Liquid glass as active filler for polymeric systems

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Nov 29, 2013 (3 years and 10 months ago)

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1

Liquid glass as active filler for polymeric systems

Levichev A.N., Pavlukovich N.G., Valetsky P.M.

A.N. Nesmeyanov Institute o forganoelement compounds of RAS

119991 Moscow GSP
-
1,Vavilov str.,28, Russia

E
-
mail: levichev@ ineos.ac.ru

Доклад на международной

конференции по химии к 50
-
летию ИНЭОС РАН Москва 2004

In engineering practractically all polymers are used in the filled form. Silicates, silicates
of alumina and the solid products of their processing are widely used in the art. Processes of
obtaining fi
lled polymeric compositions involve significant power consumption for crushing of
components and their subsequent uniform distribution in the bulk (volume) of a polymeric
matrix. Durability and the type of filler bonds with a polymeric matrix determines pr
operties of
the composition.

The increase of fineness (a degree dispersity) of filler promotes its more uniform
distribution in a polymer matrix and formation of the greater number of bonds between them (a
matrix and a filler). The ultimate fineness (maxi
mum degree of dispersity) corresponds to
(means) transition of filler into molecular form. It is impossible to transfer solid fillers from
natural sources into said state. Such compositions can be produced by filling with low
-
molecular
(simple) substances
or their solutions.

Sodium silicate is an easily accessible liquid product. It is produced as a commercial
product (commodity) as concentrated water solution under the name “liquid glass”. It’s average
market price is about three thousand rubles (~100$)

per ton, that makes use thereof in
compositions of plastic materials obviously favorable.

It has been revealed, that sodium silicate is capable to form stable emulsions with
solutions of a number of polymers. For the first time it was found out for compos
itions of
sodium silicate with solutions of chlorosulfonated polyethylene (Du Pont’s trade name
Hypolone) [1], but further appeared applicable and for other polymeric systems. The goal of our

2

research is to find conditions and additives which promote formi
ng of liquid silicates
microemulsions with organic solutions of polymers. The liquid silicates transfere into insoluble
substances during the drying
. The spontaneous formation of microemulsions

takes place
when
two unmixed liquids has the same surface tens
ion.

The chemical structure of sodium silicate is considered to be a mix of salts of various
silica acids. It is a transparent viscous colorless or yellowish liquid which dries into transparent
and fragile film. At a room temperature about 50 % of water e
vaporates (fumes away) from it.
Reduction of a mass share of water leads to the fast increase of a viscosity of a solution. Molar
ratio silica : sodium oxide (silicate number) SiO
2
:Na
2
O in a technical product is close to 3.
Drying at room temperature a si
licate gives the one of formula

shown on the fig. 1

:


The

Na
2
Si
3
O
7
∙3,5H
2
O

structure is shown.


S
Si
O
N
a
-
-
-
-
O
-
O
N
a
O
H
H
H
O
O
i
S
i
O
O
O
H
H
H
O



The solution whis low viscosity contains 20 molecules of water per one molecule of
silicate. i.e. corresponds to the formula Na
2
Si
3
O
7
∙20H
2
O. In this case
each sodium ion is
surrounded by six molecules of water and each OH group is bounded to one water molecule.

The greater molar ratio SiO
2
:Na
2
O gives more waterresistanse silicates.

Technically simple method of increasing of silicate number molar ratio is t
he (treatment)
processing sodium silicate with acetone [5] or isopropanol. By treatment of sodium silicate with
isopropanol biphase system is formed, which top layer represents alkaline water isopropanol, and
bottom is a concentrated sodium silicate soluti
on. The bottom layer has an increased the silicate

3

number, due to transition of a part of caustic soda into a layer of water isopropanol.

B
y

th
is

way
from

50% solutions of sodium silicate with the silicate number 2,9 was obtained 60
-

62%
hydrated silicate
with the number of about 3,6. The residue of isopropanol in the bottom layer

reduces the surface tension of liquid silicates and facilitates the mixing thereof with polymers
solutions.

