - This could encourage the substitution of plastics and elastomers for metal fasteners.

* Variety reduction - The average car uses about 30 different plastics and elastomer families. Sorting by polymer type is not economically feasible; therefore those polymer families that are most compatible with the major polymers will be preferred. The anticipated rapid growth of polypropylene in automotive use will therefore encourage the use of polyolefin-based TPEs such as TPOs and O-TPVs.

* Growth of TPEs vs. thermoset elastomers - The thermoplastic nature of TPEs has been one reason for their growth in automotive applications (especially for blow-molded parts). If automotive polymer recycling programs become active, the ease of handling TPEs in recycling processes will be an additional factor encouraging their growth into existing thermoset elastomer markets. It is of interest to note that the O-TPVs have been shown (ref. 4) to exhibit very little change in mechanical properties even after five regrinds.

* Compatibilizer TPEs - TPEs based on multiblock segments from different polymer families can act as compatibilizers for mixed plastics. The SBC-type TPEs in particular have been found to be capable of compatibilizing polyolefin and styrenic blends within certain concentration ranges. An increase in autoplastics recycling will enhance the market for this type of TPE.

* Closed-loop recycling - Resin suppliers that establish a closed-loop recycling infrastructure and negotiate contracts on that basis have a substantial advantage over competitors without the means to establish closed-loop recycling systems. The recycler becomes a new link in the automotive TPE supply chain. In the case of commodity TPEs, it may be desirable for the resin supplier to control this new link.

Bumper fascia

Bumper fascia have major visibility and often are the largest TPE application the vehicle. Intermaterials competition in the global bumper market has been previously reviewed (ref. 5). The key points regarding TPOs (and other TPEs) in this important application as follows:

* At 100% substitution, bumper fascia and rigid self-supporting bumper systems represent a potential market of approximately 350,000 metric tons (see figure 2).

* Physblend TPOs have taken major market shares of the bumper fascia market in Europe and Japan. In North America, the Physblend TPOs have about a 15% market share, which will grow rapidly. In North America, EPDM is the dominant elastomeric modifier. EPM rubber offers somewhat lower costs and is more widely used in Europe and Japan. More recently, VLDPE and VLDPE copolymers are being substituted for a portion of the EPDM or EPM rubber.

* In the United States, PU-RIM fascia and PC/PBT alloys (e.g., at Ford) are widely used but will see increased competition, primarily from Physblend TPOs and from reactor TPOs.

* Reactor TPOs used either with or without postreactor compounding could potentially offer a significant enough price advantage over Physblend TPOs to justify their continued penetration into the global bumper fleet.

* The size and potential of the bumper market attract Japanese polyolefin resin companies to overseas markets to service transplant auto manufacturers.

* The intense price competition and severe testing requirements for this major TPE application have made bumper fascia the battleground of the major resin supplier.

* The presence of paint on TPO bumper fascia remains a technical and economic barrier to recycling. The use of molded-in color protected by a clear topcoat is likely to increase.

Toyota and its resin suppliers have been actively improving bumper TPO formulations and recently announced a super-olefin bumper, in which the dispersed phase is aligned and has particle diameters as low as 100 angstroms, resulting in a fine microcrystalline structure in the elastomer phase. The microcrystalline structure results in increased tensile strength, hardness (double that of conventional TPOs), stiffness and impact resistance. The fine-particle dispersion is also responsible for increased fluidity during molding.

The improved moldability and scratch resistance will encourage the use of "super-olefin" TPOs in interior applications.

Commodity vs. specialty TPO

It is useful to distinguish between commodity TPEs, such as the Physblend TPOs and reactor TPOs, and specialty TPOs, which are highly tailored to meet the fabrication and performance requirements of smaller-volume, higher-value automotive applications. Competition between resin companies, and intense auto OEM purchasing pressures on this highly visible automotive TPE market have driven prices down to a point where the value-added levels can only sustain the interest of major resin and elastomer suppliers. A comparison of current levels of selling price and value-added for commodity TPOs (e.g., bumper fascia) and specialty TPOs (e.g., body side moldings or fender eyebrow components) is given in table 1.

