Chemical articles

Kevlar As Bulletproof Vest Material

Bulletproof vests are protective clothing to minimize bullet injury. Usually used by military and police personnel in certain tasks. Materials for bulletproof vests include metal (steel or titanium), ceramic or polymer type which can provide extra protection against the vital parts of the wearer.

This vest protects the wearer by holding back the bullet. The bullet is stopped before penetrating into the body. When the vest holds the bullet penetration, the drive from the bullet is reduced by spreading its momentum throughout the body. Users will still feel the kinetic energy of the bullet, this can cause bruises, swelling or serious internal injuries.

One of the polymers developed as a modern anti-bullet vest material is kevlar. Kevlar is also known as twaron and poly-paraffenylene terephthalamide, a synthetic fiber whose strength is five times the strength of copper, of the same weight. Kevlar is extremely resistant to heat and decomposes above 400 oC without melting. Kevlar was invented by the DuPont company in the early 1960s, the work of Stephanie Kwolek. Kevlar is a registered trademark by E.I. De Pont de Nemours and Company.

Properties

Kevlar is one type of aramida, which consists of long chain polymers with parallel orientation. Aramide itself is a synthetic fiber in the form of a long chain of synthetic polyamides with at least 85 percent of its amid link attached directly to two aromatic chains (amide groups and alternating aromatic groups). Kevlar strength is obtained from intra-molecular hydrogen bonds and interaction of aromatic powders between sheets. These interactions are stronger than the interactions of Van der Waals contained in other synthetic polymers and fibers such as dyneema (fibers made from very long polyethylene chains, arranged in the same direction). The presence of other salts and impurities, usually calcium, may interfere with the interaction of polymer sheets and must be eliminated in the production process. Kevlar consists of relatively rigid molecules, which form structures such as flat sheets on silk proteins.

Of these properties obtained fiber with high mechanical strength and heat resistance.

Kevlar has free groups that can form hydrogen bonds on the outside, so they can absorb water and have good 'wet' properties. It also makes it feel more natural and 'sticky' compared to polymers in general, such as polyethylene.

The main weakness of kevlar is that it can decompose under alkaline conditions or when exposed to chlorine. Although it can support large tensile stress, kevlar is not strong enough under compressive pressure. To overcome this problem, kevlar is often used in conjunction with strong materials against compressive pressures.

Production

Kevlar is synthesized from monomers 1, 4-phenyliamylamine (para-phenylenediamine) and terephthaloyl chloride. The result is an aromatic amido polymer (aramide) with a benzene ring and an alternating amide group. With this production step, randomly assembled polymer sheets are produced. To make kevlar, the materials are dissolved and stirred, resulting in a fiber-oriented polymer chain.

Kevlar is expensive because of the difficult use of concentrated sulfuric acid in its production. This extreme condition is required to maintain the high polymer toxicity in solution during synthesis and stirring.

DSM's Dyneema, Akzo's Twaron, Toyobo's Zylon (controversial, recent study, the material is rapidly degraded so that the wearer is not as protected as expected), or Honeywell's GoldFlex - all trademarks. The new materials are lighter, thinner, and more resistant than kevlar, but the price is more expensive. (Reader: From various sources).

Literature:

https://andrycalongurukimia.wordpress.com/2011/04/22/kevlar-sebagai-bahan-rompi-anti-peluru/

Dialogue between teachers and students with a scientific approach

Dialogue Chemical

The scientific approach is a scientific approach promoted by the Curriculum 2013. Steps on a scientific approach are forms of adaptation of scientific steps to science. The learning process can be matched by a scientific process. The 2013 curriculum mandates the essence of a scientific approach in learning. The scientific approach as a golden bridge of development and development of attitudes, skills, and knowledge of learners. In processes or work processes that meet the scientific criteria, the scientists put forward inductive reasoning (inductive reasoning) with deductive deductive deductiv). Principles of learning activities with curriculum curriculum approach 2013, namely:

1.  learners are facilitated to find out;

2.  learners learn from various learning sources;

3.  learning process using scientific approach;

4.  competency-based learning;

5.  integrated learning;

6.  learning that is being verified that has multi-dimensional value;

7.  aplicative skill-based learning;

8.  improving the balance, continuity and linkage between hard skills and soft skills;

9.  learning that prioritizes learners and empowers learners as lifelong learners;

10.  learning that implements values by giving exemplary (Ing Ngarso Sung Tulodo), building the will (Ing Madyo Mangun Karso), and developing the creativity of learners in the learning process (Tut Wuri Handayani);

11.  ongoing learning at home, at school, and in the community;

12.  utilization of information and communication technology to improve efficiency and efficiency of learning;\

13.  recognition of individual differences and the cultural background of learners;

14.  fun and challenging learning atmosphere.