This silicate was used as a mixture with Hypolone solutions, in the pro
duct LX 144.
Sodium silicate, modified by isopropanol, may be
fully
combined with solutions of polymers
than the raw one.

Silicates with multicharges cations are insoluble in water. Thus dissolved in water Cu
2+

compounds being added to sodium silicate giv
e insoluble residue. For example, addition of water
solution of copper vitriol into sodium silicate leads to that the mixture becomes turbid and a pale
blue deposit begins to appear.

It has been found, that the copper vitriol solution, previously process
ed by ammonia and
containing copper (II) complex, mixed up with sodium silicate, forms transparent, painted in
deep dark blue color solutions. In the cold system ammonia holds a coordination with a copper
ion. Heating of such solutions causes a decompositi
on of copper (II) ammonia complex and the
color of a solution
chan
ge to pale blue or aquamarine. When drying copper (II) ammonia
complex silicate losses the ammonia and becomes insoluble.

In the Table 1 the formulations of Hypolone solutions (code LX) with

the modified
silicate solutions are submitted. The coatings, formed therefrom have satisfactory operational
stability in outdoors conditions. Hypolone is used as 11
-
26% solutions in toluene or petroleum
solvent.

In a dried form the films possess a high (
1
М
Pa and more) adhesion to building materials.
The unstable emulsions forms during

drying coating which is stratified onto organic and silicate
layers. The soakage in water in some cases leads to eliminating of coating adhesion to a surface
of metal. Repea
ted drying restors adhesion. This effect is not observed on porous materials:

4

concrete, wood and foamed polymers. Water silicates penetrate deeply into these materials, and
the stayed composite is waterproof one.

Table

1.

Stable emulsions containing Hypo
lone and sodium silicate
.

code
LX

Na
2
Si
3
O
7
∙3H
2
O

Hypolo
ne

CuSO
4

*

5H
2
O

Cu
C
O
3

NH
3

(HOC
H
2
CH
2
)
3
N

Solvent

H
2
O

U
.
S
.%

144

29,3%

7,3%





41,3%

22,1%

36,6%

149

30,6%

7,6%

0,3%


0,2%


43,2%

18,2%

38,6%

148

15,9%

7,8%

1,1%



1,5%

44,4%

29,3%

26,3%

305

17,9%

11,
3%

1,4%


1,5%


55,1%

12,9%

32,1%

140

23,2%

7,5%


0,2%

0,5%


42,7%

25,9%

31,4%

139

12,8%

7,4%


1,2%

3,1%


41,8%

33,7%

24,5%

U.S.%
-

mass share of unvolatile substances
, %;


In the Table 2 the results of properties testing of materials
LX

of the Table

1 are given.
Dry samples represent a strong rigid semitransparent films. In water they swell, repeatedly being
increased in volume, lose a transparency and pass into high elastic condition. The relative
lengthening before break in a dry form
can not excee
d

10 %,
while

in swelled one 200%. It’s
films on steel do not stratify in water and protect metal from corrosion very well.


Table

2.

Waterproof properties of Hypolone


sodium silicate compositions
.



Peeling

Water absorption

%

Heat treatment (30min. 300
°C)

code
LX

coating

from steel
,
24 hours

30 days

Solubility for
30 days, %

Ratio
К
всп

癯汵ve a晴f爠 瑯
i潳猠 潦
睥楧桴h

5

years

volume before
heating

m, %

144

1

10,8%

50,3%

43,5%

2,9

30,9%

149

0,6

75,3%

186,5%

42,9%

2,9

32,0%

148

1*

49,7%

102,8%

28,7%

0,9

43,3%

305

0,5

142,0%

268,0%

44,0%



140

0,6*

101,8%

316,8%

25,2%

2,6

25,9%

139

0,6

2
3,0%

109,0%

60,8%

4,0

26,8%

*
-

The tests are not completed

The best (in respect to) atmospheric proof coating is formed from aquated sodium
silicate, modified by Copper (II) complexes with triethanolamine (
LX

148). This composite has
low absorption and s
olubility in water.

