In plastic packaging bag manufacturing, especially for products such as polyethylene (PE), polypropylene (PP), and BOPP bags, environmental conditions play a critical role in production stability and product quality. A well-designed temperature and humidity control SOP (Standard Operating Procedure) ensures consistent printing performance, stable material behavior, and improved overall product quality.
This article introduces the key elements of a temperature and humidity control system widely used in professional packaging bag factories.
1. Purpose of Temperature and Humidity Control
The main purpose of maintaining a controlled production environment includes:
Ensuring stable physical properties of plastic materials
Improving printing accuracy and ink adhesion
Reducing static electricity during production
Preventing dust contamination and film sticking
Enhancing product consistency and yield rate
A stable environment is essential for high-quality plastic packaging production, especially in export-oriented manufacturing.
2. Scope of Application
The temperature and humidity control system is typically applied in the following areas:
Film blowing workshop
Printing workshop (gravure and flexographic printing)
Bag converting and sealing workshop
Raw material storage warehouse
Semi-finished and finished product inspection areas
Each area may require slightly different environmental settings depending on production sensitivity.
3. Standard Environmental Requirements
Temperature Control
General range: 18°C – 28°C
Printing workshop: 20°C – 25°C (stricter control required)
Allowable fluctuation: ±2°C
Humidity Control
General range: 45% – 65% RH
Printing workshop: 50% – 60% RH
Maintains anti-static conditions and stable ink performance
Proper control of temperature and humidity helps avoid common production defects such as ink smudging, poor sealing, and film deformation.
4. HVAC System Management
An effective HVAC (Heating, Ventilation, and Air Conditioning) system is essential for environmental stability:
Daily inspection of HVAC operation status
Regular monitoring of humidifiers and dehumidifiers
Monthly or quarterly calibration of sensors
Automated alarm system for abnormal conditions
Continuous data recording for quality traceability
5. Operating Procedures
5.1 Pre-Production Checks
Confirm temperature and humidity are within standard range
Ensure doors and windows are properly sealed
Check HVAC system functionality before production starts
5.2 In-Process Monitoring
Record temperature and humidity every 2–4 hours
Adjust HVAC settings immediately if deviations occur
Minimize frequent opening of workshop doors
5.3 Material Handling Control
Raw materials must be acclimatized for at least 4 hours before production
Avoid using cold materials directly to prevent condensation issues
Maintain stable storage conditions for film rolls and resins
6. Abnormal Condition Handling
When abnormal conditions occur, such as:
Temperature out of range
Excessive or insufficient humidity
Severe static electricity
Ink drying issues or adhesion problems
Follow these steps:
Report immediately to production supervisor
Adjust HVAC or environmental control systems
Pause production if necessary
Record root cause and corrective actions
7. Key Quality Control Points
Environmental control directly impacts several production quality factors:
Printing registration accuracy
Ink drying speed and consistency
Heat sealing strength
Film shrinkage and deformation
Static-related dust contamination
Stable conditions significantly improve overall production efficiency and product appearance.
8. Records and Traceability
To ensure quality traceability, factories should maintain:
Daily temperature and humidity logs
Equipment maintenance records
Abnormal event reports
Calibration records for sensors and instruments
Recommended retention period: 1–3 years depending on customer requirements or certification standards (ISO, BRC, etc.).
9. Personnel Requirements
Operators and relevant staff should:
Receive training on environmental control procedures
Understand HVAC system operation basics
Be capable of identifying and reporting abnormal conditions
Follow standardized SOP procedures strictly
10. Advanced Requirements
For food-grade or export-oriented packaging factories, additional requirements may include:
ISO 9001 and BRC compliance systems
GMP cleanroom-level environmental control
Dust control classification (e.g., Class 100K / 300K standards)
Electrostatic discharge (ESD) grounding systems
These enhancements help ensure compliance with international customer audits and strict quality standards.
Conclusion
Temperature and humidity control is a fundamental part of modern plastic packaging manufacturing. A well-implemented SOP not only improves product quality but also reduces defects, enhances production efficiency, and ensures compliance with global standards.
For packaging factories aiming to serve international markets, environmental control is no longer optional-it is a core competitiveness factor.
