{"id":10055,"date":"2026-10-16T02:48:59","date_gmt":"2026-10-16T02:48:59","guid":{"rendered":"https:\/\/tz-machinery.com\/?p=10055"},"modified":"2026-10-19T08:42:32","modified_gmt":"2026-10-19T08:42:32","slug":"extrusion-a-double-vis-de-feuilles-de-pet-recyclees-presentant-un-jaunissement","status":"publish","type":"post","link":"https:\/\/tz-machinery.com\/fr\/recycled-pet-sheet-yellowing-twin-screw-extrusion\/","title":{"rendered":"Pourquoi les feuilles de PET recycl\u00e9 jaunissent-elles et perdent-elles leur r\u00e9sistance ? Solutions pour l'extrusion \u00e0 double vis"},"content":{"rendered":"

L'extrusion de plaques en PET recycl\u00e9 se heurte souvent \u00e0 trois probl\u00e8mes de qualit\u00e9 majeurs : le jaunissement, une faible t\u00e9nacit\u00e9 et un brillant insuffisant. Ces probl\u00e8mes deviennent plus visibles lorsque l'on utilise un pourcentage \u00e9lev\u00e9 de flocons ou de broyats de PET recycl\u00e9. Pour les fabricants de plaques de PET destin\u00e9es au thermoformage, ces d\u00e9fauts peuvent nuire \u00e0 l'aspect du produit, \u00e0 ses performances de formage et \u00e0 la qualit\u00e9 du produit fini.<\/p>\n

1. Pourquoi les plaques en PET recycl\u00e9 jaunissent-elles ?<\/h2>\n

Les feuilles de PET peuvent jaunir en raison d'une d\u00e9gradation thermique, d'une hydrolyse li\u00e9e \u00e0 l'humidit\u00e9, de la pr\u00e9sence de mati\u00e8res recycl\u00e9es contamin\u00e9es ou d'une dur\u00e9e d'exposition excessive \u00e0 des temp\u00e9ratures \u00e9lev\u00e9es. Une gestion ad\u00e9quate des mati\u00e8res premi\u00e8res et des conditions d'extrusion optimis\u00e9es sont indispensables.<\/p>\n

Pour lignes d'extrusion de feuilles de PET \u00e0 double vis parall\u00e8les<\/a>, une configuration ad\u00e9quate de la vis, le contr\u00f4le de la temp\u00e9rature, le d\u00e9gazage sous vide et une filtration efficace de la mati\u00e8re fondue peuvent contribuer \u00e0 am\u00e9liorer la qualit\u00e9 de la mati\u00e8re fondue et \u00e0 r\u00e9duire les d\u00e9fauts de transformation.<\/p>\n

Couleur et r\u00e9sistance des feuilles de PET recycl\u00e9 avant et apr\u00e8s l'optimisation du processus d'extrusion \u00e0 double vis<\/p>\n

\"<\/p>\n

2. Comment am\u00e9liorer la r\u00e9sistance aux chocs et la brillance des feuilles de PET<\/h2>\n

Une faible r\u00e9sistance peut r\u00e9sulter d'une d\u00e9gradation du poids mol\u00e9culaire du PET, d'une viscosit\u00e9 intrins\u00e8que (VI) r\u00e9duite ou d'une qualit\u00e9 irr\u00e9guli\u00e8re des mat\u00e9riaux recycl\u00e9s. Un brillant insuffisant peut \u00eatre li\u00e9 \u00e0 une contamination, \u00e0 l'uniformit\u00e9 de la masse fondue, aux conditions de la fili\u00e8re ou aux r\u00e9glages des rouleaux de refroidissement.<\/p>\n

Outre l'optimisation du processus d'extrusion, les fabricants peuvent envisager les formulations de m\u00e9langes-ma\u00eetres suivantes comme points de d\u00e9part pour leurs essais de production.<\/p>\n\n\n\n\n\n\n\n\n
Type de m\u00e9lange-ma\u00eetre<\/th>\nQuantit\u00e9 recommand\u00e9e par 1 000 kg de PET<\/th>\n<\/tr>\n<\/thead>\n
M\u00e9lange-ma\u00eetre anti-jaunissement<\/td>\n300 \u00e0 600 g<\/td>\n<\/tr>\n
M\u00e9lange-ma\u00eetre de renforcement \/ anti-fissuration<\/td>\n6 \u00e0 8 kg<\/td>\n<\/tr>\n
M\u00e9lange-ma\u00eetre blanchissant<\/td>\n1,5 kg<\/td>\n<\/tr>\n
M\u00e9lange-ma\u00eetre am\u00e9liorant la brillance<\/td>\n1,5 kg<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Ces dosages sont donn\u00e9s \u00e0 titre indicatif et doivent \u00eatre valid\u00e9s en fonction des sp\u00e9cifications du fournisseur du m\u00e9lange-ma\u00eetre, de la qualit\u00e9 du PET recycl\u00e9 et des propri\u00e9t\u00e9s requises pour les feuilles. Les m\u00e9langes-ma\u00eetres blanchissants et rehausseurs de brillance peuvent am\u00e9liorer l'aspect, tandis que les additifs de renforcement peuvent contribuer \u00e0 am\u00e9liorer la r\u00e9sistance aux chocs. Les r\u00e9sultats r\u00e9els d\u00e9pendent de la compatibilit\u00e9 des additifs et des conditions de transformation.<\/p>\n

