Loss Modulus Curves Research Articles

No yield stress required: Stress-activated flow in simple yield-stress fluids

An elastoviscoplastic constitutive equation is proposed to describe both the elastic and rate-dependent plastic deformation behavior of Carbopol® dispersions, commonly used to study yield-stress fluids. The model, a variant of the nonlinear Maxwell model with stress-dependent relaxation time, eliminates the need for a separate Herschel–Bulkley yield stress. The stress dependence of the viscosity was determined experimentally by evaluating the steady-state flow stress at a constant applied shear rate and by measuring the steady-state creep rate at constant applied shear stress. Experimentally, the viscosity’s stress-dependence was confirmed to follow the Ree–Eyring model. Furthermore, it is shown that the Carbopol® dispersions used here obey time-stress superposition, indicating that all relaxation times experience the same stress dependence. This was demonstrated by building a compliance mastercurve using horizontal shifting on a logarithmic time axis of creep curves measured at different stress levels and by constructing mastercurves of the storage- and loss-modulus curves determined independently by orthogonal superposition measurements at different applied constant shear stresses. Overall, the key feature of the proposed constitutive equation is its incorporation of a nonlinear stress-activated change in relaxation time, which enables a smooth transition from elastic to viscous behavior during start-up flow experiments. This approach bypasses the need for a distinct Herschel–Bulkley yield stress as a separate material characteristic. Additionally, the model successfully replicates the observed steady-state flow stress in transient-flow scenarios and the steady-state flow rate in creep experiments, underlining its effectiveness in capturing the material’s dynamic response. Finally, the one-dimensional description is readily extended to a full three-dimensional finite-strain elastoviscoplastic constitutive equation.

An acrylic resin system for in‐situ pultrusion: Curing performances and rheology

AbstractIn recent years, the use of low viscosity and in‐situ polymerizable thermoplastic acrylic resins for advanced fiber reinforced composites has grown, specially to address the difficulty of fiber impregnation with high‐melt viscosity thermoplastic polymers. The present work investigated the curing kinetics, chemo‐rheology of an acrylic resin system for in‐situ pultrusion, and proposed the corresponding constitutive models. First, the curing kinetics was studied with the differential scanning calorimetry experiments. The viscosity development was obtained by a rheometer as functions of the degree of cure (DOC) and temperatures. The gelation point was acquired from the intersection point of storage and loss modulus curves through dynamic mechanical analysis test, which occurs at DOC of 0.65 determined by the cure kinetics model. Through the dynamic mechanical analysis, a four step cure hardening modulus model (modified CHILE approach) was proposed. The aforementioned models were applied in a case study to evaluate the influence of process parameters on the DOC, viscosity and physical behavior of the acrylic resin system in the pultrusion die.Highlights Material characterizations of an acrylic resin system are investigated. The cure kinetics and viscosity and elastic modulus models are proposed. A pultrusion case study is given.

Physical, structural and thermal properties of bio-phenolic/epoxy polymers blends

Research on polymer has increased to produce a material that has better performance at a lower price. Blending different types of polymer resin in a single system can improve the overall performance of the composite. The effects of bio-phenolic on epoxy's physical characteristics, FTIR, dynamic mechanical properties, thermal stability, and differential scanning calorimeter were explored in this work. Different loadings of Bio-phenolic were added into epoxy resin, which were 5 wt% (P-5), 10 wt% (P-10), 15 wt% (P-15), 20 wt% (P-20) and 25 wt% (P-25). As a control, pure bio-phenolic (P) and epoxy (E) were fabricated as well. The following tests were performed: density, void content, water absorption, FTIR, Dynamic mechanical analysis (DMA), thermal gravimetry analysis (TGA), and differential scanning calorimeter (DSC). The experimental density of the fabricated polymer is slightly lower compared to the theoretical density. P-25 has the highest experimental density which is 1.12 g/cm3. The void content of the polymer blends is less than 5% and the lowest is shown by P-5 which is 2.49%. The water absorption is decreased with the addition of bio-phenolic and the water absorption of the polymer is less than 1%. The dynamic mechanical analysis reveals that the incorporation of bio-phenolic into epoxy has improved the storage modulus and loss modulus. The glass transition temperature of the polymer blends from DSC is between 61.70 ℃ and 62.32 ℃. While glass transition of polymer blends form loss modulus curve is between 64.97 ℃ and 75.69 ℃. As the bio-phenolic content of polymer blends improved, so did their thermal stability. The FTIR spectra reveal the peak intensity of a few functional groups has decreased with the increasing bio-phenolic content, and this indicates that there is a reaction between the bio-phenolic and epoxy.

