Isothermal transitions of a thermosetting system

A study of the curing reactions of a cycloaliphatic epoxy resin/anhydride system by torsional braid analysis showed the existence of two critical isothermal temperatures. These are T_g∞ (the maximum glass transition temperature of the thermoset system) and T_gg (the glass transition temperature of the material at its gel point). Two rheologically active kinetic transitions occur during isothermal cure which correspond to gelation and vitrification. Three types of isothermal behavior occur: if T_cure > T_g∞, only gelation is observed; if T_g∞ > T_cure > T_gg, both gelation and vitrification are observed; if T_cure < T_gg, only vitrification is observed. T_gg corresponds to the isothermal cure temperature at which gelation and vitrification occur simultaneously. Methods for determining the time to gel and the time to vitrify, and also T_g∞ and T_gg, have been developed. The time to gel obeyed the Arrhenius relationship, whereas the time to vitrify passed through a minimum. Application of these results to thermosetting systems in general is discussed in terms of the influence of molecular structure on the values of T_g∞ and T_gg.     

Epoxy thermosetting systems: Dynamic mechanical analysis of the reactions of aromatic diamines with the diglycidyl ether of bisphenol A

Dynamic mechanical behavior during the reactions of four aromatic diamines (m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfone, and benzidine) with the diglycidyl ether of bisphenol A was studied by torsional braid analysis under isothermal conditions. Depending on the cure temperature, three types of behavior were observed: (I) below T_gg (the glass transition temperature of the reactive systems at the gel point); (II) between T_gg and T_g∞ (the glass transition temperature of the ultimately cured polymers); (III) above T_g∞. Overall activation energies and apparent overall rate constants of the cure reactions based on third-order overall kinetics were determined before gelation, after gelation but before vitrification, and after vitrification, using gelation time, relative rigidity, and glass transition temperature T_g(t) of the polymers as kinetic terms. The influence of cure temperature and structure of the diamines on the kinetic parameters is discussed.     

Rheological study on thermal-induced gelation behavior of polyacrylonitrile solution

Thermal-induced gelation process of different polyacrylonitrile (PAN) solutions was investigated through dynamic rheological measurements. The rheological material parameters characterizing the gelation behavior of the PAN solutions were measured and the effects of such factors as water content, solvent type and concentration on the gelation process were analyzed. It is found that the gel point T _gel of PAN/DMSO (dimethyl sulfoxide)–water solution increases with increased water content in the solution. Also, T _gel becomes higher when the solvent has a lower solvency for PAN. A linear relationship between logG′ and logω, logG″ and logω indicates the beginning of gelation. The PAN concentration of the solution affects T _gel in a way similar to that of the water content. The relaxation exponent n is found to relate to the fractal dimension of the polymer gel. For PAN/DMSO–water solution, this exponent n remains almost constant when the water content differs. The solvent type and concentration respectively influences n value in their own way. The PAN/DMSO–water solution systems in our work exhibit similar characteristics of gel structure, concluded from the n and d _f values of these systems. A logarithmic plot between G′ and G″ can be used to evaluate the structural evolution of the solution, and a comparatively steep slope of the curve is an indication of gelation.     

Rheological behavior of reactive miscible polymer blends: Influence of mixing and annealing before crosslinking

We followed crosslinking reactions in the blends of two miscible reactive polymers by either torque rheometry or dynamic rheological measurements. Functional polymers with controlled glass‐transition temperatures (T_g's), chain lengths, and number of reactive groups per chain were synthesized by bulk radical polymerization. The blends were prepared either in a batch mixer or directly in the parallel plate geometry of a dynamic rheometer. Because of the low T_g of the blend components, it was possible to separate the mixing step from the crosslinking reaction, which was followed by small amplitude dynamic measurements at a higher temperature. The kinetics of the crosslinking reaction were determined by the study of the variations of the storage modulus (G′) as a function of the reaction time. In this study, we focused on investigating the influence of blend composition, crosslinking reaction temperature, and amount of shear generated during the mixing step on the reaction kinetics. The influence of annealing time after the preshear step was also investigated. We found that the mixing procedure in the internal mixer produced homogeneous blends for which G′ was dependent on the reaction time. Moreover, the reaction rate increased as the temperature and the chain functionality increased. A first approach showed that reduced variables could be defined from G′ and reaction time with the initial concentration of the functional units to obtain a master curve independent of the species concentration. For blends prepared directly between the parallel plates of the dynamic rheometer, G′ and the subsequent reaction rate were strongly dependent on the amount of shear generated during the mixing step. However, at high enough shear, the blend was perfectly mixed and the increase in G′ versus reaction time was comparable to that obtained for the blend prepared in the internal mixer. Surprisingly, the higher the annealing time was, the lower the increase in G′ was. However, we could explained this by considering the fact that the reaction started during the annealing step, which therefore, led to a thin crosslinked layer, which prevented any further diffusion of the polymer chains. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1978–1995, 2005     

