Viscoelastic Regime Research Articles

Effect of Filler Functionalization on the Thermo-Mechanical behavior of Polypropylene Nanocomposites

Present study is an experimental attempt to characterize the thermo-mechanical behavior of Thermoplastic polymer nanocomposites (PNC) surface functionalized with multi walled carbon nanotubes (MWCNT). Nanocomposites with two grades of MWCNT, pristine and –COOH functionalized were fabricated with isotactic polypropylene (iPP) and results were compared. Nanocomposites Films with 0%, 0.5%, 1% and 2% MWCNT loadings were prepared by conventional solution casting method followed by isothermal quasi static uniaxial tensile tests at constant strain rates of 0.1/min, cyclic tensile tests at strain rate of 0.1/min and isochronous creep characterization at stress levels of 0.2, 0.5, 1, 2, 5, 7, 10, 12 and 15 MPa performed on Tinius-Olsen Universal Testing machine to monitor strength and stiffness of the material and obtain the threshold of stress and time at room temperature to observe the transition from linear to nonlinear viscoelastic regime. Dynamic characterization at constant frequency of 1 Hz, temperature ramp 0-100°C, was performed to obtain storage modulus under dynamic loading conditions on Dynamic mechanical analyzer (DMA). It was reported that incorporation of functionalized MWCNT increases the strength, failure strain, reduces creep strain and increases stiffness of nanocomposites as compared to those with pristine-MWCNT up to 1% concentration. Moreover, it was also observed that loading under 1MPa and 5 seconds, the material behaves linearly. Prior to the testing, thermal stability of materials was monitored by Thermo-gravimetric analysis.

Hyperelastic behavior and dynamic mechanical relaxation in carbon black‐polymer composites

Tensile and thermo‐mechanical properties of nano‐composites fabricated by mechanically mixing semi‐crystalline ethylene‐co‐butyl acrylate (EBA) and carbon black (CB) nanoparticles are investigated. Stress–strain curves performed on samples over a broad range of CB content evidence the hyperelastic behavior of the EBA matrix. Neo‐Hookean and Mooney‐Rivlin models are used to fit the observed linear and nonlinear mechanical behaviors, respectively. The thermo‐mechanical curves highlight two relaxation phenomena depending on the CB content. Correspondingly, the EBA/CB interface properties are analyzed by correlating the volume fraction of the constrained polymer to the relaxation behavior of the viscoelastic linear regime. POLYM. COMPOS., 40:3005–3011, 2019. © 2018 Society of Plastics Engineers

Nonlinear Elongational Rheology of Unentangled Polystyrene and Poly(p-tert-butylstyrene) Melts

Nonlinear rheological behavior under uniaxial elongation was examined for unentangled melts of polystyrene (PS27; molecular weight M = 27k) and poly(p-tert-butylstyrene) (PtBS53; M = 53k) having nearly the same number of Kuhn segments per chain (nK = 30 and 35 for PS27 and PtBS53, respectively). For both materials, the steady state elongational viscosity, ηE, exhibited strain-rate-hardening and then strain-rate-softening on an increase of the Weissenberg number Wi ≥ 0.3 (Wi = eτ1eq, with τ1eq and e being the longest relaxation time in the linear viscoelastic regime and the Hencky strain rate, respectively). For the unentangled melts, the hardening and softening were free from any entanglement nonlinearity, so that the hardening was unequivocally related to the finite extensible nonlinear elasticity (FENE) of the chain, and the softening, to the suppression of the FENE effect due to reduction of the segment friction ζ occurring for the highly stretched and oriented chain. Thus, the ζ reduction, speculati...

Influence of the viscoelastic regime onto the UV reactivity of poly(lactic acid)

The photochemical reactivity of poly(lactic acid) in the rubbery and molten state was determined by two methods: photoRheology and photoDSC. Significant changes in rheological behaviour of PLA were observed, depending on the viscoelastic regime. In the rubbery state, cold crystallization causes difficulties in oxygen diffusion resulting mainly in crosslinking reactions. In the molten state, the competition between crosslinking and degradation was observed due to hydroperoxides decomposition. In all cases UV irradiation intensifies the reactions. Using PhotoDSC we determined the effect of hydroperoxides on the PLA degradation process, and the difference in effectiveness of temperature and UV on hydroperoxides decomposition.

