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Polymer Science and Engineering

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Manager : Arash Sadeghi
این نوشته مطلبی ثابت است:
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با تشکر مدیر سایت A.S





طبقه بندی: متفرقه،
برچسب ها: مطلب ثابت، update، مهندسان، اساتید، دانش آموزان، دانشجویان،

تاریخ : پنجشنبه 29 آبان 1393 | 01:12 ب.ظ | نویسنده : Arash Sadeghi | نظرات
نشریه علمی دانشجویی انجمن علی مهندسی پلیمر دانشگاه  صنعتی قم













طبقه بندی: نشریه POLY TEQ،

تاریخ : یکشنبه 28 آبان 1396 | 01:54 ب.ظ | نویسنده : زهرا حاجیان | نظرات

POLYMER CONCRETE


Polymer concrete

Polymer concrete is an ordinary concrete produced with OPC ( Ordinary portland cement) wet cured and inseminated with liquid or vaporous chemical compound (Methyl methacrylate monomer) and polymerized by gamma radiation or with chemical initiated implies, i.e by utilizing thermal catalytic method (Adding 3% Benzoyl peroxide) to the monomer as a catalyst. The impregnation is helped by drying the concrete at an extreme temperature by evacuations and absorbing the monomer under limited pressure.


TYPES OF POLYMER CONCRETE:

Polymer concrete can be classified in following three categories:

1. Polymer impregnated concrete (PIC).

2. Polymer cement concrete (PCC).

3. Polymer concrete (PC).


ADVANTAGES OF POLYMER CONCRETE:

1. It has high impact resistance and high compressive strength.

2. Polymer concrete is highly resistant to freezing and thawing.

3. Highly resistant to chemical attack and abrasion.

4. Permeability is lower than other conventional concrete.






طبقه بندی: کامپوزیت، اطلاعات پلیمری، کاربرد مهندسی پلیمر،
برچسب ها: POLYMER CONCRETE، POLYMER، CONCRETE،

تاریخ : سه شنبه 17 مرداد 1396 | 10:57 ق.ظ | نویسنده : Arash Sadeghi | نظرات


What are Eco-Friendly Products?



According to a definition given by the website all-recycling-facts.com, eco-friendly products are “products that do not harm the environment whether in their production, use or disposal”. In other words, these products help preserve the environment by significantly reducing the pollution they could produce. Eco-friendly products can be made from scratch, or from recycled materials. This kind of product is easily recognizable as it is, in most cases, labelled as such.

Some people think that it requires lot of time, effort and money to make a home eco-friendly. The truth is that there are lot of eco-products that you can start using right now which can help you to reduce waste and make this planet a better place to live. Eco-products are also known as environment friendly products or green products as they cause minimal harm to people and the environment.




طبقه بندی: پلاستیک ها،
برچسب ها: harm the environment، environment، polymer، eco-products، Eco-Friendly Products، Eco-Friendly،

تاریخ : شنبه 14 مرداد 1396 | 06:43 ب.ظ | نویسنده : Arash Sadeghi | نظرات


Bio Plastics


These are plastics made from plants. The starch contained within the plant is processed to produce a polymer. It is actually possible to produce most polymers from bio materials, but the bio plastics London Bio Packaging uses most commonly are Ingeo™ PLA (Poly-Lactic Acid) and Mater-Bi®.

Bio-plastics behave in a similar way to conventional plastics and are suitable for most packaging applications. However, unlike finite oil based plastics which take millions of years to form and hundreds of years to degrade, they are annually renewable and suitable for commercial compost (nature’s way of recycling) within 12 weeks where facilities exist. The carbon footprint of Bio-plastic is therefore much lower than traditional petroleum based plastics. For examples, manufacturing Ingeo produces 60 percent less greenhouse gases and uses 50 percent less non-renewable energy than traditional plastics like PET 




طبقه بندی: پلاستیک ها، اطلاعات پلیمری،
برچسب ها: bio، biopolymers، bioplastic،

تاریخ : شنبه 14 مرداد 1396 | 06:38 ب.ظ | نویسنده : Arash Sadeghi | نظرات
♨️انجمن علمی مهندسی پلیمر برگزار می کند:




♨️انجمن علمی مهندسی پلیمر برگزار می کند:




طبقه بندی: اطلاعیه،
برچسب ها: پلیمر،

تاریخ : یکشنبه 24 اردیبهشت 1396 | 11:00 ب.ظ | نویسنده : زهرا حاجیان | نظرات
If you’re after basic information on plastic materials, this is the place to find it. Here you’ll learn the definition and properties of polymers, another name for plastics


The simplest definition of a polymer is a useful chemical made of many repeating units. A polymer can be a three dimensional network (think of the repeating units linked together left and right, front and back, up and down) or two-dimensional network (think of the repeating units linked together left, right, up, and down in a sheet) or a one-dimensional network (think of the repeating units linked left and right in a chain). Each repeating unit is the “-mer” or basic unit with “poly-mer” meaning many repeating units. Repeating units are often made of carbon and hydrogen and sometimes oxygen, nitrogen, sulfur, chlorine, fluorine, phosphorous, and silicon. To make the chain, many links or “-mers” are chemically hooked or polymerized together. Linking countless strips of construction paper together to make paper garlands or hooking together hundreds of paper clips to form chains, or stringing beads helps visualize polymers. Polymers occur in nature and can be made to serve specific needs. Manufactured polymers can be three-dimensional networks that do not melt once formed. Such networks are called THERMOSET polymers. Epoxy resins used in two-part adhesives are thermoset plastics. Manufactured polymers can also be one-dimensional chains that can be melted.  These chains are THERMOPLASTIC polymers and are also called LINEAR polymers. Plastic bottles, films, cups, and fibers are thermoplastic plastics.

Polymers abound in nature. The ultimate natural polymers are the deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) that define life. Spider silk, hair, and horn are protein polymers. Starch can be a polymer as is cellulose in wood. Rubber tree latex and cellulose have been used as raw material to make manufactured polymeric rubber and plastics. The first synthetic manufactured plastic was Bakelite, created in 1909 for telephone casing and electrical components. The first manufactured polymeric fiber was Rayon, from cellulose, in 1910. Nylon was invented in 1935 while pursuing a synthetic spider silk.

The Structure of Polymers

Many common classes of polymers are composed of hydrocarbons, compounds of carbon and hydrogen. These polymers are specifically made of carbon atoms bonded together, one to the next, into long chains that are called the backbone of the polymer. Because of the nature of carbon, one or more other atoms can be attached to each carbon atom in the backbone. There are polymers that contain only carbon and hydrogen atoms. Polyethylene, polypropylene, polybutylene, polystyrene and polymethylpentene are examples of these. Polyvinyl chloride (PVC) has chlorine attached to the all-carbon backbone. Teflon has fluorine attached to the all-carbon backbone.

Other common manufactured polymers have backbones that include elements other than carbon. Nylons contain nitrogen atoms in the repeat unit backbone. Polyesters and polycarbonates contain oxygen in the backbone. There are also some polymers that, instead of having a carbon backbone, have a silicon or phosphorous backbone. These are considered inorganic polymers. One of the more famous silicon-based polymers is Silly Putty®.

Molecular Arrangement of Polymers

Think of how spaghetti noodles look on a plate. These are similar to how linear polymers can be arranged if they lack specific order, or are amorphous. Controlling the polymerization process and quenching molten polymers can result in amorphous organization. An amorphous arrangement of molecules has no long-range order or form in which the polymer chains arrange themselves. Amorphous polymers are generally transparent. This is an important characteristic for many applications such as food wrap, plastic windows, headlight lenses and contact lenses.

Obviously not all polymers are transparent. The polymer chains in objects that are translucent and opaque may be in a crystalline arrangement. By definition, a crystalline arrangement has atoms, ions, or in this case, molecules arranged in distinct patterns. You generally think of crystalline structures in table salt and gemstones, but they can occur in plastics. Just as quenching can produce amorphous arrangements, processing can control the degree of crystallinity for those polymers that are able to crystallize.  Some polymers are designed to never be able to crystallize. Others are designed to be able to be crystallized. The higher the degree of crystallinity, generally, the less light can pass through the polymer. Therefore, the degree of translucence or opaqueness of the polymer can be directly affected by its crystallinity.  Crystallinity creates benefits in strength, stiffness, chemical resistance, and stability.

Scientists and engineers are always producing more useful materials by manipulating the molecular structure that affects the final polymer produced. Manufacturers and processors introduce various fillers, reinforcements and additives into the base polymers, expanding product possibilities.

