Common tests for corrugated box production

为使影响纸箱材质的性能各种条件尽可能标准化,需要对各种条件进行合理有效的控制。测试通常是在室内50%的相对湿度和23℃温度下进行的(英标)。试样应在测试前24小时内妥善放置。

1.吸水性测定

公认的检测方法是Cobb法,不过该法仅适用于面纸。先把两端张开的金属环或圆筒夹在既定区域和重量的纸张上,使纸张有效地闭合金属环或圆筒的一端。测好定量的水(通常为25ml)倒入蓄水区,规定时间过后将残余水倒掉。这时重新称量一下纸张试样,知道前后重量差便可算出吸水率,以此来比较不同面纸的吸水性。通常规定的测试时间约为一分钟,只有纸张吸湿性特别强时才会调整时间。

而水滴测法可适用于所有纸张。此法较为容易,只是结果不够精确,不过可随时随地进行测试,对不同纸张作比较。通常先在纸上画个圆圈作标记,将量好的少量水滴入圆圈中央,通过测定吸水时间即圆圈湿透的时间来计算纸张的吸水性。

2.透气度测试

常用方法为Gurley测试法,仍需测定时间,不过这次测定的是在规定气压下,定量空气通过纸张上的规定区域(此处用作一层隔膜)的时间。

纸张上的固定区域是由环规来界定的。随后压缩空气在规定气压的压力下穿过这层“隔膜”,渗透的气体量可用测压计测得。透气度常用“毫升/分”作单位表示。

Corrugated box production common test layout 1

3.环压强度测试

测试时,把纸板放入一张厚钢板的环形槽中。钢板是平放的,纸带的长度正好可沿其环形槽围成一个卷筒。纸卷上方再放一张水平的钢板,随后再不断向纸卷施压直到把纸卷压溃。施加的压力即为该纸的RCT指数,通常以“牛顿”作单位。此法主要用于测试面纸,不过也可尝试用来测试瓦楞芯纸。这些纸张的RCT指数可为今后形成的纸板的最终边压强度提供很好的参考。

4.瓦楞纸压缩强度测试

本法专门用于测定瓦楞纸。如同在瓦楞芯纸平压强度测试(CMT)中一样,纸张通过冷压式瓦楞芯纸成形机后成为和瓦线上一样的芯纸。如同上文提到的RCT测试程序,成形芯纸也要受到压力,在被压溃的一瞬间可算出其抗压度。

5.短矩压缩强度测试

Neither the RCT test nor the CCT test can be repeated, because the shape or vertical state of the paper may change when it is pressed, and the test results will not be very accurate. Therefore, in order to maintain the consistency of the test, people have developed a test method for short-moment compressive strength of paper. By firmly clamping the 15 mm wide paper tape flat with two splints, leaving a gap of 0.7 mm free paper in the middle. One of the splints moves to the other splint along the paper tape plane under hydraulic pressure, squeezing the narrow paper tape in the middle, and it is still necessary to measure the pressure when the paper is crushed. The test can be done in both machine direction (MD) and machine cross direction (CD).

6. Flat compression strength test of corrugated core paper    

In the early stage of corrugated board production, people in the industry believed that it was necessary to measure the flat compression strength of different corrugated medium paper, so the corrugated medium paper test device came into being. The core paper can be made by putting the paper tape into a cold-press core paper forming machine which has a similar function to that of a single-facer. The core paper can also be formed under the action of hot rollers on the single-sided machine, but it must be stored for a period of time after the tape is attached. Tape is used to imitate single-faced cardboard to ensure that the core paper does not deform after being removed from the single-facer. This single-sided paper tape can then be put under pressure and can also be used for RCT and CCT tests. After the tape is compressed, there are two possible crushes in the CMT test - either the corrugation "unfolds" or the sides are damaged. In this way, the core paper and the face paper can be compared and tested. Similarly, the single-sided paper actually produced on the single-sided machine can also be used for testing to compare the actual value and theoretical value of CMT.

To carry out the "hot core paper" test, the sample paper is passed through the hot single-facer corrugating roller, then placed between the plywood, and the above steps are repeated.

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