Polymer Technology - What Is Polymerization & Degree Of Polymerization?

What Is Polymerization?

The chemical process in which lower molecular weight substances [monomers] are bond together to form high molecular weight substances [polymers] is known as polymerization.

 

Why Polymerization?

Polymers [products of the polymerization process] offer lots of extensive properties as compared to the other natural or synthetic products. These extensive properties of polymers include:

• Higher strength


• Resistance to corrosion


• Easy to fabricate - Can be molded in any shape, size and color


• Improved performance


• Reduced product costs


• Reduced weight [because of improved ratio of strength to stiffness]


• Most of them are good electrical insulators [such as plastics]; However some are good electrical conductors too [carbon black mixed polymers].

 

Degree Of Polymerization:

Degree of polymerization refers to the number of monomers in polymer molecules. This degree of polymerization is directly related to the polymer properties, such as melting point, mechanical strength, etc.

For homopolymers , degree of polymerization can be calculated as:

 

 [latex size=0 color=000000 background=ffffff]\displaystyle X_{n} = \frac{M_{n}}{M_{o}} [/latex]

Where,

           [latex size=0 color=000000 background=ffffff]\displaystyle X_{n} [/latex]     =  Degree of polymerization

                    [latex size=0 color=000000 background=ffffff]\displaystyle M_{n} [/latex]      =  Total molecular wt. of Polymer

  [latex size=0 color=000000 background=ffffff]\displaystyle M_{o} [/latex]        =  Molecular wt. of Polymer unit

 

Mechanisms Of Polymerization:

Polymerization processes or mechanisms of polymerization can be divided into two groups:

• Condensation polymerization [or step growth polymerization]


• Addition polymerization [or Chain growth Polymerization]

 

Types Of Polymerization

Polymerization process requires quantity of monomers along with the initiator or catalyst to start the reaction.  Polymerization processes can be classified in terms of the reaction mediums; i.e.

• Bulk polymerization


• Solution polymerization


• Suspension polymerization


• Slurry polymerization

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Classification Of Materials-What Are Different Types Of Materials?

[caption id="attachment_268" align="alignright" width="320" caption="Different types of materials"][/caption]

There are hundreds and thousands of different types of materials, present in this world. Some are naturally occurred materials [such as wood, water, clay, etc.] and some are men made materials-extracted from the naturally occurred materials by manipulating properties of them. It is impossible to study each and every material separately under the tree of material science, so these materials are divided into several categories, on the basis of the following factors:

• Chemical composition of materials,


• Mode of occurrence of materials naturally


• Ways of extraction of materials before usage [refining, manufacturing, etc.]


• Structure of materials [atomic or crystalline]


• Use of material [industrial and technical]

Most general classification of materials leads following different types of materials groups

Metals

This category contains all metals, whether they are ferrous, non-ferrous or alloys. Metallic materials are usually combination of several metallic elements. They have large number of free electrons; and these free electrons make metals good conductor of electricity and heat. Metals are generally defined as:

“All those substances which can readily give-up electrons to form metallic bonds are considered as metals”.

Some of the specific properties of metals are plasticity, strength, hardness, high luster, good conductor of heat and electricity, stiffness, malleability, magnetic properties, etc. These metallic materials are further classified into three different categories according to their end usage.

• Pure Metals: Extraction of pure metal is not an easy task, these are usually obtained by refining the ores by very expensive specialized extraction techniques. Some of the important pure metals are copper, aluminum etc.

• Ferrous Metals : Iron or ferrous is the main constituent of these ferrous metals. Ferrous metals are extremely important for engineering processes.

• Alloys : when two or metals are blended together [or at least one being metal], they form alloys. Most common example of alloy is stainless steel, which is the formed by the blend of chromium, nickel and low carbon steel.

Polymers:

Polymer materials consist of rubber and plastic constituents and possess very large molecular structures. Many of polymeric compounds falls in the organic materials categories, which are composed of carbon and hydrogen along with other non-organic materials. Polymers are extremely flexible in nature and possess low densities.

Ceramics:

Ceramics are intermediate compounds fall between the categories of metallic and non-metallic materials. Most frequently, these are oxides, carbides and nitrides. Ceramic materials are resistant to harsh environments such as high temperatures, due to which these are used as heat and electric insulators.

Composites:

Composites are the materials, which consist of more than one type of material to display a combination of best properties or characteristics of respective materials. A very familiar example is fiber glass, in which a polymeric material is embedded with glass fibers. Fiberglass acquires flexibility from the polymer and strength from the glass material.

Semi-Conductors:

As it is clear from their name, semi-conductors are intermediate between electrical insulators and conductors. Their electrical characteristics are extremely sensitive towards the presence of impurities, even in small percentages. Semi-conductors have totally revolutionized the electronics and telecom industry with the invention of integrated circuits.