Characteristics of Polymers

The majority of manufactured polymers are thermoplastic, meaning that once the polymer is formed it can be heated and reformed over and over again. This property allows for easy processing and facilitates recycling. The other group, the thermosets, cannot be remelted. Once these polymers are formed, reheating will cause the material to ultimately degrade, but not melt.

Every polymer has very distinct characteristics, but most polymers have the following general attributes.

  1. Polymers can be very resistant to chemicals. Consider all the cleaning fluids in your home that are packaged in plastic. Reading the warning labels that describe what happens when the chemical comes in contact with skin or eyes or is ingested will emphasize the need for chemical resistance in the plastic packaging. While solvents easily dissolve some plastics, other plastics provide safe, non-breakable packages for aggressive solvents.

  2. Polymers can be both thermal and electrical insulators. A walk through your house will reinforce this concept, as you consider all the appliances, cords, electrical outlets and wiring that are made or covered with polymeric materials. Thermal resistance is evident in the kitchen with pot and pan handles made of polymers, the coffee pot handles, the foam core of refrigerators and freezers, insulated cups, coolers, and microwave cookware. The thermal underwear that many skiers wear is made of polypropylene and the fiberfill in winter jackets is acrylic and polyester.

  3. Generally, polymers are very light in weight with significant degrees of strength. Consider the range of applications, from toys to the frame structure of space stations, or from delicate nylon fiber in pantyhose to Kevlar, which is used in bulletproof vests. Some polymers float in water while others sink.  But, compared to the density of stone, concrete, steel, copper, or aluminum, all plastics are lightweight materials.

  4. Polymers can be processed in various ways. Extrusion produces thin fibers or heavy pipes or films or food bottles. Injection molding can produce very intricate parts or large car body panels. Plastics can be molded into drums or be mixed with solvents to become adhesives or paints. Elastomers and some plastics stretch and are very flexible. Some plastics are stretched in processing to hold their shape, such as soft drink bottles. Other polymers can be foamed like polystyrene (Styrofoam™), polyurethane and polyethylene.

  5. Polymers are materials with a seemingly limitless range of characteristics and colors. Polymers have many inherent properties that can be further enhanced by a wide range of additives to broaden their uses and applications. Polymers can be made to mimic cotton, silk, and wool fibers; porcelain and marble; and aluminum and zinc. Polymers can also make possible products that do not readily come from the natural world, such as clear sheets and flexible films.

  6. Polymers are usually made of petroleum, but not always. Many polymers are made of repeat units derived from natural gas or coal or crude oil.  But building block repeat units can sometimes be made from renewable materials such as polylactic acid from corn or cellulosics from cotton linters. Some plastics have always been made from renewable materials such as cellulose acetate used for screwdriver handles and gift ribbon.  When the building blocks can be made more economically from renewable materials than from fossil fuels, either old plastics find new raw materials or new plastics are introduced.

  7. Polymers can be used to make items that have no alternatives from other materials.  Polymers can be made into clear, waterproof films. PVC is used to make medical tubing and blood bags that extend the shelf life of blood and blood products. PVC safely delivers flammable oxygen in non-burning flexible tubing.  And anti-thrombogenic material, such as heparin, can be incorporated into flexible PVC catheters for open heart surgery, dialysis, and blood collection. Many medical devices rely on polymers to permit effective functioning




طبقه بندی: اطلاعات پلیمری،
برچسب ها: پلیمر، polymer، plastic، monomer، polymers، plastics،

تاریخ : دوشنبه 21 فروردین 1396 | 08:31 ق.ظ | نویسنده : Arash Sadeghi | نظرات
  • Construction Waste

AluminumWood
  • Electronics

Cell PhoneElectronicsPrinter Cartridges
  • Glass

Glass
  • Hazardous Waste

AutoChemicalsBatteries

Light BulbsMotor Oil

Paint
Car Tire
  • House Chemicals

  • Household Items


BicycleBooks

ChipBagFurniture

MattressMedical

Makeup
Video
Water Filter
  • CD DVD

  • Organic Waste

Food ScrapsGarden ChemicalsGarden Waste
  • Metal

AluminumBeverageCan

ScrapMetalTins
  • Paper

Food CartonsCardboardPaper
Paper TowelsTissuesPaperboard
  • Plastic

BankCardsBottleCaps

PlasticPlastic Bags

Polystyrene BlockYogurt Pots
  • Plastic Wraps

  • Textiles

/CarpetClothes












reference: www.recyclingnj.com



طبقه بندی: اطلاعات پلیمری،
برچسب ها: polymer، recycling، plastic،

تاریخ : سه شنبه 19 بهمن 1395 | 10:28 ب.ظ | نویسنده : Arash Sadeghi | نظرات

Bottle Caps

Bottle caps are removed and discarded prior to the recycling of plastic or glass bottles and most refuse companies require you to remove the bottle cap before putting the bottle in your recycling box.

