Surge In Lamination Defects In Workshops During Rainy Seasons: A Stable Production Control System For Lamination Films In High-Humidity Environments

In actual printing production, climatic humidity exerts a profound impact on lamination processes, with high ambient humidity in rainy seasons serving as the primary trigger for out-of-control lamination quality. Compared with dry seasons, lamination defects in rainy seasons occur in concentrated batches, constituting a seasonal production pain point for most printing enterprises.

Five major types of prevalent lamination defects emerge during rainy periods: large-area blistering on laminated surfaces, foggy whitening and hazing of film layers, insufficient paper-film adhesion leading to delamination and glue separation, overall curling and edge warping of finished products, and edge cracking and lifting after die-cutting. Such defects not only ruin the flatness and gloss of finished products but also drastically degrade the wear resistance, moisture resistance, tear resistance and other functional properties of packaging goods, failing to meet customers’ quality acceptance standards.

Defect outbreaks trigger cascading losses. Mass rejects directly waste consumables including paper, offset printing ink and lamination films. Rework requires massive labor and material input, extends production cycles, and easily results in delayed order delivery. Meanwhile, substandard finished products entering the market will trigger customer complaints, returns and even compensation claims, damage corporate cooperative reputation, and directly cut production profits.

The industry generally suffers from extensive operation misconceptions. When encountering lamination defects in rainy seasons, operators usually simply raise temperature or speed up production speed as emergency solutions, which only temporarily alleviate superficial issues rather than eliminating deep-seated hidden risks caused by dampness. This leads to recurring malfunctions and a vicious cycle of repeated rework that addresses symptoms instead of root causes.

To resolve rainy-season lamination defects, empirical parameter adjustments must be abandoned. Instead, failure logic must be clarified across four dimensions—paper, film materials, offset printing ink and workshop environment—to enable targeted prevention and source governance.

Paper moisture absorption and deformation: the fundamental inducing factorPaper features a porous fibrous structure with strong moisture absorption and desorption properties, making it highly sensitive to humidity fluctuations. In rainy seasons with excessive air humidity, openly stored paper rapidly absorbs water vapor, resulting in excessive moisture content. Water absorption swells and loosens paper fibers, undermining structural stability. After lamination, inconsistent moisture levels between paper and film create mismatched deformation and film tension during hot pressing and cooling, ultimately causing blistering, curling, delamination and other issues.

Moisture-induced failure of hot-melt adhesive layers on lamination films: the core cause of adhesion defectsLamination films rely on surface hot-melt adhesive layers to bond paper and plastic, yet these adhesive layers readily absorb water vapor from the air. Once lamination films are unpacked and exposed during rainy seasons, their adhesive layers quickly absorb moisture and soften, drastically diminishing activation performance and adhesion strength. The adhesive can no longer form high-strength bonds with paper surfaces and ink layers, leading to weak adhesion, partial debonding and large-area delamination quality defects.

Abnormal drying of offset printing ink exacerbates defectsIn high-humidity environments with poor air circulation and high water vapor content, solvent and moisture volatilization rates of offset printing ink slow significantly, leaving latent water vapor and uncured ink layers on paper surfaces. If lamination proceeds under such conditions, water vapor and air become trapped between paper and film, accumulating continuously to form white spots, bubbles and foggy hazing defects that severely compromise finished product appearance.

Inadequate workshop environmental control: a major contributor to frequent defectsMost small and medium-sized printing workshops lack standardized temperature and humidity control equipment. During rainy seasons, drastic day-night temperature shifts and violent humidity fluctuations fail to discharge humid air in a timely manner. Raw materials continuously absorb moisture, while dew condenses on hot rollers and guide rollers of lamination equipment. Direct contact between water vapor and paper/film materials completely destabilizes paper-plastic composite bonding and induces a full spectrum of lamination issues.

To address rainy-season high-humidity production pain points, enterprises must abandon extensive production modes and establish a closed-loop five-in-one control system covering environment, raw materials, processes, equipment and finished products. Centered on upfront prevention and standardized operations, this system eliminates lamination defects from the source and guarantees stable production.

1. Environmental Control: Establish Standardized Constant-Temperature & Constant-Humidity Production Zones

A stable workshop environment forms the foundation of stable lamination production in rainy seasons. Workshops must strictly maintain production parameters: temperature between 18°C and 26°C, and relative humidity within the optimal range of 40% to 60%. High-power dehumidifiers and fresh air systems must operate around the clock, with temperature and humidity tested and recorded at fixed intervals. Dehumidifier power is adjusted according to humidity variations to rapidly expel humid air. Windows must remain closed during production to block external moisture infiltration. After daily shutdowns, all workshop doors, windows and ventilation openings are sealed to maintain a dry, airtight environment, preventing equipment and raw materials from reabsorbing moisture overnight and laying a solid foundation for next-day production.

