RELATION BETWEEN DYNAMIC LOSS MODULUS AND DIFFUSION COEFFICIENT IN A MODIFIED PET FIBER

The mobility of polymer chain segments is shown to play a major role in the diffusion ofdisperse dyes in a copolymerization modified PET system, monoepoxy compoundCH_3 (CH_3),OCH_2CH--CH_2 modified PET. The rate of dye diffusion (diffusion coefficient D) hasbeen related to the time-dependent mechanical property, dynamic loss modulus E', which iscontrolled by the mobility of chain segments. In this modified copolyester system, the variance ofamount of modifier in the copolyester fibers causes the change in disperse dye diffusion coefficientto fiber, and in the dynamic loss modulus of the fibers, but the relationship between the diffusionand the dynamic loss modulus is in agreement with the theoretical relation derived by Bell andDumbleton. The relation obtained in this paper is:Ln D=-2. 28Ln E'+26. 81

Reinforcing Effect of Organo-Modified Fillers in Rubber Composites as Evidenced from DMA Studies

The use of organically enhanced kaolin clay as reinforcing filler for NR(natural rubber)and blends of NR with NBR(nitrile-butadiene rubber)and poly BR(butadiene rubber)system were investigated on the basis of DMA(dynamic mechanical analysis).Kaolin clay was modified using a chemical complex of HH(hydrazine hydrate)and SRSO(sodium salt of rubber seed oil).Intercalation of SRSO into kaolin under optimized condition showed an inter-lamellar layer expansion to 4.668 nm,compared to the characteristic d001 XRD(X-ray diffraction)peak of pristine kaolin at 0.714 nm.The morphology,visco-elastic behavior,modulus property,polymer miscibility and Tg(glass transition temperature)of nano-kaolin filled NR and its blend with synthetic rubbers have been studied in detail.DMA showed a diminution in tanδpeak height and a modulus shift in correspondence with increased CLD(crosslink density).Pure NR shows only~1%increase in storage modulus(E′)while adding nanoclay rather than micron sized pristine clay under experimental conditions,because of the feeble interaction between filler and matrix,as compared to blend.An increment of~76%and~117%in E′was recognized by the addition of 4 wt%nanoclay in blends such as BR mK and NBR mK.With loss modulus(E″)pure NR shows only~7%decrease while adding nanoclay,compared to blend.A decrement of~54%and~55%in E″by the addition of 4 wt%nanoclay in BR mK and NBR mK blends were observed.As a whole,DMA was performed to figure out the effect of surface modification enabling to materialize composite.

Damping of aluminum-matrix composite reinforced by carbon nanotube:Multiscale modeling and characteristics

It is a crucial requirement for structure-damping materials to attain both stiffness and damping;unfortunately,the two properties are usually mutually exclusive.This study interestingly demonstrates that introducing Ni atoms into the interface of carbon nanotube(CNT)reinforced aluminum-matrix composites can defeat the conflict of stiffness versus damping.This originates from the gradient variation of the modulus and energy dissipation in the effective interfacial zone.The rule of mixture is modified by taking the interface contribution into account,and a gradient damping model is proposed to account for the contribution of the interface energy dissipation.Molecular dynamics simulations confirm that the proposed multiscale modulus and damping models can describe the elastic modulus and damping behavior of the composites with different volume fractions and different diameters of CNTS.The gradient interface slip caused by the lattice mismatches and misfit dislocations between Ni-coated CNT and aluminum is one of the pathways for achieving unprecedented levels of the product of stiffness and damping.

Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Numerical simulations of longitudinal wave propagation in a rock bar with microcracks are conducted by using the numerical manifold method which has great advantages in the simulation of discontinuities.Firstly,validation of the numerical manifold method is carried out by simulations of a longitudinal stress wave propagating through intact and cracked rock bars.The behavior of the stress wave traveling in a one-dimensional rock bar with randomly distributed microcracks is subsequently studied.It is revealed that the highly defected rock bar has significant viscoelasticity to the stress wave propagation.Wave attenuation as well as time delay is affected by the length,quantity,specific stiffness of the distributed microcracks as well as the incident stress wave frequency.The storage and loss moduli of the defected rock are also affected by the microcrack properties;however,they are independent of incident stress wave frequency.

Effect of ammonium based ionic liquids on the rheological behavior of the heavy crude oil for high pressure and high temperature conditions

Heavy crude oil(HCO)production,processing,and transportation forms several practical challenges to the oil and gas industry,due to its higher viscosity.Understanding the shear rheology of this HCO is highly important to tackle production and flow assurance.The environmental and economic viability of the conventional methods(thermal or dilution with organic solvents),force the industry to find an alternative.The present study was constructed to investigate the effect of eco-friendly ionic liquids(ILs)on the HCO's rheology,at high temperature and high pressure.Eight different alkyl ammonium ILs were screened for HCO's shear rheology at the temperatures of 25-100℃ and for pressures 0.1e10 MPa.The addition of ILs reduced the HCO's viscosity substantially from 25 to 33%from their original HCO viscosity.Also,it aids to reduce the yield stress to about 15-20%at all the studied experimental conditions.Furthermore,the viscoelastic property of the HCO was studied for both strain-sweep and frequencysweep and noticed the ILs helps to increase HCO's loss modulus(G00)by reducing storage modulus(G0),it leads to the reduction of the crossover point around 25-32%than the standard HCO.Mean the ILs addition with HCO converts its solid-like nature into liquid-like material.Besides,the effect ILs chain length was also studied and found the ILs which has lengthier chain length shows better efficiency on the flow-ability.Finally,the microscopic investigation of the HCO sample was analyzed with and without ILs and witnessed that these ILs help to fragment the flocculated HCO into smaller fractions.These findings indicate that the ILs could be considered as the better alternative for efficient oil production,processing,and transportation.

Strain Amplitude Effect on the Viscoelastic Mechanics of Chloroprene Rubber

This paper establishes an empirical formula to predict the strain amplitude effect.A viscoelastic constitutive model-the superposition of a hyperelastic model and a viscoelastic model-is constructed based on the laws of thermodynamics.The Mooney Rivlin model and the Prony series are employed for uniaxial tension testing.The empirical formula is derived using a hysteresis loop;it obtains results that are in agreement with the experimental results of dynamic mechanical analysis(DMA).The empirical formula proposed in this paper has certain accuracy in predicting the dynamic modulus under different strain amplitudes.