Development of Extrusion Instabilities and Surface Irregularities

8/14/2019 Development of Extrusion Instabilities and Surface Irregularities

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" D e v e l o p m e n t o f E x t r u s i o n I n s t a b i li t ie s a n d S u r f a c eI r r e g u l a r i ti e s o f E x t r u d a t e s o f P o l y m e r M e l t s a n d F i l le d

P o l y m e r s "

Dilhan M . Kalyon , E lvan B ir inc i and Hal i l Gevgi l i l i

H igh ly F i l led M ater ia ls Ins t itu teS tevens Ins t i tu te o f Tec hnology

Castle Point Stat ion, Hoboken, NJ 07030* [email protected], 201 216 8225


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SynopsisThis s tudy i s a con t inua t ion o f an ea rl i e r s tudy [Ka lyon and Ge vg i l i li ( 2003) ] and a ims a tp rob ing the e f f ec t s o f the f low bou ndary cond i t ion a t the wa l l on the dev e lopm en t o f fl owins t ab il i ti e s and ex t ruda te su r f ace i r regu la r i ti e s upon the ex t rus ion o f po lym er mel t s andpo lym er i c suspens ions . T he wa l l s l i p and f low ins t ab i l it y beha v io r o f two po lymer s , i .e .,a po ly (d imethy l s i l oxane) , PDMS and an oxe tane based a l t e rna t ing b lock the rmo p las t i ce l a s to m e r B A M O / A M M O - T P E w e r e s t u d i e d a lo n g w i t h th e w a l l s li p a n d f lo w i n s t ab i li tybehav io r o f PD M S f i ll ed wi th 10, 20 , 40% by vo lum e o f ho l low g lass spheres and 60%b y v o l u m e o f K C 1 F i ll e d B A M O / A M M O - T P E . S t e a d y t o rs i o n al f l o w w a s u s e d incon junc t ion wi th the s t r a igh t - l i ne marker t echn ique to ana lyze wa l l s l i p in s t eadyto r s iona l f l ow. Thermal imag ing and h igh - speed c inematography were used wi thcap i l l a ry flow to charac t e r i ze the su r f ace f ea tu res o f ex t ruda tes eme rg ing f rom cap i l l a ryd ies . The e f f ec t s o f t he convergen ce ang le f rom the r ese rvo i r i n to the cap i l l a ry d i e werea l so inves t iga t ed (15 , 45 and 75 ) f o r pu re PD M S and 10% g lass f il l ed PDM S. The ang leo f convergenc e had no e f fec t on the deve lopm en t o f su rf ace i r r egu la r i ti e s . T he


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r ise to f low instabil i t ies and surface irregulari t ies during extrusion. These results suggestthat the mecha nism s for the developm ent o f surface irregulari t ies of the extrudates ofpo lymer ic suspens ions d i f fe r f rom those o f the b inder phase . Dep ending on the b inder o fthe suspension and with the appropriate type and concentrat ion of the r igid f i l ler phase,the incorporation of the r igid f i l lers can prevent or induce the formation of surfaceirregulari t ies in extrudates o f polym eric suspensions.

K e y words" f low instabil i t ies, w all s l ip , extrudate , and surface irregulari t ies


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I N T R O D U C T I O N

The dev e lopm ent o f surface d i s tor t ions in the ex t ruda tes of po lym er me l t s em erg ing f romextrus ion dies (descr ibed as mel t f rac ture , shark skin, gross surface i r regular i t ies) is animpo rtant industr ia l problem . The ini t ia tion on extrudate dis tor t ions presents an upp erl imi t to the manufac tur ing r a te in ex t rus ion based process ing o f po lym ers and polymer icsuspensions . Consis tent with i ts industr ia l importance i t has rece ived s ignif icantacademic and indus t r i a l a t t en t ion [Benbow and Lamb (1963) ; Pe t r i e and Denn (1976) ;La r son (1992) ; Den n (2001) ; K a lyon and G evgi l i li (2003)] .

