New Progress in Composite Materials Technology: Dry Lamination, Extrusion Coating, and Solvent - Free Processes

2026-03-20 10:39:45

Introduction

Composite materials technology has witnessed remarkable advancements in recent years, particularly in dry lamination, extrusion coating, and solvent - free processes. These technologies have revolutionized the packaging and manufacturing industries by offering enhanced performance, cost - effectiveness, and environmental friendliness. This article will delve into the new progress of these three composite technologies, exploring their principles, advantages, disadvantages, and future development trends.

1. Overview of Dry Lamination

Dry lamination is a common method in the production of plastic packaging bags. In this process, an adhesive is evenly coated onto a carrier film through an anilox roller. The coated film then passes through an oven to dry the adhesive, and finally, it is laminated with another film under pressure at the laminating section to form a composite film.

It has several advantages. Firstly, it offers a wide range of substrate choices. It can perform composite operations between various materials, such as plastic - to - plastic, plastic - to - paper, plastic - to - metal, as well as combinations with fabric and non - woven materials. Even paper - to - metal composites are possible without the presence of plastic. Secondly, the lamination strength is relatively high. The inter - layer peel force can reach over 1000g/25mm width, enabling the production of high - end packaging products like high - temperature retort pouches. Thirdly, the thickness of each layer can be freely selected and precisely controlled. Fourthly, it supports both surface printing and reverse printing. Finally, the production speed is fast, with a general operating speed ranging from 150 - 180㎡/h and a maximum speed of over 200m/h.

However, dry lamination also has some drawbacks. Since adhesives are used, there is a problem of residual solvent toxicity. As a result, dry - laminated packaging materials, especially those using two - component polyurethane adhesives, cannot be sold in the North American and European markets but are mainly sold in Southeast Asia, Africa, and other regions. Although in China and Japan, dry - laminated products that meet national standards can be used for food and pharmaceutical packaging (the health standard is that the total amount of residual toxic components ≤15mg/㎡), the use of a large amount of solvent - based adhesives leads to environmental pollution from organic solvent volatilization and the risk of flammability and explosion. Additionally, the high adhesive consumption in dry - laminated films results in high costs and relatively expensive prices.

2. New Progress in dry lamination adhesive Technology

To overcome the problems associated with traditional dry lamination adhesives, such as solvent residues, high toxicity, and poor stability, researchers have made significant progress. For example, a single - component self - crosslinking emulsion adhesive for dry lamination has been developed using seed emulsion polymerization and pre - emulsification processes.

This adhesive is prepared by compounding environmentally friendly emulsifiers and cross - linking monomers. It is solvent - free, non - toxic, and has high stability, significantly improving the environmental friendliness and application performance of the adhesive. The main performance indicators of this adhesive are excellent. Its solid content ranges from 45% - 55%, with a pH value between 7.0 - 8.0 and a viscosity of 100 - 300mPa·S. It has good freeze - thaw stability, a storage stability of over 6 months, a peel strength greater than 400N/m, an ink transfer rate of 100%, and passes high - and low - temperature tests and indentation and embossing tests without bubbling.

The preparation process of this adhesive is as follows: First, a certain proportion of emulsifiers and water are placed in a pre - emulsification tank, and a mixture of hard monomers, soft monomers, (meth)acrylic acid, and cross - linking monomers is slowly added for emulsification. Then, in the reactor, a certain amount of water, emulsifiers, initiators, and sodium bicarbonate are added as the bottom liquid, and the temperature is raised. After adding a portion of the pre - emulsified liquid and waiting for the appearance of a blue light, the remaining pre - emulsified liquid and initiator solution are simultaneously added drop - wise. Finally, the temperature is raised for further reaction, and after cooling, the pH is adjusted, and functional additives are added.

3. extrusion coating process

Extrusion coating is a process in which a molten polymer is extruded through a die and coated onto a substrate to form a composite material. This process is widely used in the packaging industry, such as coating polyethylene on paper or cardboard to improve its moisture - resistance and barrier properties.

One of the main advantages of extrusion coating is its high production efficiency. The extrusion process can be carried out continuously at high speeds, enabling large - scale production. Moreover, it has good adhesion to a variety of substrates, forming a strong and durable composite structure. The coated layer can also provide excellent barrier properties against moisture, oxygen, and other gases, protecting the contents of the package.

