During processing, transportation, and storage, stainless steel deep-drawn utensils are prone to surface damage such as scratches, stains, and oxidation, affecting product appearance and quality. Therefore, the protective film used for its surface protection must meet core requirements including compatibility with the deep-drawing process, stable adhesion, strong protection, and easy peeling without residue. Specifically, these requirements can be categorized into three main types: process compatibility, protective performance, and ease of use. The following details the requirements for CPE (chlorinated polyethylene) protective film, strictly adhering to given parameter standards.
I. Core Requirements for Protective Films for Stainless Steel Deep-Drawn Utensils
Stainless steel deep-drawing is a complex plastic processing technique. During the forming process, the sheet metal undergoes severe stretching and bending deformation. The protective film must maintain long-term adhesion, be easy to peel off later, and not damage the utensil surface. Therefore, the protective film must meet the following key requirements:
Excellent ductility and tensile strength: During deep-drawing, the protective film must stretch and deform synchronously with the stainless steel sheet without breaking or tearing, otherwise it will lose its protective function. It must also possess sufficient tensile strength to withstand the stress impact during stretching and prevent film damage.
Suitable Thickness and Hardness: The thickness needs to balance protection and adhesion. Too thin and it's easily scratched or damaged; too thick and it affects deep-drawing precision and increases peeling difficulty. The hardness needs to be moderate, resisting minor friction and impacts without compromising adhesion.
Suitable Adhesion: The adhesion needs to be controlled within a reasonable range. It must ensure it doesn't detach or lift during deep drawing, adhering tightly to the sheet surface, while also allowing for easy peeling later without leaving adhesive residue or damaging the stainless steel surface's luster.
Good Adhesion and Stability: The protective film must adhere tightly to the stainless steel surface, without bubbles or wrinkles. It must remain stable under the high temperature and pressure of deep drawing, without softening or decomposing, and possess a certain degree of anti-fouling ability to prevent dust and oil adhesion.
Appropriate Appearance and Identification: The color should facilitate observation of the adhesion during production, avoiding problems such as missed areas or uneven application, while not hindering the inspection of the stainless steel sheet's surface quality.
II. Specific Parameters and Adaptation Instructions for CPE Protective Film (Example)
CPE protective film, with its excellent flexibility, ductility, and environmental friendliness, is a commonly used material for surface protection of stainless steel deep-drawn utensils. Based on practical application needs, its specific parameters must meet the following standards (meeting user-specified requirements), and each parameter must be adapted to the characteristics of the deep-drawing process. Specific instructions are as follows:
1. Thickness: 80 micrometers
A thickness of 80 micrometers is one of the optimal thicknesses for stainless steel deep-drawn utensils. It provides sufficient protection, effectively resisting friction and minor impacts between the mold and the sheet during deep drawing, preventing scratches and indentations on the stainless steel surface; it also avoids affecting the deep-drawing forming accuracy due to excessive thickness, while ensuring good adhesion, closely following the stretching and deformation of the sheet without wrinkling or peeling. This meets the core requirements of the deep-drawing process for protective film thickness and conforms to the conventional thickness application range of CPE protective film in the metal deep-drawing field.
2. Color: Dark Blue or Light Blue
Choosing dark blue or light blue is primarily for balancing visibility and practicality. On the one hand, the blue color clearly distinguishes the protective film from the stainless steel sheet surface, making it easier for production workers to check the application and promptly identify problems such as missed areas, uneven application, and air bubbles, thus preventing protective failure due to improper application. On the other hand, the blue film does not obscure the texture of the stainless steel sheet surface (such as brushed texture), facilitating the inspection of surface defects. Simultaneously, the blue color has a certain degree of light-blocking property, reducing the impact of ultraviolet radiation on the film's adhesion and lowering the risk of residual adhesive. This aligns perfectly with the requirements for the visual distinctiveness of the protective film in deep-drawing processes.
3. Elongation: MD direction greater than 320%, TD direction greater than 400% Elongation is a core requirement for protective films in deep-drawing processes. The CPE protective film must meet the following elongation requirements: MD (longitudinal) greater than 320% and TD (transverse) greater than 400%. This parameter perfectly matches the stretching requirements of deep-drawing stainless steel sheets. During deep drawing, stainless steel sheets undergo intense stretching in all directions, especially in the transverse (TD) direction. A transverse elongation of over 400% ensures the protective film stretches synchronously with the sheet material, preventing breakage or tearing and avoiding scratches and abrasions to the stainless steel surface caused by mold damage. A longitudinal (MD) elongation of over 320% accommodates the longitudinal stretching requirements of the sheet material, ensuring overall fit. This is one of the core advantages of CPE protective film as a deep drawing-specific film.
4. Tensile Strength: MD direction ≥11MPa, TD direction ≥10MPa. Tensile strength and elongation complement each other, ensuring the protective film remains intact during deep drawing stretching. A tensile strength of ≥11MPa in the MD direction and ≥10MPa in the TD direction withstands the tensile stress during deep drawing, preventing the film from breaking due to excessive force. It also ensures the film maintains its protective performance after stretching, preventing damage or detachment. This parameter meets the performance standards of CPE protective film in the field of metal deep drawing. It is suitable for the stress characteristics of deep drawing processes while also taking into account the flexibility of the film, avoiding excessive tensile strength that would lead to an overly rigid film that is difficult to stretch.
5. Adhesion: 450-850g Controlling the adhesion between 450-850g is key to balancing adhesion stability and easy peeling. On the one hand, an adhesion of over 450g ensures that the protective film adheres tightly to the stainless steel sheet surface during deep drawing, preventing lifting or detachment. Even under high temperature and high pressure deep drawing environments, it maintains stable adhesion, preventing protective failure due to film displacement. On the other hand, an adhesion of under 850g ensures that the protective film can be easily peeled off during subsequent use, leaving no adhesive residue and not damaging the gloss of the stainless steel surface, reducing subsequent cleaning processes and lowering production costs. This adhesion range is suitable for the application scenarios of stainless steel deep drawing and meets the core characteristics of CPE protective film: no adhesive residue and easy peeling, effectively improving the yield rate of deep-drawn products.
III. Conclusion The core requirements for protective films in deep-drawn stainless steel vessels focus on process adaptability, protection, and convenience. CPE protective film's parameters (80-micron thickness, dark blue/light blue color, specific ductility, tensile strength, and adhesion) precisely match these requirements. It not only meets the stretching and protection needs during deep-drawing but also ensures convenient, residue-free, and damage-free subsequent use, making it an ideal choice for surface protection of deep-drawn stainless steel vessels. This also aligns with the core advantages of CPE protective film in the metal deep-drawing field: "impact resistance, high ductility, and no residue."
