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This 0 page Class Notes was uploaded by Chloe Reilly on Monday November 2, 2015. The Class Notes belongs to ME 8883 at Georgia Institute of Technology - Main Campus taught by Staff in Fall. Since its upload, it has received 10 views. For similar materials see /class/234250/me-8883-georgia-institute-of-technology-main-campus in Mechanical Engineering at Georgia Institute of Technology - Main Campus.
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Date Created: 11/02/15
ME 8883 Paper Physical Property Measurements Instructor Dr Roman E Popil PhD 1984 Plasma Physics UBC office 333 ph 404 894 9722 email romanpopilipstedu Senior Research Scientist Institute of Paper Science and Technology Tuesdays and Thursdays 135 to 255 pm ME 8883 1 intro sampling moisture basis weight Paper Property Measurements Principles of measurements significance to paper quality issues Handson demonstrations in the lab pragmatics of instrument maintenance and calibration emphasis will be on standard Tappi methods some discussion of specialized methods How to use physical property measurements to solve paper quality and manufacturing problems ME 8883 1 intro sampling moisture basis weight Paper is a complex orthotropic anisototropic and hygroscopic mess no surprise Recent laser confocal shot of a softwood lab handsheet 40X mag A conglomeration of fibers each fiber is different than the next What does that mean to you Paper is lumpy bumpy fuzzy stuff Be aware that there is a lot of variability in all properties between samples and within a sample all measurements must consist of at 6 or more repeats there a 3 directions to machine made paper MD x 1 11 CD y 2 22 ZD z 3 33 mechanical properties in these three directions are all different paper retains moisture and remembers its moisture history mechanical properties are dependent on paper moisture in a nonlinear fashion l ME 8883 1 intro sampling moisture basis weight Paper Physical Property Measurements Topics basis weight moisture density Caliper hard and soft Tensile strength stretch to break TEA lnstron and LampW methods tear burst ZDT fold zero span tensile Ultrasonic stiffness stiffness orientation plot Hygroexpansivity Roughness air leak and profilometry 3D shadow Moire gloss Formation optical transmission electrography Opacity brightness 10 Color 11 Bending stiffness 2 point LampW Taber and LampW4 point 12 Linerboard Ring crush and STFI 13 Corrugated Board ECT BCT creep Concora crush 14 Water absorption water drop contact angle Cobb VWTTR size tester WNQQPWNT ME 8883 1 intro sampling moisture basis weight Grading 3 lab sessions are in the plan using the techniques demonstrated and learned produce a cohesive set of measurements on a sample set to produce a complete description of paper properties and their interrelationships Final closed book exam check of retention of recollection of the basics ME 8883 1 intro sampling moisture basis weight PAPER STUCTURE Fibers former wood OVERSIMPLIFIED cells typically 1 3 mm log 50 microns wide Paper consists of 50 to 30 air and a network of bonded fibers aligned predominantly along the MD machine direction ME 8883 1 intro sampling moisture basis weight Moisture Hysteresis Curve of Paper Wink from IPST produced a curve of the moisture content of paper versus relative humidity quoted in textbooks going up the curve is not the same as going downquot Paper once wet is never the same again If you put paper in a high humidity environment eg 90RH it will absorb moisture to have a moisture content ie wet dry weightwet weight of 11 take it back down to 50 it will have a moisture content of maybe 9 But if you take paper to 20 RH then up to 50 RH it will likely have a moisture content of 7 RH repeatably Do you know where your sample has been Your sample knows Tappi method 404 condition paper samples at 20 RH for 24 hrs then condition samples for 50 RH for 24 hours prior to any measurements ME 8883 1 intro sampling moisture basis weight Moisture Control in 351 and 352 Adjoining 351 is room 352 this is the dry room maintained at 20 RH and 73 deg C note the circular chart on the wall new samples to be tested stay here on the racks for 24 hours make sure air can get to the surfaces of your samples by hanging them up on the racks after 24 hours in the dry room hang your samples on the racks to condition in 351 lab maintained at 50RH 73 deg C Make sure you have you samples labeled with name phone number and date the racks are for conditioning samples not storage samples left on the racks are periodically discarded Without notice After your samples have finished the conditioning sequence store them in sealed plastic bags the conditions in lab 351 are subject to fluctuation and upsets by outside weather If your samples are ever subjected to humidity above 5 RH they must re conditioned 24 hours at 20 RH followed by 24 hours at 50 RH ME 8883 1 intro sampling moisture basis weight Tappi test methods most of the testing methods we will discuss are industry standardized methods decided and reviewed by Tappi committees that meet at regular Tappi conferences this ensures universal quality standards that characterize paper as a commercial product each method is designated as T 7 letter suffix 400 500 is Paper ands Paperboard testing 800 s are Containerboard