Plastic products can emit unpleasant odors during processing, and to overcome this problem, everyone has been working for a long time to reduce these odors. In addition, many friends will be mixed with a certain percentage of recycled material in the new material, pelletizing the production of heavier smell, which is a common problem in the production of the following to provide you with several solutions.
Reasons for odor after granulation
Material is more mixed
Material processing degradation many times
Decomposition of small molecules in the material
Sometimes water and some materials play a very strong role in accelerating the degradation
Due to the addition of additives or recycling materials in plastic products, plastic products with ethylene, hydrogen sulfide, sulfur dioxide, amines, ammonia odor or other odors. Some of the odors are released after a period of storage; sometimes they are latent in the plastic products, and the second processing of these harmful gases are released, constituting the odor of plastic. Typical solutions to odors include adding gas adsorbents to plastics and adding antimicrobial agents to prevent unpleasant odors due to the action of bacteria and fungi. Residual odors can also be reduced by solvent extraction and venting.
Odor treatment of plastics
1、The correct use of additives
The catalyst used in the production of polyurethane foam, tertiary amine, often brings a strong odor and also fogs up the interior windows of the car. The solution to this problem is to find alternatives to these amines. One of the measures is the use of polyhydroxy compounds, which are not only components of the polyurethane molecular chain, but also have catalytic activity.
Phenol stabilizers used in PVC extrusion or calendering processes are also often replaced by low-odor zinc stabilizers. The heat stabilizer tin octanoate is also commonly used in automotive PVC products due to its low odor and low atomization properties. Plant-derived oils such as erucic acid and oleic acid are much less odorous than amine lubricants made from animal-derived oils (used in polyolefin and styrene food packaging materials).
2、The treatment of recycled materials
Organic solvent extraction method helps to remove the odor producing compounds. One of the latest solvent extraction methods also uses supercritical carbon dioxide as a solvent, and this technology has been applied to HDPE and PET, which can remove odorous contaminants from oil containers, pesticide containers and other used devices. The benefit of carbon dioxide extractants is that they do not create the troublesome post-treatment problems of organic solvents.
The odor removal device is an integral part of the waste plastic pellet extruder, which can also effectively remove some strong volatile compounds that produce odor.
3. Use purer resins
In many plastics, especially in polyvinyl chloride, styrene, polyethyl acetate and acrylate, trace amounts of residual monomers can produce unpleasant odors. The use of monomer residues of a small amount of resin can eliminate those odors.
If the polymer is filled with a small amount of zeolite (an aluminosilicate adsorbent), it can play a role in removing the odor of the material. Zeolites have a large number of crystalline cavities that can trap small molecules of odorous gases.
Molecular adsorbents have been successfully used in polyolefin extruded tubing, injection and extrusion blow molded containers, barrier packaging materials, extruded overwrap materials, and sealing polymers. Molecular adsorbent powders can also be added to plastics as moisture absorbers to remove water vapor, which will also contribute to the odor of plastic products.
5、Adopt antimicrobial agent
Adding antimicrobial agents to plastics can not only reduce the odor they emit, but also delay the aging, discoloration and brittleness of the product surface. The most commonly used antimicrobial agents are 10,10'-oxo-bisphenoxyl arsenic (OBPA), trioxide hydroxy diphenyl ether (Triclosan), isothiazolinone (OIT), hydroxy pyridinethione (Pyrithione). Organometallic compounds containing tin and silver are sometimes used as antimicrobial agents.
6、Use desorption method
There is also a method of odor removal is to place the plastic in activated carbon and high surface area silicates and other odor adsorbents, vacuum treatment environment can make this desorption process faster. Treatment of plastic particles with special detergent solutions can also help remove odors. Generally these cleaners are aqueous or alkaline solutions containing surfactants. These cleaners can effectively remove vinyl chloride monomer, styrene, acrylate, acrylic monomer and unsaturated hydrocarbons.
7、Adding aromatic agents
Adding aromatics to plastics does not eliminate unpleasant odors, but it can mask them, and in many cases this is sufficient for the purpose. This method can be applied to polyethylene, polypropylene and polyolefin thermoplastic elastomers, and processing methods include injection molding, extrusion or blow molding.
The retention time of an aromatic does not necessarily equate to the life of the molded part, but is determined by the degree of aggregation, volume to surface area ratio, exposure to heat or humidity, and whether the molded part is tightly packaged with air barrier. Fragrances are generally used in toys, daily commodities, cosmetic containers, daily appliances and gardening equipment.
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