Bio Materials:

Bio-materials are generally used in components related to human body implants in order to replace the diseased or malfunctioning organs. The basic criteria while selecting material for bio-materials are they must be compatible with human body [i-e: human body must accept them as their part], These materials must not produce toxins while in the human body. The materials which can be used as bio-materials now these days are ceramics, polymers, metals and semiconductors

Advanced Materials:

Advanced materials are utilized in high-tech [or high technology] applications. High technological processes refers to those processes which functions on relatively sophisticated and intricate principles such as fiber optics, computer systems, electronic equipment [LCDs, CD players, VCRs, etc.], military operations, space ships, air crafts, etc. These materials are very expensive and may be off all types [ceramics, polymers, metals, etc.].

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What is material science?

[caption id="attachment_262" align="alignright" width="320" caption="Structure Of Material"][/caption]

Material science and engineering plays most important and vital role in this modern age of technology. It is basically the integration of natural sciences [physics, chemistry and biology] along with technical approaches. It helps in facing challenges by integrating education and research with versatility, breadth and perspective. So, Materials engineering covers detailed study of all materials, by investigating the relationship between basic structures and the properties of materials.

More elaborately, materials engineering revolves around the study of following factors:

• Structures of Materials

The basic structure of materials refers to the arrangement of internal components of materials. The structures are divided into four categories – subatomic, atomic, microscopic and macroscopic.

• Properties Of Materials

 Properties of materials describe the response of materials on exposition to some external factors, such as mechanical, electrical, etc.  Material properties depend upon the composition of materials as well as upon the microscopic structure of the material. Properties of materials have already been discussed here: Properties of materials

• Molecular Or Atomic Motion

 I.e. Study of interaction or motion between the atoms or molecules within the material.

• Manufacturing Processes:

 Generally, the materials are considered as of two types, naturally occurred materials and the men made materials. Manufacturing processes refers to the processes which are used to manufacture the materials by manipulating the properties of materials. These processes vary from one material type to another, as well depends upon the operating conditions of the process.

• Mechanisms Of Degradation Of Materials:

Degradation of materials is the most important factor covered under materials engineering education. Degradation simply means the failure of a material. In order to prevent the failure of materials, it is necessary to study about the mechanisms of degradation of materials. Some of the common materials degradation factors are corrosion, abrasion, tribology, etc.

Materials sciences and engineering is a broad discipline of engineering and works with the collaboration of other disciplines of engineering [such as electrical, mechanical, chemical, biomedical, etc.] for better performance and reliability of the product. So, the basic goal of a materials engineer is not only study, design and modify the materials for the process design, but also to apply their experience and knowledge towards product design and optimization.

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Paper Recycling Process-How To Recycle Paper?

[caption id="attachment_240" align="alignright" width="320" caption="how to make recycled paper"][/caption]

Paper is one of the most important recyclable materials. What is paper recycling, and what is the importance of paper recycling has already been discussed here…” recycled paper”.

The whole paper recycling process can be divided into two basic stages. First one is pre-processing stage [involves collection, sorting and the transportation of the waste paper], while the other one is the processing stage [processing of junk paper to the final products].

Pre-processing stage

The pre-processing stage of paper recycling involves following steps:

• Collection & Transportation:

The paper is first collected and transported to the respective locations.

• Sorting:

The collected paper is then sorted out on the basis of types or grades of paper.

• Storage:

The paper is then stored in the warehouses for further processing.

Processing Stage:

The processing stages are the main stages involved in the recycling of used paper to the manufacturing of newer products. This processing stage involves:

• Pulping:

The stored paper is then moved by the conveyor belt to the “Pulper” – A big unit contains dissolving chemicals and water. Firstly, the paper is chopped into small pieces, then into tiny strands of cellulose because of heating. This mixture of water, chemicals and tiny strands of cellulose is termed as “Pulp”.

• Screening

The pulp from the pulper is then passed through screens of different sizes. The purpose of screening is to remove small contaminants [like glue, plastic, sand, etc] from the pulp.

• Cleaning

The screened pulp is then introduced into large cylinders [cone-shaped], which are set to rotation or spinning [same as sedimentation process], due to which the heavy contaminants such as staples are settled at the bottom of the cylinder, while the lighter contaminants are collected in the center of the cone.

• De-inking:

After cleaning, the pulp undergoes through a pulp laundering process, known as de-inking. Deinking will remove the printing ink and other sticking materials like glue, adhesives, etc. Usually a combination of two deinking processes is used. Washing helps in rinsing the smaller ink particle from pulp with the help of water, while the stickies and larger particles are removed with air bubbles in floating process.

