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POLYVINYL ALCOHOL
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1. Chemical Formula

 

 PVA(Polyvinyl Alcohol)

 

 

 

 

 

 

 

 

 

 

 

2. Applications

 

 

 

 

2-1 General Introduction

 

 

 

 

 

PVA(Polyvinyl Alcohol)-POLINOL, is a water-soluble resin is produced by the hydrolysis of polyvinylacetate which is made by the polymerization of vinyl acetate monomer.  It is classified into two main groups namely fully hydrolyzed and partially hydrolyzed grades.
 

 

 

 PVA(Polyvinyl Alcohol)-POLINOL, as an environmentally sensitive water soluble polymer, is widely used for textile warp sizing, adhesive, paper sizing agent, ceramic binder and also used in cosmetics, emulsion stabilizer, civil engineering, construction, pharmacy and electronic industries.
 

 

 

DC Chemical. Co. Ltd has been operating technical service and laboratories for customer-oriented product development and technology development.  We are also committed to improve the quality of our products and to make on time delivery and services to our customers.
 

 

 

PVA(Polyvinyl Alcohol)-POLINOL is divided into various kinds in accordance to the degree of hydrolysis and degree of polymerization. The nomenclature each grade is as follows;
 

 

 

 

 

 

 

2-2 PVA(Polyvinyl Alcohol) Grades and Specifications

 

 

 

 

Grade
Viscosity
(cps *1)
Degree of hydrolysis
(mol%)
PH(4% aqueous
solution)
Volatile
(max%)
ASH
(max%)
Fully hydrolyzed

 

F-05

5.5-6.5

98.0-99.5

5.0-7.0

5.0

0.7

F-05A

5.5-6.5

98.0-99.5

5.0-7.0

5.0

0.7

F-17

27.0-30.0

98.0-99.5

5.0-7.0

5.0

0.7

F-17A

27.0-30.0

98.0-99.5

5.0-7.0

5.0

0.7

Intermediate
hydrolyzed

M-17

28.0-32.0

94.5-96.5

5.0-7.0

5.0

0.7

M-17A

28.0-32.0

94.5-96.5

5.0-7.0

5.0

0.7

Partially
hydrolyzed

P-24

44.0-52.0

86.0-89.0

5.0-7.0

5.0

0.7

P-20

31.0-35.0

86.0-89.0

5.0-7.0

5.0

0.7

P-17

21.0-24.0

85.5-88.5

5.0-7.0

5.0

0.7

P-17A

21.0-24.0

85.5-88.5

5.0-7.0

5.0

0.7

P-05

5.0-5.6

85.5-87.5

5.0-7.0

5.0

0.7

P-05A

5.0-5.6

85.5-87.5

5.0-7.0

5.0

0.7

Special
Grades

CT-000*

17.5-20.5

84.5-87.5

5.0-7.0

5.0

0.7

SP-07

6.6-7.0

85.5-87.5

5.0-7.0

5.0

0.7

TK-97*

6.4-7.0

79.5-81.5

5.0-7.0

5.0

0.7

CL-05*

5.0-5.6

76.0-80.0

5.0-7.0

5.0

0.7

CL-O5A*

5.0-5.6

76.0-80.0

5.0-7.0

5.0

0.7

 

Brookfield viscometer, UL-Adapter, 4% aqueous solution at 20

 

 

105, 2hr dry

 

 

 

1)We have powder grades besides the listed above and following grades
   are commercially available. (P-05S,P-17S,F-17S,P-24S,CL-05S etc...)

 

 

2)The above *grades are carboxylated modified PVA (copolymer)

 

 

 

 

 

 

2-3 Grade Selection by utility

 

 

 

 

 

 

3. PVA(Polyvinyl Alcohol) Properties

 

 

 

 

3-1. General Properties

 

 

 

 

 

  Appearance

 White granule or powder

  Specific Gravity

 1.25 ~ 1.32

  Bulk density

  0.4 ~ 0.7

  pH

  5 ~ 7

 Glass transition temperature

  58(P Grade) 85 (F Grade)

 Melting Point

150190(P Grade), 210~230 (F Grade)

  Thermal stability

Gradual discoloration about 100; darkens rapidly above 160 ,        Gradual decomposition above 180as melting point is similar to decomposing temperature

  Oil resistance

Not soluble in animal, plant and grease oils

  Storage stability

Indefinite when protected from moisture

  Solvent resistance

Not soluble in organic solvent

  Acid & alkali resistance

Softened or soluble in acid and alkali

  Color(10%solution)

Less than APHA 20

  Particle size

More than 95% through 14120mesh screen

 

 

 

3-2. Effect of Degree of polymerization and Degree of hydrolysis

 

 

 

Degree of polymerization

 

 

 

 

 

Decrease
Increase

Increased solubility
Increased flexibility
Increased hydrophilic
Increase dissolving rate