Plastic bottles are made from either polyethylene terephthalate (plastic #1) or high density polyethylene (plastic #2) but the plastic caps themselves can be made from high density polyethylene (plastic #2), low density polyethylene (plastic #4) or most often from polypropylene (plastic #5).

The polyethylene caps are the caps that you can deform easily if you squeeze or bend them with your fingers. These can be included with the plastic bottles in your recycling collection. An example of a polyethylene cap, is the flat cap commonly found on the top of plastic milk jugs. These caps push on to the top of the bottle rather than having a screw thread. Caps with a screw thread are usually made from polypropylene.

Polypropylene caps are much harder and more rigid than polyethylene caps, often with a screw on thread, and should not be included in your curbside recycling collection. If you try to bend these caps with your fingers the plastic will only bend a small amount. Polypropylene cap examples are detergent bottle caps, screw caps on soda, water bottles and toothpaste tubes or the flip top caps on shampoo bottles or other cosmetics products.

If you are not sure what type of plastic the cap is made from then place the cap in your general trash and recycle just the bottle.


reference : http://www.recyclingnj.com/



طبقه بندی: پلاستیک ها،
برچسب ها: Bottle Caps، Bottle، Caps، plastic، pp، polymer،

تاریخ : سه شنبه 19 بهمن 1395 | 10:25 ب.ظ | نویسنده : Arash Sadeghi | نظرات

Nanostructured and Functionalized Materials & Devices

Materials for biomedical applications

Molecular functionalization techniques are used to tailor substrates for biomedical applications. Examples include microbicidal surfaces which inhibit biofilm formation; high strength bone cements with bactericidal biopolymers or antibiotic-conjugated monomers which achieved higher antibacterial efficacy longer than the present cements; and magnetic nanoparticles for bioimaging and tumor targeting. In a separate development, the adsorption disruption of oriented liquid crystal molecules on a patterned surface was developed into a new label-free optical method for the simultaneous detection of multiple glycine oilgomers using sample size as little as 2 μL.

Materials for energy applications

Research in energy is focused on the design and synthesis of new and alternative materials for energy supply, transformation, storage, delivery and end-use. There are strong coordinated efforts in developing catalysts for fuel production, and for the non-oil based route to chemicals production. Ceramic membranes are used to produce oxygen from air. Electrochemical energy conversion is another focused research area covering a number of technological areas: anode materials for lithium-ion batteries, catalysts and polymer electrolyte membranes for direct alcohols fuel cells, and materials for supercapacitors.

Materials for optoelectronic applications

Many optical devices based on 3D photonic crystals, such as optical switches, low-threshold lasers and light-emitting diodes, and waveguide, require the exact placement of artificial defects embedded in the interior of the photonic crystals. We have recently embedded artificial line-defects in a 3D photonic crystal using a combination of “bottom-up” self-assembly method and the conventional “top-down” technique. The new technique circumvents some of the problems in the self-assembly approach to fabricating functional photonic devices from photonic crystals.

Polymer and molecular electronics

Molecular memories based on polymers and organic materials have the advantages of simplicity in structure, drive-free read and write capability, good scalability, 3-D stacking ability, low-cost potential, and a large capacity for data storage. By combining molecular design with novel synthesis approaches, several polymer/molecular memories, including flash (rewritable) memory, write-once read-many-times (WORM) memory and dynamic random access memory (DRAM) have been realized. All these devices exhibit stable states with high ON/OFF current ratios (104-107), and perform up to 108 read cycles under ambient conditions.

