Fabrication of 3D scaffolds based on fully biobased unsaturated polyester resins by microstereo-lithography

Additive Manufacturing (AM) technologies are an effective route to fabricate tailor made scaffolds for tissue engineering (TE) and regenerative medicine with microstereo-lithography (µSLA) being one of the most promising techniques to produce high quality 3D structures. Here, we report the crosslinking studies of fully biobased unsaturated polyesters (UPs) with 2-hydroxyethyl methacrylate (HEMA) as the unsaturated monomer (UM), using thermal and µSLA crosslinking processes. The resulting resins were fully characterized in terms of their thermal and mechanical properties. Determination of gel content, water contact angle (WCA), topography and morphology analysis by atomic force microscopy (AFM) and scanning electron microscopy (SEM) were also performed. The results show that the developed unsaturated polyester resins (UPRs) have promising properties for µSLA. In vitro cytotoxicity assays performed with 3T3-L1 cell lines showed that the untreated scaffolds exhibited a maximum cellular viability around 60 %, which was attributed to the acidic nature of the UPRs. The treatment of the UPRs and scaffolds with ethanol (EtOH) improved the cellular viability to 100%. The data presented in this manuscript contribute to improve the performance of biobased unsaturated polyesters in additive manufacturing.

Mechanical, Morphological, Thermal and Dynamic Study of Composites of Unsaturated Polyesters-Date Palm Leaf Fiber DPLF

In order to improve the properties of unsaturated polyesters, this study discusses the possibilities of developing a natural waste, date palm leaf fiber DPLF, produced in the northern Algerian Sahara, associated with the polymer matrix of a thermosetting polyester resin UP. For this purpose, composite plates containing virgin fiber at rates of 6 and 10% were treated with an alkaline solution of 6% NaOH on the one hand, and a silane compound on the other. In this research, a mechanical study of strength and elongation at break was carried out. In addition, morphological behavior was followed by SEM scanning electron microscopy. ATG thermogravimetric analysis and energy flow were monitored by DSC differential scanning calorimetry. Also, a study of the water absorption capacity has been conducted. In addition, a dynamic mechanical analysis DMA was carried out. The findings of this study show that there is a favorable mechanical behavior for the composites containing the 6% and 10% DPLF fiber, with alkaline NaOH and Silane treatment. They also show that the chemical treatment with alkaline solution and silane gives composites certain thermal stability compared to those with untreated fiber. Findings also explore that the absorption of water by the various composites shows that the chemical treatment promotes some intermolecular associations with water. Findings also show that the storage modulus (E') increases when the composite contains 10% DPLF, treated and untreated, and the maximum value of the tangent moves towards the high temperature for the treated and untreated fiber composite.

Synthesis of Semicrystalline Long Chain Aliphatic Polyesters by ADMET Copolymerization of Dianhydro-D-glucityl bis(undec-10-enoate) with 1,9-Decadiene and Tandem Hydrogenation

Acyclic diene metathesis (ADMET) copolymerization of dianhydro-D-glucityl bis(undec-10-enoate) (M1) with 1,9-decadiene (DCD) using ruthenium-carbene catalyst, RuCl2(IMesH2)(CH-2-OiPr-C6H4) [IMesH2 = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene, HG2], afforded unsaturated polyesters (Mn = 9300–23,400) under the optimized conditions. Subsequent tandem hydrogenation (H2 1.0 MPa, 50 °C) with the addition of a small amount of Al2O3 resulted in the saturated polymers having a melting temperature of 71.7–107.6 °C, depending on the molar ratio of M1 and DCD.

Investigation of the Regularities of the Synthesis of Unsaturated Polyesters by the Method of Acceptor-Catalytic Polycondensation

The regularities of acceptor-catalytic polycondensation in the synthesis of copolymers containing arylate, sulfone, and dichloroethylene groups in the main chain have been studied. The optimal conditions for their production have been found. Infrared spectroscopy, elemental analysis, turbidimetric titration and other methods confirmed the formation of copolymers of the proposed structure.

Hardening condition of unsaturated polyether from alcoholysis products of secondary polyethylene terephthalate

The technological parameters of the curing of unsaturated polyesters synthesized on the basis of alcoholysis products of secondary polyethylene terephthalate and used in the production of fiberglass pipes have been studied. It is shown that unsaturated polyesters synthesized on the basis of alcoholysis products can completely substitute imported resins of 196 and 196A grades in the production of fi berglass pipes.

Synergistic effects in cross-linked blends of ion-conducting PEO-/PPO-based unsaturated polyesters

Ion-conductive unsaturated polyesters (UP) were synthesised from poly(ethylene oxide) (Xn = 9, 13, 22, 90) or poly(propylene oxide) (Xn = 7, 13, 20, 34, 68) and maleic anhydride. Subsequently, the polyesters were doped with LiClO4 and cross-linked with styrene using a redox initiator. For PEO-based polyesters, the minimum resistivity is found at an O/Li+ molar ratio of 50/1. In contrast, more lithium is required to reach the minimum when using PPO (O/Li+ = 10/1). Unlike the PEO-based polyesters, cross-linking of the PPO types gives rise to decreasing resistivities at increasing molecular weight. This correlates well with the transverse proton relaxation time determined by single-sided NMR, which is an indicator of the chain mobility. The cross-linking reaction of these UP with styrene exactly follows the predictions based on the copolymerisation parameters and is, therefore, not dependent on the ratio of styrene to UP double bonds as previously reported. Due to the opposing effects of the molecular weight on the ion conductivity of PEO- and PPO-based UP, 1:1 blends of short-chain PPO and long-chain PEO polyesters were cross-linked with styrene. The resulting networks showed a resistivity of 4 kΩ m (σ = 2.5∙10−4 S∙m−1), which is 5 times lower than the pure PEO and 3 times lower than the pure PPO materials.

RATIONAL DISPOSAL OF PET CONTAINING WASTE AND PROSPECTS FOR THE SYNTHESIS OF NEW POLYMERS

As a result of the research on the utilization of polyethylene terephthalate-containing household waste, a promising direction was identified in the production of a new type of secondary polyethylene terephthalate (SPET) - unsaturated polyesters. It was revealed that the final product, which formed when the alcoholization process is complete in any proportion of of glycol and secondary polyethylene terephthalate, is the bisalkylent terephthalate of terephthalic acid; the content of the alcoholysis product consists of bisalkylent terephthalate, different molecule mass, functionally hydroxyl-containing complex polyester polyol and free diols. The laws of alcoholization of secondary polyethylene terephthalate have been studied and the mechanism has been established. Studies have shown that, in contrast to existing theories, such as the formation of ethylene glycol in the polycondensation of phthalic anhydride bisalkylene glycol derivatives, the increase in ethylene glycol in the process was found to be due to the exchange of diethylene glycol in the macrochain. The formation of unsaturated polyesters goes stage by stage, first ethylene-, diethylene glycol acid esters are formed, then they are exposed to hydroxyl-containing oligomers - secondary polyethylene terephthalate alcohol products. A mathematical model of the process of alcoholization of SPET and diethylene glycol was created, studies showed that the difference between the values obtained as a result of the mathematical model and experiments are less than 5%. The unsaturated polyesters were synthesized on the basis of SPET alcoholization products. Many of them have shown their superiority over unsaturated polyesters PN-1, PN-3, PN-15, which are used in industry for general purposes. By developing unsaturated polyesters on the basis of secondary polyethylene terephthalate alcohol products, it was found that the structure of these polyesters is close to that of imported resins "Body", 196, 196A, used in industry.