Fourier-transform rheology of unvulcanized styrene butadiene rubber filled with increasingly silanized silica

ABSTRACTSilica as one the most important fillers for rubber material is routinely modified by silane to improve its compatibility with the rubber matrix. Silanization of the silica particle affects both the linear and nonlinear rheological behaviors of the compounds. Their rheological nonlinearity, however, is mostly analyzed in an indirect way from linear rheological parameters, e.g. G′(ω1, γ0) and G″(ω1, γ0), which lose their physical meaning in the nonlinear viscoelastic regime. In the present work, the nonlinearity is directly quantified by the Fourier-transform rheology (FT-Rheology) technique in terms of I3/1(ω1, γ0), the third relative higher harmonic, for unvulcanized styrene butadiene rubber compounds filled with a fixed amount of silica, but varying dosages of silane. With the proposed model for I3/1(γ0), the contributions toward nonlinearity from the filler networks at a low strain amplitude and the one from the polymer networks at high strain amplitude can be successfully separated for filled systems. The utmost nonlinearity contribution from the filler networks decreases with the silane content, which is assigned to the weakening interparticle interaction of the filler. With increasing silanization of silica, the utmost nonlinearity contribution from the polymer networks is found to increase. This nonlinear mechanical response is attributed to the enhanced interfacial interaction between the filler and polymer.

Nonlinear viscoelasticity of a dilute suspension of Brownian spheroids in oscillatory shear flow

The nonlinear viscoelasticity of a dilute suspension of Brownian spheroids subject to an oscillatory shear deformation is calculated numerically. This is achieved by determining the suspension microstructure, parameterized via the orientation distribution function. Specifically, the long-time periodic orientation distribution function is obtained via a numerical solution to the Fokker–Planck equation by combining a finite-difference approximation in space with a Fourier series in time. From an ensemble average of the particle stresslet, weighted by the orientation distribution function, the entire stress tensor and relevant birefringence parameters, namely, the average orientation angle and linear dichroism, are calculated; this is done over a range of the Weissenberg number (Wi) and the Deborah number (De), or dimensionless strain-rate amplitude and oscillation frequency, respectively. Detailed calculations are presented for prolate spheroids of aspect ratio r=20; however, our methodology is general and can be applied to spheroids of arbitrary aspect ratio. We provide results in four viscoelastic regimes: linear viscoelastic (Wi≪1), quasilinear viscoelastic (Wi>1 and Wi/De≪1), quasisteady viscoelastic (De→0), and finally, the nonlinear viscoelastic regime (Wi ≳ 1 and Wi/De ≳ 1), which is our main emphasis. In this last regime, where the nonlinear and unsteady viscoelasticity of the material is probed, multiple overshoots are observed in the shear stress and first normal stress difference. The mechanistic origin of these overshoots can be understood from the periodic orientation dynamics (i.e., Jeffery orbits) of a particle under steady shear in the absence of Brownian rotation (Wi→∞). This is achieved by simultaneously analyzing the microstructure, shear stress, first normal stress difference, and birefringence parameters specifically at Wi=20 and De=1. For these values of Wi,De, and r, the period of a Jeffery orbit is comparable to the period of an oscillation cycle, allowing sufficient time for a single Jeffery orbit (and subsequent overshoot) to occur during an oscillation cycle. We contrast this behavior to recent work by Khair [J. Fluid. Mech. 791, R5 (2016)] on nearly spherical particles, for which many more overshoots are observed during an oscillation cycle, due to the shorter period of the Jeffery orbit. We briefly provide results for oblate spheroids of aspect ratio r=0.05 and compare to the results for r=20. Finally, we comment on the relevance of the present micro-mechanical analysis to the nonlinear viscoelasticity of other complex fluid materials.

Chain Retraction in Highly Entangled Stretched Polymer Melts.

We use computer simulations to study the relaxation of strongly deformed highly entangled polymer melts in the nonlinear viscoelastic regime, focusing on anisotropic chain conformations after isochoric elongation. The Doi-Edwards tube model and its Graham-Likhtman-McLeish-Milner (GLaMM) extension, incorporating contour length fluctuation and convective constraint release, predict a retraction of the polymer chain extension in all directions, setting in immediately after deformation. This prediction has been challenged by experiment, simulation, and other theoretical studies, questioning the general validity of the tube concept. For very long chains we observe the initial contraction of the chain extension parallel and perpendicular to the stretching direction. However, the effect is significantly weaker than predicted by the GLaMM model. We also show that the first anisotropic term of an expansion of the 2D scattering function qualitatively agrees to predictions of the GLaMM model, providing an option for direct experimental tests.

