semicrystalijn

Semicrystalijn is a term used in materials science, particularly in Dutch-language literature, to describe materials that contain both crystalline and amorphous phases. It is commonly applied to polymers but can also refer to certain metals or composites that exhibit partially ordered domains. The degree of crystallinity influences a range of properties and processing behavior.

In semicrystalijn polymers, crystalline domains (lamellae) are dispersed within an amorphous matrix. The crystalline fraction quantifies how much of the material is ordered. Crystallization occurs during cooling from a melt or from solution, with morphology shaped by nucleation rates, cooling rate, and chain mobility. Typical structures include spherulites and lamellar stacks, whose size and arrangement affect mechanical and thermal characteristics.

Properties and processing are closely tied to crystallinity. Higher crystallinity generally increases stiffness, tensile modulus, chemical resistance, and barrier properties, and raises the melting temperature. It can, however, reduce impact toughness and optical clarity in some films. Processing conditions such as cooling rate, annealing, and mechanical orientation can modify the crystallinity and the resulting microstructure, enabling tailored performance.

Examples and applications are dominated by semicrystalline polymers such as polyethylene, polypropylene, and polyamides. These materials are used in packaging films, fibers, automotive components, and barrier coatings. Some metals and inorganic–organic composites also exhibit partial crystallinity, with analogous effects on properties and processing.

Characterization typically involves differential scanning calorimetry to assess heat of fusion and crystallinity, X-ray diffraction to identify crystalline phases, and microscopy or scattering techniques (TEM, SAXS) to reveal morphology and lamellar spacing.