2. Raw Material Control: Implement Pre-Processing for Paper and Lamination Films to Prevent Moisture Damage

Moisture-proof management of raw materials constitutes the first line of defense against lamination defects. After warehousing, paper must be hermetically stored in dry warehouses and never left uncovered. Twenty-four hours prior to production, paper is transferred to the lamination workshop to balance moisture content under constant temperature and adapt to production conditions. Slightly damp and soft paper must undergo pre-drying on machines until moisture standards are met before lamination. Lamination films follow the principle of unpacking small quantities on demand and remain sealed during storage to avoid moisture-induced deactivation of adhesive layers. During rainy seasons, priority should be given to special lamination films with superior moisture resistance and adhesion, suited for humid working conditions to improve paper-plastic bonding stability.

3. Process Control: Dynamically Calibrate Production Parameters for High-Humidity Conditions

Enterprises must avoid applying identical process parameters year-round and dynamically optimize adjustments for rainy-season operating conditions. The composite temperature is raised by 5–10°C compared with dry seasons to fully activate dampened hot-melt adhesive, compensate for viscosity loss caused by water vapor, and ensure uniform melting and bonding of adhesive layers. Lamination speed is moderately reduced to extend hot pressing and bonding time, completely expelling residual air and water vapor between paper and film to eliminate trapped-air blistering and weak adhesion. Hot roller pressure is slightly increased to guarantee uniform full-width pressure and comprehensive tight bonding. Meanwhile, ink drying time is extended; lamination can only proceed after confirming full curing of offset printing ink and absence of latent water vapor on paper surfaces, avoiding defects at the process source.

4. Equipment Operation & Maintenance: Execute Special Moisture-Proof Maintenance Standards for Rainy Seasons

Equipment status directly determines lamination quality, requiring dedicated moisture-proof maintenance during rainy seasons. Before daily startup, core components including hot pressing rollers and guide rollers are thoroughly cleaned to remove surface dew, water vapor and dust, preventing foreign matter from impairing bonding results. After startup, machines run idle for 3 to 5 minutes to adjust unwinding and winding tension, ensuring stable film feeding and preventing stretching, deviation, wrinkling and deformation of moisture-affected films. Heating systems are inspected regularly to guarantee uniform hot roller temperatures and eliminate insufficient local heat that leads to incomplete adhesive melting and poor bonding. At the end of each production day, equipment is cleaned, leftover raw materials are sealed for storage, and full dust and moisture protection is applied to all machinery.

5. Finished Product Control: Standardize Post-Lamination Curing, Shaping and Protection Procedures

Lamination completion does not equate to quality stabilization; inadequate protection of finished products in rainy seasons easily triggers secondary defects. Laminated finished products must not be immediately die-cut, stacked or packaged. They require 2 to 4 hours of standing in constant-temperature, constant-humidity workshops to release internal stress and balance moisture levels, stabilizing bonding conditions and preventing later curling, edge warping and delamination. Separating paper is laid between stacked finished products to avoid deformation and adhesion under heavy pressure. After stacking, all finished goods are hermetically wrapped with moisture-proof film to isolate external water vapor. Dedicated personnel conduct full-process sampling inspections to screen for bubbles, white spots, poor adhesion and other flaws in advance, preventing mass defective products from flowing out and cutting rework losses.

Lamination defects of lamination films in rainy seasons are not isolated equipment or process issues, but comprehensive production problems stemming from imbalances across environment, raw materials, processes, equipment and quality control. Conventional temporary parameter adjustments and emergency remediation within the industry only resolve superficial issues and fail to deliver long-term stable production. The core of improving quality and reducing losses for rainy-season lamination lies in upfront prevention and full-process closed-loop control. Printing enterprises must abandon traditional extensive production mindsets, establish seasonal dynamic production standards, and integrate moisture-proof control throughout the entire workflow: raw material warehousing, production processing and finished product storage. Refined, standardized control effectively lowers reject rates and production costs for rainy-season lamination, mitigates risks of delayed order delivery, and comprehensively safeguards production quality and delivery efficiency.

Amid escalating quality competition in the packaging and printing industry, customers impose continuously higher standards on finished product stability, appearance and durability. Seasonal refined working condition management has become a core competitive advantage for post-press procedures. Regular implementation of the full-process control system for rainy-season lamination films enables enterprises to efficiently tackle high-humidity production challenges, reduce costs, boost efficiency and tightly control quality hazards. Furthermore, it drives the transformation of post-press lamination from experience-based production to standardized, refined and normalized operation, supporting steady overall quality improvement across the printing industry.