Increase viscosity
Increase tensile strength
Increase adhesive strenth
Increase water resistance
Increase solvent resistance
Increase dispersing power

 

 

 

Degree of hydrolysis

 

 

 

 

 

Decrease
Increase

Increased solubility
Increased flexibility
Increased dispersing power
Increased hydrophilic
Increase adhesion to hydrophobic  surfaces

Increase tensile strength
Increase solvent resistance
Increase water resistance
Increase adhesion to hydrophilic
 surface

 

 

 

 

3-3. Other properties

 

 

3-3-1 Solubility

 

 

 

 

 

PVA(Polyvinyl Alcohol), as a water-soluble resin dissolves easily in water, but solubility depends on the degree of polymerization and degree of hydrolysis. The lower the degree of polymerization, the easier it dissolves in water. In general partially hydrolyzed grades are dissolved easily than fully hydrolyzed grades. Also, the dissolution rate of PVA(Polyvinyl Alcohol) depends on dissolution temperature.
The higher the temperature, the greater the rate of dissolution. Partially hydrolyzed grades dissolve at room temperature more easily than fully hydrolyzed grades which is not easily dissolved in room temperatures. Fully hydrolyzed grades has a different dissolution rate which varies according to the degree of crystallinity but partially hydrolyzed grades show little susceptibility to heat treatment condition.

 

 

 

 

 

 

 

 

 

Figure 1. Solubility (4wt%) vs. temperature
Dissolution condition: 2000rpm, 30min. PVA/water=4/96(wt/wt)% 

 

 

 

 

Figure 2. Solubility (10wt%) vs. temperature
 Dissolution condition: 2000rpm, 30min. PVA/water=10/90(wt/wt)% 

 

 

 

3-3-2 Refractive index of aqueous solution

 

 

 

Refractive index of PVA (Polyvinyl Alcohol)aqueous solution depends on concentration and temperature of aqueous solution

 

 

 

3-3-3 Viscosity of the aqueous solution

 

 

 

As degree of polymerization and degree of hydrolysis increase, the viscosity of the aqueous solution becomes higher and depended largely on the degree of polymerization rather than the degree of hydrolysis.

 

 

 

3-3-4 Viscosity Stability of the aqueous solution

 

 

 

 

 

The viscosity of PVA(Polyvinyl Alcohol) aqueous solution for fully hydrolyzed grades increases, according to storage time, and a gelation occurs. On the other hand, the gelation does not occur. because PVA(Polyvinyl Alcohol) aqueous solution of partially hydrolyzed grades has high viscosity stability, For fully hydrolyzed grades viscosity increase at a faster rate if the concentration becomes high and temperature decreases. The higher the degree of hydrolysis and degree of polymerization, the more likelihood of having an decrease in the viscosity stability. But PVA(Polyvinyl Alcohol) aqueous solution returns to original solution state by increasing the temperature and agitation after gelation. To increase the viscosity stability, Thiocyanate, Phenol, Butyl alcohol, Isopropyl alcohol are added. There must be careful to use these viscosity stabilizers because these are affecting the quality of final products.

 

 

 

3-3-5 Surface Tension

 

 

 

 

 

PVA(Polyvinyl Alcohol) aqueous solution decreases surface tension of water and has functions as protective colloid. Surface tension of PVA(Polyvinyl Alcohol) aqueous solution increases as the degree of hydrolysis increases, but there is only a little change in the degree of polymerization. In case of grades with low degree of polymerization(P-05), the surface tension is as low as PVA(Polyvinyl Alcohol) having 80 mol% degree of hydrolysis.

 

 

 

3-3-6 Adhesion of the Solution

 

 

 Wet Track

 

 

PVA(Polyvinyl Alcohol) has superior initial adhesion compared with other natural water soluble polymer. The wet tack of PVA(Polyvinyl Alcohol) aqueous solution increases with viscosity.

Aqueous solution of PVA(Polyvinyl Alcohol) has strong adhesion to hydrophilic substance and the adhesion tends to increase with the degree of hydrolysis and polymerization. The adhesion behavior of PVA(Polyvinyl Alcohol) solution differs according to each substance 

 

 

 

 

 

3-3-7 Thermal properties

 

 

 

PVA(Polyvinyl Alcohol) changes to yellow in color upon heating, and partially hydrolyzed grades melt at 150-190and fully hydrolyzed grades melt at 210-230. PVA decomposes partly around 200-250and rapidly decomposes above 250. The degree of crystallinity increases proportional to the thermal temperature and time.

 

 

 

3-3-8 Mechanical properties of film

 

 

 

PVA(Polyvinyl Alcohol) film generally has good mechanical properties, compared with other plastic films. . Mechanical properties are affected by relative humidity because of plasticizing role of water. As relative humidity or amount of plasticizer increase, elongation and tear strength increase, but tensile strength and young’s modulus decrease.

