Thermal Stability Of Polymers Research Articles

Closed-Loop Chemical Recycling of a Biobased Poly(oxanorbornene-fused γ-butyrolactone).

New polymers, properly designed for end-of-life and efficiently formed from renewable carbon, are key to the transition to a more sustainable circular plastics economy. Ring-opening polymerization (ROP) of bicyclic lactones is a promising method for the production of intrinsically recyclable polyesters, but most lactone monomers lack an efficient synthesis route from biobased starting materials, even though this is essential to sustainably account for material loss during the life cycle. Herein, we present the exceptionally rapid and controlled polymerization of a fully biobased tricyclic oxanorbornene-fused γ-butyrolactone monomer (M1). Polyester P(M1) was formed in low dispersity (D̵ = 1.2-1.3) and controllable molecular weight up to Mn = 76.8 kg mol-1 and exhibits a high glass transition temperature (Tg = 120 °C). The orthogonal olefin and lactone functionalities offer access to a wide range of promising materials, as showcased by postpolymerization modification by hydrogenation of the olefin, which increased polymer thermal stability by over 100 °C. Next to rapid hydrolytic degradation and solvolysis, the poly(oxanorbornene-fused γ-butyrolactone) could be cleanly chemically recycled back to the monomer (CRM), in line with its favorable ceiling temperature (Tc) of 73 °C. The density functional theory (DFT)-computed ΔH° of ring-opening with methanol of γ-butyrolactone-based monomers provided a model to predict Tc, and the DFT-computed and X-ray crystal structure-derived structural parameters of M1, hydrogenated analogue M1-H2, and regioisomer M2 offered insights into the structural descriptors that cause the high polymerizability of M1, which is key to establishing structure-property relations.

Functionally graded polymers and ceramic adhesives: dynamic, viscoelastic, and thermal stability analysis

Functionally graded design transforms polymer composites without altering their properties. These composites change only the surface exposed to severe temperatures, leaving the rest unchanged. This study analyses ceramic additions’ effects on polymer thermal stability and crystallinity. Dynamic mechanical analysis (DMA) examined viscoelastic behaviour and thermogravimetric stability. Alumina, silicon carbide, and hafnium carbide ceramic powders increase thermal stability. DMA examined how ceramic additives affected composite viscoelasticity. The functionally graded design barely affects ceramic adhesive thermal properties. The ceramic adhesive remained stable at 800 °C with only 6% weight loss, while the other two disintegrated before 600 °C.

Thermomechanical properties of multifunctional polymer hybrid nanocomposites based on carbon nanotubes and nanosilica

AbstractNanocomposites containing low wt% of oxidized multi‐walled carbon nanotubes (MWCNT‐OXI), nanosilica (NS), and its hybrid (MWCNT‐OXI/NS) in epoxy resin were produced and evaluated. The used nanoparticles were studied by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Raman spectroscopy while the nanocomposites were investigated in relation to its morphology, thermal, and mechanical properties. The results demonstrated significant improvements in the storage modulus (E′), glass transition temperature (Tg), and cross link density (CD), for the produced nanocomposites. Increases in thermal conductivity (TC) of up to 85% at 90°C were observed for the nanocomposites containing 1.0 wt% of the hybrid MWCNT‐OXI + NS nanofiller, when compared with neat polymer. It was also verified increases in the resistance to plastic deformation for the nanocomposites, maintained the polymer thermal stability with the addition of these nanoparticles. Finally, the use of MWCNT‐OXI and NS, combined or not, significantly improved the thermal and mechanical properties of polymer, showing multifunctional characteristics for the produced nanocomposites.

Thermal Decomposition of Bio-Based Plastic Materials.

