PKSC 102- plastics/polymers
PKSC 102- plastics/polymers 81499 - PKSC 1020 - 001
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81499 - PKSC 1020 - 001
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This 4 page Class Notes was uploaded by Addie Pearson on Tuesday February 23, 2016. The Class Notes belongs to 81499 - PKSC 1020 - 001 at Clemson University taught by Heather P Batt in Fall 2015. Since its upload, it has received 24 views. For similar materials see Introduction to Packaging Science in Nutrition and Food Sciences at Clemson University.
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Date Created: 02/23/16
POLYMERS Back ground - Packaging is the largest user of plastics, ~30% of total plastics on market? - “plastics”=”Polymers” (for many purposes) - 1843- Malaysia- Gutta Percha derived from latex from tropical trees (Getah- sap) (Percha- strips of cloth). Used for knife handles, picture frames - Alfred Critchlow- pro-phy-lac-tic Brush Co. dues and presses for shellac, straw pulp and gutta percha for buttons and toothbrush handles - Civil war- $10,000 reward for substitute for ivory billiard balls. John Hyatt developed celluloid from cellulose nitrate and camphor. Eventually lead to cellophane. - Dr. Leo Baekeland- patented controlled reaction between phenol and formaldehyde o Resulted in Bakelite- first synthetic resin - 1930’s- polyethylene first developed - Today- Polyethylene is the most widely used packaging plastic o 13.3 billion lbs us used for packaging o Six times more PE used than the net most popularly used plastic (polypropylene) Nomenclature - Film- less than or equal to 0.001” thick - Thickness terminology o Gauge o Mil o Inches o 0.001”= 1 mil = 100 gauge - Sheet- greater than 1 mil thickness Common Types of Plastics ALL PLASTICS BASED ON CARBON UNIT C Polyethylene (PE) H H high pressure H H H H H - C = C - - C – C – C – C – C - H H (15-45,000 psi) H H H H H Product of Polyethylene Polyvinyl chloride (PVC) H Cl Cl H Cl H Cl H H – C C – H + HCl - C = C - - C – C – C – C – C – C - acetylene hydrochloric H H H H H H H H acid Polyvinyl Chloride PE- POLYETHYLENE available in different densities (LPDE, HDPE, LLDPE) used for bread bag to milk bottles PP- POLYPROPYLENE liing hinge. Strong, stiff, used for caps with hinges used for closures. PET- POLYESTER used for fresh meat overwrap, worse oxygen barrier. PVDC- POLYVINYLIDENE CHLORIDE- saran wrap, used as a parrier coating, best oygen barrier. EVAL is a trade name, common abbreviation EVOH PVAL is commonly abbreviated PVOH HDPE- HIGH DENSITY POLYETHYLENE- less branching and more ordered arrangement LDPE- LOW DENSITY POLYETHYLENE- less branching and more spread out LLDPE- combo of HDPE & LDPE, it is more ordered but still spread out. Yield- amount of finished material (area) than can be produced from raw material (lbs or in^2/lbs). LOWER DENSITY = HIGHER YIELD Thermoset- when exposed to high temperatures, bonds are set and can’t be unlocked. Thermoplastic- when exposed to high temperatures, bonds are loose and form upon cooling ORIENTATIONS - Process of aligning molecules in the direction in which they are being pulled. o MD= machine direction (pulled upwards) o CD= cross direction (as bubble expands) o Biaxially oriented film= film that has been stretched, oriented, in MD and CP direction. - Important for shrink film- necessary for equal strength Injection modling- used for cups, caps small tubes etc. Extrusion blow molding - Parison- hollow tube which exits extruder and will be inflated into the final shape of a bottle. Injection blow molding - Two step expansion - Preform- detailed finish and initial body formed, reheated and expansion to form bottle - Uses a pin and air to help stretch preform into the final bottle shape - Will also have dimple at the bottom Adv. - Single mold - Readily produced Disadv. - Handle is difficult Thermoforming - For cups, blisters, trays, etc Advantages of plastics - Very versatile - Light weight - Unbreakable - Low energy for production compared to glass and metal Disadvantages of plastics - Petroleum based (mostly) - Non-degradable- perception problem - Recycle issue- difficult to remake SAME package from post consumer waste - Not totally inert- must select carefully - Guitar pick holder - Bike attachment
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