Indian Journal o f Chemica l Technology Vol. 9, May 2002, pp. 188- 196

Articles

Utilisation of Jatropha seed oil in the stabilisation of poly (vinyl chloride) against thermal degradation

F E Okieimen

Uni versity of Benin, Department of Chemi stry, Benin City. Nigeria

Recei1 •ed 5 Marrh 2001; revised received 4 Januarv 2002: accepred 14 Febnwrv 2002

Jatropha seed meal was extracted with n-hexane and the oil obtained was found to have iodine value 157.37, acid value 5,61 and free fatty acid 2.70. The fatty acid profile of the oil showed that oleic acid (31.35 %), palmitic acid (20.9 %) stearic acid (15.68%) and caprylic acid (10.45 %) were the major fatty acid components. The seed oil was epoxidised at 29°C using peracetic acid produced in situ by reacting hydrogen peroxide (30 % vlv ) wi th various amounts of glacial acetic acid. Barium, cadmium, lead and zinc soaps of the oils were prepared by metathesis in alcohol solution. Thermal degradation studies on poly (vinyl chloride) in the presence of Jati'Opha seed oil, the epoxidised oil and the metal soaps of the oils were carried out at various temperatures (170, 180 and 190°C) under oxidati ve and non-oxidative conditions. Changes in intrinsic viscosity and levels of unsaturation in the degraded polymer samples together with kinetic data (rate measurements at 1% conversion) were used to evaluate the relative stabilising effect of the additives on the thermal degradation of poly (vinyl chloride). It was found that a lthough the values of the rate of dehydrochlorination were of about the same order of magnitude (10-2% min·\ the rates were relatively lower, and the time at which degradation reached 1% conversion considerably higher than the corresponding values obtained in the ·absence of the additives. The data from solution viscosity measurements and from estimates of the level of unsaturation in the degraded polymer samples indicate that metal soaps of the oil exert stabilising effect on the oxidative and monoxidative thermal degradation of poly (vinyl chloride).

The low thermal stabil ity of poly (vinyl chloride), PVC is one of the inherent problems associated with the manufacture and use of the polymer. At elevated temperatures, well below its decomposition temperature, PVC loses HCI , and becomes colourless, leading to changes 111 chemica l and physical properties of the polymer. Thermal degradation of PVC is genera lly considered to be initiated at unstab le st ructural irregular sites (particu larly tertiary and allylic ch lori des) within PVC; and so me authors 1

-5

have claimed that these structural defects are respons ible and can accoun t for the low thermal stability of the polymer. Although structural irregu larities considerably increase the initial rate of PVC degradation ; and indeed initial rates of degradati on at low convers ions (0. 1-0.3 %) have been shown to correlate well with all ylic and/or tertiary chloride content of PVC6

'7

; it has been argued that on accoun t of the low concentrations in normal PVC of these structural irregulariti es, the ini tiation of thermal degradation of PVC also takes place at regular monomeric units8

-12

. In add ition to the difficulties in identification and quantification of such small amou nts of lab ile allyli c and tertiary ch lorides with in

For correspondence (E-m:.~il : okieimen@uniben.edu)

normal PVC structu re, it is difficult to separate their effects on degradation from that of normal polymer units 13

. It is now generally well accepted that random elimination of HCl from regular monomer sequence are responsible for the higher degree of conversion which degrade the polymer 14

The poor thermal stab ility of PVC requires the use of stab ili sers in the processing of the polymer. Thermal stabi lisers fo r PVC are known to function by replacing labile chl orine atoms in the polymer, they scavenge the HCI evolved at the onset of degradati on and thereby preclude its autocat3lytic effect on degradation; they modify chain react ions and hence inhibit the eliminati on of HCl , and they interrupt the fo rmat ion of polyene sequence in the polymer. Addi ti ves that have found practical app li cation as thermai stabilisers for PVC includes metal sa lts of orga ni c acids, organometallic compounds and inhibitors of radical chain reactions .

