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Measures to Improve Heat Resistance of Bottles

1.Choose a reasonable preform and bottle design. The optimized preform shape design and bottle mold design help to improve the wall thickness distribution of the bottle and avoid distortion or shrinkage deformation in different areas of the bottle body;

2.Preform injection cooling time control. Strictly control the cooling time of the preform injection, so that the preform can be demolded as soon as possible. In this way, the molding cycle can be shortened and the yield can be increased, and spherical crystallization can be induced due to the higher residual temperature. The crystal diameter of spherical crystal is extremely small (only 0.3mm ~ 0.7mm), which does not affect the transparency;

3.Strictly control the process parameters of injection, drawing and blowing and the temperature distribution in each area to avoid the deformation of the bottle caused by the release of residual stress at the PET glass transition temperature (>75°C).

4.The application of blowing mold temperature adjustment technology. Usually, the hot oil circulation method is used to heat the blowing mold. There are three cycles for the temperature adjustment of the blowing mold: The bottle body hot oil circulation. Heat the blow mold to 120°C to 145°C. In this way, the temperature difference between the preform and the blowing mold cavity is reduced, which promotes further crystallization. Extend the bottle blowing and pressure holding time, so that the bottle wall and the cavity are in contact with each other for a long time and have sufficient time to improve the crystallinity of the bottle body to about 35% without destroying the transparency. Mold temperature below 100°C has little effect on the crystallinity of the bottle body, because the crystallisation of the bottle body occurs above 100°C. Cooling water circulation at the bottom of the bottle. The bottom of the bottle should be kept at a low temperature (10℃~30℃) to avoid excessive crystallization and whitening of the unstretched bottom part of the bottle. Bottleneck temperature adjustment (optional). The non-crystalline bottle finish has been completely cooled since it was released from the injection mold. Most of the non-crystalline bottle mouths are designed to strengthen the bottle mouth (increase the wall thickness of the bottle mouth), thereby improving the sealing performance and avoiding the deformation of the bottle mouth during the capping process. Usually, the ovality of the bottle mouth after filling is controlled within 0.2mm, and the shrinkage rate of the outer diameter of the thread is less than 0.6%.

5.Circulation blowing technology. When using a hot blow mold, how to control the deformation of the bottle after demolding is very important. Before the bottle blowing mold is opened, air is blown in and the cycle is evacuated, and the bottle body is cooled and shaped, so as to control the deformation amount after demolding. The air intake of the circulating cooling air passes through the same channel as the primary blowing and secondary blowing, but is exhausted from the small hole in the head of the drawing rod through the drawing rod. The circulating air blowing time is about 0.5 seconds to 2 seconds. Therefore, the high-pressure air consumption of the heat-resistant bottle making machine is much higher than that of the ordinary bottle making machine.