This research delves into a detailed exploration of the thermal decomposition behavior of bio-based polymers, specifically thermoplastic starch (TPS) and polylactic acid (PLA), under varying heating rates in a nitrogen atmosphere. This study employs thermogravimetry (TG) to investigate, providing comprehensive insights into the thermal stability of these eco-friendly polymers. In particular, the TPS kinetic model is examined, encompassing the decomposition of three distinct fractions. In contrast, PLA exhibits a simplified kinetic behavior requiring only a fraction described by a zero-order model. The kinetic study involves a systematic investigation into the individual contributions of key components within TPS, including starch, glycerin, and polyvinyl alcohol (PVA). This detailed analysis contributes to a comprehensive understanding of the thermal degradation process of TPS and PLA, enabling the optimization of processing conditions and the prediction of material behavior across varying thermal environments. Furthermore, the incorporation of different starch sources and calcium carbonate additives in TPS enhances our understanding of the polymer's thermal stability, offering insights into potential applications in diverse industries.

Active Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Films Containing Phenolic Compounds with Different Molecular Structures.

To obtain more sustainable and active food packaging materials, PHBV films containing 5% wt. of phenolic compounds with different molecular structures (ferulic acid, vanillin, and catechin) and proved antioxidant and antimicrobial properties were obtained by melt blending and compression molding. These were characterized by their structural, mechanical, barrier, and optical properties, as well as the polymer crystallization, thermal stability, and component migration in different food simulants. Phenolic compounds were homogenously integrated within the polymer matrix, affecting the film properties differently. Ferulic acid, and mainly catechin, had an anti-plasticizing effect (increasing the polymer glass transition temperature), decreasing the film extensibility and the resistance to breaking, with slight changes in the elastic modulus. In contrast, vanillin provoked a plasticizing effect, decreasing the elastic modulus without notable changes in the film extensibility while increasing the water vapor permeability. All phenolic compounds, mainly catechin, improved the oxygen barrier capacity of PHBV films and interfered with the polymer crystallization, reducing the melting point and crystallinity degree. The thermal stability of the material was little affected by the incorporation of phenols. The migration of passive components of the different PHBV films was lower than the overall migration limit in every simulant. Phenolic compounds were released to a different extent depending on their thermo-sensitivity, which affected their final content in the film, their bonding forces in the polymer matrix, and the simulant polarity. Their effective release in real foods will determine their active action for food preservation. Catechin was the best preserved, while ferulic acid was the most released.

Simulation and Experimental Study of the Isothermal Thermogravimetric Analysis and the Apparent Alterations of the Thermal Stability of Composite Polymers.

Composite polymers are an interesting class of materials with a wide range of applications. Among the properties of polymers which are currently being enhanced via the development of composite materials is their thermal stability, which is typically evaluated via thermogravimetric analysis (TGA). In this work, a paradox is recognized regarding the considered relationship between the polymer-filler interactions leading to a good dispersion of the filler and the improvement of thermal stability. Simulation of the TGA signal during isothermal measurements of composite polymers is performed along with experimental measurements. It is shown that there are at least three factors that can cause apparent alterations of the thermal stability of composite polymers, namely, the different buoyancy due to the different densities of the composites and the neat polymer, the different thermal diffusivity of the composites and the fact that the mass loss (or remaining mass) of the composites, conventionally, is expressed per overall mass of the composite and not per mass of polymer. The relative contributions of these factors are evaluated and it is found that the conventional expression of mass loss has the most profound effect. Furthermore, it is shown that it is proper to express and evaluate the TGA results of composite polymers per degradable (polymer) mass of the composite and not per overall mass of the composite.

Repeatable adhesion of bio-based polymer derived from tetrafunctional epoxides and polyhydric carboxylic acid

Bio-based network polymers were synthesized by cross-linking diastereomeric tetrafunctional epoxides, tetra-trans-LO (1) and tetra-cis-LO (2), with polyhydric carboxylic acid in the presence and absence of a catalyst. The cross-linking ability of 1 was higher than that of 2 and afforded to higher polymer yields, thermal stability, and mechanical strength. Repeatable adhesion with a moderately high recovery strength was achieved using 1 and polyhydric carboxylic acid in the presence of Zn(acac)2.