In previous studi es, the su itabili ty of rubber seed oi l (raw and processed) in the preparati on of alkyd resins 15

-17 and of its epoxide and metal soaps as

thermal stabilisers in PVC fonnu lations 18-20 was

reported. The results obtained from the latter study required that similar renewable resources be investigated. The overall purpose of these studies is

Okieimen: Utili sation of Jatroph Seed Oil against Thermal Degradation of PVC Articles

the development of value-added products o f po tenti a l practi cal appli catio n fro m local resources. In the present study , the chemi cal characteri satio n of Jatropha mult{filda seed o il, and the effec t o f its epox ides and metal soaps o n the thermal degradatio n of PVC has been reported .

Jatropha multifida is a medium-sized woody pl ant with simple pa lmate or lobed leaves and umbel inflorescence. The plant has bri ghtly coloured fl ower whi ch makes it an orn amenta l plant. The fruits tends to be capsular, green when tender, ye llow when strong and dark-brown when dry. The dry fruits consists o f three seeds whi ch are wind di spersed . The pl ant ex udes a whiti sh sap which is used loca ll y in the treatment of sore gums (pyorrhea) . At present Jatropha multifida seed o il , JSO, has no commerc ia l va lue in this country

Experimental Procedure

Materials Jatropha seed o il was sohxlet-ex tracted with n­

hexane from ground Jatro pha seeds co llec ted fro m around Benin C ity , and analysed for iodine value, saponi fication value, perox ide va lue, ac id value, and

free fatty ac id2 1. PVC (BDH Ltd) ( M n = !.Ox I 05

,

part ic le size of 100% passed B .S 60mesh and 74% passed B .S 200 mesh) was purified by solution in tetrahydrofuran/aceto ne mi xture and precipitated w ith constant stirring in a large excess of methano l. The prec ipitated po lymer was filte red o ff after 24h , washed with methanol and air-dried

Determination of fatty acid composition of Jatropha seed oil

Methy l es te rs of the fatty ac id o f compo nents of the ex tracted JSO were prepared according to the o ff ic ial method of the American Oil Chemi sts Societ/ 1

• The fa tty acid compositi on was determined using Gas Chromatograph, GC, Pye Unicam 104 equipped with a fl ame ioni zat ion detector, FID. The g lass column , 1.5 m long with 0 .4 mm di ameter was packed with 12% PEGS acid-washed chro msorb W . Flow rates were nitrogen carri er gas, 33 cm3 min·1

• Gas chromatographic peaks were identi fied by comparison of retention times with those o f standard methyl esters of pure fatty ac ids. The proportions of the fatty ac ids present in the seed oil were calcul ated on the basis of the mass o f the ir methy l es ters fro m retenti on times of known standard using a Vari an model COS 401 integrator.

Epoxidation of Jatropha seed oil Epox idation of JSO was carried out at 29°C using

peraceti c ac id prepared in situ by reacting hydrogen peroxide (30% vl v) with vari ous amo unts of g lac ial ace ti c ac id in the presence of two dro ps o f concentrated sulphuri c ac id. The level of epox idati on was determ ined using the method descri bed by Durbetaki22

. T he epox idi sed Jatropha seed o il , EJSO,

samples were stored at 7°C until required .

Preparation of metal soaps of Jatropha seed oil Metal soaps were prepared from JSO and EJSO by

metathes is in alcoho l solutio n23"24

. The sodium soap o f the o il s were firs t prepared by dissolving the o il sa mple (9 .2 g) in 50 mL of ho t ethano l fo ll owe.d by treatment w ith 20 mL o f 20 wt% sodium hyd roxide so lution. To this mi xture I 00 mL of 30 wt% solut ion of the metal salt were slow ly added with continuous stirring . The precipitated meta l soap was washed with hot wate r and a ir-dried .

