Gasoline barrier in a single layer

A single-layer extrusion blow molding machine has proven to be capable of molding HDPE barrier fuel tanks for small engines such as outboard motors through a joint effort by processor JSP Corp. (Tokyo) and materials supplier Mitsubishi Gas Chemical Co. (MGC; Tokyo).

Tank molded with single-layer die meets CARB requirements.

The two companies have developed material and processing technology that forms a barrier layer of MX-nylon between HDPE outer layers merely through extrusion through a mono-layer die. One of the first adopters is Suzuki in an outboard motor fuel tank, which is molded in Thailand.

A compatibilizer is employed in the HDPE/MX-nylon dry blend. And because a blend is employed, flash can be recycled back into the process. MGC recommends addition of at least 10% MX-nylon in the blend, although processors would always like to use less. Tanks molded with the technology meet the CARB standard for small engines.

According to Haruya Kubo, Manager of the Polymer Team at MGC, keys to realization of the barrier layer, whose form is in fact multiple striations of MX-nylon, are screw rotation speed and design and processing temperature.

Nylon-MXD6 is the generic name given to a wide range of polyamides produced from m-xylenediamine (MXDA). MGC's MX-nylon is  a crystalline polyamide produced by the polycondensation of MXDA and adipic acid.-mpweditorial@ubm.com