LDPE · grade
LDPE-INJ
Properties of the INJ condition, compared with the other LDPE grades.
High-MFR, lower-molecular-weight resin for thin-wall soft mouldings such as closures, liner caps and squeeze parts.
What is LDPE-INJ?
LDPE-INJ is LDPE in the INJ grade — high-MFR, lower-molecular-weight resin for thin-wall soft mouldings such as closures, liner caps and squeeze parts. LDPE-INJ has a yield strength of 10 MPa (1.38 ksi) and a tensile strength of 10 MPa (1.45 ksi) — weaker than 97% of polymer grades. Elongation at break is 200% and the elastic modulus is 0.2 GPa (0.029 Msi). LDPE-INJ has a density of 0.92 g/cm³ (0.0333 lb/in³), lighter than 79% of polymer grades. Its glass-transition temperature is -110°C (-166 °F). Unfilled is the default condition FabDigit quotes; INJ is available on request or by drawing note.
Advantages
- Readily welded — 95/100, better than 99% of polymer grades
- Low moisture uptake — 0.01%, better than 97% of polymer grades
- Low embodied carbon — 2.1 kg CO₂/kg, better than 94% of polymer grades
- Forms and bends easily — 90/100, better than 92% of polymer grades
- Conducts heat well — 0.33 W/m·K (0.191 BTU/hr·ft·°F), better than 88% of polymer grades
Limitations
- Low strength — 10 MPa (1.38 ksi), worse than 97% of polymer grades
- Degrades in UV without stabilisers — 20/100, worse than 88% of polymer grades
- High mold shrinkage — 2.2%, worse than 88% of polymer grades
- Hard to polish — 30/100, worse than 80% of polymer grades
- Limited service temperature — 70°C (158 °F), worse than 78% of polymer grades
LDPE-INJ properties
Typical room-temperature values for LDPE-INJ — 9 properties are specific to this condition; the rest are grade-level values shared by every LDPE grade. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher.
Physical7
LDPE-INJ has a density of 0.92 g/cm³ (0.0333 lb/in³), lighter than 79% of polymer grades. Its glass-transition temperature is -110°C (-166 °F).
Mechanical17
LDPE-INJ has a yield strength of 10 MPa (1.38 ksi) and a tensile strength of 10 MPa (1.45 ksi) — weaker than 97% of polymer grades. Elongation at break is 200% and the elastic modulus is 0.2 GPa (0.029 Msi).
Thermal11
LDPE-INJ is rated for continuous service to 70°C (158 °F). It conducts heat at 0.33 W/m·K (0.191 BTU/hr·ft·°F), better than 88% of polymer grades. Thermal expansion is 190 µm/m·K (105.6 µin/in·°F).
Electrical7
LDPE-INJ is an electrical insulator with a dielectric strength of 25 kV/mm (635 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), better than 73% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of LDPE-INJ takes about 80 MJ of energy and emits 2.1 kg of CO₂ — less than 85% of polymer grades. Typical recycled content is 10%.
Manufacturability8
LDPE-INJ's machinability is fair (45/100, worse than 77% of polymer grades); weldability excellent (95/100); formability excellent (90/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other LDPE grades and fills
LDPE is also supplied in 10 other conditions. The full side-by-side table is on the LDPE overview.
- UnfilledDefaultBaseline natural resin; pick when flexibility, sealability and chemical inertness matter more than stiffness or heat resistance.10 MPa yield · 47 Shore D
- XLPECross-linked network for LV/MV cable insulation and heat-shrink; raises continuous rating to ~90 °C and kills stress cracking, but the cured part cannot be remelted.17 MPa tensile
- FRUse where UL 94 V-0/V-2 or low-smoke halogen-free cable compounds are required; heavy filler loading cuts elongation sharply.10 MPa tensile
- INJHigh-MFR, lower-molecular-weight resin for thin-wall soft mouldings such as closures, liner caps and squeeze parts.10 MPa yield · 46 Shore D
- FOAMChemically or physically blown closed-cell foam for protective packaging, gaskets and thermal insulation.0.35 MPa tensile
Working with LDPE-INJ
Is LDPE easy to machine?
