5 Molecular motions and transitions of polymers.pdf
ChapterChapterChapter 555 55 MolecularMolecular MotionsMotions andand TransitionsTransitions ofof PolymersPolymers 高分子的分子运动与转变高分子的分子运动与转变 ChapterChapterChapter 555 SimpleSimple MechanicalMechanical RelationshipsRelationships 基本力学参数基本力学参数 Modulus pliance 模量和柔量 • Tensile 拉伸 F F Tensile Stress σ= A0 拉伸应力 A0 l − l ∆l l Tensile strain ε= 0 = 0 l 拉伸应变 l0 l0 σ Young's Modulus E = ∆l 杨氏模量ε F pliance D =1 E 拉伸柔量 Numerical values of Young's modulus Material E (Pa) Copper × 1011 Polystyrene 3 × 109 Soft rubber 2 × 106 1Pa =1 N/m2 =10 dynes/cm2 =×10−5 kgf/cm2 F 0 A δγτ 0 τγ= F A tan = 1 G = δ= = τ G γ J F 0 A 剪切 剪切应力剪切应变剪切模量剪切柔量 Shear stress Shear strain Shear modulus pliance Shear • • Compression 压缩 V0 V0−∆V P Hydrostatic pressure P 流体静压力 ∆V Volume shrink ∆= 体积收缩率 V0 P Bulk modulus B = 本体模量∆V V0 Compressibility 1 ∆V V = 0 可压缩度 B P Poisson's Ratio 泊松比 −∆m m −ε υ= 0 = T ∆l l0 ε l0 l Values of Poisson's ratio Value Interpretation m0 ∆l No volume change during stretch m No lateral contraction ~ Typical values for elastomers ~ Typical values for plastics • Relationships Between E, G, B, and ν E = 3B(1− 2ν)= 2(1+ν)G For elastomer,v = E ≅ 3G Viscosity 黏度 F Shear stress τ= 切应力 A dx A dx v+dv F Shear strain γ= F 切应变 dy v dy . dγ dv Shear rate γ= = 切变速率 dt dy . η: Melt viscosity Newton's law τ=ηγ 1Pa·s = 10 poise (泊) modulus 复数模量 Complex modulus E ∗= E′+ iE′′ Simplified 复数模量 definition of E' and E" E': storage modulus * 储存模量 E = │E │ E": loss modulus 损耗模量 E′′ = tanδ tanδ: loss tangent ′ 损耗角正切,损耗因子 E Similar definitions hold for G*, η*, and other mechanical quantities
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