Engineering plastics

HDPE (High-Density Polyethylene)

Also: high-density polyethylene, PE-HD, PEHD, PE 300, polyethylene sheet, marine board, King StarBoard, Seaboard, PE4710 (pipe), HDPE cutting board, resin code 2

HDPE: cheap, chemical-proof, weldable polyethylene for tanks, cutting boards, marine parts and pipe. Soft and weak; it cannot be glued and moves with heat.

ASTM D4976 (polyethylene molding and extrusion materials)ASTM D3350 (PE pipe and fittings materials)FDA 21 CFR 177.1520 (olefin polymers)NSF/ANSI 51 (food equipment materials, listed products)

Sourcing HDPE parts or stock?

Attach a drawing (PDF or STEP) or describe the part; a U.S. shop that fits quotes it.

At a glance

HDPE (High-Density Polyethylene) typical properties
Density	0.95 g/cm³ (0.034 lb/in³)
Tensile strength	22-30 MPa (3.2-4.4 ksi) at yield
Yield strength	22-30 MPa (3.2-4.4 ksi) tensile yield
Hardness	Shore D 60-70
Elongation	Several hundred percent at break (typically above 300%)
Modulus of elasticity	0.8-1.2 GPa (0.12-0.17 Msi) tensile; flexural up to about 1.4 GPa (0.2 Msi)
Thermal	Melts at 126-135 °C (259-275 °F); continuous service about 70-80 °C (160-176 °F); stays tough well below -50 °C (-58 °F); HDT about 60-80 °C (140-176 °F) at 0.45 MPa
Composition	Polyethylene, (C2H4)n, with low chain branching and a density of about 0.94-0.97 g/cm3; natural, pigmented or UV-stabilized

Typical values, Natural extruded or compression-molded sheet, unfilled, 23 °C (73 °F). Confirm against the mill certificate and the purchase spec.

MachinabilityGood: Easy to cut, rout and saw, but soft, springy and heat-sensitive: chips string, parts move after unclamping, and size changes with shop temperature. ±0.13-0.25 mm (±0.005-0.010") is realistic.
WeldabilityExcellent: One of the most weldable plastics: hot-gas and extrusion welding for tanks and fabrications, butt fusion and electrofusion for pipe. Adhesive bonding is poor without flame or plasma treatment and a polyolefin adhesive; solvents do not bond it.
FormabilityGood: Thermoforms (vacuum and drape forming) and line-bends with heat; thin sheet cold-bends to curves. High shrinkage and elastic memory make formed parts less precise than acrylic or ABS.
Corrosion resistanceExcellent: Resists acids, bases, salts, salt water, alcohols and most solvents at room temperature, and absorbs essentially no water. Attacked by strong oxidizing acids; swelled by aromatic and chlorinated hydrocarbons, especially warm. Stressed parts can crack in detergents. Natural grades degrade in sunlight; use black or UV-stabilized colors outdoors.

High-density polyethylene is polyethylene with few side branches, so its chains pack into a denser, more crystalline structure (0.94-0.97 g/cm3) than low-density PE. The result is stiffer, stronger and more chemical-resistant, while staying inexpensive, tough, food-safe in natural grades and easy to weld. It is the baseline commodity plastic: bottles, tanks, pipe, cutting boards, marine hardware, playground panels and a long list of machined and fabricated parts.

For machined and fabricated parts, HDPE is bought as sheet and rod. It routes, saws and machines easily, is nearly impossible to glue, and is joined by plastic welding (hot gas, extrusion, butt fusion and electrofusion) or by fasteners. It absorbs essentially no water and shrugs off acids, bases and salt water, so it is the standard material for chemical tanks, marine and outdoor components (in UV-stabilized colored grades such as marine board), and food-contact surfaces.

Its limits are strength and dimensional stability. Yield strength is only about 22-30 MPa (3-4 ksi), the modulus about 1 GPa, service temperature about 80 °C (176 °F), and thermal expansion around 110-180 um/m·K, so HDPE parts are designed with clearance, slotted holes and generous tolerances. Where sliding abrasion is the problem, UHMW outlasts it; where stiffness or precision matters, use acetal or nylon.

