The selection of dropper bottle materials must strictly consider content compatibility, light resistance, sealing performance, chemical inertness, safety regulations (e.g., FDA, EU, CSP), and texture requirements.

1. Bottle Body:

   • Glass: The absolute mainstream, especially in high-quality products.

     • Soda-lime glass: Lower cost, meets basic requirements. Good transparency.

     • Borosilicate glass (e.g., Schott, Corning brands): Preferred material.

       • Advantages: Excellent chemical inertness (almost no reaction with any ingredient), low coefficient of thermal expansion (resistant to thermal shock, suitable for processes like lyophilized powder), relatively high mechanical strength, high transparency, excellent gas barrier (good preservation), recyclable.

       • Disadvantages: Higher cost than soda-lime glass, heavy weight, fragile.

       • Colors: Commonly transparent, amber (UV protection), cobalt blue (UV protection, more high-end).

   • Plastic: Primarily used for mid-to-low-end or specific lightweight requirements. Compatibility must be strictly evaluated.

     • PET (Polyethylene Terephthalate):

       • Advantages: High transparency, high hardness, relatively lower cost than glass, lightweight, shatter-resistant.

       • Disadvantages: Moderate gas barrier (potential permeability of oxygen and water vapor), poor compatibility with certain essential oils/solvents/high-concentration active ingredients (possible migration or adsorption), slight deformation possible with long-term use. Often includes UV absorbers.

     • PETG (PET Copolyester):

       • Advantages: Better toughness than PET, more impact-resistant, slightly better chemical resistance, easy to thermoform or bond.

       • Disadvantages: Higher cost than PET, gas barrier still inferior to glass.

     • PP (Polypropylene):

       • Advantages: Low cost, good chemical resistance, high-temperature resistance (can be steam sterilized), lightweight, shatter-resistant.

       • Disadvantages: Moderate transparency (semi-transparent), poor gas barrier, texture inferior to glass/PET. Often used for caps or dropper inner tubes.

     • HDPE (High-Density Polyethylene): Similar to PP, more opaque, less commonly used for the main bottle body.

2. Dropper Tip / Bulb / Pipette: The core functional component, directly affecting liquid dispensing accuracy and user experience.

   • Bulb: The elastic component that creates negative pressure to draw liquid.

     • Butyl Rubber (IIR): Mainstream high-end choice.

       • Advantages: Low gas permeability (excellent airtightness, preventing liquid evaporation and external gas entry), good chemical resistance (especially to solvents and oils), good resilience, not prone to aging or becoming sticky, can withstand multiple high-temperature sterilizations (e.g., 121°C), complies with pharmaceutical-grade standards.

       • Disadvantages: Highest cost.

     • Natural Rubber (NR):

       • Advantages: Good elasticity, low cost.

       • Disadvantages: Highly prone to aging and becoming sticky, high gas permeability (leading to liquid evaporation and oxidation), may introduce protein allergens, poor chemical resistance (especially to oils and solvents), possible odor migration. Not recommended for cosmetics, especially products high in oils or active ingredients.

     • Silicone Rubber:

       • Advantages: Wide temperature resistance range, good chemical inertness, non-toxic and odorless, good resilience, easy to clean.

       • Disadvantages: Higher gas permeability than butyl rubber, high cost, potential slight compatibility issues (swelling) with products containing extremely high silicone oil. Commonly used in food and pharmaceuticals; gradually increasing use in cosmetics (permeability needs evaluation).

     • Thermoplastic Elastomer (TPE):

       • Advantages: Can be injection molded (design flexibility, can be integrated with the dropper), controllable cost, variety of colors.

       • Disadvantages: Long-term resilience and sealing durability may be inferior to rubber, gas permeability requires specific evaluation, chemical resistance requires formula testing. Growing in application.

   • Pipette / Stem: The tubular part connecting the bulb to the liquid inside the bottle.

     • Glass Tubing:

       • Advantages: Best chemical inertness, high transparency, easy to clean, good texture.

       • Disadvantages: Fragile, high cost, processing (cutting, fire polishing) requires precision.

