Low Density PolyEthylene (LDPE)

LDPE film

LDPE film grade is divided into several types, including general-purpose film, high-transparency film, heavy-duty film, shrink film, and cast film. These materials possess superior physical and mechanical properties, along with high chemical stability and excellent electrical insulation. They also feature low water vapor permeability and outstanding processability, making them ideal for various applications. Films made from these resins provide exceptional clarity and strong resistance to aging, ensuring durability and long-lasting performance.

Structure

LDPE (Low-Density Polyethylene) film grade is a thermoplastic polymer made from ethylene monomers (C₂H₄) through a high-pressure polymerization process. Its molecular structure is characterized by high branching, which gives it its unique properties.

Key Structural Features:

Highly Branched Polymer:

• LDPE has short-chain and long-chain branches, preventing tight packing of polymer chains.

Amorphous & Semi-Crystalline Structure:

• Due to branching, LDPE has low crystallinity (~40–50%), making it soft and transparent.
• It is more flexible and stretchable than HDPE (High-Density Polyethylene).

Low Molecular Weight Distribution:

• LDPE has a broad molecular weight distribution, contributing to good melt strength and processability in film extrusion.

Properties

Low-Density Polyethylene (LDPE) film grade is a highly flexible and lightweight material known for its excellent elongation, impact resistance, and transparency. With a density ranging from 0.915 to 0.930 g/cm³, it offers good clarity but can appear slightly hazy. It has a relatively low melting point of around 105–115°C and remains flexible even at sub-zero temperatures, making it suitable for various applications. LDPE exhibits moderate tensile strength (8–17 MPa) and exceptional elongation at break (100–600%), ensuring durability and resilience. While it provides a good moisture barrier, its gas barrier properties are poor, allowing oxygen and CO₂ to pass through. Chemically, LDPE resists acids, bases, and alcohols but is vulnerable to hydrocarbons. Its excellent heat-sealing properties make it ideal for packaging applications, including food wrap, shrink films, and shopping bags. Additionally, it is widely used in agricultural films, protective industrial films, and medical applications such as IV bags and tubing. LDPE is typically processed through blown or cast film extrusion, operating within a temperature range of 160–220°C. However, due to its susceptibility to UV degradation, stabilizers are often added for outdoor applications. Overall, LDPE film grade is a versatile and cost-effective material, valued for its flexibility, sealability, and ease of processing.

Applications

• Packaging
  • Used for manufacturing flexible packaging films (e.g., shopping bags, wraps, and pouches).
  • Food packaging, including wraps, freezer bags, and shrink films.
  • Industrial packaging for wrapping materials, products, and protective covers.
• Agricultural Use
  • Greenhouse films for agricultural purposes, creating protective environments for plants.
  • Mulch films for soil coverage and weed control.
• Consumer Products
  • Plastic bags for grocery stores, retail packaging, and garbage bags.
  • Cling films for food preservation and covering items.
  • Disposable liners for various containers.
• Construction
  • Vapor barriers in buildings, preventing moisture from seeping into structures.
  • Covers for construction materials during storage or transportation.
• Medical Use
  • Sterile packaging for medical devices, equipment, and pharmaceuticals.
  • Medical drapes and covers.

Advantages

• Flexibility
  • LDPE film is highly flexible and can be stretched without breaking.
• Transparency
  • Offers high clarity and transparency, making it ideal for packaging.
• Chemical Resistance
  • Good resistance to chemicals, oils, and greases.
• Low Cost
  • Relatively affordable material, making it a cost-effective solution for many applications.
• Ease of Processing
  • Easy to process with methods like extrusion, injection molding, and blow molding.
• Lightweight
  • Lightweight material, reducing transportation and handling costs.
• Moisture Resistance
  • Water-resistant properties, providing good moisture protection in packaging.

Disadvantages

• Low Strength
  • Low tensile strength and can tear easily under stress or load.
• Limited Heat Resistance
  • Has a low melting point, which limits its use in high-temperature environments.
• Environmental Impact
  • Non-biodegradable and contributes to plastic pollution if not recycled properly.
• Poor UV Resistance
  • Can degrade when exposed to UV light, leading to brittleness and color fading over time.
• Low Barrier Properties
  • Not ideal for barrier applications like gas or vapor resistance compared to other materials like BOPP or PET.