Cuts easily but is gummy and springs back — use very sharp positive-rake single-flute tools, high speed, low feed pressure, air blast, and expect poor tolerance hold (>0.2 mm) plus large thermal expansion.
Can LDPE be welded?
Excellent thermoplastic weldability: heat sealing, impulse, hot-plate, hot-gas and extrusion welding with LDPE/LLDPE rod; adhesive bonding needs corona, flame or plasma surface treatment.
Can LDPE be formed, bent or molded?
Very easy flow at 160–230 °C melt, 20–50 °C mould, low injection pressure; allow 1.5–4% shrinkage with strong direction dependence and design generous draft and thick-to-thin gating to avoid voids and sink.
What surface finishes work on LDPE?
Cannot be plated or painted without pre-treatment; use corona/flame treatment (≥38 dyn/cm) before printing, or in-mould colour, laser marking and hot stamping instead.
LDPE chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| antioxidant / process stabilizer (hinder | 0.02 – 0.3 | 0.1 |
| slip & antiblock (erucamide, silica) — fOmitted in injection and food-critical grades | 0 – 1 | 0.3 |
| ethylene (branched homopolymer, C2H4 repHigh-pressure free-radical polymer; 20–40 short-chain branches + long-chain branching per 1000 C; crystallinity 40–55% | ≥ 98 (balance) | — |
LDPE-INJ — frequently asked
What is LDPE-INJ used for?
LDPE-INJ is typically used for squeeze bottles, flexible tubing and hose, packaging film and drum liners, bottle cap liners and gaskets, wire and cable insulation and extrusion coating on paperboard. In short: flexible; low cost.
What is the yield strength of LDPE-INJ?
LDPE-INJ has a typical yield strength of 10 MPa (1.38 ksi) and a tensile strength of 10 MPa (1.45 ksi) — weaker than 97% of polymer grades. Strength varies by condition: see the 11 listed tempers.
Is LDPE-INJ easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 77% of polymer grades). Cuts easily but is gummy and springs back — use very sharp positive-rake single-flute tools, high speed, low feed pressure, air blast, and expect poor tolerance hold (>0.2 mm) plus large thermal expansion.
Can LDPE-INJ be welded?
Yes — weldability is rated excellent (95/100). Excellent thermoplastic weldability: heat sealing, impulse, hot-plate, hot-gas and extrusion welding with LDPE/LLDPE rod; adhesive bonding needs corona, flame or plasma surface treatment.
What surface finishes work on LDPE-INJ?
Cannot be plated or painted without pre-treatment; use corona/flame treatment (≥38 dyn/cm) before printing, or in-mould colour, laser marking and hot stamping instead.
Can LDPE-INJ be formed, bent or molded?
Very easy flow at 160–230 °C melt, 20–50 °C mould, low injection pressure; allow 1.5–4% shrinkage with strong direction dependence and design generous draft and thick-to-thin gating to avoid voids and sink.
What is the maximum service temperature of LDPE-INJ?
LDPE-INJ is rated for continuous use to about 70°C (158 °F), and briefly to 90°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between LDPE Unfilled and LDPE-INJ?
Unfilled is the default condition — baseline natural resin; pick when flexibility, sealability and chemical inertness matter more than stiffness or heat resistance. INJ: high-MFR, lower-molecular-weight resin for thin-wall soft mouldings such as closures, liner caps and squeeze parts. Yield strength is 10 MPa in Unfilled versus 10 MPa in INJ.
Can FabDigit make parts in LDPE-INJ?
Yes — LDPE-INJ is available for sheet metal and injection molding with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM D4976 — Standard Specification for Polyethylene Plastics Molding and Extrusion Materials — ASTM International (2020)
- ISO 1872-1/-2 — Plastics: Polyethylene (PE) moulding and extrusion materials — ISO (2015)
- Engineered Materials Handbook Vol. 2: Engineering Plastics — ASM International (1988)
- CAMPUS / UL Prospector polyethylene datasets — CWFG / UL Solutions (2024)
- LDPE film and injection grade datasheets — Dow / ExxonMobil / SABIC / (2024)
- Eco-profile: Low Density Polyethylene (LDPE) — PlasticsEurope (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.