Topics for a Hot Industry

To know where you’re going, someone once said, you have to know where you’ve been. The insight seems especially relevant to the plastics industry, which over the past two decades has witnessed unprecedented growth. As we head into the next century and a new millennium, the timing is right to step back and assess the state of the industry. Such an exercise can be useful, of course, because even our most faithful of readers do not retain detailed knowledge of every tidbit, especially if it’s outside the area of their immediate interest. A summary can also serve as a strategic benchmark for our reader’s own operations. Here then is the editor’s overview of plastics–where it’s been and where it’s going.

Automotive

Plastics use in cars is up 600 percent since the early ’70s and will most likely continue to grow. The reasons are fourfold: cost reduction, product distinction, part consolidation and weight decrease.

Automotive designers are using a systems approach and new materials to augment the amount of plastics in today’s cars. Interiors will continue to evolve as suppliers seek ways to take out cost and consolidate parts. For example Lear is developing seat systems for various models of cars using standard components, such as blow-molded seat backs and cushions. The approach allows the manufacturer to combine distinctive styling with reduced parts inventory and assembly costs. In light of GM’s recent announcement to phase out PVC in its vehicles, materials substitution will be an on-going strategy as designers face pressure to reduce the number of different types of resin.

The highest growth areas for plastics over the next decade will be exterior body panels, under-the-hood applications and gas tanks. One study has estimated that plastics use in exterior applications will increase from 700 to 900 million lb./yr. by the year 2002. The estimate could be conservative, especially if several current development projects attempting to perfect the use of a nanocomposite filler to improve the structural properties of TPO prove successful. Early results are promising, according to one industry executive. Also, DaimlerChrysler has announced ambitious plans to make PET body panels for a four- to 12-piece car body using a 8800-ton Husky injection molding machine.

Manifolds (nylon) and fuel systems (HDPE) will account for over half the total resin growth in under-the-hood applications over the next five years, according to a study done by Business Communications Company (Norwalk, CT). Thermoplastic elastomers will also show significant growth, the study predicts (see Table 1).

In the long-term, plastics could see more use in non-traditional areas such as power train applications and structural parts. The 1999 Jeep Grand Cherokee, for example, features the first integrated transfer case/automatic shifter assembly made with nylon 6/6. Owens Corning and DSM have launched an initiative to expand use of long-fibre reinforced polypropylene for molding large structural parts to replace metal.The key to the development of this technology is a polymer coating from Owens Corning which when applied to long-glass fibres improves bonding with the base resin.

Packaging

For a number of reasons, the much-hyped metallocene or single-site catalyst revolution has been slow to develop. Some industry analysts now doubt if more costly metallocenes will ever capture the market share once, if not explicitly predicted, implied.

Many film converters and their resin suppliers have spent years and lots of money in developing high-performance grades of conventional Ziegler-Natta catalyzed LLPDE specifically geared to their lines and products. It has also been shown that the viscosity and tackiness characteristics of metallocene-catalyzed resins require higher extruder pressures and other adjustments to equipment before running. Additionally, studies have shown that the machine-direction tear strength of garbage bags made with certain metallocene-made resins is much lower than the transverse direction tear strength, a shortcoming that may offset the resins’ superior dart impact strength in these applications.

Yet, it should also be noted that not all metallocene-made resins are equal–Dow’s mLLDPE ELITE polymers, for example, are made by a solution phase process, whereas Exxon’s line of mLLDPE Exceed resins are produced by a gas-phase process. Exxon’s technology produces resins with a very narrow molecular weight distribution and less long-chain branching than Dow’s, and some extruders have found Exxon’s mLLDPE more difficult to process. Additionally, Dow has recently announced that it is offering new lines of its metallocene-grade AFFINITY polyolefin plastomers containing an optimized slip and antiblock formula which could improve processability of these resins.

Metallocene-catalyzed resins have made inroads in a number of applications; most specifically in lamination film (as a substitute for EVA), film for form-fill-seal applications (where higher line speed is a benefit) and film for heavy duty shipping bags (where metallocenes’ improved sealability is a plus in dusty environments). Some converters have taken to the resins more readily than others. Uniplast Industries (Orillia, Ont.) reports that it is running metallocene-grade resins on about 25 percent of its extrusion lines. Uniplast (see Canadian Plastics, April 1998) has invested in an on-site laboratory to assist in the development of metallocene-made grades specifically tailored to their equipment and product lines.

In other packaging trends, glass replacement in high temperature food applications will continue to be a long-term objective of packagers and end-users. Glass, after all, is heavier and it breaks. Conversions will ultimately depend on market acceptance and on-going improvements in technology to improve performance and lower costs. Amcor PET Technologies has been testing a new cryogenic blow molding technology (see Canadian Plastics, October 1998) which uses liquid nitrogen to rapidly cool the PET after molding, setting up a “crystallinity” gradient. If successful the technology, or a variation of it, could expand PET use for hot-fill applications. In another area, PET barrier technology has improved beer shelf-life in PET from three to six months. A number of brands of beer are now being bottled in PET and sold in Australia and England.

