Influence of flameproof viscose fabrics on the burning of epoxyorganoplastics

F l a m e p r o o f viscose fabrics

1177

REFERENCES 1. V. N. KULEZNEV, Mnogokomponentnye polimernye sistemy (Multicomponent Polymeric Systems) p. 10, Izd. " K h i m i y a " , 1974 2. D. S. KAPLAN, J. Appl. Polymer Sci. 20: 2615, 1976 3. J. FERRY, Viheo.elastic Properties of Polymers, 1963 4. R. D. MAKSIMOV, V. P. MOLCHANOV a n d Yu. S. URZHUMTSEV, Mekhardka polimeroy, 780, 1972 5. M. MATSUO, C. NOZ/~g! a n d Y. JYO, Polymer Engng. Sci. 9: 197, 1969 6. Yu. S. LIPATOV a n d F . G. FABULYAK, I)okl. AN SSSR 205: 635, 1972 7. V. S. KUKSENKO and A. I. SLUTSKER, Mekhanika polimerov, 387, 1970 8. K. MATSUSHIGE, S. V. R A D C L I F F E and E. BAER, J. Polymer Sci., Polymer Phys. E d . 14: 703, 1976 9. G. I. GUREVICH, Zh. teort, fiz. 17: 1491, 1947 10. B. N. SHTARKMAN, Plastifikatsiya polivinilkhlorida (Plasticization of PVC). Izd. " K h i m i y a " , 1975 11. W. REDDISH, Perekhody i relaksatsionnye yavleniya v polimerakh (Transitions a n d Relaxation Phenomena in Polymers). p. 138, Izd. "Mir", 1968 12. G. M. BARTENEV and A. M. KUCHERSKII, Mekhanika polimerov, 544, .1970 13. V. N. KULEZNEV, Kompozitsionnye polimernye materialy (Polymeric Composites). p. 93, Izd. ":Naukova d u m k a " , 1975 14. Yu. S. LIPATOV, Fizieheskaya khimiya napohmnnykh polimerov (Physical Chemistry of Filled Polymers) Izd. " K h i m i y a " , 1977

Polymer Science U.S.S.R. Vol. 22, Printed In Poland

No. 5, pp. 1177-1185, 1980

0032-3950/80t051177-09507.5010

C 1981 pergamon Press Ltd.

INFLUENCE OF FLAMEPROOF VISCOSE FABRICS ON THE. BURNING OF EPOXYORGANOPLASTICS* S. A . VILKOVA, S. Y E . ARTEMENKO, V. M. LALAYAN, N. A . KHALTURINSKII, AL. AL. BERLIN, A. R . KOGERMAN, E . YE. KHEIN8OO a n d M. A. K_RULL Polytechnical Institute, Saratov Chemical Physics Institute, U.S.S.R. Academy of Sciences Chemistry Institute, E.S.S.R. Academy of Sciences

(Received 26 February 1979) A s t u d y has been made of the fireproofnoss of composites containing ED-20 epoxy resin and flameproof viscose fabric. I t is shown t h a t if a phosphorus-containing flam-retardant is included in the composition of viscose fabric, there is a change in the degradation p a t h w a y of the epoxy resin, and the temperature of the material and the ignition t e m p e r a t u r e are lowered. I n this w a y the composite is rendered flameproof. * Vysokomol. soyod. A22: :No. 5, 1071-1077, 1980.

1178

S.A. VXL~OVAe~ al.