Elucidation of segmental relaxations of silica‐filled cis‐polybutadiene rubber composites

AbstractThere has been a lot of interest in characterizing polymer chain dynamics of rubber compounds because it is thought to underpin the exceptional mechanical properties of composites. We studied the effect of precipitated silica on segmental mobility of cis‐polybutadiene rubber by using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). It was found that the calorimetric glass and melting transitions of silica‐filled master batch materials were essentially identical to those of the gum rubber, showing no dependence of silica loading and silane treatment. And, we observed in calorimetric measurement a change in the melting transition step for the vulcanizates. The results were correlated to the change of chemical crosslinks caused by various factors filler agglomeration and adsorption effect that tended to decrease chemical crosslink density and silane modification increased it. The DMA results demonstrated that the second peak in loss modulus versus temperature curve for the quenched vulcanizates was assigned to melting peak, and this peak disappeared at a slow cooling rate, which coincided well with DSC results. Moreover, crystalline parts constrained amorphous regions such that the glass transition temperature was raised for the cooled vulcanizates with high chemical crosslinks.

Eco-friendly, disposable bamboo fiber dishware: Static and dynamic mechanical properties and creep behavior

The global ban on plastics and the COVID-2019 epidemic have accelerated the demand for eco-friendly disposable dishware. As an alternative to plastic, the characterization of low-cost, widely-sourced, and sustainable plant fibers for degradable, eco-friendly dishware is urgently needed. In this study, bamboo fiber dishware (BFD) and poly lactic acid (PLA) dishware were investigated by exploring how the properties of their microstructures affect their mechanical properties. Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) were used to characterize the thermal decomposition behavior and dynamic viscoelasticity of both dishware types. Their modulus reductions were predicted using the accelerating creep mode, according to the time-temperature equivalence principle. The results showed that (1) the eco-friendly BFD was light weight and strong. Its specific strength, specific modulus were 4.50 and 3.09 times higher than those of PLA dishware, respectively. The efficient three-dimensional structure formed by the bamboo fibers and held together by hydrogen bonding played an important role in maintaining the excellent physical and mechanical properties. (2) The BFD and PLA dishware exhibited glass transition temperatures of 63.2 °C and 54.7 °C, respectively, according to the loss modulus curves, and their activation energies were 70.76 kJ/mol and 132.53 kJ/mol, respectively. Compared to the PLA dishware, the thermal decomposition behavior and storage modulus of the BFD were showed a lower sensitivity to temperature. (3) The time-temperature principle could be applied to the long-term creep prediction of BFD and PLA dishware. It showed that BFD exhibited a greater creep resistance in protecting food. • BFD’s specific strength and modulus were 4.50 and 3.09 times higher than PLA. • BFD could maintain high storage modulus at high temperature than PLA. • BFD had better creep resistance than PLA after a long time.

A rheological method to characterize the molecular weight changes of polyamide 1012 during solid state polymerization

AbstractIn this study, a fast and convenient method that can characterize the molecular weight (MW) and its distribution (PDI) of polyamide 1012 after the solid‐state polymerization (SSP) was proposed with the rheological technique. Conventionally, polyamides have to be chemically modified to become soluble in an organic solvent suitable for the Gel Permeation Chromatography (GPC) measurement. Herein, to avoid the complex operation of chemical modification, the quantitative correlations between the rheological properties such as zero‐shear viscosity, complex viscosity, the frequency and modulus at the crossover point between the storage and loss modulus curves, and the obtained MW and PDI were established. Thus, without chemical modifications, the characterization of PA1012 during SSP becomes convenient and time saving, which is more approach to the real “on‐line” control of SSP. The lamellar thickening and SSP occur simultaneously above Tg during SSP. Its influence on the final results of SSP was studied. Furthermore, the impact of crystallinity of the raw materials on the SSP behavior was also investigated. The higher crystallinity can lead to a decrease in the SSP rate and final molecular weight and molecular weight distribution.

