- Core Material Components for Waterproof Custom Labels
The waterproof performance of a label is not determined by a single material, but by the combined effect of the substrate, surface coating, and adhesive. If any one of these fails to be waterproof, the entire label will fail:
Substrate: Acts as the “carrier” of the label and must resist water penetration to avoid deformation, dissolution, or delamination when exposed to water.
Surface Coating: Covers the printed layer to prevent water from damaging the print (e.g., ink bleeding) and enhances abrasion resistance.
Adhesive: Ensures the label stays attached in humid environments, requiring water- and moisture-resistant properties to prevent loss of stickiness when wet.
Among these, the substrate forms the foundation of waterproofing, while the coating and adhesive serve as reinforcement. For example, if the substrate itself is highly absorbent (like regular paper), even with waterproof coating, the label may deform due to substrate swelling—thus, “waterproof substrate” is the primary requirement.
- Main Types of Waterproof Substrates and Their Suitable Applications
(a) Plastic Substrates: Cost-Effective Basic Waterproof Choice
Plastic substrates do not absorb water and have strong water resistance, making them mainstream choices for waterproof custom labels. They suit most medium-to-low humidity scenarios (e.g., short-term splashing, daily moisture), with moderate cost and ease of processing.
Polyethylene (PE)
Features: Soft texture, resistant to low temperatures (-40°C to 60°C), chemical-resistant (oil, detergents), but poor high-temperature resistance (deforms above 60°C). Smooth surface requiring corona treatment for better ink adhesion.
Applications: Outdoor temporary labels (e.g., garden plant tags), refrigerated food labels (e.g., beverage bottle labels inside refrigerators), oily environment labels (e.g., machinery parts).
Advantages: Low cost (~0.1–0.3 RMB per A4-sized sheet), suitable for mass customization; available transparent or colored to meet personalized needs.
Polypropylene (PP)
Features: Harder and stiffer than PE, better high-temperature resistance (~100°C short term), surface also requires pretreatment for printing. Available as cast-coated PP (smooth) and woven PP (textured, more abrasion-resistant).
Applications: Kitchen product labels (e.g., dish soap bottles), waterproof cosmetic labels (e.g., body wash bottles), outdoor tool labels (e.g., gardening shears).
Advantages: Balances softness and stiffness, ideal where shape retention is needed; higher color fidelity than PE, suitable for patterned custom labels.
Polyvinyl Chloride (PVC)
Features: Hard, acid- and alkali-resistant, extremely waterproof (can be soaked long-term), withstands temperatures up to 80°C, but brittle below 0°C; typically thicker (0.1–0.3mm), stiff, can be made into “rigid labels.”
Applications: Bathroom product labels (e.g., shampoo or body wash bottles frequently exposed to water), water pipe/pipe markings (long-term humid environments), industrial equipment labels (e.g., internal parts of washing machines).
Notes: Contains plasticizers, not suitable for direct food contact (e.g., inner food packaging labels), may release harmful substances under high heat; avoid in microwave or high-temperature environments.
(b) Synthetic Paper Substrates: Paper-Like Feel with Waterproofing
Synthetic paper is not actual paper but plastic-based (usually polypropylene or polyethylene), combining paper-like printability (no special pretreatment needed) with plastic’s waterproof properties. Suitable for applications requiring a paper look but waterproof features.
Synthetic Paper (e.g., Tyvek)
Features: Lightweight (density 0.9 g/cm³, 30% lighter than normal paper), tear-resistant (5x tensile strength of paper), withstands -73°C to 100°C, recyclable and more eco-friendly than PVC.
Applications: Long-term outdoor labels (e.g., tourist signs, outdoor billboards), medical supplies (e.g., sterilization instrument tags resistant to alcohol wipes), marine equipment labels (short-term immersion).
Advantages: Printing quality close to paper (supports inkjet, laser, flexo printing), ideal for custom labels needing a “paper feel” with waterproofing (e.g., luxury waterproof gift box labels).
(c) Metal Substrates: High-Strength Waterproofing for Extreme Conditions
Metal substrates offer top-level waterproofing, abrasion resistance, and high-temperature tolerance, suitable for long immersion, high humidity, and highly corrosive environments. Due to high cost and processing difficulty, used mainly where high durability is needed.
Aluminum Foil
Features: Completely waterproof (impermeable), withstands temperatures above 200°C, chemically resistant (acid and alkali), but soft and prone to scratches.
Applications: Industrial pipeline labels (long water and chemical exposure), automotive engine bay labels (high temp/humidity), deep-sea equipment temporary tags (short immersion).
Notes: Must use temperature-resistant waterproof adhesives (e.g., silicone-based) to avoid failure; requires special metal inks for printing to prevent peeling.
Stainless Steel Foil (Ultra-thin)
Features: Harder than aluminum, wear- and rust-resistant (suitable for seawater and corrosive environments), but very costly (3-5 times aluminum) and less flexible (difficult to adhere to curved surfaces).
Applications: Marine engineering equipment labels (long seawater immersion), chemical storage tank markings (corrosive liquid contact).
(d) Special Treatment Substrates: Low-Cost Waterproofing Modifications
For low cost and basic waterproofing, common materials can be treated (wax dipping, lamination), but waterproofing is weaker and suitable only for short-term or temporary use (not recommended for long-term).
Waxed Paper
Features: Ordinary paper dipped in wax to form a hydrophobic layer, provides short-term splash resistance (~30 minutes), but long exposure causes wax to wear off and fail; extremely low cost (~0.05 RMB per sheet).
Applications: Disposable outdoor event tags (e.g., picnic supplies), short-term moist environment temporary labels (e.g., watering reminders on potted plants).
Laminated Paper (BOPP Film)
Features: Paper covered with BOPP plastic film that blocks moisture, resists splashes and light wiping; substrate remains paper so edges can delaminate if wet. Good print quality (supports full color).
Applications: Waterproof gift box labels (protect from rain during shipping), cosmetic gift box labels (daily moisture resistance).
- Auxiliary Waterproof Design: Surface Coatings and Adhesives
Surface Coatings: Enhance Waterproofing of Printed Graphics
Even if the substrate is waterproof, ink can bleed when exposed to water, blurring label information. The surface coating’s key role is to protect the printed layer.
