Narrow Results

The effect of high energy electron irradiation on the microstructure and thermal properties of natural rubber (NR) filled with different fillers at different concentrations are studied. The samples are irradiated with 8 MeV electron beam to a total dose of 100 KGy. The change in free volume size and specific heat due to addition of fillers and irradiation are studied using positron annihilation lifetime spectroscopy (PALS) and differential scanning calorimetry (DSC) respectively. The Positron lifetime spectra are de-convoluted into two components. The longer lived component $({\tau }_{\mathrm{\text{o}}-\mathrm{\text{Ps}}})$ signifies the pick-off annihilation of ortho-positronium (o-Ps) at free volume site which may be related to the radius of the free volume holes. It is observed that the specific heat $(C_p)$ and free volume size are all affected by both irradiation and addition of fillers.

This study explores the experimentally verifiable rheological parameters of sparsely spaced suspensions of periodically forced rubber spheres in water at low Reynolds numbers. The experimentally verifiable rheological parameters are first normal stress difference, second normal stress difference, intrinsic pressure, and relative viscosity. These parameters are observed to be dependent on the amplitude of the periodic force, particle Reynolds numbers and the volume fraction. The main aim of this study is to determine how well the neutrally buoyant rubber balls (isoprene) flow with the solutions at low Reynolds numbers when forced periodically. The motivation of the problem consideration is to study the collective behavior of the balls when suspended in a dilute limit. An interesting and novel feature of these balls is their non-Newtonian behavior in the Newtonian frame of reference. The model obtained was an integro-differential-equation, which was solved using the Runge–Kutta fourth-order method. Results reveal that the relation between the intrinsic pressure and relative viscosity depicts a nonlinear relation with Reynolds number and proportional to volume fraction. When Rubber balls are forced periodically, they exhibit the non-Newtonian behavior. The relation between the intrinsic pressure and relative viscosity depicts a nonlinear relation with Reynolds number and proportional to volume fraction.

Classical molecular dynamics (MD) simulations are employed to study the thermal conductivity of carbon nanotube/natural rubber (CNT/NR) composite. An aligned CNT/NR system is constructed by atomic potential function and periodic boundary condition and the anisotropic thermal conductivity is predicted in three main directions. The highest thermal conductivity of 80 W/(mK) is predicted along the axial direction of CNT. However, the transverse thermal conductivity perpendicular to the CNT axis is only about 0.6 W/(mK). For obtaining thermal conductivity of randomly oriented CNT/NR composite, an isotropic algorithm is provided from thermal resistance analysis method and results indicate the thermal conductivity improvement of randomly oriented CNT/NR composite is negligible. It is deduced therefore aligning CNTs in NR matrix can be a promising method in thermal management of CNT/NR composite.

Atomic force microscopy (AFM) has the advantage of obtaining mechanical properties as well as topographic information at the same time. By analyzing force-distance curves measured over two-dimensional area using Hertzian contact mechanics, Young's modulus mapping was obtained with nanometer-scale resolution. Furthermore, the sample deformation by the force exerted was also estimated from the force-distance curve analyses. We could thus reconstruct a real topographic image by incorporating apparent topographic image with deformation image. We applied this method to carbon black reinforced natural rubber to obtain Young's modulus distribution image together with reconstructed real topographic image. Then we were able to recognize three regions; rubber matrix, carbon black (or bound rubber) and intermediate regions. Though the existence of these regions had been investigated by pulsed nuclear magnetic resonance, this paper would be the first to report on the quantitative evaluation of the interfacial region in real space.

Friction between filler/filler and filler/matrix in rubber composites is the main factor affecting the heat build-up. In this study, we used dodecanol and silane coupling agent KH-592 to co-modify silica to prepare silica/natural rubber (NR) composites. When dodecanol and KH-592 are grafted onto the surface of silica at the same time, dodecanol can also shield part of the hydroxyl groups by its molecular chain length, which further improves the dispersibility of silica particles. The silane coupling agent KH-592 can form a bridge structure between the silica and the NR matrix under the action of a mercapto group, and improve the interaction between the filler and the matrix. By controlling the use ratio of dodecanol and KH-592, the dispersion of the filler and the interaction between the filler and the matrix can be adjusted. Thereby, the friction between the filler/filler and the filler/matrix is reduced, and a low heat build-up rubber composite material is prepared. Through co-modification, we prepared a series of low-heat build-up silica/NR composites, where the minimum heat generation reached 13^∘C. The co-modified silica/NR composite material not only meets the requirements of green tires, but also has low heat build-up characteristics, providing a new strategy for preparing green and energy-saving tires.

The nondegradable nature and toxicity of organic liquid electrolytes reveal the design deficiency of lithium batteries in environmental protection. Biopolymers can be extracted from biomass under mild conditions, thus they are usually low cost and renewable. The unique characteristics of biopolymers such as water solubility, film-forming capability and adhesive property are of importance for lithium battery. The studies on the biopolymer materials for lithium batteries have been reviewed in this work. Although a lot of work on the biopolymer-based battery materials has been reported, it is still a challenge in the design of lithium battery with zero pollution and zero waste.

