Chemical Resistance Thermoplastics

Overview

Engineering reference data for Chemical Resistance Thermoplastics in material science and properties.

Key Formulas

Stress

$\sigma = \frac{F}{A}$

Force per unit area.

Strain

$\varepsilon = \frac{\Delta L}{L_0}$

Change in length per original length.

Hooke's Law

$\sigma = E \varepsilon$

Stress proportional to strain in elastic region.

Thermal Expansion

$\Delta L = \alpha L_0 \Delta T$

Length change due to temperature.

Variables

Symbol	Description	Unit
$\sigma$	Stress	Pa
$\varepsilon$	Strain	—
$E$	Young's modulus	Pa
$\alpha$	Thermal expansion coefficient	1/°C
$\Delta T$	Temperature change	°C

Chemical Resistance Factors

The chemical resistance of thermoplastics is influenced by several key factors including the chemical concentration, temperature, exposure time, and the specific formulation of the plastic material.

Thermoplastic Material Reference

The following table provides a quick reference for common thermoplastic piping materials and their general chemical resistance properties.

Key Calculation Formulas

When evaluating chemical resistance, two fundamental quantities are often calculated: the chemical's permeation rate through the pipe wall and the diffusion coefficient.

The chemical permeation rate ($J$) can be estimated using Fick's first law for steady-state diffusion:

$J = -D \frac{\Delta C}{\Delta x}$

Where:

• $J$ is the permeation flux (kg/m²·s).
• $D$ is the diffusion coefficient (m²/s).
• $\Delta C$ is the concentration difference across the wall (kg/m³).
• $\Delta x$ is the pipe wall thickness (m).

The diffusion coefficient ($D$) itself is often temperature-dependent and can be modeled with an Arrhenius-type equation:

$D = D_0 \exp\left(-\frac{E_a}{RT}\right)$

Where:

• $D_0$ is the pre-exponential factor (m²/s).
• $E_a$ is the activation energy for diffusion (J/mol).
• $R$ is the universal gas constant (8.314 J/mol·K).
• $T$ is the absolute temperature (K).

References

• Original Source