Resumo de Organic Coatings:science And Technology

DEAR FRIENDS, TODAY, I WILL TALK ABOUT THE PHYSICAL PARAMETER, ?GLOSS?, OF A SURFACE. THE SURFACE CAN BE ANYTHING LIKE A BARE WOODEN, A BARE METALLIC, A BARE PLASTIC OR THE PAINTED PANELS OF EITHER OF THE THREE. SUPPOSE IN A FINE MORNING, I ENTER YOUR OFFICE, WHILE YOU ARE BUSY IN YOUR OWN WORK AND SHOW YOU TWO PAINTED PANELS FROM A CERTAIN DISTANCE AND ASK YOU ?PLEASE TELL ME SIR, WHICH ONE IS MORE GLOSSY?? I AM SURE YOU WILL INDICATE THE PANEL SHINNING MORE, AS THE GLOSSIER ONE. THIS CONCEPT ITSELF IS WRONG. YOUR INDICATED PANEL MIGHT BE HIGHER IN ? RELATIVE BRIGHTNESS ? THAN THE OTHER BUT NOTHING CAN BE SAID ABOUT THE GLOSS VALUE UNLESS AND UNTIL YOU PUT THEM UNDER A GLOSSMETER AND MEASURE THEIR VALUES. RELATIVE BRIGHTNESS IS A MEASURE OF THE AVERAGE INTENSITY OF LIGHT SCATTERED RANDOMLY FROM A SURFACE OVER ALL THE POSSIBLE DIRECTIONS AND WHICH ULTIMATELY REACH TO OUR EYES. ON THE CONTRARY, GLOSS IS DIRECTLY RELATED TO THE INTENSITY OF LIGHT REFLECTED SPECULARLY (ANGLE OF INCIDENCE = ANGLE OF REFLECTION) FROM A SURFACE. IN THE PRESENCE OF SURFACE MICROHETEROGENEITIES, THE EXTENT OF SPECULAR REFLECTION IS BEING HINDERED AND THE GLOSS VALUE DIMINISHES. IN THE PRESENCE OF SUCH SURFACE IRREGULARITIES, THE OCCURRENCE OF RANDOM SCATTERING OF LIGHT IS FACILATED MORE LEADING TO AN ENHANCEMENT OF THE RELATIVE BRIGHTNESS PARAMETER OF A SURFACE. HOWEVER, IN THE EVENT OF THE SIZES OF THE MICROHETEROGENEOUS DOMAINS OF A SURFACE EXCEEDING A CERTAIN CRITICAL VALUE, A PORTION OF THE SCATTERED LIGHT AT THE SURFACE IS BEING BLOCKED BY THE DOMAIN WALLS AND CANNOT REACH TO THE EYES AND THE SURFACE LOOK LESS BRIGHT TO OUR EYES.A GLOSSMETER GIVES THE GLOSS VALUE IN REFERENCE TO TWO STANDARDS TILES, viz, 0 AND 100. A BLACK MATT SURFACE IS TAKEN AS ZERO WHILE A POLISHED SURFACE OF A GLASS IS TAKEN AS HUNDRED. THE PHOTO CELL OF A GLOSSMETER MEASURES THE INTENSITY OF LIGHT (SAY, X) REFLECTED FROM A SURFACE AND COMPARES WITH THE INTENSITY OF 100% STANDARD (SAY, P) AND EXPRESSES ITS GLOSS VALUE AS, X/ P *100 FRIENDS, I CAN FEEL VERY WELL THE QUESTION PEEPING IN YOUR MIND AT THE VERY PRESENT MOMENT, WHY GLOSS IS SO IMPORTANT? YES FRIENDS, IT IS INDEED VERY SIGNIFICANT ESPECIALLY IN REGARD TO THE IMAGE CLARITY OF A SURFACE.TODAYS AUTOMOTIVE FINISH PAINTS ARE REQUIRED TO BE LIKE A MIRROR (HIGH IMAGE CLARITY OR DISTINCTION) SUCH THAT A PERSON CAN COMB HIS HAIR STANDING INFRONT OF THE AUTOMOBILE. A PAINT SURFACE TO BE