What are spherulites discuss structure of crystalline polymers?
What are spherulites discuss structure of crystalline polymers?
The spherulites are radiating fibrous structures and the various observed extinction effects were interpreted in terms of such fibrous units. These extinction effects varied with the different materials and also for a particular substance with conditions of crystallization.
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.
What is the crystal structure of polymers?
Crystalline polymer structure is described by a three-phase model, that is, a crystalline phase, an amorphous phase, and mesosphere (crystalline and amorphous interface). The fact is that radiation cross-linking of the crystalline polymer mainly occurs in the amorphous region.
What are the characteristics of crystalline polymer?
Highly crystalline polymers are rigid, high melting, and less affected by solvent penetration. Crystallinity makes a polymers strong, but also lowers their impact resistance.
What are spherulites explain?
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. Perlites are spherical structures that have onion-like partings in a glassy rock.
How do spherulites form?
Spherulites form during so-called devitrification processes (“de-glassing” processes) in obsidan, a natural glass. During devitrification the glass slowly crystallizes to minerals like cristobalite and feldspars. If growing spherulites impinge on one another, polyhedral boundaries between them are formed (Fig. 2).
How is a spherulites formed?
Spherulites frequently have a radiating structure that results from an intergrowth of quartz and orthoclase. These spherical bodies are thought to have formed as a consequence of rapid mineral growth after nucleation, possibly on an accumulation of volatiles.
Are polymers amorphous or crystalline?
| Amorphous vs Crystalline Polymers | |
|---|---|
| Amorphous polymers are polymers that have no ordered pattern in its molecular structure. | Crystalline polymers are polymers that have a well-organized structure. |
| Amorphous polymers have a low chemical resistance. | Crystalline polymers have a high chemical resistance. |
| Polymer Chains |
Why are some polymers crystalline?
Polymers can crystallize upon cooling from melting, mechanical stretching or solvent evaporation. Crystallization affects optical, mechanical, thermal and chemical properties of the polymer.
Are Spherulites fully crystalline?
The linear size of the panels are (a) 220 µm, (b) 960 µm, (c) 2.4 mm, (d) 2.5 µm, (e) 7.6 µm, (f) 550 µm, (g) 2.5 µm, (h) 20 µm, (i) 250 µm, and (j) 1.7 µm, respectively. FIG. 2. Concepts for the formation of category 1 and 2 spherulites.
How do you optimize Spherulites?
Take one of your drops with lots of crystals (spherulites) and vortex it vigorously to break the crystals (called a seed stock). This will produce micro-crystals that you can’t see anymore by naked eye. Then do your normal drop size 2+2 for instance, and then add 1uL of seed stock.
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.
What is the structure of polymer spherulite?
In all the spherulites so far described the structure is based on lamellar crystals radiating outwards from the centre. In this way the early optical observation of polymer spherulites being birefringent entities with radial symmetry may be explained.
What is spherulite crystallization?
Polymeric and non-polymeric materials often crystallize as spherulites when crystallized from viscous melts or solutions at large undercooling. The essential component of a spherulite is fibrillar crystals that grow in predominantly radial directions and branch irregularly.
What is a banded spherulite?
Spherulite blend morphology is linked to the competition between radial growth rate G and diffusivity D of the diluent, expressed as the diffusion length δ. Polymer crystals in which chain helices all have the same sense show banded spherulites, as do crystals in which the chain axes are not perpendicular to the basal surfaces.
What is the general shape of polymer crystals?
•All polymer single crystals seem to have the same general appearance and structure. In their simplest form, they appear in the electron microscope as thin, flat platelets on the order of 100 to 200 Åthick and several microns in lateral dimensions Folded Chains Polymers form stacks of these folded chains.