Form-fill-seal (FFS) applications are growing in leaps and bounds and will continue to do so. FFS, a process which starts with a roll of printed film, converts film into a bag and then fills the bag in one continuous process, uses less material and reduces waste in comparison to other packaging (see Canadian Plastics, August 1999). Growth in FFS packaging, such as bags for milk, juices, cereal and chips, is being aided by the favorable economics and efficiencies of new FFS machines, some of which can produce up to 10 or 12 bags per draw, at rates of up to 70 draws per minute.

The application of metallocene technology is not limited to PE resins for making film or other packaging. Various companies are pursuing commercial development of metallocene-made polypropylene in order to achieve two properties once thought to be mutually exclusive in PP: high clarity and good stiffness and abrasion resistance. A joint-venture subsidiary of BASF and Hoechst, Targor, has reportedly successfully developed an injection molding grade of mPP with both properties. Another benefit of mPP is said to be its softer feel, a feature which may prove useful in non-woven fibre applications, such as diapers.

Dow’s line of metallocene-based QUESTRA crystalline polymers may be the “sleeper” resin heading into the next century. Targeted at both medium- and high-heat connector applications in electronics, QUESTRA is said to have better heat resistance than PBT and nylon, while being less expensive than LCP and PPS (see Canadian Plastics, July 1999). Both features would place the resin in a good position to compete for market share as this market is being driven by so-called surface mount technology, which allows manufacturers to pac
k more components on a given area of board, but requires much higher heat to manufacture.

Use of thermoplastic elastomers (TPEs), which can be made either by conventional means or by using single-site catalyst technology, has been growing at a rate which exceeds the growth rate of any other plastic material by several fold (see Canadian Plastics, June 1999). One of the highest growth areas for TPEs has been replacement of rubber in automotive seals and weather stripping. TPEs are also seeing tremendous growth as a material in over-molded “soft touch” applications such as tooth brush handles, as well as athletic shoes and a host of consumer goods. In effect, TPEs bridge the gap between rubber and hard plastic, while affording recyclability and faster cycle times in comparison to either TPUs or EPDM.

About seven percent of U.S. molders currently report gas assist (GA) capability and this figure is expected to grow. One source estimates that as much as 10 percent of injection machines sold in the future will come with an option to run gas assist. An ease in the threat of patent disputes to processors using GA should spur the growth in the number and types of GA applications (see Canadian Plastics, April 1999). Gas assist offers molders several unique benefits, including the possibility of adding one-third or more effective press tonnage without modifying standard machinery components. Gas-assist molding can also eliminate warpage, sink marks and reduce material usage, advantages that are coming to be more appreciated as GA equipment becomes more user friendly and off-the-shelf.

When Milacron’s Barr Klaus predicted at the 1997 NPE that 70 to 75 percent of all injection molding machines below 800 tons sold in developed countries would be all-electric in 10 years, it sent many a molder off to make return-on-investment analysis of electric vs. hydraulic machines. All-electric machines provide acknowledged savings on electricity consumption, water usage and hydraulic oil, and some gain in cycle time and improved machine repeatability. One study done by Ube Machinery Inc. (see Canadian Plastics, September 1999) compared costs for molding an identical part on a 720-ton hydraulic vs. a 720-ton all electric and calculated a net yearly savings of over $38,000 in favor of the all-electric. Many molders have said they value electric machines as much for quieter, cleaner operation as cost savings.

For the time, hydraulic machines still dominate in the clamping force range of 500 tons and above. Van Dorn Demag’s Scott Kroeger, product manager, large machines, says one of the reasons hydraulic machines’ remain popular with many molders is their reliability and simplicity (See Canadian Plastics, February, 1999). Kroeger says molders still like the direct hydraulic pressure feedback for tonnage control.

High-volume, high-end applications for thinwall injection molding, where the L/D ratio is in the range of 100 to 200, is becoming less esoteric and more mainstream thanks to advances in machinery, hot runner systems and design principles. Newer applications for the practice of thinwall molding include computer monitor housings, which are getting bigger, and car parts such as bumpers and under-the-hood parts. A hot runner system equipped with sequential valve gating can play a crucial role in successful thinwall molding on conventional machines at injection pressures in the range of 20,000 psi. The main advantages of thinwall molding are materials savings and shorter cycle times.

The huge growth in blow molding applications in the automotive, consumer and appliance sectors seen over the past decade will continue, largely because blow molding affords several significant advantages, such as savings on tooling costs, as well as weight and part reduction (see Canadian Plastics, May 1999). This growth has been driven by advances in design software and machinery. Machines that incorporate 3D sequential blow molding can make parts with rigid and soft regions, for example auto manifold ducts which integrate bellows and resonator sections. CPL