•I ~ r e c e n t y e a r s a u t h o r s h a v e s h o w n increasing i n t e r e s t in t h e p r e p a r a t i o n o f n o v e l fireproof m a t e r i a l s as well as in e n h a n c i n g t h e f l a m e p r o o f p r o p e r t i e s o f e x i s t i n g p o l y m e r i c m a t e r i a l s . Difficulties e x p e r i e n c e d in r e n d e r i n g p o l y m e r s f l a m e p r o o f s t e m f r o m insufficient k n o w l e d g e of relationships b e t w e e n b u r n i n g , p y r o l y s i s a n d t h e actibn of f l a m e p r o o f s u b s t a n c e s , a n d no generMized t h e o r y o f t h e fireproofness o f p o l y m e r i c m a t e r i a l s has y e t b e e n d e v e l o p e d [1]. E p o x y p o l y m e r s are n o t classed as difficultly c o m b u s t i b l e m a t e r i a l s , a n d h a v e b e e n prev i o u s l y studied. F r o m a t h e o r e t i c a l as well as a p r a c t i c a ! s t a n d p o i n t it should be a d v a n t a g e o u s to d e v e l o p w a y s a n d m e a n s of increasing t h e fireproofness of m a t e r i a l s p r e p a r e d f r o m e p o x y resins, a n d it should likewise be o f i n t e r e s t t o i n v e s t i g a t e c o m b u s t i o n m e c h a n i s m s u n d e r v a r i o u s conditions a n d to shed light on t h e a c t i o n of f l a m - r e t a r d a n t s . On a p r e v i o u s occasion [2] we s h o w e d t h a t m a t e r i a l s possessing g o o d f i r e p r o o f p r o p e r t i e s could be p r e p a r e d b y reinforcing s t a n d a r d s y n t h e t i c resins, including a n e p o x y resin, w i t h f l a m e p r o o f viscose fibres a n d fabrics. Moreover, f l a m e p r o o f fibres i n h i b i t c o m b u s t i o n o f t h e c o m p o s i t e s as a whole a n d loss o f t h e resin b y burning, w h i c h n o r m a l l y h a p p e n s w i t h glass-reinforced plastics ( G R P s ) , is prevented. On this occasion we i n v e s t i g a t e d the m a i n f e a t u r e s of t h e pyrolysis a n d c o m b u s t i o n o f E D - 2 0 e p o x y resin, whose c o m p o s i t i o n includes a f l a m - r e t a r d a n t t o d e t e r m i n e h o w f a r t h e resin is influenced b y t h e action o f f l a m e p r o o f viscose fibre. The substance investigated was ED-20 epoxy resin hardened by polyethylenopoly~mino (10 pbw) at 100° for 4 hr. The plastics, reinforced by viscose fabrics, wore prepared by pressmoulding at 90° under pressure of 8-10 kg/cm s with additional heat treatment at 100° for 4 hr. The reinforcing material was a flameproof viscose fabric impregnated with "OP" (i.e. witJa a dicyandiamide phosphate solution) and then subjected to heat treatment; unmodified viscose fabric and glass.reinfooed fabric were used for comparison. The rate of flame propagation on the surface of the material was measured in a quartz tube (diameter 40 mm) under the action of an oxidizing current (oxygen mixed with nitrogen, varying the concentration of the mixtures) flowing at the rate of 41./min, The polymeric specimen is placed on an asbcstes-cement support provided with a heater and an ignition element. The surface temperature of the polymeric material and the flame temperature during combustion were measured with a platinum-platinorhodium thermocouple (13% Rh) of diameter 0.03 ram, and were recorded with the aid of an H-115 multichannel oscillograph. Thermal degradation investigations were carried out using a derivatograph (heating rate 10 deg/min, in argon). The method of pyrolytic gas chromatography in a helium current was used to determine the quantitative composition of gaseous products of pyrolysis. A gas chromatographic column of length 3 m and diameter 3-5 mm was used with activated carbon at 46 ° to carry out the CO, CO2 and CH4 analysis; tLIO was determined with a column 3.6 m long, diameter 6 ram, using polysorb 1 containing 8% of modified TEPA at 90 °. Elemental analyses of the initial specimens and of solid residues of products of pyrolysis were carried out by chromatography, using a 185-B C,H,N-analyzer. Fillers i n t r o d u c e d i n t o p o l y m e r s a l t e r t h e i r t h e r m o p h y s i c a l p r o p e r t i e s [3], which brings c o r r e s p o n d i n g changes in t h e h e a t i n g conditions for p o l y m e r s in t h e p r e - i g n i t i o n region, a n d m a y lead to a change in t h e r a t e of flame p r o p a g a t i o n on t h e stlrface o f the m a t e r i a l s . F o r i n s t a n c e , if glass f a b r i c a n d u n m o d i f i e d

Flameproof viscose fabrics

1179

viscose fabric is added to e p o x y resin, a marked change in the rate of flame propagation is observed (Fig. 1). The oxygen index is lower for viscose fabric reinforced plastics material t h a n for the resin, b u t it rises to 23-4 if glass fabric is introduced into the system. This means t h a t different reinforcing materials differ in their influence on factors characterizing combustion of a material for flame propagation on a horizontal surface and for vertical combustion, which is normal for oxygen index determinations.

