Introduction
As the "leader" in the packaging industry, corrugated boxes have almost contracted the packaging needs of all walks of life with their strong, durable and affordable characteristics. But do you know? The key to whether these boxes are reliable or not depends on the materials used in production.
Knowing the "inside story" of corrugated boxes will help manufacturers, merchants and ordinary consumers to choose packaging that suits their needs more wisely. Let’s take a look at the main materials for making corrugated boxes, see what they are, and how they affect the quality of the boxes.
Main Raw Materials Used in Corrugated Cardboard Production
Corrugated cardboard is actually a "sandwich" structure, and each of the three layers has its own job:
Surface layer (outer lining cardboard): It is the smooth "face" on the surface of the carton, which must be both beautiful and durable.
Lining layer (inner lining cardboard): The "powerful" hidden inside, whose main task is to support the carton and make it more pressure-resistant.
Wave sandwich layer (grooved middle layer): The one twisted into a wave shape in the middle is the soul player, which can not only reduce shock and resist falling, but also make the cardboard stiff and not soft.
The paper used for these three layers is very particular – some are made of new wood pulp, some are recycled waste paper, and some are mixed and matched "practical". It all depends on what performance you want!
1. Kraft paper
Kraft paper, to put it bluntly, is the "bulletproof vest" of the packaging industry! It is made directly from real wood (mainly tough tree species such as pine and fir) beaten into wood pulp. In the packaging industry, kraft paper is synonymous with "high-end goods".
Resistant to falling and beating: thick and tear-resistant, good elasticity, and not easy to crack when bumped at corners
Not afraid of moisture: It can withstand even a little moisture, and it is not easy to soften after being stored in the warehouse for a long time
Appearance online: The color reproduction is super high, and the logo is printed on it, which is particularly high-end.
2. Recycled cardboard
This is a cardboard made of 100% recycled waste (old cartons, waste newspapers, office waste paper, etc.) re-pulped, which is equivalent to giving waste paper a "second life". Although it is not as hard-hitting as kraft paper, it is cheaper and more environmentally friendly.
These are the following three features:
- Economy – the cost is 30% lower than that of new cardboard.
- Green – the production process saves water, electricity and cuts fewer trees.
- Smart – different needs can be met by adjusting the ratio "Change to AI speech
3. Corrugated media (corrugated layer)
What is corrugated media?
The wavy "skeleton" in the middle of the corrugated board provides cushioning and structural rigidity, making the carton resistant to pressure and shock. This material is made of the following materials:
1) Semi-chemical pulp (wood is lightly chemically treated to make the fibers stiffer and used for more rugged applications).
2) Recycled pulp (waste paper is recycled, low cost but slightly weaker, and is an option for light packaging).
Characteristics of corrugated media
- Buffering capacity: can absorb more than 60% of the impact during transportation
- Invisible load-bearing capacity: 1㎡ of corrugated layer can withstand 1 ton of pressure.
- Material saving secret: hollow structure saves 30% of materials compared to solid cardboard, but is more resistant to pressure
When is corrugated media used?
- Transport and moving boxes
- Protective packaging for fragile items
- Storage boxes for stacking and compression resistance
- Invisible guard for fresh cold chain Special waterproof corrugated layer
4. Adhesive (glue for layer bonding)
What adhesive is used?
Corrugated cardboard is bonded together using starch-based adhesives that:
- Derived from corn, wheat or potato starch.
- Environmentally friendly and biodegradable.
- Cost-effective and non-toxic.
In some cases, synthetic adhesives are used for waterproofing or high-strength applications.
Why Adhesives Are Important
- Ensures a strong bond between layers.
- Increases box durability and tear resistance.
- Impacts moisture resistance and longevity.
When are Special Adhesives Used?
- Waterproof boxes (PE coated adhesive).
- Heavy-duty packaging (fortified glue for added strength).
- Environmentally friendly applications (biodegradable starch-based glue).
5.Additives and Coatings
Waterproof coating
Type: Acrylic coating (food grade).
Features: After coating, it can reach the highest waterproof standard of R10, and the surface water absorption is only 2.65g/m, which can be used as a container to hold water.
Application: Widely used in the packaging of frozen products, medical products and e-commerce cold chain products, etc.3
Anti-rust coating
Type: Coating containing rust inhibitor.
Features: The effective anti-rust time can be up to 2 years, and the packaging cost is low, which reduces environmental pollution.
Application: Currently mainly used in machinery, instrumentation, automotive parts and other industries
Anti-scratch coating
Type: Coating with viscosity and dynamic damping.
Features: The coating itself is viscous. When it moves relative to the contents, it can generate a certain resistance, which is proportional to the square of the speed, which can attenuate the motion energy and avoid scratches on parts.
Application: It can cheaply and effectively solve the problem of repeated friction between products and the inner wall of corrugated boxes causing scratches.
Oil-resistant coating
Type: Appropriate varieties of oil-resistant coating (food grade is often used in non-industrial fields).
Features: It can avoid the problem of corrugated boxes failing due to oil seepage from packaged products, and the oil-resistant performance can last up to 2 years.
Application: The inner wall of the widely used pizza box is coated with food-grade oil-resistant coating.
5. Fresh-keeping coating
Type: Ceramic coating liquid that can release far infrared rays, etc.
Features: Antibacterial and fresh-keeping of fruits and vegetables, so that fruits and vegetables maintain the lowest level of aerobic respiration, and lock in moisture to prevent evaporation, thereby preventing microbial erosion and extending the shelf life.
Application: Used for fruit and vegetable packaging to achieve fresh-keeping function
Choosing the Right Raw Materials for Your Needs
Choosing materials is like matching equipment. The key is to consider three points: whether it is hard-core enough, whether it is environmentally friendly, and whether it is cost-effective. Different occasions have different matching methods. You can choose completely according to your personal preferences.
Summary
Corrugated boxes may seem simple, but they are actually made of a variety of materials. The main materials include kraft paper, recycled cardboard, corrugated core paper, glue and various functional coatings. The choice of each material directly affects the final performance of the box.
In the packaging industry, the requirements for cartons for different purposes vary greatly. Express delivery requires pressure resistance and drop resistance, supermarket displays require exquisite appearance, and industrial packaging pays more attention to load-bearing and stacking strength. To design a packaging solution that is both durable and economical, you must thoroughly understand the characteristics of these materials.
Nowadays, environmental protection has also become a factor that cannot be ignored. How to ensure performance while taking into account sustainability is indeed a topic worthy of in-depth research.