In general, increasing degree of polymerization correlates with
higher melting temperature
and higher mechanical strength.
What affects 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 properties are affected by the degree of polymerization explain?
This means that the degree of polymerization indicates how the ratio of the molecular weights increases. o Polymerization and in particular the degree of polymerization has an impact on many of its properties. The affected properties are
tensile strength, impact strength, resistance to cracking, and viscosity
.
How does temperature affect degree of polymerization?
The temperature affects
both the rate of free radical formation and the thermody- namic properties
of the polymerization system. … It is also shown that higher levels of initiator at a particular temperature actually produced larger particles.
How does crystallinity affect melting temperature?
Their
elastic modulus changes
significantly only at high (melting) temperature. It also depends on the degree of crystallinity: higher crystallinity results in a harder and more thermally stable, but also more brittle material, whereas the amorphous regions provide certain elasticity and impact resistance.
Why is degree of polymerization important?
Polymers with identical composition but different molecular weights may exhibit different physical properties. In general, increasing degree of polymerization
correlates with higher melting temperature and higher mechanical strength
.
How is degree of polymerization controlled?
You need to use one of the controlled polymerization techniques such as
ATRP or RAFT
in order to control the chain growth of the each block. So you can control the degree of polymerization. … ATRP or RAFT give you a high degree of control over the polymerization.
How is degree of polymerization measured?
The degree of polymerization (DP or X
n
) is defined as the number of monomer units in the polymer. It is calculated as
the ratio of molecular weight of a polymer and molecular weight of the repeat unit
What is degree of polymerization of cellulose?
The degree of polymerization of cellulose is
calculated from the intrinsic viscosity of solutions prepared by dissolving cellulose in a suitable solvent
, such as CED or cadoxen. … The viscosity of pulp using the capillary viscometer method can be used for conventional pulps with up to 4% lignin.
Does tacticity affect melting point?
The tacticity of a
polymer can have a dramatic effect on its physical properties
. For example, the melting points of isotactic, syndiotactic, and atactic polypropylene are 160-170
o
C, 125-131
o
C, and <0
o
C, respectively. … It is somewhat softer than the isotactic polymer, but also tough and clear.
What increases crystallinity?
Crystallinity is usually induced by cooling a melt or a dilute solution below its melting point. The later can result in the growth of single crystals. …
Narrow molecular weight, linear polymer chains
, and high molecular weight increase the crystallinity.
What is the difference between glass transition temperature and melting temperature?
But the main difference between glass transition temperature and melting temperature is that
glass transition temperature describes the transition of a glass state into a rubbery state
whereas melting temperature describes the transition of a solid phase into a liquid phase.
What is the repeating unit of PVC?
The basic repeat unit of the PVC polymer chain is
[-CH2-CHCI-]
. The units are linked essentially ‘head-to-tail’ (Le. -CH2-CHCI- CH2-CHCI-), with very few head-to-head junctions (see Table 3.3). In commercial PVC polymers the average number of repeat units in the molecular chain (Le.
What does the N mean in polymers?
A repeat unit is sometimes called a mer or mer unit. … In condensation polymers (see examples below), the repeat unit contains fewer atoms than the monomer or monomers from which it is formed. The subscript “n” denotes
the degree of polymerisation
, that is, the number of units linked together.
How does water affect the degree of polymerization?
Water soluble polymers provide
greater water reduction
at very low values of degree of polymerization. At higher values, flocculent interactions can occur. Optimal values of the degree of polymerization vary from one polymer to another.
