INVESTIGATION MEDIA

ON

MINE

GUIDES

OF THE

THE

EFFECT

STRENGTH OF

AND

REINFORCED

OF

AGGRESSIVE

DEFORMABILITY

OF

PLASTICS UDC 539.412 : 620.193.2

N. G. Tsoi, V. S. Pleten, and V. I. Kolesniehenko

Metal guides (section length 12.5 m) used in mine shafts are subjected to intense corrosion and rapidly fail. It is possible to avoid this by replacing the metal guides with g l a s s - f i b e r - r e i n f o r c e d plastic ones (section length 4.5 m). For this purpose an investigation was made of the strength and deformability of the joints of the sections of s i m i l ar guides and also of their properties during service. The samples were made of a single sheet of g l a s s - f i b e r - r e i n f o r c e d plastic and were tested in air, water, and an aggressive medium. The effect of the medium was rated by comparing the change in the strength properties in tension and bending. The strength of the cemented joints was investigated in a sim ilar manner. The e f f e c t of water and an aggressive medium for 6 months on the strength of g l a s s - f i b e r - r e i n f o r c e d plastic produced using PN-1 and ~D-6 resins as a base may be judged on the basis of the data in Table 1. The results obtained indicate the substantial change in the strength of g l a s s - f i b e r - r e i n f o r c e d plastics under the action of these media. It is important, however, t o reveal what components of the g l a s s - f i b e r - r e i n forced plastic are affected by the medium. Glass fiber is more resistant to water and to acid and alkaline media than the binder and t h e r e f o r e we investigated the water resistance and resistance to the action of aggressive media of PN-1 and E 13-6 resins. Deformation, %

"e ~g

,J

/

2 ,,J

:I.o

2000

2,5 ~ !

86 =~

~SO0

r

800

-~ 400

~d

0,2 a

o

u t

~o

"•'TXO

~o

20

Fig. I

e~

40

120

200

280

380

K,40 J.00

b

~ o

I

40

0,5

t

30

i

180

Fig. 2

Fig. 1. The relationsh{p of the s t r e s s in compression to the relative deformation of PN-I resin in the dry condition (1) and after holding in water for 250 days (2). Fig. 2. Change in strength (I) and weight (2) of PN-I (a) and ]~D-6 (a) resins in relation to the time of holding in water. Institute o f Mechanical Engineering, Voroshilovgrad. Translated from Fiziko-KhimieheskayaMekhanika Materialov, Vol. 11, No. 2, pp. 113-115, March-April, 1975. Original article submitted July 16, 1973.

9 76 Plenum Publishing Corporation, 22 7 West 17th Street, New York, N. Y. 10011. No part o f this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission o f the publisher. A copy o f this article is available from the publisher for $15. 00.

240

It was e s t a b l i s h e d that the d e f o r m a b i l i t y of s a m ples of PN-1 r e s i n a f t e r r e m a i n i n g in w a t e r for m o r e than 250 days i n c r e a s e d (Fig. 1). A reduction in s t r e n g t h and a change in the weight of PN-1 r e s i n in c o m p r e s s ion u n d e r the action of w a t e r o c c u r s p r i m a r i l y during the c o u r s e of 280 days (Fig. 2a). Figure 2b shows the effect of the t i m e of action of w a t e r on the c o m p r e s s i v e s t r e n g t h of ]~D-6 r e s i n and the change in weight. In 240 days the c o m p r e s s i v e s t r e n g t h drops f r o m 1400 k g / c m 2 to 1000 k g / c m 2 (25%) and the weight changes by 0.7%. During this t i m e the s t r e n g t h of PN-1 r e s i n s drops by 34%and the weight changes by 2.5%.