As can be seen from the table 3, it is impossible to remove completely water
-
soluble
silicate from the majority of dry materials. In the coating, washed by water, its share may still
reach 65 or 66,7%.

Thus, it is possible to use Hypo
lone solutions, filled by sodium silicate for a
waterproofing of concrete or other porous building materials. Hypolone is UV stable and hence
may be used for obtaining of roofing membranes.

Table

3.

The influence of permeation of (soakage in) water in
to the composition of water

resistance
Hypolone
-

sodium silicate films.


LX

Composition of a initial films


Composition of a films after
by
soakage

in water for 30
days

Silicate

Hypolone

Other

Silicate

Hypolone

Other


6

144

80,1%

19,9%

0,0%

64,7%

35,3%

0,0%

149

79,5%

19,8%

0,7%

64,0%

34,7%

1,2%

148

60,4%

29,7%

9,9%

44,4%

41,7%

13,9%

305

58,5%

36,9%

4,5%

26,0%

65,9%

8,1%

140

75,1%

24,4%

0,5%

66,7%

32,6%

0,7%

139

60,0%

34,5%

5,6%

0,0%

86,1%

13,9%



As can we see from the table 2, by heating to more t
han 200°
С

the films are bloating.
Their combustibility appear to be rather insignificant, they are not inflammable, do not distribute
a flame and have low smoking ability, being, thus, fire
resistent

waterproof materials.

The
compartability

of

water silicate soluti
on with toluene solution of Hypolone is a
consequence of emulsion formation of
water
-
in
-
oil
type. The continuous phase is formed by a
polymer solution, and a silicate is distributed therein in rather regular intervals. It is possible to
dilute such emulsio
ns by a solvent for polymer. The addition of water do not influence their
viscosity. By drying the uniformity of distribution is saved in a rather wide range of components
ratio. The mixture and emulsion formation runs (occurs) very easily,
and

often
almos
t
transparent structures are formed.

For preparation of the filled compositions the commercial available Hypolone solution
-

varnish XP
-
734, containing 17 % of polymer and modified liquid glass
-

varnish SiL
-
10,
manufactured by us in plant scale was taken.

The components have mixed in a volum ratio 3:1
(LX 150). Then compositions have diluted by toluene additionally: 40 ml of toluene on 60 ml of
emulsion (LX 151) and 40 ml toluene on 80ml of emulsion (LX 152). In the Table 4 the data of
emulsion properties
and plastics are given.
Influence of a share of the organic solvent on
emulsions properties and plastics formed by them:



7

Table 4
.

The influence of solvents on properties of emulsions and solid films.

LX

Silicate

Hypol
one

Solvent
s

Emulsio
n
viscosity
sec

Solubilit
y %

Swelling
in water
%

Water
absorpti
on %
(30
days
)

U.S.%

150

14,7%

10,8%

56,6%

350

54%

38%

314%

29,5%

151

9,0%

6,6%

73,3%

28

18%

110%

300%

18,3%

152

10,0%

7,3%

70,5%

35

18%

162%

160%

20,6%

U.S.%
-

mass share of unvolatile substances
, %;


As can be seen, the addition of organic solvent sharply reduces viscosity of solutions
(conventional paint viscosity was measured). The viscosity decrease creates conditions for
obtaining emulsion with a smaller size of particles, forming more waterproof p
lastic. Loss of
film’s weight in water for 30 days fall (reduces) by dilution of emulsion with toluene from 54 %
in the initial material (mass share of silicate in all three dry films achieves 56,1 %) up to 18%.
Dilution of a polymeric solution by followin
g mixing with sodium silicate results in almost
transparent poorly opalescent systems. Easiness of mixing and appearance of the system
indicate, that microemulsions are formed.

The plastic formed by emulsion drying, consists of a polymeric matrix, inside
which large
portion of water soluble silicate is capsulated (and thus immobilized). The molecules of water
due to osmotic pressure penetrate into polymer,

and

aquatete a silicate. The gel formed gives l a
plasticity to a composition and causes sharp increa
se of volume. Such polymers are capable to
act as gaskets reacting to
presence

of water.


