| HS Code | |
| Density | 0.910–0.940 g/cm³ |
| Melting Point | 105–115 °C |
| Crystallinity | 40–60% |
| Glass Transition Temperature | -125 to -100 °C |
| Tensile Strength | 8–25 MPa |
| Elongation At Break | 100–650% |
| Flexural Modulus | 200–400 MPa |
| Impact Strength | No break / high |
| Hardness | Shore D 40–50 |
| Water Absorption | <0.01% |
| Dielectric Constant | 2.25–2.35 at 1 MHz |
| Thermal Conductivity | 0.33 W/m·K |
| Chemical Resistance | Good resistance to acids, bases, alcohols; poor to hydrocarbons and oxidizing agents |
| Uv Resistance | Poor without additives |
| Recyclability | Recyclable (resin code 4) |
As an accredited Low-Density Polyethylene (LDPE) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Low-Density Polyethylene (LDPE) is packaged in 25 kg multi-wall paper bags with inner polyethylene liners, supplied on shrink-wrapped pallets. |
| Container Loading (20′ FCL) | Low-Density Polyethylene (LDPE) pellets are loaded in 25 kg bags or bulk liners into a 20′ FCL, roughly 18–20 MT. |
| Shipping | Low-density polyethylene (LDPE) is shipped as non-hazardous resin pellets in 25 kg bags, jumbo bags, octabins, or bulk trucks/railcars. It requires no special dangerous-goods placards. Keep containers dry, closed, and away from heat, sunlight, ignition sources, and strong oxidizers to prevent degradation or contamination. |
| Storage | Store LDPE in a cool, dry, well-ventilated place away from direct sunlight, heat, and ignition sources. Keep containers tightly closed and labeled. Avoid contact with strong oxidizers and organic solvents. For powders, prevent dust buildup and static discharge. Use appropriate secondary containment to prevent environmental release. Store away from incompatible materials. Maintain good housekeeping and emergency spill procedures. |
| Shelf Life | Low-Density Polyethylene (LDPE) has an indefinite shelf life when stored cool, dry, and protected from UV light, heat, and oxidizing agents. |
Melt strength, not melt index alone, controls bubble stability in LDPE-rich blown film. On high-stalk blown film lines with circular die diameters in the 250–400 mm range, bubble instability is observed as gauge variation exceeding ±5% when frost line height is reduced below 2 die diameters. Formulation for a food-contact 25–50 μm film uses 80–90 wt% LDPE with 10–20 wt% LLDPE, erucamide slip at 300–800 ppm, synthetic silica antiblock at 1000–2000 ppm, and processing aid masterbatch at 0.5–1.0 wt%. The LDPE component is selected with a melt index of 0.2–2.0 g/10 min and density of 0.918–0.924 g/cm³ under ISO 1133-1:2022 and ISO 1183-1. LDPE contributes long-chain branching, which increases strain hardening and stabilises the bubble under high blow-up ratio conditions. Addition of LLDPE above 30 wt% reduces bubble stability and may require frost line height increase by 1.5 die diameters to prevent gauge bands. Die gap is maintained at 1.2–1.6 mm, blow-up ratio is controlled at 2.0:1–3.0:1, and melt temperature is held at 160–190 °C to avoid thermal degradation of slip additives. Food-contact grades are supplied against 21 CFR 177.1520, with migration limits evaluated under EU Regulation 10/2011, and REACH SVHC clearance is confirmed at the 0.1 wt% threshold. Film tensile elongation is validated according to ASTM D882, dart impact by ASTM D1709 method A, tear propagation by ASTM D1922, and haze by ASTM D1003. Terminal products include form-fill-seal packaging film, heavy-duty shipping sacks, produce bags, tray overwrap, garment polybags, and frozen-food liners.