Var ious polymer melts , espec ia l ly l inear polymers , exhibi t wal l s l ip [Awati e t a l . (2000) ;Ha tz ik i r i akos and Dea ly (1991) ; Gevgi l i l i and Ka lyon (2001) ; R ie l ly and Pr ice (1961) ;Ka l ika and Denn (1987) ; Ramamur thy (1986) ; Chen e t a l . (1993) ; Migle r e t a l . (1993) ;Mi. ins tedt e t al . (2000)] an d wal l s l ip is considered to be on e o f the ma jor fac tors w hichcan affec t the formation o f extrudate dis tor t ions . Kiss i and Piau (1990) carr ied out f low


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e t al ( 1993) have de te rmine d a sharp t rans i t ion be tw een a r eg ime o f weak s l ip and one o fs t rong s l ip as the shear r a t e i s i nc reased dur ing s imple shear in which the ve loc i tyd i s t r ibu t ion i s d i rec t ly mea sured w i th in the 100 nm of the wal l. The t r ans i t ion f rom w eakto s t rong s l ip in s imple shear i s cons idered to occur a t a mate r i a l -dependen t wal l shears t ress , va lue o f which depends on the su rf ace dens i ty o f su r f ace-anchored cha ins (Leger ,Herve t and Massey , 1997) . Here in th i s paper wal l s l ip i s t aken to be synonymous wi ths lip which can be de tec ted w i th macroscop ic means , i .e ., t h rough the depe ndence o f thef low curves on the su r f ace to vo lum e r a tio o f the rheom eter (Mo one y method) [Moo ney(1931) ; Yi lmazer and Kalyon (1989) ; Ka lyon e t a l . ( 1999) ] o r th rough the de tec t ion o fmm -sca le d i scon t inu i t ies a t the f r ee su r f ace o f the me l t and the edges o f the f ix tu res usedin s t eady to r s iona l f low upon fo l lowing a marker l i ne [Kalyon e t a l . ( 1993) ; Ara l andKalyon (1994) ] .

Recen t ly , Ka lyon and Gevg i l i l i ( 2003) have focused on the wal l s l ip and f low ins t ab i l i t ybehav io r o f th ree po lym ers , two o f wh ich ex h ib i t eas i ly de tec tab le wal l s l ip in s imple


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consisted of spherical hollow glass particles with a specific gravity of 1.09 and anar i thmetic mean par t ic le diameter o f 12 ~tm (Pot ters Industry) . For BA M O/A M M O a KC1filler with approximately cubical particle shape was used.

Experimental Apparati and ProceduresAn Advanced Rheometr ic Expansion System (ARES) rheometer , f rom Rheometr icScientific, Inc., Piscataway, NJ, was utilized in conjunction with steady torsional flowusing cone-and-plate and paral le l -disk configurat ions . The environmental chamber wasequipped with an im aging windo w and auxi l iary optics for cont inuous m onitor ing of thefree surface of the specim en [Aral and Kaly on (1994); G evgilili and Kalyon (2001)] Ahigh-speed cam era, capable of recording at f ilming speeds as high as 2 ,000 frames persecond, was part of the set-up shown in Figure 1.

During s teady torsional f low a s t raight- l ine ma rker was placed on the edges of thecone/plate an d the free surface of the polym er melt to enable the characterization of thewall slip velocity and the true deformation rate [Kalyon et al. (1993), Aral and Kalyon


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t empera tu r es to de t e rmine the con d i t ions u nder wh ich the ca t as t roph ic f a i lu re o f t he no -s l ip cond i t ion becam e apparen t .

An Ins t ron cap i l l a ry rheomete r was employed to co l l ec t add i t iona l shea r v i scos i ty da t aand to s tudy the deve lopmen t o f ex t ruda te d i s to r t ions upon ex i t f r om the d i e . Thed iamete r s , l eng th over t he d i amete r r a t io s and the converg ing ang le o f t he taperconnec t ing the r ese rvo i r o f t he ba r re l o f t he rheom ete r t o the s t r a igh t l and sec t ion o f t hecap i l l a ry d ie (F igure 3 ) were cha nged sys t emat i ca l ly . T he shapes o f the ex t ruded samples ,immedia t e ly upon ex t rus ion f rom the d i e , were cap tu r ed us ing a h igh - speed camera(F igure 4 ) to a l low the im med ia t e charac t e r i za t ion o f t he su r f aces o f the ex t ruda tes(F igure 5 ). The t em pera tu r e d i s t r ibu t ions o f t he ex t ruda tes em erg ing f rom the d i e werea l s o m o n i t o r e d u s i n g a T h e r m a C a m t h e r m a l i m a g i n g c a m e r a . A t y p i c a l i m a g e s h o w i n gthe t empera tu r e d i s t r ibu t ion on an ex t ruda te upon emerg ing f rom the d i e i s shown inF igure 4 to r e f l ec t the t em pera tu r e o f the mate r i a l a t t he d i e wa l l. T he t em pera tu r e o f t hemate r i a l imm edia t e ly upon ex i t p rov ided da ta on the e f fec t o f v i scous en ergy d i ss ipa t ion