Self-assembly of nanomaterials

A real-world functional material (e.g. solid catalyst) is a highly organized multi-component materials system. This modern view calls for the development of new strategies promoting the self-assembly of various functional components. For example, catalytic metals such as Au and Co can be introduced to the exterior surfaces or interior spaces of photosensitized metal oxide systems to enhance their functions as preparative nano-reactors. In another development colloidal and interfacial polymerizations are used to produce hydrophilic-lipophilic polymer composite membranes for separation; and micro-spheres and porous continuous media for catalyst immobilization and storage of energetic materials.

reference : http://www.chbe.nus.edu.sg/research/materials#


برچسب ها: materials، polymers، material، nanomaterials، nano،

تاریخ : شنبه 11 دی 1395 | 05:47 ب.ظ | نویسنده : Arash Sadeghi | نظرات


Properties Of Graphene

 Graphene is , basically, a single atomic layer of graphite; an abundant mineral which is an allotrope of carbon that is made up of very tightly bonded carbon atoms organised into a hexagonal lattice. What makes graphene so special is its sp2 hybridisation and very thin atomic thickness (of 0.345Nm). These properties are what enable graphene to break so many records in terms of strength, electricity and heat conduction (as well as many others). Now, let’s explore just what makes graphene so special, what are its intrinsic properties that separate it from other forms of carbon, and other 2D crystalline compounds?

Fundamental Characteristics

Before monolayer graphene was isolated in 2004, it was theoretically believed that two dimensional compounds could not exist due to thermal instability when separated. However, once graphene was isolated, it was clear that it was actually possible, and it took scientists some time to find out exactly how. After suspended graphene sheets were studied by transmission electron microscopy, scientists believed that they found the reason to be due to slight rippling in the graphene, modifying the structure of the material. However, later research suggests that it is actually due to the fact that the carbon to carbon bonds in graphene are so small and strong that they prevent thermal fluctuations from destabilizing it.

Electronic Properties

One of the most useful properties of graphene is that it is a zero-overlap semimetal (with both holes and electrons as charge carriers) with very high electrical conductivity. Carbon atoms have a total of 6 electrons; 2 in the inner shell and 4 in the outer shell. The 4 outer shell electrons in an individual carbon atom are available for chemical bonding, but in graphene, each atom is connected to 3 other carbon atoms on the two dimensional plane, leaving 1 electron freely available in the third dimension for electronic conduction. These highly-mobile electrons are called pi (π) electrons and are located above and below the graphene sheet. These pi orbitals overlap and help to enhance the carbon to carbon bonds in graphene. Fundamentally, the electronic properties of graphene are dictated by the bonding and anti-bonding (the valance and conduction bands) of these pi orbitals.

Combined research over the last 50 years has proved that at the Dirac point in graphene, electrons and holes have zero effective mass. This occurs because the energy – movement relation (the spectrum for excitations) is linear for low energies near the 6 individual corners of the Brillouin zone. These electrons and holes are known as Dirac fermions, or Graphinos, and the 6 corners of the Brillouin zone are known as the Dirac points. Due to the zero density of states at the Dirac points, electronic conductivity is actually quite low. However, the Fermi level can be changed by doping (with electrons or holes) to create a material that is potentially better at conducting electricity than, for example, copper at room temperature.

Tests have shown that the electronic mobility of graphene is very high, with previously reported results above 15,000 cm2·V−1·s−1 and theoretically potential limits of 200,000 cm2·V−1·s−1 (limited by the scattering of graphene’s acoustic photons). It is said that graphene electrons act very much like photons in their mobility due to their lack of mass. These charge carriers are able to travel sub-micrometer distances without scattering; a phenomenon known as ballistic transport. However, the quality of the graphene and the substrate that is used will be the limiting factors. With silicon dioxide as the substrate, for example, mobility is potentially limited to 40,000 cm2·V−1·s−1.

Mechanical Strength

Another of graphene’s stand-out properties is its inherent strength. Due to the strength of its 0.142 Nm-long carbon bonds, graphene is the strongest material ever discovered, with an ultimate tensile strength of 130,000,000,000 Pascals (or 130 gigapascals), compared to 400,000,000 for A36 structural steel, or 375,700,000 for Aramid (Kevlar). Not only is graphene extraordinarily strong, it is also very light at 0.77milligrams per square metre (for comparison purposes, 1 square metre of paper is roughly 1000 times heavier). It is often said that a single sheet of graphene (being only 1 atom thick), sufficient in size enough to cover a whole football field, would weigh under 1 single gram.

