GB/T 17037 consists of the following five parts under the general title Plastic - Injection moulding of test specimens of thermoplastic materials:
—— Part 1: General principles, and moulding of multipurpose and bar test specimens;
—— Part 2: Small tensile bars;
—— Part 3: Small plates;
—— Part 4: Determination of moulding shrinkage;
—— Part 5: Preparation of standard specimens for investigating anisotropy.
This is Part 1 of GB/T 17037.
This part is drafted in accordance with the rules given in GB/T 1.1- 2009.
This part replaces GB/T 17037.1-1997 Injection moulding of test specimens of thermoplastic materials - Part 1: General principles and moulding of multipurpose and bar test specimens. In addition to editorial changes, the following main technical changes have been made with respect to GB/T 17037.1-1997:
—— The following terms and definitions are added: mass of moulding (3.22), mass of test specimen (3.23), sink mark ratio (3.24), and cavity pressure (3.25);
—— The specimen type code is revised according to GB/T 37426.
—— The methods for setting the injection moulding parameters (see Annex D) is added;
—— The determination method of hold pressure and hold time (see Annex E) is added;
This part has been redrafted and modified in relation to ISO 294-1: 2017 Plastics - Injection moulding of test specimens of thermoplastic materials - Part 1: General principles, and moulding of multipurpose and bar test specimens.
The main technical differences with respect to ISO 294-1: 2017 are as follows:
—— The adjustments of technical differences are made for the normative references in this standard so as to adapt to the technical conditions of China. The adjustment is mainly reflected in clause 2 "Normative reference", with the specific adjustments as follows:
? ISO 179-1 is replaced by GB/T 1043.1 which is identical to the international standard;
? ISO 294-4 is replaced by GB/T 17037.4 which is identical to the international standard;
? ISO 20753 is replaced by GB/T 37426, which is modified in relation to the international standard;
The following editorial changes have been made in this part:
—— The web address information of ISO and IEC for maintenance of terminology database in clause 3 Terms and definitions is given in the form of note.
Attention is drawn to the possibility that some of the elements of this standard may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.
This part was proposed by China Petroleum and Chemical Industry Association.
This part was prepared by the National Technical Committee 15 on Plastic of Standardization Administration of China.
The previous edition replaced by this part is as follows:
—— GB/T 17037.1-1997.
Introduction
Many factors in the injection-moulding process influence the properties of moulded specimens and hence the measured values obtained when the specimens are used in a test method. The mechanical properties of such specimens are strongly dependent on the conditions of the moulding process used to prepare the specimens. Exact definition of each of the main parameters of the moulding process is a basic requirement for reproducible and comparable operating conditions. See Bibliography [1], [2], [4], [5] and [6].
It is important in defining moulding conditions to consider any influence the conditions may have on the properties to be determined.
Thermoplastics exhibit differences in molecular orientation in crystallization morphology (for crystalline and semicrystalline polymers), in phase morphology (for heterogeneous thermoplastics) as well as in the orientation of anisotropic fillers such as short fibres; see Bibliography [3]. Residual (“frozen-in”) stresses in the moulded specimens and thermal degradation of the polymer during moulding also influence properties. Therefore, these phenomena must be controlled to avoid the fluctuation of the numerical values of the specimen performance.
Care has been taken to ensure that the GB/ ISO moulds described can all be fitted in existing injection moulding equipment and have interchangeable cavity plates.
Plastics - Injection moulding of test specimens of thermoplastic materials - Part 1: General principles, and moulding of multipurpose and bar test specimens
1 Scope
This part of GB/T 17037 gives the general principles to be followed when injection moulding specimens of thermoplastic materials and gives details of mould designs for preparing two types of specimen for use in acquiring reference data, i.e. type A1 and type B1 specimens as specified in GB/T 37426, and provides a basis for establishing reproducible moulding conditions. Its purpose is to provide consistent descriptions of the main parameters of the moulding process and to establish a uniform practice in reporting moulding conditions. The particular conditions required for the reproducible preparation of specimens will vary for each material used and are given in the national standard for the relevant material or are to be agreed upon between the interested parties.
This part is applicable to reproducible preparation of multipurpose and bar test specimens by injection moulding of thermoplastic materials.
Note: Interlaboratory tests with acrylonitrile/ butadiene/ styrene (ABS), styrene/ butadiene (SB) and poly methyl methacrylate (PMMA) have shown that mould design is an important factor in the reproducible preparation of specimens.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 1043.1 Plastics - Determination of charpy impact properties - Part 1: Non-instrumented impact test (GB/T 1043.1-2008, ISO 179-1: 2000, IDT)
GB/T 17037.3-2003 Plastics - Injection moulding of test specimens of thermoplastic materials - Part 3: Small plates (ISO 294-3: 2002, IDT)
GB/T 17037.4 Plastic - Injection moulding of test specimens of thermoplastic materials - Part 4: Determination of moulding shrinkage (GB/T 17037.4-2003, ISO 294-4: 2001, IDT)
GB/T 37426-2019 Plastics - Test specimens (GB/T 37426-2019, ISO 20753: 2018, MOD)
ISO 294-2 Plastics - Injection moulding of test specimens of thermoplastic materials - Part 2: Small tensile bars
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
Note: ISO and IEC maintain terminological databases for use in standardization at the following addresses:
—— IEC Electropedia: available at http:// www .electropedia .org
—— ISO Online browsing platform: available at http://wwwi.so.org/obp
3.1
mould temperature
TC
average temperature of the mould cavity surfaces measured after the system has attained thermal equilibrium and immediately after opening the mould, ℃
3.2
melt temperature
TM
temperature of the molten plastic in a free shot, ℃
3.3
melt pressure
P
pressure of the plastic material in front of the screw at any time during the moulding process, MPa
3.4
hold pressure
PH
melt pressure (3.3) during the hold time (3.9), MPa
3.5
moulding cycle
complete sequence of operations in the moulding process required for the production of one set of specimens (see Figure 1)
Key:
X—— time t; 5—— mould-open time tO;
Y—— melt pressure p; 6—— melt pressure p;
1—— cycle time tT; 7—— longitudinal position of screw l;
2—— injection time tI; 8——mould opening;
3—— hold time tH; 9——mould closing
4—— cooling time tC;
Note: The melt pressure during the cooling phase is not zero due to back pressure effects.