The following examples of learning activities and descriptions of scientific approaches to the learning curriculum of 2013 are:

1. Observe: reading, listening, listening, seeing (without or with tools) to identify things you want to know - Observe with the senses (reading, listening, listening, watching, watching, etc.) with or without tools.

 2. Asks questions about things that are not understood from what is observed or questions to get additional information about what is observed - Create and ask questions, frequently asked questions, discuss about information that has not been understood, additional information to be known, or As a clarification.

3. Trying / collecting data (information): conducting experiments, reading other sources and textbooks, observing objects / events / activities, interviews with resource persons - Exploring, trying, discussing, demonstrating, imitating forms / moves, conducting experiments, reading other sources In addition to textbooks, collect data from resource persons through questionnaires, interviews, and modify / add / develop.

4. Associate / process information: STUDENTS process information that has been collected either limited from the results of collecting activities / experiments as well as the results of observing activities and gathering information - processing information that has been collected, analyzing data in the form of making categories, associate or connect phenomena / Related information in order to find a pattern, and conclude.

5. Communicating: STUDENTS submit results of observations, conclusions based on the results of oral, written, or other media analysis - presents reports in the form of charts, diagrams, or graphs; Prepare a written report; And present the report covering the process, results, and conclusions verbally. 6. (Can proceed with) Creating: STUDENT innovates, creates, designs models, designs, products (works) based on learned knowledge.

The following is a dialogue between teachers and students based on a scientific approach

Teacher      :  Today we will learn about the specific hydrocarbon compounds the difference between alkanes, alkenes and alkalo, have you studied them at home?

Student      : (Silent)

Teacher      : Well today we will discuss it, who knows what is hydrocarbons

Student 1   : According to the book I have abaca hydrocarbon is a compound consisting of elements of carbon atoms (C) and hydrogen atoms (H). All hydrocarbons have carbon chains and hydrogen atoms binding to the chain.

Teacher      : additional?

Student 2   : In saturated and unsaturated hydrocarbon chemistry, which is saturated as an unsaturated alkane of alkenes and alkalo

Student 3   : Sorry miss i want to ask why can there be a classification between saturated and unsaturated compounds?

Teacher      : Good question, Based on the type of bond between the carbon atoms, the hydrocarbons are distinguished by saturation and unsaturation. If all carbon-carbon bonds are single bonds (-C-C-), they are classified as saturated hydrocarbons. If there is one double bond (-C = C-) or triple bond (-C C-), it is called an unsaturated bond. That is why alkanes can not be added to other substances.

Student 2   : Then what is the difference between alkanes alkene and alkalo?

Teacher     : 1. Alkanes are saturated hydrocarbons, which means having a single bond between the carbon atoms; Alkene is an unsaturated hydrocarbon which means comprising one or more double bonds between the carbon atoms; Alkalo is also unsaturated hydrocarbons with one or more triple bonds between the carbon atoms.

   2. The general formula for alkanes is CnH2n + 2, the general formula for alkene in the case of non-cyclic compounds is CnH2n whereas the general formula for the alkalo in the case of noncyclic compounds is CnH2n-2.

  3. Alkanes are the most stable hydrocarbons because carbon bonds are difficult to solve. They have remained unchanged for millions of years, alkenes are less stable than alkanes and more stable than alkalo, the alkalo is more reactive than alkanes and alkenes.

  4. Alkanes are also called paraffins, alkenes are also called olefins, alkalo is also called acetylene.

Student 1   : What reaction happens to alkene and alkalo?

Teacher      : Reaction in the alkene there is combustion, addition and polymerization whereas in    the alkalis the addition of polymerization, combustion and substitution

Student 3   : How to distinguish between adduct reactions in alkene and alkalo?