[TABULAR DATA OMITTED]

The commodity TPO sector is dominated by major resin companies and their compounder affiliates, leaving little room for the independent compounder. In Europe, major TPO suppliers, some of whom also supply EPDM and EP rubbers such as DSM, Hoechst, Himont, Exxon Europe and ICI, dominate the bumper market. In the United States, Himont and D&S Plastics (joint venture between Dexter and Solvay) have the dominant share. In Japan, the commodity TPO market appears to be allocated between the resin suppliers and auto OEMs. For example:

* Mitsubishi Petrochemical, Tonen and Idemitsu supply Toyota;

* Showa Denko  and Mitsui Toatsu supply Honda; and

* Mitsui and Co., and Nippon Petrochemical supply Nissan.

Non-bumper TPO applications

Although bumper fascia have high visibility because of their size and participation in recycling, a substantial amount of TPO is used on a broad range of other components, as illustrated in table 2, which offers examples of TPO (and O-TPV) applications in the U.S., and Japanese automotive industry.

Table 2 - TPO and O-TPV automotive applications
and fabrication methods
                                           Blow   Est.1990 U.S.
Example components           Inj.   Ext    mold   demand (tons)
Bumper and exterior:
 Bumper fascia                 x
 Bumper trim molding                 x
 Sight shields                 x
 Air dams, spoilers            x                     27,000
 Body side molding                   x
 Mud guard                     x
 Weatherstrip seal                   x
Interiors:
 Headliner skin                     X(A)
 Wheel housing cover           X    X(A)
 Trunk liner                        X(A)               6,000
 Seat belt housing                           x
 Door trim skin                     X(A)
 Acoustic barner               x
 Other
Under the hood,
steering/suspension, misc.
 Rack/pinion boots                           x
 CV joint boots                              x
 HVAC ducting                                x         22,000
 Actuator housing                            x
 Lamp housings, seals          x
 Vacuum connector              x
 Acoustic barrier              x
 Other
Total                                                  55,000
Note: (A) primarily O-TPV in Japan

Reactor TPOs

Reactor TPOs are available from Himont, Exxon Europe, DSM, Hoechst, Nova, Enichem and Mitsui Petrochemical. Aristech, Quantum, Shell, Solvay and Eastman have grades in development stages or in early sampling. As indicated in table 3, the reactor grades could offer a price advantage over fully compounded TPOs. Compounders are actively using reactor TPOs to broaden the properties and processability of their compounded TPO product line. Based on current prices for first quality and wide-spec grades of PP and EP elastomers, it appears that reactor TPO prices must be somewhat lower than the current levels to attract wide interest from compounders.

[TABULAR DATA OMITTED]

Reactor TPOs are being used alone in interior trim applications and, as discussed below, the ability to calender the reactor TPOs is suggesting their use as interior automotive PVC skin replacement.

Price/property relationships

Extensive data have been presented on the properties of TPEs in comparison with each other and in competition with thermoset rubbers. The position of TPEs in the heat-resistance vs. oil-resistance map is published by suppliers of TPE alloys. The TPE alloys are about in the middle of the oil-resistance vs. heat-resistance spectrum. In particular they are considerably better than TPOs and compete directly in heat- and oil-resistance performance with neo-prene, but are somewhat inferior to CPE, CSPE, epichlorohydrin hydrogenated NBR and so on.

The general overview of the price/performance characteristics of TPEs shows how the O-TPVs and other TPE alloys span the range between commodity TPEs and what are usually (vaguely) referred to as engineering TPEs (E-TPEs).

Automotive interiors

Auto interiors consist of sandwich-type constructions, hard trim and functional solid components. The traditional construction of sandwich-type parts consists of a thermoformed PVC/ABS or powder-slush-molded PVC skin over polyurethane foam on an injection-molded support. on-molded support.

Previous studies (ef. 6) have shown that a variety of sandwich consolidation methods can be used for cost savings in auto interior components. More recent interest is in monomaterial constructions that facilitate recycling. An example would be a TPO skin over polyolefin foam on a PP substrate for instrument panels or door trim, or a PP skin laminated to PP foam for headliner construction.