Nonoxidative degradation-Rates of dehydrochlori­nation

Nonoxidative dehyd rochlorin ation studies were carri ed o ut using PVC powder in the presence of JSO ( I 0 wt% ), EJSO ( I 0 wt%) and 3 wt% o f the meta l soaps of the o ils. The po lymer sample ( 1.5 g) was mi xed thoroughly with appropri ate amount of the additi ve and transferred to a degradation tube. The tube was connected to a source of nitrogen mainta ined at a fl ow rate of 60 mL min·1

• The degradation tube was immersed in a the rmos tat o il bath contro lled to a

precision of± l .0°C. The HC I evolved was passed into a known volume o f standard sodium hydroxide solution. The amount o f HCl evolved was es tablished after various periods of time by titration. The extent o f dehydrochlorinati on (% conversion) was calcul ated fro m the ratio of HCl evolved to the amount avail able in the polymer.

Oxidative degradation Thermoxidati ve degradatio n studies were carried

out in a ir as described for nonox idati ve degradati on except that rates o f dehydroch lorinatio n were not monitored . Degradatio n was a llo wed to proceed fo r various period of time (30 , 60 and 90 min) at the end of which the degradatio n tube was allowed to cool, and the degraded po lymer was recovered and stored in the dark .

Viscosity measurements A po rtio n of the degraded po lymer sample was

di ssolved in cyc lohexane and precipitated in a large

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excess o f methano l. Viscos ity measurements o f undegraded and degraded PV C samples were carri ed

out in cyl cohexane so lution at 30°C. The intrinsic viscos ity and Huggin 's interac ti on constant were determined us ing the re lati o nship25

.

... ( I )

here ll sp is the specific viscos ity measured as Y] ,.- 1;

where ll r is g iven by lholnlll so lv = tllo, and ll soln is the viscos ity of the polymer soluti on, and ll solv is the viscosity of the so lvent measured at the same temperature, ti s the fl ow time of the polymer and to is

the fl ow time of the solvent . [11] is the intrinsic

viscos ity taken as Y],pi'C as C---+0 and C is the concentrati on of the po lymer so luti on in g/dL; and k is the Hugg in 's constant.

Levels of unsaturation in polymer samples The levels of unsaturati on in undegraded and

degraded PVC samples were estimated from their iodine values determined by the British Standard Instituti on methods of analys is of fats and oil s26

.

Results and Discussion Physico-chemical characteristics and fatty acid composition of Jatropha seed oil

The physico-chem.ical properti es of JSO are shown in T able I. The level of unsaturation of the oil , measured in terms of iodine value, is about the same order of magnitude with the va lues reported for linseed o il , soyabean oil and rubber seed oil20

. Thus JSO can be class ified as semi-dry ing oil , with implicati ons for the practical appli cation of the oil in alkyd res in preparation. The peroxide value of JSO, 5. I 1 meq kg-1 is relatively low ; lower than the range (20-40 meq kg-1

) within whi ch the onset of rancidity is genera lly observed . The low peroxide value reported for JSO, when considered with the high iodine value indicates that in situ oxidation reactions leading to ranc idity of the o il are low in Jatropha seeds.

Nonoxidative degradation-Rates of dehydrochlori­nation

The rates of dehydrochl orinati on of PVC at 180°C in the presence of JSO and EJSO are shown in Fig. I . Similar plo ts were obtained for the dehydrochlorination of PVC at the vari ous temperatures ( 170°C and J90°C). The time required fo r dehydrochlorinati on to attain I% conversion, loH,

190

Indian J. C he rn . Techno !. , May 2002

and the rate of degradati on at 1% conversio n, RoH , were used to assess the stabilising effec t o f the additives on the the rmal degradation o f PVC. The values o f loH and RoH for nonoxidati ve degradatio n of PVC in the presence of JSO additi ves are given in Tabl e 2. The rates o f dehydrochlorination o f PVC in

the presence of JSO at 170, 180 and 190°C at I% degradation were about the same order of magnitude ( 10-2% min-1

