Meaning
Spherulitic growth in the bulk material is less ordered than the perpendicular crystal layers that form at the surface of a polymer melt. When a resin contacts a highly nucleating substrate or a fiber reinforcement, trans-crystallization occurs as a dense row of crystals grows into the melt. This layer creates a unique mechanical interface between the polymer and the substrate.
Perpendicular Growth
Orientation of the polymer chains is forced into a specific direction by the surface of the fiber. During trans-crystallization, the crystals cannot grow along the surface, so they are pushed outward into the bulk. This results in a columnar structure that is very different from the random spheres found elsewhere.
Interface Toughness
Transfer of stress from the resin to a reinforcement fiber is improved by this crystalline layer. Because trans-crystallization creates a tight bond, it prevents the fiber from sliding or pulling out when the part is bent. This increases the overall impact strength of a composite component.
Reinforcement Bonding
Chemical coatings on fibers are often used to trigger this specific type of growth. The presence of trans-crystallization is a sign that the resin and the fiber are well-matched. Without this layer, the mechanical properties of the part would depend only on simple friction.
