newsprint paper testing

5/14/2018 Newsprint Paper Testing - slidepdf.com

http://slidepdf.com/reader/full/newsprint-paper-testing 1/19

NEWSPRINT PAPER

TESTINGINSTRUMENTS



PROPERTIES OF NEWSPRINT

BASIC CHARACTERISTICS

STRUCTURAL CHARACTERISTICS

OPTICAL CHARACTERISTICS

MECHANICAL CHARACTERISTICS



BASIC CHARACTERISTICS

Grammage

Moisture content



Grammage Tester

GRAMMAGE : Mass of the paperper unit surface area of the sheet-

mass/area. The weight or substance

per unit area is obviously

fundamental in paper and paper board

products. The Basis weight of paper is

the weight per unit area. This can beexpressed as the weight in grams per

square meter (GSM or g/M2).

Digital GSM tester is an instrument

that is used to measure the GSM of

the sample. The sample to be measure

is cut in the standard size (20*25cm)or (25*40cm) and place in the hanger

of that instrument. The reading is

shown in digitized form.

Measurement Limit:- 0-200gm



Moisture tester

Firstly Weighing tester is used to determine the weightof the sample. Range of weighing tester is 0-210gm. Tocalculate weight of a paper, we place the folded paperon the weighing tester. The reading comes on the

screen of the meter; the reading comes in the gram. Then calculate moisture content by placing the paper in

microwave oven for 5min.Again measure the weight. Bysubtracting the weight of these two reading, we obtain

the total amount of moisture present. Now we cancalculate the % of moisture present in the paper.




Sheet thickness

Surface roughness & smoothness

Porosity, air permeability




Sheet thickness is the distance betweentwo parallel plates between which thesheet is subjected to a standardizedpressure. Thickness or Caliper of paperis measured with a micrometer Givingan even pressure of 98.07kPa(1kg./Cm2) over the whole surface area of

its pressure foot.

Caliper is a critical measurement ofuniformity Variations in caliper, canaffect several basic properties includingstrength, optical and roll quality.

Measurement limit:-0-5.494 m



Smoothness is measured as how much air is passing away from

the paper when smoothness head is placed on the paper. First of

all smoothness is set to zero by placing the head on glass

because glass is the smoothest material .The air comes from the

device 'Head’. Air is supply to the head through pipe. After the

reading set to zero head is placed on the paper. As much as the

air passes away from paper, more will be the reading but less

will be the smoothness.Units:-The recommended unit is the bendtsen roughness

number, i.e. the number of milliliters of air escaping per

sec(ml/sec) with an air supply of 1.471 Kpa.

Measurement limit:- 0-1500 ml/sec

SURFACE ROUGHNESS&

SMOOTHNESS TESTER



Smoothness tester



Porosity, air permeability

The term porosity is used to describe the combined volumeof the pores, capillaries and other voids between the fillersand filler materials in the newsprint sheet. Since the porosityof paper is not a directly measurable quantity, the airpermeability or permeance is used to provide a particular

measure of thee porosity and is defined as the mean flow of air through a specified surface area of the paper with aconstant and specified pressure difference between the twosides of the sheet.

Porosity tester is the instrument used to check out the

porosity of a sample. It is based on principle of air pressure.The amount of the air passes through the paper determinesthe porosity of that paper. More the porosity of paper morewill be air pass through it and more will be the reading.Porosity is measured in ml/sec.

Range of this tester is 0-3000 ml/sec. It is a Bendsten typetester.



Porosity tester



OPTICAL CHARACTERISTICS

Brightness

Gloss

Opacity



Brightness The brightness is a measure of the ability of the sheet to reflect

diffuse light in the blue region of the visible light spectrum. It is

defined as the ratio of the light which is reflected by a pad of thenewsprint, thick enough to be totally opaque, to the light which isreflected by a perfect reflecting diffuser under the same conditions,both reflected lights being measured at an effective wavelength of 457nm. To obtain accurate reading of brightness of paper, we place a

black tile on the photo volt search meter for half an hour, after switchon the brightness tester. This is done to heat up the lamp and aftersometime the reading will set to zero.

After black tile, pure white tile is placed over it and its reading set to86%. To measure brightness, we fold the paper two times and placeover the photo volt search meter, then place white tile over it and weget reading in tester. The reading comes in percentage.

units: Brightness is a dimensionless quantity to be expressed inpercent (%) units.



Brightness

Percentage reflectance at a

wavelength of 457nm.

Amount of light reflectedfrom pad of paper/amount

of light reflected from

MgO standard.

Photo

detectorsource

457nm

filter



OPACITY The opacity is a measure of the ability

of a sheet not to transmit light. It is

calculated as the ratio between theluminous reflectance factor of a single

sheet with a black background,

measured through a green filter with an

effective wavelength of 557nm.

To measure opacity, we fold the papertwo times and place over the photo volt

search meter, then place white tile over

it and set tits value to 100. Then

remove the white tile and unfold the

paper and place the black tile over it.The tester shows the reading in

percentage.

The opacity is a dimensionless quantity

to be expressed in percent(%) units.



MECHANICALCHARACTERISTICS

Tensile strength and elongation



Tensile strength / elongation

The tensile strength is defined as the maximum tensile force perunit area per unit width that a test piece of paper will stand beforebreaking in a test.

The Elongation is the ratio of the increase in length of a test pieceof paper at the moment of the maximum tensile force during atensile test, to its length before the test. Elongation is the amount of distortion which paper undergoes under tensile stress. Stretch / elongation is usually expressed, as percent stretch to rupture.

UNITS :

In SI-units, the preferred unit for tensile strength is kN/m. Theelongation is a dimensionless quantity to be expressed as apercentage (%) of the original test span.



Tensile strength



THANK YOU

newsprint paper testing

Documents