Design of Test Plan for Composite Strength of Film-Coated Products (I)

Editor's Note: For the quality requirements of the book cover film, the relevant industry standard CY/T28-1999 "binding quality requirements and test methods - paperback," there are many provisions, other types of film products, can refer to this requirement Conduct quality assessment. However, the standards for inspection methods are relatively general and are not convenient for actual operation. In this series of quality requirements, the fastness between the paper and the plastic film, that is, the composite strength of the film-coated product has a great influence on the overall quality. For this factor, the design of the test plan was carried out in order to provide a quantifiable and operable evaluation method for the quality inspection of the coated product.

1 Introduction

Film-covered products, that is, printed products that have been processed by laminating, mainly refer to the combination of plastic film and printed paper or paperboard, which is formed by bonding and/or hot-melt adhesives, followed by heat and pressure. . There are two main production and processing processes: pre-coating process and coating process. The application of laminating technology covers a wide range of applications, such as the covers of books and magazines, albums, various documents, advertising brochures, posters, color printing cartons, and other paper products, and often uses a lamination process for surface treatment and processing to achieve better results. Appearance effect. In general, film-covered products have the following features in comparison with general paper-based prints: the surface is smoother and brighter, the gloss is higher, the graphic and text are more vivid and three-dimensional; tear resistance, abrasion resistance and resistance High folding performance; good waterproof, anti-fouling, chemical corrosion resistance.

2. The meaning and influencing factors of the composite strength of film products

The so-called “composite strength” of film-covered products is, in a nutshell, the adhesive fastness between plastic film and paper (board) prints in film-covered products, and its size depends on plastic films, paper (board) prints and adhesives ( Or the size of the adhesive force between hot melt adhesives). When the film is covered, the adhesive force mainly comes from the mechanical bonding force and the physical chemical bonding force between the plastic film, the paper (board) print and the adhesive (or hot melt adhesive).
There are many factors that affect the composite strength of film-covered products, including objective factors such as paper, printing inks, plastic films, adhesives (or hot-melt adhesives) and other production materials, as well as coating process parameters, printing process, etc. Human subjective factors can be controlled.

The various types of production materials covered by film-covered products are the basic factors that guarantee the quality of the film. In the selection and use, to make their combination will help improve the composite strength, and then improve the overall quality of the film products. At the same time, once the production materials are selected, the influence of these objective factors on the composite strength can be basically determined. Therefore, for coated products, the choice of production materials is critical.

Since the lamination process is a surface finishing process for the printed matter after printing, the composite strength of the laminating product is affected not only by the process parameters in the lamination production process, such as the temperature, pressure, and speed of the lamination process. , adhesive coating conditions, film tension and environmental factors, etc. At the same time, it is also affected by the printing process, that is, the surface state of the printed product after printing, such as ink layer thickness, graphic area and distribution, ink characteristics , Dilute agent usage, dusting usage, ink drying, and more. All of these factors will affect the mechanical bonding force between the paper (board), the plastic film and the reducing agent (or hot melt adhesive), and the formation conditions of the physical-chemical bonding force, which will cause changes in the adhesion state between the printed matter and the plastic film. This affects the composite strength of the filmed product.

In short, the composite strength of film products is the result of various factors, and it is also an important parameter for the quantitative evaluation of film quality. Therefore, according to the existing experimental equipment, with reference to the relevant national standards and industry standards, it is of great significance to design an operational experimental program and perform more accurate and scientific tests on the composite strength of the covered products.

3, the design of the test program

Any kind of test plan must have the theoretical basis for testing, reliable test equipment and feasible test methods.

3.1 Theoretical Basis, Reference Standards, and Requirements for Test Equipment

Film-covered products can be regarded as a kind of composite material formed under the specific conditions of paper (board) and plastic film through adhesive or hot melt adhesive. For composites, peel strength is an important quality evaluation index. That is, under certain test conditions, using a specific test equipment, a sample of a specified size is subjected to T-peel at a certain speed, and the average peel force between the composite layers is measured. The composite strength of film products can be expressed by the peel strength between paper (board) and plastic film.

For the determination of peel strength, reference can be made to the relevant national standards, the most important being the national standard GB/T 2791-1995 "Test method for adhesive T-peel strength" "Flexible material for flexible materials" and national standard GB/T88O8-1988 "Soft composite plastic material peel test method." In the test plan design and pre-testing process, the sample to be tested is often turned up or down, and the theoretical “T” shape cannot be formed (ie, the unpeeled part of the sample and the peeled part form a “T” type. ). If you manually fix the sample and move it along with the sample to force the sample to form a “T” shape, it will affect the size of the peel force and affect the final test result. GB/T2791-1995 clearly stipulates that the "T" peel test for "flexible material" versus "flexible material" is to apply a peel force at the unglued end of the sample, causing the sample to peel along the adhesive wire. The angle between the applied force and the glue line may not be controlled, that is, the peeling may be performed in a free state to detect the force value without having to control the angle. For coated products, paper and paperboard, which are often coated, can be regarded as "flexible materials." Therefore, the coated products can be regarded as "flexible materials" and "flexible" in most cases. For composites of "sex materials", the composite strength (peel strength) can be measured by referring to the standard.

In the testing process, the abnormal jumping of data at the beginning of the test and at the end of the test often occurs, which is mainly affected by the fluctuation of the peeling force at the beginning and the end. In order to improve the accuracy and reliability of the test results and meet the relevant provisions of the two national standards referenced, the test equipment selected is best able to reasonably screen the test data and effectively eliminate data from the beginning and end of the period. It does not participate in the calculation of the result to eliminate the influence of this unstable factor.

3.2 Test Equipment Selection and Adaptability Introduction

The relevant standards stipulate that the test equipment should use a tensile tester with a graphic recording device or other device that can meet the requirements of this test. According to this provision, and taking into account the special requirements mentioned earlier, this design plan uses the “XLW Series” intelligent electronic tensile testing machine. The device mainly has the following features:

(1) Meet relevant standards. "XLW Series" intelligent electronic tensile testing machine designed and manufactured in accordance with GB/T17200-1997 national standard technical requirements, its performance in line with national standards GB/T2791 - 1995 "Adhesive T peel strength test method (flexible material to flexible material)" And the national standard GB/T88O8-1988 "soft composite plastic material peel test method" requirements. At the same time, it can also meet the requirements of many other national standards and conduct other tests.

(2) It has a unique “skull and tail” function that can more accurately reflect the real situation of the test. During the test process, the recording device of the test equipment properly screens the data obtained from the test results, ie, the data measured at the beginning of the stripping of 25 mm and the stripping of 10 mm before the stripping are excluded and does not participate in the calculation of the test results. In this way, the effects of fluctuations at the beginning and end of the test on the test results are eliminated, and the conditions of the test can be more accurately reflected.

The curve represents the change in the size of the peel force. The person indicates the effective test range (ie, the range of the participating data calculation). Although the test data of the first 25 mm and the rear *mm can be displayed, they are not involved in the calculation of the final test result.

(3) Easy to operate and use. The whole machine adopts high-tech mechanical and electrical integration and is equipped with an easy-to-control operation panel; LCD large-screen liquid crystal display; the operation process is simple and easy to master; the test results can be alternately displayed on the screen, and can also be directly printed out; with RS232 Interface, which can be connected to a computer for further processing of the data (with related software). These features are suitable both for simple testing by general technicians and for deep research by researchers.

In summary, the "XLW Series" intelligent electronic tensile testing machine not only satisfies the requirements of the relevant standards, but also meets some special requirements for the measurement of the composite strength of the laminated products. It is an ideal test equipment.