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Defects of insufficient drying of insulation strips, engineering hazards and the popularization of refined process control for prevention
Views: 0 Author: Site Editor Publish Time: 2026-07-14 Origin: Site
Numerous quality‑related failures of thermal‑break strips across the industry, including internal bubbles, end‑face porosity, cracking during assembly, long‑term deformation, thermal aging failure and unstable dimensions, stem from inadequate drying processes in over 80% of cases after root‑cause analysis. Many manufacturers only focus on visible procedures such as extrusion, shaping and cutting while ignoring drying, the hidden pre‑process. They hold the view that slight moisture content will not impair product performance. In fact, insufficient drying of PA66 thermal‑break strips brings irreversible inherent processing defects. It damages product properties from the internal structure and triggers cascading hidden troubles for door‑and‑window projects. This paper elaborates on various defects caused by poor drying, substantial harms to doors and windows, as well as full‑process refined drying control solutions, offering practical references for process improvement and loss reduction within the industry.
I. Four Typical Product Defects Caused by Inadequate Drying
Internal Bubbles and Microporous Porosity DefectsIncomplete dehumidification of raw materials makes residual moisture vaporize instantly under the high‑temperature extrusion environment above 260℃. Numerous tiny pores and voids form inside the melt. These densely‑distributed pores are highly concealed and invisible from outside. Porous structures can only be observed after sectioning, which directly reduces material compactness and structural strength.
Uneven Melt Mixing and Material Delamination DefectsMoist‑containing raw materials break the melting state of PA66 resin, lower the bonding degree between resin and glass fiber. Local glass‑fiber agglomeration, resin peeling and material delamination occur to form hidden inclusion defects. Glass‑fiber yellowing and residual impurities tend to appear after calcination, greatly reducing material purity.
Defects in Surface Appearance and Dimensional AccuracyInsufficient drying triggers fluctuating melt pressure and unstable extrusion speed. Extruded profiles suffer from rough surfaces, pockmarks, water streaks and wavy textures. Meanwhile, deviations of straightness, torsion and cross‑section thickness exceed standard limits. Poor batch‑to‑batch dimensional consistency disables precise strip assembly.
Performance Degradation and Weather‑Resistance DefectsMoisture trapped inside the material continuously induces molecular hydrolysis aging during long‑term service. The thermal‑break strips lose toughness and become brittle with drastically reduced thermal‑aging resistance. Failures such as embrittlement, pulverization and cracking emerge within a short service period.
II. Substantial Hazards to Door‑Window Projects Resulting from Drying‑Related Defects
Firstly, prominent structural‑safety risks arise. Porous interior of thermal‑break strips drastically reduces their tensile‑resistance, wind‑load resistance and deformation‑resistance capabilities. When doors and windows with large sash sizes in high‑rise buildings bear long‑term stress, partial fracture, profile deformation and loose sashes are highly likely to occur, severely undermining the structural stability of windows and doors.
Secondly, energy‑saving and sealing performance fails. Internal micropores create invisible air‑convection passages and raise the heat‑conductivity coefficient considerably. Consequently, the strips lose their capacity to break thermal bridges, making windows fail to satisfy heat‑preservation standards and pass energy‑saving inspections. Besides, dimensional deviations and uneven surfaces lead to poor fitting among profiles. Air leakage, water seepage and weakened sound insulation turn up after long‑term application.
Lastly, frequent long‑term after‑sales troubles appear. Hydrolytic aging triggered by improper drying proceeds gradually. Cracking, shrinkage, deformation and sealing breakdown emerge intensively after 3‑5 years of service. Rework and maintenance bring high costs alongside abundant project complaints, which badly damage brand reputations of door‑window manufacturers.
III. Summary of Common Non‑standard Operations for Drying Procedures in the Industry
First, drying temperature is adjusted arbitrarily. Too low a temperature results in incomplete moisture removal, while excessive temperature causes oxidative degradation of raw materials.Second, drying duration is shortened. Manufacturers cut drying time to boost output, leaving raw materials dry on the surface yet damp inside.Third, inferior equipment is adopted. Without a dehumidifying circulation system, ordinary hot‑air baking fails to eliminate deeply bound moisture.Fourth, dried raw materials are exposed to air for a long time. Re‑absorbed moisture is not eliminated through re‑processing.
Fifth, recycled and damp materials are directly put into production without extended drying time, leading to mass production of defective products.
IV. Refined Prevention and Process Optimization Solutions for Thermal Break Strip Drying Procedures
Equipment upgrade: Replace simple hot-air drying with a constant-temperature, constant-airflow, closed-loop circulating dehumidifying and drying system. Precisely control the temperature range at 90–110°C to fully evaporate deep internal moisture and stabilize the raw material moisture content at ≤ 0.1%.
Process optimization: Implement classified drying duration management for virgin materials, damp materials, and recycled materials with customized timing to avoid uniform rigid processing standards. Strictly regulate material layer thickness and layered placement to ensure uniform hot-air penetration and eliminate local dehumidification dead zones. Store dried materials in sealed and thermally insulated conditions to prevent secondary moisture absorption.
Quality inspection improvement: Establish a complete drying verification mechanism. Test the moisture content of raw materials before each production batch, and conduct sampling section inspection to check internal compactness and eliminate pore and porosity defects. Adopt calcination tests to further verify material stability, preventing unqualified dried materials from being put into production.
V. Industry Quality Improvement Value of Strict Drying Process Control
Refined control of the drying process is the key upgrade that transforms thermal break strips from functional to high-performance and durable. Making up for the shortcomings in drying technology can completely eliminate fundamental defects such as porosity, bubbles, deformation and aging. It significantly improves the batch stability, structural safety and long-term weather resistance of thermal break strips, helps door and window enterprises reduce after-sales risks, improve project quality, and drive the standardization and refinement upgrading of industry production processes.
Conclusion
Although the drying process appears to be a basic pre-production step, it serves as the core determinant of the internal quality of thermal break strips and the fundamental barrier against hidden defects. Most industry quality issues stem from hidden risks including bubbles, porosity, aging, and deformation caused by substandard drying. Standardizing drying parameters, optimizing drying procedures, and implementing rigorous drying quality inspections to secure the first production checkpoint can fundamentally improve the overall quality of PA66 thermal break strips, and ensure the safe, energy-saving, long-term and stable service of broken-bridge aluminum doors and windows.