Predictions for circular contraction-expansion flows with viscoelastoplastic & thixotropic fluids

In this predominately predictive modelling finite volume/element study, a comparative analysis is performed for time-dependent and viscoelastoplastic flow in a circular contraction-expansion geometry of aspect-ratio 10:1:10. For this, a hybrid finite volume/element scheme is employed. A new and revised micellar model is investigated, under the denomination of BMP+_τp, which reflects a bounded extensional viscosity response and an N1Shear-upturn at large deformation rates (lost in earlier model-variants), a versatile model capable of supporting plasticity, shear-thinning, strain softening-hardening and shear-banding. Many of these features are common to wormlike micellar and polymer solutions. Then, findings are contrasted against a de Souza Mendes model. Two flow regimes are addressed: plastic flow (low flow-rate Q ≤ 1 units, solvent-fraction β < 10−1) and viscoelastic flow (larger-Q > 1; minimised plasticity; β = 1/9); as quantified via flow-structure, yield-fronts and pressure-drops. Under the plastic regime, elasticity-increase causes asymmetry about the contraction-plane, whilst yield-stress and enhanced strain-hardening promote solid-like features, apparent through augmented unyielded-regions and rising pressure-drops. Concerning the viscoelastic regime and vortex-structures, extensional-deformation experienced correlates with hardening expectation in uniaxial-extension, whilst streamline activity in vortex-cells correlates with normal-stress response in shear. Adjustment in strain-hardening/softening response with Q-rise, provides translation from weaker salient-corner vortex centres to stronger elastic corner-vortices; yet, when softening finally prevails, asymmetric upstream/downstream salient-corners vortex patterns are recovered. For strong-hardening and solvent-dominated β∼0.8 fluids (as with Boger fluids), an intermediate lip-vortex-formation phase is noted, alongside coexistence of salient-corner vortices. Such a vortex-coexistence phase is distinctly absent in solute-concentrated fluids.

Systematic bottom-up theory for the viscoelastic response of worm-like chain networks

Using the frequency-dependent force-extension response functions of single worm-like chains as the only input, the linear complex viscoelastic modulus of a polymeric network with given connectivity is derived from a systematic bottom-up theory via iterative coarse-graining. Choosing a cubic connectivity and accounting for random network orientation, we find excellent agreement with experimental data for actin networks under shear over the entire frequency range with the strength of the osmotic pressure that acts within the polymeric network as the only fitting parameter. In particular, we obtain a viscoelastic plateau regime at low frequencies and a crossover to an intermediate-frequency regime characterized by a power law behavior and an inhomogeneous shear deformation field.

Viscoelastic transitions exhibited by modified and unmodified bitumen

ABSTRACTThe working temperature of a bituminous pavement can typically range from 75C to C. Bitumen shows a wide spectrum of mechanical behaviour in this temperature range and these include those of a viscoelastic fluid, a viscoelastic solid and an elastic solid. Due to the amorphous nature of the material, the transitions between such mechanical responses are gradual. This investigation focuses on the transition between the viscoelastic solid and the viscoelastic fluid state of a wide class of bitumens with regard to unaged and short-term aged conditions. An unmodified binder and three modified binders were subjected to temperature sweep and frequency sweep in the viscoelastic regime across a wide range of temperatures. Depending on the material and the post-processing method followed, one could discern a viscoelastic fluid and a viscoelastic solid regime and a frequency-dependent mixture regime consisting of a viscoelastic solid and a viscoelastic fluid, across the tested temperatures and frequencies. It is shown in this investigation that parameters such as G–G crossover and frequency independence of tan δ cannot be used to estimate the temperatures corresponding to the onset of either fluid-like or solid-like behaviour of the body as the temperature varies. It is also shown that the time–temperature superposition principle does not hold good in the temperature regime tested (75–25C) due to the viscoelastic transitions exhibited by bitumen and modified bitumen.

Strain rate and temperature dependence of the mechanical properties of polymers: A universal time-temperature superposition principle.