tests om designates an official method pm provisional method Let s look at the first one T 400 sp97 Sampling and accepting a single lot of paper paperboard containerboard or related product ME 8883 1 intro sampling moisture basis weight 11 This rnethed describes procedures fer ebtaining a sample fer testing It sheuld be recognizer that in an ideal situation the samples selected sheuld represent a let ef paper er paperboard eentainer beard er related preduet including eeneerted paper preduets all hereafter referred te as paper Heweaer in same situatiens the sample rnap be as small as a single sheet at paper that has been presided tn the laberaterp fer testing and may net represent the let from which it is obtained 31 Lot a quantityr of paper of a single type grade grammage thickness and composition about which it is desired to make a judgment usually as to conformance to speci cation by examining or testing a small fraction called the sample 32 Stampi39e a speci ed number of test units selected according to a prescribed procedure to represent the lot It should also be recognized that in some situations the sample to be tested may consist of a limited quantity or as small as one sheet of paper 33 Test unit an area of paper suf cient to obtain a single adequate set of test results for all the properties to be measured 34 Test specimen a test unit or a portion of a test unit upon which for a speci ed property a single test determination is to be made 35 Test determination l the process of carrying out the series of operations speci ed in the test method whereby one or more readings observations are made on a test specimen and the observations combined to obtain the value of a property of the test specimen or 2 the value obtained by the process 36 Test rank the value obtained for one test unit of the sample by carrying out the complete protocol of the test method the value being as speci ed in the test method either a single test determination or a speci ed combination of a number of test determinations 37 Test strip cross tendons strip continuous strip of paper that represents the width of either a roll or reel as speci ed by the buyerr39seller Machine direction strip continuous strip of paper of a length and machine position to re ect the measurement of interest ME 8883 1 intro sampling moisture basis weight 10 532 39 39 39 39 39 39 A 18 in 5 in ms rm w window Cm the window with its longer side parallel to the machine direction when lhls is known or if not known cut the window at least 450 by 450 mm 18 x 18 in with Paper is highly variable nonuniform how many samples and measurements do you need to take to characterize a paper property 2 Sample cut along the MD MD Paper from mills usually supplied in roll form ME 8883 1 intro sampling moisture basis weigh A sample is associated with a certain grade process parameters each sample will have several specimens or replicates Front or Back or Tending Side Drive Side gm Paper from a paper machine has a variation in the MD and the CD CD variation arises from drying profiles headbox edge flows MD are high frequency variations focs wire marks etc ME 8883 1 intro sampling 12 moisture basis weight A3 Protecfiun Y0 producer The lot will be accepted with a probability afat least 95 if the proportion of die defective items comaine in it does no excee A32 Pratecfiull to Consumer The lot will be rejected with a probability of at least 90 if the proportion of lie defective items comailied in it reaches 16 to 32 in Plan I 19 to 68 in Plan 11 and 37 o 68 in Plan Ill die smaller gure in each case applying to the largest lot size Most measurements are made with several repeats 6 or more on several specimens from a sample ME 8883 1 intro sampling 13 39 t moisture basis weigh T 402 arm93 Standard conditioning and testing atmospheres for paper board pulp handsheets and related products 2 Significance E i The pi iysieal properties of a sanztpie at Stiltt RH depend on whether the santpie was hrought to 50 from higher or lower reliatix e humidities this quothumidity hysteresis effectquot is SESFHZ of the test 1raiue for many physical properties For eaanipie a hysteresis effect of t 5 moisture content it or ESQ1 of the test aaiue of oilquot moisture content is tgrpioai Preconditioning on the dry side within the range specified wiil avoid most of the hysteresis effect and resuit in the moisture content of a given santpie heing est ahiished Witi tit t Elite when the sample is tater conditioned to sass RH and EB39Z39C Conditioning donn to 50 gives most papers a moisture content tierr heartyquot the same as conditioning up to ri e391 2 Both temperature and relative humidity have signitioant effects on the physieai properties of paper and board it 2 For some properties of paper and hoard t e an MD tensiie and CD stretch a change of ti C may have hearty as much effth as a change raf et RH For synthetie fibers and plastic laminates the temperature effect may be It eater than the RH effect ME 8883 1 intro sampling 14 moisture basis weight Samples for mechanical property testing have to placed in a conditioned room 24 hours at 20 RH followed with 24 hours in 50 RH 53 Expose the sample sheets or specimens to the preconditioning atmosphere so that both surfaces of single sheets and exterior surfaces of laminated products or sealed containers