How does increasing the molecular weight of a semicrystalline polymer affect its tensile strength?

How does increasing the molecular weight of a semicrystalline polymer affect its tensile strength?

(a) The tensile strength of a semicrystalline polymer increases with increasing molecular weight. This effect is explained by increased chain entanglements at higher molecular weights.

How does deformation by drawing of a semicrystalline polymer affect its tensile strength decreases increases?

Deformation by drawing increases the tensile strength of a semicrystalline polymer. This effect is due to the highly oriented chain structure that is produced by drawing, which gives rise to higher interchain secondary bonding forces.

How does molecular weight affect tensile strength?

In general, as molecular weight increase the strength, toughness and chemical stress crack resistance increase. A High molecular weight increases the chemical resistance – to a point. It takes more damage to the main chains of the molecules before it will affect the strength of the material.

Does molecular weight affect yield strength?

In most cases, a narrow molecular weight distribution will yield better mechanical properties than a broad distribution because the low molecular weight portion will act as a plasticizer and soften the polymeric material, whereas an exceedingly high molecular weight portion will make processing of the polymer resin …

Why does crystallinity improve the strength of a polymer?

Crystallinity: The crystallinity of the polymer increases strength, because in the crystalline phase, the intermolecular bonding is more significant. Hence, the polymer deformation can result in the higher strength leading to oriented chains.

How is crystallinity of polymers measured?

Polymer crystallinity can be determined with DSC by quantifying the heat associated with melting (fusion) of the polymer. This heat is reported as Percent Crystallinity by normalizing the observed heat of fusion to that of a 100 % crystalline sample of the same polymer.

How does branching affect boiling point?

Branching decreases the boiling point So the increase of surface area increases the ability of individual molecules to attract each other.

Does branching increase stability?

Chemists have known for almost 80 years that branched alkanes are more stable than their unbranched isomers. According to this model, branching means that the electronic structure is simply more compact and this decreases molecular surface area per atom and so leads to a lowering of energy and increases in stability. .

Does boiling point depends on molecular weight?

In general, larger molecules have higher boiling points than smaller molecules of the same kind, indicating that dispersion forces increase with mass, number of electrons, number of atoms or some combination thereof.

What effect does branching of an alkene chain has on its boiling point?

Solution : As the branching increases , the surface area of an alkene approaches that of a sphere. Since, a sphere has minimum surface area, therefore, van der Waals forces of attraction are minimum and hence the boiling point of the alkane decreases with branching.

Why do straight chains have higher boiling points?

A straight chain alkane will have a boiling point higher than a branched chain alkane because of the greater surface area in contact with other molecules. Branching makes molecules more compact thus reduces the surface area.

Why do Cycloalkanes have higher boiling points?

Cycloalkanes are similar to alkanes in their general physical properties, but they have higher boiling points, melting points, and densities than alkanes. This is due to stronger London forces because the ring shape allows for a larger area of contact.

Why are alkanes unreactive?

Alkanes are saturated hydrocarbons. This means that their carbon atoms are joined to each other by single bonds. This makes them relatively unreactive, apart from their reaction with oxygen in the air – which we call burning or combustion.

Are Haloalkanes acidic or basic?

Terminal alkynes and acetylene are mildly acidic. The haloalkanes or alkyl halides are a group of chemical compounds, derived from alkanes containing one or more halogens. They are a subset of the general class of halocarbons although the distinction is not often made.

Do alkanes react?

Alkanes (the most basic of all organic compounds) undergo very few reactions. The two reactions of more importaces is combustion and halogenation, (i.e., substitution of a single hydrogen on the alkane for a single halogen) to form a haloalkane.

Are alkenes acidic or basic?

Now the reason why alkynes are more acidic than alkenes, which are in turn more acidic than alkanes, is that sp carbon atoms are more electronegative than sp2 carbon atoms, which are in turn more electronegative than sp3 carbon atoms.

Are alkynes acidic or basic?

These types of alkynes are weakly acidic. Exposure to a strong base, such as sodium amide, produces an acid‐base reaction. The acidity of a terminal alkyne is due to the high level of s character in the sp hybrid orbital, which bonds with the s orbital of the hydrogen atom to form a single covalent bond.

Why are alkanes called paraffins?

Paraffin is a truncation of Latin ‘parum affinum’ meaning ‘less affinity’ i.e. ‘less reactivity’. Alkanes have only single bonds which are sigma covalent. Hence, alkanes are called paraffins because they have lesser affinity towards general reagents. In other words they are inert, not readily active.

Which alkene is most acidic?

ethyne

Is an alkene or alkyne more acidic?

Due to presence of more s-character, the alkynes are more electronegative. Thus in Ethyne hydrogen atoms can be liberated as protons more easily.

Which is more acidic alcohol or Ethyne?

(b) The negative charge on Oxygen is more stabilised than that on Carbon, This is because,O is an electronegative element so it has better hold of negative charge,thus alcohols are more acidic.

Which one is correct order of acidity?

CH≡CH>CH3−C≡CH>CH2=CH2>CH3−CH3.

Which of the following is correct order of acidity Hcooh CH3COOH?

Correct option: b ClCH2COOH > HCOOH > CH3COOH > C2H5COOHExplanation:Recall that presence of electron withdrawing group increases while presence of electron-releasing group decreases the acidity of carboxylic acids.