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s t eady s t a t e va lues a re reached . In t h i s re l a t i ve ly sma l l shea r ra t e range t he shea r s t re s scu rves a re app ro x im a te ly pa ra l le l t o each o the r and do no t exh ib i t ove rshoo t s . T he t yp i ca lre su l t s o f t he s t ra igh t- l i ne marke r t echn ique co r re spo nd ing t o t h i s se t o f expe r imen t s a reshown in F ig . 7 . A t re l a t i ve ly sma l l shea r ra t e s t he s t ra igh t - l i ne marke r rema inscon t inuous and connec t s t he mov in g and s t a t i ona ry wa l l s . On the o the r hand , a t thehighe r she ar ra tes , for ex am ple , a t 40 s -1 the con t inui ty of the s t ra igh t - l ine m ark er i s los tdu r ing s t eady t o rs iona l f l ow . The fo rma t ion o f t he mm -sca l e d i scon t inu i ty a t the wa l l i si nd i ca t ive o f t he l o ss o f the wa l l s t i ck cond i t i on a t the wa l l " m acrosc op ic wa l l s l i p " . Onthe o the r hand , a t g rea t e r shea r ra te s t he occu r rence o f wa l l s l ip and t he even tua l e j ec t iono f t he spec imen f rom the gap fo rce the shea r s t re s s to dec rease upon rea ch ing m ax ima .Fo r PDMS the shea r s t re s s max imum a t wh ich wa l l s l i p i s i n i t i a t ed occu rs a round 0 .07M Pa a t 30C at a shear ra te of 40 s -~. This c r i t ica l shear s t ress valu e w as dete rm ined to bethe same a t 10 and 50 C a lso [Kalyon and Gevgi l i l i (2003)] .

The cap i l l a ry f l ow cu rve o f PD M S a t 30C i s shown in F igu re 8 . A t appa ren t shea r ra te s


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vo lum e r a t io o f t he cap i l l a ry d ie? D a ta co l l ec t ed a t t h ree d i f f e r en t cap i l l a ry d i e d i amete r sa r e shown in F igure 9 . The f low cu rves and the su r f ace topo log ies o f t he ex t ruda tes a r efound no t t o be a f f ec t ed by the su r f ace to vo lum e r a t io o f the d i e . Thus , r egard less o f thed iamete r o f t he d i e, t he wa l l shea r s t r ess a t wh ich the t r ans it i on to the uns t ab le r eg ion ( a twh ich the ex t ruda te su r face i s no longer smoo th ) co inc ides wi th the c r it i ca l shea r st r essr ange a t wh ich wa l l s l ip i s onse t under s t eady to r s iona l f l ow.

I s t he f low ins t ab i l it y beha v io r o f t he po lym er mel t a f f ec t ed by the con vergence ang le o fthe cap i l la ry d i e en tr ance? T he e f f ect o f t he convergence ang le f o r PD M S i s show n inF igure 10. Th i s t yp ica l beha v io r i nd ica t es t ha t t he f low cu rves and the de ve lopm en t o f thesu r f ace i r regu la r i ti e s a r e no t a f f ec ted by the converg ence ang le .

The s t eady to r s iona l f l ow be hav io r o f t he TPE (over a ve ry b road r ang e o f shea r r a t es upto 200 s ~ ) was ve ry d i f f e r en t t han PDM S. Eve n a t t he h ighes t shea r r a t es i nves t iga t ed thesamples o f TPE s t ayed in t ac t w i th in the gap , w i thou t any s ign o f wa l l s l ip , edge d i s to r tion


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t he ex t ruda tes o f the TPE w ere r e l a t ive ly smoo th and exh ib i t ed on ly non-per iod ic min orsur f ace b lemishes r egard les s o f the shear r a t e.

