Guzhenko Artyom

In this work, the student is trying to find out whether the color black really attracts more Sun rays, and white repels them.

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Research work on the topic "Black or White?"

Head: Ovsyannikova M.N.,

Primary school teacher

One hot summer day, Mom and Dad and I decided to go for a walk. I put on a black T-shirt and a dark cap, but my mother said that I would be hot in these clothes, since the black color attracts the sun's rays more. I, of course, listened to my mother and changed into light clothes, but decided to think about this issue. Why then do people with black skin color live in African countries, because they must be very hot. And why do polar bears live in the cold north, probably they are cold?

Problem

Is not it White color reflects the sun's rays, and black "attracts" them?

Hypotheses

Perhaps the rays "do not see" the white color?

Let's assume that dark clothes are just brighter and more noticeable.

Let's assume that this is just a superstitious omen.

Target

Find out if the black color really attracts the sun's rays more strongly, and the white one repels them.

Tasks

Get acquainted with additional literature and Internet materials on this issue;

Contact a physics teacher for advice;

Conduct an experiment to confirm or refute this issue;

Prepare a presentation - a report on the work done.

Theoretical part

First, I decided to find out why people with black skin live in Africa. If black attracts the sun's rays more strongly, then you will not envy these people ...

From books and encyclopedias, I learned that according to ancient legend, before all people had black skin color. One day they discovered a lake with water that stained a person white, which was no longer washed off after. People went to this lake and, having plunged into it, acquired a white skin color. When the turn came to the inhabitants of Africa, there was already so little water left in the lake that they could dip only the palms of their hands and feet into the water. That's why Africans are black.

There is another explanation why there are people with black skin in hot countries, which is more like truth than legend.

It turns out that the skin of such people is rich in melanins, that is, substances that are found in the skin, human tissues, hair, and even the retina of the eye. Melanins are widely distributed in plant and animal tissues. They determine the color of the skin and hair, for example, the color of horses, the color of bird feathers, and fish scales. Melanins also absorb ultraviolet rays and, accordingly, protect tissues from burns. That is, nature itself figured out how to protect the inhabitants of hot countries from burns and made them black .... So, people with dark color the skin is better protected from ultraviolet radiation than from light or heat. That's the whole question...

But why do polar bears live in the cold north? It is very cold in the habitat of these predators, so every ray of sunlight that gives warmth is valuable. And the white color of the bears' fur must reflect light well - dark wool would heat up much better. But then the bear among the ice and snow would be visible from afar. There is no one to be afraid of a predator - with its size, it simply has no enemies. After the ban on hunting polar bears, they stopped being afraid of people. But camouflage on the hunt is very much needed. Indeed, among the snow-white landscape, only black eyes, nose and lips give out a bear approaching prey.

It turns out that the skin polar bear black! But how does light make its way to the body through a thick fur coat? In fact, the hairs are hollow (empty) inside, and the rays easily reach the black skin, to which they transfer heat.

From additional literature and from a physics teacher, I learned that all colors found in nature are divided into achromatic (colorless) and chromatic (colored).

Achromatic include white and black, as well as all gray colors, which are obtained by mixing white and black colors. There are no achromatic colors in the spectrum. In nature, there are no such bodies that would completely reflect the entire light flux falling on them, and all bodies absorb light to one degree or another.

Black and white colors reflect light differently. Magnesium oxide powder, which is the whitest object, has the strongest reflection.

But black velvet absorbs light best, it seems to us the blackest object.

Practical part

To make sure the surfaces dark color absorbs light better let's do an experiment.

We will need two plastic bottles with screw caps. We paint one bottle black, wrap the other with white tape. Let's hang the bottles with their necks down, put them between them. table lamp. It should be located quite close to the bottles, at an equal distance from each.

With an awl, we will make holes in the plugs, insert transparent hoses into them. We hang the free ends of the hoses at the level of the bottom of the bottles. As a result, each bottle with a hose should resemble English letter U.

Now the resulting structure must be filled with water. Remove the bottles, disconnect the hoses. Pour water into the first hose to half, pour it into a bottle. For clarity, add potassium permanganate to the water. We twist the cork, insert the hose and hang the bottle. Fluid will fill the bottom of the hose. We will do the same with the second bottle. When the whole structure takes its initial position, the liquids in the two hoses should be at the same level. Turn on the lamp and see what happens.

Result

After turning on the lamp, almost immediately the water began to move in the hose, which is connected to the black bottle. She climbed up the hose and began to go outside. The water from the tube attached to the white bottle rose slightly. What follows from this? The switched on lamp heats the bottles and the air in them. When heated, the air expands and pushes against the water in the hose. Under air pressure, it rises and reaches the tip of the hose the faster, the faster the air heats up, and, consequently, the surface of the bottle itself. From experience it can be seen that the first to reach the finish line was water from a hose connected to a black bottle. In addition to color, the bottles did not differ in anything, the experimental conditions for them were the same. It follows that black surfaces heat up faster.

findings

Thus, the hypotheses that the rays "do not see" the white color, that dark clothes are simply brighter and more noticeable, or that this is just a superstitious omen, have not been confirmed.