Pultruded fiber reinforced blocked polyurethane (PU) composites. II. Processing variables and dynamic mechanical properties

Unidirectional fiber reinforced blocked polyurethane (PU) composites have been prepared by the pultrusion process. The effects of processing variables on the mechanical properties and dynamic mechanical properties of fiber reinforced PU composites by pultrusion have been studied. The processing variables investigated included pulling rate (in-line speed), die temperature, postcure time and temperature, and filler type and content. The dynamic mechanical properties of the composites produced by the process were studied utilizing dynamic mechanical spectrometer. Results show that the composites possessed various optimum pulling rates at different die temperatures. From the DSC data analysis, swelling ratio, and mechanical properties, the optimum die temperature was determined. It was found that the mechanical properties increase with filler content for various types of filler. The increasing of mechanical properties depends on the optimum postcure temperature and time. However, the properties decreased for longer postcure times since the composite materials were degraded. The glass-transition temperature (T_g) increased slightly and the damping peak (tan δ) was broadened due to fiber reinforcement. The dynamic mechanical moduli (G′, G″) of pultruded PU composites are apparently higher than those of the matrices. The moduli (G′, G″) increase with increasing fiber and filler content, and the damping peak becomes broad. Effect of postcuring on the degree of crosslinking, T_g, and dynamic modulus will be discussed.     

Time–temperature–transformation (TTT) cure diagram: Modeling the cure behavior of thermosets

The times to gelation and to vitrification for the isothermal cure of an amine-cured epoxy (Epon 828/PACM-20) have been measured on macroscopic and molecular levels by dynamic mechanical spectrometry (torsional braid analysis and Rheometrics dynamic spectrometer), infrared spectroscopy, and gel fraction experiments. The relationships between the extents of conversion at gelation and at vitrification and the isothermal cure temperature form the basis of a theoretical model of the time–temperature–transformation (TTT) cure diagram, in which the times to gelation and to vitrification during isothermal cure versus temperature are predicted. The model demonstrates that the “S” shape of the vitrification curve depends on the reaction kinetics, as well as on the physical parameters of the system, i.e., the glass transition temperatures of the uncured resin (T_g0), the fully cured resin (T_g∞), and the gel (_gelT_g). The bulk viscosity of a reactive system prior to gelation and/or vitrification is also described.     

Viscoelastic properties of elastic polyurethaneureas in the curing process

Dynamic viscoelastic properties of a system, NCO-terminated polyurethane–aniline–cresol–formaldehyde liquid resin were studied during the curing process using an R-17 Weissenberg Rheogoniometer. For gel time determinations a new method was developed, the gel time being then difined as the cure time when the relaxation time τ = 3 s at a frequency of 0.1 Hz was achieved. The dynamic storage modulus G′, the dynamic viscosity η´ and the relaxation time τ have been determined as functions of curing time. The effects of cure temperature and of curing agent concentration on G′, η′, and τ were studied. The influence of cure temperature on the gel time and on the visco-elastic properties determined at 18ks (5 h) of curing was discussed. Based on the experimental results, it was concluded that curing at higher temperature led to the more crosslinked polymer. Activation energy values for the gel time were also determined and compared with the values for polyurethanes and polyurethaneureas reported elsewhere. A relationship between the relaxation time and the effect of frequency on modulus G′ was presented, and it appeared to be independent of cure temperature, curing agent concentration, and curing time, being then presumably a useful method for comparative studies of viscoelastic behavior of different materials in curing process. This relationship was compared with the approximate relationship between tan δ and d In G′/d In ω given by Staverman and Schwarzl. The agreement at shorter relaxation times and some discrepancy at longer times were obtained.     