The gen era l t rend in the deve lopm ent o f flow ins t ab i li t ie s dur ing ex t rus ion o f po lym ermel t s invo lves the absence o f ex t ruda te su r f ace d i s to r t ions a t r e l a t ive ly low shearr a t e / s t r es s va lues ( a t which p resumably the wal l s l ip ve loc i ty i s neg l ig ib le ) on one handand a t r e l a t ive ly very h igh shear r a t e / s t r es s va lues a t which cor r espond ing ly h igh ( andpresumably s table) wal l s l ip veloci t ies exis t . This sugges ts that ext rudate dis tor t ions arel ess li ke ly to occur under cond i t ions in which a st ab le f low bou ndary c ond i t ion ex i s ts a tthe wal l ; whether i t i s e i ther a s table wal l s t ick or s table wal l s l ip condi t ion.

Filled Polymers:P D M S a n d T P E w e r e c o m p o u n d e d w i t h g l a ss s p h e re s a n d K C 1 , r e s p ec t iv e l y . F r o m e a r li e rs tud ies i t is know n tha t in the p resence o f the par t i c l es an apparen t s lip l ayer ( the Vandlayer ) fo rms a t t he wal l dur ing bo th s t eady to r s iona l and cap i l l a ry f lows [Yi lmazer and


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a p p a r e n t s h e a r r a t e r a n g e . S i n c e th e B A M A / A M M O T P E i s e n e r g e t ic i t w a s n o t p o s si b l et o m a k e a d d i t i o n a l s u p p o r t i n g m e a s u r e m e n t s , s o o u r a t t e n t i o n w a s t u r n e d t o P D M Sc o m p o u n d e d w i t h d i f f e ri n g c o n c e n t r a t io n s o f s p h e r ic a l g l a ss p a r t ic l e s . H o w w i l l t h eb e h a v i o r o f P D M S b e a f f e c t e d b y t h e p r e s e n c e o f ri g i d p a rt i c le s i n t h e 1 0 t o 4 0 % b yv o l u m e r a n g e ?

T h e t y p i c a l fl o w c u r v e s o f P D M S i n c o r p o r a t e d w i t h 1 0 % b y v o l u m e g l a s s c o l le c t e d w i t ht h r e e c a p i ll a r ie s w i t h t h e s a m e l e n g t h o v e r d i a m e t e r r a t io o f 4 0 b u t w i t h d i f fe r i n gd i a m e t e r s a r e s h o w n i n F i g u r e 1 2 . T h e i m a g e s p e r t a in to e x t r u d a te s e x t r u d e d a tapp rox im ate ly the s a me appare n t s hea r r a te o f abou t 30 to 50 s -~. Thus , a t the s a meapparen t s hea r r a te a l l o f the ex t ruda tes ex t rude d w i th ca p i l l a ry d ies w i th d i f f e r ingd iam ete r s e xh ib i t a s imi la r type o f s u r f ace i r r egu la r i ti e s .

F igu re 13 s how s a l l o f the po in t s on the f low cu rves a t w h ich e x t ruda te s u r f acei r re g u l a r it i e s w e r e o b s e r v e d ( a s in d i c a t e d b y t h e p r e s e n c e o f a r r o w s h e r e . ) T h u s , t h e


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are genera ted fo r the cap i l l a r i es wi th smal l e r d i amete r s a t cons tan t l eng th over thed iame te r r a tio , sugge s t ing tha t the suspens ion i s s lipp ing s t rong ly . The f l a t t en ing o f thef low curves a t t he h ighes t apparen t shear r a t es a t which wal l s l ip i s c l ea r ly observed i sa l so in t e r es t ing . Such f l a t t en ing i s genera l ly as soc ia t ed wi th p lug f low of the suspens ion[Kalyon et a l . (1993) ; Yaras et a l . (1994)] .

