Intrinsic Viscosity Research Articles

Synthesis and testing of latex properties of copolymers of ethyl or butyl acrylate with methyl or butyl methacrylate and methacrylic acid

AbstractThe results of a study on latexes obtained by emulsion copolymerization of acrylic, methacrylic and vinyl monomers without surfactants are presented. The monomers included ethyl acrylate and butyl acrylate, methyl and butyl methacrylate and methacrylic acid. The yield of the copolymerization reaction, the polymer concentration in the latex, the pH, surface tension, intrinsic viscosity number, Huggins constant, the molecular weight of the polymer and the particle size in the latex were determined. The stability of the latexes was tested by determining the values of non‐overt and overt coagulation thresholds. The values of the limiting equivalent conductivity and the anode zeta potential were determined. The relative hardness of latex membranes and their mass change after hot water extraction were investigated. The relationships between the properties of individual latexes were established. The main aim of the research was to determine the influence of copolymer composition on the electrokinetic properties of polymer particles in latex. They determine the possibility of developing a new type of paint for electrophoretic painting with the use of latexes. © 2022 Society of Industrial Chemistry.

Flow-induced "waltzing" red blood cells: Microstructural reorganization and the corresponding rheological response.

We investigate flow-induced structural organization in a dilute suspension of tumbling red blood cells (RBCs) under confined shear flow. For small Reynolds (Re = 0.1) and capillary numbers (Ca), with fully coupled hydrodynamic interaction (HI) and without interparticle adhesion, we find that HI between the biconcave discoid particles prompts the formation of layered RBC chains and synchronized rotating RBC pairs, referred here as "waltzing doublets." As the volume fraction ϕ increases, more waltzing doublets appear in RBC files. Stronger shear stress disrupts structural arrangements at higher Ca. We find that the flow-induced organization of waltzing doublets changes how the suspension viscosity varies with ϕ qualitatively. The intrinsic viscosity is particularly sensitive to microstructural rearrangement, increasing (decreasing) with ϕ at low (high) Ca that correlates with the change in the fraction of doublets. We verified flow-induced collective motion with comparison to two-cell simulations in which the cell volume fraction is controlled by varying the domain volume.

Production and Characterisation of Pectin from Cocoa Bean Shells

Cocoa bean shells constitute the major waste generated from the industrial processing of cocoa beans. The shells contain about 9% of pectin and extracting it would be of economic and ecological importance. However, limited knowledge on the characteristics of the pectin from cocoa bean shells and the extraction conditions, which would yield pectin of good quality and sufficient quantity, restrict the possible use of the shells as a source of commercial pectin. The objective of this study was to extract and characterise pectin from cocoa bean shells, with focus on finding the optimum extraction conditions. The conventional hot dilute acid extraction method was used. 12 M hydrochloric acid was used to acidify water to pH 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0. Extractions were carried out at temperatures of 60, 70, and 80 °C, for different times of 0.5, 1, and 2 h. The effects of each of the conditions on yield and other properties of pectin were evaluated. Depending on the conditions under which cocoa bean shells were treated, both high methoxyl and low methoxyl pectins were extracted. At the optimum conditions of pH 3.5, extraction time of 2 h and 80 °C extraction temperature, high methoxyl pectin was obtained. The yield was 4.7%, the degree of esterification was 68.9% and the anhydrouronic acid content was 71.2%. While the methoxyl content was 8.6%, the equivalent mass was found to be 805.8 g/eq. Moisture and ash contents were 6.7 and 10.3%, respectively, and the pH of the pectin hydrocolloid was 3.7. Fourier Transform Infrared (FT-IR) spectra confirmed the presence of functional groups found in the pectin structure. The intrinsic viscosity varied between 0.075–0.088 m3/kg and the molecular mass ranged from 23,470 - 42,384 g/mol. The results revealed that the shells are a viable source for commercial pectin, while necessary investigations focusing on the gelling, thickening, emulsifying, texturing, and stabilising potentials of the pectin from cocoa bean shells would inform of the areas of application

Synthesis of Biodegradable Polyester-Polyether with Enhanced Hydrophilicity, Thermal Stability, Toughness, and Degradation Rate.