Establishing the Time-Temperature and Frequency-Temperature Superposition Principles (TTSP and FTSP) to describe the mechanical behavior of polymeric materials is always of paramount significance. In this work, by adopting the classic coarse-grained model, we investigate the validity of these superposition principles for a series of networks, such as the pure polymer network, interpenetrating polymer networks composed of stiff and flexible networks (IPNs-SF), interpenetrating polymer networks composed of different cross-linking networks (IPNs-DC), polymer nanocomposites (PNCs), and surface grafted modified PNCs. The study focuses on the three critical mechanical properties such as the stress relaxation, the storage modulus versus the frequency obtained from the dynamic periodic shear deformation, and the uniaxial tensile stress-strain. The glass transition temperature (Tg) is about 0.47 for the simulated polymer network (CL400), and a smooth master curve is obtained for the stress relaxation process by setting the reference temperature Tref = 0.6 via the horizontal shifting process, indicating the validity of TTSP. Furthermore, similar smooth master curves are also achieved for both dynamic periodic shear and uniaxial tensile deformation, which exhibit similar trends and share the identical linear viscoelastic regime in the temperature interval above Tg: 0.55<T<1.0. Importantly, the Williams-Landel-Ferry and Vogel-Fulcher-Tammann equations are both adopted to quantitatively analyze non-linear TTSP behavior when the temperature approaches Tg. For the three mechanical properties, we emphasize that the master curve from TTSP or FTSP is independent of the reference temperature if it is higher than Tg, and based on the linear relation of the shift factor versus the inverse of the temperature higher than Tg, we propose a universal framework for the description of the TTSP or FTSP on the various mechanical properties. Then, we verify that the TTSP seems to be valid for the IPNs-DC system, while it does not hold for both PNCs and IPNs-SF systems because of their structural and dynamic heterogeneity. Furthermore, for PNCs filled with NPs grafted with polymer chains, the TTSP recovers back to be valid because of the enhanced compatibility between polymer and NPs attributed to the grafted polymer chains.

Large amplitude oscillatory shear behavior and gelation procedure of high and low acyl gellan gum in aqueous solution

The rheological properties of gellan fluid gels were investigated using large amplitude oscillatory shear (LAOS) technique in both linear and non-linear viscoelastic regimes, with consideration of high acyl (HA)/low acyl (LA) gellan ratio and Ca2+ concentration. The Lissajous curves and Chebyshev coefficients were used to analyze the LAOS data and successfully provided visual and quantitative representation of microstructural differences between HA and LA gellan gum, respectively. Temperature sweep measurements were performed to monitor the gelation procedure of gellan gum solution. The results show that HA gellan gum forms softer but more stable gels than LA gellan gum, especially at high temperature. And a synergistic interaction between HA and LA gellan gum may exist in the presence of abundant Ca2+ ions. The abovementioned study can allow a better understanding of structural characteristic of gellan gum and provide a practical approach to rheological assessment that facilitates the processing and diversified application of mixed gellan gum.

Impact of gas injection on physicochemical properties of waste activated sludge: A linear relationship between the change of viscoelastic properties and the change of other physiochemical properties

Aeration process in the waste activated sludge treatment accounts for 75% of total energy consumption of the treatment plant. The main purpose of the aeration process is to enhance the biodegradation of the liquid waste. Gas bubbles, rising through the liquid, improves mixing, reduces inhomogeneities in the treatment tank and enhances biological reactions. Thus aeration intensity and several physicochemical properties of feed such as viscosity, total suspended solids, and surface charge play a significant role in the biological reaction.This paper examines the impact of the gas injection rate on some physicochemical properties of waste activated sludge namely rheological properties, suspended solids, soluble COD (sCOD), surface tension, and zeta potential. The impact of four different gas flow rates on four different concentrations of waste activated sludge properties was analysed.The results showed that in linear viscoelastic regime the viscous and elastic modulus decreases linearly with an increase in gas flow rate. The amount of stress imposed by gas injection also showed a direct relationship with gas velocity. Gas injection also showed a substantial impact on soluble COD, suspended solids, and zeta potential. Additionally, a linear relationship was observed between the percentage change in the above mentioned physical properties and stress imposed by gas injection. These results confirm that gas injection produces additional shear impacting sludge physicochemical properties and therefore changes its rheological behaviour. The extra stress induced by gas injection can be predicted using a simple model based on sludge concentration and gas velocity.

