HDPE High Density Polyethylene Sheet
Comprehensive technical specification for HDPE (High Density Polyethylene) sheet material – covering tensile properties, dimensional tolerances, machinability parameters, defect thresholds, and best practices for storage and racking. For use in industrial procurement, machining, and fabrication environments.
Material Overview & Common Uses
HDPE (High Density Polyethylene) is a semi-crystalline thermoplastic with a density typically between 0.941–0.965 g/cm³. It offers excellent chemical resistance, low moisture absorption, high impact strength, and good fatigue resistance. Common applications include food-grade cutting boards, chemical tank linings, marine bumpers, conveyor wear strips, fluid handling components, and structural spacers in corrosive environments. HDPE sheet is supplied in thicknesses from 1.5 mm to 50.8 mm (0.060″–2.000″) and standard panel sizes 48″×96″ or 60″×120″.
Core Technical Properties & Sizing
| Property | Value / Specification |
|---|---|
| Density (ASTM D792) | 0.941 – 0.965 g/cm³ |
| Tensile Strength at Yield (ASTM D638) | 20 – 37 MPa |
| Elongation at Break | 100 – 600 % |
| Flexural Modulus (ASTM D790) | 0.8 – 1.2 GPa |
| Melting Temperature (DSC) | 125 – 135 °C |
| Continuous Service Temperature (air) | 80 – 100 °C |
| Thermal Conductivity | 0.44 – 0.52 W/(m·K) |
| Water Absorption (24 hr immersion, ASTM D570) | < 0.01 % |
| Flammability (UL 94) | HB |
| Standard Sheet Dimensions | 48″ × 96″ (1219 mm × 2438 mm); 60″ × 120″ (1524 mm × 3048 mm) |
| Thickness Tolerances (1.5 – 6 mm) | ±0.25 mm |
| Thickness Tolerances (6 – 25 mm) | ±0.38 mm |
Machinability, Tooling & Feeds
HDPE is soft and low-strength relative to metals, but its low melting point and high thermal expansion demand attention. Use sharp, polished carbide tooling (uncoated) with positive rake angles. Avoid high cutting temperatures which cause melting and surface smearing. For drilling, use parabolic-flute drills with slow entry/exit. For routing, climb milling is preferred.
Recommended Cutting Parameters (Carbide Single‑Point)
| Parameter | Hobby / One‑Off | Production (CNC) |
|---|---|---|
| Cutting Speed (m/min) | 150 – 250 | 250 – 400 |
| Feed per Tooth (mm/tooth) | 0.15 – 0.30 | 0.20 – 0.50 |
| Depth of Cut (mm) | 0.5 – 2.0 | 1.0 – 3.0 |
| Coolant | Air blast or mist | Mist (water‑soluble, 5–8 % concentrate) |
| Recommended Tool | Uncoated carbide, 3‑flute | Uncoated carbide, 3‑flute or diamond‑polished |
> Note: reduce rpm if edge melting occurs. Chip loads above 0.50 mm/tooth can cause edge chipping in thin sections.
Common Defects & Quality Control
| Defect | Description | QC Method / Rejection Criterion |
|---|---|---|
| Warpage | Bowing greater than 1.5 mm across 1 m length (ASTM D1182) | Visual / straightedge; reject if exceeds 1.5 mm/m |
| Surface Stress Cracking | Fine cracks near edges after machining or exposure to stress‑cracking agents | Visual with 10× loupe; reject any visible crack |
| Inclusions / Contamination | Black specks, gels, or unmelted resin particles > 0.5 mm | Visual per 200 cm² sample; permit max 2 specks >0.3 mm per 200 cm² |
| Thickness Variation | Deviation outside per‑sheet tolerance (see Core Properties table) | Micrometer (≥5 points spread); reject if any point exceeds tolerance |
| Color Inconsistency | ΔE > 1.5 vs. approved standard (natural HDPE: off‑white/translucent) | Spectrophotometer CEILAB; reject if ΔE > 1.5 |
| Impact Damage (edge/corner) | Chipped corners or edge cracks > 3 mm deep | Visual; reject any damage > 3 mm |
Storage, Handling & Racking Guidelines
HDPE requires careful horizontal storage to avoid warping. Stack sheets on flat, clean pallets. Place intermediate corrugated sheets if stacking more than 6 ft high. Protect from UV (sunlight) – prolonged exposure causes surface discolouration and embrittlement. Maintain indoor storage temperature 15–25 °C; avoid proximity to heat sources (>80 °C). In humid environments, no special dehumidification needed due to extremely low water absorption.
Recommended Storage Conditions
| Parameter | Specification |
|---|---|
| Storage Temperature | 15 – 25 °C (59 – 77 °F) |
| Relative Humidity | 20 – 65 % RH (no condensation) |
| UV Protection | Store under opaque tarp or indoors; max daily exposure 1 hr indirect light |
| Maximum Stack Height | 1.2 m (48″) for 6 mm sheets; 1.8 m (72″) for thickness >12 mm |
| Rack Type | Consider cantilever rack or flat horizontal shelving with solid decking |
| SupplyGrid Reorder Point | Minimum 2 sheets at current consumption rate (calculate using Reorder Mode in SupplyGrid) |