Kinetics of sol-to-gel transition for poloxamer polyols

Kinetics of gelation for aqueous solutions of poloxamers 407 and 288 were determined using pulse shearometry. The principle of this method for determining the shear modulus of a semisolid was based on generation of a torsional force that is transmitted through the poloxamer sample at discrete time intervals. Three distinct linear phases were observed for the log dynamic shear modulus (G′) vs. time profiles as poloxamer 407 and 288 solutions of varying concentrations were allowed to passively warm at room temperature to a temperature exceeding the sol-to-gel transition temperature, T_m. The beginning of the second exponential phase coincided with the onset of the gelation process as determined by visual observation. Although gelation appeared visually to be complete at the beginning of the third exponential phase of the log G′ vs. time profiles, this last exponential phase may indicate the rate of formation of the polymer network. A comparison of poloxamer 407 [30% (w/w); T_m = 10.9°C] and poloxamer 288 [37% (w/w); T_m = 11.1°C] would suggest that the concentration of poloxamer required to achieve approximately the same gelation temperature for poloxamers having a similar ratio of poly(oxypropylene):poly(oxyethylene) units decreases with increasing molecular weight of the poly(oxypropylene) hydrophobe contained in the copolymer. Results of these preliminary studies suggest that the gelation process was significantly (p < .05) more rapid for poloxamer 407 at a 30% (w/w) concentration compared to a 30% (w/w) solution of poloxamer 288 when the poloxamer solutions were allowed to passively warm at room temperature. In addition, it appears that the rate of gelation for the poloxamer solutions studied was dependent on the rate of heat transfer through the polymer solution.     

Viscoelastic relaxation of styrene–butadiene–styrene block copolymers with different topological structures

The viscoelastic relaxation of linear styrene–butadiene–styrene triblock copolymer (l‐SBS) and star styrene–butadiene–styrene triblock copolymer (s‐SBS) with four arms were investigated with differential scanning calorimetry and dynamic rheological measurements. Three characteristic viscoelastic responses of l‐SBS and s‐SBS in the plot of the loss tangent (tan δ) and temperature at different frequencies (ω's), which corresponded to the relaxation of the polybutadiene (PB) block (peak I), the glass transition of the polystyrene (PS) phase (peak II), and the mutual diffusion between the PB blocks and PS blocks (peak III), respectively, were observed in the experimental range. Although ω was 0.1 rad/s, a noticeable peak III was gained for both l‐SBS and s‐SBS. The dynamic storage modulus (G′) of l‐SBS showed two distinct types of behavior, depending on the temperature. At temperature (T) < T₂ (where T₂ is the temperature corresponding to peak II), G′ of l‐SBS displayed a very weak ω dependency. In contrast, at T > T₂, G′ decayed much more rapidly. However, G′ of s‐SBS displayed a very weak ω dependency at both T < T₂ and T > T₂. Only near T₂ did s‐SBS decay with ω a little sharply. These indicated, in contrast to l‐SBS, that s‐SBS still exhibited more elasticity even at T > T₂ because of its crosslinking point between the PB blocks (the star structure). In the lower ω range, l‐SBS exhibited a stronger peak III than s‐SBS despite the same styrene content for l‐SBS and s‐SBS. The high tan δ value of peak III for l‐SBS was considered to be related to the internal friction among the PB blocks or the whole l‐SBS chain, not the PS blocks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characterization of polymer-coated optical fibers using a torsion pendulum

A freely oscillating torsion pendulum has been used to characterize the dynamic mechanical behavior of single polymer-coated optical fibers. The dynamical mechanical spectra of the polymer coatings exhibit a glass transition temperature (T_g), a cryogenic glassy-state relaxation (T_sec), and another cryogenic relaxation that is attributed to water present in the coating (TH₂O). The shear modulus (G′) of the coating was computed from the shear moduli of the composite specimen and the core, assuming that the coating and core deform through the same angle on oscillation. The glassy-state modulus was the same for both thin and thick coatings, although the intensity of the damping peaks, as measured by the logarithmic decrement, increased with coating thickness. Comparison of the dynamic mechanical behavior of a coated optical fiber and of a free film cast from the same reactive components shows that the polymer itself can absorb water at ambient conditions and display a mechanical relaxation at cryogenic temperatures. The T., H₂O and T_sec relaxations are coupled with respect to their intensities. Latent chemical reactivity was found in one coating above its maximum temperature of cure. In this, the temperature of cure determines the glass transition temperature.     

