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Bio-Based Polyester Polyols for Polyurethane Applications, Study notes of Engineering

Istanbul UniversityEngineering

This document delves into the synthesis of bio-based polyester polyols using a two-step polycondensation process. It explores the influence of catalyst amount on rheological behavior and examines the reaction characteristics, including the use of nitrogen atmosphere and reduced pressure. The document also analyzes the ftir and nmr spectra of the synthesized polyols, providing insights into their molecular structure and composition. The study highlights the potential of these bio-based polyols as sustainable alternatives in the polymer industry.

Typology: Study notes

2024/2025

Uploaded on 03/29/2025

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Study 2
-The title of the paper is 'Structure-Rheology Relationship of Fully Bio-Based Linear
Polyester Polyols for Polyurethanes: Synthesis and Investigation,' by Paulina Parcheta
and Janusz Datta.
-The main motivation of the research was the growing need for bio-renewables as oil runs
out and demand increases, as a result.
-At this point, Bio-based substances, made through fermentation, help create fully bio-
based polymers. They offer various advantages, such as saving energy, reducing the use
of fossil fuel and lowering costs ,and stabilizing economies.
Aim
-The study aimed to synthesize bio-based poly(propylene succinate) using a two-step
polycondensation process.
-It examined the effect of TPT as a catalyst on polyol structure and rheology.
-And The molecular structure was analysed using advanced techniques such as FTIR,
NMR, and GPC.
-The study also investigated how catalyst amount affects rheological behaviour under
conditions relevant to polyurethane production.
Synthesis of Bio-Based Polyester Polyols
-As shown in the figure, in the synthesis process, succinic acid in the solid state and 1,3-
propanediol in the liquid state were used as reactants.
-Succinic acid was derived from biomass through fermentation of plant sugars, while 1.3-
propanediol was made by fermenting glucose or other carbohydrates.
-And The synthesis method is known as two step polycondensation process. It involves
esterification to form esters and involves polycondensation to create high molecular
weight polyester polyols, with the addition of a catalyst.
Experimental Overview-1
Let’s continue with the experimental overview. Four polyester polyol samples were
prepared with different TPT concentrations. PPS-0.00 had no catalyst and served as the
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Study 2

- The title of the paper is 'Structure-Rheology Relationship of Fully Bio-Based Linear Polyester Polyols for Polyurethanes: Synthesis and Investigation,' by Paulina Parcheta and Janusz Datta.

  • The main motivation of the research was the growing need for bio-renewables as oil runs out and demand increases, as a result.
  • At this point , Bio-based substances , made through fermentation, help create fully bio- based polymers. They offer various advantages, such as saving energy, reducing the use of fossil fuel and lowering costs ,and stabilizing economies. Aim
  • The study aimed to synthesize bio-based poly(propylene succinate) using a two-step polycondensation process.
  • It examined the effect of TPT as a catalyst on polyol structure and rheology.
  • And The molecular structure was analysed using advanced techniques such as FTIR, NMR, and GPC.
  • The study also investigated how catalyst amount affects rheological behaviour under conditions relevant to polyurethane production. Synthesis of Bio-Based Polyester Polyols
  • As shown in the figure, in the synthesis process, succinic acid in the solid state and 1,3- propanediol in the liquid state were used as reactants.
  • Succinic acid was derived from biomass through fermentation of plant sugars, while 1. 3 - propanediol was made by fermenting glucose or other carbohydrates.
  • And The synthesis method is known as two step polycondensation process. It involves esterification to form esters and involves polycondensation to create high molecular weight polyester polyols, with the addition of a catalyst. Experimental Overview- 1 Let’s continue with the experimental overview. Four polyester polyol samples were prepared with different TPT concentrations. PPS-0.00 had no catalyst and served as the

reference. In the prepared samples, TPT concentrations ranged from 0.10% to 0.30%, with a 0.05% increase. As an experimental set-up, a three-neck glass flask was used as the reactor, equipped with key components, such as a mechanical stirrer, thermometer, and condenser. Experimental Overview- 2 Let’s talk about reaction characteristics.

