Antibacterial plastic refers to addition of antibacterial agents to plastic to make plastic itself antibacterial, which can kill or inhibit bacteria on plastic for a period of time. Compared with conventional chemical and physical methods, use of antibacterial plastics requires a long sterilization time, which is economical and convenient.
1. Types and mechanisms of antibacterial action
Plastic antibacterial agent is a new type of plastic additive. Adding a small amount of an antibacterial agent to plastic can give plastic long-term antibacterial and bactericidal properties. Antibacterial agents refer to substances that kill microorganisms and inhibit biological reproduction. It can be divided into three groups: organic, natural and inorganic.
(1) Inorganic antibacterial agent
Using antibacterial ability of silver, copper, zinc and other metals, plastic antibacterial agent immobilizes silver, copper, zinc and other metals (or their ions) on porous materials such as zeolite silica gel through physical adsorption or ion exchange. The antibacterial agent may be applied to surface of surface and then added to article to form an antibacterial material.
(2) Organic antibacterial agent
In antibacterial method of inhibiting production and reproduction of harmful bacteria and real (mold) bacteria in order to kill bacteria, research and development of various organic antibacterial agents is main focus. Organic antimicrobial agents are mainly used as fungicides, preservatives and antifungals.
When using organic antibacterial agents, in addition to attention to safety, there are problems such as poor heat resistance, easy hydrolysis and short service life. Therefore, development and development of organic antibacterial agents should fully consider antibacterial ability of antibacterial agents, material compatibility, drug stability, chemical thermal stability and UV resistance and other factors.
(3) Natural antibacterial agent
The use of natural raw materials as antibacterial agents, limited by safety and processing conditions, has not yet been able to achieve a large-scale market entry. Here we mainly introduce chitosan, a natural antibacterial agent. Chitosan is a water-soluble polyglucosamine obtained by removing acetylamino groups of chitin in concentrated alkali. Chitosan exhibits antibacterial properties against various bacteria and fungi. It is generally accepted that antibacterial mechanism of chitosan ends with a two-stage reaction: first, under acidic conditions, -HN3+ in chitosan molecule combines with aions dissociated from silicic acid, phosphate, etc. contained in bacterial cell. The free movement of bacteria is hindered, thereby hindering large-scale reproduction of bacteria: secondly, chitosan further decreases in molecular weight, penetrates into cells of microorganisms through cell wall, inhibits process of transformation of genetic factors from DNA into RNA and makes microorganisms completely incapable of reproduction.
In addition to using only inorganic antibacterial agents or organic antibacterial agents, inorganic-organic compound antibacterial agents have also begun to be used. This compound antibacterial agent combines advantages of two, not only has immediate effect and durability of organic antibacterial agents, but also has safety and discoloration resistance of inorganic antibacterial agents, so it is also direction for future development of antibacterial agents. .
2. The main varieties of general purpose antibacterial plastics
The antibacterial plastics used in production of antibacterial essentials are new functional polymeric materials with antibacterial or bactericidal action. These materials are based on a wide variety of plastics such as polyethylene, polypropylene, PVC and ABS and can be used to line household refrigerators, children's toys, drinking fountains, food packaging films, fibers, coatings, stationery, water pipes and etc., and have antibacterial functions. Frequently touched common items such as private telephones, computer keyboards, mice, elevator buttons and electrical switches. Plastic products made from antibacterial functional plastics and their alloys have a self-cleaning function, and when used in special cases in hospitals, number of disinfections can be reduced.
With exception of engineering antibacterial plastics that have antibacterial activity, most other antibacterial plastics are made by adding very small amounts of antibacterial agents. The added antibacterial functional plastics are easy to commercialize and are expected to be affordable to market.
(1) Antibacterial polyethylene
An antibacterial PE can confer apparent antibacterial activity to PE by adding an antibacterial masterbatch to introduce antibacterial components. With an increase in amount of antibacterial components, zone of inhibition increased significantly, respectively, antibacterial rate of test sample / bacterial solution, which was in contact for only 6 hours, had a gradual tendency to increase, and antibacterial rate exceeded 90%, which complied with Requirements of Requirements for antimicrobial materials. Also, appearance of PE has not changed.
(2) Antibacterial polypropylene
After introducing antibacterial components by adding an antibacterial masterbatch, polypropylene showed obvious antibacterial activity. With an increase in time of contact of sample with bacteria, rate of antibacterial action increased; when antibacterial components were same, antibacterial activity increased with increase in content of antibacterial component, and rate of antibacterial action changed significantly when contact time was short.
(3) Antibacterial PVC
After adding an antibacterial masterbatch to introduce antibacterial components, PVC may show obvious antibacterial activity. With an increase in amount of antibacterial masterbatch, antibacterial zone increased, and antibacterial rate after 6 hours of contact also showedand an upward trend, and both indicators exceeded 90%. In addition, antibacterial PVC retains its transparency.
(4) Antibacterial ABS
After introduction of antibacterial components into composition of ABS, ABS showed a clear antibacterial activity. Its antibacterial effect is very good, and antibacterial performance for 6 and 24 hours is over 98%. It can be seen that synergistic effect of antibacterial components of composite and effect of binding agent on improving antibacterial characteristics of ABS is very obvious.
(5) Long-term antibacterial activity of antibacterial plastic
The material retains its high antibacterial activity, or duration of antibacterial activity may characterize retention of its antibacterial activity. Obviously, if antibacterial activity of antibacterial plastics is significantly reduced in a short period of time, their consumer value will be significantly reduced.