1、Designation: D 7310 07Standard Guide forDefect Detection and Rating of Plastic Films Using OpticalSensors1This standard is issued under the fixed designation D 7310; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide is intended to provide suggested approachesand criteria for the observation of defects in various types ofplast
3、ic film, by means of an optical scanning system.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of reg
4、ulatory limitations prior to use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to Plastics3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 defectfor the purpose of this guide, any entity in thefilm
5、that is large enough to be detected by an optical sensor andis either polymeric in nature or caused by degradation, externalcontamination, undispersed additives or pigments, or similarsources.4. Significance and Use4.1 Defects in film are not acceptable to the end-user asthere is a reduction in the
6、fitness-for-use, in many applications.This document is intended to be a guide to assist users in theinspection and observation of defects.4.2 This guide is applicable in a laboratory environment asa quality control or as a research tool. It is also appropriate foruse in any commercial process used t
7、o produce film includingcalendering and solvent casting.4.3 This guide is also suitable for use as an evaluation orscreening tool for materials intended to be used in otherprocesses where defects of this nature are also critical, such asfiber spinning and nonwovens.4.4 The individual user must agree
8、 upon the relationshipbetween the criteria and acceptance for fitness-for-use and theobserved defects, as it varies by polymer and application. Thisis attained by the collection of data over a time-period toestablish acceptable control limits.5. Apparatus5.1 ExtruderAdevice for melting polymer that
9、produces aflat or blown (tubular) film, with sizes varying from lab-scaleto production-scale.NOTE 2Although this technique is utilized for many different pro-cesses used for producing films, the extrusion systems described in thefollowing section represent the more prevalent process used. This is no
10、t toimply that the guidance provided for utilizing this type of instrumentationcannot be applied to other processes or other applications.5.1.1 Flat Film ExtrusionAn extrusion system that pro-duces a flat film that is quenched immediately after extrusionby means of one or more cooling devices such a
11、s an air knife,chill roll or water bath.5.1.2 Blown or tubular extrusion An extrusion system thatproduces a tubular “bubble” of film from a circular die,equipped with an air-ring to cool the polymer.5.2 Screen PackAlthough commonly used in commercialor semi-commercial environments, screen packs are
12、not gen-erally used in laboratory units intended for research or qualityfunctions.5.3 Defect Detection SystemAn optical scanning systemwith a light source, an analog or digital camera, and an imageprocessor. The optical characteristics of the camera are criticalfor detecting small (30 m) defects and
13、 it is important that theinstrument manufacturer be informed of the detection needswhen choosing a system.NOTE 3Other types of detection systems than the ones described inthis guide are available, but are outside the scope of the guide, and are notdefined.5.3.1 Transmission Mode (Transparent or Tran
14、slucent FilmConfiguration)The camera is located directly across from thelight source with the film passing between them. With thissystem, the film is illuminated and the camera captures imagesof the defects and sends them automatically to the image1This guide is under the jurisdiction of ASTM Commit
15、tee D20 on Plastics andis the direct responsibility of Subcommittee D20.19 on Film and Sheeting.Current edition approved Sept. 1, 2007. Published September 2007.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book o
16、f ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.processor, which measures the size and frequency of thedefects. Fig. 1 is a basic out
17、line of this setup.5.3.2 Reflection Mode (Opaque Film Configuration)Thelight source and camera are both located above and at equalangles, typically 45, to the film. This allows the camera todetect the defect images by reflectance off the film, and theimages are sent to the processor that measures th
18、e size andfrequency of the defects. Fig. 2 depicts a basic outline of thistype of setup.6. Procedure6.1 Extrusion6.1.1 Laboratory EnvironmentLaboratory determinationsare much more controlled than determinations conductedonline in production environments. Their applicability is moresuited to research