Assessment of World’s First Two Polymer Injectivity Tests Performed in Two Giant High-Temperature/High-Salinity Carbonate Reservoirs Using Single-Well Simulation Models and Pressure Falloff Tests Analysis

Summary Polymer flooding is a mature enhanced oil recovery (EOR) technology that has been widely implemented around the world for more than 60 years. Polymer flooding mostly targets medium- to high-permeability sandstone reservoirs with moderate salinity, hardness, and temperatures. However, in the last few years, the envelope of polymer flooding has been expanded to harsher reservoir conditions of high-temperature and high-salinity mixed-wet to oil-wet heterogeneous carbonate reservoirs. Development of novel polymers and innovative field application concepts has allowed for the reconsideration of polymer-based EOR as a promising technology to improve sweep efficiency for these challenging reservoirs. Polymer injectivity is one of the key challenges for polymer flooding projects and requires a rigorous derisking program that includes laboratory and field testing. A comprehensive laboratory program was designed to assess and investigate polymer thermal stability, polymer rheology in porous media, adsorption, and injectivity using reservoir core samples. In addition, two polymer injectivity tests (PITs) were performed in two giant light oil (0.3 cp) carbonate reservoirs in onshore Abu Dhabi under harsh conditions of high salinity (>200 g/L), high divalent ions (>20 g/L), high temperature (>250°F), and H2S concentration of up to 40 ppm. The polymer used during the two PITs (PIT 1 2019 and PIT 2 2021) is a new generation of EOR polymer (SAV 10) with high 2-acrylamido-tertiary-butyl sulfonic acid content that was specifically developed to tolerate such harsh conditions. This paper is focused on the interpretation of the PITs and lessons learned for future polymer-based EOR projects. The detailed data acquired in both tests were used to evaluate the polymer injectivity at representative field conditions and in-depth mobility reduction. The PITs together with the extensive laboratory studies are part of a thorough derisking program for the upcoming world’s first innovative hybrid EOR multiwell pilots—simultaneous injection of miscible gas and polymer (SIMGAP) and simultaneous injection of water and polymer (SIWAP). Both PITs are composed of three stages that include a multirate waterflood baseline, polymer injection using different rates, and polymer concentrations followed by extended chase waterflooding. In addition, a sequence of multiple pressure falloff (PFO) tests was acquired during the PIT executions and analyzed to obtain the required uncertainty parameters for the history-matching exercise. Polymer preshearing was considered as part of both PIT programs with the aim to homogenize the polymer molecular weight distribution and reduce possible shear-thickening effects near the wellbore as per laboratory measurements. Two single-well 3D simulation models were built to incorporate the information from polymer laboratory studies and to interpret the large field data sets acquired during the PITs. Lessons learned from PIT 1 allowed us to optimize the PIT 2 design program and achieve better understanding of polymer characteristics. The interpretation of the pressure transient analysis (PTA) of the PFO tests and the 3D simulation models of the two PITs confirmed the generation of polymer banks and demonstrated effective propagation of the polymer into the reservoirs at target concentrations and representative rates of the future SIWAP and SIMGAP interwell pilots.

Computational simulation-assisted design and experimental verification of molecularly imprinted polymers for selective extraction of chlorogenic acid