     • PP (Polypropylene): Most common.

       • Advantages: Low cost, shatter-resistant, good flexibility (not easily broken), good chemical resistance.

       • Disadvantages: Moderate transparency, may degrade with long-term contact with certain strong solvents.

     • PET / PETG:

       • Advantages: High transparency, better strength and toughness than PP.

       • Disadvantages: Higher cost than PP, slightly less flexible. Chosen when high transparency is desired.

     • LDPE (Low-Density Polyethylene): Good flexibility, but lower hardness and transparency; less commonly used for pipettes.

3. Cap / Overcap: Protects the dropper tip, provides sealing, and serves for brand display.

   • PP (Polypropylene): Most mainstream.

     • Advantages: Low cost, high hardness, good dimensional stability, easy to process (injection molding), easy to dye.

   • ABS (Acrylonitrile Butadiene Styrene):

     • Advantages: High hardness, good gloss, easy to plate/spray for metallic effects.

     • Disadvantages: Slightly higher cost, moderate weather resistance. Used to enhance appearance.

   • Metal (Aluminum, Zinc Alloy):

     • Advantages: High-end texture, substantial feel.

     • Disadvantages: High cost, increased weight. Often used in high-end products; surfaces can be anodized or plated.

   • Liner / Seal: Usually placed inside the cap, pressed against the bottle opening to form a seal. Materials often include foamed PE, silicone gaskets, or coated cardboard.

4. Bottle Neck / Finish: The critical sealing surface that mates with the cap. Glass bottles require precise molding to ensure dimensional accuracy and smoothness.

Dropper Bottle Manufacturing Process

1. Glass Bottle Body Manufacturing:

• Molding (Pressing or Blowing): Molten glass is injected into molds to form the bottle shape.

• Fire Polishing: Removes burrs from the bottle mouth, improving smoothness and sealing performance.

• Annealing: The glass is heated and then slowly cooled to eliminate internal stresses and prevent spontaneous breakage.

• Spraying/Coating (Optional): Such as body coating, sandblasting the bottle bottom, or inner wall coating (to enhance barrier properties or prevent sticking).

• Screen Printing/Hot Stamping (Optional): Decoration of the bottle body.

2. Plastic Bottle Body Manufacturing (PET/PETG):

• Injection Stretch Blow Molding: First, a preform is injection molded, then heated, stretched, and blow-molded into the final bottle. This ensures high transparency and strength.

3. Dropper Manufacturing:

• Glass Dropper:

  • Glass tube cutting.

  • Fire polishing of the tube mouth (to smooth edges and prevent damage to the bulb).

  • Melting and drawing the tube tip to form a fine point (controlling the droplet orifice size).

• Plastic Dropper (PP/PETG): Precision injection molding. Requires control over tube diameter uniformity and tip dimensional accuracy.

• Bulb (Butyl/Silicone/TPE):

  • Compression Molding & Vulcanization (Butyl/Silicone): Raw rubber compound is placed into a mold and formed under heat and pressure (vulcanization). This is the mainstream process.

  • Injection Molding (TPE): Pellets are heated, melted, and injected into a mold for forming. High efficiency.

4. Cap Manufacturing:

• Injection Molding: For PP, ABS, etc.

• Metal Cap Manufacturing: Stamping, drawing, turning, anodizing/electroplating/spraying.

5. Assembly Process:

• Bulb and Dropper Assembly:

  • Glass Dropper: Special adhesive is applied inside the bulb's hole. The glass tube is inserted and pressed tightly until cured. This is a critical sealing point.

  • Plastic Dropper: May involve heat pressing, ultrasonic welding, or interference fit (for integrated or TPE heads).

• Cap Assembly: The liner (gasket) is inserted into the cap.

• Final Product Assembly (Typically completed by the brand owner):

  • The dropper head is inserted into the bottle mouth.

  • The outer cap is screwed on tightly (pressing the liner against the bottle mouth to form the seal).

Note: For high-demand products (e.g., sterile pharmaceuticals), filling and capping are performed in a sterile environment.