Coat weight uniformity in high-speed extrusion coating is determined by the interaction among melt drawdown, die internal pressure, and the air gap. The coating compound is 100 wt% LDPE with a melt index of 4.0–15.0 g/10 min and density of 0.915–0.924 g/cm³; antioxidant is added at 0.03–0.10 wt%, while slip and antiblock additives are omitted because they reduce heat-seal strength and adhesion. Barrel and adapter temperatures rise from 180 °C at the feed throat to 320 °C at the die, melt temperature is held at 280–330 °C, and die gap is set at 0.5–1.0 mm. Air gap is controlled between 150 mm and 300 mm, chill roll temperature is maintained at 10–18 °C, and line speed ranges from 80 m/min to 600 m/min. Coating weight is held at 8–40 g/m², with draw ratio between 20:1 and 100:1. Total neck-in of 25–60 mm produces trimmed edge bead, and draw resonance appears as alternating thick and thin bands at frequencies of 1–5 Hz when melt tension is insufficient. Compliance for paper-based food-contact structures requires 21 CFR 176.170 and 21 CFR 177.1520; overall migration is assessed in simulants under EU Regulation 10/2011, with the prescribed limit of 10 mg/dm². Adhesion promotion by corona discharge and ozone is applied to raise surface oxidation; published data for specific ozone dosage on individual substrate grades is limited, and adhesion must be verified by peel testing. Terminal products include coated kraft paper for coffee cups, frozen-food board, sachets, medical packaging, and aseptic liquid carton sealing layers.
Closure Moulding: Short-Shot Thresholds, Gate Vestige Control, and Linear Shrinkage
Short-shot defects in LDPE multicavity closure moulding typically originate from gate freeze-off before holding pressure can compensate for shrinkage. The formulation is 100 wt% LDPE closure grade with melt index of 2.0–4.0 g/10 min and density of 0.921–0.924 g/cm³; primary antioxidant is added at 0.05–0.10 wt%, erucamide slip at 500–1200 ppm, and colour masterbatch at 1.0–2.0 wt%. Injection moulding machines with clamp force between 180 t and 500 t run 32–96 cavity tools. Barrel temperatures are profiled from 170 °C in the feed zone to 210 °C at the nozzle, melt temperature is maintained at 180–230 °C, and mould temperature is held at 10–25 °C. Injection pressure reaches 800–1200 bar, holding time is 2–6 s, cooling time is 4–12 s, and total cycle time ranges from 8 s to 18 s. Gate diameter is limited to 0.5–0.8 mm to control gate vestige. In 48-cavity hot-runner tools, cavity-to-cavity mass variation is controlled by balancing gate diameters; unbalanced runners produce short shots in outer cavities. Shrinkage is measured at 1.5–2.2% immediately after ejection, with post-mould shrinkage of 0.2–0.5% over 24 h at ambient temperature. Articles for pharmaceutical packaging are evaluated under USP <661.1> and Ph. Eur. 3.1.3; food-contact closures are supplied against 21 CFR 177.1520 and EU Regulation 10/2011. Terminal products include snap caps, dispensing closures, tamper-evident overcaps, squeeze tube shoulders, and dropper bulbs.
When LDPE parison swell shifts beyond 60% of the die bushing diameter, extrusion blow moulding tooling must be recalibrated to hold wall thickness within ±0.15 mm. The compound uses 85–100 wt% LDPE blow moulding grade with melt index of 0.7–2.0 g/10 min and density of 0.916–0.920 g/cm³; 5–15 wt% EVA with 18% vinyl acetate is added when low-temperature drop impact is required. Colour masterbatch is added at 0.5–1.5 wt%. Extrusion blow moulding machines run continuous-extrusion or accumulator heads with die head temperature at 170–190 °C, melt temperature at 175–210 °C, blow air pressure at 0.4–0.8 MPa, and mould cooling time of 8–15 s. Parison swell is controlled between 25% and 60% by adjusting die land length; higher melt index compounds sag excessively and create wall thinning before mould closure. Pharmaceutical containers are tested against USP <661.1> and Ph. Eur. 3.1.3; food-contact grades meet 21 CFR 177.1520 and EU Regulation 10/2011. Terminal products include pharmaceutical squeeze bottles, laboratory wash bottles, ophthalmic dropper bottles, and personal care containers.