Influence of magnetic interaction on configurational-entropy-suppressed β -relaxations in FeNi-based metallic glasses

In this article, we studied the effect of magnetic interaction on β-relaxations of FexNi72−xSi4.8B19.2Nb4 (x = 0, 10, 30, 50, 72) metallic glasses (MGs). It is found that, with the substitution of Fe by Ni, the β-relaxation changes from a shoulder to an excess wing, suggesting an entropic effect on the suppression of β-relaxation. A peak caused by ferromagnetic transformation appears in the loss modulus curve of Fe30Ni42Si4.8B19.2Nb4 MG with suppressed β-relaxation, which is sensitive to stress and strain. In addition, the β-relaxation can be further varied by annealing under a transverse or longitudinal magnetic field. The results suggest that the entropy-suppressed β-relaxation in MGs can be affected by magnetic interaction that could help to improve their mechanical properties.

Effects of compatibilizers on microstructural and viscoelastic properties of polypropylene/polybutadiene thermoplastics vulcanizates

AbstractCompatibilized thermoplastic vulcanizates (TPVs) based on polypropylene (PP) and polybutadiene rubber (PBR) were developed through the melt‐mixing method, and their morphological, rheological, and dynamic mechanical properties were investigated. The composition of PBR/PP blends (30/70 and 40/60) was designed in a way to study the interrelationship between the compatibilizer content and blend composition. In this study, a hydrocarbon resin (MS 40) was employed as the compatibilizer. Based on morphological analysis, the addition of compatibilizer in both blend compositions led to a finer and more uniform distribution of rubber domains; however, only for 40/60 composition, the higher content of compatibilizer caused the formation of a co‐continuous morphology. Both dynamic and static rheology results were highly susceptible to the compatibilizer content and blend composition. According to the storage and loss modulus curves, the incorporation of PBR into PP resulted in a significantly enhanced elastic response with 30/70 composition showing lower elasticity. The viscosity upturn in complex viscosity curves indicated the formation of a three‐dimensional network of dispersed rubber domains within the matrix, which led to the appearance of a highly elastic response. Based on the dynamic mechanical analysis, the highly restricted macromolecular motions upon the addition of a compatibilizer confirmed the enhanced compatibility of TPVs.

Thermal, Mechanical and Chemical Analysis of Poly(vinyl alcohol) Multifilament and Braided Yarns.

Poly(vinyl alcohol) (PVA) in multifilament and braided yarns (BY) forms presents great potential for the design of numerous applications. However, such solutions fail to accomplish their requirements if the chemical and thermomechanical behaviour is not sufficiently known. Hence, a comprehensive characterisation of PVA multifilament and three BY architectures (6, 8, and 10 yarns) was performed involving the application of several techniques to evaluate the morphological, chemical, thermal, and mechanical features of those structures. Scanning electron microscopy (SEM) was used to reveal structural and morphological information. Differential thermal analysis (DTA) pointed out the glass transition temperature of PVA at 76 °C and the corresponding crystalline melting point at 210 °C. PVA BY exhibited higher tensile strength under monotonic quasi-static loading in comparison to their multifilament forms. Creep tests demonstrated that 6BY structures present the most deformable behaviour, while 8BY structures are the least deformable. Relaxation tests showed that 8BY architecture presents a more expressive variation of tensile stress, while 10BY offered the least. Dynamic mechanical analysis (DMA) revealed storage and loss moduli curves with similar transition peaks for the tested structures, except for the 10BY. Storage modulus is always four to six times higher than the loss modulus.

Influence of temperature and magnetic field on rheological behavior of ultra-sonicated and oleic acid coated cobalt ferrite ferrofluid

The research work examines the influence of magnetic field and temperature on the magneto viscous and magneto viscoelastic nature of cobalt ferrite ferrofluid (FF). Steady rotational and oscillatory rheological measurements which examined the rheological responses of the fluid have been performed. A steady state flow was established through the application of suitable relaxation modulus and attempt was made to regulate unwanted oscillatory behavior by application of damping function. The particles were ultra-sonicated and coated with oleic acid to minimize agglomeration and improve fluid stability and its rheological behavior. The fluid is underdamped at high shear rate and high magnetic field due to damping factor that is less than one but overdamped behavior was obtained at low shear rate. Storage modulus (G’) and loss modulus were used to examine the viscoelastic behavior of the fluid. This fluid is accurately viscoelastic, because it exhibits of both elastic and viscous behaviors. Storage modulus is higher than loss modulus as a result of dominant magnetostatic forces at low strain rate. A crossover point was formed at critical strain due to overlapping of loss and storage modulus curves at high strain rate, this effect indicates the formation of phase transition. This occurred due to dominant hydrodynamic forces over magnetostatic forces. Magnetic effect revealed a steady increase in viscous effect which is as a result of formation of enhanced chain-like structure and strong particle aggregation. Enhanced viscous effect was shown in the presence of low temperature, low angular frequency and high applied magnetic field.