) but was hi ghest at 190 ~c (3.70x !0-2% min-1

). The values of tDH ranged fro m 11 9 min at

Table 1-Some physico-chemical charac te risti cs and fa tty aci d compositi on o f Jatroph a seed o i I

Para meter Physico-chemical compositi011 Oil content (wt%) Acid va lue (mg KO H/g) Iodine va lue (mg 12/1 OOg) Perox ide va lue (meq/kg) Sapo nificati on va lue ( mg KO H/g) Free fatty acid (%) us o le ic ac id Spec ific g ravity (at 30°C)

Fa11y acid composition ( o/o ) Capry lic Myri sti c Palmitic Steari c Ole ic Palmitol e ic Linole ic Vernolic Arachidic Behe nic Li onoceri c

Value

62 .20 5.6 1 157.37 5. 11 190. 12 2.70 0.92

9.46 2.6 1 20.57 15.64 30.25 3.59 5.25 2.62 5.68 1.6 1 0 .98

30r--------------------------,

~~ ·;n '-4> > c: 0 u

10

-~o- No oddttive

-<>-----o-- J so --t:r-----l:r- EJS (10 ·5mol '/, epox idised

Fig. J - Dehydrochlo rinat ion of PVC at I R0°C in the pr~scnce o f Jatropha seed o i I. % convers ion vs Degrada tion time (min)

Okieimen: Utilisation of Jatroph Seed O il against T hermal Degradation of PVC Articles

170°C to 27min at l90°C. When compared with the va lues obtained in the absence of JSO, these results show that JSO exerts a stabili sing influence o n the

degradation of PVC, except at 190°C where the values of R ot-t and fmt suggest a deleterious effect. A simi lar trend was reported for the degradation o f PVC in cashew nu t she ll liquid27 and in the presence of

rubber seed o il 28 and Khaya senegafensis seed o il 29 .

The va lues of Rott and !ott obtai ned for the degradation of PVC in the presence of epox idi sed Jatropha seed oi l EJSO, are shown in Table 2 . The results show that va lues of lmi iflc reased from 70 to

110 min at l70°C, 47 to 70 min at 180°C and from 28

to 40 min at 190°C as the level o f epox idati o n inCI·eased from I mol % to 9.5 mo l %. The values of R oH decreased with increase in the levels of epoxidation. The stabili sing effect of EJSO o n the degradation of PVC is considered to result from the facile reac tion between the HCI evolved at the early stages of dehydroch lorinati on with the epox ide. This

reaction would reduce the cata lyti c effect of HCI on the process of dehydrochlo rination and shou ld lead to a reductio n in the overa ll rate of HCI e liminat ion. It would therefore be expected that the stab i I is ing effec t of EJSO on the degradation of PVC should increase with increase in the level of epoxidati on. The resu lts in Table 2 are consis tent with thi s suggesti on. However, the results show that the values of R01-t

obtained in the presence of EJSO are genera ll y higher

than the values obtained in the presence of JSO and in the absence of the add itives; suggesting that EJSO has

a deleterious effect o n the thermal degradation of PVC. It is to be noted that for an additive to be effec tive as thermal s tab ili ser, it shou ld be stab le at the degradation temperature and be present in suffi c ient amount to mitigate degradation . These results while showing that EJSO exerts so me stabili sing influence on the thermal degradation of PVC at the early stages of dehydrochlorination, the va lues of toH and R oH suggest that the amount of HCI

Table 2- Thermal dehydroc hlorination of PVC in the presence of Jatropha seed oi l at 170. 180 and 190°C

Add itive Temperature loH 102 R011 (OC) (min ) (o/o min-1

)

None 170 82 1.0 180 50 1.67 190 44 2 .86

EJSO ( !Owto/o) 1.0 mol % epoxidi sed 170 70 ( J 19) 2. 17 (0.83)

180 47 (75) 3.57 (1.33) 190 28 (27) 5.00 (3.70)

