HET acid based oligoesters – TGA/FTIR studies

One of the important reactive halogenated dicarboxylic acids used in the synthesis of flame retardant unsaturated polyester resins is 1,4,5,6,7,7-hexachlorobicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid (HET acid). In the present investigation four different oligoesters are synthesized using HET acid as the diacid component and 1,2-ethane diol, 1,2-propane diol, 1,3-propane diol and 1,4-butane diol as the aliphatic diols. Melt condensation technique in vacuum is used for the synthesis of the oligoesters. The number average molecular weights of the oligoesters are determined using end group analysis. The degree of polymerization is estimated to be 3–5. The structural characterization is done using FTIR and NMR (1H and 13C) techniques. In the present investigation, TGA-FTIR studies for the different oligoesters are carried out in nitrogen atmosphere. The materials are heated from ambient to 600 °C at a heating rate of 20 °C/min. The main volatile products identified are CO, HCl, H2O, CO2, hexachlorocyclopentadiene and HET acid/anhydride. The evolution profile of these materials with respect to the structure of the oligoesters is discussed in detail and presented. The importance of β-hydrogens in the diol component and the plausible mechanism for the flame retardant behavior of these oligoesters are presented

Thermal Degradation Studies on PMMA–HET Acid Based Oligoesters Blends

Imparting thermal stability to polymethyl methacrylate (PMMA) without affecting its optical clarity is attempted by incorporating HET acid based oligoesters. Pure PMMA and PMMA containing five and 20 wt% of four different oligoesters are separately prepared using bulk polymerization. The thermal properties of the materials studied using DSC, TG, TG–FTIR and Pyr–GC–MS are presented. The main volatile degradation products identified are CO, HCl, CO2, H2O, hexachlorocyclopentadiene, hexachloroendomethylene tetrahydrophthalic acid/anhydride and methyl methacrylate. A detailed mechanism for the influence of the degradation products of HET acid based oligoesters on the thermal degradation of PMMA is also presented

Novel Composites for Bone Tissue Engineering

Novel metal oxide-doped fluorophosphates nano-glass powders were synthesized by melt quenching method, and their non-toxicity is proved by MTT. Their efficacy in bone formation is confirmed by osteocalcin and ALP secretion. Composites were made using PLA, PDLLA, PPF, or 1,2-diol with fluorophosphates nano-glass powders (AgFp/MgFp/ZnFp). Their non-toxicity was assessed by cell adhesion and MTT. The ability of the composite for bioconversion was assessed by RT-PCR estimation for osteocalcin, Collagen II, RUNX2, Chondroitin sulfate, and ALP secretion accessed by ELISA method. The animal study in rabbit showed good callus formation by bioconduction and bioinduction. The bioconversion of the composite itself was proved by modified Tetrachrome staining. From the 12 different composites with different composition, the composite PPF+PDLLA+PPF+ZnFp showed the best results. These obtained results of the composites made from common biological molecules are better than the standards and so they do biomimic as bone substitutes. The composites can be made as strips or granules or cylinders and will be a boon to the operating surgeon. The composite meets nearly all the requirements for bone tissue engineering and nullifies the defect in the existing ceramic composites

Effect of Graphite Filler on the Physiochemical Properties of Graphite Reinforced Thermoset Rooflite – Unsaturated Polyester Resin Composites

Received: 24.01.24. Revised: 09.02.24. Accepted: 09.02.24. Available online: 29.02.24.The authors would like the thank the Principal, and Head of the department of Chemistry, Government Arts college, Udumalpet 642 126, for allowing us to conduct the experi-ments. We extend our thanks to Dr. R. Venckatesh, Depart-ment of Chemistry, Government Arts college, Udumalpet 642 126 for helping us in the IR spectral studies of the sam-ples. The Authors wish to thank DST FIST DST-FIST-2018 (SR/FST/COLLEGE-417/2018) (TPN-2011) laboratory of the department for providing assistance to this research.The crystallinity index of the studied composite materials increased due to the enhanced interaction between the resin matrix and graphite filler.Agglomeration due to higher concentration of graphite filler lowers the interfacial contact and affects the mechanical characteristics of the composites.The glass transition temperature increases with the addition of graphite.When the percentage of graphite in composites is raised, the limiting oxygen index revealed that the composites are self-extinguishing.The synthetic composites exhibit a consistent swelling behavior in response to different chemical environments.It is well known that many polymers are insulators with poor mechanical properties, which limit their use in fuel cell applications. Physicochemical properties of the polymers can be improved by adding conductive fillers. Carbon-based materials like graphite, which provides excellent mechanical strength and thermal conductivity to the polymer matrices, is of special interest because of its abundance, low cost and light weight when compared to other carbon allotropes. In the present work we describe the physicochemical properties of rooflite unsaturated polyester resin/graphite composites. Rooflite resin and three of its composites containing 1%, 3% and 5% of graphite by weight (C-2, C-3, and C-4, respectively) were synthesized and characterized by FTIR spectral data. XRD showed two peaks at 2 = 27.37°and 55.40° with d spacing value of 3.2559 nm and 1.6571 nm, respectively, indicating the change in degree of crystallinity of the composite. The calculated crystallinity for the resin is 7.3%, and for C-2, C-3 and C-4 its values are 12.1%, 14.3%, 17.1%, respectively, evidencing the interactions between the graphite and polymer matrix. The composites showed fractured surfaces and porous rough structure with randomly distributed vascularized cavities. Agglomeration occurs, when the concentration of graphite increases. The glass transition temperature for the pure resin is 65.9 °C and increases when the resin is filled with graphite. Thermogravimetric analysis (TGA) of the composites showed no marked difference between Tmax and Tfinal, and LOI values of C-3 and C-4 are above 21%, making them self-extinguishable materials that could be used for making bipolar plates. The chemical resistance investigation against water, NaCl, NaOH, acetic acid, and toluene showed more resistance to acid than alkali solutions. These rooflite resin/graphite composites could be further studied to explore the possibility of making bipolar plates, which are an essential component of fuel cells

Application of Metal-Organic Framework as Reactive Filler in Bisphenol-A-Based High-Temperature Thermosets

Excellent thermoset monomers, bisphenol-A-based biscyanate ester (BADCy) and bispropargyl ether (BPEBPA), are synthesized and thermally cured to high-temperature thermosetting polymers. The nanoporous aluminum fumarate (Al_FA_A), an interesting Metal-Organic Framework (MOF), is synthesized in an eco-friendly manner and used as a reactive nanoparticle filler. The interaction of fumarate π bonds (trans -CH=CH-) in MOF with the reactive end functional groups (-O-C ≡ N) in cyanate ester (CE) and (-CH2-C ≡ CH) in bispropargyl (BP) ethers is focused in these hybrid nanocomposites. The % decrease in enthalpy of curing in the organic and the inorganic blends (~60% for CE and ~ 10% for BP) indicates the interaction exciting between the MOF and the organic component. The addition of the aluminum fumarate MOF increases the glass transition temperature of the polymers. The amount of heat released for every increase in 1°C during the temperature window of curing (ΔHc/TE-TS) of the neat BADCy resin is approximately 2.4 times higher than the blend (BADCy+Al_FA_A). But BPEBPA shows only a 1% higher temperature curing window compared to its blend with MOF. The metal hotspots present in the hybrid nanocomposites may be the reason for the decrease in the thermal stability, and the % char residue is noted at 700°C. The TG-FTIR studies are done to predict the gaseous products (CO2) evolved during thermal degradation