Kinetic and chemorheological modeling of thermosetting polyurethanes obtained from an epoxidized soybean oil polyol crosslinked with glycerin

Armanasco, Franco; D’hers, Sebastian; Chiacchiarelli, Leonel

doi:10.48550/arxiv.2204.07929

Cited by 1 publication

(8 citation statements)

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“…As we have already reported in a chemorheology study of this formulation, 17 the evolution of the conversion (cure) is very slow due to vitrification effects. Hence, it is important to analysis the post-cure residual heat flow, which is a measurement performed by DSC analysis so as to corroborate if the material has reached to the final conversion.…”

Section: Sample Characterization Techniquesmentioning

confidence: 56%

“…A soy-based polyol (ESOP) with an OH# of 137 mgKOHÁg À1 , a functionality of 2.90, a molecular weight of 697 Da and with fully secondary hydroxyl groups was synthesized using the procedure already reported in a previous work. 17 Further details of the physicochemical properties of this polyol can also be consulted there.…”

Section: Materials and Sample Manufacturementioning

confidence: 99%

“…It is important to highlight that the hydroxyls present on each precursor compete to react with the isocyanate group, changing the overall cure kinetics of the thermoset polyurethane. 17,34,35 A very important aspect that our group has already studied is vitrification. As it has already been studied in our previous work, vitrification affected substantially the cure kinetics of this thermoset.…”

Section: Flexural Mechanical Testsmentioning

confidence: 99%

“…16 Our group recently published a chemorheological analysis of a polyurethane thermoset which complied such characteristics, finding as well that the cure of this system was dominated by vitrification effects. 17 The rubbery to glass transition (T g ) is a typical thermal transition found in polymers and it reduces drastically the cure kinetics during cure. 18 The role of the post-cure cycle on the thermomechanical properties of the resultant thermoset was not addressed.…”

Section: Introductionmentioning

confidence: 99%

“…The main issue with vegetable polyols is that the combination of a high hydroxyl functionality and low processing apparent viscosity is usually very difficult to attain. 17 In this regard, biobased crosslinkers, such as glycerin obtained from the transesterification of soybean oil, 31,32 can circumvent this issue. However, it might be argued that glycerin has a very hygroscopic nature, leading to the formation of pores.…”

Section: Introductionmentioning

confidence: 99%

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The role of post‐cure cycle on the thermomechanical properties of soy‐based polyurethane thermosets

Armanasco

D’hers

Chiacchiarelli

2023

J of Applied Polymer Sci

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A systematic study of the post‐cure cycle of soy‐based polyurethane thermosets was conducted as a function of crosslinker content, post‐cure temperature and time. An improvement of 207% of the flexural strength, up to 175 MPa, was measured by increasing the crosslinking content to 60 wt% and by using a post‐cure cycle temperature of 110°C. Similarly, the flexural modulus also increased by 199%, up to 3.2 GPa, while maintaining a flexural strain to failure of 6.60%. In situ studies of the post‐cure cycle using dynamical mechanical analysis revealed the interplay between the two interpenetrating polymer networks as a function of crosslinker content. At a crosslinker content below 40 wt%, two rubbery to glass transition temperatures (Tg) were found at 60 and 200°C, respectively. At 60 wt%, only one Tg at temperatures close to the degradation temperature was identified (250°C). Scanning electron microscope micrographs of the fracture surface revealed the formation of stress induced cracks which were mitigated through the use of a temperature stepped post‐cure cycle. The formation of soft segments with high degradation temperatures (485°C) were revealed by thermogravimetric analysis, which can be attributed to the presence of additional covalent bonds such as allophanate and carbodiimide that were also identified through Fourier transform infrared analysis. The results revealed in this work are key for the development of biobased polyurethanes applied for the polymer composite industry. In this regard, this study represented the first analysis of the post‐cure cycle of a soy‐based polyurethane thermoset.

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Section: Sample Characterization Techniquesmentioning

confidence: 56%

Section: Materials and Sample Manufacturementioning

confidence: 99%

Section: Flexural Mechanical Testsmentioning

confidence: 99%