GB/T 40934-2021 English PDF (GBT40934-2021)

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GB/T 40934-2021: Rotational moulding. Test method for powder flowability
GB/T 40934-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.080.01
CCS G 31
Rotational Moulding – Test Method for Powder Flowability
ISSUED ON: NOVEMBER 26, 2021
IMPLEMENTED ON: JUNE 1, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the 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 ... 7
7 Standard Environment for the Test ... 8
8 Test Procedures ... 9
9 Results and Characterization ... 9
10 Precision ... 10
11 Test Report ... 11
Appendix A (Informative) Requirements for Rotational Molding Powder Materials 12
Bibliography ... 13
Rotational Moulding – Test Method for Powder Flowability
WARNING: Personnel using this Document shall have practical experience working in
formal laboratory. This Document does not address all possible security issues. It is the
user's responsibility to take appropriate safety and health measures and ensure
compliance with the conditions stipulated in the relevant national laws and regulations.
1 Scope
This Document specifies test methods for the flowability of powders for rotational molding.
This Document applies to free-flowing powder materials for rotational molding, with particle
size D98≤1mm, and apparent density Da≥0.21g/mL.
2 Normative References
The provisions in following documents become the essential provisions of this Document
through reference in this Document. For the dated documents, only the versions with the dates
indicated are applicable to this Document; for the undated documents, only the latest version
(including all the amendments) is applicable to this Document.
GB/T 1636 Plastics - Determination of apparent density material that can be poured from
a specified funnel
GB/T 1957 Tolerances and general features for plain limit gauges
GB/T 2035-2008 Terms and definitions for plastics
GB/T 2547-2008 Plastic resins - Sampling
GB/T 2918 Plastics - Standard atmospheres for conditioning and testing
GB/T 6284 Chemical products for industrial use - General method for determination of
water content - The loss of mass on drying method
GB/T 16418 Particle system - Vocabulary
3 Terms and Definitions
For the purposes of this Document, the terms and definitions given in GB/T 2035-2008, GB/T
16418 and the following apply.
3.1 Rotational moulding
The processing method that puts the resin molding material into the mold; heats the mold and
make it rotate continuously at low speed; the resin in the mold is gradually coated and adhered
to the inner surface of the mold under the action of gravity and heat to form the required shape;
and the plastic product is obtained after cooling.
[SOURCE: GB/T 2035-2008, 2.873, modified]
3.2 Powder flowability; dk
The rate at which a dry powder flows through a defined funnel under the action of gravity only.
4 Principle
4.1 The principle of this test method is to characterize the free-flowing ability of the powder
only under its own gravity by measuring the time it takes for a unit mass of powder sample to
flow out of a funnel of specified size.
4.2 This test method can be used to characterize the following properties:
- the performance of powdery materials suitable for rotational molding process;
- the conveying performance of the powdery material, that is, the performance of the
powdery material passing through the hopper or feeding device evenly;
- The performance of the powdery material to flow evenly on all surfaces of the mold.
NOTE 1: Materials with poor powder flowability may cause defects such as bridging, uneven wall
thickness, rough inner surface, pinholes and color swirls in rotationally molded products.
NOTE 2: The conditions that affect the powder flowability results include: the shape, size, inner surface
condition, inner surface roughness of the funnel and powder temperature.
4.3 Combined with the apparent density data measured in GB/T 1636, the basis for judging that
powdery materials are suitable for rotational molding can refer to Appendix A.
5 Instruments and Equipment
5.1 Funnel
The funnel used in the test shall meet the following conditions:
8 Test Procedures
The test is carried out in the following procedures.
a) Close the outflow port of the funnel with a baffle.
b) Weigh the mass of the specimen, the unit is gram, and retain one digits after the decimal
point.
c) Gently pour the specimen into the funnel along the wall of the funnel to prevent
compaction and avoid any tilting. The funnel shall not be vibrated to promote the
accumulation of the specimen.
d) Quickly open the baffle; and press the timer at the same time to start counting. Use a pen
or ruler to gently tap the funnel to promote flow. The tap shall not cause the position of
the funnel to move, but fixed mechanical vibration device that can promote flow shall
not be used.
e) Observe from the top of the funnel and stop timing when the outflow port is visible.
f) Observe the flow pattern of the specimen:
--- Continuous flow: the specimen flows out continuously until it completely flows out
of the funnel, denoted by c;
--- Intermittent flow: the specimen flows out intermittently until it completely flows out
of the funnel, represented by i;
--- No flow: The specimen does not flow out of the funnel or stops flowing out of the
funnel during of the test.
g) Use the same specimen to repeat the measurement for 3 times. For hygroscopic specimen,
the measurement shall be completed within 5min.
h) After each measurement, any residue adhering to the inner wall of the funnel shall be
cleaned.
9 Results and Characterization
9.1 Powder outflow time
Take the arithmetic mean of 3 measurements as the measurement result of the powder outflow
time. The result is rounded off to one digit after the decimal point. If one of the three
measurements is "no flow", the test result should be "NG".
9.2 Powder flowability
The powder flowability is calculated according to the Formula (1), and the result is rounded off
to one digit after the decimal point.
NOTE: For powders whose powder outflow time is "NG", the powder flowability test is not conducted.
Where:
dk - powder flowability, in s/100g; k represents the flow type. If k takes c, it shall mean
continuous flow; if k takes i, it shall mean intermittent flow;
t - the powder outflow time, in s;
m - the mass of the specimen, in g.
EXAMPLE: 100.2g of a certain powder is used for testing; the measured values of powder outflow time
are 25.7s, 26.1s and 25.5s; and the flow type is continuous flow. Calculated powder flow time
t=(25.7s+26.1s+25.5s)/3=25.8s, powder flowability dc=100×25.8s/100.2g=25.7s/100g.
10 Precision
In the same laboratory, the same operator uses the same equipment, according to the same test
method, and tests the same measured object independently within a short period of time, and
the absolute difference between the obtained two independent test results does not exceed the
repeatability limit (r); the repeatability limit (r) is calculated according to the Formula (2):
Where:
dk - the average value of two measured values, in s/100g.
In different laboratories, different operators use different equipment, according to the same test
method, the absolute difference between the obtained two independent test results by
independently testi...