Linear and nonlinear rheological behavior of native and debranched waxy rice starch gels

Abstract The rheological behaviours of native (WX) and debranched (DB) waxy rice starch gels in the linear viscoelastic (LVE) regime and non-linear (NL) regime were investigated using small amplitude oscillatory shear (SAOS), and large amplitude oscillatory shear (LAOS), respectively. Our results show that WX starch gels exhibited a wider LVE region than DB starch gels, and a scaling of G′ with frequency given by G’∼ω0.26. The G' and G” scaled nearly linear with concentration and were nearly independent of temperature in the tested range. The Lissajous plots showed a gradual yielding of the gels, followed by softening behavior. These results indicated that the WX gel has the characteristics of a weak particle gel (of non-entangled polymers). In contrast, the DB starch produced gels with a more stiff and brittle behavior. The shear moduli had a very strong concentration dependence (∼C10.30) and temperature dependence. The DB starch gel showed more abrupt yielding and strong softening behavior in the Lissajous curves. Creep measurements showed a lower compliance for these gels, and significant creep ringing. These observations suggest the DB starch gels consist of clusters of stiff polymers.

Effect of Sonication Time on Magnetorheological Effect for Monomodal Magnetic Elastomers.

The effect of sonication time on the storage modulus and particle morphology for magnetic elastomers was investigated by dynamic viscoelastic measurements and morphological studies. An ultrasonic wave using a homogenizer was irradiated to magnetic liquids containing 70 wt % carbonyl iron, for up to 30 min before cure. SEM photographs revealed that magnetic particles were randomly dispersed in the polyurethane matrix for magnetic elastomers with sonication. A parameter showing nonlinear viscoelasticity for magnetic elastomers with sonication decreased from 0.75 to 0.4, indicating that the aggregations of magnetic particles had been destroyed by the sonication. The storage modulus at 500 mT at the linear viscoelastic regime significantly increased with the irradiation time, reaching saturation after 10 min; this suggests an increase in the number of chains of magnetic particles by sonication, due to the random dispersion of magnetic particles. At high strains, the storage modulus at 500 mT increased by 8.9 kPa by sonication, indicating the number of chains of magnetic particles which were not destroyed by increased sonication. It was also found that the storage modulus for polyurethane elastomers without magnetic particles was not varied by sonication, suggesting that the polyurethane network was not broken. The effect of sonication time on the viscoelastic properties, and on the magnetorheological response for magnetic elastomers, is discussed.

A minimal rupture cascade model for living cell plasticity

Under physiological and pathological conditions, cells experience large forces and deformations that often exceed the linear viscoelastic regime. Here we drive CD34+ cells isolated from healthy and leukemic bone marrows in the highly nonlinear elasto-plastic regime, by poking their perinuclear region with a sharp AFM cantilever tip. We use the wavelet transform mathematical microscope to identify singular events in the force-indentation curves induced by local rupture events in the cytoskeleton (CSK). We distinguish two types of rupture events, brittle failures likely corresponding to irreversible ruptures in a stiff and highly cross-linked CSK and ductile failures resulting from dynamic cross-linker unbindings during plastic deformation without loss of CSK integrity. We propose a stochastic multiplicative cascade model of mechanical ruptures that reproduces quantitatively the experimental distributions of the energy released during these events, and provides some mathematical and mechanistic understanding of the robustness of the log-normal statistics observed in both brittle and ductile situations. We also show that brittle failures are relatively more prominent in leukemia than in healthy cells suggesting their greater fragility.

Rheological study of the effect of polyethylene oxide (PEO) homopolymer on the gelation of PEO-PPO-PEO triblock copolymer in aqueous solution

The effects of polyethylene oxide (PEO) homopolymer on the gelation behavior of a PEO100-PPO65-PEO100 triblock copolymer (Pluronic F127) were explored in aqueous solution under non-isothermal and isothermal conditions. Under non-isothermal conditions (temperature sweep test), two transition points were observed on increasing temperature, that is, at lower and upper gelation temperatures (LTgel and UTgel, respectively). Between LTgel and UTgel, F127 aqueous solutions maintained a hard gel state. Both molecular weight (MW) and PEO concentration affected these two gelation temperatures. In particular, relative molecular weight (MWrel ≡ molecular weight of PEO homopolymer/PEO segment of F127) affected LTgel. LTgel decreased on increasing PEO concentration at MWrel values of 1. On the other hand, UTgel decreased with increasing PEO concentration regardless of MWrel. Under isothermal conditions (fixed temperature between LTgel and UTgel), the effects of PEO homopolymer on the mechanical properties of F127 hard gel were systemically investigated using small and large amplitude oscillatory shear tests. In the linear viscoelastic regime, total intra-cycle stress and elastic intra-cycle stress were similar, and viscous response increased on increasing PEO concentration. However, at large strain amplitudes, hard gels showed intra-cycle stiffening but inter-cycle softening behavior. In addition, on increasing PEO concentrations, viscous nonlinearities underwent strain-rate thickening followed by strain-rate thinning.