What makes this particularly special is that graphene also contains elastic properties, being able to retain its initial size after strain. In 2007, Atomic force microscopic (AFM) tests were carried out on graphene sheets that were suspended over silicone dioxide cavities. These tests showed that graphene sheets (with thicknesses of between 2 and 8 Nm) had spring constants in the region of 1-5 N/m and a Young’s modulus (different to that of three-dimensional graphite) of 0.5 TPa. Again, these superlative figures are based on theoretical prospects using graphene that is unflawed containing no imperfections whatsoever and currently very expensive and difficult to artificially reproduce, though production techniques are steadily improving, ultimately reducing costs and complexity.

Optical Properties

Graphene’s ability to absorb a rather large 2.3% of white light is also a unique and interesting property, especially considering that it is only 1 atom thick. This is due to its aforementioned electronic properties; the electrons acting like massless charge carriers with very high mobility. A few years ago, it was proved that the amount of white light absorbed is based on the Fine Structure Constant, rather than being dictated by material specifics. Adding another layer of graphene increases the amount of white light absorbed by approximately the same value (2.3%). Graphene’s opacity of πα ≈ 2.3% equates to a universal dynamic conductivity value of G=e2/4ℏ (±2-3%) over the visible frequency range.

Due to these impressive characteristics, it has been observed that once optical intensity reaches a certain threshold (known as the saturation fluence) saturable absorption takes place (very high intensity light causes a reduction in absorption). This is an important characteristic with regards to the mode-locking of fibre lasers. Due to graphene’s properties of wavelength-insensitive ultrafast saturable absorption, full-band mode locking has been achieved using an erbium-doped dissipative soliton fibre laser capable of obtaining wavelength tuning as large as 30 nm.

In terms of how far along we are to understanding the true properties of graphene, this is just the tip of the iceberg. Before graphene is heavily integrated into the areas in which we believe it will excel at, we need to spend a lot more time understanding just what makes it such an amazing material. Unfortunately, while we have a lot of imagination in coming up with new ideas for potential applications and uses for graphene, it takes time to fully appreciate how and what graphene really is in order to develop these ideas into reality. This is not necessarily a bad thing, however, as it gives us opportunities to stumble over other previously under-researched or overlooked super-materials, such as the family of 2D crystalline structures that graphene has born.

reference : geraphenea.com 



طبقه بندی: شیمی،
برچسب ها: Geraphenea، geraphen، polymer، properties، material، electricity، carbon،

تاریخ : چهارشنبه 8 دی 1395 | 12:16 ق.ظ | نویسنده : Arash Sadeghi | نظرات

The story of Graphene

If you've ever drawn with a pencil, you've probably made graphene. The world's thinnest material is set to revolutionise almost every part of everyday life.

Fascination with this material stems from its remarkable physical properties and the potential applications these properties offer for the future. Although scientists knew one atom thick, two-dimensional crystal graphene existed, no-one had worked out how to extract it from graphite.

That was until it was isolated in 2004 by two researchers at The University of Manchester, Prof Andre Geim and Prof Kostya Novoselov. This is the story of how that stunning scientific feat came about and why Andre and Kostya won the Nobel Prize in Physics for their pioneering work.




طبقه بندی: شیمی،
برچسب ها: graphene، geraphen، polymer، material، physics،

تاریخ : چهارشنبه 8 دی 1395 | 12:08 ق.ظ | نویسنده : Arash Sadeghi | نظرات

New building materials for the future of construction



نتیجه تصویری برای ‪future materials‬‏


Graphene

 

While not a new material, graphene has been impractical to use in construction since its discovery. In theory, it is an excellent building material, as it is incredibly lightweight while being stronger and stiffer than both steel and carbon fibre. Potentially, it could be combined with more traditional materials to create stronger beams and cables, allowing for more impressive structures.

 

However, graphene is so difficult to produce that builders have rarely been able to use more than a few flakes of it per project. Until now, that is, as the US' Oak Ridge National Laboratory has developed a new way of producing it using a technique known as chemical vapour deposition.

 

Ivan Vlassiouk, leader of the team responsible for the project, said that this discovery "considerably extends the potential applications and market for graphene". The next step is to reduce the cost and improve scalability, then the material can be used much more widely.

 

 

 

Natural concrete

 

Staying on the concrete theme, researchers from MIT have published a paper that proposes taking cement out of the equation altogether. The researchers, from the university's Department of Civil and Environmental Engineering, are looking to the natural world - proposing the use of organic materials like bones, shells and sea sponges to bind the aggregate in concrete together. 

