Polyethylene (PE) is the most widely used plastic globally, valued for its versatility, cost-effectiveness, and adaptable properties. Its features vary by density (e.g., LDPE, HDPE, LLDPE), but core characteristics include:    Core Features:   1. Chemical Resistance      - Highly resistant to acids, bases, solvents, alcohols, and water.      - Ideal for containers holding cleaning agents, fuels, and chemicals.   2. Moisture Barrier      - Excellent water vapor barrier (low permeability), making it perfect for packaging films, bottles, and pipes.   3. Flexibility & Toughness      - LDPE/LLDPE: Highly flexible, impact-resistant (e.g., squeeze bottles, plastic bags).      - HDPE: Rigid yet tough (e.g., milk jugs, cutting boards).   4. Electrical Insulation      - Low electrical conductivity, widely used in wire/cable coatings.   5. Lightweight      - Low density (0.91–0.97 g/cm³), reducing transport costs.   6. Ease of Processing      - Easily molded via injection molding, blow molding, or extruded into films/fibers.   7. Food-Safe & Non-Toxic      - FDA/EC compliant grades available for food packaging and medical devices.   8. Recyclability      - Widely recycled (♳: HDPE, ♴: LDPE).   ---  Variants & Their Unique Traits:  Type  Density  Key Properties  Common Uses    ----------------------------------------------------------    HDPE  High (0.94–0.97 g/cm³)  Rigid, strong, weather-resistant  Pipes, fuel tanks, toys, hard hats     LDPE  Low (0.91–0.93 g/cm³)  Flexible, transparent, easy to seal  Plastic bags, cling film, squeezable bottles     LLDPE  Linear Low  Superior puncture/impact resistance  Stretch wrap, agricultural films, covers     UHMWPE  Ultra-High  Extreme abrasion resistance, low friction  Medical implants, conveyor belts, bulletproof vests    ---  Limitations:   - Low Heat Resistance: Softens at 80–120°C (varies by type).   - UV Degradation: Requires additives (e.g., carbon black) for outdoor use.   - Poor Adhesion: Surface treatments needed for printing/gluing.   - Permeable to Gases: Not ideal for carbonated drinks (often uses PET instead).     ---  Applications:   - Packaging: Bags, films, bottles, containers.   - Construction: Pipes, geomembranes, insulation.   - Consumer Goods: Toys, kitchenware, caps.   - Industrial: Chemical tanks, cutting boards, bearings.   PE’s balance of durability, processability, and recyclability ensures its dominance across industries, though selecting the 

 Key Limitations of AS Plastic: 1. Poor UV Resistance      - Turns yellow or becomes brittle when exposed to sunlight/UV rays.      - Impact: Unsuitable for transparent packaging meant for sun-exposed displays (e.g., storefronts). Requires UV stabilizers or opaque coatings.   2. Low Chemical Resistance to Solvents      - Vulnerable to strong solvents (e.g., acetone, ketones, chlorinated hydrocarbons).      - Impact: May crack or haze when filled with solvent-based cosmetics (e.g., nail polish removers, certain perfumes).   3. Moderate Barrier Properties      - Allows higher oxygen/moisture transmission than PET or PP.      - Impact: Not ideal for oxidation-sensitive formulas (e.g., vitamin C serums, organic oils) unless paired with special liners.   4. Thermal Sensitivity      - Low heat deflection temperature (∼90–100°C).      - Impact: Cannot withstand hot-fill processes or high-temperature sterilization (e.g., autoclaving). May deform in hot climates during transit.   5. Limited Impact Resistance      - More brittle than ABS, PC, or PP. Prone to cracking under sharp impacts.      - Impact: Risky for travel-friendly packaging or dense products (e.g., thick creams in large jars).   6. Scratch Vulnerability      - Softer surface than PMMA or glass. Easily scratched during handling.      - Impact: Loses clarity/gloss over time; affects premium aesthetics.   7. Not Food-Grade Compliant for All Regulations      - Some AS formulations may leach styrene monomers under extreme conditions.      - Impact: Requires strict compliance testing for lip/eye products in regulated markets (e.g., EU, FDA).    When to Avoid AS Plastic in Cosmetics: - Products requiring long-term UV exposure (e.g., sunscreen, window-displayed items).   - Formulas with high solvent content (e.g., nail polish, removers, alcohol-heavy toners >20%).   - Hot-fill processes (e.g., molten waxes, hot-pour formulations).   - Oxygen-sensitive actives (e.g., retinoids, unstable antioxidants).   - High-impact applications (e.g., thick cream jars, compacts prone to dropping).   ---    Alternatives for Demanding Applications: | Limitation          | Better Alternatives        | |---------------------|----------------------------| | UV Resistance       | PMMA (acrylic), UV-stabilized PET | | Chemical Resistance | PP, HDPE, COP/COC           | | Barrier Properties  | PET, EVOH-multilayer, Glass  | | Heat Resistance     | PP, PPSU, Glass    ...