Dynamic Moduli of Polybutylene Terephthalate Glass Fiber Reinforced in High-Temperature Environments.

The aim of this work was to show the evolution over time of the dynamic moduli in components made of Polybutylene Terephthalate reinforced with glass fiber when they are held to temperatures close to the glass transition temperature over time. For this purpose, PBT samples reinforced with short, glass fibers of Ultradur® material with 0%, 20%, and 50% in weight content were tested. Dynamic moduli showed an increment with glass fiber content showing a nonlinear behavior with the temperature. The evolution of storage modulus was depicted by means of a modified law of mixtures with an effectiveness factor depending on temperature and fiber content, whereas the evolution over time was obtained with a time–temperature transformation generated with the TTS Data Analysis software of TA-instruments for a given temperature. Storage modulus showed a linear relationship with glass fiber content when components were held to temperatures near to their respective glass transition temperature, obtained from the maximum of loss modulus curve with temperature. In summary, the value and evolution of dynamic moduli of PBT samples improved with glass fiber content, allowing us to increase the durability of components when they are submitted to high-temperature environments.

Material characterization of a pultrusion specific and highly reactive polyurethane resin system: Elastic modulus, rheology, and reaction kinetics

This study presents a detailed material characterization study of a pultrusion specific polyurethane resin system. Firstly, the chemical behaviour was characterized by utilizing differential scanning calorimetry. The cure kinetics was fitted well to an autocatalytic cure kinetics model with Arrhenius temperature dependency. The resin system did not show any inhibition time. Then, the viscosity evolution was observed using a rheometer. From these measurements, the gelation point was estimated from the criterion of cross-over point of storage and loss modulus curves. The corresponding cure degree of gelation point was found to be 0.79 using the cure kinetics model. The complex viscosity evolution through dynamic scans was predicted well with a cure degree and temperature dependent viscosity model. The elastic modulus and glass transition temperature of fully and partially cured samples were measured by means of DMA in tension mode. A five step cure hardening instantaneous linear elastic model was fitted well to a wide range of cure degree values after gelation. Lastly, the fitted material models were employed in a case study of a typical pultrusion process to visualize the effects of pulling speed on the material property evolution.

Influence of polycaprolactone and titanium phosphate in the composites based upon recycled polypropylene

The influence of polycaprolactone (PCL) and nano titanium phosphate, pristine (TiP) and Jeffamine™ modified (JETiP), was investigated in composites derived from recycled polypropylene/polycaprolactone/titanium phosphate (PPr/PCL/TiP and PPr/PCL/JETiP). The TiP was synthesized and chemically modified with amine and the composite processed in a Haake rheometer. Improvement of PPr thermal stability was revealed. Reduction of PPr cooling crystallization temperature (9°C) and crystallinity degree (∼5–10%) were registered. Hydrogen nuclear magnetic resonance time domain revealed enhance of molecular mobility which was associated to the diminution of PPr crystallinity. The X-ray diffraction pattern of the composite PPr/PCL/JETiP did not show phosphate diffraction angle. It was understood as polymer intercalation into modified titanium phosphate galleries. At low temperature, the storage modulus increased by the presence of PCL and phosphates evidencing reinforcement. Both PPr/PCL/TiP and PPr/PCL/JETiP composites yielded phase separation systems revealed by two peaks in the loss modulus curves. Also, the high PPr participation effectiveness degree on the PCL-rich phase was understood as owing to the interaction between PCL and phosphates.

Dynamic Investigations of Polymeric Systems in Viscoelastic State with Polymer Concentration Above Critical

The dynamic deformation of polymeric systems (spinning solutions of polymers) with a polymer concentration above the critical value, characterized by an unstable deformation regime, was investigated. The unified theory of deformation of polymeric systems in a viscoelastic state, by means of which it is possible to undertake a rheological analysis of the viscoelastic characteristics of polymeric systems from two measurement points over a wide range of variation of velocity gradient, was used for the investigation. It was shown that the intersection of the classical loss modulus and elasticity modulus curves is due to transition of the polymeric system to an enforced elastic state with the appearance of an effect from negative complex viscosity and its negative elastic component. Good agreement is observed during comparison of the data of unified deformation theory and experimental data for the stable deformation region.

