How to remove the odor of polypropylene plastic

A simple way to reduce the pungent smell in plastic processing. Plastic products will give off unpleasant smells. In order to overcome this problem and meet the needs of customers, plastic resin manufacturers and processors have been working hard to reduce the emission level of these odors for a long time. The typical methods to solve this problem are: replacing those unpleasant additives with low odor substitutes, reducing the amount of residual monomers in plastics, adding gas adsorbents and antibacterial agents in plastics to prevent unpleasant odors caused by bacteria and fungi, and reducing residual odors through solvent extraction and exhaust during the treatment of recycled plastics. Many compounds in plastics have unpleasant smells, including amines, phenols, mercaptans, peroxides, benzene, aldehydes and ketones, as well as some plasticizers and flame retardants. Solvents used in plastic processing also release strong chemical odor. This paper briefly outlines the measures to reduce the odor of plastics. 1. Changing the catalyst tertiary amine used in the production of additive polyurethane foam will often bring strong odor, and at the same time, it will also fog on the interior windows of automobiles. The solution to this problem is to find substitutes for these amines. One of the measures is to use polyhydroxy compounds, which are not only components of polyurethane molecular chain, but also have catalytic activity. Some polyhydroxy compounds can even replace half of the tertiary amine catalyst, so the smell of the product is much lighter. Phenolic stabilizers used in PVC extrusion or calendering are often replaced by zinc stabilizers with low odor. Thermal stabilizer tin octoate is also commonly used in automobile PVC products because of its low odor and low atomization characteristics. Oils extracted from plants, such as erucic acid and oleic acid, smell much less than amine lubricants made from animal oils (used for polyolefin and styrene food packaging materials). 2. Using purer resin in many plastics, especially in plastics such as PVC, styrene, polyvinyl acetate and acrylate, the residual monomer will produce unpleasant smell. These odors can be eliminated by using resin with little residual monomer. If the resin itself is tasteless, it will also have a good effect. For example, DuPont has developed a new grade of acetal polymer, which releases very little odor during injection processing. 3. Adding adsorbent If a small amount of zeolite (aluminosilicate adsorbent) is filled in the polymer, the odor of the material can be removed. Zeolite has a large number of crystal holes, which can capture those odorous gas molecules. Molecular adsorbents have been successfully applied to polyolefin extrusion tubes, injection and extrusion blow molding containers, isolation packaging materials, extrusion packaging materials and sealing polymers. Molecular adsorption powder can also be added to the plastic as a hygroscopic agent to remove water vapor, which will also help plastic products produce odor. 4. Adding antibacterial agents to plastics can not only reduce the odor it emits, but also delay the aging, discoloration and brittleness of the product surface. The most commonly used antibacterial agents are 10, 10'- oxydiphenol (OBPA), triclosan, isothiazolinone (OIT) and pyrithione. Organometallic compounds containing tin and silver are sometimes used as antibacterial agents. The multi-purpose resin of antibacterial agent is typically applied to PP food service utensils, handles, PP musical instrument blowholes (or microphones and brackets), containers, PA handles, PE humidity regulator parts, PE chopping boards, PE cable linings, PE blow molding, electrostatic dissipation (ESD) sewage floating balls, and PMMA transparent food storage cabinets TES (thermoplastic styrene elastomer). TPO animal ear tag (laser marking is possible) 5. Another way to remove odor by using desorption method is to put plastics into odor adsorbents such as activated carbon and high surface area silicate. Vacuum treatment of the environment can accelerate this desorption process. Treating plastic particles with special cleaners also helps to remove odors. Generally speaking, these detergents are aqueous or alkaline solutions containing surfactants. These cleaners can effectively remove vinyl chloride monomer, styrene, acrylate, acrylic monomer and unsaturated hydrocarbon. 6. Adding fragrances to plastics can't eliminate unpleasant smells, but it can mask them. In many cases, this is enough to achieve the goal. The method can be used for thermoplastic elastomers of polyethylene, polypropylene and polyolefin, and the processing methods include injection molding, extrusion molding or blow molding. The retention time of fragrance is not necessarily equal to the life of the molded part, but depends on its aggregation degree, volume-surface ratio, whether it is heated or damp, whether the molded part is tightly sealed with air and other factors. Aromatics are generally used in toys, daily commodities, cosmetic containers, household appliances and gardening equipment. 7. Recycling waste plastics often produces unpleasant smells. Most recycled plastics, such as HDPE, PP, PVC and PET, are washed with aqueous solution to remove pollutants. However, the odor adsorbed inside the plastic will still exist. Organic solvent extraction is helpful to remove odor-producing compounds. The latest solvent extraction method also uses supercritical carbon dioxide as solvent. This technology has been applied to HDPE and PET, which can remove the malodorous pollutants in oil containers, pesticide containers and other waste devices. The advantage of carbon dioxide extractant is that it will not bring the troublesome post-treatment problem of organic solvent. The deodorizing device is an integral part of the waste plastic particle extruder, which can also effectively remove some highly volatile compounds that will produce odor. 8. The odor scale of plastic odor is a subjective problem that varies from person to person, so it is very difficult to develop a system to measure odor. The first step to objectively confirm the smell is to let a group of people distinguish whether the smell they smell is pleasant or unpleasant. According to the reaction of the identification group, standard instrumental analysis methods such as meteorological chromatography and solid-state spectroscopy (GS/MS) are used to determine the grade of plastic volatiles. However, these early instrumental analysis systems need serious analysis and evaluation by experts in order to draw accurate conclusions. The latest plastic odor detector is a device called "electronic nose", which works by electronic probe lattice and pattern recognition technology. The instrument operator heats the sample and introduces the released volatiles into the probe lattice for detection. The obtained results are displayed in digital form, which easily corresponds to the conclusion of the appraisal group. According to specific requirements, the odor of volatiles can be divided into pleasant, neutral and unpleasant, or reported in the form of intensity and molecular aggregation. Conclusion In the highly competitive plastic market, pungent smell will greatly hinder sales, while neutral or pleasant smell will be welcomed by customers. Using deodorization technology may increase the cost of plastic products in the short term, but it will definitely have a good return in the long run. .