PHYSICO-MECHANICAL PROPERTIES AND APPLICATIONS OF MAN-MADE FIBRES

CHEMICAL RESISTANCE OF GLASS-FILLED POLYPROPYLENE IN THE AGGRESSIVE MEDIA OF VISCOSE MANUFACTURING G. A. Tsar'kov, I. G. Chernukhina, N. A. Mironov, I. L. Aizinson, V. S. Kurachenkova, and T. I. Podgorodetskaya

UDC 677.463.051.12:678. 742.3:66.018.8

Polypropylene (pp) is widely used as a chemically resistant material for making parts and units of equipment in man-made fibre manufacturing. Along with high chemical resistance, PP has elevated creep, a high coefficient of linear thermal expansion, and significant technological shrinkage (up to 3.5%) [i]. These defects lead to the situation that parts which operate under conditions of an aggressive medium with a temperature up to 100°C under the action of loads over the course of a long period have a short service life. The mechanical properties of molding compositions based on PP can be raised considerably when they are filled with fiberglass and when methods of chemical bonding of the polymer matrix with the filler are used° Thereupon the strength of the material rises by a factor of 2-3; the elastic modulus, by a factor of 3-5; the heat-resistance is raised to 140°C; and shrinkage is significantly reduced. On the other hand, the thermal linear expansion is only 1/4 to 1/3 of the original value; and the relative elongation is only 1/20 [3]. Modified compositions of fiberglass-reinforced PP, Komponor grade, have been developed; properties of these are given in Table i. With increase in fiberglass content, the modulus, strength properties, and heat-resistance of the composition are increased; the relative elongation and impact resistance are lowered; however, in the filling range studied the level of impact resistance values is preserved. The chemical resistance of the modified compositions was investigated according to All-Union State Standard 12020-72 in the sulfuric acid media of the precipitation bath (PB) in viscose textile yarn manufacturing and the very aggressive plasticizing bath (PIB) in viscose technical yarn manufacturing at the Kalinin "Khimvolokno" Industrial Association. The PB, at 48-50°C, contained the following, in g/liter: H2SO ~, 140-145; ZnS04, 17-i9; Na=SO 4, 285-300; surface-active substances (SAS), 0.0035-0.01. The PIB, at 82-99°C, contained the following (in g/liter): H2SO~, 40-45; ZnSO4, 10-13; Na2SO~, 14-15; CS2, 0.15; H=S, 0.005; and SAS, 2.97-0°9. In tests of the compositions, we followed the change in weight and the strength under extension. Test results in the PB and PIB media are given in Figs. 1 and 2. With respect to change in weight in the PB medium, all compositions based on PP may be assigned to the stable category; their swelling was less than 1%. In the PIB medium, the weight of the compositions increased by 6%.~ This makes it possible to assign glass-filled PP, according to State Standard 12020-72, to the relatively resistant materials. In the PB medium, the compositions retain more than 85% of their strength; and in the PIB, about 70%, which exceeds the ultimate strength of unfilled PP almost twofold. Keeping the glass-filled PP i n a PB or PIB medium (up to 150 days) did not seriously affect its specific impact strength. The test results showed that compositions having an elevated degree of glass filling retain the best mechanical properties after the action of the aggressive media in PB or PIB. As is evident from Figs. 1 and 2, swelling and decrease in strength properties of glassfilled PP takes place most markedly in the first 20 days in a PB or PIB. Then this process is sharply slowed down and it takes place at the same rate as in unfilled PP. Considering the character of the change in properties of glass-filled PP, it may be suggested that its Translated from Khimicheskie Volokna, No. 3, pp. 50-51, May-June, 1989. cle submitted August 20, 1987.

0015-0541/89/2103-0251 $12.50

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© 1990 Plenum Publishing Corporation

251

a6",MPa A.m % lO

2'

40 Z s / lO

0

20

r 30 T,

days

0

/0

Fig. i

ZO

JO ~ days

Fig. 2

Fig. i. Kinetics of change in weight, Am, of PP compositions with various contents of fiberglass (FB) in sulfuric acid media of viscose manufacturing: i-3) PB; I'-3') PIB; i, I') unfilled PP; 2, 2') composition containing 13% FB by wt.; 3, 3') composition containing 25% FB by wt. Fig. 2. Kinetics of change in strength in extension, Ao, of PP compositions with various contents of fiberglass (FB) in viscose manufacturing sulfuric acid media: 1-3) PB; 1'-3') PIB; i, i') unfilled PP; 2, 2') composition containing 13% FB by wt.; 3, 3') composition containing 25% FB by wt. TABLE I.

