A. Demirer et al. / Materials and Design 28 (2007)   1467–1476 1469

Fig. 1.  The drawing and the general view of injected part adopted in the study.

Table 1

Specifications of the moulding  materials

Name of material Acrylonitrile butadiene styrene Polyprophylene

Symbol ABS PP

Commercial name Cycolac GE Petoplen MH418

Manufacturer GE Plastics Petkim A.S.

Resin type Amorphous Semi-crystaline

Density 1.05 g/cm3 0.91 g/cm3

Melt flow index 3.7 g/10 min (230 °C/3.8 kg) 4–6 g/10 min (230 °C/2.16 kg)

Process temperature 220–280 °C 170–260 °C

Tensile strength 17–58 MPa 30–40 MPa

Modulus of elasticity 2800 MPa 1250 MPa

moulding area for ABS and PP when using HRS and CRS (i.e., bottom in Fig.  2).

When using CRS, the flow of molten plastic becomes more difficult because of the heat dissipating in the runner channels. In addition, increase in flow length increases the frictional pressure losses. Using HRS provides    significant

pressure gain by eliminating the  disadvantages  of CRS. PP material was injected at temperatures of 170, 200 and 260 °C, and at pressures shown on the diagram in Fig. 4. It was observed that significant pressure gain was provided when using HRS. At mean process temperature of 200 °C, e.g., the required average injection pressure is 70 MPa   for

1470 A. Demirer et al. / Materials and Design 28 (2007) 1467–1476

Table 2

Experimental conditions for injection moulding  process

Base polymer Process Injection pressure (MPa) Packing Mould Cycle Injection

temperature (°C) HRS CRS pressure (MPa) temperature ( °C) time (s) velocity (m/s)

ABS 225 60, 70, 75, 80,  90 70, 85, 95,  110 %  50  of injection 40 50 0.012

245 50, 65, 80 70, 100 pressure

260 40, 75 60, 90

280 30, 40, 60