Interiors currently represent only a minor share of automotive TPE demand. TPOs in particular have had only minor penetration for interior skin applications. Interiors will be the next major area for penetration of TPOs and O-TPVs. Initial penetration into interior trim by O-TPV in Japan has been for headliner skin (notably at Honda) and some door trim applications made from Milastomer, a partially vulcanized TPO from Mitsui Petrochemical.

Reactor TPO processes in particular are capable of producing soft grades with high ethylene content that are able to be calendered - Himont and Exxon are actively promoting calendered grades for instrument panel and door trim replacement of existing dry-powder-slush-molded PVC and thermoformed PVC/ABS skins on the basis of weight savings, nonfogging and recyclability in mononmaterial sandwich constructions. In Japan, where legislation concerning recyclability will take effect in the 1994-1995 period, TPO producers are competing to obtain a share of interior skin markets. Interior automotive skin applications represent a market of about 30,000 metric tons in Japan. Our forecast for penetration of TPOs and TPVs into the Japanese interior skin market in the 1995-1996 period is 6,000 tons for instrument panels and 2,000 tons each for headliners and door trim.

Intermaterials competition

The better-known automotive TPE applications such as the constant velocity boot have been extensively described in the literature. We have summarized these and some lesser-known automotive TPE applications in table 3.

Some of the intermaterials competitors in automotive TPEs for specific components are discussed below.

* Air conditioner hose - The shift to less permeable freons in automotive air conditioning is opening the opportunity for butyl-based TPEs to substitute for the halobutyl TSR/ny-1on 6 currently used for this application.

* CV joint boots - COPE TPEs replaced polychloroprene CV joint boots in the late 1980s in North America (ref. 7). In Europe, the rate of penetration of the COPEs is substantially slower due to the higher-temperature requirements of European designers.

* Rack/pinion bellows - This component illustrates the search for a price-performance match. COPEs were substituted for polychloroprene in the early 1980s by GM in the U.S., followed by Chrysler and Ford. By the later 1980s, about 80% of this application had shifted to Santoprene in North America. In Europe, polychloroprene still has the dominant share of this market with Santoprene and Hytrel sharing a little more than half

* Air ducts - Air ducts have seen penetration by the O-TPVs on the basis of their blow moldability. (The ability to blow mold TPEs is an important competitive advantage over TSRs in a broad range of auto applications.) For those air duct applications in which high temperatures are not encountered, TPOs are challenging the established position of the O-TPVs.

* Acoustic barriers - The excellent melt-flow characteristics of the SEBS-type SBCs have encouraged their use in highly-loaded, injection-molded acoustic barrier formulations. Where a higher temperature is required, O-TPV is used as the base TPE. The reactor TPOs with their enhanced flow characteristics are likely challengers in this automotive TPE market.

The value chain

The widened range of TPEs available to the automotive component engineer results in an intermaterials competition that is similar to that found in autoplastics. Higher-priced engineering TPEs (E-TPEs) open a new application and substitute for thermoset elastomers or other incumbents on the basis of better or adequate performance or cost savings due to thin walling, weight savings, parts consolidation or improved design freedom. Where appropriate, these new incumbents remain, but where they are overengineered they are replaced by a new generation of more cost-effective TPEs often offered by suppliers without the financial strength or technical capability to pioneer a new application.

Summary

TPOs and TPVs are important growth areas for automotive TPEs, especially in bumper systems in North America and for interiors in the major auto producing regions of the world. Consolidation, globalization and new competition along with the recycling pressure are changing the TPE supplier industry.

References

[1.] Handbook of Thermoplastic Elastomers, 2nd ed. Van Nostrand. [2.] Eller, R. "Plastics recycling and solid waste management in Japan," Plastics and the Environment Conference, New York, April 22, 1991. [3.] Eller, R. "The role of thermoplastic elastomers in automotive recycling," Schotland TPE Conf., Jan. 15, 1992. [4.] Purgly, E.P., Rader, C.P. and Gonzalez, E.A., Rubber and Plastic News. August 21, 1992, p. 15. [5.] Eller, R. and M. Kirsch, "Material substitution in global automotive bumper systems," SAE Technical Paper 880459. [6.] Eller, R., "Material Substitution in automotive interiors," SAE Technical Paper 870557. [7.] Reinhardt, H., "Copolyether-ester TPEs in V joint boots," Thermoplastics II Conference, April 7, 1989.