Application of radiation processing technology
Writer: Sterilization Time: 2020-10-23 Browse: 822 ℃
Application of radiation processing technology
Radiation treatment wire and cable
The properties of heat resistance, oil resistance, crack resistance, insulation, chemical corrosion resistance and mechanical strength of wires and cables made of polyethylene and polyvinyl chloride are significantly improved after radiation treatment.
wire and cable are widely used in electrical machinery, electronic computer, automobile and aircraft products. 90% of communication wires in the United States are treated by radiation. There are also clear provisions in the United States that 100% of aircraft cables must be produced by radiation crosslinking.
The traditional methods of food preservation are cold storage, high temperature sterilization and medicament fumigation. However, radiation treatment uses y-ray, X-ray or electron beam to irradiate food, causing a series of chemical and biological reactions in food, so as to inhibit sprouting, insecticidal sterilization and delay ripening.
Irradiated food is safe
For a long time, the development of food irradiation has been affected by people's long-term fear and concern about nuclear radiation. In fact, the food treated by irradiation completely meets the health requirements in terms of nutritional quality, microbiology and toxicology. It does not carry radioactivity and does not cause harm to human health, In November 1980, a joint expert committee on the health of irradiated food, composed of the international food and Agriculture Organization (FAO), the World Health Organization (who) and the International Atomic Energy Agency (IAEA), published a global standard: no food will be exposed to toxic effects up to the total average dose of 10kGy, It will not cause special nutritional or microbiological problems. Therefore, it is unnecessary to carry out toxicological test for this kind of irradiated food, which paves the way for the practicability and commercialization of irradiated food.
Characteristics of radiation processed food
Radiation processing food has some obvious advantages: (1) it is safe and pollution-free; (2) it will not damage the quality of food, and can maintain its original color, aroma, taste and appearance quality; (3) because the irradiated food can be stored at room temperature, the radiation method is more energy-saving; (4) the food irradiation process is mature and simple, and the operation is convenient, It can realize mechanization, automation and continuous operation; it has strong ray penetration and can handle various forms of food.
Radiation sterilization can be roughly divided into two categories: selective radiation sterilization and targeted radiation sterilization. The dose of selective radiation sterilization is generally less than 1kGy or 5kGy, which is mainly used for the transportation and storage of aquatic products. After radiation treatment, it can effectively inhibit the growth and reproduction of pathogenic microorganisms, The dose of radiation sterilization is between 1 and 10 kGy. The main objects of radiation sterilization are fresh meat and aquatic products, and the main targets of killing are Salmonella. The sensitivity of Salmonella to radiation is much greater than that of heat. Therefore, radiation method is very effective for frozen chicken treatment, It can be stored at - 30 ℃ for two years without obvious changes in color and flavor.
Radiation disinfection is actually a process of sterilization. After being exposed to radiation, microorganisms will die due to the biological effects of radiation. The degree of damage to microorganisms by radiation is directly related to the radiation dose. Some research results show that the survival rate of microorganisms is directly proportional to the radiation dose, that is, the higher the radiation dose is, D10 is defined as the dose required to reduce the number of bacteria in the sample to 1 / 10 of the original number. The smaller the value of d10, the more sensitive the bacteria are to radiation and the more likely they are to be killed
Radiation disinfection radiation source
There are two kinds of radiation sources used in radiation disinfection: Co60 γ radiation source and electron accelerator. As the penetration of gamma rays is very strong, the CO γ radiation source is more suitable for handling large-size packaged objects. In the process of irradiation, the method of "double-sided irradiation" is often used, that is, making the two sides of the irradiated object face the radiation source alternately, Now electron accelerators have made great progress, and the cost of electron beam radiation has been greatly reduced, which makes the cost of disinfection treatment with accelerator cheaper than that of gamma radiation source. In addition, the processing efficiency of electron accelerator is higher than that of Co60 gamma radiation source, The speed of electron accelerator is a thousand times faster than that of electron beam. There is a problem with electron beam disinfection, that is, the penetration ability of electron beam is relatively weak, and it is suitable for dealing with small objects. This will not limit the development of electron accelerator in the field of radiation disinfection, because the density of most irradiated objects is relatively low, about 0.15-0.2g/cm3, An electron beam with an energy of 5-10 MeV can be used to process such devices.
Considering comprehensively, the accelerator has certain advantages in terms of economy, safety and application range. The application of accelerator in radiation disinfection will have a good prospect in the future.
Treatment of wastewater by radiation
The treatment of wastewater by radiation can remove the pollutants that can not be removed by other methods, such as toxic cyanide, sodium alkyl sulfonate detergent, refractory dyes and organic mercury, etc. the principle of radiation treatment of wastewater is to decompose the pollutants, so as to achieve the purpose of removal.
Heat shrinkable material
Including heat shrinkable tube, sheet, strip and film. After irradiation, the product is crosslinked into a network, and then artificially expanded to a certain multiple, and then heated to the melting point of the polymer after setting, the expanded product can automatically shrink and try to recover to its original state. It is widely used in the connection and coating of wires, cables and pipes to replace the traditional lead, tape winding and epoxy resin pouring winding
Radiation vulcanization of rubber
medical gloves are prepared by radiation vulcanization of natural rubber, which has the advantages of non-toxic and less environmental pollution during waste incineration; radiation crosslinking of silicone rubber can prepare high-quality artificial organs
the structure of the network is polymerized by polymer, foaming agent and some additives. The network structure is heated by the irradiation polymerization, and the foaming agent is decomposed. The generated gas makes the reticulated body foam like structure, characterized by closed cell foam, low water absorbency, non-toxic, odorless, aging resistance, corrosion and shock absorption. Temperature and life saving materials
Irradiation preservation of food
It mainly inhibited the germination of vegetables and the ripening of fruits. The DNA and RNA in the cells were damaged by radiation, and the cells in the plant growth point could not divide. Radiation interferes with the synthesis of ATP, which is the reduction of cell synthesis, inhibition of plant germination, leading to the death of microorganisms and the damage of genetic materials.
The factors affecting food irradiation are as follows
The water and state of the irradiated food, the dose used, the temperature of the irradiated food, the presence or absence of ambient oxygen
Radiation breeding is a kind of mutation breeding. It uses ionizing radiation to treat the seeds, pollens or plants of crops to induce the genetic material to change, resulting in the variation related to transmission, and then through selection and cultivation, the favorable variation can be inherited to achieve the purpose of improving crop varieties or producing new varieties.
Curing of coatings
The coating is cured by radiation polymerization and crosslinking, which is called radiation curing of coating. Many products, such as metal, paper, ceramics and wood products, can be treated by radiation. Radiation curing usually uses ultraviolet or electron beam as energy to irradiate the liquid coating composed of 100% active ingredients, The so-called 100% active component refers to that the coating is composed of unsaturated oligomer and vinyl monomer solution, which is caused by radiation source. 6 compared with the traditional thermal curing method, radiation curing can save energy and produce high yield, The product is of high quality and can reduce environmental pollution. These advantages are incomparable with thermal curing method. However, it has some shortcomings, such as high cost, limited application range, etc. However, the research work of radiation curing is very active, and its development prospect is more optimistic.
Radiation processing technology has been developed for decades and has a certain scale. Radiation processing technology has been widely used in industry, agriculture, medicine and environment, showing unique advantages. With the continuous development of radiation processing technology, it will play an increasingly important role in the national economy, Create more significant economic and social benefits.