How is the width of the molecular weight distribution of polypropylene controlled?
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In actual production, how is the width of the polypropylene molecular weight distribution controlled?
In chemical production, the distribution of molecular weights is adjusted by controlling the amount of H2~
Hydrogen is used to adjust the molecular weight of polypropylene, but how is the molecular weight distribution adjusted?
In the loop reactor process, the molecular weight distribution can be appropriately widened through the hydrogen difference between the two loops.
I wonder how other polypropylene production processes adjust the molecular weight distribution? How does the width of the molecular weight distribution of polypropylene affect its properties?
Materials with a wide molecular weight range have good flow properties, while those with a narrow molecular weight range exhibit good impact resistance
I’ve learned it! ! ! I’m not sure if there are any effective ways to regulate the width of the molecular weight distribution.
Yes, but the efforts are mainly focused on the main catalyst. It is said that metallocene catalysts are effective in controlling the molecular weight distribution of polypropylene, resulting in a very narrow distribution. Another aspect is controlling the reaction residence time of the main catalyst; in the case of AMOCO horizontal reactors, which operate in a near-piston flow regime, the molecular weight distribution is also relatively narrow. Hydrogen is used to adjust the molecular weight, and it is generally assumed that the molecular weight distribution is normal.
The length of the PP chains is part of what determines the performance of PP, namely the MFR. The shorter the chains, the higher the melt flow rate; the lower the molecular weight, the better the fluidity. However, the yield strength decreases. Adjusting the MFR mainly involves controlling the ratio of hydrogen to propylene, and the quality of the catalyst also has an impact on the melt flow rate
The distribution of molecular weight is influenced by three main factors: first and foremost, the reactor design – much effort is invested in this aspect for exactly this reason; secondly, the catalyst, which is actually greatly affected by the reactor, so each type of reactor in a given process comes equipped with its own catalyst; thirdly, hydrogen, which relates to the operational aspects and helps keep the molecular weight values within a certain statistical range