HG/T 2625-1994 Determination of linear shrinkage of epoxy casting resin HG/T2625-1994 standard download decompression password: www.bzxz.net

Note: This standard is used to identify the test resin.
According to the test results and test period specified in Article 6.1
Determination of linear shrinkage of epoxy casting resin Subject and scope of application
This international standard specifies the method for determining the shrinkage of the linear part of epoxy paint and other resins during the curing process 1.5.32
HG/T 2625-94
This standard is applicable to casting resins composed of epoxy resin as the base material, and its measured value is useful for predicting the shrinkage characteristics in molds of other sizes and shapes.
2: Reference standards
GB2918 Standard environment for state conditioning and testing of plastic specimens 3 Principle
3.1 The shrinkage measured in this standard is the sum of the shrinkage after gelation and the shrinkage after cooling from the curing temperature and the exothermic peak temperature to room temperature.
3. When the exothermic temperature of the chemical crosslinking reaction has passed, the curing casting resin system will shrink uniformly in all directions. However, the measurement of the compensatory shrinkage rate is complicated by the fact that at the moment when the maximum shrinkage is occurring, the partially cured casting resin system is tightly attached to the mold wall. Friction prevents the system from moving on the mold surface, causing the maximum shrinkage to occur in the direction perpendicular to the mold surface. The stress caused by this uneven shrinkage in the casting must be eliminated. The casting can be cured at a temperature slightly below the melting point. Since these stresses are eliminated, the auxiliary curing often causes further shrinkage.
3.3 Using the molds of this standard, the shrinkage rate perpendicular to all surfaces, except the surface of the mold, is consistent and proportional to the distance over which the shrinkage occurs. Measure the shrinkage of the casting between the two surfaces of the mold, that is, the linear shrinkage. Calculate the linear shrinkage rate, and the shrinkage per meter length is expressed as (cm/cl). Instruments and materials The mold is shown in the figure below. The material is 45# steel, and the inner walls of the two plates at both ends of the mold are smooth and should not have defects and rust. Use the six medical schools to determine the linear shrinkage rate pre-test mold! In order to allow the sample to be poured in normally, select the cross-sectional area of ​​the mold according to the figure. The cross-sectional area is relatively large, and the exothermic peak value is also relatively high, which also affects the measurement of its linear shrinkage rate. Therefore, a mold of appropriate size should be selected through experiments. Mold volume Depth micrometer: The graduation value is not greater than 0.c02mn. 4.3
Polytetrafluoroethylene film: thickness 0.020~0025mmTemperature measurement device: accurate to 1℃
4.5.Mineral oil or silicone oil.
Specimen preparation
Nominal radius
Wipe the inner wall of the mold with mineral oil or silicone oil, then line it with a layer of polytetrafluoroethylene and make it smooth and wrinkle-free.5.1
5.2The mold and each component of the curing system used are placed at the same temperature as the test casting for more than 4 hours. 5.3Air inclusion will affect the shrinkage characteristics of the specimen curing, so try to generate as few air bubbles as possible when mixing the components. If necessary, the air bubbles can be removed by vacuum device.
5.4 "Inject the mixed sample of the predetermined volume into the mold, and be careful to avoid trapping air. For materials that cure at room temperature, the sample injection depth should be less than 30°C.
5.5 Place a suitable temperature measuring device at the geometric center of the reactants to record the exothermic peak temperature. 5.6 Curing the casting resin system in the mold according to the curing conditions. Stone state adjustment and test environment
6.1 According to GB2918, place the mold with the casting for 40 hours under standard laboratory conditions of temperature 2312°C and relative humidity 50% ± 5%. . In case of dispute, the allowable deviation of overflow is soil "℃, and the relative humidity is ±2%. 6.2 Unless otherwise specified, the test should be carried out at 23±2℃ and 50%±5% relative humidity. If cumulative jamming occurs, the allowable deviation of overflow is soil 1℃, and the relative humidity is ±2%. Operation steps
7.1 After the state adjustment is completed, remove the two end panels and take the casting out of the mold, and remove the polytetrafluoroethylene film. 7.2 Reinstall the removed end face in the original position of the mold. 7.3 Put the casting back into the mold in the same position as before it was taken out. 7.4 Make sure the specimen is tightly Contact the end panel of the mold, take the mold length as the reference, place the bottom plate measuring surface of the depth scale close to the mold opening end, measure the change in the length of the casting, move the depth scale down, and take the average of the four readings as the length difference of the porcelain casting.
8 Calculation
: Calculate the linear shrinkage rate (cm/cm) according to the following formula; Linear shrinkage rate (cm/em)
In the formula, A-wwW.bzxz.Net
length difference, cm;
B——the thickness of the ethylene film in the fourth mold, cm: C The length of the inner wall of the two tripods at the end of the mold, cm
Test report
Test report The report shall include the following:
Indicate the standard range,
The size of the mold used.
The depth (or volume) of the casting.
The ambient temperature during the casting operation.
The degree of reaction of the casting resin mixture during the casting operation. f. The peak temperature of the hottest period.
If the sample conditioning during the curing process is different from that in this standard, it shall be noted in the report. h.
Express the linear shrinkage as the shrinkage per centimeter of length. 1539
Determination of viscosity of dilute solutions of cast methyl methacrylate polymers and copolymers HG/T 2626-94
Subject and Applicability
This standard specifies the method for determining the viscosity of cast flat-based acrylic methyl methacrylate dilute solutions. This standard is applicable to cast plugs, non-molding extrusion type methyl methacrylate (MMA) homopolymers, copolymers and their mixtures. The mixture contains at least 80% (m/m) of methyl methacrylate formaldehyde polymers. It may or may not contain additives. Reference Standard
GB/T1632 Determination of viscosity and intrinsic viscosity of polymer dilute solutions 3
Measure the flow-through time of a solvent and a polymer solution of the solvent with a specified concentration at 25±0.05℃. Calculate the viscosity and intrinsic viscosity, viscosity number VN, expressed in ml/g, from the above measured flow-through time and solution concentration.
1(2-n)
In the formula --- dynamic viscosity of the test solution, mPas1ne-dynamic viscosity of the solvent, niPa·s
concentration of the compound solution·g/ml.
If the density and β of the solution and the solvent are slightly different, the sum of 7 and β in formula (1) can be replaced by the sum of the kinematic viscosities of the solution and the solvent. Unit: mrm\/s.
Trichloromethane, analytical grade. Store in a brown negative bottle and keep in a dark place.
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