LIKE A MIRROR, NOT ONLY THE REFLECTANCE SHOULD BE HIGH BUT ALSO THE SURFACE HAS TO BE VERY SMOOTH AS WELL. YOU CAN RECALL NOW, THE SURFACE MICROHETEROGENEITY REDUCES GLOSS AND HENCE GLOSS IS AN INDIRECT MEASURE OF THE IMAGE DISTINCTION OF A SURFACE. HIGHER THE GLOSS, HIGHER WOULD BE THE IMAGE CLARITY. FRIENDS, TO THE END, I WILL BE GOING TO THE FURTHER DEPTH OF THE SUBJECT. GLOSS OR SPECULAR REFLECTANCE IS A COMBINATION OF TWO FACTORS AS UNDERGLOSS IS DIRECTLY PROPORTIONAL TO (LIGHT SLIPPING PAST FACTOR -LIGHT BLOCKING FACTOR)WHENEVER A LIGHT RAY FALLS ON A SURFACE A PART IS SLIP- PAST (WHICH CAN REACH OUR EYES), WHILE A PART IS BEING BLOCKED BY THE SURFACE AND CANNOT REACH TO THE EYES. AT ZERO ANGLE OF INCIDENCE, BLOCKING IS HUNDRED PERCENT WHILE THE SLIP PAST IS ALMOST NIL SO GLOSS WOULD ATTAIN A ZERO VALUE. AT AN ANGLE OF INCIDENCE 90°, THE REVERSE IS TRUE AND THE GLOSS VALUE WOULD BE NEARLY 100%. IN BETWEEN THE TWO EXTREMES AT 45 DEG INCIDENCE, BOTH THE ABOVE FACTORS COUNTERBALANCES EACH OTHER SUCH THAT AT THIS INCIDENCE THE GLOSS VALUE IS FAIRLY HIGH. NOW UPON INCREASING THE ANGLE OF INCIDENCE FROM 45 DEG.TO THE HIGHER ONES, THE GLOSS VALUE DIMINISHES UPTO 60 DEG.OWING TO THE OCCURRENCE OF GREATER BLOCKAGE IN COMPARISON TO THE OCCURRENCE OF SLIPPING PAST OF LIGHT. ONCE THE INCIDENCE GOES ABOVE 60 DEG., THE BLOCKING FACTOR REDUCES TO A LARGE EXTENT AND THE GLOSS VALUE AGAIN RISES.COND. PAGE 2PAGE 2NOW UPON DECREASING THE ANGLE FROM 45 TO THE LOWER VALUES, THE GLOSS MONOTONICALLY DECREASES ON GROUND OF THE BLOCKAGE BECOMING MORE AND MORE IN MAGNITUDE. IT CAN NOW BE SUMMARISED THAT:GLOSS AT 85 DEG > GLOSS AT 60 DEG. GLOSS AT 20DEG.A MATT OR SEMIGLOSSY FINISH WILL VIRTUALLY SHOW VERY LOW GLOSS VALUE AT 20, 45 OR 60° AND TO GET A PERCEPTIBLE GLOSS ONE GO SHOULD TO THE 85 DEG HEAD. FOR ANY TWO HIGH GLOSS SURFACES IF THE GLOSSES ARE MEASURED AT 45 OR 60°, BOTH WILL YIELD HIGH VALUES UNDER SUCH SITUATION, ONE SHOULD GO FOR 20° GLOSS. SINCE AT THIS ANGLE THE GLOSS WILL SOLELY DEPEND ON THE SURFACE SMOOTHNESS AND AS A RESULT A VERY SHARP DISCRIMINATION CAN BE MADE BETWEEN TWO HIGHLY GLOSS SURFACES. FOR SEMIGLOOSY TO MODERATE GLOSSY SUEFACES MEASUREMENT AT 45 AND 60 DEG. HEADS USUALLY SERVE THE PURPOSES.MILLIONS OF PEOPLE EVERYDAY CONFUSE BETWEEN GLOSS, RELATIVE BRIGHTNESS AND IMAGE CLARITY BUT FRIENDS, TO THE END, I FEEL CONFIDENTLY, YOU PEOPLE, AFTER READING THIS ARTICLE, WILL NEVER CONFUSE.

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