vp~ rnrn/sec

/

I

/ 2.0 -

/×/2

,i// I'0-

•

"

40

60

J /

80

I00 Yo, %

/

F1o. 1

Fio. 2

FIG. 1. Rate of flame propagation on epoxide surfacea vs. the O= concentration: 1--ED-20, 2--glass-reinforced plastic, 3--composite containing viscose fabric, d--mixture containing flameproof fabric. Fin. 2. Logarithmic plots of the flame propagation rate vs. the O= concentration. 1--ED-20;

2,3,4--20, 40, 60% content of glass fabric in the mixture; 5,6--60% content of viscose fabric and flameproof fabric respectively. The introduction of flameproof fabric into the system leads to a more marked reduction in vp compared with the system containing the unmodified fabric, which is attributable to the flam-retardant influencing the flame propagation process. To investigate t he influence of thermophysical parameters and of the antipyrene on the flame propagation process we used the relation [4]

v p = k r'~, where Yo is the oxygen concentration.

(t )

1180

8. A. VILKOVAd a L

P a r a m e t e r s k and n, reflecting properties o f t h e p o l y m e r i c materials a n d calculated from the logarithmic plot of Vp-Y0 (Fig. 2) a p p e a r in Table 1. Coefficient k is equal to t h e flame p r o p a g a t i o n r a t e where ]go----1, a n d is a f u n c t i o n o f t h e heating r a t e for the m a t e r i a l in t h e preblazing region, a n d is c o n s e q u e n t l y related to t h e r m o p h y s i c a l properties of the materials. TABLE

1. P A R A ~ - ~ . T E R 8 ]C A N D n C A L C U L A T E D F R O M "l'Jcl~ L O G A R I T H M I C D E P E N D E N C E FLA.M-E P R O P A G A T I O N

RATE

ON THE

OXYGEN

Filler content, %

Composition ED-20 (PEPA) Epoxy glass-reinforced plastics material

-

20 40

Plastics material containing viscose fabric Plastics material containing flameproof viscose fabric

40 60

TABLE

2.

SUP~AO.,E T E M P E R A T U R E S

AND FLAME TEMPERATURES

n

b 1-00

-

60 40 60

OF THE

CONCEN'ITRATION

0.92 0.77 0-53 0.28 0-15 0.28

0-03

2"17 2"17 2"16 2"16

1'61 1"88

1"70 2"11

I N T H E B1TR~I'ING O F EPOX~A"

RESIN .MATERIALS

Indicators A-* X 10-a A-* X Tb j ~°ba ~n°col~ e T°ilsme

ED-20 epoxy resin 3-75 1-33 355 560 1550

Composition with content of viscose fabric, % 40 60 5"70 1.80 32O 560 1550

5.70 1-92 34O 590 1600

Composition containing flameproof fabric, % 40 60 5"60 1.80

320 640

9'00 2-39

270 660 1450

Coefficient n d e t e r m i n e d as the t a n g e n t o f the angle of slope of a s t r a i g h t line to t h e abscissa axis characterizes t h e r m o c h e m i e a l properties a n d is r e l a t e d to the c o m b u s t i o n h e a t o f t h e polymer, a n d to its gasification. I t is seen f r o m Fig. 2 a n d T a b l e 1 t h a t changes in the t h e r m o p h y s i c a l properties of the material (characterized b y a change in k) a p p e a r as the a m o u n t o f inert filler (glass fabric) in the composite is increased; at the same time t h e r m o chemical properties of the e p o x y resin r e m a i n constant. Changes in k a n d n are observed on introducing unmodified a n d f l a m e p r o o f viscose fabrics into the composites. Moreover, whereas values of vp as well as o f n and /c are a p p r o x i m a t e l y identical for b o t h t y p e s of reinforced materials in the case o f a 4 0 % filling, Vp is r e d u c e d for a 60% filling, a n d m a j o r changes in b a n d n are observed. This is due, a p p a r e n t l y , to an increase in the p h o s p h o r u s c o n t e n t of the material, which, with a 60~o c o n t e n t of f l a m e p r o o f fabric, a m o u n t s to 2-3%.

