Qumlangan tashqi yuzasi (Ra 2,0 mkm) bo'lgan PFA isitgichi silliq sirt bilan solishtirganda polimer ifloslanish xizmatida tozalash chastotasini kamaytira oladimi?

Cho'kmalar polimerni ifloslantirish xizmatlarida (masalan, polimer eritmalari, lateks emulsiyalari yoki yopishqoq organik eritmalar) isitgich yuzasiga mahkam yopishadi, issiqlik uzatishni kamaytiradi va tez-tez tozalashni talab qiladi. Silliq sirt bilan solishtirganda (Ra<0.2 µm), a PFA heater with a sandblasted outer surface (Ra 2.0 µm) can cut cleaning frequency by 40–60%. The actual contact area between the polymer and the heater is decreased by the roughened surface. The Cassie-Baxter model states that a textured surface keeps the polymer from soaking the entire surface by trapping air pockets beneath the fouling layer. Only the tips of the roughness peaks are adhered to by the deposit, which makes it easier to remove during cleaning or even self-clean in flow conditions. However, if the polymer has low-viscosity and flows into the cracks, the roughened surface may develop deposits in the valleys. The sandblasted surface is much superior for high-viscosity polymer melts (>10 000 cP); past yopishqoqlikdagi monomerlar uchun silliq sirtni tozalash osonroq bo'lishi mumkin-<500 cP).

Silliq va qo'pol PFA ifloslanish mexanizmlari
Polimer va to'liq ko'rinadigan joy o'rtasidagi yaqin aloqa silliq PFA yuzasi (Ra<0.2 µm). Strong adhesion is produced by van der Waals forces. The deposit creates a homogeneous, continuous coating that is challenging to mechanically or chemically remove. The coating breaks off in tiny pieces during cleaning, leaving debris in its wake.

Qumlangan sirtda balandligi 2-4 mkm (Ra 2,0 mkm) bo'lgan mayda cho'qqilar va vodiylar mavjud. Faqat tepaliklar polimer bilan aloqa qiladi. Ko'rinadigan maydonning atigi 10-30 foizi aloqada. Tegishli yopishqoqlik kuchining pasayishi mavjud. Uzluksiz plyonka sifatida hosil bo'lish o'rniga, cho'kindi cho'qqilarda alohida orollar sifatida paydo bo'ladi. Suyuqlik harakati yoki yorug'likni tozalash bu orollarni osongina kesib tashlashi mumkin. Vodiylar, shuningdek, suyuqlik yoki havoni ushlab turish orqali ozod qiluvchi vosita sifatida xizmat qiladi.

Har xil polimer turlari uchun tozalash chastotasini kamaytirish
Ishlash haroratidagi polimer yopishqoqligi turi (cP) Asosiy ifloslanish mexanizmi Tozalash chastotasi (silliq sirt) Tozalash chastotasi (Ra 2,0 mkm) pasayish (%)
HDPE (polietilen eritmasi) 5 000–20 000 Film-hosil qiluvchi, yopishtiruvchi Har 7 kunda Har 14–21 kunda 50–66%
3000–15000 polipropilen eritmasi Yelim Har 5 kunda Har 10–15 kunda 50–67%
10,000–50,000 issiq eritma yopishtiruvchi (EVA) Har uch kunda birlashtiruvchi va yopishtiruvchi57-70% har 7-10 kunda
Akril lateks emulsiyasi: 100-500 Adezyon va cho'kma Har 14 kunda; har 18-22 kunda; har 20-36%
Stirol monomeri<10 Wetting + polymerization Every two days Every three to four days 33–50%
1000–5000 poliuretan prepolimerKimyoviy payvandlash 33–50% har 10 kunda, har 15–20 kunda
50–200 Eritilgan mumning kristallanishi Har 30 kunda 0% (mum yopishmaydi) Har 30 kunda (o‘zgarishsiz)
Polimerni chiqarish uchun ideal pürüzlülük darajalari
Polimer ifloslanishini kamaytirish uchun ideal qumli sirt quyidagilarga ega:

Ra: 1,5–2,5 mkm (juda qo'pol, vodiylar polimer bilan to'ldiriladi; juda silliq, ozgina afzallik)

Choʻqqisi-to-vodiy Rz: 10–15 mkm

Eng yuqori ajralish: 20–50 mikron

Yer yuzasining 30–50% ni ochiq maydon (vodiylar) tashkil etadi.

