Kev soj ntsuam qhov tsis txaus ntseeg- PFA phab ntsa tuab (2.5 hli) tso cai rau cov pa tawm ntawm acetone ntau dua li cov phab ntsa nyias (1.5 hli) ntawm 60℃- tshwm sim thaum phab ntsa tuab yog extruded nrog cua txias (dej quench), tsim kom muaj kev ntxhov siab ntau dua thiab ntau dua amorphous dawb ntim. Acetone yog o hnyav hnyav rau PFA (solubility parameter δ ≈ 19.7 MPa¹/², ze rau PFA's amorphous theem). Nws plasticizes cov polymer, ua kom cov saw hlau txuas ntxiv. Nyob rau hauv siab -residual-stress tuab phab ntsa, cov cheeb tsam amorphous yog stretched thiab qhib ntau dua, muab qis tsis kam rau diffusion. Ib phab ntsa nyias nyias, yog tias qeeb-cooled (annealed), tej zaum yuav muaj kev ntxhov siab qis dua thiab ntau dua crystallinity, txo qhov permeation. Yog li, phab ntsa thickness ib leeg tsis txiav txim siab permeation tus nqi; ua keeb kwm thiab crystallinity yog qhov tseem ceeb sib npaug. Rau acetone vapor, qeeb-cooled 2.5 mm phab ntsa (crystallinity 55–60%) tuaj yeem muaj ib nrab ntawm qhov permeation ntawm phab ntsa quenched 1.5 mm (crystallinity 40–45%).
Lub luag haujlwm ntawm Residual Stress thiab Crystallinity
Permeation ua raws li P=D × S, qhov twg D yog diffusivity thiab S yog solubility. Acetone swells PFA, nce D thiab S. Qhov seem tensile kev nyuaj siab (los ntawm ceev txias) qhib cov cheeb tsam amorphous, ntxiv D. Ntau dua crystallinity txo amorphous ntim, txo D thiab S. Ib phab ntsa tuab uas quenched muaj ob qho tib si siab residual stress (5–10 MPa) thiab tsawg crystallinity (45%). Ib phab ntsa nyias uas yog annealed muaj kev ntxhov siab tsawg (1-2 MPa) thiab crystallinity siab (55-60%). Cov tom kawg tuaj yeem muaj 2-5 × qis permeation txawm tias nyias.
Kev sib piv Permeation: Acetone Vapor ntawm 60 degree, 1 bar
| Phab ntsa Thickness (mm) | Txoj kev txias | Crystallinity (%) | Residual Stress (MPa) | Permeation Rate (g / m²) hnub | Normalized los ntawm Thickness (g·mm / m²·hnub) |
|---|---|---|---|---|---|
| 1.5 | Dej quench | 42 | 6–8 | 25–35 | 38–53 |
| 1.5 | Cua txias (slow) | 48 | 3–4 | 15–22 | 23–33 |
| 1.5 | Annealed (200 degree) | 58 | 1–2 | 8–12 | 12–18 |
| 2.0 | Dej quench | 40 | 7–9 | 30–40 | 60–80 |
| 2.0 | Annealed | 56 | 1–2 | 10–15 | 20–30 |
| 2.5 | Dej quench | 38 | 8–10 | 40–55 | 100–138 |
| 2.5 | Cua txias | 45 | 5–6 | 25–35 | 63–88 |
| 2.5 | Annealed | 60 | 1–2 | 12–18 | 30–45 |
Lub phab ntsa 2.5 hli quenched (40–55 g / m²·hnub) muaj 5 × siab permeation tshaj 1.5 mm annealed phab ntsa (8–12 g / m²·hnub) - thicker tab sis ntau permeable. Qhov normalized npaum li cas (permeation × thickness) qhia qhov tseeb cov khoom permeability: quenched PFA muaj 100–138 g·mm/m²·hnub; annealed PFA muaj 12–45 g·mm/m²·hnub. Annealing txo permeability los ntawm 3-5 ×.