The wal l s l ip behav ior o f the suspens ions o f PD MS wi th 10, 20 and 40% by vo lu me g las spar t i c l es were inves t iga ted us ing s t eady to r s iona l f low. Genera l ly , t he re was widespreadwal l s l ip o f the suspens ion s amples . Ear l i e r exper imenta l ev idence sugges t s tha t the f lowins tab il i ti e s and ex t ruda te d i s to r tions occ ur under cond i t ions in wh ich the s t ab i l it y o f thef low boundary cond i t ion a t t he wal l i s pe r tu rbed [Atwood and Schowal t e r (1989) ] .Di s to r t ion- f r ee ex t ruda tes a r e ob ta ined when a s t ab le wal l s l ip cond i t ion , fo r exampleth rough the genera t ion o f an apparen t s l ip l ayer a t the wal l by coa t ing o f the wal l su r f aceswi th f luoroe las tomers , i s i n t roduced [Kis s i and P iau (1997) and Wang and Drda (1997) ] .One can su rmise tha t an apparen t wal l s lip me chan i sm i s a l so in t roduced upon the


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PD M S the ang l e o f convergenc e va lues be tw een 15 t o 75 do no t a f fec t t he deve lop me n to f t he ex t ruda t e d i s to r t i ons , sugges t i ng t ha t t he sou rce o f t he obse rv ed f l ow in s t ab i l i ti e sfo r bo th t he pu re PDM S and f i l led PDM S i s no t l i ke ly t o be re l a t ed t o t he dynam ics o f t heen t ry f l ow .

T h e f l o w c u r v e s o b t a i n e d f o r t h e s u s p e n s io n o f P D M S w i t h 2 0 % b y v o l u m e g l a ss a r eshown in F igu re 15 . The a r rows a re u sed aga in t o i nd i ca t e t ha t d i s t o r t ed ex t ruda t e s a reex t ruded under t ha t pa r t i cu l a r cond i t i on and t he absence o f an a r row ove r a g iven po in tsugges t s t ha t t he ex t ruda t e was sm oo th and f ree o f d i s to r ti ons . In com par i son t o 10%suspens ion t he range o f shea r ra t e s ove r wh ich f l ow in s t ab i l i t i e s a re obse rved i scons ide rab ly reduc ed a t 20% by vo lum e g l a ss (be twee n 100 to 1000 s -1) w i th noex t ruda t e d i s to r t ions obse rved be low an app a ren t shea r ra t e o f 100 s -~, rega rd l e ss o f t hed i am e te r o f t he cap i l l a ry d i e .

T h e f l o w c u r v e s o f th e 4 0 % b y v o l u m e g l as s s p h e re s i n c o r p o r a te d P D M S a r e s h o w n i n


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decreas ing o r be ing e l imina ted co mp le te ly wi th increas ing concen t r a t ion o f r ig idpar t ic les .

The occ ur r ence o f wal l s l ip i s c l ea rly su rmised by com par ing the da ta co l l ec ted a td i f fe r en t d i amete r s ( a t cons tan t l eng th ove r the d iamete r r a tio ). A s the d iam ete r inc reases(hence a decrease o f the su r face to vo lum e r a t io ) the wa l l shear s t r ess inc reasessugges t ing tha t the re i s s ign i f i can t wal l s l ip , wi th the s l ip ve loc i ty increas ing wi thincreas ing wal l shear s t r es s . Th i s i s cons i s t en t wi th our f ind ings f rom s t eady to r s iona lf low tha t sugges t tha t wal l s l ip p reva i l s over a b roader r ange o f shear r a t es as the par t ic l econcen t r a t ion increases . A ga in the f l a t ten ing o f the f low curves i s a p recur sor o f p lugf low, which r end er s the app l i ca t ion o f M oon ey ' s approach fo r the de te rm ina t ion o f thewal l s l ip ve loc i ti es i r r e levan t [Mo oney (1939) ; Yaras e t a l. ( 1994) ; Ka ly on (2003)] .

