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What is the acceptable level of acetaldehyde in pet preform. If it is more than 8 ppm what happened for that preform.
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Why does AA measurement of the same sample at different times yield different AA readings? How can AA measurement be standardised?What are the causes of differences?
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For drying PET:
1) 8 hrs residence time at hopper is preferred (use a range from 5 to 9 hrs). 1 cfm/lb/hr airflow rate, -40°C dew point, 165°C process air temperature.
2) Temperature range from 140°C to 185°C maybe used. It depends on the residence time. Remember 160°C is a requirement at the extruder feed throat.
Cheers..!!!!
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To whom it may concern
I want to know the best tempreture and time for pet drying ?
Best Regards
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Several resons maybe involved:
1. cost -- how much you need to pay for transportation, washing, to remove label and glue on bottles?
2. outlook -- outer finish of PET bottle will not be shining anymore mostly after first use.
Any more reasons?
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Is it true that pet bottles packed with drinking water must be used only once? what happens on repeated use of the same bottle for filling waterin the long run?
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Acetaldehyde is a simple, naturally occurring, organic chemical occurring in many ripe fruits eg., apples, grapes and citrus fruits (up to 230 ppm). It is produced during the fermentation of sugar to alcohol, and is a natural constituent of butter, olives, frozen vegetables and cheese. It forms in wine and other alcoholic beverages after exposure to air (up 140 ppm). It even occurs as an intermediate in the decomposition of sugars in the body and hence can be found in traces in blood. Acetaldehyde or AA is listed as an approved additive and is used to enhance citrus flavours helping to create natural, fruity tastes and fragrances. As a flavour ingredient it can be found in ice creams, sweets, baked goods, chocolates, rum and wine. Acetaldehyde is, therefore, a harmless chemical in these circumstances but it does have a flavour and, in its pure state, a sharp, penetrating fruity aroma.
It is formed during thermal degradation of PET and only when the polymer is in the molten state. However, it is very important to control the level of acetaldehyde because of its ability to change the taste, and flavour, of foods packaged in PET. Typical concentrations of acetaldehyde in PET used for beverage packaging would certainly be less than 10ppm and probably closer to 4-5 ppm. At these concentrations it has no effect on the taste of foods, or beverages, and is certainly not a toxicity hazard.
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Acetaldehyde (AA) CH3CHO
Basic function of:
PET MELT TEMPERATURE
PET RESIDENCE TIME IN MELT
For PET injection molding minimize both for minimize AA in PREFORM!
DEGRADITION REACTION OF PET
NATURALLY OCCURING IN FRUIT
HRAPPED?IN PREFORM AFTER MOLDING
MIGRATES SLOWLY FROM THE PREFORM
MIGRATES MORE EASILY FROM THE BOTTLE
SIGNIFICANT MIGRATION INTO THE BEVERAGE COULD CAUSE A TASTE CHANGE Q.C.
TESTING LIMITS ESTABILISHED BY THE MAJOR BEVERAGE COMPANIES
Q.C. Testing done by headspace gas chromatography of blown bottle (24-hour headspace test) HSAA
Joseph S. Lakatosh, PhD.
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Acetaldehyde, a degradation product created during melt processing of PET, is no longer being created once the part is molded. (It is only created while the PET is molten.) It therefore dissipates from the preform (if made via the 2 stage process) or bottle (if made on via single stage process)dependent on such things as storage temerature, storage time, amount of acetaldehyde initially present, part thickness, and part surface area. I have found that, for bottles stored at room temperature, the amount of acetaldehyde asymptotically approaches zero after about 30 days.
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Why does AA measurement of the same sample at different times yield different AA readings? How can AA measurement be standardised?What are the causes of differences?
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