Carbon black dispersion in LDPE cable insulation is assessed on the production line by monitoring melt pressure fluctuation across a 200/400/600 mesh breaker plate. The insulation compound is formulated with 97.0–97.5 wt% LDPE, carbon black masterbatch at 2.5–3.0 wt%, and antioxidant at 0.2–0.3 wt%. Wire coating extrusion uses a crosshead die with melt temperature of 180–230 °C, conductor preheat of 100–150 °C, draw-down ratio between 3:1 and 8:1, and cooling trough water at 20–60 °C. A screen pack pressure rise above 25 MPa indicates carbon black agglomerates; the line is stopped for screen replacement before voids cause partial discharge failure. LDPE provides dielectric constant of 2.2–2.3 at 1 MHz and dissipation factor of 0.0001–0.0004 under ASTM D150. Mechanical properties after ageing are validated according to IEC 60811-100, and insulation construction is referenced to IEC 60502-1 and ASTM D1248. RoHS compliance is confirmed under Directive 2011/65/EU with lead, mercury, cadmium, and hexavalent chromium each limited to 0.1 wt% in homogeneous material. Terminal products include drop wire insulation, coaxial cable dielectric, control cable insulation, and telephone singles.
Twin-screw torque rise during masterbatch compounding of LDPE-based formulations indicates pigment agglomeration before visible colour streaks appear. The carrier formulation is composed of 50–70 wt% LDPE with melt index of 8–20 g/10 min and density of 0.918–0.922 g/cm³, pigment or additive at 20–40 wt%, dispersant wax at 2–8 wt%, and antioxidant at 0.1–0.3 wt%. Compounding is performed on a co-rotating twin-screw extruder with L/D ratio of 40–48, screw diameter of 25–75 mm, screw speed of 400–1200 min⁻¹, melt temperature of 180–220 °C, and specific energy input of 0.15–0.25 kWh/kg. Vacuum venting is maintained at -0.08 MPa to remove moisture, followed by strand pelletising after water bath cooling at 20–40 °C. Final pellet melt index is verified by ISO 1133-1:2022 at 190 °C/2.16 kg. When masterbatch is intended for food-contact final articles, the carrier and additive system must comply with 21 CFR 177.1520 and EU Regulation 10/2011; REACH SVHC clearance is required at the 0.1 wt% threshold. Terminal products include colour masterbatch for blown film, slip and antiblock masterbatch, black masterbatch for cable insulation, and additive masterbatch for injection moulded articles.
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Low-density polyethylene (LDPE) is supplied as a high-pressure free-radical homopolymer with density of 0.917 g/cm³ to 0.930 g/cm³ when tested to ISO 1183-1:2019 or ASTM D792. Film-extrusion grades are characterized by melt mass-flow rate (MFR) of 0.2 g/10 min to 2.0 g/10 min at 190°C under 2.16 kg load per ISO 1133-1:2022 or ASTM D1238, while extrusion-coating grades may exhibit MFR values from 4.0 g/10 min to 15.0 g/10 min. The material is designated PE-LD under ISO 1872-1 and classified under ASTM D4976. It contains long-chain branching that reduces high-shear viscosity and raises melt strength relative to linear low-density polyethylene. Food-contact packaging grades must comply with FDA 21 CFR 177.1520 and with overall migration limits of 10 mg/dm² in Regulation (EU) No 10/2011.
The primary structural difference is branching architecture. LDPE produced in high-pressure autoclave or tubular reactors contains both short-chain and long-chain branches, producing a broad molecular weight distribution and low crystallinity of approximately 45% to 55%. LLDPE produced by Ziegler-Natta or metallocene catalysis has limited short-chain branching and no significant long-chain branching, while HDPE has minimal branching and crystallinity of 60% to 80%. Processing consequences are measurable: LDPE has lower melt viscosity at high shear, lower equilibrium melting temperature, and higher melt strength than LLDPE. At a shear rate of 100 s⁻¹ and 190°C, film-grade LDPE may exhibit apparent viscosity in the range of 300 Pa·s to 600 Pa·s, but published data for any specific commercial grade is limited due to molecular weight and branching variations.
