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Why does excessive cross-linking increase brittleness of a polymer?
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+ Polymer science
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Aijaz Haider
Why does excessive cross-linking increase brittleness of a polymer?
It is not true that more cross~linking would increase the brittleness of the polymer.
Rubber can not be used in anywhere befor cross-linking by crossling agent such as sulfur and sulfur resin. The more cross-linked bond formed, the better performance the rubber could have. And the brittleness of the rubber may be the same. The reason is that the double bond in the rubber could make the motion of sedgmental easier and could weak the brittleness caused by crossling.
It is not true that more cross~linking would increase the brittleness of the polymer.
Rubber can not be used in anywhere befor cross-linking by crossling agent such as sulfur and sulfur resin. The more cross-linked bond formed, the better performance the rubber could have. And the brittleness of the rubber may be the same. The reason is that the double bond in the rubber could make the motion of sedgmental easier and could weak the brittleness caused by crossling.
A “living polymer” is one that still has a cationic, anionic, or free radical end that can continue to react with monomer molecules. If a polymer chain undergoes a termination step, that extinguishes the reactive end.
A “living polymer” is one that still has a cationic, anionic, or free radical end that can continue to react with monomer molecules. If a polymer chain undergoes a termination step, that extinguishes the reactive end.
Cross-linking is way of interconnecting two polymer chains with or without a intermediate chemical. In Rubbers, Sulphur is used as Crosslinking chemical. Crosslinking is nothing but forming a chemical bond between two atoms or molecules. Sulphur has free electrons which can be used for making chemical bond. Similarly polymer which has free electrons(double bond) can be used for making chemical bond. In case Rubber and sulphur, two rubber molecules are crosslinked with help of sulphur. This process is known in rubber industry as Curing.
Cross-linking is way of interconnecting two polymer chains with or without a intermediate chemical. In Rubbers, Sulphur is used as Crosslinking chemical. Crosslinking is nothing but forming a chemical bond between two atoms or molecules. Sulphur has free electrons which can be used for making chemical bond. Similarly polymer which has free electrons(double bond) can be used for making chemical bond. In case Rubber and sulphur, two rubber molecules are crosslinked with help of sulphur. This process is known in rubber industry as Curing.
In short, a piece of polymer can be viewed as millions and millions of individual polymer chains all tangled together.
In the state where they are not cross-linked you can think of the polymer chains having a certain ability or freedom to move or to straighten out if acted upon by an outside force.
Think now of what happens as you pull on a plastic staw. At some point in the straw the plastic necks down and becomes elongated. In essence the energy of the force is dissapated with the ability of the polymer chains to move or straighten out.
In the scenario where you introduce cross-linking, you inhibit this freedom. At a low level of cross-linking this might not have a significant effect BUT once the level gets higher and higher, the ability to straighten out or move becomes severly inhibited - the energy of the force progressively ends up snapping more and more of the chains where they cant move.
A decreased ability of the polymer chains to move and absorb the energy of impact is reflected in a drop in the impact strength of the material and a corresponding rise in brittleness.
In short, a piece of polymer can be viewed as millions and millions of individual polymer chains all tangled together.
In the state where they are not cross-linked you can think of the polymer chains having a certain ability or freedom to move or to straighten out if acted upon by an outside force.
Think now of what happens as you pull on a plastic staw. At some point in the straw the plastic necks down and becomes elongated. In essence the energy of the force is dissapated with the ability of the polymer chains to move or straighten out.
In the scenario where you introduce cross-linking, you inhibit this freedom. At a low level of cross-linking this might not have a significant effect BUT once the level gets higher and higher, the ability to straighten out or move becomes severly inhibited - the energy of the force progressively ends up snapping more and more of the chains where they cant move.
A decreased ability of the polymer chains to move and absorb the energy of impact is reflected in a drop in the impact strength of the material and a corresponding rise in brittleness.
Living polymers are those which have a active end means if you introduce the monomer it again start polymerization because of that active end .
Majorly anionic polymerization give this type of living polymers . Cationic also give living polymers bit they are not much stable so they easily converted into stable chain ends.
Living polymers are those which have a active end means if you introduce the monomer it again start polymerization because of that active end .
Majorly anionic polymerization give this type of living polymers . Cationic also give living polymers bit they are not much stable so they easily converted into stable chain ends.
It is not true that more cross~linking would increase the brittleness of the polymer.
Rubber can not be used in anywhere befor cross-linking by crossling agent such as sulfur and sulfur resin. The more cross-linked bond formed, the better performance the rubber could have. And the brittleness of the rubber may be the same. The reason is that the double bond in the rubber could make the motion of sedgmental easier and could weak the brittleness caused by crossling.