 

The research is a fresh attempt to solve the twin drawbacks of Portland cement - the energy needed to make it, and the potential for microcracking over time. The idea came about when the team contrasted the extensive knowledge on the structure of natural materials with the 'guesswork' on concrete's internal structure - so it made sense to use more familiar materials in a 'bottom-up' approach to concrete production. 'Bone-crete' is not a material ready to be used just yet - it is more of a starting point for engineers to change the way they choose the composition of building products. 



Carbon-fibre balsa

 


Balsa wood is useful thanks to its stiffness despite being incredibly lightweight; however, it is difficult to produce and therefore expensive. However, a team of researchers at Harvard University have managed to create cellular composite materials of unprecedented light weight and stiffness that could replace it.

 

Fibre-reinforced epoxy-based thermosetting resins and 3D extrusion printing techniques have been used to create the synthetic replacement. The researchers used these methods to create a 'honeycomb' effect in carbon-fibre epoxy materials.

 

The end result is something that could potentially completely replace balsa wood. Not only would it be cheaper, it also eliminates the problems the wood has with irregular grains that make it difficult to use in precision structures.


Improved wood

 

Research from the Universities of Warwick and Cambridge has led to new understanding of the molecular structure of wood. This could lead to new uses for plants in construction, as well as an improved version of one of the most common building materials in the world.

 

The scientists found that the xylan polymer - which makes up about a third of wood's structure - has an unusual shape. This enabled them to study how molecules and cells within plant walls are arranged.

 

Professor Paul Dupree of the University of Cambridge said: "This major step forward in understanding the molecular architecture of plant cell walls will impact the use of plants for renewable materials, energy and for building construction."




طبقه بندی: اخبار پلیمری،
برچسب ها: polymers، construction، Graphene، wood، materials،

تاریخ : سه شنبه 7 دی 1395 | 12:49 ق.ظ | نویسنده : Arash Sadeghi | نظرات

What Are Synthetic Polymers?

Check out these images of useful, everyday items. Do you notice anything that they have in common? For one, all these compounds are super strong, cheap, and easy to make. Secondly, they are all examples of this video's topic: synthetic polymers! But what is a synthetic polymer?

Let's break the term apart to discover the definition. To start, a compound that is synthetic is man-made and produced by chemical reactions. Synthetic compounds may be made as exact replicas of naturally occurring compounds like vitamin C, or they may be unique compounds like plastic.

To talk about polymers, imagine a paperclip chain. If you've got time (and lots of paperclips), you can just make one instead of thinking about it! A paperclip chain is like a polymer. It is a long, strong chain made of many paperclips hooked together. By definition, a polymer is a compound that is made of many small repeating units bonded together. In our case, the small repeating units are the paper clips.

We use the scientific term 'monomer' to describe the small, repeating units used to make up a polymer. Polymers usually consist of tens of thousands of monomers, all bonded together. Huge molecules like these are often referred to as macromolecules. Our world is loaded with naturally occurring polymers, like cellulose (the stuff in plant fibers), DNA (the molecule that contain our genes), and silk.

Now, we can put our two terms together! A synthetic polymer is a man-made macromolecule that is made of thousands of repeating units. Sometimes these polymers are straight-chained, like our paperclip chain example, and consist of one long chain of monomers bonded end to end.

Sometimes polymers are both straight-chained and branched. This means that neighboring chains will bond with each other and make vast, net-like structures. This type of bonding between chains is called crosslinking.

Synthetic polymers are lightweight, hard to break, and last a long time. They are quite cheap to make and easy to form into shapes.

One of the most common and versatile polymers is polyethylene. It is made from ethylene (also known as ethene) monomers. In polymer form, the double bond between the carbons is lost and a chain is formed between repeating units of two carbons, each bonded to two hydrogens.

Polymer chain
Polymer chain

Sometimes for brevity's sake, the polymer chain is represented like the image you see here, with a large pair of parentheses around the monomer. You'll notice that there is an n in the bottom right hand corner outside the parenthesis. This n can represent any number. It could be 5 or 10,000! Often times, it is just left as a simple n to show it is a polymer of varying length.

Polyethylene is used to make plastics of all sizes and shapes, from piping to bottles to toys. And if you've ever dealt with these pesky things, then you know polyethylene!