Novel poly(butylene succinate-butylene furandicarboxylate/polyethylene glycol succinate) (PBSF-PEG) was synthesized using two-step transesterification and polycondensation in the melt. There are characterized by intrinsic viscosity, GPC, 1H NMR, DSC, TGA, tensile, water absorption tests, and water degradation at different pH. GPC analysis showed that PBSF-PEG had high molecular weight with average molecular weight (Mw) up to 13.68 × 104 g/mol. Tensile tests showed that these polymers possessed good mechanical properties with a tensile strength as high as 30 MPa and elongation at break reaching 1500%. It should be noted that the increase of PEG units improved the toughness of the polyester material. In addition, the introduction of PEG promoted the water degradation properties of PBSF, and the copolymer showed a significantly faster water degradation rate when the PEG unit content was 20%. This suggests that the amount of PEG introduced could be applied to regulate the water degradation rate of the copolymers. Hence, these new polymers have great potential for application as environmentally friendly and sustainable plastic packaging materials.

Integrated Approach to Eco-Friendly Thermoplastic Composites Based on Chemically Recycled PET Co-Polymers Reinforced with Treated Banana Fibres.

A major societal issue of disposal and environmental pollution is raised by the enormous and fast-growing production of single-use polyethylene terephthalate (PET) bottles, especially in developing countries. To contribute to the problem solution, an original route to recycle PET in the form of value-added environmentally friendly thermoplastic composites with banana fibres (Musa acuminata) has been developed at the laboratory scale. Banana fibres are a so far undervalued by-product of banana crops with great potential as polymer reinforcement. The melt-processing constraints of commercial PET, including used bottles, being incompatible with the thermal stability limits use of natural fibres; PET has been modified with bio-sourced reactants to produce co-polymers with moderate processing temperatures below 200 °C. First, commercial PET were partially glycolyzed with 1.3-propanediol to produce co-oligomers of about 20 repeating units, which were next chain extended with succinic anhydride and post-treated in a very unusual "soft solid state" process at temperatures in the vicinity of the melting point to generate co-polymers with excellent ductility. The molar mass build-up reaction is dominated by esterification of the chain ends and benefits from the addition of succinic anhydride to rebalance the acid-to-hydroxyl end-group ratio. Infra-red spectroscopy and intrinsic viscosity were extensively used to quantify the concentration of chain ends and the average molar mass of the co-polymers at all stages of the process. The best co-polymers are crystallisable, though at slow kinetics, with a Tg of 48 °C and a melting point strongly dependent upon thermal history. The composites show high stiffness (4.8 GPa at 20% fibres), consistent with the excellent dispersion of the fibres and a very high interfacial cohesion. The strong adhesion can be tentatively explained by covalent bonding involving unreacted succinic anhydride in excess during solid stating. A first approach to quantify the sustainable benefits of this PET recycling route, based on a rational eco-selection method, gives promising results since the composites come close to low-end wood materials in terms of the stiffness/embodied energy balance. Moreover, this approach can easily be extended to many other natural fibres. The present study is limited to a proof of concept at the laboratory scale but is encouraging enough to warrant a follow-up study toward scale-up and application development.

Influence of the Multiple Injection Moulding and Composting Time on the Properties of Selected Packaging and Furan-Based Polyesters

In recent years, there has been a trend toward replacing petrochemical raw materials with so-called “bio” plastics, i.e. plastics from renewable sources. Herein, the susceptibility of degradation in the compost heap of three types of packaging polyesters, by means of PET and biobased PEF and PLA, with other thermoplastic polyesters with more methylene groups (three and six) bio—(PTF and PHF, respectively) and petrochemically-based (PTT and PHT, respectively) has been studied. Two series of polymer materials based on ethylene, propylene, and hexamethylene glycols and two diesters (dimethyl terephthalate and dimethyl 2,5-furandicarboxylate) were thus obtained and compared with “double green” PLA. Moreover, the assessment of the influence of the subsequent processing cycle (injection moulding) on the utilitarian properties of these materials, constitutes the analogy to the subsequent recycling cycle. The susceptibility to degradation was assessed in the context of changes in the structure (analyzed by FTIR and DSC), intrinsic viscosity, and mechanical performance. In addition, chromatographic analysis of the solutions of the analyzed samples in methanol was carried out in order to determine whether and what low-molecular compounds were released from the analyzed polyesters. It has been shown that furan-based polyesters have great potential to replace materials based on dimethyl terephthalate-based polyesters.

