What is the crystallization temperature of polypropylene?

The α2-form can be obtained at high crystallization temperature above 145°C and α1 can be observed at low crystallization temperatures below 132°C. The mixed α-spherulites can be obtained between 132°C and 145°C.

What are the factors affecting crystalline melting point of polymers?

The polymer melting point Tm is increased if the double bonds, aromatic groups, bulky or large side groups are present in the polymer chain, because they restrict the flexibility of the chain. The branching of chains causes the reduction of melting point, as defects are produced because of the branching.

What is isotactic polymer?

Isotactic polymers are composed of isotactic macromolecules (IUPAC definition). In isotactic macromolecules all the substituents are located on the same side of the macromolecular backbone. An isotactic macromolecule consists of 100\% meso diads. Polypropylene formed by Ziegler–Natta catalysis is an isotactic polymer.

What is crystallization temperature?

The temperature at which crystals will appear in a brine solution of a given density as it cools. In preparing oilfield brines, the crystallization temperature can be used to indicate the maximum saturation (density) achievable for a brine solution at a given temperature.

Is polypropylene semi crystalline or amorphous?

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.

Why does PVC have a higher melting point than polyethylene?

There are greater intermolecular forces between the long chains compared with smaller simple molecules. This means that polymers have a higher melting point than many other organic molecules.

Do polymers have high melting points?

Polymers have higher melting and boiling points than simple molecules. This is because the intermolecular forces between the larger polymer molecules are stronger, so more energy is needed to break them.

Is syndiotactic or isotactic stronger?

Atactic polypropylene is a soft, rubbery polymer, while isotactic polypropylene is strong and hard with excellent resistance to stress, cracking, and chemical reaction. Syndiotactic polypropylene has only recently been made on a large scale. It is somewhat softer than the isotactic polymer, but also tough and clear.

Does isotactic polypropylene change with time at room temperature?

Being a standard semicrystalline polymer, isotactic polypropylene, iPP, has long been known to change with time at room temperature, although not to the extent more recently observed with the syndiotactic form.

Does isotactic polypropylene crystallization produce spherulites?

According, to Varga revision [3] when isotactic polypropylene is crystallized from the melt, is monitored by polarizing optical microscope, birefrengent spherulites are produced, growing radially at a constant rate under isothermal conditions.

What is the difference between isotactic and atactic polymers?

Isotactic PP is the well-known semicrystalline material that we all know, while atactic PP is a rubber-like material. The degree of isotacticity determines the “melting point” of the polymer. Isotactic PP with less than one mistake in any of its 200 insertions melts at 166°C. Sign in to download full-size image

What is the melting point of polypropylene polymer?

The degree of isotacticity determines the “melting point” of the polymer. Isotactic PP with less than one mistake in any of its 200 insertions melts at 166°C. Fig. 55. Microstructures of polypropylene.