高分子材料加工技术专业英语 Introduction 22.Polymer Families.ppt

Arrangement + Effects Chain Flexibility – Side Groups Having a Benzene ring attached to one side of the chain will greatly affect the stiffness. Polystyrene is very stiff to the point of being brittle (CD cases) Polystyrene (PS) Crystalline – No (Benzene ring makes it too rigid) Hygroscopic – No (not O or N) Glass Transition – High (210 F) Flammability – Yes only C-H bonds Polystyrene (PS) Polystyrene (PS) Options: Approximate tensile strength – note PP, PVC approach engineered thermoplastics!! * 80% of all plastics are thermo plastics. 80% of all thermoplastics are either PE, PP, PVC and PS * Bob, explain your experience here with PEEK – go to the website, note carbon reinforced peek has high compressive strength and low coefficient of friction but costs $100/lb. UHMW, low coef of friction but low compression strength. Solution: cast nylon!! 80% commodity = lower price by shear volume. Also, where are engineered plastics used?? * /photos/uncategorized/sidecar.jpg * /images/J7306.jpg * /images/products/gallon_big.jpg * /d540a07/mrYuk.JPG * UHMWPE does not melt like lower molecular weight grades, at 150C still behaves like rubber. Difficult to injection mold!! * /prod_images_blowup/Coke-20-oz-Bottles1.jpg * Show chemical formla * /wikipedia/commons/thumb/c/c7/Mint_box_polypropylene_lid.JPG/432px-Mint_box_polypropylene_lid.JPG * See page 113 and 114 for definition of copolymer and homopolymer – bob define this better next year in chapter 4 * * * /photoTransparent_Slim_CD_Case.jpg * Chapter 8 – Polymer Families Recall polymer categories: Plastics: Thermoplastics Engineered and commodity Thermosets Engineered and commodity Elastomers: Thermosets and thermoplastics Most plastics are thermoplastics. Most thermoplastics are commodity Most commodity thermoplastics are PE, PP, PVC and PS – This accounts for 80% of all thermoplastics!!! Commodity vs. Engineered Thermoplastics Commodity thermoplastics $1.50/lb (’06) Engineered thermoplastics $1.50 to $6.