Sirtni tayyorlash uchun 3-4 bar havo bosimida alyuminiy oksidi qumidan (hajmi 100–150 mkm) foydalaning. O'rnatilgan qum zarralaridan qutulish uchun qumdan keyin ehtiyotkorlik bilan tozalang. Cho'qqilarni tekislash yoki jilolashdan saqlaning.

Maydondagi misol
Issiq eritma yopishtiruvchi aplikatorda silliq PFA isitgichi ishlatilgan. Har uch kunda bir marta yopishtiruvchi isitgichni ifloslantirib, tozalash uchun ikki-soat yopishni talab qildi. Zavodda bir xil vatt zichligiga ega bo'lgan qumli PFA isitgichi (Ra 2,0 mkm) o'rnatildi. Tozalash oralig'iga o'n kun qo'shildi. Yillik hosildorlikning 120 soatlik (15 kunlik) o'sishi kuzatildi. Qum bilan tozalash har bir isitgich uchun 50 ta (har bir isitgich uchun 550 ta) yoki yiliga 55 000 dollarga ishlamay qolish vaqtini oshirdi.

Cheklovlar va qachon qumtoshdan tozalash kerak
Qum bilan tozalash quyidagilar uchun foydali emas:

past viskoziteli suyuqliklar (<500 cP) that completely soak the surface as they flow into the valleys. Fouling and contact area are subsequently increased by the roughness.

Zarrachalar bilan toʻldirilgan{0}}korroziv muhit: notekis sirt korroziy tuzlarni ushlab, chuqurchalar paydo boʻlishini tezlashtirishi mumkin.

Yuqori-tozalikdagi ilovalar: mahsulot qum bilan tozalash natijasida oʻrnatilgan qum zarralari bilan ifloslanishi mumkin. Buning o'rniga silliq yoki elektropolizlangan yuzalarni tanlang.

Juda yupqa PFA devorlari (1,5 mm dan kam): Qumlash devorlarning qalinligini 0,05 dan 0,1 mm gacha kamaytirish orqali zaiflashishi mumkin.

Qumlangan yuzalarni qanday tozalash kerak
Qumlangan PFA isitgichni tozalash uchun yumshoq neylon cho'tkalar yoki past bosimli suv oqimidan (10–20 bar) foydalaning. Metall qirg'ichlar qo'pollikni buzadi va cho'qqilarni tekislaydi, shuning uchun ularni ishlatishdan saqlaning. Kimyoviy tozalash (erituvchi emdirish) sirtni mexanik ravishda silamaganligi sababli, tavsiya etiladi. Tozalashdan keyin sirt pürüzlülüğünü tekshirish uchun profilometrdan foydalaning. Ra 1,0 mkm dan pastga tushgan bo'lsa, isitgichni almashtiring yoki qayta to'plang.

Xulosa qilib aytganda, sirt qum bilan qoplangan (Ra 2,0 mkm). Yopishqoqlik yuqori{2}}polimer eritmalari uchun tozalash chastotasini 40–60% ga qisqartiradi
A sandblasted outer surface (Ra 2.0 µm) for PFA heaters in polymer fouling service with high-viscosity melts (>5000 cP) silliq sirt bilan solishtirganda tozalash chastotasini 40-60% ga kamaytiradi. Haqiqiy aloqa maydonini kamaytirish orqali pürüzlülük konlarni olib tashlashni osonlashtiradi va doimiy plyonka shakllanishini to'xtatadi. Past viskoziteli suyuqliklar uchun silliq sirt yaxshiroq mos keladi (<500 cP). The cheap cost of sandblasting ($50–100 per heater) is offset by longer cleaning cycle intervals and less downtime. For sticky polymer solutions, polyolefin melts, and hot melt adhesives, specify sandblasted PFA. While a smooth surface encourages fouling, a rough surface discourages it. Select the release's roughness. Your production schedule will be grateful.