Shear modulus in closely packed gel suspensions

Rheological properties and swelling were examined in a series of concentrations of particles of crosslinked polyacrylate gels in water or salt solutions. The modulus during steady shear G_s = 2τ²/P₁₁-P₂₂ was determined from shear stress τ and primary normal force difference P₁₁-P₂₂ in a cone-and-plate rheometer. G_s was nearly constant with shear rate for the gel particles in the closely packed condition. The dynamic storage modulus G′ determined by ecentric rotating disc rheometry increased with increasing frequency for all concentrations. The apparent equilibrium shear modulus G_e determined by stress relaxation agreed closely at all concentrations and ionic strengths with the corresponding values of G_s, and hence G_s is considered a good estimate of equilibrium shear modulus for this gel material.     

Thermal-induced simultaneous liquid-liquid phase separation and liquid-solid transition in aqueous polyurethane dispersions

Thermal-induced simultaneous phase separation and liquid-solid transition (gelation) in waterborne polyurethane dispersions has been detected morphologically and rheologically. The viscoelastic material functions, such as dynamic shear moduli, G′ and G″ complex shear viscosity, η* and loss tangent, tan δ were found to be very sensitive to the structure evolution during the gelation process and the subsequent formation of a fractal polymer gel. At the onset temperature of the gelation process, an abrupt increase in G′, G″ and η* (several orders of magnitude) was observed during the dynamic temperature ramps (2 °C/min heating-rate) over a wide range of angular frequency. The temperature dependencies of G′, G″ and tan δ were found to be frequency independent at the gel-point, T_gel, providing a fingerprint for determining T_gel of the dispersions. Furthermore, a dramatic increase in zero-shear viscosity, η₀ (v-shape) was observed at T=T_gel and found to be in good agreement with the value obtained from the tan δ versus T data. As expected, the time-temperature-superposition principle was found to be only valid for temperatures lower than the T_gel; the principle failed at T≥70 °C. The morphology of the dispersions at 70 °C for 2 h showed for 36, 38 and 40 wt% formation of a network structure having a unique periodicity and phase connectivity. A lower critical solution temperature (LCST) phase diagram was estimated based on the different morphologies of the dispersions. The coexistence of liquid-liquid and liquid-solid transitions at the same temperature range confirmed the complex behavior of the polyurethane dispersions, pointing to the need for a new theory that explicitly takes this special behavior into account.     

Viscoelastic Behavior,Thermodynamic Compatibility,and Phase Equilibria in Block Copolymer-Based Pressure-Sensitive Adhesives

The viscoelastic behavior, thermodynamic compatibility, and phase equilibria in block copolymer-based pressure-sensitive adhesives were investigated. The block copolymers investigated were: (1) polystyrene-block-polybutadiene-block-polystyrene (SBS) copolymer (KRATON® D-1102, Shell Development Company) and (2) polystyrene-block-polyisoprene-block-polystyrene (SIS) copolymer (KRATON® D-1107, Shell Development Company). The tackifying resins investigated were: (1) WINGTACK® 86 (Goodyear Tire & Rubber Company) and (2) PICCOTAC® 95BHT (Hercules Inc.). Samples of various compositions were prepared by a solution-casting method with toluene as solvent. Measurements of dynamic storage modulus (G″), dynamic loss modulus (G″), and loss tangent (tan δ) were taken, using a Rheometrics Mechanical Spectrometer. It was found that: (1) both WINGTACK 86 and PICCOTAC 95BHT were equally effective in decreasing the plateau modulus (G ^O _N ), and increasing the glass transition temperature (T_g ) of the polyisoprene midblock of KRATON 1107; and (2) WINGTACK 86 was very effective in decreasing the G ^O _N and increasing the T_g of the polybutadiene midblock of KRATON 1102, whereas PICCOTAC 95BHT was not. The observed difference between WINGTACK 86 and PICCOTAC 95BHT in decreasing the G ^O _N and increasing the T_g of the polybutadiene midblock of KRATON 1102, whereas PICCOTAC 95BHT was not. The observed difference between WINGTACK 86 and PICCOTAC 95BHT in decreasing the G ^O _N and increasing the T_g of the polybutadiene midblock of KRATON 1102 (perhaps to SBS block copolymers in general) is explained by the values of the interaction parameter for WINGTACK 86 and KRATON 1102, and for PICCOTAC 95BHT and KRATON 1102. The interaction parameter was determined, using the piezoelectric quartz sorption method. Phase diagrams were constructed for the four block copolymer/tackifying resin systems investigated, using information obtained from both dynamic viscoelastic measurements and optical microscopy. It was found that when mixed with KRATON 1102, PICCOTAC 95BHT formed separate domains whereas WINGTACK 86 did not over the range of concentrations and temperatures investigated. This confirms the evidence obtained from two other independent experimental techniques, namely, dynamic viscoelastic measurements and the piezo-electric sorption method. We have concluded from the present study that PICCOTAC 95BHT is not as an effective tackifying resin as WINGTACK 86, when each is mixed with KRATON 1102. It is pointed out further that information on the order-disorder transition temperature T_r , which was determined from a rheological technique proposed by us, is valuable in determining optimal processing conditions for block copolymer-based pressure-sensitive adhesives.     

