Puas yog annealing hloov qhov roughness ntawm PTFE zaj duab xis tsim los ntawm tig?

Annealing ho hloov qhov roughness ntawm PTFE zaj duab xis npaj los ntawm kev tig, feem ntau qhia ib tug qauv ntawm txo roughness thiab ib tug smoother nto. Qhov no yog nrog los ntawm kev hloov pauv tsis tu ncua ntawm qhov chaw microstructure. Cov laj thawj tseem ceeb muaj feem cuam tshuam nrog cov crystallinity ntawm PTFE, tso tawm cov kev ntxhov siab nyob hauv lub sijhawm tig, thiab cov saw hlau molecular rearrangement.

I. Thawj Ntog Xeev ntawm Tig PTFE Films
Tig yuav muaj kev hloov kho PTFE rods / raj kom tau txais cov yeeb yaj kiab. Thaum lub sij hawm ua, kev txiav txim ntawm cov cuab yeej tsim cov kev taw qhia txiav cov cim (xws li cov kab sib txuas microgrooves thiab burrs) ntawm cov yeeb yaj kiab nto. Lub shearing quab yuam generated thaum txiav ua rau saum npoo molecular chains mus rau orient, ua residual stress. Ib txhij, lub zos crystallization raug cuam tshuam (ua rau thaj tsam amorphous lossis microcrystalline distortion). Qhov no ua rau muaj qhov pib ntawm qhov roughness siab heev (Ra / Rz) thiab qhov tsis sib xws ntawm qhov chaw morphology hauv zaj duab xis tig.

II. Mechanism ntawm Nto Roughness Hloov Kho los ntawm Annealing
PTFE muaj qhov hloov pauv iav ntawm kwv yees li -120℃thiab melting point ntawm kwv yees li 327℃. Annealing feem ntau ua ntawm 150 ~ 300℃(hauv qab lub melting point nyob rau hauv high-elasticity ntau). Thaum cov txheej txheem no, peb qhov kev hloov pauv tseem ceeb tshwm sim hauv zaj duab xis, cuam tshuam ncaj qha rau saum npoo:

Residual Stress Release: Shear stress thiab internal stress generated thaum tig yog maj mam tso tawm thaum lub sij hawm annealing. Micro-warping thiab zawj distortion tshwm sim los ntawm kev ntxhov siab ntawm qhov chaw yog smoothed tawm, txo cov microscopic protrusions thiab kev nyuaj siab ntawm qhov chaw.

Molecular Chain Rearrangement thiab Txhim Kho Crystallization: Molecular chains nyob rau hauv cov cheeb tsam amorphous tau txais kev ua haujlwm thermal, rov kho dua rau lub xeev crystalline ruaj khov. Microcrystals loj hlob thiab txhim kho (grain coarsening), thiab cov cheeb tsam crystalline distorted thaum xub thawj cuam tshuam los ntawm kev txiav ua ntau dua, ua kom lub ntsej muag microscopic ntawm qhov chaw thiab ua rau lub ntsej muag denser.

Nto micro- tshem tawm qhov tsis xws luag: Microburrs thiab microcracks ntawm qhov chaw tsim tawm thaum lub sij hawm tig yog smoothed los ntawm siab elasticity thiab viscous ntws yam ntxwv ntawm PTFE nyob rau hauv thermal ua (me ntsis fusion ntawm tsawg- melting- taw tes nto microcrystals). Directional txiav grooves yog sau thiab passivated, thiab ob qho tib si qhov tob thiab dav ntawm cov grooves txo.

