The short answer
Extrusion coating LDPE is a higher-melt-index LDPE, typically about 4–8 g/10 min at 190°C / 2.16 kg, with density around 0.918–0.925 g/cm³. It is made for low neck-in and good draw-down at line speed, and most grades carry no slip or antiblock. Buy it by melt index, density, the substrate you coat and the producer’s FDA letter if it touches food.
This page covers LDPE for extrusion coating and extrusion lamination only. For all LDPE film grades, see LDPE film grades. For blown film, see LDPE blown film resin.
Typical spec window
| Property | Typical range | Test method |
|---|---|---|
| Melt index | About 4–8 g/10 min for most paperboard and foil coating; some grades run higher | ASTM D1238 or ISO 1133, 190°C / 2.16 kg |
| Density | About 0.918–0.925 g/cm³ | ASTM D1505 or D792; ISO 1183 |
| Melting point | About 105–115°C / 221–239°F | DSC, ASTM D3418 or ISO 11357-3 |
| Slip and antiblock | None in most coating grades | Stated on the data sheet |
| Neck-in and draw-down | Grade-specific; there is no single standard value | Measured on a coating line by the producer |
Typical ranges from published data sheets for grades in this window. Your grade’s own data sheet and the lot COA are what count.
What it’s used for
- Paperboard for cups, cartons and food trays, coated on one or both sides
- Liquid packaging board, where the LDPE layer gives the moisture barrier and the heat seal
- Foil and film laminations, with LDPE as the bonding layer between two webs
- Multiwall sack paper, wraps and release-liner base paper
- Coated woven fabric for sacks and tarps
How to tell grades apart
Inside the 4–8 MI window, grades differ mainly in how the melt behaves in the air gap between the die and the nip.
- Neck-in. How much narrower the curtain gets than the die. Lower neck-in means less edge trim. Coating grades are often made in autoclave reactors, which gives the broad molecular weight distribution and long-chain branching that hold neck-in down.
- Draw-down. The thinnest coat the grade can pull at line speed before the edges weave or the curtain tears. Higher MI usually draws down further but necks in more.
- Adhesion. LDPE bonds to paper and foil through surface oxidation in the air gap, so coating lines run hot, often above 300°C / 572°F. Grades with little or no antioxidant bond more easily but give more smoke and odor.
- Odor and taste. Grades for liquid and food packaging are made and tested for low odor and taste.
- Heat seal. Lower density seals at a lower temperature. Blends with LLDPE or metallocene PE raise seal strength and hot tack.
What to put on your RFQ or PO
- Melt index with the condition. MI at 190°C / 374°F and 2.16 kg (ASTM D1238), nominal value and spec range.
- Density. By ASTM D1505, with a range.
- Process and substrate. Coating or lamination; paperboard, foil, film or woven fabric; coat weight and line speed.
- Additives. Usually none. Say if slip and antiblock must be absent, and if you need antistat, UV or extra antioxidant for your end use.
- Color. Natural for most coating. If you add a white or color concentrate, name its carrier resin.
- Food contact. The producer’s FDA letter for the exact grade; PE letters usually cite 21 CFR 177.1520. Put odor and taste limits in writing.
- COA values to check. MI and density on every lot, plus gel count if the grade lists it.
- Packaging. Lined gaylords (box fiber is a common source of gels), bulk truck or railcar. LDPE pellets run about 31–36 lb/ft³.
- Quantity and release size. Total quantity, how much per release and how often.
A polymer chemist reviews every request and checks the grade against your process before we quote. Every prime lot from our suppliers ships with a COA, and orders start at one gaylord.
Get an email when resin prices move
A short note when PP, PE, nylon or other prices shift. No spam; unsubscribe anytime.
By signing up you agree to receive emails from ResinBridge. Unsubscribe anytime by replying or using the link in any email. PrivacyEquivalents and substitutes
- Another coating LDPE at the same MI and density. The closest swap. Run a coating trial and check neck-in, adhesion and odor before you approve it.
- LDPE blended with LLDPE or metallocene PE. For stronger seals and hot tack. The blend necks in more, so most lines keep LDPE as the main part.
- Tubular-reactor LDPE at the same MI. Usually necks in more than an autoclave grade, though some tubular grades are made for coating. Do not assume a drop-in.
- Acid copolymers or ionomers. Used as a tie or sealant layer for better adhesion to foil. A different material, not a straight swap.
Common processing problems
- Gels and specks in the coating: gels and fisheyes and black specks
- Weak or leaking seals on cups and cartons: heat seal failures
- Streaks and lip build-up: die lines and build-up
- Coat weight that swings: extruder surging
Common questions
What melt index LDPE is used for extrusion coating?
Most paperboard and foil coating runs on LDPE of about 4–8 g/10 min at 190°C / 2.16 kg. Higher MI draws down to thinner coats; lower MI necks in less. Match the grade you run now first, then change one thing at a time.
Can I use blown film LDPE for extrusion coating?
Usually not. Film grades have a lower melt index, often carry slip and antiblock, and are made for a stable bubble rather than draw-down in an open curtain. Coating grades are made for low neck-in and good adhesion at high melt temperature.
Why does my LDPE coating not stick to the board?
Most often the melt is not oxidized enough: melt temperature too low, air gap too short, or line speed too high for the coat weight. Slip in the resin and an untreated substrate also hurt adhesion. Check temperature and air gap before you change the resin.
Is extrusion coating LDPE FDA compliant?
Many coating grades are made for food packaging, but compliance is grade-specific. Ask for the producer’s FDA letter for the exact grade; PE letters usually cite 21 CFR 177.1520. The finished package still has to meet the rules for its use.
Tell us the coating grade you run now
A polymer chemist reviews every request, then matches your grade or finds a qualified equivalent and prices it.
What to send for an accurate quote
- The grade name, from any supplier, or a data sheet
- Color (natural, black or a custom match)
- Fill type and percentage, if any
- Melt flow, if you know it
- Quantity for this order and what you use in a year
- Ship-to city and state or province