Figure 1 Schematic diagram of an injection-moulding cycle showing the melt pressure (full line) and the longitudinal position of the screw (dashed line) as a function of time
3.6
cycle time
tT
time required to carry out a complete moulding cycle (3.5), s
Note: The cycle time is the sum of the injection time, tI, the cooling time, tC, and the mould open time, tO.
3.7
injection time
tI
time from the instant the screw starts to move forward until the switchover point between the injection period and the hold period, s
3.8
cooling time
tc
time from the end of the injection period until the mould starts to open, s
3.9
hold time
tH
time during which the pressure is maintained at the hold pressure (3.4), s
3.10
mould-open time
tO
time from the instant the mould starts to open until the mould is closed and exerts the full clamping force (3.19), s
Note: It includes the time required to remove the mouldings from the mould.
3.11
cavity
part of the hollow space in a mould that produces one specimen
3.12
single-cavity mould
mould with one cavity (3.11) only
3.13
multi-cavity mould
mould that has two or more identical cavities (3.11) in a parallel-flow arrangement
Note: Identical flow-path geometries and symmetrical positioning of the cavities in the mould ensure that all specimens from one shot are equivalent in their properties.
3.14
family mould
multi-cavity mould (3.13) containing cavities (3.11) which have different geometries
3.15
GB/ISO mould
one of several standard moulds including designated GB/T 37426 type A1, B1, C1, D11 and D12 intended for the reproducible preparation of specimens with comparable properties
Note: The moulds have a fixed plate with a central sprue, plus a multi-cavity cavity plate as described in 3.13.
Note: Additional details are given in 4.1.1.4. An example of a complete mould is shown in Annex C.
3.16
critical cross-sectional area
Ac
cross-sectional area of the cavity (3.11) in a single-cavity mould (3.12) or multi-cavity mould (3.13) at the position where the critical portion of the test specimen, i.e. that part on which the measurement will be made, is moulded, mm2
Note: For tensile specimens, for instance, the critical portion of the test specimen is the narrow section which is subjected to the greatest stress during testing.
3.17
moulding volume
VM
ratio of the mass of the moulding (3.22) to the density of the solid plastic, mm3
3.18
projected area
Ap
overall profile of the moulding projected on to the parting plane, mm2
3.19
clamping force
FM
force holding the plates of the mould closed, kN
3.20
injection velocity
vI
average velocity of the melt as it passes through the critical cross-sectional area (3.16), mm/s
3.21
shot volume max.
VS
product of the maximum metering stroke of the injection-moulding machine and the cross-sectional area of the screw, mm3
3.22
mass of moulding
Wm
total mass of the specimens, the runner(s) and the sprue in a single moulding, g
3.23
mass of test specimen
Ws
mass of a single specimen, excluding the runner(s) and the sprue, g
3.24
sink mark ratio
SR
indication of the relative depth of a sink mark on the surface of the specimen, dimensionless
Note: The measurement of sink mark and the calculation method of sink mark ratio are shown in E.1. 2.1.
3.25
cavity pressure
Pc
pressure of the melt in the mould cavity, measured with a pressure sensor on the inner surface of the cavity, MPa
4 Apparatus
4.1 Moulds
4.1.1 GB/ISO moulds (multi-cavity)
4.1.1.1 GB/ISO moulds are strongly recommended for producing specimens for the acquisition of data which are intended to be comparable (see GB/T 19467.1, GB/T 19467.2, ISO 11403-1., ISO 11403-2 and ISO 11403-3), as well as for use in the case of disputes involving different standards.
4.1.1.2 Multipurpose test specimen as specified in GB/T 37426 type A1 shall be moulded in a two-cavity mould using a Z- or T-runner (see Annex A). The mould as shown in Figure 2 shall meet the requirements specified in 4.1.1.4. Of the two types of runner, the Z-runner is preferred owing to the more symmetrical closure force obtained. The specimen mouldings produced shall have the dimensions of the type A1 specimen specified in GB/T 37426.
4.1.1.3 Rectangular 80 mm × 10 mm × 4 mm bars (GB/T 37426 type B1) shall be moulded in a four-cavity mould with a double-T runner. The mould shall meet the requirements specified in 4.1.1.4, schematic diagram is shown in Figure 3. The bars produced shall have the same cross-sectional dimensions along their central section as multipurpose specimens (see GB/T 37426) and a length of 80 mm ± 2 mm.
4.1.1.4 The main constructional details of the GB/ISO moulds used for preparing type A1 and type B1 specimens specified in GB/T 37426 are shown in Figures 2 and 3. They shall meet the following requirements:
Foreword i
Introduction iii
1 Scope
2 Normative references
3 Terms and definitions
4 Apparatus
5 Procedure
6 Report on test-specimen preparation
Annex A (Informative) Examples of runner configurations
Annex B (Informative) Standards for plastic injection mould components
Annex C (Informative) Example of an injection mould
Annex D (Informative) Methods for setting the injection moulding parameters
Annex E (Informative) Methods of determining the hold pressure and hold time
Bibliography