Physicochemical and rheological characteristics of pectin extracted from renewable orange peel employing conventional and green technologies

Hydrochloric acid- (HAE), citric acid- (CAE) and microwave-assisted extraction (MAE) of pectins from orange peels, as a whole or their albedos, was performed. Pectin yield varied from 10.6 to 22.8%, galacturonic acid content (GalA) from 46 to 73.5%, intrinsic viscosity [η] from 0.3 to 0.8 dL/g and molecular weight from 5 to 15 kDa. All pectins were high methoxy pectins with a degree of esterification (DE) > 50% and their solutions presented acidic pH values. The studied properties were affected by both extraction conditions and raw material. The gelling and emulsifying properties of the pectins were also evaluated. HAE pectin-based emulsions were more stable and showed greater viscosity and lower conductivity. All pectins formed a gel network on cooling from 95 °C to 5 °C, which was thermally irreversible with the exception of CAE pectins that presented an increase of moduli at temperatures >40 °C. A thermal annealing behaviour was observed when gels were taken to high temperature and re-cooled. All gels exhibited great syneresis. Overall, the extracted pectins can be good candidates for the formation of food products of specific textural and rheological properties.

Impact of the solvent properties on molecular interactions and phase behaviour of alginate-gelatin systems

Alginate-gelatin systems are used in a wide range of applications, e.g., foods, cosmetics, drugs, and medicine. To target the techno-functionalities of alginate-gelatin systems such as texture, stability, or appearance it is necessary to understand the structure formation of gel systems, which is influenced by the molecular interactions and the phase behaviour. Therefore, the aim of this study was to characterise the molecular interactions and phase behaviour of dilute alginate-gelatin systems. For this purpose, we analysed alginate, gelatin A and their mixtures at pH 7. First, we characterised the effect of the sodium chloride concentration on the single polymer solutions by measuring the critical overlap concentration, the zeta potential, intrinsic viscosity, the Huggins coefficient as well as the molecular weight and the second virial coefficient. To gain a better understanding of the molecular interactions between alginate and gelatin, we determined the Huggins coefficient and the interaction parameter by Wolf as a function of mixing ratio, NaCl and urea concentration. Additionally, we calculated the second cross-virial coefficient. Lastly, we characterised the influence of the interactions on the secondary structure of gelatin by Fourier-transform-infrared-spectroscopy. The attractive interactions between alginate and gelatin potentially enabling the formation of soluble complexes, were demonstrated as deviations from additivity of intrinsic viscosity and negative cross-virial coefficients. Interestingly, the Wolf interaction parameter was affected by the NaCl concentration and the mixing ratio, whereas the presence of urea showed no impact. This indicates that the attractive interactions of alginate and gelatin A at pH 7 is rather caused by electrostatic interactions than hydrogen bonds. The present study clarifies the relevance of hydrogen bonds and electrostatic interactions as well as the impact of mixing ratio and solvent properties on the phase behaviour of alginate-gelatin systems. The insights contribute to a better understanding of the structure formation of concentrated alginate-gelatin systems, levelling the path to specific modifications of functionality.

Rheological investigation on the associative properties of poly(vinyl alcohol) solutions

We report intrinsic viscosity and flow curve measurements on a set of five industrial poly(vinyl alcohol) (PVOH) samples, with varying degree of hydrolysis, molecular weight, and concentration in two solvents: water and dimethyl sulfoxide (DMSO). Aqueous poly(vinyl alcohol) solutions exhibit clear features of associative polymers, and the hydroxyl-carbonyl hydrogen bonds seem to dominate polymer chain associations. We propose a “sticky-blob” model, applicable to any associating polymer solution with many stickers inside each correlation blob, which predicts the concentration dependence of the specific viscosity and the chain relaxation time in the entanglement regime. When PVOH polymers are dissolved in DMSO, a strong hydrogen bond acceptor, chain-chain associations are fully prevented for all relevant degrees of hydrolysis. The specific viscosity and the relaxation time of the chain recover the expected concentration dependences for nonassociating flexible polymers in DMSO. The same concentration dependences are exhibited by literature data on 100% hydrolyzed PVOH in water, as the acetate content, dominating interchain associations, is zero. Comparing entangled aqueous and DMSO solutions at the same concentration enables the experimental measure of the time delay due to associations as the ratio between the terminal relaxation time of solutions in water and DMSO. The concentration dependence of such a time delay was also captured by the simple sticky-blob model introduced in this work.

