{"id":3539,"date":"2026-09-05T03:12:24","date_gmt":"2026-09-05T03:12:24","guid":{"rendered":"https:\/\/sivite-machinery.com\/?p=3539"},"modified":"2026-09-07T01:07:05","modified_gmt":"2026-09-07T01:07:05","slug":"vis-dextrusion-pour-feuilles-de-pet","status":"publish","type":"post","link":"https:\/\/sivite-machinery.com\/fr\/pet-sheet-extrusion-screw\/","title":{"rendered":"Vis d'extrusion pour feuilles de PET : comment choisir le rapport L\/D"},"content":{"rendered":"
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La premi\u00e8re fois que de nombreux acheteurs jettent un \u0153il \u00e0 Extrusion de feuilles de PET<\/strong><\/a> En ce qui concerne les \u00e9quipements, on constate que les extrudeuses de feuilles de PET de diff\u00e9rents fabricants se ressemblent beaucoup \u00e0 premi\u00e8re vue : la disposition du cylindre, de la fili\u00e8re et des rouleaux de refroidissement est pratiquement identique. Mais d\u00e8s que l\u2019on examine de plus pr\u00e8s le composant central, \u00e0 savoir la vis d\u2019extrusion pour feuilles de PET, on constate que, bien qu\u2019il s\u2019agisse dans tous les cas de \u2019 feuilles de PET \u201c, la conception du rapport L\/D de la vis est totalement diff\u00e9rente selon qu\u2019il s\u2019agit de PET vierge, de RPET, de CPET ou de feuilles de PETG moul\u00e9es pour le mobilier. Il ne s\u2019agit pas d\u2019un choix de conception arbitraire de la part des fabricants : cela s\u2019explique par le fait que chaque mat\u00e9riau poss\u00e8de des propri\u00e9t\u00e9s physiques diff\u00e9rentes, et que l\u2019extrudeuse doit contr\u00f4ler avec pr\u00e9cision le profil de temp\u00e9rature et le temps de s\u00e9jour du mat\u00e9riau pendant l\u2019extrusion \u00e0 l\u2019\u00e9tat fondu afin d\u2019\u00e9viter l\u2019apparition de taches cristallines, une faible t\u00e9nacit\u00e9, un jaunissement et des surfaces ternes sur la feuille finie.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Qu'est-ce que le rapport L\/D d'une vis, et pourquoi d\u00e9termine-t-il la qualit\u00e9 de l'extrusion ?<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Le rapport L\/D d'une vis d\u00e9signe le rapport entre la longueur effective de travail de la vis et son diam\u00e8tre \u2014 par exemple, une vis d'un diam\u00e8tre de 90 mm et d'une longueur effective de 3 600 mm pr\u00e9sente un rapport L\/D de 40:1. Ce chiffre peut sembler n'\u00eatre qu'un simple param\u00e8tre g\u00e9om\u00e9trique, mais il d\u00e9termine directement la dur\u00e9e pendant laquelle la mati\u00e8re est chauff\u00e9e, cisaill\u00e9e et m\u00e9lang\u00e9e \u00e0 l'int\u00e9rieur de la vis, ainsi que le nombre de zones ind\u00e9pendantes de contr\u00f4le de la temp\u00e9rature dans lesquelles la vis peut \u00eatre divis\u00e9e \u2014 ce que l'on appelle commun\u00e9ment le temps de s\u00e9jour et la pr\u00e9cision du contr\u00f4le segment\u00e9 de la temp\u00e9rature.
