Thermoplastic material and It’s Process
PBT (Polybutaline phthalates):
Typical Application:
- Household appliance (Example: food processor, blades, vacuum cleaner parts, fans, heir drier housing, coffee makers)
- Electronics (Example: switches, motor housings, fuse cages, key caps for computer, connectors, fiber optic, buffer tubing)
- Automotive (Example: grilles, body panels, wheel covers, and components for doors and windows)
Injection molding processing conditions:
| Drying | This material is sensitive to hydrolysis at high temperatures. It is therefore important to dry the material prior to molding. Suggest drying condition (in air) is 120 deg c for 6-8 hours (or 150 deg c for 2-4hrs). Moisture levels must be below 0.03%. When using a desiccant dryer, drying at 120 deg c for 2.5 hours is recommended. |
| Melt temperature | 225-275 deg c “Aim 250 deg c “ |
| Mould Temperature | 40-60 deg c for unreinforced grades. For other grades, a wide range of temperature can be used, depending on the grade (15-120 deg c). Cooling channels should be properly designed to minimize part war page. The heat removal must be fast and uniform. Cooling channels of 12mm diameter are recommended. |
| Injection Pressure | Moderate (up to maximum of 1500 bar/21750 psi) |
| Injection Speed | Fastest possible speeds should be used (due to first solidification of PBT’s) |
Runners & Gates:
Full round runners are recommended to impacts maximum pressure transmission (Rule of thumb: runner diameter = part thickness + 1.5mm). A wide variety of gates may be used. Hot runners may also be used, taking care to avoid drool and material degradation. Get diameters or depths should preferably be between 0.8 to 1.0t where “t” is the part thickness. When using submarine gates, the minimum recommended diameter is 0.75mm.
HDPE (High density polyethylene):
Typical Application:
Measure use in below molding application such as
- Containers, refrigeration units
- Storage vessels
- Household goods (Kitchen ware)
- Self caps
- Bases for PET bottles
Injection Moulding Processing Conditions:
| Drying | Not normally necessary if stored properly |
| Melt temperatures | 220-260 deg c “ for high molecular weight resin, the suggest melt temperature range is 200-250 deg c |
| Mold Temperature | 50-95 deg c (Higher temperatures for wall thickness of up to 6mm “lower temperature for wall thickness greater than 06 mm) |
The cooling rate should be uniform to minimize shrinkage variations. For optimum cycle times, the cooling channel diameters should be at least 08mm and must be within a distance of 1.3d from the mould surface (where “is the diameter of the cooling channel”)
| Injection Pressure | 700-1050 bar (10000-15000 psi) |
| Injection speed | Fast injection speeds are recommended profiled speeds reduce warpage in the case of components with a large surface area |
Runners & Gates:
Diameters of runners range from 4-7.5mm (typically 6mm). Runner lengths should be has sort has possible. All types of gates may be used. Gate lands should not exceed 0.75mm in length. Ideally suited for hot runner moulds ‘ an insulated hot tip runner is preferred when there are frequent color changes.
LDPE (Low density polyethylene):
Typical Application:
- Closers
- Bowls
- Bins
- Pipe couplings
Injection Molding Processing Conditions:
| Drying | Not usually necessary |
| Melt Temperature | 180-280 deg c |
| Mold Temperature | 20-40 deg C |
For uniform and economic heat removal, it is recommended that the cooling channel diameters. Be at least 8mm and the distance from the surface of the mould to the edge of the cooling channel be not more than 1.5 times the diameter of the cooling channel.
| Injection Pressure | Up to 1500 bar (21750 psi) |
| Back Pressure | Up to 750 bar (10850 psi) |
| Injection speed | Fast speeds are recommended profiled speeds can limit warpage problems of large surface area parts |
Runners & Gates:
All conventional types may be used: LDPE is well suited for hot runner mold. Insulated hot tip runners are preferred for frequent color changes.
