QB/T 2957-2008 English PDF (QBT2957-2008)

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QB/T 2957-2008: Determination of starch content of starch based plastics Thermogravimetry(TG)
QB/T 2957-2008
QB
LIGHT INDUSTRY STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.180
Classification No.: G32
File No.: 24049-2008
Determination of starch content of starch based plastics
Thermogravimetry (TG)
ISSUED ON: MARCH 12, 2008
IMPLEMENTED ON: SEPTEMBER 01, 2008
Issued by: National Development and Reform Commission, People's Republic of
China
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Principle ... 5
5 Instruments and equipment ... 5
6 Specimen ... 5
7 Test steps ... 6
8 Result calculation ... 6
9 Test report ... 8
Determination of starch content of starch based plastics
Thermogravimetry (TG)
1 Scope
This Standard specifies the method to determine starch content in starch based plastics.
This Standard is applicable to starch based plastics with starch and resin as the main
raw materials that have obvious differences in the characteristic temperature of thermal
weight loss.
2 Normative references
The provisions in following documents become the provisions of this Standard through
reference in this Standard. For dated references, the subsequent amendments (excluding
corrigendum) or revisions do not apply to this Standard, however, parties who reach an
agreement based on this Standard are encouraged to study if the latest versions of these
documents are applicable. For undated references, the latest edition of the referenced
document applies.
GB/T 6425, Nomenclature for thermal analysis
ISO 11358, Plastics - Thermogravimetry (TG) of polymers - General principles
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T 6425 as
well as the followings apply.
3.1 starch based plastic
Plastic materials and products such as resins, films, sheets and injection molded
products that are processed by molding with starch, plastic resins and additives as the
main raw materials.
3.2 characteristic temperatures
The temperature in the TG curve that characterizes a substance, expressed by
extrapolated initial temperatures and extrapolated end temperatures.
3.3 extrapolated initial temperatures
The temperature corresponding to the intersection of the TG curve starting mass line
extrapolation and the tangent made at the maximum slope of the corresponding
transition curve.
3.4 extrapolated end temperatures
The temperature corresponding to the intersection of the TG curve ending mass line
extrapolation and the tangent made at the maximum slope of the corresponding
transition curve.
4 Principle
Use TG method to determine starch and starch based plastic, respectively. Determine
the characteristic temperature and the mass corresponding to that temperature in the TG
curve of starch. In the TG curve of starch based plastic, determine the temperature
corresponding to the characteristic temperature of starch and the corresponding mass.
Use the ratio of the two masses to calculate the starch content in starch based plastic,
expressed as mass fraction.
5 Instruments and equipment
5.1 Thermogravimetric analyzer
- High temperature furnace: the temperature can reach 800°C; the heating rate is
20°C/min;
- Thermal balance: the weighing can reach to 50mg; the weighing accuracy is
0.02mg;
- Can record the TG curve.
5.2 Gas source
Specimen gas: nitrogen; analytical grade; the flow is 30mL/min~150mL/min.
5.3 Balance
The accuracy is 0.1mg.
5.4 Other requirements shall be in accordance with the provisions of ISO 11358.
6 Specimen
- Powders, granules or specimens cut directly from the product.
- Quantity: 1 portion for starch, 2 portions for starch based plastic. The mass of each
portion is about 10mg.
7 Test steps
a) Turn on the thermogravimetric analyzer and gas source. Adjust the flow of
specimen gas to 50mL/min. Adjust the flow of other gases to corresponding value;
b) Carry out mass and temperature calibration to the instrument according to ISO
11358;
c) Use the balance to weigh about 10mg of starch specimen. Put it into the
thermogravimetric analyzer crucible;
d) Heat the temperature from room temperature to 105°C at a constant rate of
20°C/min. Keep it at a constant temperature for 5min and then cool down to room
temperature;
e) Use the thermal balance to weigh the mass (mS);
f) Uniformly heat the temperature from room temperature to 600°C at a rate of
20°C/min. Record the TG curve;
g) Use the balance to weigh about 10mg of starch based plastic specimen. Put it into
the thermogravimetric analyzer crucible. Repeat the step of 7d). Use the thermal
balance to weigh the mass (mS1);
h) Repeat the step of 7f);
i) Compare the characteristic temperatures TA, TB in the TG curve of the starch
specimen with the temperatures TA1, TB1 -- corresponding to the starch
characteristic temperatures -- in the TG curve of starch based plastic specimen. If
the difference between TA and TA1 or TB and TB1 is greater than 20°C, take another
specimen and redo it.
8 Result calculation
8.1 Determination of TG curve and relevant parameters
In the TG curve of starch specimen (Figure 1), determine the weight loss transition that
characterizes the specimen. At this transition, obtain the extrapolated initial temperature
TA and the extrapolated end temperature TB as two characteristic temperatures of starch.
Determine the corresponding mass mA and mB of TA and TB. In the TG curve of starch
based plastic specimen (Figure 2), find out the weight loss transition at the temperature
corresponding to the characteristic temperature of the starch specimen. Obtain the