What are spherulites in polymers?
In polymer physics, spherulites (from Greek sphaira = ball and lithos = stone) are spherical semicrystalline regions inside non-branched linear polymers. Spherulites are composed of highly ordered lamellae, which result in higher density, hardness, but also brittleness when compared to disordered regions in a polymer.
How do spherulites grow?
Many structural materials (metal alloys, polymers, minerals, etc.) are formed by quenching liquids into crystalline solids. This highly nonequilibrium process often leads to polycrystalline growth patterns that are broadly termed “spherulites” because of their large-scale average spherical shape.
Is a Spherulite crystalline?
Under the microscope the spherulites are of circular outline and are composed of thin divergent fibers that are crystalline as verified with polarized light.
Why do spherulites show a Maltese cross?
The Maltese cross is seen because polymers are birefringent. Polarised light cannot travel through a crystalline polymer if the direction of the polarisation of the light is perpendicular to the direction of carbon chain in the polymer.
Why do spherulites form in polymers?
After nucleation, growth in most polymers is faster in one preferred direction. This means that polymer crystals grow in helical strands radiating from a nucleation point. Such growth leads to the formation of structures called spherulites.
Why are amorphous polymers transparent?
Hi; Crystalline polymers are usually opaque because of light scattering on the numerous boundaries between the crystalline and amorphous regions. Optically transparent polymers are usually amorphous, because crystallites scatter light giving a milky/opaque appearance.
Is PP amorphous or crystalline?
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins and is partially crystalline and non-polar.
What is Maltese cross in urine?
Round particles producing birefringent Maltese crosses under polarized light are commonly seen in the urinary sediment of patients with a nephrotic syndrome. The appearance of the Maltese crosses is due to the birefringence of lipid droplets, which consist mainly of cholesterol esters.
What does the Maltese cross look like?
The Maltese cross is an eight-pointed cross formed by four v-shaped elements that each meet at its vertex. The shape itself has origins dating back to Byzantine culture in the 6th century. It was originally a white cross placed on a red or black backdrop.
What is the diameter of spherulite?
Their formation is associated with crystallization of polymers from the melt and is controlled by several parameters such as the number of nucleation sites, structure of the polymer molecules, cooling rate, etc. Depending on those parameters, spherulite diameter may vary in a wide range from a few micrometers to millimeters.
What type of rock is spherulite?
(Show more) spherulite, spherical body generally occurring in glassy rocks, especially silica-rich rhyolites. Spherulites frequently have a radiating structure that results from an intergrowth of quartz and orthoclase.
What are spherulites in insulin?
Structure of Spherulites in Insulin, β-Lactoglobulin, and Amyloid β | ACS Omega Under denaturing conditions such as low pH and elevated temperatures, proteins in vitro can misfold and aggregate to form long rigid rods called amyloid fibrils; further self-assembly can lead to larger structures termed spherulites.
Why do spherulites have semicrystalline structure?
The largest surfaces of the lamellae are terminated by molecular bends and kinks, and growth in this direction results in disordered regions. Therefore, spherulites have semicrystalline structure where highly ordered lamellae plates are interrupted by amorphous regions.