5.6 mo l% epox idised 170 82 2. 14 180 58 3.33 190 40 4.80

9.5 mnl% epox idi sed 170 ll U 2.0 180 70 2.93 190 37 3.33

Meta l Soaps ofJSO (3wto/o) 13arium soap 170 141 1.33

180 87 1.60 190 59; 73" 2 .00; 2.00"

Cad mium soap 170 122 0 .67 180 120 1.33 190 74: 144" 1. 82 : 2.00"

Lead soap 170 120 0.89 I SO 120 1.43 190 70; 10( " 1.85; 0.54"

Zinc soap 170 145 1.1~

180 97 1.33 190 67; 88" 1.90: 1.60''

Values obtai ned in the presence o f unepoxidi scd JSO in parent hes is. a = Values obtained in the prese nce of metal soaps of EJSO (9.5 mol o/r cp• Jx idi , ed).

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eliminated fro m PVC at I% degradati on may we ll be in excess of the epox ide content o f the additive.

The rates o f dehydrochlorinati o n of PVC in the presence o f cadmium soaps of JSO and EJSO at

l90°C are shown in Fi g. 2. Similar results were obta ined fo r barium, lead and zinc soaps o f the o ils. T he va lues o f R oH and t oH obtained in the presence o f the metal soaps of the o il s are shown in T able 2 . The results show the metal soaps o f JSO are more effec ti ve than JSO and EJSO in suppress ing dehydrochl orinati on of PVC and the re lati ve order o f stabili sati on effec tiveness is cad mium soap>lead soap>zinc soap>barium soap . The mechani sm by whi ch metal soaps stabili se PVC aga inst thermal degradation in volves the repl acement o f labile chl ori ne atoms within PVC structure with carboxy late group whi ch is more hea t stable30

"3 1

. Direct ev idence of chl orine substitutio n with carboxy late group was first reported by Frye and Horst30 from radi oactivity re tention measurements and mo re recently from Ff­IR analys is of PVC/metal soaps films32

. Meta l soaps are a lso considered to be effec ti ve HC l scavengers, precluding the autocatal yti c effect on the dehydrochlorination process o f the J--I C I evolved at the ini tial stages of degradatio n. The enhanced stabili sation effec ti veness of metal soaps fro m JSO is thought to be partl y due to the higher heat stability of the soaps than EJSO and JSO. For instance temperature at the o nset of decomposition o f the metal soaps was found to vary fro m 130°C for barium

soap to above 180°C fo r cadmium soap32.

c

30r------------------------------, -o---o- No additive

~ Cadmium soap of JSO

--o-----o- Cadmium soap of EJSO-

-~ 20 0

"' ... ., > c: 0 u

o~~~----~--~----~--~~--~~ 60 80 100 120

Dtgradot ion tim~ (min)

Fig. 2- Dehydrochlorinat ion of PVC at 190"C in the presence of cadm ium soaps of Jatropha seed oil % conversion vs Degradation time (min)

192

Indi an J_ Che rn . Tec hno !_ , May 2002

The values of R0 1.1 and /0 1-1 obtained fo r the degradation o f PVC in the presence of metal soaps of EJSO are shown in Tabl e 2. The values of l oH and R 0 1-1

obta ined in the presence o f the metal soaps of EJSO <:u·e markedl y hi gher (by up to 80%) and lower (by up to 50%) respectively than the corresponding va lues obta ined in the presence of the metal soaps of JSO. T he enhanced stabili sing e ffec t of metal soaps of EJSO o n the degradati on of PVC is more apparent when the results are co mpared with the correspond ing va lues obtained in the presence of EJSO . It is tho ug ht that the metal soaps of EJSO showed the combined e ffec ts o f the epox ide group and the metal soap in stabili sing PVC against thermal degrad tio n.