3. Comment l'extrusion \u00e0 double vis parall\u00e8le am\u00e9liore la qualit\u00e9 des feuilles de PET recycl\u00e9<\/h2>\n

Une ligne d'extrusion de feuilles de PET \u00e0 double vis parall\u00e8le correctement con\u00e7ue permet d'assurer un m\u00e9lange, un d\u00e9gazage et une transformation efficaces des mati\u00e8res premi\u00e8res recycl\u00e9es en PET adapt\u00e9es. Associ\u00e9e \u00e0 un syst\u00e8me de filtration ad\u00e9quat, \u00e0 un contr\u00f4le de la temp\u00e9rature et \u00e0 un dosage pr\u00e9cis des additifs, elle peut aider les fabricants \u00e0 am\u00e9liorer l'uniformit\u00e9 de la couleur, la r\u00e9sistance et l'aspect de surface des feuilles.<\/p>\n

La configuration optimale de l'\u00e9quipement et les param\u00e8tres de traitement d\u00e9pendent de la composition des mat\u00e9riaux recycl\u00e9s, du rendement vis\u00e9, de l'\u00e9paisseur de la feuille et de l'application finale. Le maintien d'une qualit\u00e9 stable des mati\u00e8res premi\u00e8res et la ma\u00eetrise de la d\u00e9gradation du PET sont \u00e9galement essentiels pour obtenir des r\u00e9sultats de production constants.<\/p>\n

FAQ<\/h2>\n

Pourquoi les feuilles de PET recycl\u00e9 jaunissent-elles ?<\/h3>\n

Quatre causes principales sont \u00e0 l'origine de ce ph\u00e9nom\u00e8ne : la d\u00e9gradation thermique, l'hydrolyse due \u00e0 l'humidit\u00e9, la pr\u00e9sence de mati\u00e8res recycl\u00e9es contamin\u00e9es et un temps de s\u00e9jour excessif \u00e0 une temp\u00e9rature de fusion \u00e9lev\u00e9e. Le jaunissement est une alt\u00e9ration chimique de la cha\u00eene polym\u00e8re ; il est donc pr\u00e9f\u00e9rable de le ma\u00eetriser en amont gr\u00e2ce \u00e0 la gestion des mati\u00e8res premi\u00e8res, au contr\u00f4le de la temp\u00e9rature, au d\u00e9gazage sous vide et \u00e0 la filtration de la masse fondue.<\/p>\n

Le jaunissement peut-il \u00eatre invers\u00e9 une fois la feuille fabriqu\u00e9e ?<\/h3>\n

Non. Le jaunissement r\u00e9sulte d'une modification mol\u00e9culaire du PET lui-m\u00eame ; il est donc impossible de le faire dispara\u00eetre par polissage ou lavage a posteriori. La solution la plus pratique consiste \u00e0 pr\u00e9venir ce ph\u00e9nom\u00e8ne : veillez \u00e0 ce que les flocons restent secs et propres, r\u00e9duisez le temps de s\u00e9jour et ajoutez un m\u00e9lange-ma\u00eetre anti-jaunissement \u00e0 un dosage valid\u00e9.<\/p>\n

Pourquoi les plaques en PET recycl\u00e9 perdent-elles leur t\u00e9nacit\u00e9 et leur r\u00e9sistance aux chocs ?<\/h3>\n

La perte de r\u00e9sistance s'accompagne g\u00e9n\u00e9ralement d'une baisse du poids mol\u00e9culaire et de la viscosit\u00e9 intrins\u00e8que (VI). Les paillettes recycl\u00e9es pr\u00e9sentent des valeurs de VI variables et des ant\u00e9c\u00e9dents d'exposition thermique diff\u00e9rents ; la masse fondue peut donc contenir des fractions d\u00e9grad\u00e9es qui se fissurent sous l'effet d'un choc. Une qualit\u00e9 constante des paillettes et un traitement thermique doux permettent de pr\u00e9server la VI.<\/p>\n

Quelle quantit\u00e9 de m\u00e9lange-ma\u00eetre anti-jaunissement utilise-t-on par tonne de PET ?<\/h3>\n

On commence g\u00e9n\u00e9ralement par utiliser entre 300 et 600 g pour 1 000 kg de PET. La quantit\u00e9 exacte d\u00e9pend des sp\u00e9cifications du fournisseur du m\u00e9lange-ma\u00eetre, de la couleur des flocons recycl\u00e9s entrants et de l'aspect souhait\u00e9 de la feuille ; elle doit donc \u00eatre confirm\u00e9e lors d'essais de production.<\/p>\n