Flameproof viscose fabrics

1181

T e s t s were carried o u t to d e t e r m i n e h i g h - t e m p e r a t u r e values o f vp t o s h e d light on t h e e x t e n t to which f l a m e p r o o f fabric m a y affect basic c h a r a c t e r i s t i c s o f c o m b u s t i o n of t h e e p o x y resin. T h e t e s t results show (Fig. 3) t h a t a rise in t h e t e m p e r a t u r e of t h e s p e c i m e n to 200 ° leads to a n increase in vp in line w i t h t h e empirical equation A

vp (Tbs--To)='

(2)

w h e r e Tbs is t h e b u r n i n g surface t e m p e r a t u r e , T O is the s a m p l e t e m p e r a t u r e , a n d A is a n i n d i c a t o r c h a r a c t e r i z i n g t h e r m o p h y s i c a l a n d t h e r m o m e c h a n i c a l p r o p e r t i e s of t h e m a t e r i a l . v.1/2

Up,mm/sec

2-0 -

2.0 .

I'0-

~

II

1'0 0.5 ~

.

.

a

i

2I

×3 I ,

50

I

I

I00

[

150 TO £00

Fie. 3

0.5

o l~

1

I

50

I00

I

I

150 TO 200

FIG. 4

l~xo. 3. Effect of temperature of the material on the rate of flame propagation on the surface (O= concentration 50~). 1--ED-20; 4,3--40 and 60~o of viscose fabric; and 60% of flameproof fabric.

2,5--40

Fie. 4. Determination of the surface temperagure during combustion from the plot of the flame propagation rate vs. the test t,emperature. 1--ED-20; 2,2'--40~o viscose fabric and flameproof fabric respectively; flameproof fabric and viscose fabric respectively.

3,4--60°/o

U s i n g r e l a t i o n (2) we o b t a i n e d t h e b u r n i n g surface t e m p e r a t u r e f r o m t h e vp j vs. T Op l o t (Fig. 4). I t is seen f r o m T a b l e 2 t h a t t h e b u r n i n g surface t e m p e r a t u r e is significantly r e d u c e d (by 85 °) for t h e e p o x y resin w h e n a 60~/o c o n t e n t o f f l a m e p r o o f fabric is i n t r o d u c e d into t h e composite. T h e i n f l a m m a b i l i t y o f

1182

S.A. VILKOVAet 6[.

'composites is reduced by a lower surface temperature, and the temperature of the material is lowered accordingly. At the same time other results are obtained by direct measurement of TbB using a thermocouple. When measured with a thormocouple the epoxy resin surface temperature is practically 200 ° higher, and the addition of the flameproof fabric makes Tbs practically 100° higher compared with the unfilled resin. This is attributable to the fact that on combustion epoxy resins and materials containing the latter form a sizable coke residue, which covers the epoxy resin surface, and so the temperature measured by the thermocouple is evidently that of the calcined .coke residue. Since the maximum flame temperature for a composite containing flameproof fabric is 100° lower (see Table 2), and since the temperature of the coke residue is correspondingly increased, there is markedly reduced heat flow from the flame to the polymer surface, which likewise reduces the inflammability •of the material.

1~

aw

,lw

CL

o

!

8 I

I00

i

I

JO0

L

I

TO 500

I00

200

300

#00 T"

F]o. 5. TGA (a) ~.nd DTG (b) curves. I--ED-20; 2,4--v~eose fabric and composite prepared from it (60% fabric); 3,5--flameproof fabric and the oomposite (60•).

I t is known [5, 6] that phosphorus-containlng compounds are dehydration catalysts, and alter the degradation mechanism of cellulose. Consequently, the yield of carbon and H=O is higher during combustion of cellulose material, and the amount of inflammable gases is considerably reduced. Pyrolysis investigations .carried out for the epoxy resin, viscose fabrics and composites prepared from these materials, using the method of thermogravimetric analysis in argon, showed that whereas the yield of solid residue is 12~ higher when flam-retardant is added to the viscose fabric (see Fig. ~ ) , a practically id.entical amount of carbon residue is formed (approximately equal to the amount formed during degradation of the epoxy resin) during degradation of the composites containing the unmodified and the flameproof viscose fabrics. This means that surface protection is being prevented during combustion of the composites owing to the higher