Investigation of Hydroxyl Radical Yield in an Impact-Jet Hydraulic Cavitator

Hydroxyl radical (·OH) is a key component that leads to the cleavage of the glycosidic bond in the process of chitosan (CS) degradation by hydrodynamic cavitation (HC). In this paper, methylene blue (MB) was selected as the trapping agent of ·OH and the yield of ·OH in an impact-jet hydraulic cavitator was investigated. The results showed that the cavitation intensity and the number of passes (N) were the two main factors affecting the yield of ·OH. A smaller cavitation number (Cv) or a larger N indicated that more ·OH can be produced. Based on the dimensionless number correlation method, the yield of ·OH was correlated with Cv, N, Euler number (Eu), Reynolds number (Re), and a dimensionless parameter (γ), and a prediction model of ·OH yield was established. The relative deviations between the experimental and calculated values of the ·OH yield were basically within 10% by the prediction model. On the basis of the prediction model, the yield of ·OH produced in the process of CS degradation by HC was obtained. The results showed that the predicted yield of ·OH was significantly correlated with the intrinsic viscosity reduction rate of CS. It was suggested that the prediction model of ·OH yield based on the MB solution can be used to calculate the ·OH yield during the degradation of low concentration CS by HC.

Conformation and Structure of Hydroxyethyl Cellulose Ether with a Wide Range of Average Molar Masses in Aqueous Solutions

The solution properties of a water-soluble chemically modified cellulose ether, hydroxyethyl cellulose (HeC), were examined using static light scattering (SLS), dynamic light scattering (DLS), small-to-wide-angle neutron scattering (S-WANS), small-to-wide-angle X-ray scattering (S-WAXS) and viscometric techniques at 25 °C. The examined HeC samples had average molar substitution numbers ranging from 2.36 to 2.41 and weight average molar masses (Mw) that fell within a wide range from 87 to 1500 kg mol-1. Although the relationship between the determined radius of gyration (Rg) and Mw was described as Rg ∝ Mw~0.6, as is observed usually in flexible polymer solutions in good solvents, the observed scattering vector (q) dependencies of excess Rayleigh ratios were well interpreted using a rigid rod particle model, even in high-Mw samples. Moreover, the ratios of the formed particle length (L) evaluated assuming the model for rigid rods to the determined Rg showed the relationship LRg-1 ~ 3.5 irrespective of Mw and were close to those theoretically predicted for rigid rod particle systems, i.e., LRg-1 = 12. The observed SLS behavior suggested that HeC molecules behave just like rigid rods in aqueous solution. As the L values were not simply proportional to the average molecular contour length calculated from the Mw, the chain conformation or structure of the formed particles by HeC molecules in aqueous solution changed with increasing Mw. The q dependencies of excess scattering intensities observed using the S-WANS and S-WAXS experiments demonstrated that HeC molecules with Mw less than 200 kg mol-1 have a diameter of ~1.4 nm and possess an extended rigid rod-like local structure, the size of which increases gradually with increasing Mw. The observed Mw dependencies of the translational and rotational diffusion coefficients and the intrinsic viscosity of the particle suspensions strongly support the idea that the HeC molecules behave as rigid rod particles irrespective of their Mw.

One-Pot Synthesis of Hyperbranched Polyurethane-Triazoles with Controlled Structural, Molecular Weight and Hydrodynamic Characteristics.