The com par i sons o f the behav ior o f the e f f ec ts o f incorpora t ion o f the r ig id par ti c l es in tothe po lymer mat r ix a r e more c l ea r ly s een in F igures 17-19 , which show the f low curves


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and character is t ics) in to the binder phase. This is an important f inding and can beexploited to our industr ia l advantage. Conv ersely , i f the extrudates of the binder phaseare smooth and dis tor t ion f lee , the incorporat ion o f r ig id part ic les can in troduce extrudatedis tor t ions. This is another important f inding and should be kept in mind especial ly whenpolymeric compounds are formulated to include various sol id ingredients . These resultsat tes t to the in t imate re la t ionship be twe en the wall s l ip of polym ers a nd polym ericsuspensions and the development of surface ir regular i t ies in their extrudates .Un derstand ing o f the factors that control the s tabil ity of the f low bou nda ry condit ion atthe wa l l can p rov ide a be tte r unders tand ing to the under ly ing me chan ism s o f thedevelopment of extrudate dis tor t ions.

Re f e r e n c e s

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Ba gley E. B., "End correct ions in the capi l lary f low o f poly ethylen e," J . Ap pl ied Physics28, 624-627 (1957).Ben bow , J . J . and P. Lam b, "Ne w asp ects of me l t fracture," SPE Tra nsact ions 3, 7-17(1963).Brochard , F. and P. G. de Gennes,Langm ui r 8, 3033-3037 (1992).

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Gevgili l i , H. and D . M . Kalyon, "Step st rain f low: wal l s l ip effects and other errorsources," J. Rheol. 45, 1-9 (2001).Hatziki riakos, S. G and J. M. Dealy, "Wal l sl ip of mo l ten high dens i ty polyethylen e. I .Sl iding plate rheom eter studies," J . Rheol . 35, 497-523 (1991).Hatziki riakos, S . G a n d J . M . Dealy , "W al l s l ip o f mol t en h igh den s i ty polye thylene . II .Cap i l lary rheo me ter studies," J. Rheol . 36, 703-741 (1992).


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Kalyon, D. M. , "Let t e r t o the Edi tor : Com ments on "A new M ethod o f process ingcapi l lary visco me try data in the presence o f wal l s l ip" , J. Rheol . 47, 1087-1088 (2003).Kalyo n, D. M. and H. Gevg i l il i , "W al l slip and extrudate distort ion of three poly m ermel ts , J . Rheol . 47, 6 83-699 (2003).Kalyon, D. M. , A. Lawal , R. Yazici , P. Yaras and S. Rai lkar, "Mathemat ical model ingexperim ental studies of twin-screw extrusion of f i lled polym ers" , Polym . Eng. Sci. 39,1139-1151 (1999).Kalyon, D. M. , P. Yaras, B. Aral and U. Yi lmazer, "Rheological behavior of aconce ntrated suspension: A sol id rocket fuel simulant ," J. Rheol . 37, 35-53 (1993).Kalyo n, D. M. , H. Gokturk, P. Yaras and B. Aral , "M ot ion analysis of dev elopm ent ofwal l s l ip during die f low o f concen trated suspensions," S ociety of Plast ics Eng ineersAN TEC Technica l Papers . 41 , 1130-1134 (1995) .Kalyon, D. M. , A. Lawal , R. Yazici , P. Yaras and S. Rai lkar, "Mathemat ical model ingexperim ental studies of twin-screw extrusion of f il led polym ers" , Polym . Eng. Sci . 39,1139-1151 (1999).Kissi , N. E. and J. M. Piau, "The di fferent capi l lary f low regimes of entangledpolydimethyl si loxane polymers" Macroscopic sl ip at the wal l , hysteresis and cork flow,"J . Non -New tonian Flu id Mech. 37 , 55-94 (1990).Kissi , N. E. and J. M. Piau, "Adhesion of l inear low densi ty polyethylene for f lowregime s wi th shark skin," J . Rheol . 38, 1447-1463 (1994).Kissi , E. N. , J . M. Piau an d F. Tussaint , "Sha rkskin an d cracking o f po lym er ext rudates,"J . Non-N ewtonian F lu id Mech. 68 , 271-290 (1997).