Properties of Fiberglass-reinforced PP Compositions Fiberglass content, % by wt. Property 0

Melt flow index, g/10 min Strength in extension, MPa Elongation at break, % Elastic modulus, GPa Sharp impact strength, kJ/m 2 not notched notched Deformation temperature under a load of 1o8 MPa, °C

4°3 32°0 i00 1ol No b r e a k -

60

13

25

3°9 58°7 6.0 3.1

3°4 70.5 3,8 4.2

34.6 14.6 116

33.4 14.0 124

*At 230°C and a load of 21.6 N strength properties are 2 times as high as in unfilled PP, even on more prolonged exposure, for a year, for example° This affords a basis for suggesting that the operational reserve is several times as great for parts made of glass-filled PP as compared with unfilled PP. Glass-filled PP compositions were processed by injection molding. The molding regime was as follows: melt temperature, 230-240°C; form temperature, 60°C; specific molding pressure 90-100 MPa; holding time under pressure, 40 sec. Parts for spinning machines were made from Komponor and put into manufacturing conditions: brackets, yarn guides, spinneret assemblies, and some others. As a result of tests, it was discovered that, as compared with unfilled PP, the glass-filled material permits one to reduce warping of the parts during manufacture and service. Cartridges for winding Kapron textile yarn which were made from Komponor had 2-3 times as great a service lifetime. By virtue of the greater stiffness of the material, no pinching of the cartridge on the spindle was observed thereupon. The studies performed showed the possibility of using the indicated materials for making parts and closing equipment which operate in the highly aggressive media of man-made fibre manufacturing.

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CONCLUSIONS The introduction of fiberglass somewhat increases the swelling of polypropylene in acidic media, but due to the preservation of a high level of mechanical properties, it permits one to increase the operational lifetime of parts and to reduce warping. From the test results, glass-filled polypropylene of the Komponor grade is recommended for introduction for operation in the aggressive media of man-made fibre manufacturing. LITERATURE CITED io

2. 3o °

Polymer Encyclopedia [in Russian], Sovetskaya Entsiklopediya, Vol. 3, Moscow (1977). G. L. Koren'kov, E. P. Nikulina, et al., Khim. Prom-st' za Rubezhom, No. i, 89 (1982). A. Neiman (ed.), Materials of the Future [Russian translation from German], Khimiya, Leningrad (1985). Yu. A. Mulin, Yu. A. Panshin, and N. A. Bugorkova, Protective Coatings and Linings Based on Thermoplastics [in Russian], Khimiya, Leningrad (1984).

DETERMINATION OF HEAT OF DESORPTION OF MOISTURE IN DRYING POLYACRYLONITRILE FIBRES ~. A. Mal'vinov, I. N. Andreeva, L. S. Gulyaev, A. T. Serkov, and V. P. Kim

UDC 677o494.745.32.021.125.7

It is well known that in moist hydrocellulose fibres the water can be in free or bound form [I, p. 109], the bound water being retained by capillary and solvation forces. In hydrophilic fibres, the latter stage of water bonding with the fibre is practically absent; therefore there can be only free and capillary water in such moist fibres. It was previously shown [2, 3, p. i00] in the case of viscose textile yarn that the thermogravimetric analysis method gives satisfactory results in determining the heats of desorption of free and bound water. In these same researches it was found that, at a denser structure, for example, from fibres of regenerated cellulose obtained from viscoses containing 12% by wt° of a-cellulose, the heat of desorption from the capillaries is approximately 15% greater than the heat of desorption for fibres prepared from viscoses containing 6% by wt. of a-cellulose. Thus, this form of analysis gives an indirect characterization of the overall structural density of hydrocellulose fibres° Knowledge of the heat of desorption of moisture from fibres of other types presents undoubted interest. As objects of study we took polyacrylonitrile (PAN) fibres spun from polyacrylonitrile in a thiocyanate bath. T h e p r o c e d u r e in preparing specimens for the experiment, and also the experiment, which was carried out on a derivatograph from the Hungarian company MOM, have been previously described [2]. Graphical and mathematical treatment of the experimental data were carried out by the procedure of [4]. Treatment of the experimental data revealed that in drying PAN fibre (see Table i), with respect to heat of desorption, the water can be arbitrarily divided into two fractions: a first one with a heat of 2.48 MJ/kg; and the second, with a heat of 5.59 MJ/kg of evaporated moisture° The heat of desorption of the first fraction corresponds to the value for the heat of a phase transformation of water, which is, for the investigated temperature range (from 20 to 60°C) 2.403 MJ/kg of evaporated moisture [5, p. 548], that is, with a deviation of no more than 3.3%. Thus, the method used for determining the heat of desorption has an accuracy sufficient for technical purposes. The heat of desorption of the second water fraction (5.59 MJ/kg of evaporated moisture) is 2.3 times as great as the heat of desorption of free water. For further analysis we use the results of [2]. According Translated from Khimicheskie Volokna, No. 3, pp. 51-52, May-June, 1989. cle submitted July 7, 1988.

0015-0541/89/2103-0253 $12.50

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