What types of paper bags are there?

Types of Paper Bags
1. By Material
White cardboard: Thick and smooth, suitable for high-quality printing (210-300g/m²)
Coated paper: Smooth, high whiteness, good printing results, but slightly less stiff than white cardboard
White kraft paper: Environmentally friendly and tough, commonly used in reusable shopping bags (120-200g/m²)
Kraft paper: High burst resistance, darker color, suitable for single- or two-color printing
2. By Number of Layers/Structure
Single-layer paper bag: The simplest structure, suitable for lightweight goods.
Double-layer (overbag): Two layers of paper are laminated for increased strength and moisture resistance.
Multi-layer composite bag: Paper layer + PE/PP film or aluminum foil layer, combining rigidity and waterproofing.
3. By Application
Food bags: Used for packaging candy, baked goods, and fast food, often with moisture-proof treatment.
Gift bags: Emphasize appearance and decoration, and can use high-end paper and hot stamping.

Garment bags: These require stiffness and load-bearing properties, often made of kraft paper or double-layer construction.
Agricultural/Gardening Bags: These bags, such as fruit and seed bags, require breathability and waterproofing.
4. Classification by Function/Special Treatment:
Waterproof/Moisture-Proof Paper Bags: Surface waxing or lamination enhances water resistance.
Oil-Proof Paper Bags: Ink or special coatings are added to the inner layer, suitable for oily foods.
Degradable Paper Bags: Use FSC-certified paper to meet environmental requirements.
How can paper bags be improved in terms of waterproofing and moisture resistance?
Measures to Improve Waterproofing and Moisture-Proofing Performance of Paper Bags
1. Surface Coating or Waxing: Spraying wax emulsion or polyethylene (PE) coating on the paper surface creates a waterproof layer, significantly improving water repellency.
2. Composite Film Lining (PE/PP): Adding polyethylene film to the inside of a paper bag creates a paper-plastic composite bag that prevents moisture vapor penetration and is commonly used for moisture-proofing food packaging. 3. Multi-layer Structure Design
A double or triple-layer structure (paper-film-paper) is used, with interlayer bonding enhancing overall rigidity and moisture resistance, making it suitable for transportation and storage in high-humidity environments.
4. Production Process Testing and Quality Control
A water splash test is used to quickly assess the waterproofness level. When necessary, a more rigorous water immersion test is used to ensure compliance with national standards such as GB/T7350.
Pre-treatment to prevent moisture (e.g., spraying with a moisture-proofing agent) is performed before packing. After packaging, the product is stored in a dry and ventilated environment to prevent moisture from forming later.