As a result of the experiment, I found out that black absorbs light better than white. So, really, in hot sunny weather, you need to wear light-colored clothes.

Practical significance

The materials of the work can be used in the lessons of the surrounding world and for conversations on the prevention of sun or heat stroke with children in a summer health camp. ;

Aqua-Flex Sun Reflect

Repels the heat of the sun's rays and transmits light rays.

Polyurethane transparent greenish paint on water based for painting external glasses and areas of structures exposed to the sun. Repels up to 85% of the heat of the sun's rays, thereby preventing heating, filters and transmits only light.

Protective paint for structures and structures sensitive to heat, repels the heat of the sun's rays, thereby preventing heating, one-component and very easy to use, used for coating exterior surfaces.

It is also produced on the basis of two-component polyurethane for greater stability in conditions external environment for many years.

Properties:

- repels most of the heat of sunlight, prevents heating of painted surfaces;

- prevents heating of structures where people and equipment are located;

- water-soluble, one-component, easy to use;

- economical, for coloring thin layer;

- allows you to significantly save energy for cooling and air conditioning.

Application:

- for painting exterior walls, windows, roofs of residential and industrial buildings;

- for painting exterior walls and roofs made of metal that heats up in the sun;

- for painting the outer surfaces of vehicle cabins in hot conditions and in strong sun;

- for painting the outer surfaces of containers and trailers with equipment;

- for painting the outer surfaces of closed military vehicles;

- for painting the outer surfaces of motorized parts of equipment and weapons.

Specifications:

— theoretical consumption - 1 liter per 8 m;

- elasticity - 1 mm (Sheen);

- density - 1.0 - 1.2 g / cm 3 ;

- viscosity - 1000-3000 Pa.s (Brookfield);

- hardness - 3 Dg (Erickson);

- abrasion - 120 microns - 850 cycles (Gardner) ASTM;

- heat recovery - 80-85% on average on the surface "polyflex white" (SRI ASTM E 1980 = Reflectance ASTM E 903: Surface Emimitance ASTM E 408);

- heat recovery - 90-100% on average on white TPO sheets or on a surface coated with aluminum.

Compound:

- high-quality polyurethane emulsion, stable in outdoor conditions;

— fillers, pigments;

- special substances for repelling heat;

- supplements.

Colors:

- translucent white.

Shine:

- silk.

Dry to Touch:

- 60 minutes.

Drying between coats:

— 2-8 hours, final - 24 hours.

Application method:

- brush, roller, spray;

Dilution:

— water;

- brush, roller - 10-20%;

- spraying - the first layer 30%, the second layer - 5%.

Surface preparation:

— clean the surface of dust, grease, dirt and old paint;

- handle sandpaper, remove dust with pressurized air.

Primer:

— new wall– sand the wall, remove dust and cover with a layer of Denbertex Primer;

– roof – a layer of Aqua-Flex White on resin or bitumen sheets;

— old paint– clean with sandpaper, remove dust and apply a layer of Denbertex Primer;

– old roof – clean with high pressure water, dry and apply Aqua-Flex White;

- corrugated roof and others - Tutgum Universal;

– steel containers with equipment, armored vehicles– Epoxy Primer Anti-Corrosion, if there is light rust – Epoxy Primer Rust Converter.

Supplied packaging:

— 5 l, 18 l, 200 l.

Storage conditions:

— in a dark place at room temperature.

Shelf life:

- 12 months in original packaging.

Cleaning tools:

- soap and water immediately after work.

Precautionary measures:

- do not eat;

- Keep out of the reach of children;

- apply paint in a well-ventilated area;

- wear protective goggles, clothing and gloves for work;

- in case of ingestion, immediately consult a doctor;

- in case of contact with skin and eyes, rinse large quantity water and consult a doctor;

- Read the safety instructions on the packaging carefully.

Quality control:

— produced at the manufacturer's enterprise in accordance with the specification of the Institute of Standards;

— ISO 9001-2008.

Please pay attention:

Specifications are general information, whichdoes not commit to anything. The product is intended for professional use professionals with experience in the field.Specifications are not a substitute for advice, training and guidance.Before the main application should be tested on a small area. Specifications are subject to change and change, current versions are available upon request. You can get the names of professional consultants by phone. Please read the MSDS Safety Instructions carefully before using this product.

Ecology of consumption. Whether it's the roof of your car or the roofs of your houses, there are some things you don't want to heat up in the sun. They not only become unpleasant to the touch, but also prematurely lose their working qualities.