Barium and cadmium soaps o f carboxy li c ac ids are often reported to exert sy nerg isti c stabi li sing effect on the degradation of PVC. Mi xtu res of barium and cadmium soaps o f JSO were degraded under ni trogen at 190°C. The variati ons of the measured va lues of R 0 1-1 and l o1-1 with the compositio n of the mi xture are shown in Fig. 3. The results show that mi xtures of barium and cadmium soaps of JSO showed sy nergisti c stabili sing effec t o n the degradati o n of PVC. The combined effec t of barium and cad miu m soaps o f JSO in stabili s ing PVC aga inst thermal degradati o n is cons idered to fo llow the sequence3~ ·35

(a) facile reactio n of the more reacti ve component of the mixture (cadmium soap) with labile chl orine ato ms in PVC; (b) conversion o f the cadmium chloride formed in reactio n (a) above to the soap by reacti on with barium soap and (c) scavenging of HC I

110

3-0 100

90 c: E

80

70

60

1 - 0L---~------,~--f:;--,l.;--~~50 20 40 60 80 100

Composition (wt ·; . cadmium soap)

Fig. 3- Dehydrochlorination o f PVC at 190°C in 1hc presence of mi xtures o f barium and cadmiu m soaps of JSO 1 0~ RoH (% min "1

) vs compos ition (wt% cad mium soap)

Okieimen: Utilisation of Jatroph Seed Oil against Thermal Degradation of PVC Articles

formed during dehydrochlori nation by the metal soaps. The reaction that is perhaps most critical to the stabili s ing influence of the soap mixtures is the conversion of cadmium chloride to the soap. It would seem from the results in Fi g. 3 that the reaction sequence attained optimum effectiveness at cadmium to barium soap ratio of 9: I .

Viscosity measurements The viscosity parameters of PVC samples degraded

in the presence of JSO additives are shown in Table 3. The major reactio ns that may take pl ace during thermal degradati on of PVC include dehydro­chlorination , chain sc iss ion and crosslinking, a ll of which influence the viscosity of the degraded polymer sample. Degraded PVC is semi-flexible in nature, with the conjugated po lymeric sequence introd uced in the polymer on dehydrochlorinatio n constituting the rod-like part and the undegraded portion being fl exible. It has been reported that the intrinsic viscosity o f PVC undergoing degradation decreases

initially to a minimum and then increases with further increase in the number of conjugated double bonds in the polymer36 probably due to reduced flexibil ity a long the main polymer chain axis and cross linking. Therefore, if the extent of dehydrochlorination is kept low, changes in the values of intrinsic viscosity can be taken as es timates of the ex tent of degradation : the lower the va lue of intrinsic viscosity; the greater the extent of degradation . The re lative intrinsic viscosity

[11]1[11] 0 , where [11] 0 is the intrinsic vi scosity of undegraded PVC sample can be used to assess the ex tent of degradation and the effect of JSO additi ves on degradation. Table 3 shows th at the va lues of

[11]1[11]o decrease with increase in degradati on time, and that the va lues of intrinsic viscos ity are hi ghest for PVC samples stabilised with metal soaps of EJSO and lowest fo r the un stabili sed PVC samples. These results show that JSO additives are re lati ve ly effect ive in stabilising PVC against thermal degradatio n and are consistent with the data from rate of measurements.

Table ] - Intrinsic viscositi es and I-luggin 's interac ti on co nstant for PVC degraded in the prese nce of EJSO addit ives at 190°C

Addi tive

None

EJSO ( 101Vro/o) 5.6 mol% epoxidi sed

4.5 mol% epoxidi sed

Meral Soaps of JSO (3wr%) Barium soap

Cadmium soap

Lead soap

Zi nc soap

Time of degradati on (min)

30 60 90

30 60 90

30 60 90

30 60 90

30 60 90

30 60 90

30 60 90

[lllc = In tri nsic vi scosi ty of undegraded PVC= I I 0 Values obtained in the presence of unepoxid ised JSO in parenthesis. a= Values obtained in the presence of metal soaps of unepox idi sed JSO.

