Application of nanotechnology in pharmaceutical packaging materials
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In the aspect of pharmaceutical packaging, in order to have high impact strength, softness, transparency, etc., it is necessary to select plastic materials, and the following is an introduction to plastic materials.
▼Plastic products are printed
The nature of plastics is mainly determined by the size and shape of the constituent molecules. Most of the plastics are monomers in the first few stages of manufacture, ie consisting of small unit molecules, but in the role of heat and pressure and chemical catalysts. These small molecules combine into complex molecules to become solid or semi-solid structures. The characteristics of plastics can be listed as follows:
1. Can resist chemical corrosion.
2. It is shiny and partly transparent or translucent.
3. Most plastics are good insulators.
4. Light weight, but very strong, even replace metal.
5. It can be mass-produced, easy to process, and cheap.
6. Wide range of uses, multi-purpose and pleasing colors.
7. The shape is stable and the electrical properties are good.
8. It is flexible, easy to color, and partially resistant to high temperatures.
Because of the above-mentioned advantages of plastics, new plastics are constantly being researched and developed, and their various properties are better, such as engineering plastics or polymer plastics.
A high molecular polymer is a high molecular weight compound containing a covalent bond as a binding atom or a binding force between molecules. Usually a molecular weight of more than 1000 can be called a polymer. Natural rubber, protein, cellulose, starch, asbestos and the like are all high-molecular substances in nature.
Polymer is composed of monomers, that is to say, the polymer can be said to be a monomer bond. The structure of the polymer is usually used to describe the structure of the polymer. The structural units have different arrangements and connections. The method, for example, a linear polymer, wherein the structural unit is arranged on the chain, X-(M)nY, where M is a structural unit, ie, a monomer, and n is a degree of polymerization (degree of Polymerization), referred to as dp. When n is 2, it is called dimers. When n is 3, it is called trimers. When n is 4, it is called tetramers, and the number of n can reach as many as 10 million. The structural unit M is bounded by X and Y at both ends, and X and Y may be the same or different. Any polymer containing the same repeating unit is called a homopolymer, such as polyethylene. Polymers containing two or more structural units, referred to as copolymers. The polymerization type thereof includes addition polymerization, condensation polymerization, and combination polymerization.
▼ Commonly used plastic materials can include the following:
1. Polyethylene (Polyethlene)
Referred to as PE, it is the most extensive plastic. The main raw material for polyethylene is ethylene. Ethylene can be produced by thermal cracking of pentane: pentane is subjected to hot cracking to obtain ethane and propylene, and ethane can be dehydrogenated to obtain ethylene. The main products of polyethylene are medicine lids, tableware, kitchen utensils, toys and lighting parts.
Polyethylene can be divided into two types, low density polyethylene and high density polyethylene. Low density polyethylene, having a molecular weight of 50,000 to 300,000, a density of about 0.92 g/cm3 of high density ethylene, a molecular weight of up to 3 million, and a density of about 0.96 g/cm3.
2. Polypropylene (Polypropylene)
Polypropylene is produced in a similar manner to polyethylene. It is dispersed in a solvent with titanium trichloride and triethylaluminum, tributylaluminum or diethylaluminum chloride as a catalyzing agent. The reaction is carried out at 10 atm. Polypropylene, which is slurried, dissolved in ethanol, treated and then dried.
Polypropylene is harder than polyethylene, has a high softening point, and is brittle at low temperatures. The molecular weight is between 80,000 and 150,000, and the specific gravity is 0.90 to 0.91. Related products are silk fiber, traffic equipment, laboratory glass, dropper and injection molded products.
3. Polyvinyl chloride (pvc)
The Chinese name is polyvinyl chloride, and its material properties are high specific gravity and flame resistance. High transparency, good insulation and good printability. Different formulations have different characteristics and are widely used and inexpensive. When the processing temperature exceeds 190 ° C, it is prone to cracking, and HCL gas is released. The environmental impact is great. The molecular weight is between 60,000 and 150,000, and has good electrical and fire resistance. Related products are wire and cable sheaths, raincoats, curtains, and can be made by adding additives.
4. Pet polyethylene terephthalate (polyester)
The Chinese name is polyethylene terephthalate (polyester), and its material properties are low specific gravity, non-hygroscopic, good insulation, transparency, low cost, and low rigidity.
5. ABS (propylene laurel-butadiene-styrene tri-polymer)
The Chinese name is propylene celestial-butadiene-styrene tri-copolymer. The material properties are the ratio of the composition of each polymer. The ABS with different characteristics, excellent surface strength and heat resistance, good surface gloss, good surface spray and electroplating properties, hygroscopicity, and general finished products can be dyed. Need color. Its related printing products are suitcase face plates, ABS pipes, and home appliance casings.
6. PC (polycarbonate)
The Chinese name is polycarbonate, and its material properties are good transparency, high impact resistance at normal temperature, high temperature resistance, high rigidity, FDA grade, poor abrasion resistance, and poor chemical resistance. Its related printing products include transparent containers for safety glass and medical equipment.