English
Polyvinyl alcohol (PVA) film, with a density of 1.26-1,29g/cm3 and a refractive index of 1.52, emits blue white light after ultraviolet irradiation. This product has high water absorption and can dissolve when immersed in water. The moisture content of the fibers can reach 30% -50%, and the moisture content can also reach 4.5% in an environment of 65% RH and 25 ℃. It can pass through water vapor, but is difficult to pass through alcohol vapor, organic solvent vapor, inert gases, and hydrogen gas. The barrier properties of polyvinyl alcohol film are even better than those of vinyl chloride film. Polyvinyl alcohol
? Medium soluble thin film
? Insoluble film
? Special film
PVA is the only ethylene based polymer that can be used as a carbon source and energy source by bacteria. Under the action of bacteria and enzymes, it can degrade 75% in 46 days. It is a biodegradable polymer material that can be produced on a large scale through non petroleum routes. It is inexpensive and has outstanding oil resistance, solvent resistance, and gas barrier properties. It has unique advantages in food and drug packaging. The application of PVA is based on the solution method, which involves the preparation of thin film materials through casting. However, the solution processing and forming process requires dissolution and drying, which has disadvantages such as complex technology, high cost, and low yield. It is difficult to prepare thick walled and complex shaped products, and it is also impossible to co extrude and blow mold multi-layer composite films with other materials.
Polyvinyl alcohol (PVA) is a water-soluble polymer characterized by good density, high crystallinity, strong adhesion, flexible and smooth film, oil resistance, solvent resistance, wear resistance, good gas permeability, and water resistance after special treatment. It has a wide range of applications.
Polyvinyl alcohol is non-toxic, odorless, and harmless to the human body. It has good affinity with the natural environment, does not accumulate, and is pollution-free.
Polyvinyl alcohol film is a green and environmentally friendly functional material mainly composed of polyvinyl alcohol, with additives such as modifiers added, processed through special processes, and can be completely degraded by microorganisms in the soil. It can degrade into carbon dioxide and water in a short period of time, and has the effect of improving land.
The biggest advantage of polyvinyl alcohol film is its water solubility, but the biggest disadvantage is its poor water resistance. The reason for poor water resistance is due to the presence of hydrophilic hydroxyl groups (- OH) in its molecules. If the hydroxyl group can be appropriately blocked and attached with a water-resistant group, the water resistance of PVA film can be improved. PVA contains hydroxyl groups and can undergo all typical reactions of polyols. By selecting appropriate condensed polymers, it can moderately interact with the hydroxyl groups in PVA in a small amount, forming a strong three-dimensional structure that stabilizes the airtightness of PVA under wet conditions and improves its water resistance.
classification
Polyvinyl alcohol films can be classified into the following categories based on their solubility characteristics:
Room temperature dissolving film (NT type, also known as fast dissolving film, cold dissolving film): Dissolving temperature 25 ℃
Medium temperature soluble film (IT type, also known as medium temperature soluble film, hot melt film): dissolution temperature 65 ℃
High temperature soluble film (HT type, also known as insoluble film, resistant film): dissolution temperature 85 ℃
Special film: The formula and process can be designed according to specific applications to meet the requirements of special use.
manufacturing method
Process [1]
(1) Co polymerization modification involves introducing weaker units on the main chain or side groups through copolymerization or polymer reactions, reducing the intermolecular and intra molecular forces of PVA molecules and lowering the melting point; The Japanese company Keleli has synthesized thermoplastic PVA, which contains alpha olefin units and/or vinyl ether units with less than 4 carbon atoms, with a melting point of 160-230 ℃; The AXPVA copolymer film developed by Nippon Synthetic Chemical Company has excellent molding and processing properties, with a melting point of 200-210 ℃ and a molding and processing temperature of 210-230 ℃.
(2) Blending modification involves adding a large number of polymers that can form hydrogen bonds with hydroxyl groups in PVA, breaking down the intermolecular forces between PVA molecules, lowering the melting point, or increasing the thermal decomposition temperature, such as sugar derivatives and collagen hydrolysates. Nishino blended the sugar derivative Poly (GEMA) with PVA, significantly increasing its thermal decomposition temperature. When the addition amount reached 25wt%, the thermal decomposition temperature of the mixture reached 326 ℃. Novamont, a subsidiary of Montedison Group in Italy, has developed and produced the most successful PVA/starch composite material "MaterBi" grade, which is an interpenetrating network structure polymer plastic alloy composed of modified starch and modified PVA blends. It has excellent formability, secondary processability, mechanical properties, and biodegradability. The company has developed products such as extruded sheets, blown films, cast films, injection molded products, hollow containers, toys, etc.
