Plastics reduce irritating odors

Plastics are an important raw material in the packaging industry. Plastics processing products emit an unpleasant odor. In order to overcome this problem, plastic resin processors have long been working to reduce the distribution of these odors. The solution is to replace those unpleasant additives with low odor substitutes; to reduce the amount of residual monomers in plastics; to add gas sorbents to plastics and add antibacterial agents to prevent the production of bacteria and fungi. Smells; there is also the ability to reduce the residual odor by solvent extraction and venting during the recycling of plastics.

Many compounds in plastics have unpleasant odors, including amines, phenols, thiols, peroxides, benzene, aldehydes, ketones, and some plasticizers and flame retardants. Solvents used in plastic processing also release a strong chemical odor. Reducing the plastic smell can take the following measures:

Change additives

The tertiary amines used in the production of polyurethane foams often give rise to strong odors. The solution to the problem is to find alternatives to these amines. One of the measures is the use of polyhydroxy compounds, which not only have a component of the polyurethane molecular chain but also have catalytic activity as well. Some polyols can even replace half of the tertiary amine catalysts, and the odor emitted from the resulting product is much weaker.

Phenolic stabilizers used in PVC extrusion or calendering processes are also often replaced by low-odor zinc stabilizers. Plant extract oils such as erucic acid and oleic acid are much less odor than amine lubricants made from animal extract oils (used in polyolefin and styrenic food packaging materials).

Use more pure resin

In many plastics, especially in plastics such as polyvinyl chloride, styrene, polyethyl acetate, and acrylates, residual traces of monomers can give offensive odors. Resins with little residual monomer can eliminate those odors.

If the use of odorless resin itself has a good effect. For example, DuPont has developed a new grade of acetal copolymer that releases a very slight odor during the injection process.

Add adsorbent

If the polymer is filled with a small amount of zeolite (an aluminosilicate adsorbent), it can remove the odor of the material. Zeolites have a large number of crystalline voids that can trap small gas molecules that have odors. Molecular adsorbents have been successfully used in polyolefin extrusion pipes, injection and extrusion blow containers, insulation packaging materials, extruded outer packaging materials and sealing polymers. Molecular adsorption powders can also be added to plastics as a moisture absorber to remove water vapor, which also contributes to the odor of plastic products.

Antibacterial agent

The addition of antibacterial agents to plastics can not only reduce the odor they emit, but also delay the aging, discoloration and embrittlement of the surface of the products. The most commonly used antibacterial agents are 10,10'-oxydiphenyloxime (OBPA), tricoronate (Triclosan), isothiazolinone (OIT), and Pyrithione. Organometallic compounds containing tin and silver are also sometimes used as antimicrobial agents. Antibacterial agents are used in a wide range of applications. Thermoplastic styrene elastomer TPO can be used for food packaging, medical facilities, and transparent food storage cabinets.

Using desorption method

Another method of deodorization is to place plastics in odor adsorbents such as activated carbon and high surface area silicates. Vacuum processing can speed up this desorption process.

Treatment of plastic granules with a special detergent solution can also help remove odors. In general, these cleaners are aqueous or alkaline solutions containing surfactants. These cleaners can effectively remove vinyl chloride monomer, styrene, acrylates, acrylic monomers and unsaturated hydrocarbons.

Add aromatics

Adding fragrances to plastics does not eliminate unpleasant odors, but it can mask these odors and in many cases it is sufficient to achieve the goal. This method can be applied to polyethylene, polypropylene, and polyolefin thermoplastic elastomers by injection molding, extrusion, or blow molding. Fragrance retention time is not necessarily equal to the life of the molded part. Its retention time is determined by the degree of aggregation, volumetric surface area ratio, exposure to heat or humidity, and whether the molded part is tightly isolated from the air. Fragrances are generally used in toys, household goods, cosmetics containers, household appliances, and gardening equipment.

Recycling product processing

Waste plastics often produce bad smells. Most recycled plastic packaging, such as HDPE, PP, PVC, and PET, will be washed with aqueous solutions to remove contaminants. However, the odor absorbed inside the plastic still remains. Organic solvent extraction methods help remove odor-causing compounds. The latest solvent extraction method also uses supercritical carbon dioxide as a solvent. This technology has been applied to HDPE and PET, which removes odorous contaminants from oil containers, pesticide containers, and other obsolete devices. The benefit of carbon dioxide extraction agents is that they do 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 of the strong volatile compounds that generate odors.

Plastic odor scale

Smell is a subjective problem that varies from person to person, so it is very difficult to develop a system for odor grading. The first step in objectively confirming the odor is to have a group of people identify whether the smell they smell is pleasant or unpleasant. According to the reaction of the discrimination team, standard instrument analysis methods such as gas chromatography and solid-state spectroscopy (GS/MS) were used to determine the grade of volatiles in plastics. However, these earlier instrumental analysis systems require careful analysis and evaluation by experts to arrive at an accurate conclusion.

The latest plastic odor detection device is a device known as an “electronic nose” that relies on electronic probe lattices and pattern recognition technology to work. The operator of the instrument heats the sample to guide the released volatiles into the probe lattice for detection. The results obtained are displayed in digital mode and are easily associated with the conclusions of the panel. According to specific requirements, the volatile odor can be classified as pleasant, neutral, unpleasant, or reported in terms of intensity and molecular aggregation.

In the highly competitive plastic packaging market, irritating odors will hinder sales, while neutral or pleasant odors will be welcomed by customers. The use of odor removal technology may increase the cost of the product in the short term, but in the long run there will be good returns.

Development of plasticizer substitutes in food packaging materials is imminent

Food safety is inseparable from the food packaging safety. Food packaging is known as a "special additive" for food. In current food packaging materials, plasticizers are often added in order to improve the performance of the packaging materials in certain aspects. However, at the same time as improving the performance of packaging materials, the harm of plasticizers to the human body can not be ignored.