We report a simple and convenient approach to the one-pot synthesis of hyperbranched polyurethane-triazoles with desirable properties. This method is based on in situ generation of an AB2 + A2 + B4 azide-acetylene monomer mixture of known composition, due to quantitative reactions of urethane formation between isophorone diisocyanate (IPDI), 1,3-diazidopropanol-2 (DAPOL) (in the first stage) and propargyl alcohol (in the second stage). The obtained monomer mixture can be involved in step-growth polymerization by azide-alkyne cycloaddition without additional purification (in the third stage). The properties of the resulting polymers should depend on the composition of the monomer mixture. Therefore, first the model revealing the correlation between the monomer composition and the ratio and reactivity of the IPDI and DAPOL active groups is developed and proven. In addition, the newly developed structural kinetic model considering the substitution effect at polyaddition of the complex mixture of monomers allows the prediction of the degree of branching of the target polymer. Based on our calculations, the hyperbranched polyurethane-triazoles were synthesized under found conditions. All products were characterized by 1H NMR, FTIR, SEC, DLS, DSC, TGA and viscometry methods. It was shown that the degree of branching, molecular weight, intrinsic viscosity, and hydrodynamic radius of the final hyperbranched polymers can be specified at the first stage of one-pot synthesis. The obtained hyperbranched polyurethane-triazoles showed a degree of branching from 0.21 to 0.44 (calculated DB-0.25 and 0.45, respectively).

Closing the cycle: Enzymatic recovery of high purity glucose and polyester from textile blends

Enzymatic recovery of glucose and polyester from cotton / polyester textile blends was investigated. Grinding to a fibre length of 0.5 mm increased cellulose recovery from 53.6 to 85.4%. Subsequent steam explosion combined with alkaline pre-treatment led to complete hydrolysis of cotton while sonication and solvent pre-treatments were less effective. Comparison of weight loss and HPLC analysis indicated the presence of cellu-oligomers besides glucose. Recovery of enzymes via ultrafiltration only caused less than 5% in activity loss when used in five subsequent hydrolysis cycles. Similar bioethanol yields were determined for the hydrolysate and commercial glucose as carbon source for S. cerevisiae. The absence of peaks at 3600 cm−1 and 3000 cm−1 in FT-IR analysis and differential scanning calorimetry (DSC) analysis indicated no cellulose present in the polyester fraction. Re-granulation led to an intrinsic viscosity of 0.6 dl g−1 suitable for fibre spinning and production of towels thereby closing the cycle.

Effect of solution pulsed plasma process on the degradation and physicochemical properties of pectin

Pectin was degraded by solution pulsed plasma (SPP). The impacts of discharge voltage and the distance between the electrodes on pectin degradation and its steady shear flow behavior and characterization were investigated. The results showed that the influence of the discharge voltage was higher than that of the distance between the electrodes. The stronger discharge voltage and the narrower distance between the electrodes presented the lower intrinsic viscosity, the greater shear-thinning capacities, and the stronger viscoelastic behavior. FT-IR and 1H NMR analysis demonstrated that SPP treatment did not damage the main structure of pectin. XRD, SEM and HPSEC-MALL analysis revealed that the crystallinity, Mw and <S2>z1/2 of pectin gradually decreased with the increasing discharge voltage and decreasing the distance between the electrodes. The depolymerized pectin molecules exhibited a hard sphere conformation in the aqueous solution. A higher degradation effect had a greater influence on the conformation of pectin.

The effect of freezing-assisted cross-linking on structural and rheological properties of potato starch

In order to achieve preparation of cross-linked (CL) potato starch with the maximum degree of substitution, freezing pre-treatment (FS) in different modes as three days freezing (3D), two freezing-thawing cycles (3D + 3D) and 6 days freezing (6D) were conducted. Thereafter, native, frozen and cross-linked starches were characterized for morphological, structural and pasting properties as well as alkaline and intrinsic viscosity. Regarding obtained result, freezing pre-treatment as 3D + 3D was found to be an efficient method to achieve high level of cross-linking than native and other modes of freezing pre-treatments when exposed to POCl3 reagent. The crystallinity (%) and ratio of 1047/1022 cm−1 increased from 38.6 % and 1.112 (native potato starch; NPS) to 41.6 % and 1.269 (cross-linked native potato starch; CL) and 41.3 and 1.292 (cross-linked freeze- thawed starch 3D + 3D + CL) after being treated with POCl3. Data obtained by intrinsic viscosity was in line with the power-law model. Cross-linked starch with POCl3 exhibited the lowest k value and the highest n value, implying lower shear-thinning behavior of cross-linked starch after freezing pre-treatment than CL native starch. To sum up, low peak viscosity (determined by RVA) and intrinsic viscosity (by U-tube viscometer) could also explain the high level of cross-linking and low swelling power of 3D + 3D + CL.

Prediction of the Rheological Properties of Fresh Cementitious Suspensions Considering Microstructural Parameters.

