EXTRUSION MOULDING The plastic granules are moved down by the feed screw and heated up. The molten plastic is forced through the series of dies.
The plastic extrusion iscooled by passing itthrough a water bath orjets of air.The extrusion continuesuntil it reaches itspredetermined length.It is then cut off tolength and the cycle ofoperations continues.
CONTD.. Bubble casting For thermoplastic materials only
THERMO FORMING 3 Dimensional articles Combination of Extrusion and Compression Moulding. 2 Steps: Heating & Forming Forming can be achieved by i) Vacuums Thermoformingii) Pressure Thermoforming iii) Mechanical Thermoforming
PREPARATION (i) Hydrogenation Of Acetylene H 2 / Pd CH CH CH 2 CH 2 Acetylene Ethylene(ii) Dehydration of ethanol Dehydration Catalyst CH 3CH 2OH CH 2 CH 2 H 2O Ethanol Ethylene(iii) Dehydrogenation of ethane Dehydrogen ation Catalyst CH 3 CH 3 CH 2 CH 2 H2 Ethane Ethylene
TYPES OF PE LDPE BenzoylPeroxide 80 250 C 1500 atmn[CH 2 CH 2 ] [ CH 2 CH 2 ]n HDPE Al ( C2 H 5 ) 3 120 C 6 7 atm n[CH 2 CH 2 ] [ CH 2 CH 2 ]n
Low Density PE High Density PE Obtained at High P Obtained at low P Branched Structure Linear structure Low density 0.91-0.925 High density 0.95- g / cm 3 0.97 g / cm 3 Low M.P(115ºC) Low Crystallinity High M.P(135ºC) High Water & gas High Crystallinity permeability Low Water & gas Used for making toys , permeability mugs , carry bags. For making milk bottles ,industrial containers , for domestic water & gas piping.
PROPERTIES OF PE Rigid, waxy, white, translucent, non-polar material Chemical resistance to strong acids, alkalis and salt solution Good electrical insulator Resistant to atmospheric conditions