A few days ago, the China Consumers Association issued a consumer warning to prevent electromagnetic radiation pollution. The issue of human health in the era of modern electronics once again aroused our concern. This article reviews the development trend of functional packaging for electromagnetic radiation protection from the perspective of packaging.

Whether it is a classical packaging textbook or a modern packaging technology book, most of the functions of packaging are summarized into three major functions: protecting products, facilitating storage and transportation, and promoting sales. Packaging is one of the important means to realize the value and value of products. In the production process, packaging is the last important process; in the process of circulation, packaging plays an important role in the protection, beautification, promotion, storage, transportation, sales, and use of goods; in the international market Packaging reflects the degree of development of a country in terms of economy, technology, science, and culture and relates to the reputation of its products.

In order to achieve the packaging function, it is necessary to use reasonable packaging materials and a certain packaging technology. In the process of circulation, items are subject to various external influences and damages, such as shocks, impacts, collisions during transportation, temperature and humidity during storage and transportation, radiation, electromagnetic fields, and microorganisms. Therefore, the use of reasonable packaging materials should have corresponding protective functions. In general, the packaging industry currently divides commonly used functional packaging materials into the following eight categories.

First, barrier packaging materials, including gas barrier type, moisture barrier type (water vapor), fragrance barrier type (perfume type) and light barrier type. The second is heat-resistant packaging materials, mainly microwave oven heating type. The third is to select the permeability packaging material, which is a high-grade packaging material that has barrier properties to certain atmospheres while being permeable to other atmospheres. The fourth is fresh-keeping packaging materials, which have both the function of slow-ripening and fresh-keeping, as well as the ability to inhibit bacteria and prevent bacteria. Fifth, conductive packaging materials, due to different additives made of different conductive properties of the material, or anti-static, or used to prevent electromagnetic interference. Sixth, it is a decomposable packaging material, such as a biodegradable type, a photodecomposable type, and a thermal decomposition type. Seventh, other functional packaging materials, such as edible packaging materials, anti-corrosive packaging materials, smart packaging materials, and the like.

1. Functional Packaging Materials Overview

Functional packaging materials are only a member of the large family of functional materials. In order to fully understand functional packaging materials, it is necessary to first look at the outline of functional materials.

The so-called functional materials are the confluence of special materials and composite materials that can transfer, convert or store substances, energy, and information. The functional sources of such materials generally have two approaches: one is the special function of the material itself, called structural functional materials; the other is based on common materials, in which the addition of a specific function Another material, called composite functional material.

Most of the functional materials are new materials for high-tech research and development, and their special functions often involve multiple disciplines. It is difficult to develop and has a long development cycle. Functional materials have obvious features and advantages. They are generally characterized by light weight, easy processing, special functions or specific purposes, special applications, high added value, and high economic benefits. These characteristics are also evident in functional packaging materials.

There are many kinds of modern functional materials and their development is very rapid. Therefore, the classification of functional materials is also complicated. This article classifies according to the attribution of the function of the material, for the multifunctional material and the multi-functional packaging material, will be divided according to the attribution of its main function. The classification of functional materials related to packaging is described below.

(1) Electrically functional materials

The electrical functional materials mainly include conductive functional materials, photoelectric functional materials, thermoelectric functional materials, electrical storage functional materials, dielectric functional materials, and the like. Among them, the development of electrically functional materials having conductive, semiconducting, and superconducting characteristics is particularly rapid, and structural conductive polymers, composite conductive plastics, and the like are also used in antistatic packaging and electromagnetic shielding packaging.

(2) Optical functional materials

Such materials mainly include photoconductive functional materials, polarized light functional materials, photochemical reaction materials, light color functional materials, and the like. Among them, photochemical reaction materials, photochromic functional materials, etc. have also been applied in the field of packaging, such as photodegradable plastics and the like.

(3) Chemical functional materials

This class of materials refers to chemically reactive functional materials, catalytically functional materials, adsorption functional materials, desorption functional materials, and the like. Among them, the high water-absorbent resin can absorb water more than 500 times its own weight, which has been well applied in the food packaging field and has been well received.

(4) Thermal functional materials

The thermal functional materials include thermo-optical functional materials, thermal-sensitive functional materials, thermal-deformable functional materials, thermal-insulating functional materials, heat-resistant functional materials, and the like. Among them, thermochromic materials and thermoluminescent materials are also exposed in anti-counterfeiting packaging. Flame-retardant packaging materials are also favored by the packaging industry.

(5) Magnetic functional materials

The magnetic functional materials mainly include magnetic conductive functional materials, hysteresis functional materials, and magnetic fluid functional materials. Among them, hysteresis seal materials used for packaging and sealing technology, can greatly improve the sealing strength of flexible bags, and magnetic ink for anti-counterfeiting packaging, praised by manufacturers.

(6) Mechanical functional materials

Such functional materials mainly include

Quality functional materials, force-electricity conversion functional materials, etc. The separation membrane in the former has the function of selectively permeating certain substances and preventing the penetration of other substances, and is expected to occupy a place in the packaging industry, particularly in the food packaging industry.

(7) Biological functional materials

Biological functional materials mainly refer to biomimetic functional materials, bioengineered materials, pharmaceutical functional materials, human functional materials, and so on. Among them, biodegradable plastics have also stirred up a wave of applications in the field of packaging engineering. The research of microbial plastics has successfully injected vitality into the packaging industry.