TABLE 1

Medium

Air Water

Acidic (25%

Tensile strength of glass-fiber-reinfSrced plastic, kg/cm2 PN-1 ~D-6 base base 4200 4300 3900 4100 3800 4000

acid solution) Alkaline

3900

4050

7000 / ~

908 ~ _ ~ = v . - . 800

,

2 /

t

.; i

,

/80

200

Time, days

From a gation it m a y to w a t e r than base cements guides as the

c o m p a r i s o n of the r e s u l t s of the be s e e n that t~D-6 r e s i n is m o r e PN-1. T h e r e f o r e I~D-6 o r t~D-5 have been adopted f o r c e m e n t i n g m o r e r e s i s t a n t to w a t e r .

investiresistant resinmine

Fig. 3. Relationship of the bending s t r e n g t h of c e m e n t e d joints of g l a s s - f i b e r - r e i n f o r c e d p l a s t i c box guides (l~D-5 c e m e n t e d joints) to t h e i r holding t i m e in v a r i o u s m e d i a at 20~ 1) n e u t r a l m e d i u m , pH =7.0; 2) alkaline m e d ium, pH =8-9; 3) acid m e d i u m , pH = 2 - 3 .

The study of the effect of a g g r e s s i v e m e d i a on the s e r v i c e p r o p e r t i e s of g l a s s - f i b e r - r e i n f o r c e d p l a s t i c s was made in acid (pH=2-3) and alkaline (pH=8-9) mine w a t e r s f r o m the mine of D o n b a s s a n t r a t s i t C o m bine. The change in the p r o p e r t i e s of g l a s s - f i b e r - r e i n f o r c e d p l a s t i c s u n d e r the action of a g g r e s s i v e m e d i a (medium t e m p e r a t u r e 20~ was judged on the b a s i s of the change in tensile and bending s t r e n g t h a f t e r 40, 80, 120, 160, and 200 days. To obtain a v e r a g e d data six s a m p l e s w e r e t e s t e d . The t e s t s of different methods of c e m e n t e d joints of g l a s s - f i b e r - r e i n f o r c e d p l a s tic conductors showed that the conductor o p e r a t e s p r i m a r i l y in bending and t h e r e f o r e a m i t e r joint is m o s t rational. It was shown that all m e d i a have an effect on the bending strength of the c e m e n t e d joints (Fig. 3). In 200 days the n e u t r a l m e d i u m d e c r e a s e s the bending s t r e n g t h by 5-8%, the alkaline by 10%, and the a c i d by m o r e than 10%. The m o s t intense reduction in s t r e n g t h in the neutral, acid, and alkaline m e d i a o c c u r s in the f i r s t 80 days and then this p r o c e s s o c c u r s v e r y slowly. The t e s t s e s t a b l i s h e d that w a t e r and the a g g r e s sive m e d i a reduce the s t r e n g t h of the binding and weaken the bond between the binder and the g l a s s fiber. Failure has a cohesion c h a r a c t e r (in the binder) o r an adhesion c h a r a c t e r (in the boundary between the b i n d e r and the c e m e n t e d m a t e r i a l ) . Weakening of the adhesive bonds in a m o i s t m e d i u m is caused by e n t r y of w a t e r into the boundary between the binder and the r e i n f o r c i n g m a t e r i a l in g l a s s - f i b e r - r e i n f o r c e d p l a s t i c s through the c e m e n t and the m a t e r i a l being c e m e n t e d through the face of the c e m e n t e d joint d i r e c t l y on to the boundary between t h e m . I n c r e a s e s in the r e s i s t a n c e of c e m e n t e d g l a s s - f i b e r - r e i n f o r c e d p l a s t i c guides to the action of w a t e r and a g g r e s s i v e m e d i a m a y be obtained if the binding g l a s s - f i b e r - r e i n f o r c e d plastic and the c e m e n t have voids with a c r o s s section of l e s s than 2.5 A, by w a t e r p r o o f i n g of the c e m e n t and the binding g l a s s - f i b e r r e i n f o r c e d p l a s t i c at the t i m e of its t h e i r p r e p a r a t i o n by the introduction of s p e c i a l additions, and by p r o tection of the faces of the g l a s s - f i b e r - r e i n f o r c e d p l a s t i c and c e m e n t e d p a r t s with insulating m a t e r i a l r e sistant to w a t e r and acid and alkaline m e d i a .

241-