Amorphous Polymers

Transition Temperature

Molecular mobility in these materials remains highly restricted below a specific thermal threshold. This threshold represents the glass transition temperature where the polymer transitions from a rigid, glassy state to a flexible, rubbery phase. For amorphous polymers, this transition governs the upper limit for continuous service temperature, making it a critical specification on the material datasheet.

Processing Performance

Injection moulding of disorganized chain systems requires high injection pressures to overcome the high melt viscosity of the disordered chains. Unlike semi-crystalline alternatives, amorphous polymers experience a gradual viscosity drop with increasing temperature, meaning that melt flow is highly dependent on shear rate. Run-to-run consistency depends on maintaining precise melt and mould temperatures to prevent incomplete mold filling or flow marks.

Inadequate control of these temperature parameters can lock in high residual stresses, which subsequently lead to stress cracking when the finished parts are exposed to cleaning solvents or environmental stressors.

Shrinkage Rate

Post-moulding dimensional changes are exceptionally low because the lack of recrystallization prevents major density shifts during cooling. Industrial components made of amorphous polymers typically exhibit isotropic shrinkage of less than one percent. In contrast, semi-crystalline materials show much higher, non-uniform shrinkage that often induces warping in the finished part.