Why synthesize a polymer with a high degree of crystallinity

Begin typing your search term above and press enter to search. Press ESC to cancel. Skip to content Home Engineering What is crystallinity of polymers? Ben Davis March 11, What is crystallinity of polymers? What does crystallinity mean? Why do polymers crystallize? What affects crystallinity in polymers? How does branching affect crystallinity?

What is meant by branching? What causes branching in polymers? Does branching increase viscosity? What increases viscosity? What are the factors that affect viscosity? How does branching affect polymer properties? Which one of the following is branched polymer? Which of the following is linear polymer? Which of the following is an example of condensation polymer?

Is PVC a condensation polymer? Is nylon a condensation polymer? Is nylon 6 a condensation polymer? Is protein a natural polymer? Why is it called Nylon 6? Is nylon 6 a polyester? What are 4 uses for nylon? What are the uses of nylon 6? Why is nylon so strong? How is nylon harmful? Is nylon stronger than steel? Is nylon The strongest Fibre? The number and degree of long chain branching also affects the melt flow properties such as shear thinning behavior and viscoelastic response.

Polymer Properties Database. Branched Polymers The properties of polymers are strongly affected by their molecular weight and molecular weight distribution as well as by their chain architecture, particularly by the amount of branching. References F. Bueche, Journal of Chemical Physics 40, Summary Branched Polymers The number, size and type of side chains has a significant affect on the thermo-physical and mechanical properties of a polymer.

Short Branches An increase in the average branch length results in a larger free volume, reduced packing density, and thus, in a lower glass transition and melting temperature, but increased toughness, and flexibility.

Long Branches Polymers with long side chains have an intrinsic tendency to side-chain crystallization which leads to an increase in the glass transition temperature and melting point. Read More. Theromophysical Data Key data on over two hundred and fifty polymers. Polymers Index. Typical Performance Properties of commercial commodity and engineering polymers. Plastics Index. Physics of Polymers Physical and mechanical properties of polymers Phys. This creates amorphous regions in an otherwise crystalline polymer.

Most crystalline polymers have amorphous regions, which means crystalline polymers are never completely crystalline. Crystallinity can range from 0 percent entirely amorphous to percent entirely crystalline , but most polymers fall somewhere between those extremes. Chain flexibility — both flexing along the entire chain and flexing in bonds between atoms — plays a big role in polymer crystal formation.

As chains flex and bend against each other, various attractive and repulsive forces affect how polymer chains arrange themselves, either more orderly or less orderly. Degree of crystallinity is directly related to whether a polymer melts like a typical solid or whether it transitions between glassy and rubbery states. Highly crystalline polymers have a more traditional melting point, so when they are heated, they reach a certain temperature at which the orderly arrangement of their long-chain structure transitions to a random and disorganized arrangement.

This value is usually a specific number, designated as the melting point, or T m. Instead, they reach a range of temperatures over which the material becomes less glassy and more rubber-like or vice versa. The glass transition temperature of a specific polymer may be listed as a single temperature, but this number is a representative value representing a range of temperatures.

To explain glass transition temperature in terms of molecular motion, we would say that, at temperatures below T g , the amorphous polymer chains cannot rotate or move in space the cooked spaghetti is frozen and cannot move. This produces the glassy state, which is hard, rigid, and brittle. When the temperature rises above T g , the entangled chains can move small portions of the spaghetti noodles can move around. This produces a rubbery state, when an amorphous polymer is soft and flexible.

Although percent and 0 percent crystallinity are rare, some polymers fall close to either extreme. Those that tend toward high crystallinity are rigid, have high melting points, and are less affected by solvent penetration. Those that tend toward high amorphousness are softer, have glass transition temperatures , and are penetrated more by solvents than are their crystalline counterparts.

Here are some examples, along with their key properties:. To understand why, it helps to realize that polymers can have multiple configurations. A polymer has a main backbone with small clusters of atoms, called pendant groups, coming off of the chain. If all of the pendant groups are on the same side of the chain, the polymer is isotactic. If the pendant groups come on alternating sides of the chain, the polymer is said to be syndiotactic.

If the pendant groups are on both sides, but in no particular order, the polymer is atactic.