Achraf Kallel

@article{ben_abdallah_1721,

title = {Modeling of viscoelastic behavior of a shape memory polymer blend},

author = {Abir Ben Abdallah and Achraf Kallel and Abbas Tcharkhtchi and Tarek Hassine and Fehmi Gamaoun},

url = {https://onlinelibrary.wiley.com/doi/10.1002/app.51859},

year  = {2022},

date = {2022-05-01},

journal = {Journal Of Applied Polymer Science},

volume = {139},

number = {13},

pages = {51859},

abstract = {Shape memory effect (SME) of polymers is a property that concerns both,

macroscopic and microscopic changes. The variation of internal polymer

properties such, as molecular weight (Mw), rigidity, and viscoelasticity could

alter its SME. In this study, a bi-parabolic model with six parameters is used to

describe the viscoelastic behavior of a shape memory polymer (SMP) blend

(40% poly(caprolactone), PCL/60% Styrene-Butadiene-Styrene) with different

PCL Mw. These parameters are determined using the Cole-Cole method.

Modeling curves (E00 = f (E0)) will be then compared to experimental data from

dynamical mechanical analysis (DMA) tests. It is shown that the bi-parabolic

model predicts well the behavior of the SMP mixture for different Mw of PCL.

Afterwards, the evolution of the model parameters with the Mw of PCL is

investigated. It is revealed that, when Mw of PCL drops, the relaxation modulus

E0 increases. This result proves that the rigidity of the SMP blend rises with

Mw declines.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{kallel_1585,

title = {Driving force for shape memory effect of polymers},

author = {Achraf Kallel and Abir Ben Abdallah and Fehmi Gamaoun and Abbas Tcharkhtchi and Hachmi BenDaly and Joseph Fitoussi},

url = {https://link.springer.com/article/10.1007/s10965-021-02637-4},

year  = {2021},

date = {2021-07-01},

journal = {Journal Of Polymer Research},

volume = {28},

number = {10},

pages = {308},

abstract = {In this study, we aim to evaluate the shape memory effect of a Poly (Caprolactone) (PCL) (40%) and a Styrene-Butadiene-Styrene (SBS) (60%) blend. Shape memory cycle tests are performed at different temperatures to detect the best recovery rate. Under appropriate temperature, the blend recovers substantially its original shape. To study the recovery rate evolution, multi cycle tests are realized with controlled temperature. The results indicate that the shape memory effect growths when the number of cycle increases. The stored energy acts as a driving force to bring the polymer to its permanent shape after each loading cycle. Then, an original method is proposed to measure the stress-strain evolution during the recovery. With a variable temperature, no standard test can follow the stress-strain evolution. This test is needed to validate the behavior model.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ben_abdallah_1269,

title = {Molecular weight influence on shape memory effect of shape memory polymer blend ( poly(caprolactone)/styrene-butadiene-styrene )},

author = {Abir Ben Abdallah and Fehmi Gamaoun and Achraf Kallel and Abbas Tcharkhtchi},

url = {https://onlinelibrary.wiley.com/doi/10.1002/app.49761},

year  = {2021},

date = {2021-02-01},

journal = {Journal Of Applied Polymer Science},

volume = {138},

number = {5},

pages = {49761},

abstract = {The shape memory effect (SME) does not only concern the macroscopic structure. It concerns also the polymer structure at morphological, macromolecular, and molecular scales. This effect may depend on different physicochemical properties like morphology heterogeneity, chain rigidity, steric hindrance, chain polarity, free volume, cross-linking or entanglement density, molecular shape and weight, and so on. Hence, finding the relationship between the SME and these properties is very important. This can help to obtain the knowledge about the phenomenon origin and mechanism. One of the basic polymer properties, which can have direct SME, may be the molecular weight (Mw). The question here is: If the Mw of a shape memory polymer (SMP) changes, for different reasons like degradation, what will be the effect of this change on its SME. In order to answer to this question, the investigation is focused on an SMP blend of 40% poly(?-caprolactone) (PCL) and 60% styrene-butadiene-styrene (SBS). Then, enzymatic hydrolysis is performed on this blend to change its Mw. It is shown that this change is only related to the variation in the Mw of PCL. After that, different samples with a distinct average Mw are prepared and characterized by various experimental methods. Shape memory tests are performed on these blends, and the recovery rate (Rr) for each of them is determined. It is found that when Mw of PCL decreases, its degree of crystallinity, its glass transition, and its melting temperatures, corresponding to the PCL phase, increase. However, the elongation at break of the blend declines with the reduction in Mw. The tests show that the alteration in the blend's Mw influences its SME. Indeed, Rr of the (PCL/SBS) mixture drops with the decrease in Mw of PCL.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ben_abdallah_992,