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Nazem , F . and M. G. Hansen , "St ress growth and re l axat ion o f a mo l t en polye thylene in amodified Weissenberg rheogoniometer," J . Appl . Polym. Sci . 20, 1355-1370 (1976).Pet rie, C. J . S. and M. M . Denn, "Ins tabi l it ies in polym er processin g," AI Ch E J. 22, 209-236 (1976).Ram am urthy, A. V. , "W al l sl ip in viscous f luids and influence o f materials ofconst ruct ion," J . Rheol . 30, 337-357 (1986).Wang, S. Q. and O. A. Drda, "Superfluid l ike st ick-sl ip t ransi t ion in capi l lary f low ofl inear polye thylene mel ts . 1. Gene ral features," M acrom olecules 29, 2627 -2632 (1996).W ang, S. Q. and O. A. Drda, "St ick-sl ip t ransi t ion in capi l lary f low of l inearpolyethylene: 3. Surface condi t ions," Rheol . Acta 36, 128-134 (1997).Wa ng, S. Q. , "M olecu lar t ransi tion and dynam ics at polym er/wa l l interfaces" origins offlow instabi l i t ies and wal l s l ip," Advances in Polymer Science 138, 227-256 (1999).W hite J. L., H. Han, N. Nak aj ima an d R. Brzosk owsk i , "Th e influence o f materials ofcons t ruc tion on b iconica l ro tor and capi l la ry measurem ent s of shear v i scos i ty of rubberand i ts comp oun ds and con siderat ions of sl ippag e," J. Rheol . 35, 167 -189 (1991).Yi lmazer U. And D. Kalyon, "Sl ip effects in capi l lary and paral lel disk torsional f lows ofhigh ly fi l led suspe nsions," J . Rheol . 33, 1197-1212 (1989).


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E n v i r o n m e n t a lco n t ro l l e r

Fo rce Reb a lan ceT r a n s d u c e r

Actu a to rM o t o r

Co m p u ter in te r face fo r rh eo m eteran d h ig h sp eed Cam era

+

Hig h Sp eed Cam era500-2000 fps

F i g u r e 1


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A discon t inui ty in the s tra ight- line m arker indicates loss o f no -s l ipboundary c ond i t ion a t the po lym er m el t-meta l in ter face

Figure 2


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"- D = 0 . 3 7 5 "

L

. . . . . . . . . . . . . . . . i - ' -

" i

. . . . ~ . . . . . . . . . i

- O a n g 1- - 4 5 e

r D

T h e a n g l e o f c o n v e r g e n c e w a s v a r ie d b e t w e e n 1 5 , 4 5 a n d 7 5 d e g r e e s .

Figure 3


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T hermal Imag ingC a m e r a .

H i g h S p e e d C a m e r a

Figure 4


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P D M S45de g d - 0 .09 6 L /D - 4 0 C r osshe ad Spe ed: 2 in /min

0 .3 7 5 i n

F ig u r e 5


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1 9 0

1 8 0

1 7 0

1 6 0 -

1 5 0 -

1 4 0

1 3 0

1 2 0

1 1 0 -

100

Tbarrel= 180 oCer=0.03" L/D= 66

Discharge of the die - ~

Cross-Head speed:0.5"/min,7 = 4 6 7 . 3 s -1 , T m a x : 182.5C

I I I I I

5 10 15 20 25P o s i t i o n ( P i x e l s )

3 0

F i g u r e 6


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r~r~

1 0 0 0 0 0

1 0 0 0 0

1000

100

100.01

" - 3 . 0 S " 1= 4 0

0.1

= 1 0 s -1

T i m e , s

- - ' ~ ' - - 5 S - 1: ' ~ = 2 s -1

10

F i g u r e 7


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10,000

100,000

A

1,000

0 Capi l la ry RheometerA Steady Tors ional Flow

0


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1000000

1 0 0 0 0 0 -r, ~=

- - I r

I

, t l i ~ ' ~ #

i I I I I I I t I

~a=0 .078 M Pa

X

I i I I I l t I I

1 1 0 1 0 0 1 0 0 0

A p p a r e n t S h e a r R a t e , sPDM S" dev e lopm ent o f ex t ruda te su r face i rregu lar it i esAs a func t ion o f cap i l l a ry su r face /vo lum e ra t io

A D = 0 . 0 9 8 4 " L / D = 4 0X D = 0 . 0 5 9 1 " L / D = 4 0* D = 0 . 0 3 2 8 " L / D = 4 0

10000

Figure 9


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4P~raOraO

. 4 , , , a

~D

Development of Extrusion Instabilities and Surface Irregularities

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