Un rapport L\/D plus \u00e9lev\u00e9 permet g\u00e9n\u00e9ralement de diviser la vis en un plus grand nombre de zones de chauffage et de plastification, ce qui rend l'intensit\u00e9 de cisaillement et l'\u00e9l\u00e9vation de temp\u00e9rature dans chaque zone plus mod\u00e9r\u00e9es et plus faciles \u00e0 contr\u00f4ler. Un rapport L\/D plus faible concentre la plastification dans un nombre r\u00e9duit de zones, offrant ainsi un rendement sup\u00e9rieur ; toutefois, si la mati\u00e8re est intrins\u00e8quement plus difficile \u00e0 plastifier ou pr\u00e9sente un niveau de contamination plus \u00e9lev\u00e9, cela peut entra\u00eener une plastification incompl\u00e8te ou un cisaillement excessif localis\u00e9. C\u2019est pr\u00e9cis\u00e9ment pour cette raison que la conception des vis varie sensiblement d\u2019un Extrudeuses de feuilles de PET<\/strong><\/a> traitement de diff\u00e9rents mat\u00e9riaux \u2014 l'objectif principal consiste \u00e0 utiliser le rapport L\/D et le syst\u00e8me de r\u00e9gulation de temp\u00e9rature segment\u00e9 les mieux adapt\u00e9s aux propri\u00e9t\u00e9s physiques de chaque mat\u00e9riau, tout en contr\u00f4lant la qualit\u00e9 de la plastification et la stabilit\u00e9 thermique.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Quels d\u00e9fauts de t\u00f4le r\u00e9sultent d'un temps de s\u00e9jour mal contr\u00f4l\u00e9 ?<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Plastification incompl\u00e8te : taches cristallines<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Si le rapport L\/D de la vis n'est pas adapt\u00e9 au degr\u00e9 de plasticisation du mat\u00e9riau, ou si la conception segment\u00e9e du syst\u00e8me de contr\u00f4le de la temp\u00e9rature s'av\u00e8re insuffisante, les granul\u00e9s de PET peuvent pr\u00e9senter des zones localis\u00e9es qui ne sont pas enti\u00e8rement fondues lors de la transformation. Ces particules non fondues forment des taches cristallines visibles une fois la feuille refroidie \u2014 ce qui ne constitue pas seulement un probl\u00e8me esth\u00e9tique, mais aussi un point de concentration des contraintes qui r\u00e9duit la r\u00e9sistance m\u00e9canique globale de la feuille.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Historique thermique non contr\u00f4l\u00e9 : jaunissement, perte de t\u00e9nacit\u00e9, surface terne<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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\u00c0 l\u2019inverse, si le contr\u00f4le segment\u00e9 de la temp\u00e9rature et de l\u2019intensit\u00e9 de cisaillement ne sont pas finement adapt\u00e9s \u00e0 la sensibilit\u00e9 thermique d\u2019un mat\u00e9riau, et si celui-ci reste trop longtemps ou subit un cisaillement excessif dans une zone localis\u00e9e \u00e0 haute temp\u00e9rature, le PET subit une d\u00e9gradation thermique \u2014 qui se manifeste par un jaunissement, une diminution de la t\u00e9nacit\u00e9 due \u00e0 la scission des cha\u00eenes mol\u00e9culaires et une surface nettement plus terne. Le PET est un polyester relativement sensible \u00e0 l'historique thermique, et sa d\u00e9gradation s'acc\u00e9l\u00e8re consid\u00e9rablement en cas de s\u00e9jour localis\u00e9 \u00e0 des temp\u00e9ratures sup\u00e9rieures \u00e0 environ 270 \u00b0C.