19、 and quality functions, and consequently, therequirements and control levels are more stringent.6.1.1.1 Extruder ConditionsIn order to count defects inextruded film, the proper temperatures, especially on the diezone, must have been reached. In general, it is best for the setpoint temperature to be
20、at or above the melt point of thepolymer, but not enough above it to cause degradation of thematerial.NOTE 4Specific extruder conditions and preconditioning of material,such as drying, if required, are determined by the system used and thematerial being evaluated, in conjunction with guidance provid
21、ed by theinstrument manufacturer, material supplier, or material specificationdetermine. In addition, the extruder screw speed shall be set such that theresidence time of the polymer is adequate to entirely melt and mix thepolymer, but not long enough to cause degradation (less than 10 minutesis bes
22、t to prevent formation of defects in the extruder).NOTE 5One method for determining residence time is to introduce adifferent pigmented polymer into the extruder and measuring the timerequired for the pigment to travel from the throat, or point of introduction,to the final product.The relation of th
23、e screw speed (extruder output) and take-upspeed shall be set to produce film of suitable thickness tomeasure defects. After these conditions are determined, thesame conditions must be used consistently to ensure repeatableresults for a given type and grade of material. A nitrogenblanket is recommen
24、ded on the feed throat to eliminate oxygenin the extruder.6.1.1.2 PurgingThe extruder shall be cleaned thoroughlyprior to the introduction of the material to be evaluated. This isaccomplished by introducing some form of concentrate addi-tive mixture, such as an antioxidant, prior to introducing thes
25、ample, or simply running a clean, highly stable, compatiblematerial through the extruder until the film appears clear orwhen the defect count, as measured by the optical monitoringsystem, has stabilized. After introducing the material to beevaluated into the extruder, allow enough time for the prece
26、d-ing material to completely purge. If studies of similar materialsare being performed, the purge time is established prior tosubsequent evaluations. (See Appendix X1 for guidelines onthe use of a Control Resin.)NOTE 6The need for adequate equilibration cannot be overstressed.Not only must care be t
27、aken to provide adequate time for the system tostabilize after purging, but also to allow adequate monitoring time in caseswhere intermittent defect flurries occur in a stable system due tonon-uniformity of the sample itself (see Appendix X2).6.1.2 Production (Commercial) Environment6.1.2.1 The gene
28、ral purpose of optical sensors used in aproduction environment is continual monitoring, both for theconsistency of the product and to detect any disturbances in thesystems or processes that introduce an unacceptable level ofdefects.6.1.2.2 Extruder ConditionsWhen monitoring film pro-duced on a comme
29、rcial scale, the extruder conditions shall bedetermined by the constraints of the production requirements,that is, conditions are not changed from the normal operatingconditions for the purpose of defect detection. When the intentis to evaluate the film for defects, it is important to haveprocesses
30、in place to ensure that proper operating guidelinesare followed. Variables such as temperature, film gauge, etc.must be taken into account to achieve repeatable results.6.1.2.3 PurgingIt is normally not possible to purge pro-duction extrusion equipment with any cleaning or referencematerial. In this
31、 case, the system must be set up to producecommercially acceptable product and the monitoring systemessentially serves to track deviations from the acceptablelevels. In this case, the acceptable levels shall be determined bythe accepted fitness for use set by the application or byagreement between s
32、upplier and user.FIG. 1 Transmission Mode (Clear/Translucent Film)D7310072NOTE 7It is also possible to monitor commercial quality by taking asample of film and evaluating it using an offline system. However, this willnot provide continuous monitoring nor will it necessarily be representativeof the e
33、ntire commercial production quantity.6.2 Evaluation of DefectsNOTE 8General best practice guidelines and possible sources of testerror are found in Appendix X1.6.2.1 For laboratory evaluations, produce a sufficient quan-tity of film to ensure the defect frequency has stabilized.NOTE 9It is critical
34、that the area not be disturbed during theevaluation, as dust and other foreign particulate matter are liable to causeerroneous measurements. Cover the extruder hopper during the evaluationto prevent the inclusion of any foreign materials.6.2.2 Monitor the film with the optical scanning system.6.2.3