Viscoelastic analysis of oat grain within linear viscoelastic region by using dynamic mechanical analyzer

Abstract The stress relaxation, creep-recovery, temperature, and frequency sweep tests were performed within the linear viscoelastic region by using a dynamic mechanical analyzer to investigate the viscoelastic characteristic of oat grain. The result showed that 5-element Maxwell and Burgers model were able to describe viscoelastic behaviors better. The relaxation stress decreased with the increasing moisture content from 6.79 to 23.35%, while the creep strain increased as well as the final percentage recovery decreased from 58.61 to 32.50%. In frequency sweep, storage modulus increased with the increasing frequency. In temperature sweep, there was a clear turning point in storage modulus, loss modulus, and tan delta curves with increasing temperature. The turning value of 167.47, 147.44, 134.27, 132.41, 110.28, and 92.62 °C detected in the tan delta were regarded as the best glass transition temperatures. This temperature was found to be lower than gelatinization heating temperature and decrease with the increase of moisture content. The crystalline structure of oat exhibited a typical A-type pattern and corresponding crystallinity increased from 22.03 to 31.86% with increasing moisture content. The scanning electron microscopy (SEM) micrograph of oat section was found that the size and adhesive effect of starch granules increased due to hydration.

Effect of thermal cycling on mechanical and thermal properties of basalt fibre-reinforced epoxy composites

Current study investigated the effect of thermal fatigue on mechanical and thermal properties of basalt fibre-reinforced polymer (BFRP) composites. To this, basalt fibre textiles in 2/2 twill pattern was used to fabricate BFRP composites. Thermal cycling experiment was carried out between $$-40$$ and $$+120^{\circ }$$ C for 20, 40, 60, 80 and 120 cycles. Moreover, dynamic mechanical analyzer (DMA) was used to evaluate the effect of thermal cycling on thermal properties of BFRPs. Moreover, we compared the extracted viscoelastic characteristics, such as storage modulus, loss modulus and loss factor curves with original thermal-treated BFRP specimens. Based on the results, thermal cycling affected the characteristics of composites in the post-curing stage due to an increase in temperature. Finally, the effect of thermal cycling on water absorption properties of BFRP composites was examined by hydrophobicity test. The results showed that tensile strength, flexural modulus and ILSS values increased with the increase in the number of cycles up to 80 cycles. In other words, an increase in the number of cycles increased the hydrophobicity of BFRP composites by decreasing the contact angles. Finally, the mechanical properties of tested composites were significantly decreased when the number of cycles reached 120. This was due to the mismatch of thermal expansion coefficient and long crack formation in the structure of composite.

Preparation and properties of flame-retardant epoxy resins containing reactive phosphorus flame retardant

To prepare flame-retardant epoxy resin, phosphorus compound containing di-hydroxyl group (10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phospha phenanthrene-10-oxide, DOPO-HQ) was reacted with uncured epoxy resin (diglycidyl ether of bisphenol A, YD-128) and then cured using a curing agent (dicyandiamide, DICY). This study focused on the effect of phosphorus compound/phosphorus content on physical properties and flame retardancy of cured epoxy resin. The thermal decomposition temperature of the cured epoxy resins (samples: P0, P1.5, P2.0, and P2.5, the number represents the wt% of phosphorus) increased with increasing the content of phosphorus compound/phosphorus (0/0, 19.8/1.5, 27.8/2.0, and 36.8/2.5 wt%) based on epoxy resin. The impact strength of the cured epoxy resin increased significantly with increasing phosphorus compound content. As the phosphorus compound/phosphorus content increased from 0/0 to 36.8/2.5 wt%, the glass transition temperature (the peak temperature of loss modulus curve) increased from 135.2°C to 142.0°C. In addition, as the content of phosphorous compound increased, the storage modulus remained almost constant up to higher temperature. The limiting oxygen index value of cured epoxy resin increased from 21.1% to 30.0% with increasing phosphorus compound/phosphorus content from 0/0 to 36.8/2.5 wt%. The UL 94 V test result showed that no rating for phosphorus compounds less than 19.8 wt% and V-1 for 27.8 wt%. However, when the phosphorus compound was 36.8 wt%, the V-0 level indicating complete flame retardancy was obtained. In conclusion, the incorporation of phosphorus compounds into the epoxy chain resulted in improved properties such as impact strength and heat resistance, as well as a significant increase in flame retardancy.