\u00c9tant donn\u00e9 que ces deux types de d\u00e9fauts correspondent \u00e0 des probl\u00e8mes oppos\u00e9s \u2014 \u201c une plastification insuffisante \u201d contre \u201c un historique thermique localis\u00e9 hors de contr\u00f4le \u201d \u2014 le rapport L\/D de la vis et la conception des zones doivent \u00eatre adapt\u00e9s avec pr\u00e9cision au comportement \u00e0 la fusion de chaque mat\u00e9riau sp\u00e9cifique, plut\u00f4t que de r\u00e9duire la d\u00e9cision \u00e0 une seule dimension du type \u201c plus c\u2019est long, plus c\u2019est s\u00fbr \u201d ou \u201c plus c\u2019est court, plus c\u2019est s\u00fbr \u201d.\u201d<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Param\u00e8tres relatifs au rapport longueur\/diam\u00e8tre des vis de SIVITE, issus de plus d'une d\u00e9cennie d'essais<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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En tant que fabricant sp\u00e9cialis\u00e9 dans la conception de vis pour l\u2019extrusion de feuilles de PET, SIVITE, fabricant d\u2019extrudeuses de feuilles, a consacr\u00e9 plus d\u2019une d\u00e9cennie \u00e0 mener des essais approfondis en conditions r\u00e9elles sur du PET vierge, de l\u2019APET, du RPET, du CPET et du PETG, pour aboutir progressivement \u00e0 un ensemble de param\u00e8tres de rapport L\/D garantissant la qualit\u00e9 la plus stable possible des feuilles. Ces chiffres ne sont pas des calculs th\u00e9oriques : ils sont le r\u00e9sultat de validations r\u00e9p\u00e9t\u00e9es par rapport \u00e0 des donn\u00e9es de production r\u00e9elles :<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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1. PET vierge\/APET : rapport L\/D de 40:1<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Les granul\u00e9s de PET vierge ou d\u2019APET pr\u00e9sentent des propri\u00e9t\u00e9s physiques homog\u00e8nes ainsi qu\u2019une faible teneur en humidit\u00e9 et en impuret\u00e9s. SIVITE utilise un rapport L\/D de 40:1, avec davantage de zones de contr\u00f4le de temp\u00e9rature segment\u00e9es, ce qui permet un processus de plastification plus doux et plus complet \u2014 pr\u00e9servant ainsi la transparence et la brillance des feuilles tout en garantissant une production stable.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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2. RPET : rapport L\/D de 48:1 (avec zone de d\u00e9gazage)<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Le PET recycl\u00e9 (RPET) pr\u00e9sente des taux d\u2019humidit\u00e9 et de contamination plus \u00e9lev\u00e9s, ainsi que des fluctuations de l\u2019indice de viscosit\u00e9 (IV), ce qui rend la plastification nettement plus difficile ; il n\u00e9cessite en outre l\u2019\u00e9limination de l\u2019humidit\u00e9 et des compos\u00e9s volatils de faible poids mol\u00e9culaire lors de l\u2019extrusion. SIVITE utilise un rapport L\/D de 48:1 pour le RPET, avec une zone de d\u00e9gazage sous vide int\u00e9gr\u00e9e, garantissant une plastification compl\u00e8te tout en \u00e9vacuant en continu les compos\u00e9s volatils afin d'\u00e9viter la formation de bulles et de voiles dans la feuille.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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3. CPET : rapport longueur\/diam\u00e8tre 34:1<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Le CPET (PET cristallis\u00e9) est principalement utilis\u00e9 pour la fabrication de barquettes alimentaires r\u00e9sistantes \u00e0 la chaleur et de r\u00e9cipients adapt\u00e9s au four. Sa particularit\u00e9 r\u00e9side dans le fait que la feuille finie doit pr\u00e9senter un degr\u00e9 de cristallinit\u00e9 contr\u00f4l\u00e9 pour r\u00e9sister au chauffage au micro-ondes ou au four. SIVITE utilise un rapport L\/D de 34:1 pour le CPET, associ\u00e9 \u00e0 un contr\u00f4le de temp\u00e9rature segment\u00e9 plus pr\u00e9cis, de sorte que la mati\u00e8re fondue sorte de la vis dans un \u00e9tat thermique adapt\u00e9 \u00e0 l\u2019\u00e9tape de cristallisation contr\u00f4l\u00e9e qui suit \u2014 \u00e9vitant ainsi un historique thermique trop important ou insuffisant pour une cristallisation stable.