Thermal insulation material requirements and inspection
[China Aluminum Network] I. Classification of heat insulation data
Insulation data refers to the non-metallic materials used to connect aluminum alloy profiles with low thermal conductivity. According to the processing methods of aluminum alloy thermal insulation profiles, the thermal insulation data is divided into two categories, one is for sliver processing. Thermal insulation profiles are insulation strips. It is the selection of polyamide nylon (abbreviated as PA66) kneading heat insulation materials, according to the aluminum alloy profile planning needs to knead a variety of different cross-section. The other type is insulation materials used for cast-in-process heat-insulating profiles, ie, heat-insulating glues. The main types are polyurethane and rigid polyurethane foam.
Second, the quality requirements of insulation data
The general inspection items of heat insulation data include appearance quality, scale error, horizontal room temperature stretching function, moist heat resistance, brittleness, and stress crack resistance. The specific targets are shown in Table 6-4-1, and other physical functions are shown in Table 6-4. 2 and Table 6-4-3.
Table 6—4—1 Demand Table for Heat Insulation Data
Items
Quality requirements
Appearance quality
The appearance of lubrication, flat, no depression, bulge, crack, no corners and other shortcomings
Scale error/mm
±0.05
Room temperature tensile test
Lateral tensile characteristics ≥ 24 N/mm
Water immersion experiment, hot and humid experiment
Lateral tensile characteristics ≥ 24 N/mm. Compared with the results of previous room-temperature transverse tensile experiments, the decrease in transverse tensile strength values ​​does not exceed 30%.
Brittle test
Compared with the results of previous room-temperature transverse tensile experiments, the decrease in transverse tensile strength values ​​does not exceed 30%.
Stress cracking test
Investigate the hole with naked eyes
Table 6-4-2 Typical Properties of Thermal Bar (PA66) Target Table
Typical features of the PA66
Typical value
See Inspection Specifications
Thermal conductivity/W·(m·K)-1
≤0.35
GBl0297
Incineration function
R2
GB8624, GB8626
Heat distortion temperature/°C
≥240
GB/Tl634
Linear expansion coefficient (vertical)/K-1
≤3.5×10-5
GB/Tl036
Continued Table 6-4-2
Typical features of the PA66
Typical value
See Inspection Specifications
Density and error/g·cm-3
1.3±0.05
GB/Tl033
Shore hardness (D type)
≥82
GB/T2411
Impact strength (unnotched)/kJ·m-2
≥30
GB/Tl043
Tensile strength/N·mm-2
≥80
GB/Tl040
Elastic modulus/N·mm-2
≥2900
Elongation after breaking/%
3 to 8
Table 6—4—3 Heat Insulation Information Typical Characteristics of Polyurethane and Rigid Polyurethane Foam
Polyurethane, rigid polyurethane foam typical features
Typical value
See Inspection Specifications
Thermal conductivity/W·(m·K)-1
≤0.121
ASTM C 518
Hot melt temperature/°C
≥177
ASTM D 2117
Heat disturbance temperature (method B) 455 kPa (66 psi)/°C
≥90
ASTM D 648
Linear expansion coefficient (vertical)/K-1
≤1.68×10-4
ASTM D 696
Mixed density/kg·L-1
1.149
Shore hardness (D type)
77±3
GB/T1241 1
Impact strength (unnotched)/kJ·m-2
≥21
GB/Tl043
Tensile strength/N·mm-2
38±7
GB/Tl040
Elastic modulus/N·mm-2
≥1600
Elongation after breaking/%
80
Third, heat insulation data inspection
The quality of the insulation data directly affects the overall quality of the aluminum alloy insulation profile. Therefore, inspection of insulation data is necessary. However, because the inspection of the thermal data part functions is more cluttered and the inspection time is longer, generally only the functions in table 6-4-1 are checked, while the functional goals in table 6-4-2 and table 6-3-4 are checked. For reference only, the inspection statement must be provided by the insulation material manufacturer. Inspection of insulation data is checked as raw and auxiliary data of the company, and inspections are conducted before use. The same standard and the same purchase time are in one batch. The inspection items and sampling rules are shown in Table 6-4-4.
Table 6-4-4 Insulation Data Inspection Project and Sampling Demand Table
Inspection items
Checking nature
Sampling rules
Appearance quality
Scale error
Room temperature tensile test
Water immersion experiment, hot and humid experiment
Brittle test
Stress cracking test
Into the factory inspection
Into the factory inspection
Into the factory inspection
Method check
Method check
Method check
L% per batch, not less than 10
L% per lot, no less than l0
Each batch of l0 roots, each l
Each batch of 20 roots, each l
Each batch of l0 roots, each l
Each batch of l0 roots, each l
1. Appearance quality and scale error checking
The heat insulation data should be lubricated and flat with no defects such as sag, bulge, crack, and no sawtooth on the corners. The strip heat insulation strip can be directly inspected. For polyurethane and rigid polyurethane foam, first Pouring into small specimens and checking their appearance quality.
For polyurethane and rigid polyurethane foam, it is not necessary to check the scale error. The dimensional error of the strip heat insulation strips is checked with a micrometer of the appropriate accuracy, and changes in the dimensions of the insulation strips should be taken into account when checking.
2. Room temperature transverse tensile test
Because of the special nature of heat insulation data forming technology, it is necessary to go through a period of functional stability and adaptation period after molding. To ensure the reliability and accuracy of experimental data, the heat transfer data must be adjusted before the functional inspection. That is, the insulation data should be stored in the laboratory at room temperature (23°C ± 2°C) and humidity of 50% ± 10% for 24 hours, and the tests should be conducted later.
In order to ensure the comparability of the inspection data prior to the horizontal room temperature stretching test, to ensure the comparability of the inspection data, the sample was first dried, and the sample was dried in an 80% oven for 8 hours and naturally cooled in a dry box until Room temperature is followed by a tensile test. Because the moisture content of the insulation bar is different, its horizontal tensile strength at room temperature is not the same.
"Transverse stretching" refers to the application of a transverse tensile load in the direction of the cross-section of the parallel sample. The longitudinal tensile load is not applied in the direction of the cross section of the straight specimen. Transverse tensile testing is primarily to check the data against lateral separation.
The experimental equipment is equipped with a tensile machine, and the fixtures of the transverse tensile test can be planned according to the different shapes of the data. There are generally two ways: one is to puncture the sample into the fixture for stretching; the other is to grip the sample directly (lateral) drawing (this method can sometimes be difficult because of thermal data constraints Clamping). Generally, because the specimen is strip, it will cause difficulties for the fixture, and the experiment can be performed smoothly. It is advocated that the length of the specimen can be selected within 20 to 35 mm.
The room temperature transverse tensile test process is as follows:
1) Ten specimens were stored in a room temperature (23° C.±2° C.) and 50%±10% humidity in a laboratory for 24 hours (condition conditioning), and the PA66 heat-insulated strips were first subjected to boring treatment.
2) At room temperature (23 °C ± 2 °C) transverse tensile test at a tensile rate of 1 mm/min ~ 5 mm/min. It is necessary to carry out experiments on one sample and one sample, and they cannot be combined together for experiments.
3) The process of accounting for transverse tensile eigenvalues ​​is as follows:
(1) Calculate the larger tensile force that can be accepted on each unit length of the sample. Q=Fmax Greater tensile force (N)/L sample length (mm).
(2) Calculate the average value of the larger tensile force that can be accepted on the length of 10 sample units. Q = (Q1+Q2+Q3+Q4+Q5+Q6+Q7+Q8+Q9+Q10)/10.
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