Experiment 3 (bfl).docx

POLYMER PROCESSING DESIGN LAB

POLYMER & PROCESSING DESIGN LAB REPORT NO: 02 (Blown Film Extrusion Line) SUBMITTED BY: WAJAHAT GHULAM RASOOL REGISTRATION NO: 2016-PE-12 SUBMITTED TO: SIR ENGR.MUZAMIL HAMZA GROUP NO: 1

UNIVERSITY OF ENGINEERING & TECHNOLOGY, LAHORE

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POLYMER PROCESSING DESIGN LAB

Blown Film Line Objective: To study the working of blown film extrusion and analyze the effect of processing parameters on the properties of thermoplastic. Equipment Required: Blown film extrusion line, Vernier Caliper, Thickness gauge, measuring gauge. Material Required: HDPE (Grade 912) and LLDPE (Grade 1018 Sabic) Introduction: Blown film extrusion is a technology that is the most common method to make Plastic films, especially for the packaging industry. The process involves extruding a tube of molten polymer through a die and inflating to several times its initial diameter to form a thin film bubble. This bubble is then collapsed and used as a lay-flat film or can be made into bags. Usually polyethylene is used with this process, and other materials can be used as blends with these polymers. A typical blown film (upward) is shown in fig 2.1.[1]

Fig 2.1

A schematic diagram of blown film (upward)

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POLYMER PROCESSING DESIGN LAB A combination of HDPE and LLDPE was used to perform the experiment. Typically, blown film extrusion is carried out vertically upwards, however horizontal and downward extrusion processes are now becoming more common.

Procedure:          

Processing parameters were set on the control panel of extrusion blown film Combination of LLDPE and HDPE was used in the hopper as feed Three different temperature were set according to three zones respectively, 190oC, 200oC and 220oC Molten material was then allowed to pass through die and parison was allowed to move in and upward direction. Air was blown from downward to blown up the parison Blown material was then forced to pass through the folding rods Material was then passed through nip rollers that controls the thickness of the material. After passing through nipping rollers, material was then pass through conveying rollers Finally, it was winded up on the nipping rollers. Thickness and width were measured for each sample

Results and Discussions: The effect of processing conditions on the thickness and width of plastic bag was observed as shown in table. Observations

Speed Levels

Values

Revolution Per Minute

Thickness (mm)

Lay Flat Width(mm)

Blow Up Ratio

01.

Low

50

0.03

165

2.0609

02.

Moderate

54

0.02

168

2.0984

03.

High

56

0.014

175

2.1733

It was observed that thickness of the material was decreasing as shear rate increases due to increase in screw rotation (RPM). The opaqueness in the product appears if the thickness of the product is too high due to the hindrance in light rays to pass out the sample.

Calculations: 3

POLYMER PROCESSING DESIGN LAB Blown up ratio =

Bubble Diameter 0.637 × Lay Flat Width = Die Diameter Die Diameter

Die Diameter = 63mm = 2.5 inch

For sample 1 Blown up ratio =

0.637 × Lay Flat Width 0.637 ∗ 165 = = 1.668 Die Diameter 63

For sample 2 Blown up ratio =

0.637 × Lay Flat Width 0.637 × 168 = = 1.6986 Die Diameter 63

For Sample 3

Blown up ratio =

0.637 × Lay Flat Width 0.637 × 175 = = 1.769 Die Diameter 63

Questionnaire: Q: Suggest the troubleshooting steps that can be taken to remove the surface characteristics observed during the blown film extrusion of HDPE+LLDPE? Ans: Die lines and melt fracture effect the surface properties of HDPE+LLDPE during blown film extrusion. Die lines can reduced by cleaning the die properly and refinishing the rough flow surface. Melt fracture can be reduced by lowering the viscosity of the melt which is done through increasing melt temperature. Q: Address the importance of the blown film extrusion of HDPE+LLDPE in industry and how the objective of this lab relates? Ans: Blown film extrusion of HDPE+LLDPE is very important in the industry as it is widely used in

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POLYMER PROCESSING DESIGN LAB

the packaging industry to make shrink, stretched and plastic bag film. It is also used in the consumer packaging to make packaging bags. All these applications require control thickness and other various parameter that are studied to improve the quality of the product. These parameters are studied during this laboratory. Q: What are dispersive and distributive mixing? Ans: Process where particle clamps are broken down during mixing with polymer with high shear rate is called dispersive mixing. Distributive mixing is however carried out by repeatedly straining, stretching and rearranging of layers. Distributive mixing leads to the uniform homogenous mixing of minor component into the polymers. Q: List the advantages and disadvantages of single screw extruder?

Twin Screw Extruder

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POLYMER PROCESSING DESIGN LAB

Conclusion: This process was carried to make plastic bags of different thickness. The parameters effecting thickness and width were observed and blown up ratio was calculated by different thickness of plastic bags. LLDPE and HDPE were used to carry out the process. Applications: Blown film can be used either in tube form

o

Plastic bags.

Typical applications include Industry packaging.

o o o o o o

Shrink film. Stretch film, bag film or container liners. Consumer packaging (e.g. packaging film for frozen products, shrink film for transport packaging, food wrap film, packaging bags, or form, fill and seal packaging film). Laminating film (e.g. laminating of aluminum or paper used for packaging for example milk or coffee). Barrier film (e.g. film made of raw materials such as polyamides and EVOH acting as an aroma or oxygen barrier used for packaging food, e. g. cold meats and cheese). Films for the packaging of medical products, Agricultural film (e.g. greenhouse film, crop forcing film, silage film, silage stretch film).

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POLYMER PROCESSING DESIGN LAB

Reference: 

[1] Introduction is retrieved from

http://www.appropedia.org/Blown_film_extrusion 

[2] Applications are retrieved from

http://www.bpf.co.uk/Plastipedia/Processes/Blown_Film.aspx

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