8

It is possible to increase a silicate number through hydrolysis of ethers of a silica acid:
tetraethoxysilane or its technical analogue


an ethylsilicate liquid in a
queous sodium medium of
silicate. Following this route some additional water resistante compounds were obtained


Figure 6.

Penetration of water into concrete insulated by films LX.


0%
1%
2%
3%
4%
5%
6%
7%
8%
9%
10%
11%
12%
13%
0
50
100
150
200
250
Время экспозиции в воде, час
Водопоглощение, %
без покрытия
ЛХ-34
ЛХ-35
ЛХ-116
ЛХ-148


9

On fig.6 the results of of insulating proper
ties determined for films LX on concrete are
submitted. The tests were conducted on dry concrete blocks, all sides of which, except one, were
covered with composition LX. After drying the cover said block was weighed and was immersed
in water on ¾ of heigh
ts of a vertical side. For comparison samples of concrete without cover
were used. Gain in weight of concrete due to penetration of water is determined by periodic
weighing. The data obtained were compared with increase of a block weight without
waterpro
ofing cover. As it is evident from fig. 1, during at least 10 days penetration of water into
concrete through coating LX is practically absent.

Properties of compositions were essentially improved by introducing
polydimethylsiloxanes, received by hydrolys
is of dimethyldichlorsilane. Hydrolysis in presence
of diethyl ether gives yield of cyclic ethers reaching 98%. The introduction of
hexamethyldisilasane (HMDS) or dimethyldichlorosilane hydrolisate also improves properties of
compositions. Organosilicon a
dditives plastsize a dryed product, giving also to a film additional
water
-
repellent properties. After a year of operation on open air the film LX
-
115 saved it’s
strength and elasticity.

Stable emulsions form with sodium silicate not only the solutions of
Hypolone in toluene,
but also the solutions of other polymers in unpolar organic liquids. Now it is determined for
solutions of chlorinated polyvinylchloride, copolymer of vinylchloride and vinylacetate,
polystyrene and nitrocellulose.

Distinctive feature

of polymeric compositions filled by liquid glass is the opportunity of
introduction in them additional amount of traditional fillers: quartzes, kaolin etc. The mass share
of filler can exceed 50%.

The painted sand was used in some compositions as filler.
Such compositions are suitable
for manufacturing of decorative roofing. The films can be covered by layers with thickness up to
4 mm. The dried materials can contain more than 90 % of mineral fillers and only 3 % of organic

10

polymer. Nevertheless, it is str
ong weather
-
resistant coatings, which can be used for a
waterproofing. The compositions being in long contact with water do not lose the weight.

The important technical problem is the creation of fire resistant heat
-
insulation materials.
It can be achiev
ed, filling compositions LX by easy mineral substances for example microglass
spheres.

Conclusions.

1. The solutions of polymers in unpolar organic solvents form stable emulsions with
concentrated water solutions of sodium silicate,
transformed

by drying

into solid, homogeneous
bodies.

2. Microemulsions, formed from diluted polymeric solutions, form a material, in which
the large portion of water soluble silicate is capsulated inside a polymeric matrix and
immobilized. The molecules of water are capable

to penetrate deeply into polymer, formed gel
gives plasticity of all composition and causes sharp increase of volume. The increas
ing

of

silicate
ratio improves property of emulsions and solid bodies, formed from them
.


4. The copper complexes with ammonia

and triethanolamine give water
-
soluble silicates,
in which nitrogen containing ligand saves coordination with copper ion.

6. The compositions
sodium silicate
-

organic polymer have lowered combustibility;

7. The compositions SODIUM SILICATE
-

Hypolone ar
e highly effective waterproofing
materials, suitable for waterproofing roofs, bases and other underground concrete constructions.

8. Filling the polymer
-

silicate compositions by easy mineral fillers allows to get highly
effective waterproof heat
-
isolatin
g materials, including incombustible waterproof heat
-
isolating
materials.

9. Filling the polymer
-

silicate compositions by heavy mineral fillers allows to obtain
waterproofing coatings with increased atmospheric durability and water resistance. Such plast
ics
can contain only 3 % of organic polymers.