Quelle quantit\u00e9 de m\u00e9lange ma\u00eetre de renforcement est ajout\u00e9e \u00e0 la feuille de PET recycl\u00e9 ?<\/h3>\n

La dose de r\u00e9f\u00e9rence est de 6 \u00e0 8 kg pour 1 000 kg de PET, ce qui correspond \u00e0 environ dix fois la quantit\u00e9 d'additif anti-jaunissement. Les performances en termes de r\u00e9sistance aux chocs d\u00e9pendent de la compatibilit\u00e9 de l'additif avec la r\u00e9sine de base et des conditions de transformation ; il est donc recommand\u00e9 de valider cette concentration sur votre propre ligne de production avant de passer \u00e0 une \u00e9chelle sup\u00e9rieure.<\/p>\n

Une ligne \u00e0 double vis n\u00e9cessite-t-elle un pr\u00e9s\u00e9chage pour les flocons de PET recycl\u00e9 ?<\/h3>\n

Le d\u00e9gazage sous vide et la conception \u00e0 \u00e9vents multiples permettent d'\u00e9liminer l'humidit\u00e9 et les compos\u00e9s volatils pendant l'extrusion, ce qui r\u00e9duit la cristallisation et la charge de pr\u00e9s\u00e9chage qu'un Ligne d'extrusion de feuilles PET \u00e0 vis unique<\/a> ce que cela n\u00e9cessite habituellement. Les flocons extr\u00eamement humides ou tr\u00e8s encrass\u00e9s peuvent n\u00e9anmoins n\u00e9cessiter un traitement pr\u00e9alable.<\/p>\n

Quelles sont les causes d'un manque de brillance sur les feuilles de PET recycl\u00e9 ?<\/h3>\n

Un brillant insuffisant est g\u00e9n\u00e9ralement d\u00fb \u00e0 la pr\u00e9sence d'impuret\u00e9s, \u00e0 un manque d'homog\u00e9n\u00e9it\u00e9 de la masse fondue, \u00e0 l'\u00e9tat de la fili\u00e8re ou au r\u00e9glage des rouleaux de refroidissement. Une pression de fusion stable, un syst\u00e8me de filtration propre et un refroidissement contr\u00f4l\u00e9 ont tous une incidence directe sur la finition de surface.<\/p>\n

Une structure de co-extrusion ABA peut-elle masquer la d\u00e9coloration du PET recycl\u00e9 ?<\/h3>\n

Oui. Un Ligne de coextrusion \u00e0 trois couches ABA PET<\/a> Cette technique consiste \u00e0 recouvrir un noyau recycl\u00e9 d'une couche ext\u00e9rieure vierge, ce qui rend la l\u00e9g\u00e8re d\u00e9coloration du noyau beaucoup moins visible sur le produit fini. C'est une solution pratique lorsque la teneur en mat\u00e9riaux recycl\u00e9s est \u00e9lev\u00e9e, mais que l'aspect de la surface doit rester haut de gamme.<\/p>\n

Comment les fabricants de t\u00f4les peuvent-ils garantir une qualit\u00e9 constante des mat\u00e9riaux recycl\u00e9s ?<\/h3>\n

G\u00e9rer le cycle en interne. A d\u00e9chets de bordures de t\u00f4le broy\u00e9s en ligne<\/a> renvoie les d\u00e9chets osseux directement vers l'extrudeuse, ce qui permet au flux de mati\u00e8re broy\u00e9e de rester propre, sec et tra\u00e7able, au lieu d'accumuler des contaminants d'origine inconnue.<\/p>","protected":false},"excerpt":{"rendered":"

Les causes profondes du jaunissement et de la fragilit\u00e9 des feuilles de PET recycl\u00e9 ont \u00e9t\u00e9 identifi\u00e9es ; les r\u00e9glages de l'extrudeuse \u00e0 double vis et les dosages de m\u00e9lange-ma\u00eetre ont \u00e9t\u00e9 ajust\u00e9s pour r\u00e9tablir la couleur et la r\u00e9sistance.<\/p>","protected":false},"author":1,"featured_media":10060,"comment_status":"open","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":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center 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toughness loss: learn the causes plus twin screw extrusion settings and masterbatch dosages that restore color and impact.","_yoast_wpseo_title":"Recycled PET Sheet Yellowing: Causes & Twin Screw Fix"},"categories":[68],"tags":[],"class_list":["post-10055","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tz-machinery-knowledge"],"yoast_head":"\nRecycled PET Sheet Yellowing: Causes & Twin Screw Fix<\/title>\n<meta name=\"description\" content=\"Recycled PET sheet yellowing and toughness loss: learn the causes plus twin screw extrusion settings and masterbatch dosages that restore color and impact.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/tz-machinery.com\/fr\/extrusion-a-double-vis-de-feuilles-de-pet-recyclees-presentant-un-jaunissement\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta 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