## Step-by-Step Solution Let's analyze each polymer for phone case suitability using the tables: ### 1. **Polypropylene (PP)** #### Properties: - **Tensile modulus:** 1.38 GPa (low, so more flexible) - **Tensile strength:** 33.8 MPa (moderate) - **Elongation:** 450% (very high, very flexible/stretchable) - **Impact strength:** 70 J/m (moderate) - **Glass transition temp:** -18°C (very low; stays flexible at room temp) - **Melting temp:** 175°C #### Suitability: - **Flexible cases:** Very high elongation and low modulus mean PP is excellent for flexible, bendable phone cases (e.g., soft, snap-on covers). - **Not extremely tough or rigid.** --- ### 2. **Poly(methylmethacrylate) (PMMA, Acrylic)** #### Properties: - **Tensile modulus:** 3.10 GPa (high, rigid) - **Tensile strength:** 62.1 MPa (good) - **Elongation:** 6% (very low, brittle) - **Impact strength:** 320 J/m (notch) (good but not as high as others) - **Glass transition temp:** Not listed, but typically ~105°C - **Melting temp:** Not listed, but decomposes before melting #### Suitability: - **Rigid, transparent cases:** High modulus (stiffness), low elongation (brittle), decently strong. - **Not flexible**—best for hard, clear cases (like "hard shell" acrylic covers). --- ### 3. **Polycarbonate (PC)** #### Properties: - **Tensile modulus:** 2.41 GPa (moderate-high) - **Tensile strength:** 60.7 MPa (good) - **Elongation:** 115% (high, ductile) - **Impact strength:** 790 J/m (very high, extremely tough) - **Glass transition temp:** 150°C (very high, stable at high temps) - **Melting temp:** 265°C #### Suitability: - **Durable, impact-resistant cases:** High modulus (somewhat rigid), **very high impact strength** (shockproof), can deform before breaking (high elongation). - **Used for rugged or protective cases** (e.g., "tough" cases, drop-proof cases). --- ## **Summary Table** | Polymer | Flexible | Rigid | Durable (Impact) | Best Use Type | |------------------|----------|-------|------------------|-------------------------| | PP | ✅ | ❌ | Moderate | Flexible, soft cases | | PMMA (Acrylic) | ❌ | ✅ | Moderate-high | Hard, clear, rigid cases| | PC | ❓ (Some) | ✅ | ✅✅✅ | Rugged, protective cases| --- ## **Final Answers** ### **Which type of phone case is each polymer best for?** 1. **Polypropylene (PP):** - **Best for:** **Flexible** phone cases - **Reason:** High elongation, low modulus (soft, bendable, not brittle) 2. **Poly(methylmethacrylate) (PMMA):** - **Best for:** **Rigid, clear** phone cases - **Reason:** High modulus, low elongation (brittle), usually transparent 3. **Polycarbonate (PC):** - **Best for:** **Durable, impact-resistant** (protective) phone cases - **Reason:** Highest impact strength, good stiffness, ductile (can absorb shocks) --- ### **Summary Sentence** - **Polypropylene** is best for flexible, soft phone cases. - **PMMA** is best for hard, rigid, transparent phone cases. - **Polycarbonate** is best for rugged, durable, and impact-resistant phone cases.