1183

Flameproof viscose fabrics

coke yield for epoxides. H o w e v e r , it is clear f r o m the T G A results t h a t t h e r e t h e r e are new changes in the e p o x y resin d e g r a d a t i o n mechanism. W h e r e a s t h e r m a l d e g r a d a t i o n o f the unfilled e p o x y resin takes place in two stages, m a x i m u m rates being o b s e r v e d a t 205 a n d 320 ° (Fig. 5b) and, within a n a r r o w e r i n t e r v a l (230 a n d 300 °) the c h a r a c t e r of t h e d e g r a d a t i o n process is the same for the composite p r e p a r e d f r o m the unmodified fabric, we find t h a t t h e second stage o f t h e r m a l d e g r a d a t i o n is a b s e n t for t h e composite based on the f l a m e p r o o f fabric, a n d d e g r a d a t i o n takes place in a single stage, a n d a m a x i m u m r a t e appears a t 230 °. This points t o a change in t h e d e g r a d a t i o n conditions, which m u s t also involve a change in the composition of d e g r a d a t i o n p r o d u c t s [7]. T h e m e t h o d of p y r o l y t i c gas c h r o m a t o g r a p h y was used to investigate the yield of gaseous p r o d u c t s o f pyrolysis in relation t o the t e m p e r a t u r e of surr o u n d i n g m e d i u m (Table 3). T ~ L E 3. COMPOSITIONOF

G A S E O U S P R O D U C T S OF P Y R O L Y S I S OF E P O X Y P L A S T I C S

Pyrolysis Material

temperature, °C

ED.20 epoxy resin

Plastics material based visoose fabric (60%)

on

Plastics material based on ~rneproof fabric (60%)

Viscose fabric

Flameproof fabric

• In arblh-sW u.~m.

Gas composition, % on sample weight H,O

COl

CO

3'0

0.I

4.5 7-0 5"8 5-8

0.2 0"7

].5 4"0

1-0

18"5

10.3 12.0 12.2

5.7 6-0 7.5

12.8

8-7

13.0

9-5

1.2 3-0 9-5 12.2 II.0

12.0

4-0

14-8

4-7

16-0 16-0 14.5

5.0 6"3 7.5

1.0 2-2 6.0 9.0 10.7

11"5 13-0 15.5 16"5 14'0 16-7 17.0 21.3 21.0 21.2

10-0 10.5 11.5 10-7 10.5 7.6 8.7 9.2 8-5 8.2

1.5 5.0 16.0 15-3 16-0 1.9 2-7 4-5 5.9 9.0

7.3

CH~

HC~

l

NHa* 1.6 3-9 3.1 4.0 3.0

0.5

0.9 1.6 2"5 5.0

Trscos ,p .I

I

"

1"0 2-0

Tra~m

2.6

I'I 1"7

2.5 1.4

II I

0-6 0"5 1"0 3"1

5.4

1184

S.A. Vn~ZOVAet al.

I t tu r n ed out as a result of the increased rate of dehydration the H z 0 yield was highest during thermal degradation of the flameproof fabric and of the composite based on it, the yield being slightly lower for the unmodified viscose fabric, and lowest of all for the epoxy resin. Thermal degradation of the composite based on the flameproof fabric is also accompanied by an increase in the am ount of C02 evolved, and by a corresponding reduction in the amounts of CO and CH 4 compared with gases evolved during thermal degradation of the epoxy resin and of composites containing the unmodified viscose fabric. TABLE

4.

ELEMENTAL AND

A N A L Y S I S O F T H E E P O X Y R E S I N , A N D O F P L A S T I C S P R E P A R E D F R O M IT~ OF SOLID RESIDUES

Material ED-20 epoxy resin Plastics materials based on viscose fabric Plastics material based on flameproof fabric

