What describes a characteristic of branched polymers?
Answer: The one that describes a branched polymer is that they have only one start point and many end points.
What are branched chain polymers?
Branched polymers are defined as having secondary polymer chains linked to a primary backbone, resulting in a variety of polymer architectures such as star, H-shaped, pom-pom, and comb-shaped polymers.
Which of the following is a branched polymer?
Answer. ▶Low density polymer are branched polymer.
How does branching affect polymer properties?
Branching also affects chain entanglement, the ability of chains to slide past one another, in turn affecting the bulk physical properties. Long chain branches may increase polymer strength, toughness, and the glass transition temperature (Tg) due to an increase in the number of entanglements per chain.
How does branching affect crystallinity?
Both the degree of branching as well as the length of the branches affects the density which can vary considerably. Typically, the higher the density of the polymer the higher the degree of crystallinity and the stiffer, harder, and stronger the polymer. However, these polymers are rather brittle.
What is the difference between a linear and branched polymer?
Polymers can be grouped as linear polymers and branched polymers depending on their structures. The main difference between branched polymer and linear polymer is that branched polymers have a branched structure whereas linear polymers have a linear structure.
Which of the following is linear polymer?
The examples of linear polymer are polythene, poly – vinyl chloride etc.
Why does cross linking improve the strength of polymers?
7.24 Explain how cross linking improves the strength of polymers. o Crossed linked polymers contain additional bonds between the molecules that provide resistance to flow. All of the extra links or bonds must be broken before the molecules can move relative to each other. Some polymers are conductive naturally.
What happens to the properties of a linear polymer when heated?
The effect of temperature change on polymers When heated, the polymers will first become flexible before melting. This is due to their structure. Eventually, if the polymer is heated enough, the melting temperature Tm will be reached (the plastic becomes a viscous fluid). This process is reversible for thermoplastics.
What affects the 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 factors affect polymer properties?
Numerous factors affect various mechanical properties of polymers, in- cluding molecular weight, processing, extent and distribution of crystallinity, composition of polymer, and use temperature.
How does temperature affect polymers?
Higher temperatures lead to lower young modulus of the material. Weak points of every polymeric material are the secondary bonds between molecules of your polymer. With increasing temperatures, the molecules have more kinetic energy, thus the weak secondary bonds have less and less effect.
What temperature does plastic soften?
100 degrees Celsius
Why do polymers shrink when heated?
Once the plastic is heated above its glass transition temperature, the polymer chains are no longer locked in that high strain orientation. They relax to a low energy orientation- curled and bending in a way that shrinks the bulk material.
What polymers melt when they are heated?
Thermosoftening and thermosetting plastics Thermosoftening plastics melt when they are heated. Most plastics that we come across in everyday life are thermosoftening plastics. This means that they can be recycled , which involves melting them before making a new product.
Do polymers expand when heated?
The extent to which the polymer expands or contracts when heated or cooled. They contain strong covalent bonds along the polymer chain and much weaker dispersive forces between the polymer chains. As a result, polymers can expand by differing amounts in different directions.)
What happens when thermosets are heated?
Thermoset polymers do not soften when heated because the molecules are cross-linked together and remain rigid. The chemical bonding formed within a polymer, and the shape of the resulting polymer, affect its properties.
How can you change the properties of polymers?
Overall, the main ways to change and tune the properties of a polymer include changing the length of the polymer chains, creating branched chains from linear polymer chains, crosslinking the polymer chains and adding plasticizers into the polymer.
What are the main properties of polymers?
Some of the useful properties of various engineering polymers are high strength or modulus to weight ratios (light weight but comparatively stiff and strong), toughness, resilience, resistance to corrosion, lack of conductivity (heat and electrical), color, transparency, processing, and low cost.
Why are polymers so strong?
The bigger the molecule, the more molecule there is to exert an intermolecular force. Even when only weak Van der Waals forces are at play, they can be very strong in binding different polymer chains together. This is another reason why polymers can be very strong as materials.
How do you strengthen polymers?
Adding filler materials such as fibers, platelets, and particles is a commonly employed technique for strengthening polymer materials. Fillers such as clay, silica, and carbon network materials have been extensively researched and used in polymer composites in part due to their effect on mechanical properties.
Which polymer is the strongest?
Polybenzoxazole (PBO) is a high-performance, heat-resistant fiber with a benzene-fused oxazole ring structure. The fiber is almost twice as strong as aramid fibers (Kevlar, Nomex) and about 10 times stronger than steel making it the strongest manmade organic fiber.
What is polymer crosslinking?
Put simply, crosslinking involves a chemical reaction between polymer chains to link them together. Crosslinking can influence several end properties across most applications, including: Coating chemical resistance. Polymer flow properties – block and print resistance. Coating toughness.
How do you increase yield strength in steel?
The finer the carbides and grain size, the higher the yield strength. The tempering determines the size of the carbide particles. Increasing the tempering temperature for a given time will accelerate diffusion, but lead to the carbide and grain coarser and the material slightly softer.
How do you increase ductility of steel?
During a recrystallization anneal, new grains form in a cold-worked metal. These new grains have a greatly reduced number of dislocations compared to the cold-worked metal. This change returns the metal to its pre-cold-worked state, with lower strength and increased ductility.
How can steel properties be improved?
The strength of steel can be increased by the addition of alloys such as manganese, niobium and vanadium. However, these alloy additions can also adversely affect other properties, such as ductility, toughness and weldability . The more steel is rolled, the stronger it becomes.
Does annealing make metal stronger?
Annealing makes metals more formable. When metal is stronger and more ductile, it gives manufacturers more leeway in the fabrication process. There is less risk of material fracturing from bending or pressing. Annealing can also improve a metal’s ability to be machined and improve the lifespans of tools.
How do you make metal stronger?
To make steel harder, it must be heated to very high temperatures. The final result of exactly how hard the steel becomes depends on the amount of carbon present in the metal. Only steel that is high in carbon can be hardened and tempered.
How do you strengthen metal?
There are four ways to increase a metal’s strength:
- Cold working.
- Solid-solution hardening.
- Transformation hardening.
- Precipitation hardening.
Does heating metal make it stronger?
This simple act, if heated to an exact temperature range, can create a more pure, hard metal. It’s often used to create steel that is stronger than annealing the metal, but also creates a less ductile product. So, heat can indeed make metal weaker. However, there are many processes where metal is strengthened by heat.