Perovskite lead zirconate (PbZrO₃) was synthesized in an orthorhombic form at a temperature below the Curie temperature, T_C. The orthorhombic form is a noncentrosymmetric structure which is capable of spontaneous polarization. Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) patterns confirm the successful synthesis of the lead zirconate; and scanning electron microscopy (SEM) micrographs indicate that PbZrO₃ particles are moderately dispersed in the natural rubber (NR) matrix. Without an electrical field, the particles merely act as a ferroelectric filler, which can absorb and store additional stress. Under an electrical field, particle-induced dipole moments are generated, leading to interparticle interaction and a substantial increase in the storage modulus. At a small amount of lead zirconate particulates present in the natural rubber matrix, at a volume fraction of 0.007306, the electrical conductivity increases dramatically by nearly two orders of magnitude at the electrical frequency of 500 kHz.

Positron annihilation lifetime spectra (PLAS) have been measured for natural rubber polymer with different fillers (Titenium dioxide, Nanosilica and Nanoclay) as a function of filler concentration to investigate how these fillers affect the microstructure of free volume of natural rubber. The lifetime spectra is analyzed by using LT9.0 and the longest lived component(τ_o-Ps) is attributed to the pick- off annihilation of o-Ps in free volume sites, available mostly in the amorphous region of polymer. On the basis of the τ_o-Ps values the radii of the free volume holes (R_h) are calculated. The PALS results show that o-Ps lifetime as well as the size of free volume decreases with the increase of filler concentration.

Today, fossil carbon provides us with fuels (energy), polymers (packaging, insulating and building materials, household utensils, glues, coatings, textiles, 3D-printing inks, furnitures, vehicle parts, toys, electronic and medical devices, etc.) and biologically active substances (drugs (Chapter 9), flavorings, fragrances, food additives, plant protection products, etc.). In this chapter we discover the modern materials of our civilization which are very often polymers derived from oil. They are referred to as “plastics” (annual world production: 380 × 10⁶ tons). Their production consumes 8% of the crude oil extracted (ca. 5 billion tons per year). An increasing part of the plastics originates from renewable resources (less than 10% today, see Section 11.10, bio-sourced plastics). Plastics make life easy for us, but at the underestimated cost of damage to our environment (Figure 8.1) and our health. They contaminate the hydrosphere and the agricultural soil. The atmosphere is also contaminated by microplastics…

Relative to the conventional enzymatic treatment of deproteinization, purified natural rubber treated with adsorption precipitation method has better thermal stability because of the removal the water-soluble proteins instead of binding proteins in NR. Thermal degradation mechanisms of purified natural rubber (PNR) were studied by thermogravimetric analysis (TGA) and differential thermal analysis (DSC). The results show that, the removal of water-soluble proteins and the other non-rubber components from the NR leads to a remarkable change in the degradation stabilization. The total activation energy of PNR calculated by Coats-Redfern method was 167.99 kJ/mol, which is 35.05 KJ/mol higher than that of NR. For the whole thermos-oxidative degradation stage, the thermal decomposition mechanism of PNR is similar to that of NR. The thermal decomposition mechanism of PNR corresponds to a three-dimensional diffusion (Jander equation) at the first stage, and a phase boundary controlled reaction (one-dimensional movement) at the second stage. Kinetic analysis showed that activation energy (Ea), activation entropy (ΔH) and activation Gibbs energy (ΔG) values are all positive, indicating that the first thermos-oxidative degradation process of PNR is non-spontaneous.

Unvulcanized polar graft-modified rubbers, including maleic anhydride grafted ethylene propylene diene monomer (MAH-g-EPDM) and 49% methyl methacrylate grafted natural rubber (MMA-g-NR, i.e. MG49 rubber), were empolyed to toughen polystyrene (PS). The results showed that Charpy impact strength of the unnotched PS specimens at room temperature was improved by addition of the graft-modified rubbers. Moreover, Charpy impact strength of the composite increased with increasing content of polar graft-modified rubbers in this study, and the incorporation of MAH-g-EPDM enhanced impact strength of PS more markedly than that of MG49 did. The result of thermogravimetric analysis (TGA) indicated that the addition of MAH-g-EPDM improved the thermal stability of PS, while the incorporation of MG49 reduced it. The result of thermal mechanical analysis (TMA) indicated that the glass transition temperatures of their corresponding PS-based blends increased with the addition of either MAH-g-EPDM or MG49. The glass transition temperatures of PS-based blends increased with increasing polar graft-modified rubbers content. This may be due to the incorporation of the polar grafts. This work may also provide some information for oil-resistant modification of PS due to the polar groups grafted onto the backbone of rubbers.