Whether it's the roof of your car or the roofs of your houses, there are some things you don't want to heat up in the sun. They not only become unpleasant to the touch, but also prematurely lose their working qualities.

While one solution to this problem is to paint surfaces white, a scientist at Johns Hopkins University has developed another way - glass-based reflective paint.

Dr. Jason Benkoski makes his paint from cheap and available material- potassium silicate, a raw glass ingredient that dissolves in water. He modifies it in such a way that the material can be sprayed onto the surface and dried, thereby making it waterproof. The scientist also adds pigment to give color and enhance the reflective properties.

The paint is almost entirely inorganic, which should make it much more durable than traditional organics. polymer paints which lose their qualities under the influence sunlight. In addition, it does not emit as many volatile organic compounds that are harmful environment with which traditional paints are rich.

Also, instead of cracking, this paint has the ability to expand and contract with the metal surfaces it has been applied to.

The paint is mixed with a white pigment to reflect sunlight so it can be applied to any surface to maintain a constant temperature. This will not only help to keep the temperature of the building, but will also reduce the demand for air conditioners, and will also extend the life of any metal surface, as it reduces the negative effect of heat on metal structures.

The scientist says that despite the fact that the paint hardens, it continues to retain

While Benkoski designed his paint primarily for use on warships, he envisions it being used on things like playground equipment, grandstands, or roofs. Field trials are scheduled to begin within two years. published

Traditionally, summer clothes are made from fabrics light colors. It is believed that light-colored clothing reflects the sun's rays, and a person is not so hot in the sun. However, experts strongly recommend in hot sunny days wear dark clothes. It is she who protects our skin from harmful effects. ultraviolet rays capable of causing skin cancer.

People who want to protect themselves from harmful ultraviolet rays should dress in dark clothes, not bright Hawaiian shirts, experts say. Yellow shirts provide the least protection from the sun. Few would think of wearing black or dark blue clothes on a hot sunny day, but scientists from the University of Catalonia, Spain, advise choosing these colors. “The color of the fabric has a tremendous influence on its protective properties from ultraviolet radiation, ”says study author Dr. Ascension Riva (Ascension Riva).

Traditional for warm weather white and yellow colors put a person at greater risk of developing skin cancer, scientists say. And dark and more saturated colors better absorb the sun's rays. Dark blue and red colors are especially good in this aspect - they protect the skin best of all. The scientists wrote about this in the pages of the journal Industrial and Engineering Chemistry. In the course of work, they dyed the same cotton fabric in various shades of red, blue and yellow flowers and then measured the ability of each sample to absorb ultraviolet rays.

Most people who go to resorts rely on clothing to protect themselves from the scorching sun, although regular sunscreen would suffice. Keep in mind that white T-shirts and tight-fitting tank tops, as well as wet bathing suits, do not protect well from ultraviolet rays. Scientists believe that this information can be useful not only to consumers, but also to clothing manufacturers to create products that can effectively protect from the sun.

UV curing ink contains substances that react to exposure to ultraviolet radiation and therefore air dry. Such a colorful material is used for various kinds printing, for example, offset, flex, screen, to reproduce raster graphics. It is applied to any surface - paper, plastic, polyethylene, in a thick or thin layer.

During the printing process, UV lamps are used, which fix the ink applied to the product. Some UV curing inks are toxic and should not be used on food packaging. But during drying, they do not emit solvents into the air, unlike solvent formulations. However, when using lamps, ozone is released, which can be toxic if its concentration in the air is high.

Paint Features

UV-curing paint differs from conventional solvent-based formulations in its ability to dry and "set" almost instantly. Other Features of UV Coloring Materials:

• rigid structure;
• more viscous, sticky;
• resistant to moisture;
• does not rub off as quickly as solvent paints;
• hardens (dries) only under the influence of UV radiation.

As part of UV-curable inks:

• a pigment or dye that gives the base color to the coating;
• specialized liquid binder, which turns into a solid film, polymerizes under the influence of UV rays;
• photoinitiator involved in chemical reaction polymerization or curing of the paint layer;
• UV hardener are oligomers, which are viscous substances that harden under the influence of ultraviolet light;
• monomers - solvents, vegetable oils;
• additives, waxes and fillers.

On a note! The coloring composition is a powder of curable polymers that is heated, melted and forms a strong film on paper, plastic or wood.

An interesting feature of ultraviolet curing paints is that the layer is fixed faster on a white material, and slower on a dark one, because a light background repels UV radiation, while a black one, on the contrary, absorbs it.

Curing methods

The last stage in obtaining a layer of paintwork material is drying. The dispersed medium in the process of drying powder varnishes and paints is air. The film is obtained because the solid polymer particles in the composition of the material form a strong bond, first melt, then cure. The coloring composition heats up to 110 degrees and hardens in a matter of seconds.