OF T H E P Y R O L Y S I S P R O D U C T S

Pyrolysis conditions Initially 500° Initially 500° Initially 500°

C 68-03 70-25 51-05 67-26 46-02 59-15

Found, % H 7"33 3.27 6'34 2-89 6-17 3.39

N 4"79 6-85 3-17 6"45 5-42 8-40

On comparing the results of elemental analysis (Table 4) and of pyrolytic gas chromatography, it is seen t h a t during the high-temperature pyrolysis of t h e epoxy resin nitrogen evolution takes place mainly in the form of HCN, the yield increasing as the t e m p e r a t u r e rises, while only an inconsiderable am ount is in the form of ammonia. HCN evolution during thermal degradation of the composite based on the flameproof fabric has a m axi m um at 600-700 °, and is reduced as the temp er at ur e rises. However, the major part of the nitrogen-containing compounds remains during degradation of these specimens in the solid residue, while some is given off in the form of HCN, and some in the form of ammonia. No evolution of ammonia was observed during thermal degradation of the composite based on the unmodified viscose fabric. Thus it is reasonable to conclude in the light of these investigations t h a t t h e addition of flameproof viscose fabric to the epoxy resin leads to reduced inflammability of the entire composite as a result of changes in thermophysical properties: the temp er atu r e of the material and of the flame during combustion is reduced, and the direction of degradation is altered towards evolution of less combustible gases. Translated by R. J. A. HENDRY REFERENCES

1. U. EINSELE, Melliand Textilber., No. 1, 64, 1976 2. S. A. VI~JKOVA, S. Ye. ARTEMENKO, M. A. TYUGANOVA and Z. A. ROGOVIN, Plast. massy, No. 5, 23, 1978 3. K. KANARI, Denki sipena yuci xoksky, 176, 251, I973

Synthesis of polyamido hydrazides

1185

4. V. M. LALAYAN, 'Yu. M. TOVMASYAN, N. A. I~HkLTURINSKII and AI. AI. BERLIN, Vysokomol. soyed. B22: 150, 1980 (Not translated in Polymer Sci. U.S.S.R.) 5. J. E. HENDRIX, J. E. BOSTIC, E. S. OLSON and R. H. BARKEN, J. Appl. Polymer Sci. 14: 1701, 1970 6. J. E. HENDRIX, G. L. D R A K E and R. H. BARKEN, J. Appl. Polymer Sci. 16: 257, 1972 7. M. KRULL, A. KOGERMAN, O. K I R R E L , L. KUMYINA and D. ZAROLSKI, J. AppL Polymer Sci. 135: 212, 1977

Polymer Science U.S.S.R. Vol. 22, No. 5, pp. 1185-1191, 1980 Printed In Poland

0032-3950/80/051185-07 $07.50/0 © 1981 Pergamon Press Ltd.

INVESTIGATION OF MOLECULAR INTERACTIONS OF SOLVENTS IN THE SYNTHESIS OF P O L Y A M I D 0 H Y D R A Z I D E S * Yu. I. MITCHV.NKO,L. M. BRO~CSHT~.I~,B. I. ZrrrZDYUX, V. V. KORSKAX, A. L. RUSA~OV and A. S. CHEaOLYA All-Union Synthetic Fibre Research Institute

(Received 26 February 1979) A study has been made of the molecular influence of solvents on electron densities of reactive groups of p-aminobenzoic acidc hydrazide in the synthesis of polyamido hydrazides. Interactions of the latter with various solvents have been investigated, using model compounds. A mechanism is proposed to account for changes in the reactivities of hydrazide and amino groups in the preparation of P A H differing in their degree of ordering through the use of various solvents.

POLYA_~IIDO hydrazides (PAH) are currently used for the preparation of lfigh strength and high modulus fibres [1]. Several authors [2, 3] have found that variations in the mechanical properties of articles fabricated from the polymers are obtainable by varying the degree of ordering of units in the polymer chains. It was shown in [3] that the degree of ordering of PAH may be varied by altering the reactivity of amino groups of p-aminobenzoic acid hydrazide (ABH) through the use of various solvents and additives. In such cases it is important that data on molecular interactions in these solutions should be available. In the present work the NMR method was used to investigate solutions of PAH and its model compounds in DMAA, DMSO, DMF, hexamethylphosphorotriamide (HMPTA), N-methylpyrrolidone (MP) and 98% HzS04. The NMR spectra were reocrded for the solutions at room temperature, using a 100 MHz INM-100 spectrometer operating. Chemical shifts (5, p.p.m) were determined in rela* Vysokomol. soyed. A22: No. 5, 1078-1082, 1980,