| Property | LDPE | LLDPE | HDPE |
|---|---|---|---|
| Density (ISO 1183-1:2019) | 0.917–0.930 g/cm³ | 0.915–0.940 g/cm³ | 0.941–0.965 g/cm³ |
| Peak melting temperature (ISO 11357-3) | 104–115 °C | 120–126 °C | 130–137 °C |
| Tensile yield stress (ISO 527-2) | 8–12 MPa | 10–25 MPa | 22–31 MPa |
| Tensile elongation at break (ISO 527-2) | 300–700% | 600–1000% | 100–1000% |
| Vicat softening temperature A50 (ISO 306) | 85–95 °C | 95–110 °C | 118–128 °C |
In blown-film production, LDPE is processed on single-screw extruders with screw diameters from 45 mm to 120 mm and L/D ratios from 24:1 to 30:1. Barrel temperature profiles are set from 150°C in the feed zone to 190°C in the metering zone, with die temperatures of 180°C to 210°C. Adapter melt temperature should remain below 240°C to suppress gel formation. Die gaps range from 0.8 mm to 1.6 mm, blow-up ratios from 2.0:1 to 3.5:1, and frost-line heights from 200 mm to 600 mm. A 90 mm extruder with a 250 mm die and internal bubble cooling typically runs at 150 kg/h to 250 kg/h; output is constrained by bubble stability rather than drive load. Unstable bubble behaviour appears as periodic gauge bands and is mitigated by raising melt temperature or reducing blow-up ratio. Sharkskin can occur when shear stress exceeds approximately 0.14 MPa; it is managed by increasing die temperature or adding a fluoropolymer processing aid.
In extrusion coating and lamination, LDPE is processed at melt temperatures of 280°C to 320°C. The upper boundary is critical: above 320°C, free-radical degradation accelerates, producing volatile aldehydes, gel specks, and viscosity loss that destabilizes the web. At 310°C to 320°C, surface oxidation improves adhesion to paperboard and aluminium foil. Air gap is maintained at 100 mm to 250 mm; longer air gap raises adhesion but increases neck-in and draw resonance. For a coating grade with MFR of 4.0 g/10 min to 8.0 g/10 min running at 250 m/min through a 1.0 mm die gap, neck-in per side is commonly 40 mm to 70 mm; exact values are grade-dependent and affected by die width and melt temperature. Draw resonance appears when draw ratio exceeds approximately 20:1, but LDPE long-chain branching suppresses it by increasing elongational viscosity under extension. Adhesion to aluminium foil is measured by peel testing at 15 mm strip width under ASTM F88; values above 2.0 N/15 mm are typical for LDPE at coating weight of 20 g/m². The processing window for adhesion without web edge instability is often narrower than ±5°C when running thin coatings below 15 g/m² on aluminium foil.
High-pressure autoclave and tubular processes operate at reactor pressures of 150 MPa to 300 MPa and initiation temperatures of 160°C to 300°C. High-pressure autoclave LDPE grades generally have broader molecular weight distribution and higher long-chain branch concentration than tubular grades. The resulting melt relaxation time is longer, improving bubble stability and reducing extrudate swell. Autoclave film resins with MFR of 0.2 g/10 min to 0.5 g/10 min are used where melt strength is controlling. Tubular reactor grades show narrower molecular weight distribution, lower haze, and fewer visible gels because of reduced micro-contamination. In cast film and extrusion coating, tubular resins with MFR of 4.0 g/10 min to 8.0 g/10 min are preferred because they require lower melt pressure and draw down more uniformly. Reported Rheotens melt strength at 190°C is 5 cN to 15 cN for LDPE film grades, compared with 1 cN to 4 cN for typical LLDPE; published data for any specific commercial resin is limited. Batch-to-batch variation in MFR should be controlled within ±0.05 g/10 min for MFR below 1.0 g/10 min to keep bubble geometry stable.
When blown film is manufactured from LDPE, tensile strength at break in the machine direction is typically 20 MPa to 30 MPa and transverse direction 15 MPa to 25 MPa under ASTM D882. Elmendorf tear strength for 50 µm film is often 2 N to 5 N in machine direction and can exceed 5 N in transverse direction due to orientation. Haze for 50 µm film is 5% to 10% by ASTM D1003, and 60° gloss is 60 to 80 gloss units by ASTM D2457. These ranges are not specification limits for any individual grade, because optical properties depend on die gap, frost-line height, and additive package. Slip and antiblock additive loadings from 500 ppm to 1500 ppm reduce blocking but can reduce seal strength. Drop dart impact for 50 µm LDPE film is typically 80 g to 150 g under ASTM D1709, whereas LLDPE film of equal gauge often exceeds 300 g; published data for specific resin pairs is limited due to orientation differences.