(3) Post reaction modification, by chemically modifying the hydroxyl groups on the PVA molecular chain, introduces structural units that can reduce the regularity of PVA and improve its thermal stability, thereby improving the thermoplastic processing performance of PVA. Nishimura's research shows that alkyl boronic acid complexes can effectively reduce the melting temperature of PVA and increase the decomposition temperature, achieving melt spinning.
(4) Plasticization modification is a simple and efficient method that has been extensively studied both domestically and internationally. For example, companies such as Japan's Coca Cola Company, Japan Synthetic Chemical Company, DuPont, Sichuan Vinylon Factory, Sichuan University, Beijing University of Chemical Technology, South China University of Technology, and Beijing Gongshang University have used single or composite plasticizers such as water, inorganic salts, glycerol, polyols and their oligomers, caprolactam, and ethanolamines to lower the melting point of PVA and improve processing flowability.
performance
environmentally
PVA film products belong to green and environmentally friendly materials. The relevant departments have measured that the biological oxygen demand (BOD) of PVA is much lower than that of starch. After Air Products in the United States biodegraded Airvol's PVA products for 5 days, the measured BOD was less than 1% of the initial total BOD. Through biological experiments, it has been proven that PVA is non-toxic.
In terms of degradation mechanism, PVA material has two degradation properties: water and biological. Firstly, it dissolves in water to form a gel that infiltrates into the soil, which can increase soil cohesion, breathability, and water retention, making it particularly suitable for sand soil transformation. PVA materials in soil can be decomposed by bacteria in the soil and ultimately degraded into CO2 and H2O.
water-soluble
The solvent for PVA is water, but its solubility in water is largely influenced by the degree of polymerization, especially by the degree of alcoholysis. When the alcoholysis degree is below 88%, it is almost completely dissolved in room temperature water at 20 ℃. As the degree of alcoholysis increases, the solubility of PVA decreases significantly, and the complete alcoholysis of PVA dissolves very little in water.
The water solubility of PVA film is related to the thickness of the film and the temperature of the water. The relevant data table is as follows:
Dissolve water temperature and start dissolution time
(minutes) Complete dissolution time
(minutes)
Room temperature soluble film 25 ℃ 0.5 15
Medium temperature soluble film 65 ℃ 0.5 10
High temperature melting film is completely insoluble below 40 ℃ and completely dissolved above 85 ℃
Note: 1. Film thickness: 20 μ m, 2. In turbulent water.
Strength and weather resistance
PVA film has good toughness, high tensile strength, and tear resistance, ranking first among all types of films. It has superior biaxial tensile strength, good weather resistance, and long service life. The strength properties of various films are shown in the following table:
PVA film, PT film (glass paper), PE film, PP film, PVC film
Tensile strength (MPa) 44.1~63.7 54.9~131.4 17.3~19.1 45.1~53.9 20.6~17.6
Elongation (%) 150~400 15~25 50~600 200~600 5~25
Demoulding and metal plating
PVA film has low affinity for highly hydrophobic plastics and good delamination performance for various organic materials with low polarity.
PVA film can be coated with aluminum under a vacuum of 1.33 × 10~266 × 10 Pa, and the coating will not peel off when immersed in water at 30 ℃ for 24 hours.
Transparency and Glossiness
The transparency and glossiness of PVA film are superior to other films.
PVA film, PT film (glass paper), PVC film, PET film
Transmittance% 90.1 60.5 50.4 57.8
Reflectivity% 81.5 60.5 79.5 22
Moisture permeability
The moisture permeability of PVA film is similar to that of glass paper, and it is a film with extremely high moisture permeability that does not produce droplets when packaging hot or wet items. The data measured according to JIS-Z1503 is shown in the following table:
PVA film, PT film (glass paper), PVC film, PET film
Moisture transmission 1500~2000 1300~2000 120~180 35~180
barrier
PVA film has excellent oxygen barrier properties under dry conditions, and its oxygen permeability coefficient is the lowest among various resin films.
There are a large number of hydroxyl groups (- OH) on the molecular chain of PVA, which can easily form hydrogen bonds with water molecules in a humid environment, causing changes in the aggregated structure of PVA and greatly reducing its barrier properties. As the relative humidity increases, the oxygen permeation rate significantly increases.
PVA film has strong permeability to moisture and ammonia, but superior barrier properties to oxygen, nitrogen, hydrogen, helium, argon, and carbon dioxide. Under normal pressure, the barrier rate to oxygen is about 1000 times that of commonly used polyethylene film and 300 times that of polypropylene film. The use of PVA film can effectively maintain the composition and inherent odor of the packaged product.
Antistatic properties
Many plastic films have strong charges, while PVA films have almost no static electricity. During the process of packaging products with PVA film, there will be no reduction in plasticity or electrostatic dust accumulation caused by static electricity.
