Introduction to Polymers
- What is the difference between thermoplastic and thermosetting polymers? In one line Thermoplastics soften on heating and harden on cooling repeatedly because their linear chains are held by weak forces, while the... 1
- How are polymers classified by origin, structure, polymerisation type and composition? In one line Polymers are classified in several ways: by source (natural, semi-synthetic, synthetic), by chain structure (linear, branched, c... 1
- What are number average and weight average molecular weights of a polymer and what is polydispersity? In one line Because a polymer sample contains chains of many different lengths, its molecular weight is expressed as an average: the number... 1
- How do you calculate number average and weight average molecular weight in a numerical? In one line Make a table of N_i, M_i, N_iM_i and N_iM_i², then use M_n = ΣN_iM_i/ΣN_i and M_w = ΣN_iM_i²/ΣN_iM_i. Explained simply The metho... 1
- What is the difference between crystalline and amorphous polymers, and what controls crystallinity? In one line In crystalline regions polymer chains are packed in an ordered, regular way, while in amorphous regions they are randomly coiled... 1
- What is the glass transition temperature of a polymer and what factors affect it? In one line The glass transition temperature (T_g) is the temperature below which an amorphous polymer is hard, rigid and glassy, and above... 1
- What do hardness, tensile strength, creep, fatigue and impact resistance mean for polymers? In one line These mechanical properties describe how a polymer responds to force: resistance to indentation (hardness), maximum pulling stre... 1
- Why are polymers good electrical insulators, and what are dielectric strength, insulation resistance and surface resistivity? In one line Most polymers have no free electrons or ions, so they resist current flow; their insulating quality is described by dielectric s... 1
- What optical properties of polymers matter: refractive index, transmittance, photoelectric property and colour? In one line Optical properties describe how a polymer interacts with light: how much it bends light (refractive index), how much light passe... 1
- What are polymers and macromolecules, and what do monomer and degree of polymerisation mean? In one line A polymer is a macromolecule (very large molecule, molecular weight typically 10³ to 10⁷) built by joining many small repeating... 1
- What chemical bonds and intermolecular forces hold polymer chains together? In one line Atoms within a polymer chain are joined by strong primary covalent bonds, while separate chains are held together by weaker seco... 1
- Explain viscoelasticity property of polymer. Viscoelasticity is the property of polymers by which they show both elastic (solid-like) and viscous (liquid-like) behaviour when deformed.... 1
- In a polymer sample 30% molecules have a molecular mass 20,000, 40% have molecular mass 30,000 and the 30% have 60,000. Calculate the weight average, number average molecular weight and polydispersity of polymer sample. Given (number fractions of molecules): take 100 molecules, so N_i = 30, 40, 30. N_iM_iN_iM_iN_iM_i² 3020,0006.0 × 10⁵1.2 × 10¹⁰ 4030,00012.0... 1
- Give the definitions and significance of following properties of polymer. Tensile strength, insulation resistance and refractive index. 1. Tensile strength Definition: the maximum tensile (pulling) stress a polymer specimen can withstand before it breaks: tensile strength = m... 1
- Define the tensile strength of a polymer and explain its significance. Tensile strength is the maximum tensile (stretching) stress that a polymer can withstand before it breaks (fractures): Tensile strength = ma... 1
- Explain all types of chemical bonds existing in polymers. Polymers contain primary (covalent) bonds along the chain and secondary (intermolecular) forces between chains. Together they decide the str... 1
- Write short notes on crystallinity, number average molecular weight and fatigue of polymers. 1. Crystallinity Polymers have crystalline regions, where chains are packed in an ordered, regular way (crystallites or lamellae formed by f... 1
- Explain the term ‘glass transition temperature’ with significance. Glass transition temperature (T_g) is the temperature below which an amorphous polymer (or the amorphous part of a polymer) is hard, rigid a... 1
- A Polymer has the following composition: 100 Molecules of molecular mass 1000, 200 molecules of molecular mass 2000 and 500 molecules of molecular mass 5000. Calculate the number and weight average of molecular weight and the polydispersity index. (P… Given: N_iM_iN_iM_iN_iM_i² 10010001.0 × 10⁵1.0 × 10⁸ 20020004.0 × 10⁵8.0 × 10⁸ 500500025.0 × 10⁵125.0 × 10⁸ Σ = 80030.0 × 10⁵134.0 × 10⁸ Num... 1
- Explain following properties of polymer a) Electrical b) Optical. a) Electrical properties – most polymers are good insulators because they have no free electrons or ions. Dielectric strength: the maximum e... 1