1-Iugg in ' s constant K

74.30 120.20 197.30

18.00(27.33) 65.58(66. 13) 140 00(222.00)

19.30 47.26 73.24

33.67:27.78" 33.06;51.65 " 111.10;131.51 "

16.68; 17.6R" 34.29:56.69a 62.50: 137. 17"

20.4 1 ;20.4 1" 28. 73;56.69" 73.05;97 .65"

2 1.00:27.78 " 43.40:59.49 " 9 1.83;77. 16 "

[11] (11 ]/(ll lo (d l/g)

0.3 1 0.27 0.23 0.20 0.15 0. 13

0.69(0 56) 0.60(0.49) 0.38(0.36) 0.30(0.31) 0.25(0.20) 0.2 1(0. 17)

0.72 0.63 0.46 0.40 0.32 0.2))

0.65 ;0.60" 0.57:0.52a 0.55;0.44" 0.48:0.38" 0.30;0.26" 0.26;0.23"

0.77:0.77" 0.67;0.67" 0.54:0.42" 0.47:0.37" 0.40;0.27" 0.35:0.23"

0.70:0.70" 0.6 1 :0.57'' 0.59:0.42" 0.47;0.37" 0.37:0.32" 0.35 ;0.23"

0.69 ;0.66 " 0.60:0.57 a 0.48:0.4 1 " 0.42;0.36 " 0.33 ;0.36 a 0.29:0.3 1"

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Thermoxidative degradation The intrinsic viscosity of PVC sampl es deg raded in

air at l90°C for various period of time in the presence of JSO additives are shown in Tabl e 4. The results show that the values of intrin sic viscosity of degraded PVC samples are lower than the va lues for the undegraded polymer. It can be seen from the results that the values of int rinsic viscosity of PVC sample degraded without the add itives are less than 30% of the va lue of the undeg raded sample while the values of intrinsic viscosity of the polymer samples degraded in the presence of JSO additives are much higher, generally between 30 and 70% of the intrinsic vi scosity va lue of the undegraded PVC. These results show that the extent of degradation of PVC in the presence of JSO additives is smaller than in the absence of the additives. Thermoxidative degradation studi es on PVC were also carried out using mixtures

of barium and cadmium soaps of JSO at 190°C. The

Indian J. Chcm. Techno!., May 2002

variation of the relative intrinsic viscos ity and iodine va lue of the degraded PVC samples are shown in Figs 4 and 5 respectively as function s of composition of soap mixture. Fig. 4 shows that the value of intrinsic viscosity decreases initia lly with increase in the cadmium soap content of the mixture and the reafter increases to a maximum value of about 0.70 and 0.40 for polymer samp les degraded for 30 and 90 min respective ly at 90 wt% cadmium soap content of the mixture and indicate synergistic stabi lis ing effect on the degradation of PVC.

The levels of unsaturation of PVC degraded in air

at 190°C o f various period of time are shown in Fig. 5. The e lim ination of HCI d uring thermal degradation of PVC leads to the formation of olefinic bonds in the polymer molecu le. Therefore provided that the ex tents of degradation are low, and dehydrochlorination is not accompan ied by secondary reactions, measurements of the level o f unsaturation

Table 4- Thermoxidative degradat ion of PVC in the presence of Jatropha seed oil. Vi scosit y data of polymer sample~ degraded at 190°C

Additive Time of deg radation Huggin 's consta nt [TJ] [T] ]/[T]]o (min) K (dllg)

None 30 0.3 1 74.30 0.27 60 0. 23 120.20 0.2.0 90 0.15 197.30 0.1 3

JSO ( / Owr% ) 30 0.56 27.33 0.49 60 0.36 66.13 0.31 90 0.20 200.00 0.17

EJSO ( !Owr)%

5.6 mol% epox idi sed 30 0.69 18.00 0.60 60 0.38 65.58 O.JO 90 0.25 140.00 0.2 1

4.5 mol% epox idi sed 30 0.72 19.30 0.63 60 0.46 47 .26 0.40 90 0.32 73.24 0.28

Meral Soaps of EJSO ( Jwr% ) Barium soap 30 0.60 (0.65) 27.78 (33.67) 0.52 (0.57)

60 0.44 (0.55) 51.65 (33.06) 0 .38 (0.48) 90 0.26 (0.30) 13 1.51(1 11. 10) 0.23 (0.26)

Cadmium soap 30 0.77 (0.77) 17.68 (16.68) 0.67 (0.67) 60 0.42 (0.54) 56.69 (34.29) 0.37 (0.47) 90 0.27 (0.40) 137. 17 (62 .50) 0.23 (0.35)

Lead soap 30 0.70 (0.70) 20.4 1 (20.41) 0.61 (0.60) 60 0.42 (0.59) 56.69 (28.73) 0.37 (0.42) 90 0.32 (0.37) 97.65 (73.05) 0.27 (0 .29)

Zinc soap 30 0.66 (0.69) 27.78 (2 1.00) 0.57 (0.60) 60 0.41 (0.48) 59.49 (43.40) 0.36 (0.42) 90 0.36 (0.33 ) 77.16 (91.83) 0.3 1 (0.29)

Values obtained in the presence of meta l soaps of EJSO in parenthesis

194

Okieimen: Utili sa ti on of Jatroph Seed Oil aga inst Thermal Degradation of PVC Articles

0-7

0 6

p '$_0 ·4 £

o .1 L----::~-::--_.._JL:---+;;--;:';:;----:'Io~o--' 20 40 60 so 1

Composition (WI '/, cadmium soap)

Fig. 4-Thermoxidat ive degradation o f PVC at 190°C in the presence of mixtures of barium and cadmium soaps of JSO. Variation of relati ve intrinsic viscosity with composition of soap mi xture. [11)/[lllo vs composition (wt% cadmium soap)

11-5,...----------------.

8. 0 L---='::----L-~-:::----=--:-~:::-' 20 40 60 so 100

Composition (wt '!. cadmium soap) ·

Fig. 5-Thermox idat ive degradatio n of PVC at 190°C in the presence of mi xtures of barium and cadmium soaps o f JSO. Variation of re lati ve iodine values with compositi on of soap mi xture. (IV)]/(IV)0 vs composition (wt% cadmium soap)

in the degraded polymer sample should provide satisfactory estimate of the extent of degradation. The ratio of the iodine value of degraded PVC to the value of undegraded sample (IV)/(JV)0 has been used to assess the relative effect of the JSO additives on the

thermal degradation of PVC: the lower the (TV)/(IV)0

value, the greater the extent of degradation. The results in Fig. 5 show that the level of unsaturation in the degraded PVC samples decreases with increase in the cadmium soap content of the soap mixtures and that the PVC samples degraded in the presence of the soap mixture with 90wt% cadmium soap gave the lowest levels of unsaturation. When compared with the values obtained for PVC samples degraded in the absence of the metal soaps of JSO ((JV)/(IV)0 is about 18.0), these results indicate reductions of up to 80% in the level s of unsaturation in PVC samples degraded in the presence of mixtures of barium and cadmium soaps of JSO. It can be seen from Fig. 5 that mixtures of barium and cadmium soaps of JSO exerted a synergistic stabilising effect on the thermoxidati ve degradation of PVC. It would seem that as with nonoxidative degradation, the reaction sequence involving the soap mixture and the polymer matrix attained optimum effectiveness at a cadmium soap to barium soap ratio in the mixture of 9: I .

Conclusion This study examined the physico-chemical

properties and fatty acid profile of Jatropha seed oil and the effect of its derivatives (epoxides and metal soaps) on the nonoxidative and oxidative thermal degradation of PVC using rate measurements and changes in the intrinsic viscosity and level of unsaturation in the degraded polymer samples. The data from this study are corroborative and show that the derivatives of JSO examined are effective in suppressing the rate of dehydrochlorination and in reducing the extent of degradation of the polymer. The suggested practical application of JSO additive as thermal stabiliser in PVC formulations is an important first step towards a fuller exploitation of the resources of Jatropha multifida.

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