Vim li cas Acetone txawv ntawm Tsis yog - o Permeants
Rau cov uas tsis yog{0}} o (N₂, O₂, CO₂), permeability yog proportional rau 1/thickness. Thicker ib txwm txhais tau tias qis permeation. Rau cov kuab tshuaj o (acetone, MEK, ethyl acetate, toluene), polymer plasticizes li permeation pib. Lub diffusion coefficient nce nrog lub sijhawm. Nyob rau hauv tuab, siab -stress phab ntsa, acetone ua rau o ntau dua, ntxiv D. Cov nyhuv yog nws pib-catalytic. Nyob rau hauv ib qho annealed, low{10}}stress phab ntsa, PFA tiv thaiv o vim hais tias cov crystalline cheeb tsam txwv lub amorphous theem.
Cov txiaj ntsig zoo rau kev xaiv lub rhaub dej kub
Rau kev pab cuam acetone vapor (los yog ib qho o hnyav):
Tsis txhob xav tias tuab yog ib txwm zoo dua- ib txwm thov cov ntaub ntawv permeation rau cov kuab tshuaj tshwj xeeb ntawm kev ua haujlwm kub.
Qhia kom meej PFA annealed(post-extrusion annealing ntawm 200℃rau 4-8 teev). Qhov no txo cov permeation los ntawm 2-5 × tsis hais thickness.
Ntsuas qhov kev ntxhov siab seemntawm lub nplhaib curvature; txais tsuas yog cua sov nrog R_curve> 300 mm (σ_res < 2 MPa).
Xav txog qhov kub thiab txias: Acetone permeation poob los ntawm 50% rau txhua txhua 10℃txo.
Piv txwv teb
Lub tshuab tshuaj reactor rhaub acetone vapor ntawm 60℃siv lub 2.5 hli PFA rhaub (dej-quenched, as-extruded). Permeation yog 45 g / m²·hnub, ua rau corrosion sai ntawm cov tub ntxhais hlau (acetone / H₂O / peroxide nres). Cov cua sov siv tau 6 lub hlis. Cov nroj tsuag tau hloov mus rau 1.5 mm annealed PFA rhaub (slow{10}}cooled, annealed 200℃/ 4 hr). Permeation poob mus rau 10 g / m²·hnub. Cua sov lub neej txuas ntxiv mus rau 3+ xyoo. Lub thinner, ua kom zoo cua sov outperformed lub thicker, tsis ua hauj lwm ib tug.
Kev tshuaj xyuas qhov mob o
Rau lub rhaub hauv kev pabcuam acetone, tshuaj xyuas rau:
Nto tackiness (plasticization)
o (qhov siab nce ntawm 1-2%)
Crazing nyob rau hauv 10 × magnification
Yog hais tias tam sim no, lub rhaub yog degrading tsis hais phab ntsa thickness.
Xaus: Kev Ua Tau Ua Thickness rau Swelling Solvents
Rau acetone vapor ntawm 60 degree, lub PFA rhaub nrog cov phab ntsa tuab (2.5 hli) tuaj yeem pom cov permeation siab dua li cov phab ntsa nyias (1.5 hli) yog tias cov phab ntsa tuab tau ua tiav nrog ceev txias (dej quench, siab residual stress, low crystallinity). Acetone swells thiab plasticizes PFA, thiab cov nyhuv yog amplified los ntawm residual tensile stress. Ua kom txias qeeb thiab annealing txo permeation los ntawm 3-5 ×, ua kom tiav 1.5 hli phab ntsa ua haujlwm tsis zoo 2.5 hli phab ntsa. Thaum xaiv PFA rau cov kuab tshuaj o o, qhia meej txog kev sib xyaw ua ke thiab kev ntxhov siab tsawg. Thickness yog qhov thib ob. Txheej txheem yog thawj. Anneal PFA, ntsuas qhov kev ntxhov siab, thiab ntseeg cov ntaub ntawv - tsis yog qhov tuab. Ib phab ntsa tuab, nyuaj siab yog daim txhuam cev. Ib phab ntsa nyias nyias yog ib qho thaiv. Xaiv qhov thaiv.