It is not true that more cross~linking would increase the brittleness of the polymer.
Rubber can not be used in anywhere befor cross-linking by crossling agent such as sulfur and sulfur resin. The more cross-linked bond formed, the better performance the rubber could have. And the brittleness of the rubber may be the same. The reason is that the double bond in the rubber could make the motion of sedgmental easier and could weak the brittleness caused by crossling.
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Intuitively with more cross linking you have more chance to form a network with more opportunities to break linkages which is observed as brittleness.
Intuitively with more cross linking you have more chance to form a network with more opportunities to break linkages which is observed as brittleness.
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VOTE
A “living polymer” is one that still has a cationic, anionic, or free radical end that can continue to react with monomer molecules. If a polymer chain undergoes a termination step, that extinguishes the reactive end.
A “living polymer” is one that still has a cationic, anionic, or free radical end that can continue to react with monomer molecules. If a polymer chain undergoes a termination step, that extinguishes the reactive end.
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Cross linked polymers are polymers in which monomer units are cross linked together to form a three dimensional network polymers .
These polymers are hard,rigid and brittle because of network structure .
Some important examples are bakelite , melamine formaldehyde etc.
Cross linked polymers are polymers in which monomer units are cross linked together to form a three dimensional network polymers .
These polymers are hard,rigid and brittle because of network structure .
Some important examples are bakelite , melamine formaldehyde etc.
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VOTE
Cross-linking is way of interconnecting two polymer chains with or without a intermediate chemical. In Rubbers, Sulphur is used as Crosslinking chemical. Crosslinking is nothing but forming a chemical bond between two atoms or molecules. Sulphur has free electrons which can be used for making chemical bond. Similarly polymer which has free electrons(double bond) can be used for making chemical bond. In case Rubber and sulphur, two rubber molecules are crosslinked with help of sulphur. This process is known in rubber industry as Curing.
Cross-linking is way of interconnecting two polymer chains with or without a intermediate chemical. In Rubbers, Sulphur is used as Crosslinking chemical. Crosslinking is nothing but forming a chemical bond between two atoms or molecules. Sulphur has free electrons which can be used for making chemical bond. Similarly polymer which has free electrons(double bond) can be used for making chemical bond. In case Rubber and sulphur, two rubber molecules are crosslinked with help of sulphur. This process is known in rubber industry as Curing.
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VOTE
In short, a piece of polymer can be viewed as millions and millions of individual polymer chains all tangled together.
In the state where they are not cross-linked you can think of the polymer chains having a certain ability or freedom to move or to straighten out if acted upon by an outside force.
Think now of what happens as you pull on a plastic staw. At some point in the straw the plastic necks down and becomes elongated. In essence the energy of the force is dissapated with the ability of the polymer chains to move or straighten out.
In the scenario where you introduce cross-linking, you inhibit this freedom. At a low level of cross-linking this might not have a significant effect BUT once the level gets higher and higher, the ability to straighten out or move becomes severly inhibited - the energy of the force progressively ends up snapping more and more of the chains where they cant move.
A decreased ability of the polymer chains to move and absorb the energy of impact is reflected in a drop in the impact strength of the material and a corresponding rise in brittleness.
In short, a piece of polymer can be viewed as millions and millions of individual polymer chains all tangled together.
In the state where they are not cross-linked you can think of the polymer chains having a certain ability or freedom to move or to straighten out if acted upon by an outside force.
Think now of what happens as you pull on a plastic staw. At some point in the straw the plastic necks down and becomes elongated. In essence the energy of the force is dissapated with the ability of the polymer chains to move or straighten out.
In the scenario where you introduce cross-linking, you inhibit this freedom. At a low level of cross-linking this might not have a significant effect BUT once the level gets higher and higher, the ability to straighten out or move becomes severly inhibited - the energy of the force progressively ends up snapping more and more of the chains where they cant move.
A decreased ability of the polymer chains to move and absorb the energy of impact is reflected in a drop in the impact strength of the material and a corresponding rise in brittleness.
More
VOTE
Living polymers are those which have a active end means if you introduce the monomer it again start polymerization because of that active end .
Majorly anionic polymerization give this type of living polymers . Cationic also give living polymers bit they are not much stable so they easily converted into stable chain ends.
Living polymers are those which have a active end means if you introduce the monomer it again start polymerization because of that active end .
Majorly anionic polymerization give this type of living polymers . Cationic also give living polymers bit they are not much stable so they easily converted into stable chain ends.
More
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