PHYSICOMECHANICAL PROPERTIES AND APPLICATION OF MAN-MADE FIBRES

MODIFICATION OF POLYACRYLONITRILE

W I T H H A L O G E N - C O N T A I N I N G P O L Y M E R S

M , S h . S a g a t o v a , B . l~. G e l l e r , D . S h p i l t m a n n , a n d I . Z . Z a k i r o v

F I B R E S

UDC ~77.494.745.32

Numerous f ib re modif icat ions have been developed which a re based on po lymer s and c o ~ l y m e r s of a c r y - loni t r i le [1]. Addition of a weakly compat ible or incompatible po lymers , int roduced through a ~=ommon solvent, makes it poss ible to p r e p a r e f ib res with improved operat ional p rope r t i e s . It is poss ib le to prep~r@ f ib res f r o m a mix tu re of po lyacry loni t r i l e and polyvinyl chloride (PAN-PVC) [2], The introduction of PVC @~ ~pVC) into PAN f ibre leads to a dec r ea se in i ts combust ibi l i ty [3].

We have invest igated the effect of var ious halogen-containing po lymer s (HCP) on the p rope r t i e s of PAN f ib res which have been modified with them by jointly d issolving a mix ture of the po lymer s in d !~o thy l fo rmamide (DMF). As the HCP we took PVC, CPVC, and also Ftor lon (FT). The f ib res were spun into aq t t eo~ p rec ip i t a - tion baths . We studied the devi t r i f icat ion fea tu res of the mix tu res , and the resu l t s obtained were c.ompared with data on the effect of the composi t ion of the mix tu res on the s t r uc tu r a l -mechan i ca l p rope r t i e s of the f ib res . The g lass points of the po lymer s , tg, and of the i r mix tu res were es t imated by the d i la tomet r l¢ al!d t h e r m o m e - chanical methods; f ibre combast ibi I i ty , f r o m the oxygen index value. Cha rac t e r i s t i c s of the f i b r e - fo rming

Content Molecu- Polymer of indicated lar wt., tg, "C

1¢ iTlcn t, M~v by wt.

PAN N 25,9 59000 II0 PVC Cl 56,4 65000 82 CPVC Cl 63,7 72000 94 PT F 51,4 84000 50

po lymer s studied a r e given below:

The voluminous exper imenta l ma te r i a l pe rmi t s one to suggest that the monotonical ly changing tg vs . com- posit ion d i ag rams a re a proof of the uniformity of the po lymer mix tu re (compatibil i ty of the po lymers ) , if the di f ference in the tg values of the components in the mix tu re apprec iab ly exceeds the e r r o r in determining the g lass region. Incompat ibi l i ty of the po lymer s in the solid s ta te is e x p r e s s e d in the fo rm of a ~split s tg vs . composi t ion d i ag ram. When the additions of one po lymer to the o ther a re smal l , only one tg region is displayed, wherein the higher tg a r e somewhat lowered and the lower ones a re r a i s ed somewhat .

For the invest igated PAN--HCP sys t ems , WsplitH tg vs . composi t ion d i ag rams a re rea l ized . At ra t ios of the po lymer s in the mix tu re which a re close to 1 : 1, a m a x i m u m nsplittingn of the tg vs. composi t ion curves is obse rved in the value of tg. As is well known [ 4] , depending on compat ibi l i ty and the ra t io of the po lymer s which have been mixed, in ya rn fo rmat ion the re is obse rved e i ther a s epa ra t e fo rmat ion of supe rmolecu l a r s t r uc tu r e s of each component, o r common supe rmolecu l a r fo rmat ions a r i s e . The speed of phase breakdown exer t s a considerable effect on this p r o c e s s . E lec t ron m i c r o s c o p i c examinat ion of c ros s sec t ions of f ib res spun f rom the examined po lymer mix tu res has shown that he terogenei ty in s t r uc tu r e s begins to be displayed in P A N - C P V C mix tu re s at a second component content g r e a t e r than 1% by wt.; in P A N - P V C , at 2%; in P A N - F T mix tu re s , at g r e a t e r than 5%. An impor tan t fac tor in po lymer compatibi l i ty effects in the solid phase is the ra t io of t he i r volume expansion coeff icients , a , which a r e d i rec t ly connected with the propor t ions of Sfree vol - ume n [5].

The effect of a content of HCP added to PAN on c~ values below (~c) and above (c~ T) was invest igated by the d i l a tomet r i c method, and the i r d i f ference A~ = ~C - - aT , which cha rac t e r i z e s the change in proport ion of nfree volume n relaxat ion, was calculated. With i nc rea se in the HCP content in the mix tu re (Fig. 1), up to a definite value for each pa i r of p o l y m e r s , an ex t r eme r i s e inA~ takes place . The bimodal A a vs. composit ion dependence indicates l imited compatibi l i ty of the po lymer s in the inves t igated s y s t e m s : l a r g e r for the P A N - F T sys tem; s m a l l e r fo r the P A N - C P V C sys t em. At l a rge r a t ios of the po lymers being mixed, the mix tu re becomes macrohe te rogeneous .

T rans la t ed f r o m Khimicheskie Volokna, No. 2, pp. 44-45, March -Apr i l , 1984. Original a r t i c le submit ted June 13, 1983.