UV Sources

The optimization of the curing process depends on the choice of UV emitter. Sources of UV light can be:

• electrodeless, LED, quartz emitters;
• mercury lamps;
• fluorescent, xenon lighting devices;
• Led UV drying lamps.

The main rule when choosing a hardener paintwork machines - the radiation frequency of the device must match the absorption frequency of the photoinitiator, which is responsible for the optimal dose of UV rays and the ability of coloring materials to enter into a chemical reaction.

For powder curing paintwork materials wide spectrum lamps can also be used, but they have significant drawbacks:

• energy consumption;
• toxicity.

Attention! These devices, when heated, release a large amount of ozone into the air, which adversely affects health.

Coating quality

The curable polymers in the composition of paints and varnishes form a durable film during the drying process. The thickness of the layer does not affect the quality of the result. paint material:

• lies flat;
• does not spread beyond the boundaries of the image;
• distributed evenly.

Quality is affected by:

• a coloring composition, which includes a pigment, a diluent, a resin, a photoinitiator, fillers, a synergist;
• painted surface;
• the conditions under which painting takes place;
• radiation dose;
• type of UV device;
• the distance between the lamps and from the radiation source to the substrate.

The colorful coating is durable, resistant to moisture, does not fade under the influence of sunlight, other radiation, so even full-color images applied with UV-curable inks come out of high quality.

Advantages and disadvantages of UV curing technology

The UV curing method is environmentally friendly. Other advantages of modern technology:

• short drying time of varnish or paint;
• high performance;
• economy because drying finished products does not take time;
• application in parts, for example, painting a specific area of ​​\u200b\u200bthe surface;
• reuse of the rest of the paintwork materials or the stacked paintwork material;
• applying a thin layer is sufficient for High Quality finished product;
• strength and durability of the painted surface;
• low explosiveness;
• health safety.

UV curing technology also has disadvantages:

• use on automatic lines pays off only in case of high production volumes;
• the price of paints and varnishes is higher than similar solvent or folic;
• if you need to paint non-flat surfaces, drying takes longer;
• to achieve high quality, the curing process must be slowed down.

In addition, if layer defects, such as smudges, drops, have formed on the surface to be painted, most often they cannot be eliminated.

There are several types of paints and varnishes on the market. coloring compositions which dry out under the influence of ultraviolet light.

Specificity of UV curing inks

Print shops use acrylic, water-based, polyester varnishes and colorful materials that are cured by UV radiation.

Acrylic

These paints dry in just a few minutes and are highly reactive with almost 100% dry residue. Contains no UV hardener. The hardness and strength of the resulting layer makes it possible to use the material for painting parquet flooring. They are environmentally friendly, in the process of drying they almost do not emit fumes. However, upon contact with open skin, they harm the epidermis, so it is necessary to work with acrylic coatings with gloves, a respirator and goggles. Due to their high viscosity, acrylic coatings cannot be applied by spraying.

Polyester

These paints and varnishes are inexpensive, but require blowing to dry completely. Cures upon impact a large number ultraviolet lamps. Suitable for spray application. Coatings tend to turn yellow during UV curing.

Waterborne

Characteristics of these paints and varnishes:

• environmental friendliness;
• high quality;
• security.

Waterborne coatings do not yellow and are suitable for spraying. When dried, they form durable pigment layers of high quality. Absolutely harmless in contact with open skin. They are more expensive than acrylic and polyester, require convective drying.

Comparison Chart for Acrylic, Polyester and Waterborne UV Inks

UV inks in printing

UV curing technology is used in almost all printing methods:

• screen printing of all kinds;
• flexo printing;
• silk screen printing;
• offset sheet and roll;
• polygraphy;
• wide format, inkjet printers.

Due to the unique properties of coloring materials to cure almost instantly, it is possible to print with UV inks on different materials:

• paper;
• wood;
• plastic;
• film;
• plastic.

If you are printing on non-absorbent materials such as polyethylene films, it is necessary to control the tension of the surface, because the problem of adhesion of the ink layer to the film or plastic can be a time bomb. Defects will become visible later, and it will be impossible to fix the marriage, so the tension is checked with special ink or test pencils.

During printing, the following climatic conditions must be observed:

• temperature from 18 to 24 degrees;
• humidity from 50 to 60%.

Important! Light from fluorescent lamps and sunlight should not fall on the printing press, cans of coloring materials. For window protection, yellow filters and lamps of a safe yellow and white spectrum should be used.

Finished products can be coated with UV curing varnishes that protect products and create special effects such as glossy or matte surface. UV varnishing is considered an environmentally friendly, safe and cost-effective technology.

In general, UV-cured inks and varnishes are popular in Moscow printing shops, because they give good results even when printing on “capricious” materials.