What is the structure of the spray bottle nozzle and how to choose the materials?
The performance of continuous spray bottle nozzles (such as continuous spray and cosmetic spray nozzles) depends on their precise internal structure and reasonable material matching. Below, from the three dimensions of structural disassembly + material selection + the reason for choosing PP (polypropylene), we will clearly explain why the spray nozzles are designed this way and why the industry generally selects PP as the main material.
I. Internal and External Structures of the Spray Bottle Nozzle
The spray head can be divided into two parts: the internal functional structure and the external operating structure. Together, they achieve the entire process of pressing, liquid suction, pressure increase, and atomized spraying.
1. External structure (visible to users)
The spray head needs to have a lifespan of 2000 to 5000 presses or more. It mainly performs the functions of "operation and protection", including:
① The trigger/pressing is the core component for user operation, mostly made of PP or ABS. It requires moderate hardness, not prone to breaking or deforming, stable rebound, and resistance to fatigue. It should not break easily upon impact. (PE: prone to expansion and deformation when exposed to solvents, PET: has average chemical resistance and cannot be used as elastic components)
② The shell/cover covers the internal mechanism and provides the overall appearance, mostly made of PP (lightweight, resistant to chemicals), cost, process compatibility, and the usage scenarios of daily care sprays are highly matched or ABS (higher hardness)
③ Nozzle cap / Atomizing port: Determines the spray form (fine mist, straight spray). The atomizing core can be made of PP, PE or ceramic.
2. Internal functional structure (core of the spray head)
The key to the continuous spray head lies in the pump core + pressure retention system, which is mainly composed of the following components:
① Pump body assembly
Pump chamber, suction tube (Dip tube) for holding liquids/gases and connecting the tubes inside the bottle. Generally, PP material is used. PP is a non-polar polymer and does not react with common substances such as alcohol, fragrance, surfactants, acids and bases (pH 3-10). Some contain propylene glycol as a solvent. It will not release harmful substances to contaminate the product nor will it be eroded by the ingredients causing cracking or swelling (compared to ABS which is easily corroded by alcohol, PE which has weak solvent resistance, and PP has almost no weaknesses in compatibility);
One-way valve/ball: Prevents liquid backflow. Common materials: PP, POM, rubber ball.
② Pressure retention structure (key to continuous spraying)
Pressure retention spring (POM engineering plastic spring: used for acidic and alkaline products or 304, 316 stainless steel springs with high strength and corrosion resistance)
Pressure retention sealing seat (PP/rubber)
Boosting channel: Increases the pressure of the chamber, forming fine mist
Principle: Press once, the spring stores energy, and continuous and uniform mist is discharged
③ Drive and reset system
Piston: Compares the pump chamber
Reset spring: Draws back the liquid, preparing for the next press
Material: POM, PP, stainless steel spring
④ Atomizing nozzle assembly
Microporous atomizing port (0.1–0.3mm)
Atomizing disc/atomizing core: Can be made of PP (cost-effective) or ceramic (high-end nozzle),The dozens to several tens of components inside the nozzle are completed through precise injection molding and assembly, relying on the fatigue resistance, corrosion resistance and stability of the material.
II. Why is PP material commonly used for spray bottle nozzles?
Industry conclusion: PP is the best all-round material for spray nozzles, without any competition.
→ PP is the only low-cost material that can be compatible with various cosmetic liquids.
1.Advantages of PP: Excellent fatigue resistance, Not prone to breaking, with good toughness. It won't shatter upon dropping and has a stable rebound feel. It is highly suitable for: pressing keys, pump body shells, piston seats, and connection structures.
2. Excellent injection molding performance: Compatible with complex nozzle structures
The internal structure of the spray head is complex and detailed. PP has the following advantages: good fluidity, high processing accuracy
It can easily form micro-holes, snap-in parts, and small structures, with a short molding cycle, high production efficiency, controllable shrinkage rate, and high yield
→ It is highly suitable for large-scale mass production, with thousands of mold cycles per day in industrialized production.
3. Safe and non-toxic, meeting food-grade requirements
PP is the PP5 recycled material marking. Its advantages include: no bisphenol A (BPA-free), no plasticizers, no odor, and suitable for food-grade packaging (in compliance with FDA/GB 4806).
Suitable for nozzles for: cosmetics, oil bottles
Maternity and infant care / oral sprays
4. Recyclable and environmentally friendly
Complies with the brand's ESG requirements: PP is a 100% recyclable plastic with a higher recycling value than PE and PS. It can be promoted as a sustainable packaging feature.
5. Optimal Cost Solution
Compared with similar materials: 20-40% cheaper than ABS and POM, lower in processing energy consumption than PET, much lower than PC and PMMA, and extremely important for products with high usage such as spray bottles.
Summary: Why are spray nozzles mostly made of PP?
✔ Compatible with cosmetic formulations (almost all spray liquids will not corrode PP)
✔ Resistant to fatigue and impact, capable of withstanding thousands of presses
✔ High processing accuracy, capable of producing precise pump cores and structural components
✔ Safe and non-toxic, food-grade, suitable for infant products
✔ Lightweight + low cost, suitable for large-scale production
✔ Recyclable, in line with environmental protection trends
→ Therefore, the industry consensus is: the main material for the body of continuous spray bottle spray heads should be PP.