How to Make Express Delivery Bags

From Raw Materials to Delivery: An In-Depth Analysis of the Professional Manufacturing Process and Industry Trends of Express Delivery Bags

In today’s booming e-commerce industry, express delivery bags, as the "last mile" armor for the circulation of goods, are undeniably important. A high-quality express delivery bag not only ensures the safety of goods during transportation but also reflects a company’s environmental responsibility and brand image. This article systematically elaborates on the entire manufacturing process of express delivery bags, providing a professional and rigorous perspective to unveil the industrial intricacies behind this everyday item.

Chapter 1: Selection and Proportioning of Raw Materials—The Foundation of Quality

The performance of an express delivery bag primarily depends on its raw materials. Currently, mainstream express delivery bags in the market are mainly composed of the following materials:

Polyethylene (PE): This is the most common raw material for express delivery bags. Based on density, it can be categorized into:

Low-Density Polyethylene (LDPE): Soft in texture, good extensibility, and strong tear resistance. Often used for making flat-mouth express delivery bags that require certain cushioning properties.

High-Density Polyethylene (HDPE): Relatively rigid material, high tensile strength, and puncture resistance, but poor flexibility. Mostly used for making envelope-style express delivery bags or packaging requiring higher stiffness.

Linear Low-Density Polyethylene (LLDPE): Combines the softness of LDPE and the strength of HDPE, making it an ideal material for high-performance express delivery bags. It is often blended with LDPE to optimize performance and cost.

Biodegradable Materials: To address environmental challenges, biodegradable express delivery bags are gradually gaining popularity. These mainly include:

Biodegradable Plastics (e.g., PLA/Starch-Based): Can be broken down into water and carbon dioxide by microorganisms under specific composting conditions.

Photo-Oxodegradable Plastics: Molecular chains break under the influence of light and oxygen, eventually degrading.

Fully Biodegradable Materials (e.g., PBAT/PLA Blends): Currently the most technologically mature and environmentally recognized biodegradable solution, capable of achieving relatively complete biodegradation in natural environments.

Professional Proportioning Recommendations:

Standard PE Bags: A 7:3 blend of LDPE and LLDPE achieves a good balance between cost and performance.

High-Strength Bags: Increase the proportion of LLDPE or add a certain proportion of HDPE to enhance puncture resistance.

Biodegradable Bags: Typically use PBAT and PLA as the main base materials, supplemented with fillers like starch. The specific proportions need to be adjusted based on degradation standards (e.g., China’s GB/T 38082) and physical performance requirements.

Chapter 2: Core Production Process—Precision in Craftsmanship

The production of express delivery bags is a continuous, automated process, with the following core steps:

Step 1: Film Blowing

This is the core process for manufacturing plastic films. The proportioned plastic pellets (or biodegradable masterbatch) are fed into an extruder, where they are heated and sheared into a molten state. The molten plastic is extruded through a die to form a tubular film bubble. Compressed air is blown into the bubble, causing it to expand, stretch, and cool, eventually forming a film roll through traction rollers. The key to this process lies in controlling the blow-up ratio, traction speed, and cooling efficiency to obtain a film with uniform thickness and stable mechanical properties.

Step 2: Printing

Based on customer requirements, brand logos, address fields, environmental labels, and other content are printed onto the rolled film. Flexographic printing is primarily used due to its low plate-making cost, fast printing speed, and wide applicability to various substrates. Before printing, corona treatment is required to increase the film’s surface tension and ensure ink adhesion.

Step 3: Bag Making

This is the critical step of converting the film roll into the final bag product. The entire process is completed on an automated bag-making machine:

Folding: The film roll is precisely folded into the bag body through guide rollers.

Heat Sealing: Heat sealing blades are used to apply heat and pressure at preset positions (usually the sides and bottom) to fuse the plastic film and form sealed edges. Heat sealing temperature, pressure, and time are the three core parameters determining seal strength and must be precisely controlled based on material characteristics.

Cutting and Punching: Continuous heat-sealed film is cut into individual bags using precision blades, while simultaneously punching easy-tear openings or handhold holes.

Collection and Counting: Finished bags are automatically stacked, counted, and packaged into specified quantities (e.g., 500 bags per bundle).

Chapter 3: Quality Control and Performance Testing—Professional Assurance

A qualified express delivery bag must pass a series of rigorous tests to ensure its reliability during the logistics process.

Thickness Test: A thickness gauge is used to measure the thickness at various points of the bag, ensuring compliance with standards (e.g., 0.05mm–0.08mm is a common range). Uniform thickness is a prerequisite for consistent strength.

Tensile Strength and Elongation at Break Test: A universal material testing machine simulates the bag’s performance under longitudinal and transverse, ensuring it is not easily torn.

Puncture Resistance Test: Simulates scenarios where the bag is pierced by sharp objects, a key indicator of its protective capability.

Seal Strength Test: Evaluates the firmness of sealed edges under peeling force to prevent opening or bursting during transportation.

Drop Test: Items of specified weight are placed in the bag and subjected to free-fall tests from different heights and angles to comprehensively evaluate the bag’s overall performance.

Environmental Performance Test (for biodegradable bags): Requires sending samples to professional laboratories to test biodegradation rate, heavy metal content, and other indicators according to relevant standards.

Chapter 4: Industry Trends and Innovation Frontiers

The manufacturing technology of express delivery bags is not static; it continues to evolve with market demands and technological advancements.

Green and Sustainable Development: The research and application of biodegradable and recyclable materials are absolute mainstream trends. Meanwhile, "lightweighting" designs minimize raw material usage while ensuring performance, achieving plastic reduction at the source.

Intelligence and Informatization: The integration of express delivery bags with the Internet of Things has led to "smart bags" with built-in RFID chips or printable electronic labels, enabling full tracking and information management of packages.

Functionalization and Personalization: Beyond basic waterproofing and shock resistance, additional features such as self-sealing, anti-theft, and anti-information leakage (e.g., kraft paper lining) have been introduced. Customized printing services have also matured, becoming new touchpoints for brand marketing.

Exploration of New Materials: Materials such as inorganic eco-friendly plastic bags made from stone powder and calcium carbonate, as well as bio-based materials extracted from seaweed and agricultural waste, offer more possibilities for future sustainable development.

Conclusion

The production of a seemingly simple express delivery bag is, in fact, a systematic engineering project that integrates polymer material science, precision mechanical design, and automation control technology. From the scientific proportioning of raw materials to the precise control of each step in film blowing, printing, and bag making, and the strict quality inspections before leaving the factory, every aspect reflects the professionalism and rigor of modern manufacturing. As environmental regulations become increasingly stringent and consumer demands continue to rise, the manufacturing process of express delivery bags will inevitably evolve toward greener, smarter, and more diverse directions, providing safer and more efficient packaging solutions for the global logistics system.