Supplementary cementitious materials (SCMs) are commonly used to partially replace cements. Although it is necessary to investigate the rheological properties of the individual supplementary cementitious materials (SCMs) for understanding complex rheological behaviors of the blended mixes, the study on the investigation of rheological properties of various SCMs such as fly ash, blast-furnace slag, and silica fume, according to various solid volume fractions and prediction models is fairly limited. This study investigated the rheological properties of non-blended cementitious suspensions with Portland cement (PC), fly ash (FA), blast-furnace slag (BS), and silica fume (SF) materials in the experiments and predicted using YODEL (Yield stress mODEL) and Krieger–Dougherty’s (K–D’s) equation. Experiments were designed with various solid volume fractions () from 0.28 to 0.44, and the rheological properties of all cementitious suspensions were noted to increase with increasing , showing an improved flowability at low . YODEL, derived from the first principles considering particle-size distributions, interparticle forces and microstructural parameters predicted the yield stress. The YODEL predictions were consistent with the experiments with a positive correlation coefficient of above 0.96. K–D’s equation with the maximum particle fractions and intrinsic viscosity as key parameters predicted the plastic viscosity. The K–D’s equation predictions match up with the experiments with a positive correlation coefficient of above 0.94. Both models showed more quantitative predictions without any fitting parameters and could be applied to any multimodal powder suspensions.

Sulfated Polysaccharides from Chaetoceros muelleri: Macromolecular Characteristics and Bioactive Properties.

Simple SummaryAlgae are an important source of bioactive compounds. The interest in microalgae is increasing due to their high-value products and the advantage of biomass cultivation under controlled conditions. Polysaccharides are released by algae and microalgae species and have been reported to have bioactivities found beneficial to human health. Despite the recognized importance of these organisms, the structure of polysaccharides in microalgae has been practically unexplored in contrast to that of macroalgae. Only a few microalgae polysaccharide structures have been solved due to the difficulties in the extraction of pure samples and the complexity of their chemical structures. Reports emphasize how the molecular weight, the content of sulfate groups, and the negative charge may be responsible for their multiple bioactivities. To better understand the uses and potential applications of extracellular polysaccharides, it is necessary to know their structure and physicochemical properties, which include molecular weight and chain conformation, since they are decisive in their biochemical behavior.In the present study, a culture of Chaetoceros muelleri, a cosmopolitan planktonic diatom microalga present in the Sea of Cortez, was established under controlled laboratory conditions. A sulfated polysaccharide (CMSP) extraction was carried out from the biomass obtained, resulting in a yield of 2.2% (w/w of dry biomass). The CMSP sample was analyzed by Fourier transform infrared spectroscopy, showing bands ranging from 3405 to 590 cm−1 and a sulfate substitution degree of 0.10. Scanning electron microscopy with elemental analysis revealed that the CMSP particles are irregularly shaped with non-acute angles and contain sulfur. High-performance liquid chromatography coupled to a dynamic light-scattering detector yielded molecular weight (Mw), polydispersity index (PDI), intrinsic viscosity [η], and hydrodynamic radius (Rh) values of 4.13 kDa, 2.0, 4.68 mL/g, and 1.3 nm, respectively, for the CMSP. This polysaccharide did not present cytotoxicity in CCD-841 colon cells. The antioxidant activity and the glycemic index of the CMSP were 23% and 49, respectively, which gives this molecule an added value by keeping low glycemic levels and exerting antioxidant activity simultaneously.

Extraction and characterization of chitin and chitosan from Nile tilapia scale in Lake Chamo, Arba Minch and their application in clarification of apple juice