  • The molar ratio of succinic acid (SA) to 1.3-propanediol (PDO) was set at 1:1.2( one to one point two ), with PDO in excess.
  • The reaction occurred at 140°C in a nitrogen atmosphere with continuous stirring.
  • Water is removed by distillation to drive the reaction forward.
  • A TPT catalyst was added, and the temperature was increased to 160°C.
  • The reaction was conducted under reduced pressure, and the nitrogen flow stopped.
  • The reaction progress is monitored by the acidic number, aiming for less than or equal to one milligram of KOH per gram.
  • The final product was a polyester polyol with an average molecular weight of around 2000 g/mol. and a functionality of 2 FTIR ANALYSIS
    • In the study, FTIR analysis was used to obtain the spectra of the bio-based polyester polyols and their pure components. As you can see from the graph , The peaks with yellow and blue circled confirmed the presence of ester bonds in poly(propylene succinate).
    • In addition, the analysis confirmed that the catalyst content had no significant effect on the macromolecular structure of the synthesized polyols.
    • As I mentioned, the raw materials were also analyzed. 1,3-Propanediol showed peaks for hydroxyl and C–O groups, while succinic acid showed peaks for carboxyl and carbonyl groups. NUCLEAR MAGNETIC RESONANCE (^1 H NMR)

By-product Removal : Conducting the reaction under reduced pressure facilitates the removal of volatile by-products, such as water or alcohols formed during the esterification and polycondensation processes. By lowering the pressure, these by- products can be evaporated more easily, which helps drive the reaction toward completion and increases the yield of the desired polyester polyol. Reaction Kinetics : The combination of an inert atmosphere and reduced pressure can enhance the reaction kinetics, allowing for more efficient polymerization. This can lead to a higher molecular weight and better properties of the final product.

  1. Why is the water removed in esterification? Water is removed during the esterification process for several key reasons: Driving the Reaction Forward : Esterification is a reversible reaction between a carboxylic acid and an alcohol, producing an ester and water. By removing water from the reaction mixture, the equilibrium of the reaction is shifted toward the formation of more ester. This principle is known as Le Chatelier's principle, which states that a system at equilibrium will adjust to counteract any changes imposed on it. Increasing Yield : Removing water helps to maximize the yield of the desired ester product. If water remains in the mixture, it can react with the ester to revert back to the original carboxylic acid and alcohol, thus reducing the overall yield of the ester. Improving Reaction Kinetics : The removal of water can also enhance the reaction kinetics, allowing the esterification to proceed more quickly and efficiently. This is particularly important in industrial processes where time and efficiency are critical. Preventing Hydrolysis : If water is allowed to accumulate in the reaction mixture, it can lead to hydrolysis of the ester back into the carboxylic acid and alcohol, which is undesirable. By continuously removing water, the risk of hydrolysis is minimized. Overall, the removal of water during esterification is crucial for achieving a high yield of the desired ester product and for ensuring the efficiency of the reaction.
  1. Why is the PDO used in excess? Driving the Reaction Forward : Using an excess of 1,3-propanediol (PDO) helps to shift the equilibrium of the esterification reaction toward the formation of the desired polyester polyol. Since esterification is a reversible reaction, having more PDO than succinic acid ensures that there is a greater likelihood of PDO reacting with the available carboxylic acid groups, thus promoting the formation of the ester. Achieving Desired Molecular Weight : The excess PDO contributes to achieving the target molecular weight of the final polyester polyol. By providing more hydroxyl groups, the reaction can produce longer polymer chains, which is essential for obtaining the desired properties in the final product. Minimizing Side Reactions : An excess of PDO can help minimize the formation of oligomers or other side products that may occur if the reactants are present in stoichiometric amounts. This ensures a more controlled reaction environment and leads to a more uniform product. Compensating for Losses : During the reaction, some PDO may be lost due to evaporation or other factors. Using it in excess helps to ensure that there is still enough available to complete the reaction and achieve the desired outcome. Overall, the use of excess PDO is a strategic choice to enhance the efficiency of the reaction, improve yield, and ensure the desired characteristics of the polyester polyol are achieved.
  2. Why, in polycondensation, nitrogen flow is stopped? In the polycondensation process, the flow of nitrogen is typically stopped for the following reasons: Facilitating Reaction Conditions : Once the polycondensation reaction begins, it often requires specific conditions such as increased temperature and reduced pressure. Stopping the nitrogen flow allows for better control of these conditions, as the reaction can be conducted under a vacuum or reduced pressure to facilitate the removal of by- products. Preventing Dilution of Reactants : Continuous nitrogen flow can dilute the reactants in the reaction mixture, which may hinder the efficiency of the reaction. By stopping

