How’s the process technology affect the Properties of Polycarbonate Composites?

Composite technology is an important technology developed in the field of polymer modification in recent years. The addition of a light diffuser to the polymer matrix through different processing processes will have an impact on the properties of materials. In addition, in the actual production, it is obvious that the cost will be greatly increased by using the direct addition method to prepare the composites. Therefore, studying the effects of different processing processes on the properties of the composites can achieve the purpose of improving the properties of the materials and reduce the cost. In this paper, the KMP590 of 2.2um particle size was used as the filler of PC, and the effects of different processing processes on the optical properties and micro-morphology of the composites were studied by changing different processing processes and comparing with the twin-screw masterbatch method.

3.1 experimental materials and equipment

3.2 Instruments and equipment

Electrothermal oven, twin-screw extruder, plastic granulator, plastic injection molding machine, light transmittance/fog tester, single screw extruder, grinder, electro-optic analytical balance

2 sample preparation

Direct addition method: directly put the mixture of PC and photo-diffuser into the twin-screw extruder to prepare the particles (PC-kmp590-d-x, PC-kmp590-ti-d-x, X is the content of photo-diffuser added, the content of Tio2 is unchanged, it is 0.05% all the time, extrusion process, the temperature of one zone is 210 ° C, the temperature of two zones is 230 ° C, the temperature of three zones is 240 ° C, the temperature of four zones is 240 ° C, the temperature of five zones is 240 ° C

240 °C, 6 zone temperature 240 °C, 7 zone temperature 250 °C, rotate speed 100-500 r/min. After the particles are dried, the injection process is tested on the injection molding machine. The temperature of the injection molding machine is set as 315 ° C in zone 1,320 ° C in zone 2,320 ° C in Zone 3 and 325 ° C in Zone 4. After the injection molding is completed, the spline is tested for its performance.

Single screw masterbatch method: accurately weighing each raw material composition according to weight percentage, after fully mixing polycarbonate and light diffuser (1:10) , adding mixer, mixing for 8 minutes, cooling, crushing with the crusher to prepare light diffusible masterbatch MKMP590, the internal mixer is set at 230 °C in zone one, 240 °C in zone two and 250 °C in zone three. Accurately weigh each raw material composition according to the weight percentage of the formula shown in table 3.3, the PC-MKMP590-X composite particles were prepared by mixing polycarbonate and light diffusible masterbatch in a single-screw extruder. The temperature of the extruder was set at 230 °C in 41 regions, the temperature of the second zone is 250 ° C, the temperature of the third zone is 250 ° C, the temperature of the fourth zone is 250 ° C, the temperature of the fifth zone is 260 ° C, the temperature of the sixth zone is 260 ° C, the temperature of the seventh zone is 260 ° C, the temperature of the die head is 260 ° C, the rotating speed is 80-500 r/min. After the particles are dried, they are injected into the injection molding machine to form the test sample strip. The temperature of the injection molding machine is set as 335 ° C in zone 1,350 ° C in zone 2,350 ° C in Zone 3 and 355 ° C in Zone 4. After the injection molding is completed, the spline is tested for its performance.

Table 3.3 Experimental formula of PC/KMP590 composite

3.3 testing and characterization.
1. Optical test.
Using light transmittance/haze tester (EEL57D, Shanghai Precision instrument Co., Ltd.), test according to GB/T0-2008, sample size 50mm X 50mm X2mm, formula see 2-1 ~ 2-2.

2. Microstructure characterization.
The dispersion behavior of light diffusion agent in PC matrix was observed by scanning electron microscope. The splines were cooled in liquid nitrogen for about 5 minutes, and then manually quenched, the cross-section was cut off and glued to the glass slides, and then observed after gold spraying.

3. Burn residue test

Accurately weighing a certain amount of light diffusion masterbatch, and then put into the box-type resistance furnace, burning at 600 °C for 4 hours after taking outweighing, thus determining the burning residue.

Actual content% = amount after burning/amount before burning * 100%

4. Deviation analysis.
The deviation of general data can be divided into average deviation and standard deviation. The average deviation is also known as the arithmetic mean deviation, and its expression is as follows:

In the formula, D is the average deviation, x is the value of any measured results, x is the average value of N measured results. It is simple to use average deviation to express precision, but a large deviation can not get a proper response.

The standard deviation is more sensitive than the average deviation to reflect the existence of the large deviation, so it can reflect the precision of the measurement better:

In the formula, S is the standard deviation, x is the value of any measurement results, and x is the average value of N measurements.

