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July 1, 2008

5 Min Read
New blowmolding grades target variety of uses

Blowmolders have had their choice of materials expanded substantially in the past few months, including a number of grades launched at the ‘plastics in automotive’ conference in Mannheim, Germany this spring.

Dow Automotive’s Pádraig Naughton stands beside (from bottom to top) four progressively more complex blowmolded PC/ABS seatbacks.

At that event, Pádraig Naughton, engineering leader for Dow Automotive (Auburn Hills, MI), said his firm expects its recent integration of its automotive plastics operations with its polyurethane foam division will help it get even more commercial applications of the blowmolded rear seatbacks it developed with processor Möller Tech (Bielefeld, Germany).

These seatbacks already are commercial in the Audi TT and Audi A3 Cabrio. Two other cars entering start of production (SOP) this year also will include the seats, again blowmolded by Möller Tech and all using Dow’s Pulse PC/ABS. The two new vehicles’ seatbacks will have headrests integrated into them, which the current commercial versions do not. Seats so far have been for small vehicles with 50:50 rear seat splits, “but we’re developing for the 60:40 split,” says Naughton, referring to the one large seat/one small seat split seen in the backs of most passenger cars. In every case, about 20-25% of seatback weight has been reduced, and Naughton predicts the weight reduction will be even greater for 60:40 rear seats. Dow owns the patents for the application, and he says it has seen tremendous interest from carmakers in North America and Japan.

Also at that event, plastics supplier Lanxess (Leverkusen, Germany) introduced a range of PA 6 and 66 grades marketed for processing of parts used in engine air management, such as air supply lines, charge-air pipes, and intake air lines. They process via standard or sequential extrusion blowmolding, or suction blowmolding. The PA 66 grades can withstand peak loads of 200°C. The nonreinforced PA 6, Durethan DP BC 600 HTS, has an elasticity modulus of only about 350 MPa (conditioned), meaning it can be suction blowmolded as a single-material solution, for example to make charge-air pipes with integrated flexible bellows. To date, these are sequentially blowmolded of two polyamides of differing hardness. “With this innovation, we are responding to the increasing trend toward turbocharged engines in which the charge-air pipes incorporate flexible bellows,” said Ralf Zimnol, head of application development-automotive for semicrystalline materials.

PS, OPP touted as PET, maybe even HDPE replacements

Container Corp. of Canada and LyondellBasell are making a run at PET and other materials with oriented polypropylene, with commercial use expected late this year.

BASF (Ludwigshafen, Germany) is pondering the sale of its commodity styrenics sector, but that hasn’t slowed developments there. The supplier has developed an impact-resistant polystyrene, called BX 3580, which is marketed as an alternative to PET and HDPE for blowmolded packaging. The material can be processed on injection blowmolding and injection stretch blowmolding units, as can PET. The supplier predicts it may find application in bottles for milk and yoghurt beverages—commonly extrusion blowmolded of HDPE or stretch blowmolded from PET. Polystyrene’s lower density compared to PET’s means processors likely can cut material use by up to 25%. Also, PS does not require drying: PET does. Whether brand owners will approve a shift from PET, easily recycled and thus viewed as an environmentally friendly material, is of course the big question.

Blowmolded packaging processor Container Corp. of Canada (CCC; Richmond Hill, ON), has chosen Pro-fax X11540-81-3, a custom-oriented polypropylene experimental grade from LyondellBasell Industries (Rotterdam, the Netherlands), for use in the commercial production of oriented PP (OPP) hot-fill jars and bottles. Until now, blowmolded PP applications generally have been limited to water bottles, pill vials, and other containers where oxygen barrier properties were not critical. According to LyondellBasell, its new material could help OPP compete more readily with PET, glass and other materials in a broader spectrum of applications.

CCC’s new packaging, called Enviroclear Barrier System, makes use of a barrier coating developed by South Africa’s Council for Scientific Industrial Research (CSIR). A dip/spray process is used to coat the bottles; coating improves the oxygen barrier on a 500-ml OPP bottle by approximately 140 times over an uncoated PP version, according to Lorie Struzik, technical program manager at LyondellBasell. That also gives the bottles about 10 times the barrier protection of an uncoated PET bottle. The bottles are said to be as clear as PET with no need for peroxide to enhance OPP’s melt flow.

According to the supplier, the material’s adhesion properties are such that the coating does not rub off when bottles bump against each other. Various applications are currently being tested with commercialization expected toward the end of 2008.

Masterbatch keeps head tooling clean

A proprietary additive is said to offer extrusion blowmolders help in eliminating the amount of colorant and burnt material deposited in an extrusion head during production. The additive is available as a standalone masterbatch or can be added to other color masterbatches supplied by colorant supplier Ampacet (Tarrytown, NY).

According to Morgan Gibbs, director of technical service and development at Ampacet, the product, known as 100458, helps keep material from burning and also helps clear any burnt or charred material from a machine’s screw, barrel, and head. He says the additive is akin to a purging agent, as used in injection molding, but in contrast, can be added to the colorant during processing. The additive can reduce blowmolders’ color changeover times by 50% or more, he says.

Doug Brownfield, Ampacet strategic business manager, adds that part quality also shows improvement, since elimination of contamination in the extrusion head tooling permits die lines to disappear. Gibbs cites an unidentified customer running an 8-head Uniloy machine processing 1-gal bottles who, after using the additive, saw scrap drop by 50% and also was able to run material at a slightly lower temperature, thus improving bottle trimming.

Using the additive “is a no-brainer when using higher-end colorant masterbatches or for high-volume processing,” states Gibbs. “You probably want to use it every time you run a pearlescent or a metallic.”

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