Chlorogenic acid (CGA) is an active ingredient in honeysuckle with a broad-spectrum of antibacterial activity, suppressing tumor growth and other pharmacological effects. However, it is susceptible to damage during traditional extraction and separation processes. Therefore, developing selective and efficient extraction methods of CGA is essential. Based on computational molecular simulations, a reliable and efficient molecularly imprinted polymers (MIPs) were successfully developed for selective extraction of CGA. MIPs and non-molecularly imprinted polymers (NIPs) were synthesized using a precipitation polymerization method, employing three different functional monomers: [methacrylic acid (MAA), 4-vinylpyridine (4-VP), and methyl methacrylate (MMA)], with CGA serving as the template molecule. To simulate the polymers and predict the optimal ratio between the template and functional monomer, the computational studies and adsorption performance experiments were carried out. The adsorption characteristics and thermal stability of polymers were evaluated by isothermal adsorption, adsorption kinetics, selective adsorption and thermogravimetric analysis, aiming to obtain the MIPs with specific recognition and selectivity for CGA. When the molar ratio of template CGA to functional monomer 4-VP was 1:8, the prepared MIPs was found to have the maximum adsorption capacity (14.85 mg g−1) and the highest imprinting factor (1.74) at the CGA concentration of 100 mg L−1. These results were consistent with those obtained by computational molecular simulation. This study not only provides good guidance for developing separation materials for extracting CGA from natural plants but also inspires the application of computer simulation and molecular docking techniques in the preparation of specific MIPs materials.

Excessive free radical grafting interferes with the macromolecular association and crystallization of brined porcine myofibrils during heat-set gelatinization

Free radical grafting and oxidative modification show superiority in myofibrillar protein (MP) aggregation patterns during salting process, but their consequent formation mechanisms of protein hydration network require further evaluation. Herein, we explored the effect of salt-curing (0, 1, 3 and 5 %) on MP protein polymer substrate, water-protein interaction, crystallization events and thermal stability under H2O2/ascorbate-based hydroxyl radical (•OH)-generating system (HRGS) (1, 10, 20 mM H2O2). Results showed that moderate salting (≤3%) favored the water binding of MP gels during the oxidation course. Accordingly, the maximum thermal stability (Tm) of MP gels was obtained at 3 % salting could be greatly attributed to the protein chain solubilization and refolding process. However, 5 % salt synergized with •OH oxidation intensified diffraction peak 2 (the most striking diffraction feature). Microstructural analysis validated a maximum compactness of MP gel following brining with 5 % salt at potent oxidation strength (20 mM H2O2). This study maybe promises efficient strategy to the myogenetic fibril products and biomaterials.

Self-Polymerization Reaction of Epoxidized Oleic Acid: Kinetic and Product Characterization

Epoxidized oleic acid can be transformed into vegetable oil-based polyesters through a self-polymerization reaction. This study aims to develop the kinetic model for the polymerization reaction between epoxide and carboxyl groups and the product characterization regarding its functional groups, molecular weight, and thermal stability. The polymerization reaction was carried out at the temperature of 120–180 °C for 2–6 h with the highest conversion of oxirane number up to 97%. Kinetic study showed one-step reaction model between oxirane and carboxylic group gives the activation energy value of 34.71 kJ/mol. Furthermore, the two simultaneous reaction model with further reaction between oxirane group and hydroxyl group also taken into account. The later provides a better agreement between the experimental data and the calculated conversion value. The activation energy values in the first and second steps are 38.61 and 26.00 kJ/mol, respectively. The product characterization showed that adding adipic acid did not significantly affect the polymer's molecular weight and thermal stability. The polydisperse characteristics of the poly(oleic acid) produced in this study enable poly(oleic acid) to be used as a lubricant, a polymer additive, or a precursor to produce polymers with higher molecular weights by taking advantage of the accessibility of OH groups. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Enhanced Thermal Stability of Polymers by Incorporating Novel Surface-Decorated SrTiO3@Graphene Nanoplatelets