Teacher     : The addition reaction to the alkene compound is sufficient one time then the alkenes will turn into alkanes. While the alkaline requires two times pengadisian. Well that's just our meeting on this day I end the wassalamualikum wr.wb

chemical vocabulary

CHEMICAL VOCABULARY

NO	VOCABULARY	EXPLANATION
1	acid dissociation constant (Ka)	This is equal to the ratio of the concentrations of an acid's conjugate base and the acid present when a weak acid dissociates in water. That is, if you have a solution of Acid X where the concentration of the conjugate base is 0.5 M and the concentration of the acid is 10 M, the acid dissociation constant is 0.5/10 = 0.05.
2	activation energy	The minimum amount of energy needed for a chemical reaction to take place. For some reactions this is very small (it onl takes a spark to make gasoline burn). For others, it's very high (when you burnmagnesium, you need to hold it over a Bunsen burner for a minute or so).
3	Avogadro's Law	If you've got two gases under the same conditions of temperature, pressure, and volume, they've got the same number of particles (atoms or molecules). This law only works for ideal gases, none of whichactually exist.
4	calorimetry	The study of heat flow. Usually you'd do calorimetry to find the heat of combustion of a compound or the heat of reaction of two compounds.
5	chromatography	This is when you use a system containing a mobile phase (usually a liquid in general chemistry classes) and a stationary phase (something dissolved in the liquid) to separate different compounds. This is usually done by exploiting the differing polarities of solutes, though you can do it a whole slew o' ways.
6	circuit	The closed path in a circuit through which electrons flow.
7	coagulation	When you destroy a colloid by letting the particles settle out.
8		decomposition: When a big molecule falls apart to make two or more little ones.
9	degenerate	Things (usually orbitals) are said to be degenerate if they have the same energy. This term is used a whole lot in quantum mechanics. Also when dealing with kids who steal cars.
10	delocalization	This is when electrons can move around all over a molecule. This happens when you have double bonds on adjacent atoms in a molecul(conjugated hydrocarbon)
11	endothermic	When a process absorbs energy (gets cold).
12	functional group	A generic term for a group of atoms that cause a molecule to react in a specific way. It's really common to talk about this in organic chemistry, where you have "aldehydes, carboxylic acids, amines" and so on.
13	gamma ray	High energy light given off during a nuclear process. When a nucleus gives off this light, it goes to a lower energy state, making it mor stable.
14	geometrical isomer:	isomerism where atoms or groups of atoms can take up  different positions around a double bond or a ring. This is also called cistrans-isomerism.
15	heterogeneous mixture	A mixture where the substances aren't equally distributed.
16	homogeneous mixture:	A mixture that looks really "smooth" because everything is mixed up really well.
17	irreversible reaction	A chemical reaction in which the reagents make products but the products can't reform reagents. Most chemical reactions in basic chemistry classes are thought of as being irreversible.
18	isotonic solutions	Solutions containing the same osmotic pressure
19	Lewis acid	An electron-pair acceptor (carbonyl groups are really good ones)
20	Lewis base:	An electron-pair donor. Things with lone pairs like water and ammonia are really good ones.
21	Lewis structure	A structural formula that shows all of the atoms and valenceelectrons in a molecule.
22	ligand	A molecule or ion that sticks to the central atom in a complex. Common examples are ammonia, carbon monoxide, or water.
23	limiting reagent	If you do a chemical reaction and one of the chemicals gets used up before the other one, the one that got used up is called the "limiting reagent" because it limited the amount of product that could be formed. The  other one is called the excess reagent.
24	line spectrum	A spectrum showing only certain wavelengths.
25	mechanism	A step-by-step sequence that shows how the products of a reaction are made from the reagents. Mechanisms are very frequently shown during organic chemistry.
26	molality	The number of moles of solute per kilogram of solvent in a solution. This is a unit of concentration that's not anywhere near as handy or common as molarity.
27	molar mass:	The mass of one mole of particles.
28	molar volume:	The volume of one mole of a substance at STP. If you believe that everything is an ideal gas, this is always 22.4 liters. Unfortunately,there's no such thing as an ideal gas.
29	molecular compound	A compound held together by covalent bonds.
30	molecular formula	A formula that shows the correct quantity of all of the atoms in a molecule.
31	monatomic ion	An ion that has only one atom, like the chloride ion.
32	optical isomerism	Isomerism in which the isomers cause plane polarized light to rotate in different directions.
33	orbital	This is where the electrons in an atom live.
34	organic compound	A compound that contains carbon (except carbondioxide, carbon monoxide, and carbonates)
35	osmosis	The flow of a pure liquid into an area of high concentration through a semi-permeable membrane
36	oxidation number	The apparent charge on an atom.
37	STP	See standard temperature and pressure.
38	unshared electron pair:	two electrons that aren't involved in chemical bonding. Also frequently referred to as a "lone pair".
39	unshared electron pair	two electrons that aren't involved in  chemical bonding. Also frequently referred to as a "lone pair".
40	valence electron	The outermost electrons in an atom.
41	synthesis	When you make a big molecule from two or more smaller ones.
42	system	Everything you're talking about at the moment.
43	temperture:	A measurement of the average kinetic energy of the particles in a system