Heat treatment

Not heat treated. For flat or precision machined parts, stress relieve blanks between roughing and finishing at roughly 90-110 °C (195-230 °F), hold about 30 minutes per 6 mm (1/4") of thickness, and cool slowly while supported flat.

Tempers and conditions

Natural (white, translucent)
Black UV-stabilized
Colored and color-core (two-layer) sheet
Marine-grade UV-stabilized board
FDA / NSF cutting-board sheet
Pipe grades (PE4710)
Reprocessed

Stock forms

Sheet and plate
Rod
Pipe and fittings
Film
Welding rod
Molding pellets (injection, blow and rotational molding)

Relative cost

Tier 1 of 5. The baseline: among the cheapest plastics per pound and per cubic inch. Marine-board and color-core sheet cost more; machining is quick.

Typical applications

Chemical and water tanks, sumps and liners
Cutting boards and food-processing surfaces
Marine hardware, boat parts and dock components
Water, gas and industrial pipe
Playground and outdoor furniture panels
Light-duty wear strips, guides and chute liners
Bottles, containers and blow-molded parts

Process compatibility

How HDPE takes each process, and what to specify. Each process links to its own guide and to the shops that do it.

HDPE (High-Density Polyethylene) process compatibility
Process	Rating	Notes
CNC Machining	GoodGood	Cheap and fast to machine; set tolerances around its expansion and springback.
CNC Milling	GoodGood	Routed from sheet on CNC routers with single- or O-flute cutters for marine and signage parts; vacuum hold-down.
CNC Turning	FairFair	Turns easily but chips string and diameters are hard to hold; UHMW, acetal or nylon rod usually suits turned parts better.
Waterjet Cutting	GoodGood	Clean, cold profiling of thick sheet; routing is usually cheaper for thin sheet.
Laser Cutting	PoorPoor	Melts and re-fuses into a rough, rounded edge and can flame; thin sheet only. Rout or waterjet instead.
Injection Molding	ExcellentExcellent	A major commodity molding resin, with blow and rotational molding for hollow parts; high shrinkage, so watch warp and tolerances.
FDM 3D Printing	PoorPoor	Shrinks and warps badly and will not stick to most print beds; print prototypes in PETG or polypropylene instead.
Vibratory Finishing	FairFair	Knocks down fuzzy burrs on small parts; routed parts are usually deburred by hand with a scraper.
Bead Blasting	PoorPoor	Too soft to blast usefully; media embeds in the surface.
Plating	Not recommendedNot recommended	Polyethylene cannot be plated, and paint adheres only after flame or plasma treatment; buy colored sheet instead.

Compare HDPE

HDPE vs UHMW

Design and sourcing tips

Design for expansion: at about 110-180 um/m·K, a 1 m (39") panel changes about 4-7 mm (0.16-0.28") over a 40 °C swing. Use slotted holes and floating mounts.
Tolerance general features at ±0.25 mm (±0.010"); call out tighter features individually and expect to pay for them.
Plan joints as welds or fasteners, not adhesives; weld-fabricated tanks and boxes are standard work for plastic fabricators.
Specify black UV-stabilized or marine-grade colored sheet for anything outdoors.
For food contact, specify natural FDA-compliant or NSF-listed sheet and ask for the certificate.
Use UHMW instead where the part slides against abrasive material; HDPE wears several times faster.

