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. Number average DP and weight average DP are the two main types used for measuring the DP.
How does the degree of polymerisation affect the mechanical properties of the material?
Increasing the degree of polymerisation. The strength properties of polymers
increase with the length of the chains
, which is controlled by the degree of polymerisation. … The strength increases with the chain length because they become more tangled and, therefore, a higher stress is needed to stretch and untangle them.
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
.
What affects rate of polymerization?
Rates of polymerization may be increasing either by
raising the temperature
or by increasing the concentration or activity of the catalyst.
Why are polymers with a higher degree of polymerization DP stronger and more viscous?
Due
to increased entanglement of chains with increased molecular weight
, the polymer gets higher viscosity in molten state, which makes the processing of polymer difficult.
Why is degree of polymerization important?
Correlation with physical properties
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?
By using
postassembly ligand photo-cross-linking
, we established a method to arrest NR polymer growth after a particular self-assembly time, and in this manner, using kinetics of step-growth polymerization, we achieved control over the average degree of polymerization of plasmonic polymers.
What are mechanical properties?
Mechanical properties are
physical properties that a material exhibits upon the application of forces
. Examples of mechanical properties are the modulus of elasticity, tensile strength, elongation, hardness and fatigue limit.
How does the degree of crystallinity affect the properties of a thermoplastic?
2009; 517(1-2):51-60.. Crystallinity degree in high performance thermoplastics is important, because it has a strong influence on chemical and mechanical properties:
the crystalline phase tends to increase stiffness and tensile strength
, while the amorphous phase is more effective in absorbing impact energy
9
.
How does temperature affect polymers?
The effect of temperature change on polymers
When substances made of small molecules are heated,
they simply melt and form a free-flowing liquid
; however with polymers the process is more complex. When polymers are cooled, they will often become very brittle.
Which polymerization process has the highest reaction rate?
4 Methyl-Methacrylate Bulk Polymerization
The polymerization is highly exothermic and exhibits a strong acceleration in polymerization rate due to gel-effect (e.g., the termination rate constant decreases with conversion).
How do you calculate polymerization rate?
- Rp=−d[M]dt.
- Ri=d[R·]dt.
- Ri=d[R·]dt=2kd[I]
- Rprop=−d[M]dt =kp[M][M·]
- Rtc=−d[M·]dt =2ktc[M·][M·]
- Rtd=−d[M·]dt=2ktd[M·][M·]
- Rt=−d[M·]dt=2ktd[M·]2+2ktc[M·]2=2kt[M·]2.
How do you calculate polymerization?
Divide the molecular weight of the polymer by the molecular weight of the monomer unit
to calculate the degree of polymerization. If the molecular mass of tetrafluoroethylene is 120,000, its degree of polymerization is 120,000 / 100 = 1,200.
Does viscosity increase with temperature?
The viscosity of liquids decreases rapidly with an increase in temperature, and
the viscosity of gases increases with an increase in temperature
. Thus, upon heating, liquids flow more easily, whereas gases flow more sluggishly. … Kinematic viscosity is the absolute viscosity of a fluid divided by its mass density.
What are the factors that control crystallinity of polymers?
The size and structure of the crystals and the degree of crystallinity depend on the
type and structure of the polymer
, and on the growth conditions. Narrow molecular weight, linear polymer chains, and high molecular weight increase the crystallinity.
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.