are freely exposed This is best achieved by suspending them from overhead or supporting them on a wire grid or rack 54 Precondition the sample sheets or specimens by exposing them as speci ed above 53 to the preconditioning atmosphere Precondition for a minimum of24 it unless a lesser time has been found to give satisfactory results If the sample is to be stored for time after preconditioning store at a temperature below 25 C 77 F and a relative humidtity below 40 but not below 10911 NOTE 4 For preconditioning apparatus of ample capacitr and air Circulation the following preconditioning times have usually been found satisfactory single sheets of paper less than i h linerboard corrugatng medium chipboard boxboard 12 h conugated and solid berboard in sheet form 510 h sealed boxes and shipping containers 1216 h specially treated water vapor resistant papers and boards 24 h and more moisture weight or other moisture dependent property 1 hr for single sheets 5 hr of corrugated board sheets time r ME 8883 1 intro sampling 15 moisture basis weight Condition m le at 20 RH its m will be 4 umsvuu comm 1 Fig 1 The same sample from a humid environment conditioned at 50 RH will have m of 8 2 w so mzmwe Nimmv quot Typical mmsmre sorpnan mum furpmp and pupal ME 8883l intros samplings moisture basis Weight is 7 An example of the effect of moisture Excerpted from Popil and Schaepe August 2005 Tappi Journal Studies at IPST have shown that RC or similarly the short span compression strength STFI dependence on moisture can be described by the empirical relation STFImRCm STFloj RC0189 7009M 3 where M is the percent moisture content by weight of the lmerboard and the 0 subscript denotes the values of RC or STFI for samples equilibrated at 50 RH Tappi Standard testing conditions 26 Exposure to high humidity conditions can increase the moisture content of liner to 11 lowering the strength properties according to Equation 3 and consequently Equation 1 by 30 percent Therefore keeping box components dry as possible is important in maintaining corrugated board strength 26 LehtiST Ketoja JANiskanen KJ Measurement of Paper Rheology at Varied Moisture Conditions 2003 International Paper Physics Conference September 711 2003 Victoria British Columbia 57 63 27 Tappi test method T402 Standard conditioning and testing atmospheres for paper board pulp handsheets and related products ME 8883 1 intro sampling 17 moisture basis weight T 412 elm94 Moisture in pulp paper and paperheard Use a drying oven at 105 deg C dessicator chamber and sample tins 5 For sman specimevis 2 g 21 Weigh the specimen in the tared weighing bottle to the nearest milligram place it in the drying even remeve the stepper and heat for aheut 30 min fer grarmnages greater than 224 ge39ml heat for 1 11 522 Restopper the bottle remove it from the even can te room temperature in a desiccator loosen the stepper momentarily to allow air to enter and reweigh Carry out this weighing step within 3930 min after remnval 0f the battle from the oven to prevent reahseiptien of water vapor by the specimen f Calculate the meisture for each specimen as the percentage less of the Original weight if the specimeIL to the nearest 0 1 t W W5 100 Percent meisture centent 1 J l 1e39l iere W1 initial weight specimen g W3 dry weight specimen g Report as moisture the average ef the values for the twe specimens Any variations from the recommended method sheuld be stated in the report ME 8883 1 intro sampling 18 moisture basis weight Repeatability Within a laboratory DL3595 15 moisture content Reproducibility between laboratories is variable depending on how well the procedure is followered differences as great as 15 moisture content H The precision and accuracy of test results will be affected by a variations in moisture content throughout a reel lb handling and atmospheric exposure and c i the ambient relative humidity of the drying oven A rli erence of up to 03 moisture content in bleached paperboard has been noted between cases where the even has been located in a low relative humidity i less than 1594113 or at standard 50 humidities Where possible it is suggested to locate the oven in the test laboratory environment of 50 RH ME 8883 1 intro sampling 19 moisture basis weight Air tight jar with dessicant on bottom Place sample in air tight sample can ME 8883 1 intro sampling moisture basis weight 1 Place samples inside of oven kept at 105 deg C for two hours 2 Put can covers on using heat resistant gloves 3 Put cans into dessicantjar weigh to 4 places when cooled ME 8883 1 intro sampling 21 moisture basis weight IR methods for moisture 1 31 vs nxm Co lccmg i 39 Ix Mm E 39 39 quot 39 gtkl39 7 I paw II I Timquot r may 39 l I u t v 39 I x L M il39r39lll N In J39 lr39 WP T J 3333 n 141 l 39 539 ll mgr has e l I 39u39d nlri hasquot LiaquotVI 113 39 I 39r 53 l1 rerz me 54in 1quot quot39 f 7ii l 3772 7 anuc l 39IIJ i H IE 23 22 2a 5 39 39aa e39uigll39 irmru rim1m 5f Using a filter wheel or several detectors a difference method may be used to determine the moisture content in paper calibration is required for different grades due to different optical effects Microwave aborption is also used in some sensors more applicable to thick substrates ME 8883 1 intro sampling 22 moisture basis weight
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