Frequently asked questions

Is HDPE food safe?: Natural HDPE made from resins that comply with FDA 21 CFR 177.1520 is widely used for food containers, cutting boards and processing surfaces, and NSF-listed cutting-board sheet is available. Pigments and recycled content can change that, so specify a food-contact grade and ask for the certificate.
Can HDPE be glued?: Not well. HDPE has very low surface energy and resists solvents, so most glues peel off. Flame, plasma or corona treatment followed by an adhesive made for polyolefins gives a usable bond. For structural joints, plastic welding or mechanical fasteners are far more reliable.
Can HDPE be welded?: Yes, very well. Fabricators hot-gas and extrusion weld HDPE sheet into tanks, ducts and boxes, and pipe is joined by butt fusion and electrofusion. A properly made butt-fusion joint is as strong as the pipe itself.
HDPE vs UHMW: which should I use?: Use HDPE for tanks, boards, marine parts, food surfaces and anything to be welded, molded or thermoformed: it is cheaper and easier to fabricate. Use UHMW for wear, such as chute liners, wear strips, guides and star wheels, where it lasts several times longer and absorbs impact better.
Is HDPE UV resistant?: Natural HDPE is not; it chalks and embrittles in sunlight. Black HDPE with carbon black, and UV-stabilized colored sheet such as marine board, last many years outdoors. Specify UV-stabilized material for any outdoor part.

Processes that commonly use it

Injection Molding

Related materials

UHMW Polyethylene (UHMW-PE)PVC (Rigid, Type 1)ABS Delrin (Acetal)Nylon 6/6

Where to verify these values

Resin producer HDPE data sheets (Dow, LyondellBasell, Chevron Phillips Marlex)
Sheet producer data (King Plastic, Röchling, Mitsubishi Chemical Advanced Materials)
ASTM D4976 and D3350
Plastics Pipe Institute Handbook of Polyethylene Pipe

HDPE (High-Density Polyethylene)

Also: high-density polyethylene, PE-HD, PEHD, PE 300, polyethylene sheet, marine board, King StarBoard, Seaboard, PE4710 (pipe), HDPE cutting board, resin code 2

HDPE: cheap, chemical-proof, weldable polyethylene for tanks, cutting boards, marine parts and pipe. Soft and weak; it cannot be glued and moves with heat.

ASTM D4976 (polyethylene molding and extrusion materials)ASTM D3350 (PE pipe and fittings materials)FDA 21 CFR 177.1520 (olefin polymers)NSF/ANSI 51 (food equipment materials, listed products)

At a glance

HDPE (High-Density Polyethylene) typical properties
Density	0.95 g/cm³ (0.034 lb/in³)
Tensile strength	22-30 MPa (3.2-4.4 ksi) at yield
Yield strength	22-30 MPa (3.2-4.4 ksi) tensile yield
Hardness	Shore D 60-70
Elongation	Several hundred percent at break (typically above 300%)
Modulus of elasticity	0.8-1.2 GPa (0.12-0.17 Msi) tensile; flexural up to about 1.4 GPa (0.2 Msi)
Thermal	Melts at 126-135 °C (259-275 °F); continuous service about 70-80 °C (160-176 °F); stays tough well below -50 °C (-58 °F); HDT about 60-80 °C (140-176 °F) at 0.45 MPa
Composition	Polyethylene, (C2H4)n, with low chain branching and a density of about 0.94-0.97 g/cm3; natural, pigmented or UV-stabilized

Typical values, Natural extruded or compression-molded sheet, unfilled, 23 °C (73 °F). Confirm against the mill certificate and the purchase spec.

MachinabilityGood

Easy to cut, rout and saw, but soft, springy and heat-sensitive: chips string, parts move after unclamping, and size changes with shop temperature. ±0.13-0.25 mm (±0.005-0.010") is realistic.

WeldabilityExcellent

One of the most weldable plastics: hot-gas and extrusion welding for tanks and fabrications, butt fusion and electrofusion for pipe. Adhesive bonding is poor without flame or plasma treatment and a polyolefin adhesive; solvents do not bond it.

FormabilityGood

Thermoforms (vacuum and drape forming) and line-bends with heat; thin sheet cold-bends to curves. High shrinkage and elastic memory make formed parts less precise than acrylic or ABS.

Corrosion resistanceExcellent

Resists acids, bases, salts, salt water, alcohols and most solvents at room temperature, and absorbs essentially no water. Attacked by strong oxidizing acids; swelled by aromatic and chlorinated hydrocarbons, especially warm. Stressed parts can crack in detergents. Natural grades degrade in sunlight; use black or UV-stabilized colors outdoors.