• Refining:

During refining process, pulp is beaten to ensure the separation of large bundles of fibers into individual fibers.

• Bleaching & Color Striping:

The selection of bleaching and color striping process depends upon the type of paper to be made.

If the colored paper is to be produced, the, the color stripping process is used. The stripping chemicals help in removing the dyes from the paper.

Bleaching is used in case of white paper production. Paper is bleached with oxygen, chlorine dioxide or hydrogen peroxide.

For brown paper production, pulp is neither stripped, nor bleached.

• Paper Making

Finally, the clean pulp is ready to be processed as paper in the paper machine. Paper machine itself consists seven different sections, which are flow box, wire, presser, drier, size press, calendaring section and reeling up section.

The pulp can be used alone, or can be blended with newer material [virgin fiber] to add strength and smoothness to the paper. Rest of the recycled paper making process is same as that of the simple paper making process, which can be read here…”Paper Manufacturing”.

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Recycling Paper – What is Paper Recycling & Importance Of Recycled Paper

[caption id="attachment_224" align="alignright" width="181" caption="recycle paper"][/caption]

Recycling is the process of producing new products or materials by reprocessing used materials. There are number of materials, which can be recycled to some other useful materials. Some of them are paper, plastic, cardboard, glass, metal [such as steel, aluminum etc]. More about Recycling can be studied here… “What is recycling”.

Paper is made from cellulose – A plant fiber which is derived from wood. This cellulose is converted to pulp first then this pulp is used for the manufacturing of paper. More about paper and paper manufacturing has been discussed in detail here… “Paper manufacturing”.

About one-third of the total solid waste generated around the globe is paper waste. If the world is able to recycle only 50% of the paper then millions of trees can be saved globally. Recycling paper not only saves the energy consumption, but it also helps in reducing the air pollution [caused by the burning of paper]. The complete paper recycling procedure is discussed here…”how to recycle paper”.

What Is Paper Recycling:

Paper is recycled by converting waste paper [thrown by the consumers after use] and scrap paper [wastage in industrial pre-production level] into new usable products. Certain categories of paper, which can be recycled, are:

• Mill broke – Scrape from the paper manufacturing processes such as trimmed papers, paper pulp, etc


• Pre-Consumer Waste - Material discarded before consumer usage.


• Post-Consumer Waste – Discarded material after consumer usage, such as newspaper, office paper, notebooks, etc

What Can Be Made From The Paper Recycling:

Usually the recycled paper made from the paper recycling is of low grade then that of the original material. E.g. the fine office paper sheets can be recycled to make the newspaper, etc.  Almost 80% of the recovered paper is recycled back to form the paper or other paper related products. Rest of the 20% recycled paper can be used for the production of other products, such as wall insulations, ceilings, fuel, roofing, paint filter, animal bedding, etc.

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Recyclable materials – What Can Be Recycled

[caption id="attachment_83" align="alignright" width="300" caption="recyclable materials"][/caption]

Recycling and the benefits of recycling have already been discussed in the previous post. Have a look here: What is recycling.

Materials Which Can Be Recycled:

All materials are not considered as good recyclable materials. The biodegradable materials like food items, organic wastes, etc are not considered as the recyclable materials. The materials, which can be picked, cleaned, and reprocessed into new materials are considered as the recyclable materials. The good recyclable materials are:

Municipal Solid Wastes

These municipal solid wastes (MSW) are the post-consumer solid wastes, generated by the domestic units, commercial units, institutions, hospitals, etc. MSWs are not easy to define; however, MSW is considered as the material waste generally (yard waste, papers, glass, metals, etc). Some of the MSW are described under:

o   Paper

Wasted papers are recycled into the new paper products by paper recycling. It is unfortunately a fact that the paper processing requires pulp, which is obtained by cutting down the trees, which is a threat to the environment. Using recycled papers can minimize the new paper requirements, and so are the wood requirements.

o   Glass

Unlike paper recycling, glass recycling needs extra concentration. The glass bottles and the other types of glass (like Pyrex, light bulbs, window glass, auto glass, etc) cannot be recycled together. As glass chemistry is based on its oxide components typically. The most likely recyclable glass is the clean glass.

o   Oil

Oil recycling might be newer for many people. “Oil” refers to variety of combustible liquids, which are not soluble in water and leave greasy stain. The used or contaminated oil (not consumed) can be considered as the recyclable material. Direct combustion of used oil as a burner fuel should always be condemned, because it not only destroys this valuable source, but also cause environmental pollution.

o   Plastic

Plastic recycling has turned a new shape today. There are lots of grades of plastics. And all the grades or types of plastics cannot be recycled together. A very small quantity of the wrong grade of the plastic can ruin the whole processing batch. It is generally not easy to separate different grades of the plastics. That’s why, there are several cryptic markers used in the plastic industries to indicate the type of the plastics.

