ASTM_D_2342_-_68_1972_scan.pdf

AMERICAN NATIONAL ANSI/ASTM D 2342-68(Reapproved 1972)STANDARD Standard Test Method for LOT-TO-LOT STABILIZATION UNIFORMITY OF PROPYLENE PLASTICS1 This Standard_ is issued under the_ fixed designation D 2342;the number immediately following the designation indicates the year of ongtnal adoption or,tn the case of rev1s1on,the year of last revision.A number in parentheses indicates the year of last reapproval.I.Scope I.I This method covers two procedures for determining the stability of propylene plastics when exposed to air in the molten state for a relatively brief period of time:I.1.1 Procedure A-without the presence of copper.1.1.2 Procedure B-with the presence of copper.NOTE I-The values stated in SI units are to be regarded as the standard.2.Summary of Method 2.1 Plastic pellets are exposed in aluminum or copper dishes in a circulating-air oven at 185 C for definite time periods.Thermal oxi-dative stability under these conditions is de-termined visually by comparing the cooled disk of heated plastic with a standard or by measuring any change in its flow rate by ASTM Method D 1238,Measuring Flow Rates of Thermoplastics by Extrusion Plas-tometer.3.Significance 3.1 These procedures are intended primar-ily as a means for rapid quality control.They serve to indicate the uniformity of the thermal oxidative stability of a material as produced from lot-to-lot in a particular composition by a single manufacturer.3.2 The test can detect differences among materials having different levels and types of stabilizers.Procedure A is applicable to all propylene plastics.The use of Procedure B is generally limited to materials that are specifi-cally designed for applications in which there is direct contact of the plastic with copper or its alloys.3.3 Due to the complexities of polymer oxidative degradation and its retardation and their dependence on such factors as tempera-ture and time,the data obtained by these pro-cedures for materials of various polymer and stabilization types may not correlate with behavior under actual use conditions.There-fore,these procedures are not recommended for rating or qualifying such materials in the absence of other long-term aging information.4.Apparatus 4.1 Oven-Air-circulating oven capable of maintaining a uniform temperature and an air flow of 75 to 140 m/min(approximately 250 to 450 fp.m)measured at the inlet side.A con-venient method of checking uniformity of oven exposure conditions consists of filling the oven shelf to be used with the aluminum dishes described in 4.2,after charging each with 15 g of a general-purpose(moderately stabilized)polypropylene.Heat for 16 h at 185 2 C.Remove the dishes,cool,and examine.The polypropylene in each of the dishes should be similar in color.Variation in polypropylene color between dishes indicates nonuniformity of oven temperature or air flow,or both;if variation occurs,the oven is.This method is under the jurisdiction of ASTM Com-mittee D-20 on Plastics and is the direct responsibility Of Subcommittee D-20.12 on Olefin Plastics.Current edition effective Jan.10,1968.Originally issued 195.Replaces D 2342-65 T.Annual Book of ASTM Standards,Part 35.NOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest information.unsatisfactory and must not be used.Non 2-A Freas oven,Model 625,gives satis-factory results when used with the air intake and exhaust vents wide open and the air flow dial set at the maximum air flow.4.2 Dishes-Aluminum dishes and copper dishes,each approximately 0.14 mm(0.0055 in.)thick,70 mm(2.76 in.)in diameter,and 17 mm(0.67 in.)deep.Non 3-Satisfactory aluminum dishes are flat bottom aluminum foil dishes used for milk analysis,made from aluminum alloy I 145-O.At present there is no commercial source for similar copper dishes,but for the purpose of this test these may be easily fabricated by hand or stamping-tool from annealed ETP copper sheet(ASTM Specification B 152,for Copper Sheet,Strip,Plate,and Rolled Bar).4.3 Extrusion Plastometer-Apparatus and accessories as specified in ASTM Method D 1238.5.Test Specimen 5.1 The test specimen shall be in the form of pellets or granules as manufactured for molding or extrusion use.6.Conditioning 6.1 The specimens shall be tested in the as-received condition unless otherwise specified.7.Procedure A-Aluminum Dish Test 7.1 Set the oven temperature at 185 2 C and regulate the air flow to be in the range from 75 to 140 m/min(approximately 250 to 450 fpm).7.2 Clean the aluminum dishes before use with a I+l mixture of acetone and toluene.It is necessary for the bottoms of the dishes to be flat.Discard any dishes that are not satis-factory or reparable.7.3 Place 3.5 0.l g of the sample into each of two aluminum dishes.Spread the pel-lets to a uniform depth in the dish and take precautions to avoid any disturbance of the pellets when transferring the dishes to the oven.7.4 Place the specimen dishes onto th