PVA film, PT film (glass paper), PVC film, PE film, PET film
Static voltage 1.2V 1.3V 40.5V 98.6V 120.6V
printing performance
PVA film has excellent water color and ink printability, which is an unparalleled advantage of existing plastic films that can only be printed with ink. It can be used for water transfer printing, such as color printing on irregular surfaces of glass, ceramics, electrical enclosures, automotive components, and so on. At the same time, PVA film has strong polarity and can be printed without electrical discharge treatment. It is widely used in the special printing industry, such as water transfer film substrates.
Heat sealing property
Water soluble packaging film has good heat sealing properties, suitable for resistance heat sealing and high-frequency heat sealing. The heat sealing strength is related to temperature, humidity, pressure, time and other conditions, generally greater than 200g/cm2.
Oil and solvent resistance
PVA film has excellent oil resistance (vegetable oil, animal oil, mineral oil), resistance to organic solvents and carbohydrates, etc. However, strong bases, strong acids, chlorine free radicals, and other substances that can react chemically with PVA (such as borax, boric acid, certain dyes, etc.) are not suitable for PVA film packaging.
A Oil Absorption Scale
Oil testing conditions PVA PET OPP PE OPS
Gasoline at 20 ℃, 10 days 0 1.1 1.1 4.7
Diesel fuel at 40 ℃, 30 days 0 3.2 5.2 3.5 2.8
Salad oil 40 ℃, 30 days 0 1.8 3.1 4.6 1.5
B solvent absorption scale
Solvent PVA EVAL CPP OPP PET
Fragrance retention and sublimation prevention
The fragrance retention and anti sublimation performance of PVA film are excellent. Using PVA film packaging not only maintains the fragrance of the packaging well, but also prevents the packaging from being affected by external odors.
Fragrance retention test form
Contents rose essence (1ml) lemon essence (1ml) apple essence (1ml) essential balm (1ml) soy sauce (2ml) tea (3g) cigarette (3g)
PP
(25 μ m) 1 hour 1 hour 1 hour 1 hour 3 hours 1 day 1 day
PP/PE (65 μ m) 3 hours 1 day 1 day 1 hour 1 week 1 week 1 week 1 week
PVA/PP (32 μ m) 1 week 1 week 1 week 2 days 4 weeks
The above 4 weeks
The above 4 weeks
application
Quick dissolving film
The inner packaging of pesticides and chemical products is lined with bags, which can prevent hands from touching pesticides and chemical products, and there are no residual pesticides in the plastic bags.
Cement additive packaging bag to avoid dust flying and endangering the environment.
Embroidery substrate, wig and other fabric carriers. Set off the carrier for easy cleaning.
Artificial marble release film, with a water-soluble film placed inside the mold, can quickly release the mold.
Water transfer printing can transfer onto curved surfaces after printing on the film.
Seed bags are used to package seeds at fixed intervals and bury them underground, saving valuable seeds and eliminating the busy process of intercropping.
The hospital washing packaging bag can be directly put into the washing machine without touching contaminated clothes.
disposable bag.
Medium soluble thin film
Food and cosmetics packaging bags, supermarket shopping bags.
Food packaging composite film, high-end textiles, plastic bag packaging, packaging cushioning air cushion.
Using glass paper type printing ink can achieve a beautiful printing effect.
Packaging of animal oil, vegetable oil, mineral oil, and packaging of oily food.
Used for packaging and sealing spices such as tea, coffee, curry powder, chili powder, and pepper powder.
It can be used for packaging small grains, oilseeds, dried seafood, precious Chinese medicinal materials, tobacco, etc. It can be used in combination with oxygen scavengers or vacuum pumps to ensure the quality and freshness of its anti mold, anti insect, and anti fading properties.
Anti static packaging for electronic products.
Insoluble film
The sealing of clothing, shoes and hats, leather and leather products, arts and crafts, documents, and archives, when used in conjunction with oxygen scavengers, has the effects of preventing mold, insect infestation, and oxidation discoloration.
Using glass paper type printing ink can achieve a beautiful printing effect.
Packaging of alcohols, ethers, ketones, esters, chemical raw materials, and intermediates.
Packaging for daily necessities, pharmaceuticals, and toys.
Used for sealing wireless components and complete machines, precision machinery, military equipment, radar, and ammunition, it has unique anti oxidation and anti-corrosion functions.
Optical instruments, lenses, and spare parts are sealed comprehensively to prevent mold and fogging.
Special film
Polyvinyl alcohol film can also be used in special fields such as polarization mode, automotive film, windshield interlayer, and sanitary material manufacturing.