o   ferrous metals

Recycling of the ferrous scrap is the principle recycling activity worldwide. The ferrous metals refer to the substances made up of iron or steel. Recycling of these ferrous metals gives number of environmental benefits as well including reduction in air pollution, water usage, landfill requirements, etc compared to the use of virgin materials.

o   Non ferrous metals

Non ferrous metals are any metal other than iron or iron alloys. Highly recycled non ferrous metals are copper, aluminum, lead and zinc.

o   Rubber

Rubber recycling is commonly known by the name of “tire recycling”. Used and damaged tires, which cannot longer be used on the roads, are one of the largest sources of the hazardous wastes. That’s why the tires are one the most recyclable materials. Rubber is a very resilient material, and can easily be reused in other products.

Waste Water Recycling

Waste water recycling refers to the process of removing suspended solids, impurities, Ph balancing, color treatments etc. There are various ways, in which waste water can be recycled. The selection of the treatment process depends upon the end use of the treated water. If the water is to be treated for the textile industrial usage, then there might be some of the treatment techniques involved like the sedimentation, filtration, color treatments etc. But, if water is being treated for human consumption, then number of additional processes like ultra-filtration, reverse osmosis, etc should be carried out. However, treated waste water is generally not used for the drinking purposes.

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Recyclable materials – What Can Be Recycled

Recycling and the benefits of recycling have already been discussed in the previous post. Have a look here: What is recycling. 

Recyclable Materials

What Materials Can Be Recycled:

All materials are not considered as good recyclable materials. The biodegradable materials like food items, organic wastes, etc are not considered as the recyclable materials. The materials, which can be picked, cleaned, and reprocessed into new materials, are considered as the recyclable materials. The good recyclable materials are:

   

   

Municipal Solid Wastes 

These municipal solid wastes (MSW) are the post-consumer solid wastes, generated by the domestic units, commercial units, institutions, hospitals, etc. MSWs are not easy to define; however, MSW is considered as the material waste generally (yard waste, papers, glass, metals, etc). Some of the MSW are described under:

o   Paper

Wasted papers are recycled into the new paper products by paper recycling. It is unfortunately a fact that the paper processing requires pulp, which is obtained by cutting down the trees, which is a threat to the environment. Using recycled papers can minimize the new paper requirements, and so are the wood requirements.

o   Glass

Unlike paper recycling, glass recycling needs extra concentration. The glass bottles and the other types of glass (like Pyrex, light bulbs, window glass, auto glass, etc) cannot be recycled together. As glass chemistry is based on its oxide components typically. The most likely recyclable glass is the clean glass.

o   Oil

Oil recycling might be newer for many people. “Oil” refers to variety of combustible liquids, which are not soluble in water and leave greasy stain. The used or contaminated oil (not consumed) can be considered as the recyclable material. Direct combustion of used oil as a burner fuel should always be condemned, because it not only destroys this valuable source, but also cause environmental pollution.

o   Plastic

Plastic recycling has turned a new shape today. There are lots of grades of plastics. And all the grades or types of plastics cannot be recycled together. A very small quantity of the wrong grade of the plastic can ruin the whole processing batch. It is generally not easy to separate different grades of the plastics. That’s why, there are several cryptic markers used in the plastic industries to indicate the type of the plastics.

o   ferrous metals

Recycling of the ferrous scrap is the principle recycling activity worldwide. The ferrous metals refer to the substances made up of iron or steel. Recycling of these ferrous metals gives number of environmental benefits as well including reduction in air pollution, water usage, landfill requirements, etc compared to the use of virgin materials.

o   Non ferrous metals

Non ferrous metals are any metal other than iron or iron alloys. Highly recycled non ferrous metals are copper, aluminum, lead and zinc.

o   Rubber

Rubber recycling is commonly known by the name of “tire recycling”. Used and damaged tires, which cannot longer be used on the roads, are one of the largest sources of the hazardous wastes. That’s why the tires are one the most recyclable materials. Rubber is a very resilient material, and can easily be reused in other products.

·    Waste Water Recycling

Waste water recycling refers to the process of removing suspended solids, impurities, Ph balancing, color treatments etc. There are various ways, in which waste water can be recycled. The selection of the treatment process depends upon the end use of the treated water. If the water is to be treated for the textile industrial usage, then there might be some of the treatment techniques involved like the sedimentation, filtration, color treatments etc. But, if water is being treated for human consumption, then number of additional processes like ultra-filtration, reverse osmosis, etc should be carried out. However, treated waste water is generally not used for the drinking purposes. 

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