Blends of rABS and SEBS: Influence of In-Situ Compatibilization on the Mechanical Properties.

In this study, the in-situ compatibilization reaction between recycled acrylonitrile–butadiene–styrene copolymer (rABS) and functional styrene–ethylene–butylene–styrene block maleic anhydride (SEBS-g-MAH) was confirmed, which contributed to the toughening phenomenon of rABS, especially the notched impact strength. As mechanical test that manifested, the rABS/SEBS-g-MAH blends are stronger and more ductile than the rABS/SEBS blends. Prominently, the former has great advantage over the latter in terms of improving the impact performance. Scanning electron microscope (SEM) images showed that the compatible segments that were generated by reaction not only improve the interface adhesion of rABS/SEBS-g-MAH blends but also promote the evolution of co-continuous structures, which can be evidently observed after etching. Furthermore, the SEM micrographs of tensile fracture surfaces indicated that the formation of the co-continuous phase and the improvement of interface adhesion are the most profound reasons for the excellent tensile properties of the rABS/SEBS-g-MAH blends. The impact fracture surface revealed that two-phase interface affects crack propagation and shear yielding absorbs more impact energy than simple interface debonding does at higher deformation rates. Meanwhile, rheological analysis demonstrated that the complex viscosity of the rABS/SEBS-g-MAH (80/20 wt%) blend with a co-continuous structure exhibits a maximum positive deviation at low frequencies from the theoretical value calculated using the rule of logarithmic sum, which indicated a connection between co-continuous structure and complex viscosity. In addition, the storage modulus vs. loss modulus curves of the blends revealed that the viscoelastic behavior of rABS/SEBS-g-MAH blends is very similar to that of rABS.

An investigation on curing rheokinetics of a nadic end-capped MDA-BTDA-ODA copolyimide resin by dynamic mechanical analysis

Abstract The curing behavior of a nadic end capped MDA-BTDA-ODA copolyimide resin was investigated using dynamic mechanical analysis in the shear mode. The studied copolyimide consists of 3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride (BTDA) with a 50:50 M combination of 4,4′-diaminodiphenylmethane (MDA) and 3,4′-oxydianiline (ODA) monomers. The effects of curing temperature and time on the rheological properties of the resin were examined. At the beginning of the network formation process, an increase in the storage modulus, loss modulus and complex viscosity was observed. The gelation temperature, Tgel, was determined from the intersection points of the temperature-dependent storage and loss moduli curves. It was found that the rate of gelation of the resin was increased with increasing temperature. In terms of mechanical curing condition, the kinetics of isothermal network formation process at different isothermal curing temperatures were monitored by using Kamal-Sourour model. The model fitted well with experimental data. Therefore, mechanical conversion at different temperatures can be well predicted by the kinetics data.

Rheological analysis of thermo-responsive alginate/PNIPAAm graft copolymers synthesized by gamma radiation

Focused on biomedical applications of thermo-responsive polymers, low-doses of gamma radiation from a 60Co source were applied in a simple one-pot method to synthesize graft copolymers of alginate and poly(N-isopropylacrylamide) (PNIPAAm) with different compositions. The molar percentage of grafted NIPAAm (% molar NIPAAm) was determined by thermogravimetric analysis (TGA) and elemental analysis (EA), being the copolymer structure-property relationship studied in terms of thermo-associative and rheological behavior in aqueous solutions.The addition of more NIPAAm monomer in the initial mixture of reaction, as well as, increasing absorbed dose lead to a greater grafting. However, increasing radiation dose produces copolymers with diminished viscoelastic properties caused by the alginate backbone scission.From rheological curves, two transition temperatures, Ta and Tgel, were determined as a consequence of the thermo-responsiveness of PNIPAAm side chain. Storage (G′) and loss (G″) modulus curves undergo a slope inversion at Ta temperature, where both moduli begin to increase caused by an associative behavior of PNIPAAm domains. While, Tgel temperature is related to the onset of the gelation process at the G′/G″ crossover.In order to design samples with liquid-gel transitions close to the human body, able to form gels in situ once inoculated, it was possible to tailor both transition temperatures selecting copolymers with an appropriate PNIPAAm content and optimizing the copolymer concentration in the aqueous solution. A good agreement between transition temperatures and viscoelastic properties was achieved for 5 wt% aqueous solutions of copolymers with low NIPAAm content synthesized at the lowest absorbed dose (0.5 kGy).