3.4 results and discussion

3.4.1 Table 3.4 Experimental data of masterbatch calcined residue

Table 3.4 experimental data of ignition residue of light diffusion masterbatch prepared by the internal mixer. As can be seen from the diagram, the actual proportion of the light diffuser in the light diffuser masterbatch is close to the theoretical proportion (the error range is less than 0.6%) . The content of photo-diffuser in masterbatch MKMP590 is 9.51 wt%, which makes the content of photo-diffuser in PC photo-diffuser more accurate.

Analysis of optical properties of 3.4.2 optical diffusion composites

Fig. 3.1, fig. 3.2, fig. 3.3 and Fig. 3.4 are the transmittance and fog analysis of KMP590, KMP590/Tio2 light diffusion composite prepared by the direct addition method.

Fig. 3.3 shows that the transmittance of the composite decreases with the increase of the content of KMP590. When the content of KMP590 is 2.0%, the transmittance is 55.4%. The average deviation of repeated experiments is between 2.467% and 3.789%, the standard deviation ranges from 3.504% to 4.526%. As can be seen from Fig. 3.4, with the increase of the content of KMP590, the fog of the composite increases. When the content of KMP590 reaches 2.0%, the fog is 90.8% and the average deviation of repeated experiments is between 2.072% and 3.453%, the standard deviation ranged from 3.204% to 4.532. The repeated experimental data showed that the direct addition process was unstable, the deviation of repetition number was large, the average deviation and the standard deviation were much larger than that of the double-screw Masterbatch process, which was about 2.00% more.

Figures 3.5 and 3.6 show the transmittance and haze analysis of the light-diffused composite prepared by the single-screw masterbatch method

As shown in figure 3.5, with the increase of KMP590 content, the light transmittance of the composite decreases. When the KMP590 content reaches 2.0%, the light transmittance is 54.9%. The average deviation of repeated experiments is 0.817%-2.789%, and the standard deviation is 0.992%-3.542%. As can be seen from figure 3.6, with the increase of KMP590 content, the haze of the composite increases. When the KMP590 content reaches 2.0%, the haze is 91.8%. The average deviation of repeated experiments is 0.887% 1.241%, and the standard deviation is 1.064% 1.741%. The repeated experimental data show that the process stability of the single-screw masterbatch method is good, and the average deviation and standard deviation of the repeated data are slightly worse than that of the twin-screw masterbatch processing method, which is about 1.00% more than that of the twin-screw masterbatch processing method.

3.4.3 SEM Image Analysis of Optical Diffusion Composites.
Whether the optical diffuser is uniformly dispersed in PC matrix is one of the important factors affecting the optical properties of PC composites. The SEM images of light diffusion composites prepared by different processing processes were analyzed.

The SEM of the cross-section of the composites prepared by different processing processes is shown in figure 3.6. It can be seen from the figure that the light diffusion agent is uniformly dispersed in the PC matrix and the shape of the light diffusion agent is kept intact when the masterbatch prepared by the dense mixing mechanism is compounded with PC, while the SEM image of the composite prepared by the direct addition method shows that the light diffusion agent is not well dispersed in the PC matrix, and the light diffusion agent has agglomeration phenomenon, which is similar to that in the literature.

3.5 Summary of this chapter.
In this chapter, the effects of different processing processes on the properties of the composites were discussed. the optical properties and process stability of the three kinds of composites were studied by direct addition method, single-screw masterbatch method, and twin-screw masterbatch method.

1. For the light diffusion composites prepared by the direct addition method, with the increase of the light diffusion dose, the light transmittance of the composites decreased to 56.5%, and the haze increased to 90.2%. From the repeated experimental data, the direct addition process is very unstable, and the data deviation is large. The standard deviation is between 2.509% and 4.532%. Through the SEM analysis of the composites, it is found that the light diffusion agent is not well dispersed in the PC matrix, and there is a phenomenon of agglomeration.

2. The light transmittance of the composites decreased to 54.9% and the fog increased to 91.8% with the increase of the light diffusivity dose, and the process stability of the composites by the single-screw Masterbatch method was good, the standard deviation is between 0.922% and 3.542% . Through the SEM analysis of the composite, it was found that the dispersion of the light diffuser in the PC matrix was good, the shape of the light diffuser was good, and there was no agglomeration.

Compared with the composite material prepared by the twin-screw masterbatch method, the standard deviation of the repeated experiment of the twin-screw master batch filling method is between 0.265% and 2.469%, and that of the single screw master batch filling method is between 0.992% and 3.542%, and that of the direct method is between 2.509% and 4.532%. Finally, it is concluded that among the three processing processes, the deviation of the twin-screw masterbatch method is the smallest and the process is the most stable.