Polyvinylidene fluoride (PVDF) is a vital component in the manufacturing of flexible dielectric capacitors due to its exceptional electrical insulation properties. However, its thermal stability remains a significant concern. To address this, we have developed a novel approach in which surface-decorated SrTiO3@Graphene (STO@G) nanoplatelets were prepared using a wet-chemical method. Subsequently, STO@G/PVDF nanocomposite films were synthesized via a solution-casting method using an automatic film coater. X-ray diffraction (XRD) analysis confirmed the presence of the required strontium titanate (SrTiO3), graphene, and STO@G phases. Further, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDXS) were used to examine the STO@G nanoplatelets' even distribution inside the PVDF polymer, even at higher nanoparticle concentrations (10wt.%), revealing no porosity or morphological defects and demonstrating its potential for flexible dielectric capacitors. Thermogravimetric analysis (TGA) was used to assess the thermal stability of 10wt.% STO@G/PVDF nanocomposite films, demonstrating a positive impact on PVDF's thermal stability. Specifically, the thermal stability of PVDF was enhanced until 170 oC. These findings demonstrate that our approach provides a promising strategy to enhance the thermal stability of PVDF for various applications, including energy storage and conversion, sensors, and electronic devices, ultimately improving its reliability and durability by increasing its operational temperature range.

Potential of Lauryl Gallate as Stability and Recyclability Improver of Poly (Butylene succinate-co-adipate)

In the present study, Lauryl Gallate (LG), a natural antioxidant, was used to improve polymer thermal stability and recyclability of a biodegradable polyester as poly(butylene succinate-co-adipate) (PBSA). Neat PBSA and PBSA/LG (0.5 wt% LG) blends were processed by melt extrusion and subjected to multiple consecutive extrusion cycles at 170 °C to prevent the occurrence of thermo-oxidative radical degradation processes of the polymer. Thermal, rheological, morphological, FTIR, and GPC analyses showed the beneficial effect of LG in delaying PBSA thermo-oxidative degradation, reducing polymer fragmentation at low-mid molecular weights compared to the reprocessed virgin PBSA. The use of LG limits the drop of both complex viscosity η* and zero-shear stress viscosity η0 as well as the reduction of crystallinity degree and the enhancement of melt flow rate (MFR). This molecular degradation produces low molecular weight polymer fractions and oligomers that solely affect molten PBSA fluidity. In the presence of 0.5 wt% of LG, the processability of PBSA doubles from six (neat PBSA) up to twelve extrusions until presenting the first signs of degradation of the molten polymer while preserving the mechanical characteristics at the solid state. These mechanical properties remain equivalent to the neat PBSA (Young’s modulus 0.33 GPa, yield strength 19.2 MPa, stress at break 24.4 MPa, and elongation at break 350%). Consequently, LG can be successfully employed as a natural PBSA stabilizer to extend the polymer lifecycle and contribute to the circular economy practice within the processing and manufacturing industry, particularly in the field of PBSA agricultural applications and injection moulded disposable products.

A Thermal Analytical Study of LEGO® Bricks for Investigating Light-Stability of ABS.

Acrylonitrile butadiene styrene (ABS) is a thermoplastic polymer widely used in several everyday life applications; moreover, it is also one of the most employed plastics in contemporary artworks and design objects. In this study, the chemical and thermal properties of an ABS-based polymer and its photo-degradation process were investigated through a multi-analytical approach based on thermal, mass spectrometric and spectroscopic techniques. LEGO® building blocks were selected for studying the ABS properties. First, the composition of unaged LEGO® bricks was determined in terms of polymer composition and thermal stability; then, the bricks were subjected to UV-Vis photo-oxidative-accelerated ageing for evaluation of possible degradation processes. The modifications of the chemical and thermal properties were monitored in time by a multi-technique approach aimed at improving the current knowledge of ABS photodegradation, employing pyrolysis online with gas chromatography and evolved gas analysis, coupled with mass spectrometric detection (Py-GC-MS and EGA-MS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and corroborated by external reflection FT-IR spectroscopy. The multimodal approach provided new evidence on the two-step degradation pathway proposed for ABS, defining molecular markers for polybutadiene oxidation and styrene-acrylonitrile depolymerization. Moreover, the results highlighted the feasibility of correlating accurate compositional and thermal data acquired by bulk techniques with external reflection FT-IR spectroscopy as a non-invasive portable tool to monitor the state of conservation of plastic museum objects in-situ.

