The characteristics of the pva film and bag
1 Environmental protection
PVA film products are green materials. The relevant departments have measured that the biological oxygen consumption (BOD) of PVA is much smaller than that of starch. After 5 days of biodegradation of Airworth PVA products by American Air Products, the measured BOD is less than 1% of the original total BOD. Biological tests have shown that PVA is neither toxic.
As far as the degradation mechanism is concerned, PVA material has two degradation properties of water and organism. It is first dissolved in water to form a gel solution which penetrates into the soil, which can increase the agglomeration, gas permeability and water retention of the soil, and is especially suitable for sand modification. The PVA material in the soil can be decomposed by bacteria in the soil and eventually degraded to CO2 and H2O.
2 Water solubility
The solvent of PVA is water, but the solubility to water is largely affected by the degree of polymerization, especially by the degree of alcoholysis. When the degree of alcoholysis is 88% or less, it is almost completely dissolved in normal temperature water at a normal temperature of 20 °C. As the degree of alcoholysis increases, the solubility decreases drastically, and the dissolution of fully alcoholized PVA in water is minimal.
The water solubility of the PVA film is related to the thickness of the film and the temperature of the water. The relevant data sheets are as follows:
Dissolved water temperature begins to dissolve time
(minutes) complete dissolution time
(minute)
Room temperature soluble film 25 ° C 0.5 15
Medium temperature soluble film 65 ° C 0.5 10
High-temperature melting film is completely insoluble under 40 °C, completely dissolved above 85 °C 0.5 10
Note: 1, film thickness: 20μm, 2, in turbulent water.
3 Strength and weather resistance
PVA film has good toughness, high tensile strength and tear strength. It has the best tensile strength, good weather resistance and long service life. The strength properties of various films are as follows:
PVA film PT film (cellophane) 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 rate (%) 150~400 15~25 50~600 200~600 5~25
4 Release and metal plating
The PVA film has low affinity for a highly hydrophobic plastic, and has good release (peeling) properties for various organic materials having a small polarity.
The PVA film can be plated with aluminum under a vacuum of 1.33 x 10 to 266 x 10 Pa, and the product is immersed in water at 30 ° C for 24 hours, and the plating layer is not peeled off.
5 Transparency and gloss
The transparency and gloss of the PVA film are superior to those of other films.
PVA film PT film (cellophane) PVC film PET film
Transmittance% 90.1 60.5 50.4 57.8
Reflectance % 81.5 60.5 79.5 22
6 moisture permeability
The moisture permeability of the PVA film is similar to that of cellophane. It is a film with extremely high moisture permeability. It does not produce fog droplets when packaging hot and wet items. The data measured in accordance with JIS-Z1503 are as follows:
PVA film PT film (cellophane) PVC film PET film
Moisture permeability 1500~2000 1300~2000 120~180 35~180
7 Barrier
The PVA film has excellent oxygen barrier properties under dry conditions, and its oxygen permeability coefficient is the lowest among various resin films.
A large number of hydroxyl groups (-OH) exist in the molecular chain of PVA. In a humid environment, these hydroxyl groups easily form hydrogen bonds with water molecules, resulting in a change in the structure of PVA aggregates, which greatly reduces the barrier properties of PVA. As the relative humidity increases, the amount of oxygen permeation increases significantly.
PVA film has strong permeability to moisture and ammonia, but has superior barrier properties to oxygen, nitrogen, hydrogen, helium, argon and carbon dioxide. The barrier rate of oxygen in normal pressure environment is about common. 1000 times of vinyl film and 300 times of polypropylene film. The PVA film can be used to maintain the composition of the packaged product and its own odor. The Salame method is used to test the permeability of different plastics:
Plastic variety Parmachor value Air permeability (cc.20μ/m2•24h•1atm) Salame test value Measured value
N2 O2 CO2
PVA 160 0.02 0.06 0.21 0.2
PVCD 97 0.6 3.6 12 2
PET 68 21 80 310 40
PVC 61 100 200 1000 300
HDPE 39 800 2000 12000 2500
PP 31 1600 5400 20000 3000
PS 27 2400 8000 26000
LDPE 26 3200 10000 36000 10000
8 Antistatic
Many plastic films have a strong chargeability, while PVA films have almost no static electricity. When the product is packaged using a PVA film, it does not cause plasticity reduction or electrostatic dusting due to static electricity.
PVA film PT film (cellophane) PVC film PE film PET film
Static voltage 1.2V 1.3V 40.5V 98.6V 120.6V
9 Printing performance
PVA film has excellent water color and ink printing property, which is an incomparable advantage of the existing plastic film which can only be printed by ink. It can be used for water transfer printing, such as glass, ceramics, electrical enclosure, automobile parts, etc. Color printing. At the same time, the PVA film has strong polarity and can be processed without EDM. It is also widely used in the special printing industry, such as water transfer film substrate.
10 Heat sealability
The water-soluble packaging film has good heat-sealing property and is suitable for resistance heat sealing and high-frequency heat sealing. The heat sealing strength is related to temperature, humidity, pressure, time and the like, and is generally greater than 200 g/cm 2 .
11 Oil resistance and solvent resistance
PVA film has excellent oil resistance (vegetable oil, animal oil, mineral oil), organic solvent resistance and carbohydrates. However, strong bases, strong acids, chlorine radicals and other substances that can react with PVA (such as borax, boric acid, certain dyes, etc.) are not suitable for PVA film packaging.
A grease absorption scale
Oil test conditions PVA PET OPP PE OPS
Steam oil 20 ° C, 10 days 0 1.1 1.1 4.7
Diesel oil 40 ° C, 30 days 0 3.2 5.2 3.5 2.8
Salad oil 40 ° C, 30 days 0 1.8 3.1 4.6 1.5
B Solvent absorption scale
Solvent PVA EVAL CPP OPP PET
Toluene 3 120 3740 6120 670
Isopropyl alcohol 80 3440 600 430 1070
Ethyl acetate 10 240 2950 3700 1520
Methyl ethyl ketone 7 500 2070 2790 1560
Total quantity 100 4300 9360 13040 4820
12 Protecting fragrance and preventing sublimation
The PVA film has excellent fragrance retention and excellent performance in preventing sublimation of the package. PVA film packaging not only maintains the fragrance of the package well, but also prevents the package from being affected by external odor.
Fragrance test table
Contents Rose essence (1ml) Lemon essence (1ml) Apple flavor (1ml) Wind oil (1ml) Soy sauce (2ml) Tea (3g) Cigarette (3g)
PP
(25μm) 1 hour 1 hour 1 hour 1 hour 3 hours 1 day 1 day
PP/PE (65μm) 3 hours 1 day 1 day 1 hour 1 week 1 week 1 week
PVA/PP (32μm) 1 week 1 week 1 week 2 days 4 weeks
Above 4 weeks
Above 4 weeks
the above
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