The temperature stiffness of high temperature nylon increases as the temperature of the mold is raised above its starting temperature. But, perhaps more importantly, the effect of mold temperature on the stiffness of the sample at high temperatures is examined. This shows that the crystallinity of the part will be reduced if the component is cooled too quickly.

As a result of our collaboration, I am frequently perplexed as to how much the process circumstances influence the final performance of the injection molded parts. The general consensus appears to be that the selected material exhibits the properties listed on the data sheet, but that these qualities are unrelated to the method by which the raw materials are transformed into molds.

When you think at it this way, the processor's duty is really just to heat the material up until it's a molten state, pass it through a suitable processing device, and then solidify the polymer into the shape that was originally printed. Providing the pieces fit the required aesthetics and the main dimensions are within the printing specifications, the processor can complete the work. The material provider is responsible for the ownership of the property.

Unfortunately, it is not as straightforward as that. For example, in plastic injection molding, the molding circumstances will have a substantial impact on the final performance of the material, regardless of how the item is designed. Melt temperature and die temperature are the two technological parameters that have a substantial impact on the properties of the polymer and are discussed in detail below.

First and foremost, it is critical to distinguish between these process conditions and the set points that we utilize to regulate them. The melt temperature of a polymer is the temperature at which it really melts when it leaves the nozzle and enters the mold. The barrel set points reflect the tools that we employ to attain the required melt temperature, but they are not the same as the melt temperatures themselves.

When determining the actual melt temperature, the mechanical work, residence duration, and the quality of the screw and barrel are all critical factors to consider. Furthermore, the real-time surface temperature of the mold core and cavity is related to the temperature of the fluid traveling through the channel in the mold, although the two are not always the same in every case.

Assuming that has been established, we can investigate the relationship between these two parameters and the properties of the polymer. It is commonly accepted that the melting temperature has an effect on the viscosity of a substance. However, the ultimate molecular weight of the polymer in the molded pieces is affected by the melt temperature as well as the mold temperature.

For example, in an experiment involving components molded with polypropylene, the polymer in the component molded at a melting temperature of 400 degrees Fahrenheit (204 degrees Celsius) has a significantly higher average molecular weight than the polymer in the component molded at a melting temperature of 480 degrees Fahrenheit (204 degrees Celsius) (249 C). Overall, this results in increased impact resistance, reduced energy consumption, and a reduced overall cycle duration.

Although the effects of die temperature on final performance may not be immediately apparent, it frequently has a bigger impact than previously thought. Higher mold temperature results in decreased mold stress in amorphous polymers (such as ABS and polycarbonate), which results in improved impact resistance, stress cracking resistance, and fatigue performance.

Mold temperature is a significant element in determining the crystallinity of semicrystalline materials because it influences the crystallinity of polymer. Many performance criteria, such as creep resistance, fatigue resistance, wear resistance, and dimensional stability at high temperatures, are influenced by crystallinity in a variety of forms. The crystal can only be created when the polymer is heated to a temperature lower than its melting point but higher than its glass transition temperature (TG).

Time required for crystallization

To ensure that semi-crystalline materials crystallize for a sufficient amount of time when molded, the optimal mold temperature will be greater than the transition temperature (TG). Figure 1 illustrates the differences in performance between high temperature nylon (PPA) when molded at the optimum mold temperature and when molded at a lower mold temperature. The relationship between the modulus of the material and temperature is depicted in the diagram. When the mold temperature is raised, the stiffness of the material increases at ambient temperature, as well as when the mold temperature is decreased.

There is a bigger disparity between samples that were molded at the right temperature and samples that were formed at the lower mold temperature when testing at higher test temperatures. When the material is between 130 and 140 degrees Celsius, the modulus of the molded material begins to fall at lower temperatures, and the modulus reduces further and further at lower mold temperatures as C approaches the glass transition area. The processor is in charge of determining how the system will behave.

ABS's impact qualities are determined by the interaction between the mold and the melt temperature. ABS is an amorphous polymer that is typically chosen for its toughness. When the die temperature is changed from 29 to 85 degrees Celsius (85 to 185 degrees Fahrenheit) and the melt temperature is changed from 218 to 271 degrees Celsius (425 to 515 degrees Fahrenheit), the profile captures the impact resistance of the dart. Some people may be surprised to learn that the impact resistance ranges from less than 2 nanometers (1.4 ft lb) to approximately 50 nanometers (36.5 ft lb) only because of these differences.

The most important factor is the temperature of the die. The best results, on the other hand, can be produced by combining a higher die temperature with a lower melt temperature. The appropriate range of processing conditions, as well as the situations that should be avoided, are clearly depicted in the illustration.

This is a characteristic of all polymers, including polyethylene. Lower melt temperatures combined with higher mold temperatures often result in the optimum performance in most cases. Unfortunately, this is the polar opposite of what we typically see in the manufacturing shop.... When a melt temperature is higher than the optimal temperature, it is often believed to be the only accessible tool for reducing the viscosity of the melt, rather than the opposite. A higher melt temperature increases energy consumption, degrades polymers, and lengthens the amount of time it takes to cool down items to their final dimensional stability.

The processor will rely on the lowered mold temperature to make up for the decreased production as a result of the increased cycle time. However, the lowered melt temperature and higher die temperature typically result in parts that have the same or shorter cycle time and better mechanical characteristics than the parts produced at the higher melt temperature. When processors understand their involvement in the development of polymer characteristics, they will construct processes in totally diverse ways, ultimately resulting in cost reduction and quality improvement.