Examples

Polyethylene has a pretty popular cousin, named polyethylene terephthalate (abbreviated PET or PETE). You might recognize PET from our intro! PET is commonly used for packaging liquids, especially sodas. PET is also used to make plastics that need to tolerate extreme temperatures.

PET is a great example of a thermoplastic. Thermoplastics are solid until heated to a certain temperature. When they get to that special temperature, they can be molded into any shape. Once they cool, their shape is set. Thermoplastics can be melted down once they are used up or no longer needed, and reshaped! This process is known as recycling.

Maybe you've seen these symbols on some plastics? They tell you several things. First, the item is a thermoplastic. Also, the number represents the type of polymer. And lastly, this symbol lets you know that this is very recyclable! Next time you are using something in a plastic bottle, look for one of these symbols. Then when you're finished using the plastic bottle, make sure to recycle it




طبقه بندی: اطلاعات پلیمری،
برچسب ها: polymer، monomers، material، plastic، synthetic، polymers،

تاریخ : سه شنبه 7 دی 1395 | 12:43 ق.ظ | نویسنده : Arash Sadeghi | نظرات

What Are Polymers

What do DNA, a plastic bottle, and wood all have in common? Give up? They are all polymers!

Polymers are very large molecules that are made up of thousands - even millions - of atoms that are bonded together in a repeating pattern. The structure of a polymer is easily visualized by imagining a chain. The chain has many links that are connected together. In the same way the atoms within the polymer are bonded to each other to form links in the polymer chain.

The molecular links in the polymer chain are called repeat units that are formed from one or more molecules called monomers. The structure of the repeat unit can vary widely and depends on the raw materials that make up the polymer. For example, polyethylene, the polymer used to make a wide variety of plastic bags and containers, has a very simple repeat unit, two carbons that are bonded to one another to form a single link.




طبقه بندی: اطلاعات پلیمری،
برچسب ها: polymer، chain، molecular، monomer، material،

تاریخ : سه شنبه 7 دی 1395 | 12:38 ق.ظ | نویسنده : Arash Sadeghi | نظرات

 ?What Is Carbon

The entire world is made out of atoms. The table your computer screen is sitting on, the clothes you're wearing, the air you breathe... even your body is made out of atoms. And those atoms come in many different types. We call those different types of atoms elements.

Carbon is one of the elements; one type of atom. It contains six protons and six neutrons in its nucleus, with six electrons orbiting around the outside. The number of protons and electrons is what determines its properties, and those properties are incredibly important. Without carbon, we humans would not exist.

Carbon looks very different in its many shapes and forms. Diamond is made of carbon. But so is the graphite in your pencil, the charcoal in a fire and the coal in a power plant. Carbon dioxide, a molecule made out of carbon and oxygen and is something you breathe out, is also the gas most responsible for climate change. So, carbon is totally different in its many different forms.

But, from our perspective as humans, the important thing is that carbon is the basis for life on Earth. We, as humans, are considered to be carbon-based life.

Carbon-Based Life

Carbon is the most important component of all life found on Earth. Even the most complex molecules that make us up contain carbon bonded to other elements: carbon bonded to oxygen, carbon bonded to hydrogen, carbon bonded to nitrogen. You name it - it has carbon.

There are certain key molecules that are a big part of our bodies and the bodies of other living organisms. Proteins, for example, form almost our entire bodies, and proteins on Earth are based on carbon. Nucleic acids are vitally important to animal life, and indeed also contain carbon. Carbohydrates and lipids (fats) are also major parts of the bodies of animals like us. All of these things are reliant on carbon. For this reason, life on Earth is known as carbon-based life, or life that contains building blocks that are made up of combinations of carbon and other elements.

We often assume, therefore, that if we were to find life on other planets, in other parts of the universe, that it would also be carbon based. But some say that we are foolish to make that assumption. There are other elements, like silicon, for example, that contain many of the properties of carbon. Perhaps if we ever meet aliens, their bodies will be made of silicon, not carbon! There's a famous episode of Star Trek where they did just that. I guess there's only one way to find out




طبقه بندی: شیمی،
برچسب ها: carbon، element، life، polymer،

تاریخ : یکشنبه 5 دی 1395 | 01:20 ق.ظ | نویسنده : Arash Sadeghi | نظرات
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