ASTM D7444-18
(Practice)Standard Practice for Heat and Humidity Aging of Oxidatively Degradable Plastics
Standard Practice for Heat and Humidity Aging of Oxidatively Degradable Plastics
SIGNIFICANCE AND USE
4.1 Since the correlation between the conditions specified in this practice and actual disposal environments (for example, composting, soil or landfill) has not been determined or established, the test results are to be used only for comparative and ranking purposes in the laboratory. No extrapolation to real world disposal expectations or predictions are to be made from results obtained by this procedure. Real world evaluations and correlations are needed for such claims.
4.2 Degradable plastics exposed to heat and humidity are subject to many types of physical and chemical changes. The severity of the exposures in both time, temperature and humidity level, determines the extent and type of change that occurs. For example, short exposure times at elevated temperatures generally serve to shorten the induction period of oxidatively degradable plastics during which the depletion of antioxidants and stabilizers occurs. Physical properties, such as tensile and impact strength and elongation and modulus, sometimes change during this induction period; however, these changes are generally not due to molecular-weight degradation, but are merely a temperature-dependent response, such as increased crystallinity or loss of volatile material, or both. The effects of humidity are less well understood and are more difficult to predict and depend on the degradable plastics characteristics such as hydrophilicity, polarity and composition.
4.3 Generally, short exposures at elevated temperatures drive out volatiles such as moisture, solvents, or plasticizers; relieve molding stresses; advance the cure of thermosets; increase crystallinity; and cause some change in color of the plastic or coloring agent, or both. Normally, additional shrinkage is expected with a loss of volatiles or advance in polymerization.
4.4 Some plastic materials such as PVC become brittle due to loss of plasticizers or to molecular breakdown of the polymer. Polypropylene and its copolymers tend to beco...
SCOPE
1.1 This practice indicates how to test the oxidative degradation characteristics of plastics that degrade in the environment under atmospheric pressure and thermal and humidity simulations, only, in the absence of any selected disposal environment such as soil, landfill, or compost. This practice does not by any extension or extrapolation of data or results generated indicate that such plastics are suitable for or will degrade on disposal in these said environments. It is particularly noted that in real world environments such as soil, compost and landfill oxidations, if they occur, will predominantly be under conditions where other interfering ingredients are present and, in the case of landfill, at sub-atmospheric oxygen concentrations. This practice, therefore, can only result in a relative ordering of the potential for oxidation of plastic materials under the conditions tested, which are not always reflective of their behavior in a particular real world disposal systems. Prediction of the oxidation of a plastic under real world disposal conditions is an essential further testing in appropriate methodologies, such as Test Method D5338 for composting. No claims can be made for real world behavior based on this practice.
1.2 This practice is only intended to define the exposure conditions of plastics at various temperatures in air at atmospheric pressure under controlled humidity levels for extended periods of time. The humidity levels and temperature ranges are selected to be within the variable recorded seasonal ranges (upper and lower levels) generally observed in disposal sites where such plastics are discarded. For example: soil (15 to 40 percent moisture); landfill (35 to 60 percent moisture), and compost (45 to 70 percent moisture). It is optional to expose the plastic at zero humidity, if comparison with specified humidity ranges is of interest. Only the procedures for heat and humidity exposures are specifi...
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Designation: D7444 − 18
Standard Practice for
Heat and Humidity Aging of Oxidatively Degradable
1
Plastics
This standard is issued under the fixed designation D7444; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* ity exposure effects. The effect of heat and humidity on any
particular property is determined by selection of the appropri-
1.1 This practice indicates how to test the oxidative degra-
atetestmethodandspecimen;however,itisrecommendedthat
dation characteristics of plastics that degrade in the environ-
Practice D3826 be used to determine the embrittlement
ment under atmospheric pressure and thermal and humidity
endpoint, which is defined as that point in the history of a
simulations, only, in the absence of any selected disposal
material when 75% of the specimens tested have a tensile
environment such as soil, landfill, or compost. This practice
elongation at break of 5% or less at an initial strain rate of 0.1
does not by any extension or extrapolation of data or results
mm/mm min.
generated indicate that such plastics are suitable for or will
degrade on disposal in these said environments. It is particu-
1.3 This practice is used to compare the effects of heat and
larly noted that in real world environments such as soil,
humidity at any selected temperature, such as those found in
compost and landfill oxidations, if they occur, will predomi-
the mentioned disposal environments, on the degradation of a
nantly be under conditions where other interfering ingredients
particularplasticbyselectionofanappropriatetestmethodand
are present and, in the case of landfill, at sub-atmospheric
specimen.
oxygenconcentrations.Thispractice,therefore,canonlyresult
1.4 This practice is to be used in order to apply selected
in a relative ordering of the potential for oxidation of plastic
exposure conditions when comparing the thermal-aging char-
materials under the conditions tested, which are not always
acteristics at controlled humidity levels of plastic materials as
reflective of their behavior in a particular real world disposal
measured by the change in some property of interest (that is,
systems. Prediction of the oxidation of a plastic under real
embrittlement by means of loss of elongation, molecular
world disposal conditions is an essential further testing in
weight, disintegration, etc.). It is very similar to Practice
appropriate methodologies, such as Test Method D5338 for
D3045butisintendedforuseinevaluatingplasticsdesignedto
composting. No claims can be made for real world behavior
be oxidized easily after use. The exposure times used for this
based on this practice.
practice will be significantly shorter than those used for
1.2 This practice is only intended to define the exposure
Practice D3045
conditions of plastics at various temperatures in air at atmo-
1.5 The type of oven used can affect the results obtained
spheric pressure under controlled humidity levels for extended
from this practice. The user can use one of two methods for
periods of time. The humidity levels and temperature ranges
oven exposure. Do not mix the results based on one method
are selected to be within the variable recorded seasonal ranges
with those based on the other one.