Molecular design of ferrocene-based novel polymer using click chemistry via chemoselective polymerization and investigation of electrical properties as organic Schottky diode

Organic Schottky diodes are electronic devices that consist of a metal–semiconductor junction formed with an organic polymer as the semiconductor material. This work synthesized cinnamic acid side chain bearing polymer and its ferrocene-modified polymer. Thermal stability, dielectric and electrical properties of the initial polymer and the modified one were examined and the addition of a ferrocene unit to the initial polymer clearly improved the optical and electrical properties of the target polymer. Due to the influence of ferrocene, the dielectric constant increased from 8.69 to 18.92. Additionally, it was discovered that the ac conductivity value raised from 6.40x10−9 to 2.64x10−8. The Al/modified-polymer/p-Si structure exhibits an ideality factor of 2.22, a barrier height of 0.61 eV, and a reverse bias current of 1.28 10−5 A in the dark, according to the I-V measurements. These results demonstrated the fabricated diodes have a rectifier behavior. This diode exhibits unique electrical properties due to the characteristics of the organic polymer.

Enhancement of piezoelectric β‐polymorph formation and properties of graphene oxide and PZT‐incorporated in PVDF‐HFP matrix for energy harvesting applications

AbstractThis paper presents and compares films made using the solution casting method with a mixture of poly (vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP), graphene oxide (GO), and lead zirconate titanate (PZT). The Hummers' method synthesized GO. Scanning electron microscopy (SEM), Fourier‐transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and tensile testing were realized. The developed composite films were found to have a coherent distribution of PZT and GO in PVDF‐HFP. After that, a gradual improvement, such as an increase in the quantity of β phase, produces high piezoelectric performance. Also, the PVDF‐HFP polymer's thermal stability improved. When 0.1 wt% of PZT/GO was added, the melting temperature increased from 140 to 143°C, and the crystallization temperature from 109 to 113°C. PVDF‐HFP elastic modulus and tensile strength were also considerably reduced as PZT/GO increased. As a result, this has enabled us to develop composite films with important properties that can be used as piezoelectric materials for energy harvesting.

Integrating stabilizer efficiency of secondary antioxidants to thermal, rheological, optical characterization and filterability study of polypropylene

Abstract The framework of the present study is based on investigation of different types of phosphorus based secondary antioxidants and their role in stabilization of polypropylene. Three different chemical entities i.e., Tris (2,4-di-tert-butylphenyl) phosphite, Tetrakis (2,4-di-tert-butylphenyl)-4,4-biphenyldiphosphonite and Bis (2,6-di-tert-butyl-4-methylphenyl pentaerythritol-diphosphite) have been studied for its efficiency as a secondary antioxidants or processing stabilizer. Thermal stability of polymer is predicted using degradation kinetics study and correlated with it’s optical, thermal and rheological response. To further evaluate performance of secondary antioxidants, thermogravimetry analysis was performed for polypropylene at three different heating rates and processed for iso-conversional analysis to get the kinetic parameters. Oxidation induction data and kinetic parameters have been related with efficiency of the stabilizers. Filtration study was also carried out to understand the efficacy of stabilizers during secondary process. Die pressure build up in filtration study is quantified and related with performance of secondary antioxidants.