Typical applications

Chemical and water tanks, sumps and liners

Cutting boards and food-processing surfaces

Marine hardware, boat parts and dock components

Water, gas and industrial pipe

Playground and outdoor furniture panels

Light-duty wear strips, guides and chute liners

Bottles, containers and blow-molded parts

Process compatibility

How HDPE takes each process, and what to specify. Each process links to its own guide and to the shops that do it.

HDPE (High-Density Polyethylene) process compatibility
Process	Rating	Notes
CNC Machining	GoodGood	Cheap and fast to machine; set tolerances around its expansion and springback.
CNC Milling	GoodGood	Routed from sheet on CNC routers with single- or O-flute cutters for marine and signage parts; vacuum hold-down.
CNC Turning	FairFair	Turns easily but chips string and diameters are hard to hold; UHMW, acetal or nylon rod usually suits turned parts better.
Waterjet Cutting	GoodGood	Clean, cold profiling of thick sheet; routing is usually cheaper for thin sheet.
Laser Cutting	PoorPoor	Melts and re-fuses into a rough, rounded edge and can flame; thin sheet only. Rout or waterjet instead.
Injection Molding	ExcellentExcellent	A major commodity molding resin, with blow and rotational molding for hollow parts; high shrinkage, so watch warp and tolerances.
FDM 3D Printing	PoorPoor	Shrinks and warps badly and will not stick to most print beds; print prototypes in PETG or polypropylene instead.
Vibratory Finishing	FairFair	Knocks down fuzzy burrs on small parts; routed parts are usually deburred by hand with a scraper.
Bead Blasting	PoorPoor	Too soft to blast usefully; media embeds in the surface.
Plating	Not recommendedNot recommended	Polyethylene cannot be plated, and paint adheres only after flame or plasma treatment; buy colored sheet instead.

Design and sourcing tips

Design for expansion: at about 110-180 um/m·K, a 1 m (39") panel changes about 4-7 mm (0.16-0.28") over a 40 °C swing. Use slotted holes and floating mounts.

Tolerance general features at ±0.25 mm (±0.010"); call out tighter features individually and expect to pay for them.

Plan joints as welds or fasteners, not adhesives; weld-fabricated tanks and boxes are standard work for plastic fabricators.

Specify black UV-stabilized or marine-grade colored sheet for anything outdoors.

For food contact, specify natural FDA-compliant or NSF-listed sheet and ask for the certificate.

Use UHMW instead where the part slides against abrasive material; HDPE wears several times faster.

Frequently asked questions

Is HDPE food safe?

Natural HDPE made from resins that comply with FDA 21 CFR 177.1520 is widely used for food containers, cutting boards and processing surfaces, and NSF-listed cutting-board sheet is available. Pigments and recycled content can change that, so specify a food-contact grade and ask for the certificate.

Can HDPE be glued?

Not well. HDPE has very low surface energy and resists solvents, so most glues peel off. Flame, plasma or corona treatment followed by an adhesive made for polyolefins gives a usable bond. For structural joints, plastic welding or mechanical fasteners are far more reliable.

Can HDPE be welded?

Yes, very well. Fabricators hot-gas and extrusion weld HDPE sheet into tanks, ducts and boxes, and pipe is joined by butt fusion and electrofusion. A properly made butt-fusion joint is as strong as the pipe itself.

HDPE vs UHMW: which should I use?

Use HDPE for tanks, boards, marine parts, food surfaces and anything to be welded, molded or thermoformed: it is cheaper and easier to fabricate. Use UHMW for wear, such as chute liners, wear strips, guides and star wheels, where it lasts several times longer and absorbs impact better.

Is HDPE UV resistant?

Natural HDPE is not; it chalks and embrittles in sunlight. Black HDPE with carbon black, and UV-stabilized colored sheet such as marine board, last many years outdoors. Specify UV-stabilized material for any outdoor part.