Effectively control factors affecting composite quality
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Ex ante control
Pre-existing control is the detection and control of raw materials in order to avoid the occurrence of quality problems. In order to truly control beforehand, each batch of raw materials must be carefully inspected according to certain national behaviors or enterprise standards, and raw materials that do not meet the standards are not used.
Thinners, glues, films, inks and other raw materials, the indicators and testing methods required by national standards are as follows:
(1) Detection of thinner
The diluent refers to a solvent used in the compounding process, that is, ethyl ester, toluene, acetone, methyl ethyl ketone, and the like.
1 Index: The water content should not exceed 0.2%, and the total purity should not be lower than 99% (according to GB3728-91).
2 Control method: Using gas chromatograph, using nitrogen as carrier gas, thermal conductivity detector, peak height and concentration, the working curve is obtained, and then the corresponding peak height is obtained by sampling each batch of solvent under the same conditions to obtain the concentration.
3 specific operations:
A. Gas chromatograph: the temperature of the chamber is 250 ° C, the temperature of the detection chamber is 200 ° C, the temperature of the column chamber is 150 ° C, and the porous cells of the polymer are used as the column packing;
B. Distillation and chemical purification of analytically pure reagents. (Different purification methods for various solvents);
C. Using a solvent that has been purified and water to prepare a standard solvent having a combined water content of 0.02%, 0.05%, 0.1%, 0.15%, and 0.2%;
The injection volume is 0.1ml, and under a certain bridge current and attenuation, the response peak of water is obtained, and the peak height of water is plotted against the concentration to obtain a working curve;
D. Each batch of raw materials was sampled, and under the same conditions, the same injection was carried out, and the peak concentration was used to obtain the corresponding concentration in the working curve, which was compared with the standard;
E. Every time you start the test, you must do a work curve, regardless of whether the conditions are the same as before;
F. Also prepare a solution with a purity of 100%, 99.8%, 99.5%, 99.2%, 99%, the injection volume is 0.1ml injection, the peak height of the measured diluent is obtained, and the peak height is plotted against the concentration to obtain a working curve. Then, the peak height is also taken by sampling, and the corresponding concentration is obtained according to the working curve.
(2) Control of polyurethane glue
1 Polyurethane adhesives have different uses, no common testing standards, but have common testing methods;
2 Solid content: GB2793-81, using the weight loss method to test the content of non-volatiles in the polyurethane glue.
Specific operation: Take 3 clean and dry surface plates, each accurately weighed about 2.00g, recorded as M1, put in a drying oven at 80 °C for 2-3 hours, weighed as M2, twice weighing ratio M2/M1×100% is the solid content.
3 Viscosity: The viscosity at 25 ° C was measured by a rotational viscometer according to GB279481. The specific operation is as follows: the sample gel is heated at 25 ° C for 0.5 hour or more, and the appropriate rotary viscometer rotor is selected for testing according to the viscosity provided by the supplier.
4 Acidity: According to GB/1 1458-83, it can be measured by glass electrode acidity meter, and the pH value can also be detected by precision test paper.
The specific operation is: igniting the activated glass electrode in the sample chamber and titrating the acidity to the end point.
5NCO value: The NCO value of the curing agent was measured by chemical titration according to the detection method of polyisocyanate.
The specific operation is:
A. Preparing the reaction solution: analytically pure hexahydropyrazine: acetone = 1:50;
B. Weighing about 2.00g of curing agent into a 250ml Erlenmeyer flask with 10ml of acetone;
C. Add 25 ml of the reaction solution and let stand for 15 minutes;
D. Add 20ml of absolute ethanol and 7 drops of bromine blue indicator;
E. Titrate to the end point with 0.5 ml / L ethanol solution;
F. At the same time, a blank experiment was performed to obtain an NCO value.
(3) Detection of the membrane
1 indicator: transparency, uniformity, etc. can be determined by visual inspection;
2 escape auxiliaries: GB100488, the content of which is detected by gas chromatography, and can also be qualitatively determined by heating after smelling according to actual production needs;
3 Surface tension: The film after corona treatment is detected by Dyne pen, but the dyne pen is not accurate after a long time of use, and the potion test can be used.