 

 

 

4. Contact Information

 

 

 

  E-mail : dept2-2@dcchem.co.kr
Tel  :  +82-2-7279-465,413
Fax :  +82-2-774-2735

 

 

5. Others

 

 

 

 

5-1 Direction for Dissolution

 

 

5-5-1 Facility

 

     

 

PVA(Polyvinyl Alcohol) does not corrosive, so a Carbon steel would be used, but Stainless steel is preferable. Sometimes, vessels coated with plastic or other materials may be used. The dissolving vessel must be equipped with either low speed paddle-type agitator or high speed propeller-type one.

 

 

 

 

 

5-5-2 Dissolving Method

 

 

 

 

 

PVA(Polyvinyl Alcohol) should be put into the vessel little by little, so as to prevent the formation of swelling lumps which are very difficult to completely dissolve

 

 

 

 

 

(1) Fully hydrolyzed PVA(Polyvinyl Alcohol)
 

 

 

Fully hydrolyzed PVA(Polyvinyl Alcohol) disperse easily in water without lumps because of low solubility at room temperature. First charge the vessel with suitable amount water. Next charge PVA(Polyvinyl Alcohol) with stirring at room temperature and then heat up to 95. PVA(Polyvinyl Alcohol) is dissolved completely after stirring for 30 to90 minutes, depending on the effectiveness of stirrer and amount of PVA(Polyvinyl Alcohol). (see figure 3)

 

 

 

 

 

(2) Partially hydrolyzed PVA(Polyvinyl Alcohol)
 

 

 

Partially hydrolyzed PVA(Polyvinyl Alcohol) is charged very with stirring at room temperature and then heat up to 90 . PVA(Polyvinyl Alcohol) is dissolved completely after stirring for 30 to 60 minutes. It is good to increase the temperature to save dissolution time, because the higher the temperature of solution, the more likelihood of increases in the dissolution rate. Partially hydrolyzed PVA(Polyvinyl Alcohol) is more likely to produce foam, so rapidly increased temperature or stirring is to be avoided. (see Figure 4)

 

 

 

 

 

 

 

 

 

 

 

 

  Figure 3

 

 

  Dissolution of fully hydrolyzed PVA

 

 

 

 

 

 

 

 

  Figure 4

 

 

  Dissolution of partially hydrolyzed PVA

 

 

 

 

 

 

 

 

5-2 Storage

 

 

5-2-1 Power

 

 

 

 

 

PVA(Polyvinyl Alcohol) has high hygroscopicity If open to ambient, PVA(Polyvinyl Alcohol) adsorbs slowly moisture. It is advisable to store in sealed container.

 

 

 

 

 

 

 

 

5-2-2 Packing

 

 

 

 

 

vessel: kraftpaper bag
Net weight: 20kg.500kg(Ton-Bag), 750kg(Ton-Bag)

 

 

 

 

 

 

 

 

5-2-3 Plasticization

 

 

 

 

 

Plasticizer is used when needed to give a flexibility to PVA(Polyvinyl Alcohol) film. There are Glycerine, Ethylene glycol, Trethylene glycol, Urea, and Ethanol amine as the effective plasticizer. Among them, Glycerine is used in large quantity.

 

 

 

 

 

 

 

 

5-2-4 Gelation

 

 

 

 

 

The most representative gelation agents are borax and boric. The gelation of PVA (Polyvinyl Alcohol) aqueous solution occurs even with a small quantity. The gelation occurs easily with the high degree of hydrolysis concentration of PVA (Polyvinyl Alcohol) aqueous solution.
Also, some dye (Congo red) and pigment (china clay, titaniumoxide, calcium carbonate) cause the gelation and viscosity increases. Therefore, the substances containing these must be handled carefully and be used after empirical tests.

 

 

 

 

 

 

 

 

5-2-5 Extender, thickening

 

 

 

 

 

There are Starch, CMC, Methyl cellulose, Polyacryl amide, Alginic acid soda as a thickener and china clay, titan white, calcium carbonate, starch, dextrin, and casein as extender.
According to PVA(Polyvinyl Alcohol) grades and concentration of mixture, these tend not to be mixed uniformly or become easily separated. 

 

 

 

 

 

 

 

 

5-2-6 Antifoaming agent

 

 

 

 

 

Bubbles occur when starred partially hydrolyzed PVA(Polyvinyl Alcohol) aqueous solution. Antifoams are used to restrain the occurrence of bubbles and get rid of the occurring bubbles promptly. The most effective antifoam is silicone antifoam, but it causes dyeing stain because of water-repellent.

 

   On the other hand, non-silicone antifoam do not cause the dyeing stain, but it has low foaming effect and does not produce a long-term effect. Anti-foam is used according to directions. Generally 0.2-0.4wt% of non-silicon antifoam is used here.  

 

 

 

 
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