title = {Enzymatic Hydrolysis of Poly (Caprolactone) and its Blend with Styrene-Butadiene-Styrene (40% PCL/60% SBS)},

author = {Abir Ben Abdallah and Achraf Kallel and Fehmi Gamaoun and Abbas Tcharkhtchi},

url = {https://link.springer.com/article/10.1007%2Fs10924-019-01522-y},

year  = {2019},

date = {2019-11-01},

journal = {Journal Of Polymers And The Environment},

volume = {27},

pages = {2341-2351},

abstract = {In this study, we aim to evaluate the effect of enzymatic hydrolysis on aliphatic polyester and on its shape memory blend. Therefore, the hydrolysis of poly (?-caprolactone) (PCL) and of its shape memory polymer (SMP) blend [40% PCL/60% styrene-butadiene-styrene (SBS)] in a solution containing an Amano lipase from pseudomonas fluorescence and a phosphate buffered saline (PBS), is achieved. An appropriate characterization helps to better understand the behaviour of these polymers. So, the properties of these materials prior and after hydrolytic degradation are investigated. When they are submitted to enzymatic hydrolysis, the physico-chemical and mechanical properties of PCL and its blend (PCL/SBS) change. PCL undergoes a significant decrease in weight during enzymatic hydrolysis. Yet, blending PCL with SBS considerably reduces its degradation rate in terms of weight drop, compared with pure PCL. The enzymatic hydrolysis causes chains splitting, which rises their mobility and facilitates their reorientation. Consequently, for PCL and its blend, the degree of crystallinity Xc rises during hydrolytic degradation, which confirms that the amorphous regions of PCL are more susceptible to hydrolysis. Besides, this continuous rise in crystallinity causes the augmentation of PCL and its blend melting, crystallization and glass transition temperatures. Moreover, the PCL brittleness increases, and the blend ductility decreases with the enzymatic hydrolysis time. For both, PCL and its blend, the young modulus displays two opposite effects; it goes up due the growth of crystallinity, but at the end of hydrolysis, its value goes down because of weight loss.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{kallel_891,

title = {Study of bonding formation between the filaments of PLA in FFF process},

author = {Achraf Kallel and Imade Koutiri and Elham Babaeitorkamani and Alireza Khavandi and Morteza Tamizifar and Mohammadali Shirinbayani and Abbas Tcharkhtchi},

url = {https://www.hanser-elibrary.com/doi/10.3139/217.3718},

year  = {2019},

date = {2019-08-01},

journal = {International Polymer Processing},

volume = {34},

number = {4},

pages = {434-444},

abstract = {Fused filament fabrication (FFF) is an additive manufacturing (AM) process that provides physical objects commonly used for modeling, prototyping and production application. The major drawback of this process is poor mechanical property due to the porous structure of final parts. This process requires careful management of coalescence phenomenon. In this paper, the major influencing factors during the FFF process of poly(lactic acid) (PLA) were investigated experimentally and with a numerical model. It has been shown that the polymer temperature has a significant effect on rheological behavior of PLA especially on adhesion of the filaments. An experimental set-up has been placed in the machine to have the cyclic temperature of the filament. A variation of the polymer temperature influences process parameters such as feed rate, temperature of nozzle and temperature of the platform. The results showed that the amount of polymeric coalescence (neck growth) rises when increasing the feed rate, the nozzle temperature, and the platform temperature. A model to predict the neck growth is proposed. It predicts a lower amount of neck growth value than obtained with experimentally. This difference has been explained as the effect of other phenomena, such as polymer relaxation time, pressure of the nozzle and especially cyclic temperature which is not taken into account in the model.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}