Effect of physical annealing on the dynamic mechanical properties of a high-Tg amine-cured epoxy system

Physical annealing of a fully cured amine/epoxy system has been investigated using the freely oscillating TBA torsion pendulum technique. The material densifies spontaneously during annealing in an attempt to reach equilibrium, thereby changing material behavior. The dynamic mechanical behavior of a film specimen (T_g = 174°C, 0.3 Hz) and of a glass braid composite specimen (T_g = 182°C, 0.9 Hz) was monitored during isothermal annealing at sub-T_g temperatures (ranging to 230°C below T_g); after annealing, the behavior was measured vs. temperature and compared with that of the unannealed state. Isothermally, the storage modulus (G′) of the film specimen and the relative rigidity (1/P²) of the composite specimen increased almost linearly with log time, whereas the logarithmic decrement (Δ) decreased with time. The isothermal rates of annealing were determined from the rates of changes in G′ and in 1/P² for the film and composite specimens, respectively. In a wide temperature range between T_g and the secondary transition temperature, T_sec (≈ ?30°C, 2.3 Hz by TBA), the isothermal rates of annealing at the same annealing time appeared to be the same. Thermomechanical spectra of the isothermally annealed material revealed a maximum deviation in thermomechanical behavior from the unannealed material in the vicinity of the annealing temperature. The effects of physical aging were the same for the film and composite specimens. Effects of sequential annealing at two isothermal temperatures on the thermomechanical behavior were also investigated; when the second temperature was higher than the first, the effect of only the high-temperature annealing was evident, whereas the effect of annealing at both temperatures was revealed when the second temperature was lower than the first. Results suggest that physical annealing at different temperatures involves different length scales of chain segment relaxation and that the effects of isothermal aging can be eliminated by heating to below T_g.     

Relation between impact strength and dynamic mechanical properties of plastics

A simple theory is developed which correlates the Izod impact strength of polymers with (G′₁₀₀-G′₃₀₀)²/G′₁₀₀, where G′₁₀₀ and G′₃₀₀ are dynamic shear moduli at 100°K. and 300°K., respectively. The theory assumes the Maxwell element for the material and the fracture time smaller than the relaxation time. The theory is verified by experimental data for numerous polymers. Another approach which correlates the impact strength with the integrated loss factor from 0 to 300°K. is also proved valid.     

Viscoelastic properties of alkyd ceramers

The viscoelastic behavior of three alkyd ceramers was studied using dynamic mechanical thermal analysis (DMTA). A commercial product was compared to model alkyds. The model alkyds were prepared from phthalic anhydride, glycerol, and linseed or sunflower seed oil. Three sol–gel precursors, titanium tetra-i-propoxide, titanium di-i-propoxide diacetylacetonate, and zirconium tera-n-propoxide were investigated. The alkyd ceramers were evaluated as a function of both alkyd type and a sol–gel precursor content. The viscoelastic data showed that both E′ and T_g were affected by sol–gel precursor content. Both the crosslink density and T_g demonstrated a minimum at low sol–gel precursor contents. After this minimum, both the crosslink density and the T_g increased substantially. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2017–2028, 1999     