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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4. PETG : rapport L\/D de 32:1<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Le PETG (PET modifi\u00e9 au glycol) comporte une unit\u00e9 de copolym\u00e8re int\u00e9gr\u00e9e \u00e0 sa structure mol\u00e9culaire, ce qui lui conf\u00e8re une stabilit\u00e9 thermique relativement plus faible ; il est g\u00e9n\u00e9ralement trait\u00e9 \u00e0 des temp\u00e9ratures inf\u00e9rieures de 20 \u00e0 30 \u00b0C \u00e0 celles du PET standard \u2014 un temps de traitement trop long entra\u00eene facilement une d\u00e9gradation thermique. SIVITE utilise un rapport L\/D de 32:1 pour le PETG, associant un parcours de plastification relativement plus court \u00e0 des temp\u00e9ratures de transformation plus basses afin de r\u00e9duire le temps de s\u00e9jour dans les zones \u00e0 haute temp\u00e9rature. Ce param\u00e8tre a \u00e9t\u00e9 valid\u00e9 et optimis\u00e9 gr\u00e2ce \u00e0 des donn\u00e9es de production r\u00e9elles exhaustives sur des feuilles de PETG destin\u00e9es au moulage de mobilier, ce qui permet de r\u00e9duire de mani\u00e8re fiable le risque de d\u00e9gradation thermique tout en garantissant une plastification compl\u00e8te.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Les chiffres ci-dessus correspondent aux param\u00e8tres recommand\u00e9s par SIVITE, issus d'une synth\u00e8se de plus d'une d\u00e9cennie de donn\u00e9es issues d'essais en conditions r\u00e9elles. Le rapport L\/D r\u00e9el doit \u00eatre ajust\u00e9 avec pr\u00e9cision en fonction du rendement sp\u00e9cifique de l'\u00e9quipement, de la valeur IV de la mati\u00e8re premi\u00e8re et des exigences de mise en forme en aval.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Guide d'achat : questions \u00e0 se poser avant de choisir le rapport L\/D d'une vis sans fin<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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\u25cf Quelle est votre mati\u00e8re premi\u00e8re principale ? Vierge, recycl\u00e9e ou un m\u00e9lange \u2014 et dans quelles proportions \u2014, car cela d\u00e9termine la difficult\u00e9 de plastification et les besoins en mati\u00e8re de d\u00e9gazage
\u25cf Envisagez-vous de produire des mat\u00e9riaux sp\u00e9cialis\u00e9s tels que le CPET ou le PETG ? Si la m\u00eame ligne doit traiter plusieurs mat\u00e9riaux \u00e0 l'avenir, v\u00e9rifiez au pr\u00e9alable aupr\u00e8s du fabricant si la vis peut \u00eatre ajust\u00e9e de mani\u00e8re modulaire ou s'il faudra disposer de plusieurs jeux de vis.
\u25cf Quel est le niveau d'exigence de vos sp\u00e9cifications en mati\u00e8re d'aspect et de propri\u00e9t\u00e9s m\u00e9caniques des feuilles ? Plus les exigences en mati\u00e8re de transparence, de brillance et de r\u00e9sistance sont \u00e9lev\u00e9es, plus il est n\u00e9cessaire d'ajuster avec pr\u00e9cision le rapport L\/D et le contr\u00f4le segment\u00e9 de la temp\u00e9rature.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>","protected":false},"excerpt":{"rendered":"

The first time many buyers look at PET sheet extrusion equipment, they notice that different manufacturers’ PET sheet extruders look […]<\/p>\n","protected":false},"author":5,"featured_media":3540,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[37],"tags":[],"class_list":["post-3539","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-knowledge"],"yoast_head":"\nPET Sheet Extrusion Screw: How to Choose the L\/D Ratio<\/title>\n<meta name=\"description\" content=\"How should you choose a PET sheet extrusion screw L\/D ratio for virgin PET, RPET, CPET, and PETG? See SIVITE's data-backed 32:1-48:1 parameters that prevent crystalline spots and yellowing.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/sivite-machinery.com\/fr\/vis-dextrusion-pour-feuilles-de-pet\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"PET Sheet Extrusion Screw: How to Choose the L\/D Ratio\" \/>\n<meta property=\"og:description\" content=\"How should you choose a PET sheet extrusion screw L\/D ratio for virgin PET, RPET, CPET, and PETG? 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