However, extrusion coating also has some limitations. The coating thickness is more difficult to control precisely compared to other processes. It requires high - temperature operation, which may cause thermal damage to some heat - sensitive substrates. Additionally, the choice of polymers for extrusion coating is relatively limited, and not all polymers are suitable for this process.

4. New Developments in Extrusion Coating

In recent years, there have been some new developments in extrusion coating technology. Advanced die designs have been introduced to improve the uniformity of the coating thickness. Computer - controlled extrusion systems can adjust the extrusion parameters in real - time according to the production requirements, ensuring more precise coating thickness control.

New polymer materials have also been developed for extrusion coating. These polymers have improved properties such as better barrier performance, higher heat resistance, and enhanced adhesion. For example, some biodegradable polymers are being used in extrusion coating to meet the growing demand for environmentally friendly packaging.

Another development is the combination of extrusion coating with other processes. For instance, it can be combined with printing or lamination processes to create multi - functional composite materials. This integration allows for the production of more complex and high - value - added packaging products.

5. Solvent - Free Composite Technology

Solvent - free composite technology is a revolutionary development in the field of composite materials. Unlike traditional composite methods, it does not use organic solvents, which brings many benefits. Firstly, it is environmentally friendly. Since the adhesive does not contain solvents, there is no pollution caused by solvent emissions. The noise level of solvent - free equipment is much lower than that of solvent - based equipment. The noise of solvent - free composite equipment is generally between 70 - 75dB, while that of solvent - based equipment is between 85 - 100dB. Secondly, it is cost - effective. In terms of equipment investment, solvent - free composite equipment is more compact, occupies less space, and has a lower cost than solvent - based equipment. It also does not require a solvent warehouse. In terms of energy consumption, the motor power of solvent - free equipment is dozens of kilowatts less than that of solvent - based equipment. Thirdly, it is hygienic and safe. It avoids the pollution of contents by residual solvents and the generation of odors, making food packaging safer. Moreover, there is no risk of fire or explosion due to the absence of solvents, eliminating the need for explosion - proof measures. Finally, it can improve product quality. Since the operating temperature is lower than that of solvent - based processes, it will not cause film deformation at high temperatures. Currently, most common composite film substrates can be produced using solvent - free adhesives, and even composite films resistant to high - temperature retort at 121°C can be manufactured by this method.

However, solvent - free composite technology also has some disadvantages. The entire system needs to be heated during adhesive coating, and the coating machine needs to be insulated. The pot life of the mixed adhesive is short, usually no more than 30 minutes. It is still difficult to meet the requirements for heavy - duty packaging, products with high resistance to media, and ultra - high - temperature sterilization. The initial adhesion is low, and the curing time is long. High precision is required for coating.

6. Future Trends of Composite Materials Technology

Looking ahead, the future trends of composite materials technology, including dry lamination, extrusion coating, and solvent - free processes, are promising. There will be a greater emphasis on environmental friendliness. With the increasing global awareness of environmental protection, the development and application of biodegradable, recyclable, and low - carbon composite materials will be accelerated. For example, more research will focus on developing new adhesives and polymers that are environmentally friendly and can be easily recycled. In terms of performance improvement, continuous efforts will be made to enhance the adhesion strength, barrier properties, heat resistance, and mechanical properties of composite materials. New materials and processes will be developed to meet the requirements of high - end applications, such as aerospace, automotive, and electronic industries. The integration of different composite technologies will also become more common. By combining the advantages of dry lamination, extrusion coating, and solvent - free processes, more complex and high - performance composite materials can be produced. This integration will require more sophisticated equipment and process control systems. Automation and intelligent manufacturing will play a key role in the future of composite materials technology. Computer - controlled production lines, sensors for real - time monitoring, and artificial intelligence - based process optimization will improve production efficiency, reduce production costs, and ensure product quality consistency.

In conclusion, the new progress in dry lamination, extrusion coating, and solvent - free processes of composite materials technology has brought about significant changes in various industries. Although each technology has its own advantages and disadvantages, continuous innovation and improvement will likely lead to more efficient, cost - effective, and environmentally friendly composite solutions in the future.