In order to overcome the unpleasant smell of plastic products in the process of processing, people have been working hard to reduce these odors for a long time. In addition, many friends will add a certain proportion of recycled materials to the new materials, which will make the granulation production taste heavier. This is a common problem in production. Now we provide seven solutions.
The reasons for the peculiar smell of plastics are as follows: the materials are miscellaneous, the materials are processed and degraded for many times, the small and medium molecular materials are decomposed, and sometimes the water and some materials play a strong role in accelerating the degradation.
Because the additives or recycled materials are added to the plastic products, the odor of ethylene, hydrogen sulfide, sulfur dioxide, amine, ammonia or other odors are carried in the plastic products. Part of the odor is released after the products are stored for a period of time; sometimes it lurks in the plastic products, and these harmful gases are released during the secondary processing, forming the odor of plastic. The typical way to solve the odor is to add gas adsorbent and antibacterial agent into the plastic to prevent the bad smell caused by bacteria and fungi. The residual odor can also be reduced by solvent extraction and exhaust.
Odor treatment of plastics
1. Correct use of additives
The TERT amines used in the production of polyurethane foam often bring strong odor and fog on the car windows. The solution to this problem is to find alternatives to these amines. If polyhydroxy compounds are used, polyhydroxy compounds are not only components of polyurethane molecular chain, but also have catalytic activity.
Phenol stabilizers used in PVC extrusion or calendering are often replaced by zinc stabilizers with low odor. Tin octanoate, a heat stabilizer, is also commonly used in automotive PVC products because of its low odor and low atomization. Vegetable oils such as erucic acid and oleic acid have much less odor than the amine lubricants (used for polyolefin and styrene food packaging materials) made from animal oils.
2. Treatment of recycled materials
Organic solvent extraction method is helpful to remove odor compounds. The latest solvent extraction method also uses supercritical carbon dioxide as solvent. This technology has been applied to HDPE and pet. It can remove odorous pollutants from oil containers, pesticide containers and other waste devices. The advantage of carbon dioxide extractant is that it will not bring the trouble of post-treatment of organic solvent.
Odor removal device is an integral part of waste plastic particle extruder. It can also effectively remove some strong volatile compounds that will produce odor.
3. More pure resin is used
In many plastics, especially in polyvinyl chloride, styrene, poly (ethyl acetate) and acrylate, the residual trace monomers will produce unpleasant smell. Those odors can be eliminated by using resin with little residual monomer.
4. Add adsorbent
If a small amount of zeolite (an aluminosilicate adsorbent) is filled in the polymer, the material odor can be removed. Zeolites have a large number of crystalline cavities, which can capture small molecules of odorous gases.
Molecular adsorbents have been successfully used in polyolefin extrusion pipes, injection and extrusion blow molding containers, isolation packaging materials, extrusion packaging materials and sealing polymers. Molecular adsorption powder can also be added to plastics as a moisture absorbent to remove water vapor, which can also help plastic products produce odor.
5. Antibacterial agents were used
Adding antibacterial agents into plastics can not only reduce the odor, but also delay the surface aging, discoloration and embrittlement of products. The most commonly used antimicrobial agents are 10,10 '- oxydiphenoxapine (OBPA), triclosan, OIT and pyrothione. Organometallic compounds containing tin and silver are sometimes used as antimicrobial agents.
6. Using desorption method
Another method of deodorization is to put the plastic in the odor adsorbent such as activated carbon and silicate with high surface area. Vacuum treatment can accelerate the process of deodorization. Treating plastic particles with a special detergent solution can also help remove odors. Generally speaking, these cleaners are aqueous or alkaline solutions containing surfactants. These cleaners can effectively remove vinyl chloride monomer, styrene, acrylate, acrylic monomer and unsaturated hydrocarbon.
7. Add aromatics
Adding aromatics to plastics doesn't eliminate bad odors, but it can mask them, which is enough in many cases. This method can be applied to polyethylene, polypropylene and polyolefin thermoplastic elastomers. The processing methods include injection molding, extrusion or blow molding.
The retention time of aromatics is not necessarily equal to the service life of molded parts. Its retention time is determined by the degree of aggregation, volume surface area ratio, whether it is exposed to heat or humidity, and whether the molded parts are tightly insulated from air. Aromatics are commonly used in toys, household goods, cosmetics containers, household appliances and gardening equipment.
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