(8) Friction material

Such functional materials include drag-reducing functional materials, resistance-enhancing functional materials (anti-slip functions), lubricating functional materials, and the like. Among them, drag-reducing functional materials and non-slip functional materials have also become one of the goals tracked by packaging researchers, and have also been applied in the production of packaging materials and packaging containers.

(9) Adhesive functional materials

This type of functional material is mainly adhesive

Functional materials, sealing functional materials, their application in the packaging area for a long time, the application of a wide range, is already a packing science and technology personnel are familiar with a packaging material.

(10) Memory functional materials

The memory functional materials mainly include shape memory functional materials, which are characterized by being able to remember the original form after deformation, and by simply placing the material in a suitable temperature field, the original shape can be completely restored, and as long as the polymer chain is not destroyed This deformation and recovery can be repeated over a long period of time. Shrink-wrapped packaging is a typical use case for such materials in packaging.

According to the literature data, the current evaluation criteria and management aspects of functional packaging materials are still confusing. This is mainly manifested in several aspects: the terminology is not uniform, the specifications are different, and the testing methods are different. It can be said that currently there is no universally accepted international standard, and each country formulates and implements its own standards for individual administration. This undoubtedly brings certain difficulties to the evaluation and management of materials.

In view of this, the standardization of functional packaging materials is a matter of urgency. It is recommended that reference should be made to the adoption of internationally more widely used standards. This is beneficial for the research and development of functional packaging materials and series. $Page break $

2. Anti-electromagnetic function packaging

In 1894, the great physicist C.A. Popov invented the radio and founded the electromagnetic wave propagation theory. While electromagnetic waves serve a variety of undesirable effects while serving people, scientists soon noticed this. In 1934, the CISPR, the international organization that administers electromagnetic waves, was established. In 1952, the Federal Republic of Germany took the lead in the development of the VDE regulations for electromagnetic interference (EMI) regulations. In 1976, the United States established the FCC regulations and was equivalently adopted by many countries. Following the FCC regulations, Britain, Canada, Japan and some other countries have established their own relevant laws and regulations.

From the above, the seriousness of the EM I and the need to strengthen regulation. In the past 10 years, the electromagnetic wave source in China has increased rapidly, and the annual growth rate of big cities such as Beijing is above 20%. This has attracted the attention of environmental experts and government officials, and China's electromagnetic shielding and packaging materials have only started.


3 . Versatile packaging

Just as packaging science is an edge science involving many disciplines such as physics, chemistry, mechanics, materials science, aesthetics, and psychology, packaging materials must satisfy three major functions and adapt to many external environments, relying only on the above-mentioned single functions. Can not meet the market requirements, therefore, packaging materials often need to be made of dual-function or multi-functional packaging materials.

(1) Electromagnetic Shielding - Anti-Static Packaging Materials

In general, electromagnetic shielding packaging materials (packaging containers) are not single-function type. According to actual needs, they are often provided with anti-static function when they have EMI shielding properties, and become truly dual-functional materials. Its antistatic ability is usually conferred by coating an antistatic agent on the inner and outer surfaces of an electromagnetic shielding composite packaging material (container). For example, the application of an antistatic agent inside and outside the aluminum-plastic composite packaging bag is one.

(2) Electromagnetic Shielding - Flame Retardant Packaging Materials

In practical applications, flame retardant requirements are often required when the electromagnetic shielding performance is required, and fire-retardant polymer materials or flame retardants in common plastics are generally used to meet the requirements. The United States has developed a flexible electromagnetic shielding mesh material, which can emit a self-extinguishing gas to prevent the combustion from proceeding when it is burned. A kind of copper net type electromagnetic shielding composite plastic developed in Guangzhou, China has reached the ULV-O level.

(3) Easy slip - anti-static - high barrier packaging material

Plastic packaging film occupies a very important position in packaging materials. For anti-static composite packaging films, the deterioration of slidability in secondary processing often brings many troubles in production such as snaking, scratches, and the like. To this end, Japan developed a slip-resisting-anti-static-high barrier three-function packaging material, which is coated with a special layer of FB on the OPP film to give its function, its surface resistivity is 1010Ω · cm, dynamic friction The coefficient is 0.3, and the oxygen permeability is less than 1 ml/m2·24h.

(4) EMR/RFR/MWR protective materials

The topic of the three defense materials, due to the multiband bandwidth of the band, the required dual conductivity performance is naturally higher than the EMI shielding material. The United States recently introduced a flexible plastic material with a high content of copper powder plus a cationic antistatic agent and a non-ionic antistatic agent to increase the magnetic conductivity and electrical conductivity, and can be effectively used to protect electromagnetic radiation/radio frequency radiation/microwave radiation.

The above only listed several examples of multifunctional packaging materials. With the development of packaging science and technology and the increasing demand for functional materials for packaging products, the prospects for the development of dual-function and multi-functional packaging materials are good.

Functional polymer materials are a new area developed in the 1970s and are now in a good period of time. According to the prediction of Japan Industrial Structure Research Association, by 2005, the sales of functional polymer materials in the world will reach 300 billion yen, which will increase at an annual growth rate of 10%.

According to data reports, there are still many functional packaging materials that have been available or are about to come out. By 2010, functional packaging materials will be more developed and improved, especially in protecting the earth and protecting human living environment, the existing packaging materials will be greatly improved.

Worldwide, EMI shielding materials have been rapidly developed in recent decades. The EMI shielding materials mainly include the following types: (1) metal foil materials; (2) surface conductive type shielding materials; (3) filled-type shielding materials; (4) shielding coatings and the like.

3.1 Metal foil

Prevent electromagnetic interference, application of metal foil