LDPE has dielectric constant of 2.25 to 2.35 at 1 MHz per ASTM D150 and dissipation factor below 0.0005, making it suitable for low-voltage signal and power-cable insulation. The polymer is not hygroscopic, and pre-drying is not required unless surface moisture is present after storage above 60% RH. Extrusion melt temperature for cable coating is normally 180°C to 220°C, and water-trough cooling is staged from 20°C to 60°C to avoid microvoid formation. Sulfur-containing copper stabilizers and certain hindered amine light stabilizers can cause discolouration at temperatures above 220°C; compatibility testing is required before production. Because LDPE has lower tensile strength than HDPE, jacket wall thickness must be increased for equivalent abrasion resistance under ISO 6722 or UL 62 testing.
For flexible packaging, LDPE sealant layers provide heat-seal initiation at 95°C to 110°C and seal strength of 1.5 N/15 mm to 3.0 N/15 mm at 120°C, 0.2 MPa dwell pressure, and 0.5 s dwell time under ASTM F88. Hot-tack strength and seal-through-contamination performance are lower than metallocene LLDPE sealants. LDPE is therefore selected when low-temperature sealing is not critical but extruder compatibility and low back pressure are required. In blends, additions of 10 wt% to 30 wt% LLDPE raise dart impact and puncture resistance while retaining bubble stability; additions above 30 wt% may require wider die gaps and higher motor torque due to increased shear viscosity.
The ISO 1872-1 designation system uses a block format: a designation such as PE-LD 0.923/0.3 identifies density of 0.923 g/cm³ and MFR of 0.3 g/10 min. Procurement specifications commonly include density tolerance of ±0.002 g/cm³, MFR tolerance of ±0.05 g/10 min below 1.0 g/10 min, and maximum gel count of 10 gels/m² above 0.7 mm diameter. Additive loadings are specified as 500 ppm to 1500 ppm slip/antiblock masterbatch, with migration kinetics affecting seal strength and surface energy. For food-contact use, additives must be listed in the positive lists of Regulation (EU) No 10/2011 and comply with FDA 21 CFR 177.1520.
| Standard or Regulation | Scope | Critical Limit or Test Method |
|---|---|---|
| FDA 21 CFR 177.1520 | Olefin polymers for food contact | Extractables and end-use migration limits per FDA tables |
| Regulation (EU) No 10/2011 | Plastic food-contact materials | Overall migration 10 mg/dm²; specific migration limits for additives |
| REACH Regulation (EC) No 1907/2006 | SVHC content | Communication at 0.1% w/w threshold, Article 33 |
| RoHS Directive 2011/65/EU | Electrical and electronic equipment | Lead, cadmium, mercury, Cr(VI), PBB, PBDE at 0.1% w/w or 0.01% w/w for cadmium |
| ASTM D4976 | Polyethylene plastics specification | Cell classification by density, MFR, and mechanical properties |
| ISO 1872-1 | Polyethylene designation | PE-LD designation block with density and MFR |
In injection moulding, LDPE grades with MFR of 8 g/10 min to 40 g/10 min are used for flexible lids, overcaps, and soft-touch closures. Mould temperature is kept at 15°C to 40°C, and shrinkage after moulding is 1.5% to 3.0% in the flow direction. Lower crystallinity gives a heat-deflection temperature under 0.455 MPa load of 35°C to 45°C by ISO 75-2/B. Blow-moulded LDPE containers use MFR of 0.5 g/10 min to 2.0 g/10 min and provide squeezeability but lower environmental stress-cracking resistance than HDPE; contact with detergents, alcohols, or surfactants requires case-by-case validation under ASTM D1693. In closures, torque retention after 24 h at 40°C must be verified because LDPE cold flow reduces back-off torque compared with polypropylene.
Under typical shrink-film orientation conditions, LDPE blown film can achieve machine-direction shrinkage of 30% to 50% and transverse-direction shrinkage of 10% to 20% when immersed in an oil bath at 150°C for 30 s per ISO 14616. Gauge variation should be held within ±5% to prevent uneven shrink forces. LDPE shrink film is blended with LLDPE to increase puncture resistance; however, increasing LLDPE content raises shrink initiation temperature. Agricultural film formulations use hindered amine light stabilizers at 0.2 wt% to 0.8 wt% and UV absorbers at 0.1 wt% to 0.3 wt%. Without stabilization, LDPE film can undergo chain scission and fail within 6 to 12 months of direct outdoor exposure; stabilized grades can exceed 24 months depending on thickness, climate, and stabilizer migration rate.
