Part II: Classification of polymer

Classification of Polymers (ref. 4 p.8-23) By origin: natural polymers, semi-synthetic polymers, synthetic polymers By response to temperature: thermoplastics, thermosets By polymerization methods: addition(chainwise), condensation (stepwise) By architecture of chain: linear, crosslink, branched, dendritic By no. of monomer types in polymer: homopolymer (PE, PP, PS, PVC, PMMA, PC, PET), copolymer (SBR, NBR), terpolymer (ABS) By orientation of polymer chains: amorphous, semi-crystalline

Classification(1) : By origin polymer Classification(1) : By origin inorganic organic natural synthetic Natural synthetic - silicone rubber - boron nitrile soil sand adhesive fiber paints plastic rubber glass bricks cement ceramics โพลิซักกาไรด์ (polysaccharides) protein โพลิไอโซพรีนในรูปของยางธรรมชาติ (polyisoprene) collagen Kesine (from milk) Ref: พิชิต เลี่ยมพิพัฒน์ พ.ศ. 2542 starch cellulose Chitin, Chitosan

Examples of some natural polymers

Examples of some synthetic polymers Polymers originated from ethylene Polymers with O in molecules Polymers with O and N in molecules Thermosetting Polymers

Polymers Originated from Ethylene Ref: พิชิต เลี่ยมพิพัฒน์ พ.ศ. 2542

Polymers Originated from Ethylene (cont.) Polyvinylidine chloride 3 Ref: พิชิต เลี่ยมพิพัฒน์ พ.ศ. 2542

Polymers with O in molecules Ref: พิชิต เลี่ยมพิพัฒน์ พ.ศ.2542

Polymers with O and N in molecules The 3 most important are: polyester, polyamide, polyurethane

Polymers with O and N in molecules Ref: พิชิต เลี่ยมพิพัฒน์ พ.ศ. 2542

Thermosetting Polymers Phenol-formaldehyde Urea-formaldehyde Ref: พิชิต เลี่ยมพิพัฒน์ พ.ศ. 2542

Thermosetting Polymers (cont.) Melamine-formaldehyde

Classification(2): Response to temperature Thermoplastic - ex. linear and branched polymers Polymers held together by 2nd bonds. When T 2nd bonds break lose polymer flow Thermoset - Polymer chains held together with primary bond (crosslink) bond btw. polymers and inside polymers break at same temp. polymer degrade special case ex. Cellulose held by several 2nd bonds(hydrogen bonding) but exhibit thermoset behavior  modified to thermoplastic by making “cellulose acetate” ex. Polytetrafluoroethylene(teflon, PTFE) held by several 2nd bonds (van der Waal force btw. F-F) but exhibit thermoset behavior

Polymer Thermoplastic Elastomer Thermoset Crystalline Amorphous ( lightly cross linked) (heavily cross linked ) Network Cross linked polymers Linear/branched polymers (no cross linked)

Bonding in polymers Type of bonds Primary covalent Bonding in polymers is relevant to characteristic thermal response of the polymers Type of bonds Primary covalent Hydrogen bond ex. (-CO-NH-) Dipole interaction van der Waals (special case: PTFE(Teflon) has very strong van der Waals force that Teflon cannot melt) ionic secondary bond (Ref:S.L. Rosen, John Wiley & Sons 1993)

Bonding in polymers Type of bonds - Secondary Bonds: - Primary Bonds: Dipole interaction Hydrogen bond covalent ionic bond van der Waals interaction

Bond distances and strengths ref.:S.L. Roson,John Wiley &Sons 1993 = depth of potential energy required to break the bond

Bond Parameters Approximate bond strength and interatomic distances of the bond - note that primary covalent bond is much stronger than secondary bond. ดังนั้น primary covalent bond dissociate last when kT reach its activation energy) ref.:S.L. Roson,John Wiley &Sons 1993

Model structures of thermoplastic vs. thermoset Ref: พิชิต เลี่ยมพิพัฒน์ พ.ศ. 2542

Common Thermosetting Polymers (Ref: พิชิต เลี่ยมพิพัฒน์ พ.ศ. 2542) Amino (have N in structure) - Urea - Melamine Epoxy Phenolic Unsat. Polyester Silicone Polyurethane Urea-formaldehyde