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SAFOAM®/SAFTEC® can be used in blow-molding. Weight reductions of 5-15% have been achieved. Specific grades depend on the resin(s) used. Blow molding is a two-stage process. A hot tube, or parison, is extruded and then molded by inflation within a mold. The general principles for successful extrusion apply to the parison. A parison can be made in one of two ways:

1. Continuous Extrusion (similar to pipe extrusion) or
2. Intermittent Extrusion

With intermittent extrusion, the melt must be kept under pressure to prevent premature cell formation, resulting in poor or rough surface. As soon as the parison exits the die, expansion and cell formation occur. The die and pin diameter must be adjusted to compensate for expansion. The die diameter must be reduced and the pin diameter increased. Conventional molds are employed (i.e. stationary, reciprocating, or rotary). Since the hot strength of the melt is lower, mold release may be required on the hot knife or wire to obtain a clean cut-off. The blow-pressure may have to be reduced to avoid wall rupture.

PROCESS

The foam blow molding process is capable of producing a skin-foam wall structure that can vary. The cell structure and size of the foam layer can be influenced by the amount of blowing concentrate used, as well as the processing parameters. The cell structure produced is a "closed cell".

A foam blow-molding machine is used. Typically, two extruders run, one for the skin layer and the other for the foam layer. It is possible to use two extruders (one for each layer) when running both internal and external skins.

KEY ADVANTAGES:

Foam blow molding has the following key advantages:

1. High strength to weight ratio in the molded products
2. Increase in product rigidity (stiffness)
3. Reduction in noise levels
4. Weight reduction
5. Improved economics
6. One step process for manufacturing

Applications include collapsible containers and retail boxes, pallets, air ducts for automotive, partitions and panels, etc.