Fractional rheological models of dynamic mechanical behavior of magnetoactive elastomers in magnetic fields

Several fractional rheological models containing one or two fractional elements in addition to the classical springs and dashpots have been proposed to describe the dynamic behavior of magnetoactive elastomers (MAEs) in magnetic fields. To test the models, MAEs containing 70, 75 and 80 wt% of carbonyl iron particles with the diameter of 3–5 μm have been synthesized. Theoretical model parameters have been obtained via fitting experimental frequency dependences of MAE's dynamic modulus measured under dynamic torsion oscillations in linear viscoelastic regime. It has been shown that the simplest rheological models with one fractional element can adequately describe MAEs behavior at low and for some cases high magnetic fields where the main contribution to the MAEs elasticity arises either from polymer network or magnetic particle aggregates, respectively. However, these models fail in describing MAE's dynamics in intermediate magnetic fields where the major restructuring of the magnetic filler particles is expected. The best fitting is realized with two-fractional-element models for a wide range of magnetic fields. The role of two fractional elements in generalized Maxwell model has been interpreted in terms of two main MAE components (namely, polymer network and magnetic particles) whose contributions to material elasticity and viscosity depend considerably on the material composition and magnetic field strength.

Rheological investigation of high-acyl gellan gum hydrogel and its mixtures with simulated body fluids.

Purpose Most of the studies concerning gellan have been focused on its application as a food ingredient, however, gellan is often considered as a candidate for the development of novel pharmaceutical formulations. Taking into account that gellan is ion-sensitive, it can be assumed that its initial mechanical properties can change upon contact with body secretions. Therefore, the aim of the work was to investigate the rheological properties of pure high-acyl gellan gum hydrogel (0.4%) and its mixtures with selected simulated body fluids. Methods The rheological investigations were performed on rotational rheometer and included oscillatory temperature, amplitude, and frequency sweeping. The results enabled estimation of the linear viscoelastic regime, calculation of the cross-over points, and percentage of structure recovery. Results In the case of pure hydrogel no evidence of thermosensitivity was observed in the range of 20-40°C. In pH = 1.2 (NaCl/HCl) the hydrogel structure was almost entirely destroyed. Mixing with phosphate buffer (pH = 4.5) resulted in higher gel strength than after dilution with deionized water. The opposite effect was observed in the case of pH = 7.4. The studies performed for the mixture of GG hydrogel and mucin indicated interaction between the components. The hydrogel elasticity increased in the presence of simulated tear, but decreased in simulated saliva and vaginal fluid. Conclusions In this study, it was shown that the stability of a three-dimensional gellan structure may be affected by pH and the presence of mucin which most probably competed with gellan gum in divalent cations binding. The observations presented in this study may be important in terms of potential application of gellan gum as a potential carrier in drug delivery systems.

Dynamics of drop impact on solid surfaces: evolution of impact force and self-similar spreading

We investigate the dynamics of drop impacts on dry solid surfaces. By synchronising high-speed photography with fast force sensing, we simultaneously measure the temporal evolution of the shape and impact force of impacting drops over a wide range of Reynolds numbers ($\mathit{Re}$). At high $\mathit{Re}$, when inertia dominates the impact processes, we show that the early time evolution of impact force follows a square-root scaling, quantitatively agreeing with a recent self-similar theory. This observation provides direct experimental evidence on the existence of upward propagating self-similar pressure fields during the initial impact of liquid drops at high $\mathit{Re}$. When viscous forces gradually set in with decreasing $\mathit{Re}$, we analyse the early time scaling of the impact force of viscous drops using a perturbation method. The analysis quantitatively matches our experiments and successfully predicts the trends of the maximum impact force and the associated peak time with decreasing $\mathit{Re}$. Furthermore, we discuss the influence of viscoelasticity on the temporal signature of impact forces. Last but not least, we also investigate the spreading of liquid drops at high $\mathit{Re}$ following the initial impact. Particularly, we find an exact parameter-free self-similar solution for the inertia-driven drop spreading, which quantitatively predicts the height of spreading drops at high $\mathit{Re}$. The limit of the self-similar approach for drop spreading is also discussed. As such, our study provides a quantitative understanding of the temporal evolution of impact forces across the inertial, viscous and viscoelastic regimes and sheds new light on the self-similar dynamics of drop-impact processes.