It works! Reasons for the peculiar smell of plastics and seven solutions

Plastic products emit unpleasant odors during processing. In order to overcome this problem, everyone has long been working to reduce these odors. In addition, many friends will add a certain proportion of recycled materials to the new materials to make the pellets taste heavier during production. This is a common problem in production. Now we provide seven solutions.

Reasons for the peculiar smell of plastics: the materials are relatively miscellaneous, the materials have been processed and degraded many times, the decomposition of small molecular materials in the materials, and sometimes the materials with mixed water play a strong role in accelerating degradation.

Additives or recycled materials are added to plastic products, so that the plastic products carry ethylene, hydrogen sulfide, sulfur dioxide, amine, ammonia, or other odors. Part of the odor is released after the product is stored for a period of time; sometimes it is lurking in the plastic product, and these harmful gases are released during the secondary processing, which constitutes the peculiar smell of the plastic. The typical way to solve the odor is to add gas adsorbent and antibacterial agent to the plastic to prevent the unpleasant odor caused by the action of bacteria and fungi. Solvent extraction and exhaust can also be used to reduce residual odors.

Plastic odor treatment

1. Use additives correctly

    The tertiary amine catalyst used in the production process of polyurethane foam often brings strong odor and also fogs up on the interior windows of cars. The solution to this problem is to find substitutes for these amines. If a polyhydroxy compound is used, the polyhydroxy compound is not only a component of the polyurethane molecular chain, but also has catalytic activity.

Phenolic stabilizers used in the process of PVC extrusion or calendering are often replaced by low-odor zinc stabilizers. The heat stabilizer tin octoate is also commonly used in automotive PVC products due to its low odor and low fogging characteristics. Plant-derived oils such as erucic acid and oleic acid have much less odor than amine lubricants made from animal-derived oils (used in polyolefin and styrene food packaging materials).

2. Treatment of recycled materials

     Organic solvent extraction methods help remove odor-producing compounds. The latest solvent extraction method also uses supercritical carbon dioxide as a 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 cause troublesome post-processing problems with organic solvents.

The odor removal device is an integral part of the waste plastic pellet extruder. It can also effectively remove some strong volatile compounds that produce odor.

3. Use purer resin

       In many plastics, especially in plastics such as polyvinyl chloride, styrene, polyethyl acetate and acrylic esters, residual trace monomers can produce unpleasant odors. Those odors can be eliminated by using resins with a small amount of residual monomers.

4. Add adsorbent

     If a small amount of zeolite (an aluminosilicate adsorbent) is filled in the polymer, it can play a role in removing the odor of the material. Zeolite has a large number of crystalline voids, which can capture small gas molecules with odor.

Molecular adsorbents have been successfully applied to polyolefin extrusion pipes, injection and extrusion blow molding containers, isolation packaging materials, extrusion molding outer packaging materials and sealing polymers. Molecular adsorption powder can also be added to plastic as a moisture absorbent to remove water vapor, which will also help plastic products produce odor.

5. Use antibacterial agents

     Adding antibacterial agents to plastics can not only reduce the odor, but also delay the surface aging, discoloration and brittleness of the products. The most commonly used antibacterial agents are 10,10'-oxobisphenoxa (OBPA), trioxyhydroxydiphenyl ether (Triclosan), isothiazolinone (OIT), and pyrithione (Pyrithione). Organometallic compounds containing tin and silver are sometimes used as antibacterial agents.

6. Use desorption method

    Another way to deodorize is to place the plastic in an odor adsorbent such as activated carbon and high surface area silicate. The vacuum treatment environment can speed up the desorption process. Treating plastic particles with special detergent solutions can also help remove odors. Generally speaking, these cleaning agents are aqueous or alkaline solutions containing surfactants. These cleaners can effectively remove vinyl chloride monomers, styrene, acrylic acid esters, acrylic acid monomers and unsaturated hydrocarbons.

7. Add fragrance

     Adding fragrances to plastics cannot eliminate unpleasant odors, but it can cover these odors, which is sufficient in many cases. The 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 the fragrance is not necessarily the same as the life of the molded part. Its retention time is determined by its degree of aggregation, volume-to-surface area ratio, whether it is exposed to heat or humidity, and whether the molded part is tightly insulated and air-packed. Fragrances are generally used in toys, daily commodities, cosmetic containers, household appliances and gardening equipment.

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