GB/T 7141-2008 PDF English
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| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB/T 7141-2008 | English | 115 |
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Plastics -- Methods of heat aging
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| GB/T 7141-1992 | English | 239 |
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Plastics-Methods of exposure to thermal air
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GB/T 7141-2008: Plastics -- Methods of heat aging---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT7141-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.080;83.080.01
G 31
Replacing GB/T 7141-1992
Plastics - Methods of heat aging
Issued on. AUGUST 14, 2008
Implemented on. APRIL 01, 2009
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword... 3
1 Scope... 5
2 Normative references... 6
3 Terms and definitions... 6
4 Meaning and application... 6
5 Equipment... 8
6 Specimens... 9
7 State adjustment... 9
8 Test steps... 9
9 Result calculation... 11
10 Test report... 13
11 Precision and bias... 14
Annex A (informative) Technical differences between this Standard and ASTM
D5510.1994 (2001) and their reasons... 15
Foreword
This Standard adopted ASTM D5510.1994 (2001) " Standard Practice for Heat
Aging of Oxidatively Degradable Plastics" (English edition).
This Standard was redrafted based on ASTM D5510.1994 (2001).
Considering China's national conditions, this Standard has made some
changes when using ASTM D5510.1994 (2001). The relevant technical
differences have been incorporated into the main text and marked with a single
vertical line in the margins of the clauses they refer to. A list of these technical
differences and their reasons is given in Annex A for reference.
For ease of use, the following editorial changes have been made to ASTM
D5510.1994 (2001).
a) changed "ASTM Standard" to "this Standard";
b) deleted the standard description of ASTM D5510.1994 (2001);
c) deleted the publication notes of ASTM D5510.1994 (2001);
d) deleted the reference standard notes of ASTM D5510.1994 (2001);
e) added the foreword of this Standard;
f) in normative references, used corresponding national standards or
international standards to replace the ASTM standards;
g) added Annex A.
This Standard replaces GB/T 7141-1992 " Plastics-Methods of exposure to
thermal air".
Compared with GB/T 7141-1992, the main differences in this Standard are as
follows.
- There is only one type of heat aging test box method in GB/T 7121-1992,
that is, the forced ventilating air heat aging test box. However, this
Standard provides two heat aging test box methods, that is, gravity
convection heat aging test chamber and forced ventilation heat aging test
chamber. These two kinds of heat aging test chambers are respectively
suitable for specimens with different nominal thicknesses;
- This Standard puts forward more requirements for the selection of test cycle
for plastic heat aging test;
- In addition to providing test methods and results comparison methods for
each material at a single temperature during each exposure period, this
Standard also provides test methods and results comparison methods for
exposure tests for each material under a range of temperatures. The test
results can be used for the basic assessment of the temperature stability
of the material or the assessment of the maximum expected service life at
a set temperature.
Annex A of this Standard is informative.
This Standard was proposed by China Petroleum and Chemical Industry
Association.
This Standard shall be under the jurisdiction of Subcommittee on Aging
Methods of National Technical Committee on Plastics of Standardization
Administration of China.
The drafting organizations of this Standard. Guangzhou Synthetic Materials
Research Institute Co., Ltd., Wuxi Jinhua Test Equipment Co., Ltd., Beijing
Tianjia Technology Co., Ltd.
The participating organizations of this Standard. Zhuhai Yuankang Enterprise
Co., Ltd., Longkou Daun Engineering Plastics Co., Ltd., Guangzhou Kingfa
Technology Co., Ltd.
Main drafters of this Standard. Wang Haojiang, Shao Fang, Li Jie, Shan Jinhua,
Yang Xinhua, Yang Yunong, Xie Zhenping.
Versions of standard substituted by this Standard are. GB 7141-1986, GB/T
7141-1992.
Plastics - Methods of heat aging
1 Scope
1.1 This Standard specifies the exposure conditions when plastics are only
exposed to hot air at different temperatures for a long time. This Standard only
specifies the method of heat exposure, but does not specify the test method or
specimen. The influence of heat on any properties of plastics can be determined
by selecting suitable test methods and specimens. This Standard recommends
the use of ASTM D3826 standard to determine the end point of embrittlement.
The end point of embrittlement means that at an initial strain rate of 0.1 mm/min,
when 75% of the tested specimens have an elongation at break of 5% or less,
the material reaches its end point of embrittlement.
1.2 This Standard gives guidelines for comparing the heat aging properties of
materials. These properties are measured by changes in certain related
properties (that is, the embrittlement properties are measured by the decrease
in elongation). This Standard applies to the evaluation of plastics that are easily
oxidized during use.
1.3 The results obtained in accordance with this Standard are affected by the
type of heat aging test chamber used. The user can choose one of two methods
to conduct heat aging test chamber exposure. The results based on these two
methods shall not be confused with each other.
1.3.1 Method A. Gravity convection heat aging test box – It is recommended for
thin specimens with a nominal thickness of not more than 0.25mm.
1.3.2 Method B. Forced ventilation heat aging test chamber – It is
recommended for specimens with a nominal thickness greater than 0.25mm.
1.4 This Standard introduces methods to compare the heat aging properties of
materials at a single temperature. This Standard also describes the method for
determining the heat aging properties of materials at a series of temperatures,
so as to estimate the time required for the material to change its properties at a
lower temperature. This Standard does not predict the heat aging performance
when factors such as stress, environment, temperature and time control failure
interact.
1.5 This Standard does not involve relevant safety instructions. Even if there is,
it is only related to its application. It is the responsibility of users of this Standard
to establish applicable safety and health regulations and to determine
applicable regulatory limits before use.
