EFFECT OF

OF

SOME

MEDIA

ON

GLASS-REINFORCED M.

N.

Kashirina

THE

STRENGTH

PROPERTIES

PLASTICS and

S. M.

Perlin

UDC 621.643.25/29+666.211

During the extraction, storage, transport, and refining of petroleum there is intensive corrosion of equipment and piping which, as is well-known, inflicts a huge amount of damage on the national economy. T h er ef o r e, work aimed at seeking possibilities for using g l a s s - r e i n f o r c e d plastics in piping for grades of petroleum is extremely timely. The present work is devoted to an investigation of the long-term action of aggressive media and elevated temperatures on the mechanical propert i es of wound g l a s s - r e i n f o r c e d plastics. The tests were made using flat samples in the form of bands measuring 200• 10• 3 ram, prepared by winding f r o m a continuous aluminobromosilieate glass fiber with a diameter of 9-12 pro, in the f o r m of a braid containing 30 strands. The c h a r a c t e r i s t i c s of the samples investigated are given in Table 1. The media investigated were: dehydrated petroleum (0.1-0.2% water, 1.7-1.8% sulfur, 40-50 r a g / l i t e r salt); flooded petroleum (46% water, 1.7% sulfur, 2-40% silica gel, 40 r a g / l i t e r salt, 2.5% hydrogen sulfide); and distilled water, the most aggressive medium for g l a s s - r e i n f o r c e d plastics. As c r i t e r i a of the chemical resistance there were adopted the tensile strength and the elastic modulus with elongation, as c h a r a c t e r istics determining the possibility of using the m at eri al for piping for grades of petroleum. The aging was c a r r i e d out in special sealed vessels, at t e m p e r a t u r e s of 80, 120, and 150~ The tensile strength and the elastic modulus with elongation, after the action of the media, were determined in a PDM-2.5 machine, with m e as u r emen t of the deformations using an MK-3 strain gauge, in accordance with the standard method. Before determination of the strength and deformation characteristics, all the samples of the g l a s s - r e i n forced plastics under h~vestigation had an identical relaxation time (2-3 h). In dehydrated petroleum, at all the temperatures investigated, the change in the tensile strength of elongated samples of glass-reinforced plastics is of an extremal character, with a sharply marked maximum. In all the glass-reinforced plastics, the tensile strength.varies predominantly during the first 250300 h, when its values attain a maximum, and then drops somewhat; after 450 h of exposure, the process is stabilized, and the curve goes over into a straight line, practically parallel to the axis of abscissas. An exception is constituted by glass-reinforced plasticswitha9ii binder at 80~ for which there is no extremum, or one which is very much washed out. The values of the elastic modulus, for all the elongated glass-reinforced plastics, after holding in dehydrated petroleum and at the above temperatures, correspond to the starting data, although during the first 250-300 h at 120 and 150~ there are maxima on the curves; they are most sharply marked at a higher temperature and, with time, are shifted to the left. The dependences observed are obviously explained by the relatively small polarity of the medium, which promotes the process of structure formation and reduces the rate of destruction, preventing the penetration of atmospheric oxygen and moisture to the surface of the samples. The results obtained are comparable to the data of other authors [i]. With aging of glass-reinforced plastics in distilled water, the strength is considerably lowered in comparison wfth its starting level. For glass-reinforced plastics based on an ]~D-5 binder, this lowering

I. M. Gubkin Institute for the Pe t r ochem i cal and Gas Institute, Moscow. Translated from FizikoKhimicheskaya Mekhanika Materialov, Vol. 8, No. 5, pp. 78-80, September-October, 1972. Original article submitted May 28, 1971. 9 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 ff'est 17th Street, ."yew York, V. Y. 10011. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanica[, photocopying, microfilming, recording or otherwise, without written permission of the publisher. 1 copy of this article is available from the publisher for $1,5.00.

593

i

TABLE

:

.m

Elastic Tensile Deg,ee o~ {Specific Lu[Martensheal modulus strength Resin with content, setting, % I weight, brieant tr~sistance' under ] g/cmS etonga- elongation, tio0, z kg/cm~ kg/cm 9

Binder.