0015-0541/84/1602- 0109508,50 © 1984 Plenum Publishing Corpora t ion 109

b

. . . . . . . . zz_- I I I I

1oo 80 6o ~o 2o

PAN content, °1o by wt.

Fig. 1

Orel, c N/tex

26

10 f I i T - ' - - - ' 9 - 4, 8 t2 16 20

HCP content, qo by wt. _

Fig. 2

30

20

Io

Fig. 1. Effect of composition of a P A N - H C P mixture onthe difference in volume expansion coefficients, Aa: 1) CPVC; 2) PVC; 3) FT; additivity l ines are denoted by the dots.

Fig. 2. Ef fec tofcompos i t ion of P A N - H C P mixtures on the relat ive strength, ~rel (continuous lines) and on elongation ~ (dotted lines): 1) CPVC; 2) PVC;

3) FT.

The change in Aa of mixtures is parallel with the dependence of the physicomechanical proper t ies of mod- ified PAN fibres on additions of HCP. When HCP are introduced into a polymer ic substra te , the strength and elast ici ty of the f ibres are raised to an ext reme (Fig. 2). The effect })f small additions of an HCP is displayed par t icular ly c lear ly in the change of res is tance of PAN fibres to fatigue actions (Fig. 3). An ext reme increase in AC~, strength, and res i s tance to double bending of modified PAN fibres is real ized at an HCP content in the mixture which is equal to the polymer concentration in the metastable mixing region, Cm, which is cha rac te r - is t ic of each added polymer .

It was of in teres t to compare the At c and Cm values with the calculated interact ion pa ramete r s for the po lymers being mixed, which were calculated by the formula given in [6]: X = Vr /RT • (61-62)z, where 6 i is the solubility pa ramete r of the uolymer; V r is the ScomparativeS volume, equal to 1 • 10 -4 m3"mole-1; and T = 298°K. Values of 6i" 10 -3 (J/m3) °'s, calculated f rom the data of [6], are as follows: PAN, 26.06; PVC, 19.07; CPVC, 18.78; FT, 21.38. Charac ter i s t ics of mixtures of PAN with HCP are given below:

System Atg, "C Crn , °1o by wt. %,,

PAN - CPVC 15 2 2,12 P AN - PVC I 1 5 1,95 P AN --FT 7 8 0,88

With increase in Xt 2, the val ues of Atg r i se and those of Cm decrease . It is obvious that the region of a metastable state of P A N - C P V C mixtures is considerably na r rower than th i s region is for P A N - F T sys tems . In the process of ya rn formation in spinning f ib re s f rom P A N - H C P mixtures , both cohes ion -adhes ion i n t e r - action and al so entropy charac ter i s t ics of the sys tem, that is, Xiz, exert a decisive effect on s t ruc ture fo rma- tion. The less compatible the mixed polymers are , the less addition of the second component i s required to achieve an improvement in the physicomechanical proper t ies of the modified f ibres.

In studying the effect of FT additions on the coefficient of f r ic t ion of modif ied PAN fibres on meta l , ~m (at a load of 100 cN) and on f ibre , ~f, (at a load of 200 cN), the following relationship was obtained. •

FT content; 3 m /l f % by wt.

0 0,32 0,51 10 0,13 0,62 2O 0,39 0,63

The f i b r e s obtained a re o i l - res is tant , which makes it possible to recommend them (at an FT content of 10%) for use in gland packings. Introduction of up to 20% PVC or CPVC into the polymer ic substra te , in spite of the impairment in physicomechanical charac ter i s t ics , causes a reduction in the f lammabil i ty of PAN fibres [3].

Thus, compatibili ty of HCP with PAN in the solid state decreases in the sequence FT > PVC > CPVC; on introduction of small additions of HCP to PAN fibre via a common solvent, the physicomechanical proper t ies

!1o

n.lO "3

50

25

I I I 8 /2

HCP content, % by wL

Fig. 3, Effect of composition of PAN-HCP mixtures on the resis- tance of fibres spun from them to double bending, n: 1) CPVC; 2) PVC; 3) FT.

of the PAN fibres are improved to the extreme at smaller additions, the less compatible the polymers are. Modification of PAN fibres with HCP makes it possible to prepare fibrous materials which have specific con- sumer properties.

C O N C L U S I O N S

The physicomechauicul and relaxation properties of fibres based on mixtures of polyacrylonitrile with halogen-containing polymers -polyvinyl chloride, chlorinated polyvinyl chloride, and F t o r l o n - have been studied.

It has been found that on introducing small additions of HCP, the physicomechanical properties of the fi- bres rise in an extreme fashion.

I i 2.

3o 4.

5o 6.

L I T E R A T U R E C I T E D

I. Z. Zakirov, Physical Modification of Polyacrylonltrile Fibre [in RuSsian], Fan, Tashkent (1982). L. S. Krasil 'nikova and V. D. Fikhman, in: Fibres from Synthetic Polymers [in Russian], Khimiya, Moscow (1970), pp. 170-175. Inventor's Certificate No. 524869 (1974) (USSR). S. I. Slepakova and B. 1~. Geller, Izv. Vyssh. Uchebn. Zaved., Ser. nTekhnol. Leg. Promsti. , s No. 1, 44- 47 (1973). M. Takayanagi, H. Harima, and S. Iwata, Mem. Fae. Eng. Kyushi Univ. Jim., 23, 1-15 (1963). Polymer Blends, D. Paul and S. Newman, eds., Academic Press (1978).

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