NOTE. There is no ISO standard equivalent to this Standard.
2 Normative references
The following documents contain the provisions which, through reference in this
Standard, become the provisions of this Standard. For dated references, their
subsequent amendments (excluding corrigendum) or revisions do not apply to
this Standard. However, the parties who enter into agreement based on this
Standard are encouraged to investigate whether the latest versions of these
documents are applicable. For undated reference documents, the latest
versions apply to this Standard.
GB/T 2035, Terms and definitions for plastics (GB/T 2035-2008, ISO
472.1999, IDT)
GB/T 2918, Plastics - Standard atmospheres for conditioning and testing
(GB/T 2918-1998 idt ISO 291.1997)
GB/T 7142, Determination of time-temperature limits of plastics after
exposure to prolonged action of heat (GB/T 7142-2002, ISO 2578.1993,
MOD)
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T
2035 apply.
4 Meaning and application
4.1 Since the correlation between the results obtained according to this
Standard and the actual use environment has not been determined, these
results are only used for comparison and rating.
4.3 Under normal circumstances, short-term exposure of plastics to high
temperatures will release volatile substances such as moisture, solvents or
plasticizers; reduce molding stress; improve the curing of thermosetting plastics;
increase crystallinity; and make the color change of plasticizer or colorant or
both. Generally, further shrinkage will occur as volatiles decrease or further
polymerization reaction occurs.
4.4 Certain plastics, such as PVC, may become brittle due to loss of plasticizers
or breakage of polymer molecular chains. Polypropylene and its copolymers
tend to become very brittle when the molecules are degraded. On the other
hand, polyethylene becomes soft before the tensile strength and elongation
decrease and become brittle.
4.7 The exposure effect of the sample may be significantly different. Especially
when exposed for a long time, the error will accumulate over time. Factors
affecting data reproducibility include the degree of temperature control in the
heat aging test box, the humidity of the heat aging test box, the air flow rate on
the surface of the sample, and the exposure period. In the long-term test, some
materials are easily degraded due to the influence of humidity. For example,
hydrolysis-sensitive materials (i.e., hydrolysis-degradable plastics) will degrade
due to moisture during long-term thermal tests.
4.9 In fact, there may be multiple temperature values. Each failure criterion
corresponds to a temperature value. Therefore, to ensure the validity of the
temperature value in any application, the heat aging procedure must be exactly
the same as the intended exposure conditions of the final product. If the final
use of the material is not evaluated by the aging procedure, then the resulting
temperature index is not suitable for this application of the material.
4.10 In some cases, the material can be exposed to a temperature for a specific
period, followed by exposure to another temperature for a specific period. This
Standard is suitable for these applications. After getting the thermal aging curve
of the first temperature, the heat aging curve at the second temperature can be
obtained by exposing the sample after exposure to the first temperature.
4.11 When an Arrhenius curve or equation based on test data at a series of
temperatures is used to estimate the time to reach a specified performance
change at a lower temperature, there may be a very large error. The estimated
time to reach the specified performance change or failure shall always be within
the 95% confidence interval.
5 Equipment
5.1 Environmental conditions
The environmental conditions of the equipment shall provide environmental
state adjustment.
5.2 Heat aging test chamber
5.3 Specimen holder
The design of the specimen holder shall ensure the air circulation around the
specimen.
5.4 Test equipment
It is used to determine the selected performance or multiple performances
according to the corresponding national standards.
6 Specimens
6.1 The number and type of specimens required shall meet the requirements of
the corresponding national standards for testing specific properties.
6.2 The thickness of the specimen shall be equivalent to but not greater than
the minimum thickness in the intended application.
6.3 The method of making the specimen shall be the same as that used in the
intended application.
6.4 All test specimens for a series of temperatures shall be the same batch.
7 State adjustment
7.1 According to the regulations of GB/T 2918, the initial test is carried out in a
standard laboratory environment. The specimen shall be adjusted according to
the requirements of the performance test method specified by the national
standard.
8 Test steps
8.1 Choose Method A or B according to the applicable heat aging test chamber
type in item 5.2.
8.2 When testing at a single temperature, all materials shall be exposed
simultaneously in the same device. The number of parallel specimens for each
material in each exposure period shall be enough, so as to ensure that the test
results used to characterize material properties can be compared with analysis
of variance or similar statistical data analysis methods.
8.3 When performing a series of tests at temperatures, in order to determine
the relationship between the specified performance change and temperature, a
minimum of four temperatures shall be used. It is recommended to select the
exposure temperature according to the following methods.
8.4 Test the selected properties of a set of non-exposed specimens according
to applicable test methods, including conditioning.
8.5 Mount the specimen on the specimen holder. Put the specimen holder in
the heat aging test box to ensure that both sides of the specimen are exposed
to the airflow. In order to minimize the influence of temperature changes in the
heat aging test chamber, it is recommended to periodically adjust the position
of the specimen or specimen holder.
9 Result calculation
9.1 When materials are compared at a single temperature, analysis of variance
shall be used to compare the average of the measured performance data for
each material at each exposure time. Use each group of parallel determination
results for each material to be compared for analysis of variance. It is
recommended to use an F statistic with a 95% confidence level to determine
the validity of the results of the analysis of variance.
9.2 When comparing materials at a range of different temperatures, it shall use
the following methods to analyze the data. Estimate the exposure time required
to reach a predetermined level of performance change at a lower temperature.
This time can be used for the basic assessment of the temperature stability of
the material, or as an estimate of the maximum expected service life at the
selected temperature.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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