SAFETY OF USING ISOPHTHALIC ACID AS A COMPONENT OF POLYMER MATERIALS

The widespread use of polymeric materials in various industries and fields of activity is explained by the thermal stability of polymers, their high strength characteristics, and the durability and reliability of synthetic materials. The introduction of additives can change the physical-mechanical, thermophysical, optical, electrical, frictional and other performance characteristics of the original (base) polymer. The purpose of the article is to investigate the safety of using isophthalic acid filler in a polymer composition. Methodology. Application of theoretical research methods, regulatory documents. Results. The spheres of polymeric materials application are considered. Ways of creating polymers with specified properties by introducing fillers into their composition, which change not only the operational characteristics, but also the physical and chemical characteristics of the original polymer are investigated. In view of the identification for danger of using isophthalic acid as a filler for phenylone, its physicochemical composition, stability, reactivity, toxicity, and environmental impact are studied. The measures and means of ensuring fire and explosion safety, means of controlling hazardous exposure, precautionary measures for personnel and personal protective equipment when working with isophthalic acid are considered. As a result of the research, it is possible to obtain an optimal polymer composition with improved plastic characteristics and safe properties. Scientific novelty. The possibility of obtaining an optimal polymer composition is shown: with improved plastic characteristics due to the addition of the biodegradable isophthalic acid filler fenilon to the polymer material; safe properties for humans and the environment, namely the absence of toxic substances release under the influence of heat, light and other external actions. Practical value. The resulting polycomposite material with updated plastic characteristics and safety properties can be used for further processing of secondary polymer raw materials.

Ameliorating the Mechanical Parameters, Thermal Stability, and Wettability of Acrylic Polymer by Cement Filling for High-Efficiency Waterproofing.

Acrylic polymer/cement nanocomposites in dark and light colors have been developed for coating floors and swimming pools. This work aims to emphasize the effect of cement filling on the mechanical parameters, thermal stability, and wettability of acrylic polymer. The preparation was carried out using the casting method from acrylic polymer coating solution, which was added to cement nanoparticles (65 nm) with weight concentrations of (0, 1, 2, 4, and 8 wt%) to achieve high-quality specifications and good adhesion. Maximum impact strength and Hardness shore A were observed at cement ratios of 2 wt% and 4 wt%, respectively. Changing the filling ratio has a significant effect on the strain of the nanocomposites. The contact angle was increased as the concentration of additives and cement increased, indicating that the synthesized coating is not hydrophilic and does not allow water permeability through it. The results show that the acrylic polymer/cement with a cement ratio of 8 wt% is the best nanocomposite for high-efficiency waterproofing.

Preparation of pH-Responsive Hydrogels Based on Chondroitin Sulfate/Alginate for Oral Drug Delivery.

This study investigates pH-sensitive hydrogels based on biocompatible, biodegradable polysaccharides and natural polymers such as chondroitin sulfate and alginate in combination with synthetic monomer such as acrylic acid, as controlled drug carriers. Investigations were conducted for chondroitin sulfate/alginate-graft-poly(acrylic acid) hydrogel in various mixing ratios of chondroitin sulfate, alginate and acrylic acid in the presence of ammonium persulfate and N′,N′-Methylene bisacrylamide. Crosslinking and loading of drug were confirmed by Fourier transform infrared spectroscopy. Thermal stability of both polymers was enhanced after crosslinking as indicated by thermogravimetric analysis and differential scanning calorimeter thermogram of developed hydrogel. Similarly, surface morphology was evaluated by scanning electron microscopy, whereas crystallinity of the polymers and developed hydrogel was investigated by powder X-ray diffraction. Furthermore, swelling and drug-release studies were investigated in acidic and basic medium of pH 1.2 and 7.4 at 37 °C, respectively. Maximum swelling and drug release were detected at pH 7.4 as compared to pH 1.2. Increased incorporation of hydrogel contents led to an increase in porosity, drug loading, and gel fraction while a reduction in sol fraction was seen. The polymer volume fraction was found to be low at pH 7.4 compared to pH 1.2, indicating a prominent and greater swelling of the prepared hydrogels at pH 7.4. Likewise, a biodegradation study revealed a slow degradation rate of the developed hydrogel. Hence, we can conclude from the results that a fabricated system of hydrogel could be used as a suitable carrier for the controlled delivery of ketorolac tromethamine.