III. Cov kev hloov hauv Surface Roughness tom qab Annealing
Raws li tus txheej txheem annealing tsim nyog (kub, tuav lub sij hawm, tus nqi txias), qhov roughness ntawm tig PTFE zaj duab xis qhia tau hais tias muaj kev tswj tau txo qis nrog cov txheej txheem meej:
Cov nyhuv kub: Nyob rau hauv thaj tsam ntawm 150 ~ 280 degree, qhov roughness (Ra) tsis tu ncua nrog nce qhov kub thiab txias; Txawm li cas los xij, thaum qhov kub nce mus txog 300℃(ze rau lub melting point), me ntsis viscous flow deformation tshwm sim ntawm qhov chaw. Yog hais tias lub sij hawm tuav ntev dhau lawm, nws yuav ua rau thaj tsam ntawm qhov chaw, thiab qhov roughness yuav nce me ntsis.

Lub Sijhawm Teebmeem: Hauv thawj lub sijhawm tuav (0.5 ~ 2h), roughness txo qis tshaj plaws (kev ntxhov siab sai thiab sai crystallization); Tom qab tuav lub sij hawm tshaj 2h, qhov roughness txo qis, ncav cuag saturation.

Txias tus nqi: Ua kom txias qeeb (piv txwv li, 5 ~ 10℃/ min) txhawb nqa kev sib txuas ntawm cov saw hlau molecular, uas ua rau muaj cov crystallization tsis tu ncua thiab smoother nto; Kev ua kom txias sai sai ua rau quenching ntawm microcrystals, tsis sib xws crystallization, thiab cov nyhuv roughness txo qis.

IV. Cov xwm txheej tshwj xeeb: Kev cuam tshuam tsis zoo ntawm cov txheej txheem Annealing tsis raug

Yog tias qhov kub thiab txias siab dhau (Ntau dua lossis sib npaug rau 320 degree), lub sijhawm tuav ntev dhau, lossis qhov cua kub ceev dhau, nws tuaj yeem ua rau:

Lub zos melting ntawm PTFE nto txheej, uas ua rau viscous nto bulges thiab shrinkage kab noj hniav;
Ntau dhau ntawm cov nplej coarsening, ua qoob loo ciam teb protrusions, uas ua rau nce qhov roughness;
Cov zaj duab xis undergoes thermal shrinkage, ua rau macroscopic wrinkles nyob rau saum npoo, ho nce pom roughness.

Yog li ntawd, kev txhim kho ntawm qhov chaw roughness los ntawm annealing yog txheej txheem -nyob thiab yuav tsum tau tswj nyob rau hauv ib tug tsim nyog parameter ntau yam.

V. Cov teebmeem ntxiv: Kev poob ntawm Deg Orientation Qhov saum npoo ntawm machined films nthuav tawm ib qho txawv molecular saw orientation (raws li cov kev taw qhia txiav) vim cov txheej txheem txiav. Tom qab annealing, qhov kev taw qhia no ploj mus nrog thermal zog, hloov qhov chaw los ntawm anisotropic txiav kev ntxhib los mos mus rau isotropic, du morphology. Qhov no yog ib qho tseem ceeb ntawm qhov pom ntawm qhov roughness txo, nrog rau cov isotropic hloov nyob rau hauv cov zaj duab xis mechanical zog (xws li tensile zog thiab elongation ntawm so).

Nyob rau hauv cov ntsiab lus, annealing yog ib tug zoo txhais tau tias ntawm kev txhim kho cov nto roughness ntawm machined PTFE films. Nyob rau hauv cov txheej txheem tsim nyog, nws tuaj yeem txo qhov roughness, tshem tawm cov qhab nia, thiab tau txais qhov chaw du thiab ntom. Qhov tseem ceeb, nws ua tiav qhov kev ntxhov siab nyob hauv qhov tso tawm, molecular saw rearrangement, thiab crystallization zoo los ntawm kev ua haujlwm thermal. Cov txheej txheem tsis ua haujlwm (kub, sijhawm, qhov txias txias) yog qhov tseem ceeb hauv kev txiav txim siab qhov hloov pauv qhov ntxhib; Cov txheej txheem tsis raug tuaj yeem ua rau muaj kev nce hauv roughness.