pvc calender film process

Teaching publicationsTeaching publications

MTT 655 Polymer ProcessingMTT 655 Polymer Processing

: : Calendering: Design and product controlCalendering: Design and product control

MTT 655 Polymer Processing; 1/2552 Asst. Prof. Ekachai Wimolmala

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Presentation contents

Principle of calenderingMaterialsProcessing of calenderingProductsAdvantages of calendering process Estimation of output rates and pressure


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CalenderingCalendering

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Principle of calendering

Consists rollers, Sheet or film formSimple process, Continuous processMinimum thickness of 0.05mm.L/D ratio between 2 to 3; length (L) and diameter (D)(Rollers speeds 10-200 m/min , length 0.5-2.5m, diameter 0.4-0.9m)

Adjusted by heating and cooling systemsUsually the compound mixture of the polymer and filler and/or additive using other mixers (two roll mill, internal mixers and extruders)

Product: shower curtaining, tarpaulins, table cloths, wall covering, rainwear, credit cards, conveyor belt, floorcovering, tyre, waterproofing


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Materials

Poly (vinyl chloride); PVC(reason lies on degradation calendering processing has a relatively shorter residence time)

Polyethylene; PE, Polypropylene; PP(more used in the sheet and film extrusion)

PURubber (carcass coating)


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Calendering MachinesCalendering Machines


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http://tpe-u.com/tpu/emea/en/processing/special_processes/calendering/Calendering.html


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CalenderingCalendering processprocess

I-shape

•ชุดลูกรีดไมตองทําหนาที่หลอมเหลวพลาสติก

•ทําหนาที่ปรบัขนาดความหนาของผลิตภัณฑ

•นิยมใชในอุตสาหกรรมพลาสติกในปจจุบัน

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CalenderingCalendering processprocess

Vertical L-shape

•ผลิตภัณฑแผน PVC แบบแข็ง

•โดยใชลูกรีด 2 ลูกแรกเปนตัวหลอมเหลว

พลาสติก

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Calendering processCalendering process

F-shape

•ผลิตภัณฑ PVC แบบออน

•โดยใชลูกรีด 2 ลูกแรกเปนตัวหลอมเหลว

พลาสติก

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Calendering processCalendering process

Z-shape

• ใชในการเคลอืบพลาสติกลงบน แผนผาหรอืเสนดาย

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PVC Calendering plant

D.H. Morton –Jones, Polymer Processing, CHAPMAN AND HALL


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Factors processing

Roller temperaturePressure of rollerGap sizeRotating speed of the rollersViscosity of the polymer


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ProductsProducts

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The advantages of calendering

Higher output ratesLess chance of thermal degradationMuch easies to operateLower machine and maintenance costs


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The disadvantages of calendering

Difficult of control thicknessLimited only to materials in the rubbery stateNo other product (pattern sheet and film) Difficult to control processing temperaturePremixing and compounding are required


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Estimation of output rates and Pressure in calendering

Control properties of the productBehavior of flow

Assumptions- The melt is incompressible- The flow between the rollers is isothermal and laminar- There is no slip between the rollers and the polymer- The size of the rollers is the same

- The rotating speed of the rollers is the same


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The schematic of flow along the nip in a calender


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V = 2πRN

Q = HWV

Pmax = 16ηvd3

RH0

V = velocity of the sheetQ = total output rate P = maximum pressureR = radius of the rollers (m)N = rotating speed of the roller (rpm) H0 = size of the nip gapH = thickness of the sheetW = width of the sheet (m)d = distance nip gap to sheet (m)


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ExampleIn PVC sheet manufacture by calendering, estimate the thickness of the sheet and the maximum pressure developed on the nip of rollers. Roller diameter 50 cm and width 700 cm. The rotating speed of the rollers is 20 rpm. The feed rate of the PVC compound having a viscosity of 104 Ns.m-2

is 0.45x10-3 m.s.-1 The nip gap is 0.2 mm. The PVC compound has a viscosity of 104 Ns.m-2 . The d value is 30 mm.

SolThe velocity of the sheet is determined byV = 2πRN =2X3.14X0.25X20=31.4 m.min-1

Therefore the thickness is:H = Q = 0.45X10-3X60 = 0.001 m

WV 0.70x31.4And the maximum pressure is :Pmax = 16ηVd3 = 16x104x(31.4x60)x(0.03)3 = 1.63x108 N.m-2

RH0 0.25X0.0002


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Thank youThank you

pvc calender film process

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