Ethylene-vinyl alcohol copolymer
EVOH, also known as ethylene-vinyl alcohol copolymer, is a thermoplastic material widely used in the food packaging industry due to its excellent barrier properties. EVOH excels in preventing the penetration of gases, liquids and aromas, making it the first choice for food packaging applications.
Chemistry and Properties
Polyvinyl alcohol (PVOH) has the lowest gas permeability of the available polymers. However, PVOH is water soluble and difficult to process. EVOH copolymers are prepared by first copolymerizing ethylene and vinyl acetate and then hydrolyzing the copolymer to obtain ethylene-vinyl alcohol. Therefore, a high degree of barrier effect is still retained, and there are significant improvements in moisture resistance and processing properties.
EVOH copolymers are highly crystalline in nature, and their properties are mainly determined by the relative concentrations of their comonomers. Generally speaking, as the ethylene content increases, the gas barrier properties decrease, the moisture resistance improves, and the resin is easier to process.
Oil Resistance
EVOH resins are also highly resistant to oils and organic solvents. After immersion in various solvents and oils at 68°F for one year, the percentage weight gain was: 0% for solvents such as cyclohexane, xylene, petroleum ether, benzene, and acetone, 2.3% for ethylene glycol, 12.2% for methanol, and 0.1% for salad oil.
Thermomechanical properties
EVOH resin has high mechanical strength, elasticity, surface hardness, wear resistance and weather resistance, and has strong antistatic properties. EVOH film has high gloss and low haze, and is highly transparent.
EVOH resin is the resin with the highest thermal stability among all commercial strong barrier resins. This property allows the waste generated during processing to be recycled and reused, and the recycled material contains up to 20% or more EVOH.
Advantages of EVOH
The notable features of EVOH are its excellent gas barrier properties and excellent processability. In addition, it has excellent transparency, gloss, mechanical strength, scalability, abrasion resistance, cold resistance and surface strength.
In the packaging field, EVOH is made into a composite film intermediate barrier, which is used for all rigid and flexible packaging. In the food industry, it is used for aseptic packaging, hot cans and peel bags, packaging of dairy products, meat, canned juice and condiments. In terms of non-food products, it is used to package solvents, pesticide chemicals, air conditioning structural parts, gasoline drum linings, electronic components, etc.
EVA recyclability
EVA (ethylene-vinyl acetate copolymer) is a thermoplastic with good softness, impact resistance, transparency and low temperature resistance. With the improvement of people’s environmental awareness, the recycling and reuse of EVA materials has also received increasing attention.
The answer is yes. EVA materials can be recycled through a specific recycling process. This process mainly includes steps such as collection, classification, cleaning, crushing and melting. After these treatments, the discarded EVA materials can be remade into new EVA products, thereby reducing resource consumption and environmental pollution.
In the recycling and reuse process, the first thing to do is to collect and classify the discarded EVA. The purpose of classification is to ensure the purity and quality of the recycled materials. Next, the stains and impurities on the surface of the EVA are removed through the cleaning process to ensure the performance during reuse.