10 4

PN"~'3

94,5--95,5 95,5--96,0 95,5--96,0

911

~D-5

o

250

1,85 1,85 1,8

500

~ 7~5

286 286800 Above

750 125o

0

2,~

19.4 26.3 26,8

2637 2519 3O03

500

]5o ,25o

39 37 39

I,h

Fig. 1. Aging of g l a s s - r e i n f o r c e d plastics based on b i n d e r s 911 (a) and P N - 3 (b) in dehydrated p e t r o l e u m (O, A, O) and distilled w a t e r (x): 0 ) 80~ A) 120; O) 150; X) 80~

b

a

~ooo oo

~0

2000 lA

20

7000 ~ o

o

1

250

I

500

-t

I

---4;I

750

7250

0

250

500

750 7250

~, h Fig. 2. Aging of g l a s s - r e i n f o r c e d plastics in flooded petroleum: a) b i n d e r 9 i l ; b) binder PN-3. 0) 80~ A) 120; O) 150~ iS 20%, f o r s a m p l e s with PN-3 it attains 59%, and for g l a s s - r e i n f o r c e d plastics with b i n d e r 911 it is equal to 23%. These r e s u l t s a r e in a g r e e m e n t with the r e s u l t s of other work [2, 3]. The lowering of the strength of g l a s s - r e i n f o r c e d plastics with the l o n g - t e r m action of w a t e r is mainly due to r e a c t i o n between the m o i s ture and the binder; such p r o c e s s e s include plasticizing of the binder, lowering the adhesive strength, osmotic phenomena, mid the cleaving action of the medium, leading to a breakdown of the continuity of the b i n d e r as the r e s u l t of the growth of s t r u c t u r a l defects and to breakdown of the adhesive bonds at the glass r e s i n interface. T h e s e p r o c e s s e s o c c u r during the f i r s t 10 days and lead to s t r u c t u r a l t r a n s f o r m a t i o n s of the binder; they then cease, a s a r e s u l t of which the mechanical p r o p e r t i e s p r a c t i c a l l y coincide with t h e s t a r t i n g data. The r e s u l t s with r e s p e c t to the elastic modulus, with l o n g - t e r m action, can be explained by the fact that the modulus does not depend onthe defectiveness of the m a t e r i a l [4], which is e x p r e s s e d p r e d o m inantly in the f o r m of a breakdown of the g l a s s - r e s i n bond. The value of the elastic modulus is mainly det e r m i n e d by the elastic p r o p e r t i e s of the b i n d e r and, since they v a r y only slightly, the elastic modulus also r e m a i n s p r a c t i c a l l y unchanged. With the aging of g l a s s - r e i n f o r c e d plastics in p e t r o l e u m with a high d e g r e e of flooding, it is found that with a r i s e in the t e m p e r a t u r e and an i n c r e a s e in the exposure time the tensile strength f o r all the 594

elongated g l a s s - r e i n f o r c e d plastics falls sharply. At 80~ and holding for a period of 60 days it remains practically unchanged, at a temperature of 120~ it is lowered by 36-59%, and at a temperature of 150~ by 85%. The change in the mechanical c h a r a c t e r i s t i c s of the g l a s s - r e i n f o r c e d plastics investigated, after aging in petroleum with a high degree of flooding with water, can be explained by the same p r o c e s s e s which take place in g l a s s - r e i n f o r c e d plastics under the action of distilled water. Increase in the temperature leads to an increase in the rate of the aging process and to a sharp lowering of the strength properties of the g l a s s - r e i n f o r c e d plastics. In this case, the aging process prevails over the s tr u ctu re formation process, and the change in the tensile strength with elongation (at 150~ is expressed by an exponential dependence. As an example, Figs. 1 and 2 give curves illustrating the change in the investigated c h a r a c t e r i s t i c s of the g l a s s - r e i n f o r c e d plastics as a result of aging in the above-mentioned media. On the basis of the investigations c a r r i e d out the following conclusions may be drawn. AII of the investigated g l a s s - r e i n f o r c e d plastics may be recommended for broad industrial tests in dehydrated petroleums at temp er at ur e s up to 150~ inclusive. In flooded petroleums, the g l a s s - r e i n f o r c e d plastics can operate at t e m p e r a t u r e s up to 80~ inclusive. LITERATURE i.

2. 3. 4.

CITED

V. S. C-umenyuk and V. V. Lushchik, Mekhanika Polimerov, No. 4 (1967). I. G. Romanenkov and G. S. Abashidze, Plasticheskie Massy, No. 3 (1965). W. Bauer, Kunststoffe, ~ No. 12 (1956). G. E. Ponemon, Modern Plastics, No. 11 (1958).

595