A new approach for determination of gel time of a glass/epoxy prepreg

Gel time of a glass/epoxy prepreg, HexPly®1454, was investigated by a parallel plate rheometer. The prepreg is based on dicyandiamide (DICY)‐cured diglycidyl ether of bisphenol A epoxy resin system. It is found that the application of the G′‐G″ crossover method for gel time determination is not suitable for this system. A new approach was proposed in which the maximum tan δ is regarded as the gel point. This can accurately define the gel point at various temperatures. The results proved that this point is independent of the applied frequency. The activation energy for the cure reaction of the system was determined via gel time determination of the prepreg at different isothermal temperatures and found to be 75.0 ± 10.2 kJ/mol. This is in good agreement with the activation energy obtained from the dynamic DSC studies. The steady‐shear rheology experiment was used to study the viscosity profile and subsequently to determine the gel point and verify the new approach for gel time determination. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Swelling and mechanical properties of cellulose hydrogels. III. Temperature effects on the swelling and compliance levels studied by dilatometry and 1H-NMR spectroscopy

The temperature dependence of the swelling and the creep compliance has been investigated for swollen isotropic cellulose hydrogels. The measurements were performed in a high precision type of dilatometer between 5 and 65°C. The thermal expansion of the gels in silicone oil (closed system) and the temperature dependence of the equilibrium swelling in water (open system) were studied. The influence of compressive stress in these experiments was also evaluated. The swelling level in equilibrium with water diminishes slightly with increasing temperature due to migration of water from the gel phase to the surrounding water phase. A secondary transition was found at 35°C where the temperature dependence of the swelling level is changed. When measured at constant gel composition the creep compliance of a highly swollen gel decreases with increasing temperature. The decrease is not, however, large enough for entropy elasticity to dominate over energetic elasticity. The energetic contribution f_U/f was determined to be 0.61 for a gel swollen to 3.9 g water/g dry gel (g/g) and 1.24 for a gel swollen to 1.05 g/g. The swelling and compliance data have also been analyzed in terms of a model where the gels are assumed to behave as a filler-reinforced rubbery network. The amorphous parts of the hydrogels are thus assumed to be described by the statistical theory for polymeric networks. In proton magnetic resonance studies of a gel swollen to 4.4 g/g the spin-lattice relaxation time T₁ was determined to be considerably longer than the spin-spin relaxation time T₂. T₂ has a maximum at 30°C. This maximum marks the onset (on the NMR time scale) of an exchange process between two types of proton species. These species are suggested to be specific hydration water and free gel water, respectively.     

Dynamic mechanical behavior of copolymers containing carbon black

The storage and loss moduli of random copolymers of styrene and butyl methacrylate containing carbon black of varied surface area were determined by dynamic mechanical analysis at several temperatures about 100°C above the glass-transition temperature, T_g. At low frequencies, the pure polymers exhibit linear double log plots of moduli against frequency, with slopes of unity and approaching two for G″ and G′, respectively. With the addition of carbon black filler, both G′ and G″ become independent of frequency and temperature at low frequencies, consistent with yield behavior arid the formation of a carbon black network. The limiting dynamic complex modulus exceeds the yield stress from steady shear rheology, perhaps indicating the extent of the carbon black network, which was highest for low-molecular-weight copolymer and polystyrene. The filled random copolymers behaved Theologically like similarly filled polystyrenes of comparable molecular weights. Plasticization effects observed in the steady shear rheology of filled copolymers containing small concentrations of carbon black were not observed in dynamic mechanical analysis, although dynamic moduli converge at high frequency.     

A rheological method for the study of crosslinking of ethylene acetate and ethylene acrylic ester copolymer in a polypropylene matrix

Transesterification may be used to crosslink a copolymer such as ethylene vinyl acetate with poly(ethylene acrylate-co-propylene) in the presence of dibutyltin oxide as a catalyst. A rheological study of the mechanism of this exchange reaction has been made: The kinetics of the crosslinking reaction was determined by studying the time and temperature dependence of the dynamic storage modulus G′(t, T)_ω. Kinetic curves obtained for different reactive blends (EVA, PP/EVA, and PPf/EVA) allowed for the evaluation of the activation energy of the reaction and, thus, specified the appropriate parameters (temperature and time) for carrying out this reaction in a molten state.