Top Ten Inventions in Packaging in the 20th Century (II)

In addition, in order to expand the use of polypropylene, foreign countries are developing high-strength, high-rigidity high-crystallinity polypropylene (HCPP), which has obvious seven advantages, has the ability to compete with other plastics.
Irradiated PACKAGING
In 1896, the French physicist ATOINE HENRI BECQUEREL invented radioactivity. In 1898, MDANE CURIE discovered the radioactive elements of Radon and Radium, and in 1900 the French physicist PAUL VILLARD. Γ-rays were found. Shortly afterwards, there were applied disciplines such as radiation biology and radiation technology.
The use of γ-rays to irradiate packaged foods began in the 1970s and was originally used for the packaging, storage and preservation of meat products. This is based on scientific theory and practice. The obvious advantages of irradiating packaging are: 1. To extend the shelf life of food; 2. To adopt new packaging (such as polymer) and directly irradiate the packaging product; 3. To maintain the product characteristics; 4. No chemical residue (such as Preservatives); 5, reduce product losses; 6, automatic packaging production process; 7, save energy resources, protect the environment, the best green technology; 8, good technical and economic indicators. According to the International Atomic Energy Conference, the food storage energy-storage freezing method is 90 kW/h·ton, the pasteurization temperature is 230 kW/h·ton, and the heat sterilization is 300–700 kW/h·t, and the irradiation is complete. Sterilization was 6.3 kW/h·ton. Therefore, even in accordance with the requirements of the environmental protection standard ISO 14000, it is an authentic green packaging process.
For example, beef and pork packaged with a polymer material (radior-resistant) may be irradiated with gamma-rays at a dose of 0.6 MRAD and may be between 3 and 50. 2 months in D environment; selective sterilization with heat treatment combined with radiation can make the product at 5-20. The storage period under D is extended to 5 months.
Milk is the best food given to us by nature, but it is difficult to keep fresh; heat treatment (pasteurization, boiling) will cause some physical or chemical changes in the milk, the effect of treatment with electric field, ultraviolet light or chemical reagent Not Gui. Treatment with ionizing radiation (irradiation dose of 0.3-0.4 MRAD) can sterilize the milk.
In the 1990s, the scope of radiation packaging products has also been greatly expanded, such as dehydrated vegetables, dried fruits, convenience fabrics, cooked meat products, health drinks, Chinese and Western medicines, cosmetics, hygiene products, native products, food products, fresh fruits and vegetables, etc. The sources of radiation are gamma rays, X-rays, high-energy electron beams, etc. The radiation dose is strictly controlled within a safe range, leaving no radioactive material.
Due to the negative effect of the first atomic bomb in Hiroshima, radiation products have been in a state of “having a partial cover” for more than 30 years. In accordance with international regulations, China also formulated the “Administrative Measures for Irradiated Food” in China two years ago. Starting June 1, 1998, all irradiated foods (including imports) that were sold on the Chinese market should be packaged with The "IRRADIATED FOOD" green circle logo is affixed.
Irradiation can also be used for grafting, cross-linking modification of polymer materials, and also for disposal and regeneration of waste packaging materials.
Polyester (POLYESTER)
The polyester (PET) resin that was invented in 1847, researched in 1922, and completed in 1941 is the longest-researched and most widely used modern packaging industry, and has the most promising family members (referred to as polyesters), the most promising packaging materials, and Packaging products.
In 1847 the Swedish chemist BENZELIUS chemically synthesized the first polyester (PET) resin but no one cares. In 1922, DuPont chemists in the United States conducted polymer research with W. CARETHERS. Invented nylon in 1926, but did not complete the final study of PET. In 1941, the British chemists WHINFIELD and DICKSON used Carbirth's basis to make terephthalic acid and ethylene glycol to make ethylene terephthalate (PET) resin.
Thermoplastic polyester resins (broad refers to) are polymers composed of aromatic dicarboxylic acids and aliphatic aromatic diols. PET was the earliest discoverer because of its excellent performance as a packaging film developed rapidly. At that time, due to its poor formability, PBT (polybutylene terephthalate) with excellent processability in the 1960s was widely used; at the same time, PEN with excellent overall performance has been applied, but because of its high price Contained. Subsequently, PBN and PTT polyester resins were also introduced.
In 1987, PET resin began to realize commercial production and became one of the pillars of plastics. With the rapid development of PET in the second, PET film followed, and PET fiber shrank. Recently, the development rate of PET in the world has slowed down and prices have dropped. It is expected that the global PET demand growth rate will drop to about 4% after 2000.
In July 1995, American AMOCO Company first realized the commercial production of PEN raw material NDC (dimethyl naphthalene dicarboxylate), resulting in a significant drop in the price of PEN, replacing only the benzene ring of PET with naphthalene ring, so all aspects of performance are Better than PET. Especially in the heat resistance, chemical resistance, radiation resistance, gas barrier, UV resistance is also better than PET and so on.
Thanks to PEN (ethylene naphthalate (alcohol)...into the packaging field, it can also be used as a hot-fill container, pressure vessel (beer bottle) and other chemical engineering fields, and is known as the "star" of the world's packaging industry. , "New Polyester."
In June 1977, SHELL officially announced the listing of PTT (poly(trimethylene terephthalate)). Due to the development of a new process for the production of propylene glycol, the PTT price is comparable to that of PET, and the PTT also has the high performance of PET and the excellent molding processability of PBT, so it is widely used.
In addition, polyester resins include PBS (polybutylene succinate), BPSA (polybutylene adipate), and PES (ethylene poly(ethylene) succinate). Degradable plastics are new products for green packaging. (To be continued)

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