(upper and lower levels) generally observed in disposal sites
where such plastics are discarded. For example: soil (15 to 40
1.6 Procedure A: Gravity-Convection Oven—
percent moisture); landfill (35 to 60 percent moisture), and
Recommended for film specimens having a nominal thickness
compost (45 to 70 percent moisture). It is optional to expose
not greater than 0.25 mm (0.010 in.).
the plastic at zero humidity, if comparison with specified
1.7 Procedure B: Forced-Ventilation Oven—Recommended
humidityrangesisofinterest.Onlytheproceduresforheatand
for specimens having a nominal thickness greater than 0.25
humidity exposures are specified, not the test method or
mm (0.010 in.).
specimen, necessary for the evaluation of the heat and humid-
1.8 Thispracticerecommendsproceduresforcomparingthe
thermal and humidity aging characteristics of materials at a
1
single temperature under dry or selected humidity conditions.
ThispracticeisunderthejurisdictionofASTMCommitteeD20onPlasticsand
isthedirectresponsibilityofSubcommitteeD20.96onEnvironmentallyDegradable
Recommended procedures for determining the thermal aging
Plastics and Biobased Products.
characteristics of a material at a series of temperatures and
Current edition approved July 1, 2018. Published August 2018. Originally
humidity conditions for the purpose of estimating time to a
approved in 2011. Last previo
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7444 − 11 D7444 − 18
Standard Practice for
Heat and Humidity Aging of Oxidatively Degradable
1
Plastics
This standard is issued under the fixed designation D7444; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Scope*
1.1 This practice indicates how to test the oxidative degradation characteristics of plastics that degrade in the environment under
atmospheric pressure and thermal and humidity simulations, only, in the absence of any selected disposal environment such as soil,
landfill, or compost. This practice does not by any extension or extrapolation of data or results generated indicate that such plastics
are suitable for or will degrade on disposal in these said environments. It is particularly noted that in real world environments such
as soil, compost and landfill oxidations, if they occur, will predominantly be under conditions where other interfering ingredients
are present and, in the case of landfill, at sub-atmospheric oxygen concentrations. This practice, therefore, can only result in a
relative ordering of the potential for oxidation of plastic materials under the conditions tested, which are not always reflective of
their behavior in a particular real world disposal systems. Prediction of the oxidation of a plastic under real world disposal
conditions is an essential further testing in appropriate methodologies, such as Test Method D5338 for composting. No claims can
be made for real world behavior based on this practice.
1.2 This practice is only intended to define the exposure conditions of plastics at various temperatures in air at atmospheric
pressure under controlled humidity levels for extended periods of time. The humidity levels and temperature ranges are selected
to be within the variable recorded seasonal ranges (upper and lower levels) generally observed in disposal sites where such plastics
are discarded. For example: soil (15 to 40 percent moisture); landfill (35 to 60 percent moisture), and compost (45 to 70 percent
moisture). It is optional to expose the plastic at zero humidity, if comparison with specified humidity ranges is of interest. Only
the procedures for heat and humidity exposures are specified, not the test method or specimen, necessary for the evaluation of the
heat and humidity exposure effects. The effect of heat and humidity on any particular property is determined by selection of the
appropriate test method and specimen; however, it is recommended that Practice D3826 be used to determine the embrittlement
endpoint, which is defined as that point in the history of a material when 75 % of the specimens tested have a tensile elongation
at break of 5 % or less at an initial strain rate of 0.1 mm/mm min.
1.3 This practice is used to compare the effects of heat and humidity at any selected temperature, such as those found in the
mentioned disposal environments, on the degradation of a particular plastic by selection of an appropriate test method and
specimen.
1.4 This practice is to be used in order to apply selected exposure conditions when comparing the thermal-aging characteristics
at controlled humidity levels of plastic materials as measured by the change in some property of interest (that is, embrittlement
by means of loss of elongation, molecular weight, disintegration, etc.). It is very similar to Practice D3045 but is intended for use
in evaluating plastics designed to be oxidized easily after use. The exposure times used for this practice will be significantly shorter
than those used for Practice D3045
1.5 The type of oven used can affect the results obtained from this practice. The user can use one of two methods for oven
exposure. Do not mix the results based on one method with those based on the other one.
1.6 Procedure A: Gravity-Convection Oven—Recommended for film specimens having a nominal thickness not greater than
0.25 mm (0.010 in.).
1.7 Procedure B: Forced-Ventilation Oven—Recommended for specimens having a nominal thickness greater than 0.25 mm
(0.010 in.).
1.8 This practice recommends procedures for comparing the thermal and humidity aging characteristics of materials at a single
temperature under dry or selected humidity conditions. Recommended procedures for determining the thermal aging characteristics
1
This practice is under the jurisdiction of A
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