Polyethylene Powder for Rotomoulding: LDPE Pellets Cut to -30 Mesh in an Air-Cooled Mill (Feder, Wedco, US 3,428,260)

Rotational moulding needs polyethylene as a fine, free-flowing powder, but grinding heats the plastic until it softens and clogs the mill. Feder's mill throws the pellets off a fast impeller into toothed cutters, while the impeller itself pumps air through to keep the particles cool. Result: low density polyethylene powder, -30 mesh, well suited to rotational moulding. Source: Feder, US 3,428,260 (Wedco, 1969), Operating Example. Picture drawn by Youblob.

متقدم

Factory process

التعليمات

Fit cutters for the mesh

Use 12 in cutters with 480 cutting edges for a -30 mesh product (240 edges give -12 mesh). Edges at 60° with a 0.010 in flat; a razor edge would not last. Clearance to the housing 1/4 in.

الأدوات المطلوبة:

مطحنة

Run the impeller and cutters

Drive the 18.5 in impeller at 2700 rpm and the cutters at 4200 rpm. The impeller pumps air through the housing, which cools the particles while they are cut.

الأدوات المطلوبة:

مطحنة

Feed the pellets

Feed low density polyethylene pellets about 1/8 in across, in open circuit, at about 150 lb per hour; more overheats the plastic.

المواد لهذه الخطوة:

حبيبات LDPE1 as required

الأدوات المطلوبة:

مطحنة

Collect the powder

Particles small enough pass the screen round the housing; the mill's own air carries them to a cyclone about 10 ft above it. The size spread is narrow, with few fines.

الأدوات المطلوبة: