Activated Anionic Polymerization of Îµ-Caprolactam for RIM Process

11 Activated Anionic Polymerization of ε-Caprolactam for RIM Process GIOVANNI CARLO ALFONSO, CARMEN CHIAPPORI, SANDRO RAZORE, and SAVERIO RUSSO

Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: January 8, 1985 | doi: 10.1021/bk-1985-0270.ch011

1

Centro Studi Chimico-Fisici di Macromolecole Sintetiche e Naturali, C.N.R., Corso Europa 30, 16132 Genoa, Italy

The role of initiator and activator concentrations on the whole process of ε -caprolactam anionic polymerization has been explored, with the aim of selecting the most suitable experimental conditions for the RIM process. The effects of the active species on high polymer yield, residual monomer content, higher oligomers and side products have been evaluated. It has been found that polymer molecular masses and their distributions are related to both active species in a complex manner. Under specific experimental conditions, i t is however possible to predict their values in a relatively large range of average masses. Side reactions and structural irregularities in the polymer chains have been correlated to the absolute and relative concentrations of activator and initiator, in order to minimize their extent. The effect of active species on the overall polymerization time as well as on the initial and maximum rates of polymerization has been evaluated. In recent years the a c t i v a t e d a n i o n i c p o l y m e r i z a t i o n of ε-caprolactam (CL) in b u l k , in the presence of some inorganic s a l t s , has been the subject of a thorough i n v e s t i g a t i o n by our research group ( 1 - 6 ) . Indeed, some 1

Author to whom correspondence should be addressed.

0097-6156/ 85/ 0270-0163S06.00/ 0 © 1985 American Chemical Society

In Reaction Injection Molding; Kresta, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.


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h a l i d e s such as l i t h i u m and calcium c h l o r i d e are able to modify and improve many bulk p r o p e r t i e s of the r e s u l t a n t poly( ε - c a p r o l a c t a m ) (PCL). For i n s t a n c e , they can induce an increase of polymer d e n s i t y , glass transition temperature, Young's modulus and melt v i s c o s i t y , as well as a decrease of i t s melting temperature, degree of c r y s t a l l i n i t y and c r y s t a l l i z a t i o n r a t e . At present, attempts to polymerize CL added with various fillers, reinforcing agents and p r o p e r t y - m o d i f i e r s are explored by us i n great d e t a i l ( 7 , 8 ) . The aim i s to synthesize polymer blocks where the a d d i t i v e , d i s s o l v e d or finely dispersed i n the monomer medium, remains homogeneously d i s t r i b u t e d throughout the polymer m a t r i x . Indeed, if the p o l y m e r i z a t i o n k i n e t i c s i s not adversely a f f e c t e d by the a d d i t i v e , the very short p o l y m e r i z a t i o n time and the r a p i d increase of the medium v i s c o s i t y prevent any coarse aggregation of the a d d i t i v e and the consequent phase separation i n large domains. T h e r e f o r e , at l e a s t in p r i n c i p l e , the above process may represent a very easy way to produce polymer mixtures, blends and composites based on PCL, with som p e c u l i a r morphologies and p r o p e r t i e s . Quite r e c e n t l y , the a c t i v a t e d a n i o n i c p o l y m e r i z a t i o n of CL has been found s u i t a b l e f o r the r e a c t i o n i n j e c t i o n molding (RIM) technology (9-12) and has prompted some new studies (13-15) devoted to update the c l a s s i c a l p i c t u r e of the r e a c t i o n k i n e t i c s (J_6), mostly in terms of potential industrial a p p l i c a t i o n s of the RIM process (13-15,17-20). Successful attempts by Hedrick et al . (11,12) to a n i o n i c a l l y synthesize a s e r i e s of PCL block copolymers has led to impact-modified RIM nylon (Monsanto's NYRIM). The p o s s i b i l i t y to u t i l i z e the RIM technology f o r the synthesis of PCL-based m a t e r i a l s r e q u i r e s a careful control of many r e a c t i o n parameters, which strongly affect the whole k i n e t i c course of the p o l y m e r i z a t i o n as well as the p r o p e r t i e s of the r e s u l t a n t m a t e r i a l . It i s well known, indeed, that the a n i o n i c p o l y m e r i z a t i o n of CL i s c o n s t i t u e d of a complicated set of main and side r e a c t i o n s , g i v i n g r i s e to a v a r i e t y of a c t i v e species and irregular structures in the polymer chains (JL6). Our study has been focused on the r o l e played by a c t i v a t o r and i n i t i a t o r c o n c e n t r a t i o n in determining the optimum c o n d i t i o n s f o r the p o l y m e r i z a t i o n of CL i n the mold. To our knowledge no such study has been published so f a r , at l e a s t under experimental c o n d i t i o n s s u i t a b l e f o r RIM. We report here the f i r s t part of our study, r e l a t e d to the


11. ALFONSO ET AL.

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polymerization of neat CL. The e f f e c t s of various a d d i t i v e s on the p o l y m e r i z a t i o n k i n e t i c s at 'optimum' c o n d i t i o n s are i n progress and w i l l be given elsewhere (21). We have c a r r i e d out a s e r i e s of p o l y m e r i z a t i o n runs in q u a s i - a d i a b a t i c c o n d i t i o n s , as described in Ref. 3, at different c o n c e n t r a t i o n s of both i n i t i a t o r and a c t i v a t o r , so that not only t h e i r absolute amounts but also t h e i r relative r a t i o s were widely m o d i f i e d . Experi mental Sodium caprolactamate (prepared i n s i t u from sodium metal and CL) and N-acetyl caprolactam were chosen as i n i t i a t o r and a c t i v a t o r , r e s p e c t i v e l y . The s t a r t i n g temperature of p o l y m e r i z a t i o n was 1 5 5 ° C A double-walled glass r e a c t o r , of about 60 c m , equipped with mechanical s t i r r e r , i n e r t gas i n l e t and o u t l e t and thermocouple lodging was used (3_). The polymerization products were f r a c t i o n a t e d f o l l o w i n g the published l i t e r a t u r e (b) i n t o high polymer, r e s i d u a l monomer, higher oligomers and low molecular mass side products, and their r e s p e c t i v e y i e l d s were determined. Monomer content has also been evaluated by g.l . c . A thermokinetic a n a l y s i s of the p o l y m e r i z a t i o n runs has enabled us to evaluate both enthalpy and instantaneous r a t e of p o l y m e r i z a t i o n , f o l l o w i n g the procedure described in Ref. 3. Molecular mass d i s t r i b u t i o n of PCL has been determined by GPC of the corresponding t r i f 1 u o r o a c e t y 1 d e r i v a t i v e s by using the method described i n Ref. 22. A s o l u t i o n of N-TFA d e r i v a t i v e s at c=0.2 g/dl was prepared, adding o-dichlorobenzene as internal standard (1 yl/ml s o l u t i o n ) . 25 μ 1 of the s o l u t i o n were i n j e c t e d i n a Waters High Pressure L i q u i d Chromatography apparatus (pump 6000 A, i n j e c t o r U6K, UV detector 440, μ - s t y r a g e l columns s e t : 1 0 - 10*- 1 0 - 500 Â ) , λ=254 nm, flow r a t e : 1 ml/min). UV absorption spectra of 1% (w/w) PCL s o l u t i o n s in anhydrous formic acid have been recorded with a Cary UV spectrophotometer mod. 219. For a l l samples, band maximum at 275-277 nm has been found, at variance to previous analyses of PCL samples synthesised under different experimental c o n d i t i o n s (J_). 3

s

s


166



Results and D i s c u s s i o n Mass balances of the p o l y m e r i z a t i o n products have been performed f o r the whole set of p o l y m e r i z a t i o n r e a c t i o n s , where both the i n i t i a t o r and a c t i v a t o r concentrations have been v a r i e d from 0.3 to 1.5 moles over 100 moles of CL. In Table I the data r e l a t e d to the maximum monomer conversion and the high polymer y i e l d are given as f u n c t i o n s of the a c t i v e species c o n c e n t r a t i o n ( i n i t i a t o r and activator), which are present in equimolar amount i n the polymerizing mixture. For almost a l l systems, monomer conversion and polymer y i e l d are higher than 98 and 95%, respectively. In such c o n c e n t r a t i o n range of a c t i v e s p e c i e s , y i e l d f l u c t u a t i o n s are l e s s than 1.5% i n terms of monomer conversion and l e s s then 2.0% f o r the high polymer y i e l d . Also f o r a c t i v a t o r concentrations higher than those of initiator, the y i e l d data are c l o s e to the above v a l u e s , as evidenced i n Table II. Only f o r very low i n i t i a t o r concentrations ( l e s s than 0.3%) there i s a dramatic decrease of the high polymer y i e l d . Very few runs have been performed using a c t i v a t o r c o n c e n t r a t i o n s lower than those of the i n i t i a t o r (see Table III), because of the claimed adverse effects, caused by the strong b a s i c i t y of the medium, on the structural homogeneity of the polymer. It i s well known, indeed, that C l a i s e n - t y p e condensation r e a c t i o n s on the performed polymer are induced by a strong base and are responsible for the formation of structural irregularities along the c h a i n , i . e . of groups which are able to s t r o n g l y absorb i n the UV region (J_6) and represent p r e f e r r e d degradation s i t e s . We w i l l d i s c u s s the behaviour of our PCL samples i n t h i s respect l a t e r on. It can be n o t i c e d , n e v e r t h e l e s s , that -even i n excess initiator c o n c e n t r a t i o n s both monomer conversion and high polymer y i e l d show values only s l i g h t l y lower than those quoted i n the previous t a b l e s . In crude terms of conversion, therefore, i t can be i n f e r r e d that a rather large range of a c t i v e species concentrations can be explored without any s i g n i f i c a n t worsening of the a t t a i n a b l e conversion v a l u e s . Molecular Mass D i s t r i b u t i o n The molecular mass e v a l u a t i o n of a l i p h a t i c polyamides as well as the determination of t h e i r molecular mass distribution are relevant problems which only very


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Table I. Monomer Conversion and High Polymer Yield in Polymerization Runs with Equimolar Concentrations of Initiator and Activator

[A] = [I]


(mol/100 mol CL) 0.3 0.5 0.6 0.7 0.9 1 .2 1.5

Table II.

Monomer Conversion (λ) %

97.9 98.6 98.2 98.2 98.2 98.3 98.2

High PolymerYield %

95.0 95.7 95.6 95.6 95.6 95.5 95.4

Monomer Conversion and High Polymer Yield in Polymerization Runs Where [A]/[I] >, 1

[A] / [I] (mol/100 mol CL) 0.6/0.1 0.6/0.15 0.6/0.2 0.6/0.3 0.6/0.4 0.6/0.6 0.7/0.4 0.7/0.6 0.7/0.7 0.8/0.4 0.8/0.6 0.8/0.7 0.9/0.6 0.9/0.7 0.9/0.9 1.0/0.6 1 .0/0.7 1 .2/0.6 1.2/0.9 1.2/1.2 3.0/0.6

Monomer Conversion (λ) %

High Polymer Y i e l d

-

76.3 85.6 93.7 96.2 95.3 95.6 94.1 96.1 95.6 93.5 96.1 96.1 97.3 95.2 95.6 96.2 95.6 96.0 95.7 95.5 88.3

98.2 98.2 96.7 98.4 98.2 96.6 98.4 98.8 97.8 98.5 98.2 98.5 98.1

-

98.7 98.3

-

%


REACTION INJECTION MOLDING

168

recently have been s a t i s f a c t o r i l y s o l v e d ( 2 2 - 2 5 ) . The aforementioned N-trif1uoroacety1ation r e a c t i o n runs as f o l 1ows:


(1) Complete s u b s t i t u t i o n of the nitrogen-bonded hydrogen and easy r e p r o d u c i b i l i t y are the most r e l e v a n t aspects of the above r e a c t i o n . The N-trif1uoroacetylated d e r i v a t i v e of PCL i s q u i c k l y s o l u b l e in many solvents (such as acetone, THF, dioxane, chlorinated hydrocarbons, etc.) and can e a s i l y be analyzed by conventional GPC apparatus. P r e l i m i n a r y data on MMD of our samples are given in Table IV. It i s evident that equimolar concentrations of activator and initiator produce PCL polymers c h a r a c t e r i z e d by a r e g u l a r l y decreasing p o l y m o l e c u l a r i t y index Q, from c a . 2.6 to 2.0. In Figure 1 the number of polymer molecules formed per acyllactam molecule i s p l o t t e d as a f u n c t i o n of i n i t i a t o r concentration . The actual values should be compared to the ' t h e o r e t i c a l ' value of 1, which corresponds to the assumption that the number of macromolecules would be equal to the number of a c y l l a c t a m molecules (26J, as in the i d e a l case of a s t e p - a d d i t i o n of lactam anions to a constant number of growth c e n t e r s . It i s evident t h a t , by i n c r e a s i n g [I] at equimolar concentrations of a c t i v e s p e c i e s , there i s a r e g u l a r decrease in the number of polymer molecules Ν per a c t i v a t o r molecule. Moreover, a l l experimental values of [N] / [A] are lower than 1, i n the [I] range from 0.5 to 1.5 mole %. E x t r a p o l a t i o n to i n f i n i t e d i l u t i o n of caprolactam anions shows a c o n s i s t e n t cohincidence with the c a l c u l a t e d value of 1, in f u l l agreement with theory. From the above data i t i s evidenced t h a t , i n the experimental range of i n i t i a t o r concentrations we used, polymer molecular masses are higher than expected. Indeed, a d d i t i o n a l growth c e n t e r s , i.e. new polymer c h a i n s , can be produced by d i s p r o p o r t i o n a t i o n r e a c t i o n s such as the f o l l o w i n g one, induced by strong bases: •CO-N—CO

+

Θ

ΝΗ


(2)

11. ALFONSO ET AL.


Table I I I .

[A] /

169

Activated Anionic Polymerization of e-Caprolactam

Monomer Conversion and High Polymer Y i e l d i n Polymerization" Runs where [A]/[I]*1 Monomer Conversion High Polymer Y i e l d (λ)

[I]

(mol/100 mol CL)

[A] / [I] (mol/100 mol CL) 0.5/0.5 0.7/0.7 π η/π π 0.9/0.9 1.2/1 .2 1.5/1.5

95.6 94.9 94.9 93.6 95.6 95.2

98.2

0.6/0.6 0.6/0.9 0.6/1 .2 0.6/1 .8 0.7/0.7 0.7/0.9

Table

%

%

-

98.2 98.2

IV.

GPC Data on PCL Samples — -3 Mn-10

27.04 19.74 /16.77 \l7.42 14.40 14.34

3 — Mw-10

70.63 46.09 Γ39.32 \38.37 32.42 29.25


Q

2.61 2.33 Î2.34 \2.20 2.25 2.04



_J

0.2

I

I

I

I

0.6

1.0

I

1

L

U

[l] [mol /o] ;

e

Figure 1. Number of polymer molecules formed per acyllactam molecule, as a function of initiator concentration in the case [I] = [A].


11. ALFONSO ET AL.

Activated Anionic Polymerization of crCaprolactam

whereas C l a i s e n - t y p e condensation r e a c t i o n s , such those involving the following speci es ( 1_6 ), r e s p o n s i b l e f o r an increase of molecular masses:

171

as are


•CH-CO-N—CO or

Actual balance between the two opposite e f f e c t s determine the average value of polymer molecular mass and i t s distribution. From our data i t seems that the p r e v a i l i n g e f f e c t i s caused by type (3) r e a c t i o n s , which are more and more r e l e v a n t as b a s i c i t y of the medium i s i n c r e a s e d . Side Reactions and S t r u c t u r a l

Irregularities

As already mentioned, the a c t i v e species (imide groups and lactam anions) undergo a s e r i e s of side r e a c t i o n s , which induce the formation of i r r e g u l a r u n i t s along the chains. Not only the r e g u l a r i t y of the chains i s affected, but also the whole p o l y m e r i z a t i o n process as well as the polymer end p r o p e r t i e s are markedly modified (Jj5) . The s t r u c t u r e s , a r i s i n g from the aforementioned C l a i s e n - t y p e condensation r e a c t i o n s , are very r e a c t i v e : on one hand, they r e - c r e a t e growth centers and, on the other, they are r e s p o n s i b l e f o r the formation of heterogeneous groups, such as d e r i v a t i v e s of i s o c y a n a t e s , u r a c i l , malonamide, e t c . , which act as c o l o r centers and i n v e r s i o n points of chain r e g u l a r i t y . As a consequence, together with l i n e a r c h a i n s , branched and c r o s s l i n k e d s t r u c t u r e s are also formed. They s t r o n g l y a f f e c t molecular masses, MMD, and s o l u t i o n p r o p e r t i e s . Moreover, these n o n - c r y s t a l l i z a b l e u n i t s cause a decrease of both the polymer melting temperature and the crystallization rate, as well as a poorer thermo-oxidative s t a b i l i t y (16). In order to minimize these e f f e c t s , which may be r e l e v a n t a l s o to RIM technology, we have studied the r o l e of a c t i v e species concentration on the UV absorption spectra of the r e s u l t a n t polymer. The data are given i n Figures 2 and 3, where the e f f e c t s of equimolar and non-equimolar concentrations of a c t i v e s p e c i e s , r e s p e c t i v e l y , are shown. In Figure 2 the UV absorption c o e f f i c i e n t of PCL samples appears to be a l i n e a r f u n c t i o n of each a c t i v e species



172


0.2

0.6

1.0

U

[l].[mol%]

Figure 2. Optical density of PCL samples at λ= 276 nm as a function of initiator concentration, in the case [I] = [A].


ALFONSO ET AL.


[A] mol /.


e

U

I

0.2

I

I

I

I

0.6

1.0

ι

ι 1.4

ι

I

[l].[mol /o] e

Figure 3. Effect of activator concentration, as constant [ I ] , on polymer optical density at λ= 276 nm. a) [I] = 0.4; b) [I] = 0.6; c) [I] = 0.7; d) [I] = 0.9.



174


c o n c e n t r a t i o n in the range between 0.3 and 1.5 mole %. It i s reasonable to assume that the UV absorption i s directly proportional to the t o t a l amount of side products a r i s i n g from the C l a i s e n - t y p e condensation r e a c t i o n s , which are c a t a l y z e d by strong bases. Thus, the a b s c i s s a i s f o r m a l l y expressed i n terms of i n i t i a t o r c o n c e n t r â t i ons. In Figure 3 the e f f e c t of a c t i v a t o r c o n c e n t r a t i o n on the UV absorption c o e f f i c i e n t of our polymer samples, at constant [I] , i s g i v e n . Almost p a r a l l e l l i n e s , well joined to the i n t e r p o l a t e d values on the equimolar c o n c e n t r a t i o n l i n e , have been found. From the whole set of above data i t can be i n f e r r e d t h a t , by s u i t a b l y p l a y i n g with appropriate c o n c e n t r a t i o n s of the a c t i v e s p e c i e s , i t i s p o s s i b l e to reduce the amount of s t r u c t u r a l i r r e g u l a r i t i e s along the c h a i n . Polymeri ζ ation K i n e t i c s The whole p o l y m e r i z a t i o n k i n e t i c s has been followed by means of the a d i a b a t i c r e a c t o r method ( 3 , 6 ) , which allows to simultaneously determine p o l y m e r i z a t i o n times and rates. In Table V d a t a , r e l a t e d to the overall p o l y m e r i z a t i o n time, tp , as well as to the i n i t i a l and maximum rates of p o l y m e r i z a t i o n , are g i v e n . A l l these parameters are, of course, very r e l e v a n t to RIM technology. In Figure 4 the o v e r a l l p o l y m e r i z a t i o n time i s p l o t t e d as a function of one or the other a c t i v e species c o n c e n t r a t i o n . A h y p e r b o l i c type dependence of t on [active species] i s e v i d e n t , with a very sharp decrease of tp i n the c o n c e n t r a t i o n range between 0.3 and 0.7 mole %, and a much slower decrease at higher c o n c e n t r a t i o n s . At the highest l e v e l s of a c t i v e species c o n c e n t r a t i o n s , t p is very low ( c a . 3 min) and t h i s value compares r a t h e r well with the usual r e a c t i o n times f o r the RIM technology. Non-equimolar concentration conditions roughly f o l l o w the same p a t t e r n , as evidenced from the data quoted i n Table V, and allow to underline the prominent r o l e of [I] on t , whereas [A] has a much lower relevance on i t . The i n i t i a l p o l y m e r i z a t i o n rates show a dependence on the first power of [A] and 0.9 power of [I] , as evidenced i n Figure 5. With only a few exceptions almost a l l the experimemtal points are well a l i g n e d on the s t r a i g h t line, passing through the o r i g i n . The 0.9 exponent indicates an almost complete d i s s o c i a t i o n of the p

p


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Table V. Overall P o l y m e r i z a t i o n Time, I n i t i a l and Maximum P o l y m e r i z a t i o n Rates i n Runs with D i f f e r e n t Amounts of A c t i v a t o r and I n i t i a t o r [A] / [I]

Overall Polym. I n i t i a l Rate Maximum Rate Time, t (dx/dt) -10 ( dx/dt ^ 1 0 (mol/100 mol CL) (min) (min" ) (min" ) 2

o

p

0.3/0.3 0.3/0.3 0.5/0.5 0.7/0.7 0.7/0.7 0.9/0.9 1.2/1 .2 1.5/1 .5 0.6/0.4 0.7/0.4 0.8/0.4 0.7/0.6 0.8/0.6 0.9/0.6 1.0/0.6 0.8/0.7 0.9/0.7 1.0/0.7 0.7/0.9 1.2/0.9

12 .05 11 .05 8 .10 4 .90 5 .40 3 .80 3 .70 3 .15 6 .50 9 .30 7 .85 6 .05 5 .60 5 .40 3 .95 5 .15 5 .70 4 .70 5 .15 5 .40

1

1

1 .95 1 .41 3.39 6.98 7.40 9.41 19.28 23.63 3.69 3.37 4.54 5.61 7.10 4.78 8.64 7.49 6.11 11.12 8.57 9.77

1

3.38 3.74 5.17 8.01 8.28 10.04 13.64 15.82 5.69 4.30 5.06 6.77 7.90 8.21 9.43 9.90 7.77 10.96 8.48 7.96



176 REACTION INJECTION MOLDING



ALFONSO ET AL.


Figure 5. Initial polymerization rate as a function of acti species concentration.



178

caprolactamate ' a l t i n our experimental c o n d i t i o n s , at variance with previous f i n d i n g s ( 1 6 ) . From the data of Table V i t i s also evident that the maximum polymerization rates in quasi-adiabatic conditions are 10-20 times higher than the i n i t i a l r e a c t i o n s r a t e s . At i n c r e a s i n g concentrations of the a c t i v e s p e c i e s , the r a t i o between the two rates r e g u l a r l y decreases.


Cone!usions The RIM process f o r m a t e r i a l s based on PCL r e q u i r e s a stringent control of the many r e a c t i o n parameters which strongly a f f e c t the whole pattern of the a c t i v a t e d a n i o n i c polymeri z a t i on. Among these parameters, i n i t i a t o r and a c t i v a t o r c o n c e n t r a t i o n s play a very r e l e v a n t r o l e . The present study underlines t h e i r i n f l u e n c e on the p o l y m e r i z a t i o n k i n e t i c s and polymer p r o p e r t i e s . 'Optimum' c o n d i t i o n s f o r each of the f o l l o w i n g aspects have been found: high polymer y i e l d , maximum monomer conversion, initial and maximum rate of p o l y m e r i z a t i o n , overall time of p o l y m e r i z a t i o n , polymer molecular mass and i t s d i s t r i b u t i o n , side r e a c t i o n s and i r r e g u l a r structures. Other r e l e v a n t parameters, such as v i s c o s i t y r a i s e and crystallization rate,which are c u r r e n t l y explored by other research groups (13,15), w i l l be the subject of future s t u d i e s on our experimental system, i n the presence of various added substances. ReteasLcfi

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Literature Cited 1.

2. 3. 4. 5.

Bonta', G.; Ciferri, Α.; Russo, S. "Ring Opening Polymerization"; Saegusa, T.; Goethals, L . , Eds.; ACS SYMPOSIUM SERIES No. 59: Washington, D.C., 1977; p. 216. Costa, G.; Pedemonte, E . ; Russo, S.; Sava', E. Polymer 1979, 20, 713. Alfonso, G. C.; Bonta', G.; Russo, S.; Traverso, A. Makromol. Chem. 1981, 182, 929. Alfonso, G. C.; Pedemonte, E.; Russo, S.; Turturro, A. Makromol. Chem. 1981, 182, 3519. Biagini, E . ; Pedemonte, B . ; Pedemonte, E.; Russo, S.; Turturro, A. Makromol. Chem. 1982, 183, 2131.


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6. 7. 8.


9. 10. 11. 12. 13. 14. 15. 16.

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Alfonso, G. C.; C i r i l l o , G.; Russo, S.; Turturro, A. Eur. Polym. J. 1983, 19, 949. Alfonso, G. C., Costa, G.; Pedemonte, Ε.; Russo, S.; Turturro, A. Proc. 5th AIM Meeting, Milan, 1981. Russo, S. Proc. IUPAC 28th Macromolecular Symp., Amherst, 1982. Kubiak, R. S.; Plast. Engng. 1980, 36, 55. Kubiak, R. S.; Harper, R. C. Reinf. Plast./Composites Inst., 35th Annual Conf., 1980, Sec. 22-C, p. 1. Hedrick,R. M.; Gabbert, D. Α. I. Ch. E. Symp., Detroit, 1981. Gabbert, D.; Hedrick, R. Μ. Α. I. Ch. E. Symp., Detroit, 1981. Sibal, R. E . ; Camargo, R. Ε.; Macosko, C. W. Int. J. Polym. Techn. Eng. Polym. Process. Eng., in press. Russo, S. Proc. 5th AIM Summer School on Polymer Processing, Gargnano, 1983; p. 289. Camargo, R. E . ; Gonzales, V. M.; Macosko, C. W.; Tirrel, M. Rubber Chem. Techn. 1983, 56, 774 Šebenda, J. In "Comprehensive Chemical Kinetics"; Bamford, C. H.; Tipper, C. F., Eds.; Elsevier: Amsterdam, 1976; Vol. XV, Chap. 6, 'Lactams', p. 379ff. Alfonso, G. C.; Russo, S.; Pedemonte, E.; Turturro, Α.; Puglisi, C. Italian Pat. 21912A/83 (to C.N.R.). Russo, S.; Alfonso, G. C.; Pedemonte, E.; Turturro, Α.; Martuscelli, E. Italian Pat. 21950A/83 (to C.N.R ). van der Loos, J. L. M.; van Greenen, A. A. ACS PMSE Proc. 1983, 49, 549. Biagini, E.; Razore, S.; Russo, S.; Turturro, A. ACS Polymer Preprints, 1984, 25 (1), 208. Russo, S.; et al., to be published Biagini, E.; Gattiglia, E.; Pedemonte, Ε.; Russo, S. Makromol. Chem. 1983, 184, 1213. Schuttenberg, H.; Schulz, R. C. Angew. Chem. 1976, 88, 848. Jacobi, E.; Schuttenberg, H.; Schulz, R. C. Makromol. Chem. Rapid Comm. 1980, 1, 397. Weisskopf, K.; Meyerhoff, G. Polymer 1983, 24, 72. Šebenda, J . ; Kouřil, V. Eur. Polym. J . 1971, 7, 1637.

RECEIVED June 14, 1984


Activated Anionic Polymerization of Îµ-Caprolactam for RIM Process

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