The specific operation is as follows: using the analytically pure formamide and ethylene glycol ether in a certain proportion to obtain the syrup, according to whether it is continuous on the film to determine whether the film meets the requirements.
4 Ink: Because the ink is printed differently, the pigment, binder and solvent of the ink are different, so the control of the ink is different, but in general, it can be from acidity, viscosity and chromaticity. In terms of the needs of the manufacturers.
In addition to the detection and control of raw materials, there is an operating process and appropriate use problems, such as:
A. To make the retort-resistant composite bag, it is necessary to use the retort-resistant ink glue and film. If ordinary ink, glue or film is used, the quality of the composite bag cannot be achieved. However, these inks, glues or films are not unqualified raw materials and need to be used properly. A similar situation is that some manufacturers use external inks to represent the printing ink and isopropyl alcohol as the diluent for the printing ink. Since the film after printing of the ink is to be composited, and the isopropanol contains active hydrogen, the effective group in the curing agent, isocyanate group (N-G-O), is consumed. Causes poor adhesion and glue to dry.
B. Preparation and guarantee of glue: When using two-component polyurethane, it is necessary to mix the main agent, curing agent and diluent in a certain ratio and in a certain order. If the compounding is not carried out in an appropriate ratio, the hydroxyl group in the main agent and the isocyanate group in the curing agent are basically not reacted in proportion, resulting in incomplete reaction, which affects the bonding strength. If the compounding agent is used first, the main agent is used. Mixing with the curing agent and adding thinner may cause surface quality problems after compounding. Therefore, the order of the glue can not be changed. It is necessary to first add the diluent to the main agent or the curing agent, and dilute the main agent or the curing agent to mix the two together. The reaction rate is much faster when the concentration is large. After the dilution, the reaction rate is slow, so that excessive molecular groups are not formed locally. Similarly, if the glue is not used within 8 hours, and it is not sealed and stored frozen, the surface quality of the composite product may also occur when mixed with the glue. The above two examples are used to illustrate: the use of appropriate raw materials, the correct operating process and the raw materials of the standard complement each other, together constitute the cornerstone of excellent products.
Post hoc detection and analysis
Ex ante control is the behavior before printing compounding, and post-testing and analysis is the testing and analysis of composite products. The purpose is to test whether the products are qualified, and to analyze the unqualified products, to absorb the experience and ensure the full product of the products in the future. rate.
The method of testing the finished product. For composite manufacturers, the inspection of the finished product should include the measurement of the composite film, the peel strength and heat seal strength of the bag, the detection of the residual solvent content of the composite film, and the comprehensive analysis of the quality problem.
(1) Peel strength and heat seal strength of composite bag: Due to different end use of composite film bag, its index is different. The method is tested by electronic tensile machine according to GB8808-88. For composite film, it is cut into 15×200mm slender. After the strip was peeled off by 5 mm, the tensile force was gradually increased by an electric tension machine, and the peeling test was performed for the heat-sealing strength of the composite wire to be cut into 15 × 100 mm.
(2) Residual solvent content of the composite membrane: It is detected by gas chromatography according to GB1004-88, and the content is not more than 10 mg/m2.
A. Hydrogen turret detector, using nitrogen as carrier gas, gas room temperature 120-150 ° C, column chamber temperature should not be lower than 80 ° C, the difference between the two room temperature is not lower than 50 ° C;
B. Take 1 ml and 2 ml of solvent, respectively, placed in a 500 ml flask with a silicone plug preheated at 80 ° C for 30 minutes, and heated at 80 ° C for 30 minutes;
C. Take 1ml sample, inject, and obtain solvent peak;
D. Plot the height to the mass to obtain a standard curve;
E. The mixture was quickly crushed into a 500 ml conical flask at 80 ° C for a 0.2 m 2 composite film, and the silicone plug was capped. Heat at 80 ° C for 30 minutes. Take 1ml sample, inject, and obtain solvent peak;
F. Find the corresponding quality on the standard curve.
(3) Comprehensive analysis of composite film quality problems: Using the above instruments and methods, combined with observation phenomena, can make a correct discrimination of quality problems and find out the correct cause.