The integrity of PET veterinary plastic bottles is crucial for maintaining drug efficacy and shelf life. However, bubble formation during manufacturing remains a significant challenge that compromises container integrity and potentially damages pharmaceutical products. Understanding the root causes of this phenomenon requires examining both material science and production parameters.

The Science Behind Bubble Formation

Bubble defects in PET plastic bottles originate from two primary sources:

Material Factors:

• PET's inherent hydrophilicity (0.4-0.6% moisture absorption)

• ester groups attracting water molecules

• Required dryness level: <50 ppm before processing

• Thermal degradation above 285°C releasing acetaldehyde

Processing Parameters:

• Inadequate screw design causing shear-induced degradation

• Rapid cooling creating differential crystallization rates

• Insufficient compression allowing air entrapment

Technical Analysis: Manufacturing Process Deficiencies

1. Excessive Production Speeds

Optimal vs Problematic Parameters:

Impact: Shear rates exceeding 4000 s⁻¹ cause molecular breakdown generating CO₂ and volatile organics

2. Inadequate Cooling Management

Wall Thickness Considerations:

• 1.5-2.0 mm walls require 22-25 second cooling

• 3.0 mm sections need conformal cooling channels

• 15°C temperature differential maximum between surface and core

Vacuum Bubble Formation:
Rapid surface crystallization creates shrinkage voids in thicker sections where molten core material cannot compensate during solidification

3. Pressure-Related Issues

Three Critical Pressure Parameters:

1. Injection Pressure: 800-1000 bar for complete cavity fill

2. Holding Pressure: 400-600 bar preventing back flow

3. Back Pressure: 50-100 bar ensuring proper melting

Consequence: Pressure drops below 350 bar allow air entrainment and bubble formation

Material Preparation: The Moisture Challenge

PET's hygroscopic nature demands rigorous drying:

Moisture Management Protocol:

• Drying Temperature: 150-165°C for 4-6 hours

• Air Dew Point: -40°C minimum

• Moisture Content: <0.005% (50 ppm)

• Re-drying Requirement: 4-hour exposure to ambient air

Warning: 0.02% moisture content causes hydrolytic degradation reducing IV by 0.02 dl/g

Mold Design and Venting Solutions

Advanced Mold Considerations:

• Vent Channels: 0.015-0.025 mm depth × 5-10 mm width

• Vacuum Systems: 0.5-0.8 bar extraction during injection

• Thermal Regulation: ±1°C zone control required

• Surface Finishes: Mirror polish reducing adhesion points

Twin Neck Bottle Specifics:
Complex geometries require additional venting at parting lines and ejector pin locations

Prevention and Quality Control Measures

Comprehensive Monitoring Systems:

• Infrared moisture analyzers at hopper loading

• Melt pressure sensors with ±1 bar accuracy

• Real-time viscosity monitoring through screw position

• Automated vision inspection for bubble detection

Corrective Actions:

1. Increase back pressure to 80-100 bar

2. Reduce screw speed to 45 RPM maximum

3. Implement decompression (suck back) phase

4. Extend drying time by 2 hours for humid conditions

Xingfuda's Technical Solutions

Our PET liquid bottle manufacturing incorporates:

✅ Advanced Drying Technology:

• Closed-loop dehumidifying dryers

• Real-time moisture monitoring

• Automatic material conveying systems

✅ Precision Mold Engineering:

• CFD-optimized venting designs

• Conformal cooling channels

• Automated vent maintenance systems

✅ Process Control Innovations:

• Adaptive pressure profiling

• Shear-rate monitoring algorithms

• Thermal degradation prevention systems

Quality Performance Metrics:

• 99.97% bubble-free production rate

• 0.003% moisture content consistency

• ±0.5°C temperature control accuracy

1000ml Dispensing Bottle A190