distribution of polymer chains, allowing researchers to understand how the synthesis conditions (like catalyst amount) affect the final product. A well- defined molecular weight distribution is crucial for ensuring consistent performance in applications, particularly in the production of polyurethanes.

  • Polyols Show Non-Newtonian Fluid Behavior : o The synthesized bio-based polyester polyols exhibit non-Newtonian fluid behavior, meaning their viscosity changes with the applied shear rate. Specifically, they display pseudoplasticity, where the viscosity decreases with increasing shear stress. This behavior is advantageous in processing applications, as it allows for easier handling and application of the polyols in manufacturing processes. Understanding the rheological properties is essential for predicting how these materials will behave during mixing, pouring, and curing.
  • 0.25 wt.% and 0.30 wt.% Catalysts Yield Optimal Properties : o The study identified that using 0.25 wt.% and 0.30 wt.% catalyst concentrations resulted in the most favorable properties for the synthesized polyols. These concentrations led to a balanced molecular weight distribution, optimal viscosity, and desirable mechanical properties. This finding suggests that these specific catalyst levels are ideal for producing bio-based polyester polyols that can meet the performance requirements for applications in polyurethane production.
  • Comparable to Commercial Polyols (POLIOS 55/20), Sustainable Alternative for Polyurethane Production : o The properties of the synthesized bio-based polyester polyols were found to be comparable to those of commercially available synthetic polyester polyols, such as POLIOS 55/20. This similarity indicates that the bio- based alternatives can potentially replace traditional petroleum-based polyols in polyurethane production, offering a more sustainable option. The use of bio-renewable resources not only reduces reliance on fossil fuels but also contributes to lower environmental impact, making these

bio-based polyols an attractive choice for manufacturers looking to adopt greener practices.

  • These outcomes collectively highlight the significance of catalyst optimization in the synthesis of bio-based polyester polyols and their potential as sustainable alternatives in the polymer industry.
  1. Nuclear Magnetic Resonance (NMR) analysis as described in the article: Peak at 2.63 ppm (d) - Succinic Acid : This peak is attributed to the methylene protons (-CH2-) adjacent to the carbonyl group in succinic acid. The presence of this peak confirms that succinic acid is part of the polymer structure, indicating that the esterification reaction has occurred. It serves as evidence of the starting material used in the synthesis of the polyester polyol. Peaks at 4.20 ppm (e) and 2.00 ppm (f) - Propylene Glycol : The peak at 4.20 ppm corresponds to the methylene protons (-CH2-) connected to the ether oxygen in propylene glycol, while the peak at 2.00 ppm is associated with the methylene protons (-CH2-) that are not adjacent to any electronegative atoms. These peaks confirm the incorporation of propylene glycol into the polymer structure, indicating that the glycol component is successfully integrated into the polyester polyol. Peak at 3.65 ppm (a) - Hydroxyl-Terminated End Groups : This peak is indicative of the hydroxyl (-OH) groups at the ends of the polymer chains. The presence of this peak suggests that the synthesized polyesters have hydroxyl-terminated end groups, which are important for the properties of the final polymer, especially in applications where reactivity is required (e.g., in polyurethane synthesis). Peaks at 1.90 ppm (b) and 4.35 ppm (c) - Low Molecular Weight Oligomers :