35、Observations6.2.3.1 Record the result of the measurement of defects theinspection system detects.6.2.3.2 Categorize and count the defects according to sizeclasses or other specifications as defined by internal standardsor agreement between supplier and user.(a) Typical units for reporting include de
36、fects per squaremeter (or square foot), defect area in parts per million (PPMdefect area = total defect area/total area measured), or anyother method as defined by internal standards or agreementbetween supplier and user.NOTE 10Examples of data presentation for film defect detection andmonitoring ar
37、e shown in Appendix X3. The examples of the reports arefrom the same optical scanner and are provided as a means of demon-strating the type of information available.7. Report7.1 Complete sample identification7.2 Date of sample testing7.3 Method of Evaluation7.3.1 Equipment Type (Lab or Production; F
38、lat or Blown;etc.)7.3.2 Scanner Mode (Transmission or Reflection (andangles of camera and light source to the film for reflection)7.4 Film thickness7.5 Area of film inspected7.6 Defect observation and size7.6.1 Method of Observations (measurement), based oninternal requirements, the accepted fitness
39、-for-use set by theapplication, or by agreement between supplier and user.8. Keywords8.1 cast film; defect; extrusion; optical scanner; tubular filmFIG. 2 Mode (Opaque Film)D7310073APPENDIXES(Nonmandatory Information)X1. GENERAL GUIDANCE AND TROUBLESHOOTINGINTRODUCTIONThis appendix is offered to ass
40、ist laboratories in conducting defect detection of plastic films usingoptical sensors. It is an aid used to identify the root-cause of problems caused by equipment,environment, or testing technique, but not intended to be an all-inclusive troubleshooting checklist.Although most of these points apply
41、 to laboratory use, it is feasible to apply some of the principlesto a production environment.X1.1 Control ResinThe use of a control material cannotbe over-emphasized. Best practice includes securing a suffi-cient quantity of material that is used on a regular basis toconfirm the consistency of the
42、system operation. It is alsoimportant that the control resin contain minimal defects inorder to be able to assess the cleanliness of the system. Theobservable measurement obtained using the control resin isalso used to establish control charts, which provide anothertool to assess the consistency of
43、the system. If wide varieties ofmaterials are tested on the same instrument, it is advisable toselect an appropriate range of materials to be used as controls.Control resin baseline values are best established on a cleanextruder and die. If inconsistencies are observed that are notassignable to any
44、identified cause, inspection and cleaning ofthe screw and die is recommended.X1.2 Purge ResinA suitable purge resin must be selectedbased on its ability to properly clear the system of any residualmaterial but still be able to be purged, in turn, by thematerial(s) being tested. The use of special ad
45、ditives orcompounds is effective but care must be taken to ensure theyare properly cleaned out of the system. If wide varieties ofmaterials are tested on the same instrument, a range of differentpurge materials is normally required.X1.3 Purging ProcedureThe purge resin must be pro-cessed until all r
46、emnants of the preceding material have beenremoved. There are a number of methods used to determinewhen purging is adequate including:X1.3.1 Visual observation for changes in clarity or colorX1.3.2 Stabilization of extrusion pressures or motor loads ifchanges occur after adding the purge materialX1.
47、3.3 Use of a color tracerX1.4 Extruder and Die Temperature ControllersProperand consistent control of processing temperatures is critical.Under-heating results in poor or nonhomogeneous melting andmixing while overheating results in degradation.X1.5 Operating ConditionsStandard operating condi-tions
48、 must be established for each category or type of resin.These conditions include:X1.5.1 Temperature settings (extruder, die, and rolls),X1.5.2 Film gauge,X1.5.3 Output rate,X1.5.4 Extruder and line speed (drawdown),X1.5.5 Web tension,X1.5.6 Scan duration,X1.5.7 Cooling (Air ring or knife, chiller, e
49、tc.).X1.6 Shutdown ProcedurePurging with a well-stabilizedmaterial prior to shutdown minimizes degradation of thematerial. It is advisable to slowly ramp down the temperaturesprior to actual shutdown. Use a separate shut down resin afterpurging to allow a gradual ramp down of extrusion tempera-tures to an appropriate temperature before shutdown is helpful.Monitor torque and pressures so that no equipment damageoccurs while the extrusion temperatures are decreasing.X1.7 Startup ProcedureThe initial warm-up temperaturesettings must below the operating se