AbstractFish and seafood processing industries generate large quantities of waste, which are at the origin of several environmental, economic and social problems. However, fish waste contains high value‐added substances such as collagen, gelatin, chitin and chitosan. In Ethiopia, Arba Minch is one of the leading areas of fish production zone, and hence, everyday lot of fish waste has been generated due to this. This work has focused on the extraction and characterization of chitin and chitosan from fish wastes (Nile tilapia). The chitin and chitosan extracted were characterized by analyzing parameters such as percentage yield, moisture and ash content, solubility, degree of deacetylation, water binding capacity, fat binding capacity, intrinsic viscosity and Molecular weight (Mw). The results obtained from this study show that the yield of chitin and chitosan was 29.88 ± 0.01% and 15.87 ± 0.14%, respectively. The moisture and ash content, DD, solubility, FBC, WBC, intrinsic viscosity and Mw of the extracted chitosan were found to be 6.79 ± 0.40%, 1.22 ± 0.16%, 85.25 ± 0.28%, 94.3 ± 0.99%, 391.17 ± 0.13%, 461.34 ± 0.42%, 6.832 ± 0.0101 and 3514.730 ± 1.1 g/mol, respectively. The chitosan was then employed for apple juice clarification and the reduction in total soluble solids value from (12.67 to 9.20), titratable acidity (2.38 to 1.61) and turbidity (320.2 to 86.6) after treatments have confirmed their effectiveness on apple juice clarification. The reduction in titratable acidity has been supported by increase in pH value (3.19 to 4.29). The sensory evaluation of control juice and chitosan‐added juice samples was performed, and it has been observed that chitosan concentration of up to 0.25 g/L was well accepted by the consumers.Novelty impact statement The current study is the first kind of attempt to analyze the different physicochemical properties of chitin and chitosan obtained from Nile tilapia fish scale wastes, from Lake Chamo, Arba Minch. It also throws light on how fish scale wastes can be converted into useful products like chitin and chitosan. The application of extracted chitosan in apple juice clarification has been successfully demonstrated in the study.

Influence of Chain Extenders on Recycled Standard and Opaque PET Rheology and Melt-Spun Filament Properties

This work aims to evaluate the spinnability of recycled poly(ethylene terephthalate) (rPET) modified by chain extenders. Pyromellitic anhydride (PMDA), JONCRYL ADR 4400, 2,2′-bis(2-oxazoline) (BOZ), and 1,3-phenylene-bis-oxazoline (PBO) were used from 0.1 to 1 wt% on transparent postconsumer PET bottle flakes and opaque rPET flakes containing TiO2 particles. The created molecular architectures were characterized in the first section. Second, their spinnability was assessed via a pilot high-speed spinning process. The corresponding shear rheology, intrinsic viscosity, and elongational rheology were reported. It was observed that PMDA and JONCRYL induce a more drastic increase in melt strength and melt elasticity than BOZ and PBO due to chain branching. In a second step, melt-spun filaments were produced with a low content of chain extenders on standard rPET and opaque rPET matrices. Finally, their degree of crystallinity, molecular orientation, and mechanical properties were determined. PMDA and JONCRYL strongly decrease the spinnability and, consequently, the properties of filaments. However, BOZ improves the opaque rPET filaments’ tenacity while decreasing their degree of crystallinity.

Stress Relaxation Behavior of Poly(Methyl Methacrylate)/Graphene Composites: Ultraviolet Irradiation.

The graphene/poly (methyl methacrylate) (PMMA) composites are a promising candidate for electronic, optoelectrical, and environmental applications. Understanding the mechanical degradation of PMMA-based materials is of practical importance in improving the reliability and lifespan of the associated structures and systems. In this study, we investigate the effects of functionalized graphene (FG) and UV irradiation on the stress–relaxation of PMMA. Uniaxial tensile and stress –relaxation tests are performed to evaluate the mechanical properties of the composites. The mechanical strength and elongation at the break increase with the graphene concentration but decrease with the increase of the irradiation dose. Raman spectroscopy and intrinsic viscosity measurement are applied to examine the root cause of the degradation in the composites. UV irradiation leads to polymer chain scission and loss of molecular weight. The Kelvin representation of the standard linear solid model (SLSM) is used to describe the stress–relaxation curves of the composites. The value of the elastic modulus in the Kelvin element decreases with the increase in temperature. The viscosity follows the Arrhenius equation. The activation energy of viscosity increases with the increasing FGs concentration because the FGs hinder the chain motion of PMMA. However, UV irradiation makes chain scission of PMMA/FGs composite so that the polymer chain moves more easily and the activation energy of stress relaxation lowers. The steady-state stress follows the van ’t Hoff equation that stress relaxation is an exothermal deformation process. Although Maxwell’s representation of SLSM is mathematically identical to the Kelvin representation of SLSM, the former cannot interpret the stress–relaxation behavior of PMMA/FGs composite, which is against the concept of Young’s modulus as a decreasing temperature function.