Thermo-soil weathering and life cycle assessment of carbon black, silica and cellulose nanocrystal filled rubber nanocomposites.

Carbon black (CB) and silica (Sil) as rubber reinforcement have raised environmental concerns for being high resources consumptive and less susceptible towards biodegradability. Cellulose nanocrystal (CNC) has demonstrated great potentials for use as biodegradable nanofillers in rubber nanocomposites while evaluation of its environmental impacts with optimal end-of-life (EOL) choices is not carried out. To simulate realistic EOL, thermo-oxidative aging and soil burial aging behaviors of rubber nanocomposites with 33.3% filler were performed. The environmental weathering performance modeled with the help of life cycle assessment (LCA) illustrates increased biodegradation susceptibility with partial replacement of CB or Sil with CNC in the nanocomposites, hence promoting the environmental solutions for waste minimalization by enhancing the biodegradability potentials. In terms of LCA, the CNC incorporation contributes more to the environmental impacts in manufacturing but greatly lowers the EOL choices, by reducing the global warming potential values.

Viscoelastic Rheological Behaviors of Polypropylene and LMPP Blends.

Dynamic oscillatory shear testing is used to investigate polymeric viscoelastic behaviors. Small and large amplitude oscillatory shear tests are the canonical method for characterizing the linear and nonlinear viscoelastic behaviors of any polymeric material. With prominent and abundant work on linear viscoelastic studies, the nonlinear behavior is evasive in terms of generating infinite higher harmonics in the nonlinear regime. For this reason, intrinsic nonlinearities from large amplitude oscillatory shear (LAOS) studies have recently been used for insights on microstructural behaviors. This study is carried out for linear and nonlinear viscoelastic behavior with a main focus on LAOS of isostatic polypropylene (iPP) and relatively new low molecular weight and low modulus polypropylene-based polyolefin (LMPP) blends. The morphological results showed reduced spherulitic crystal nucleus size and increased distribution in blends with increasing LMPP. The blends showed subtle linear viscoelastic responses with strong nonlinear mechanical responses to variant strain and stress compared to pure iPP. The intracycle strain thickening and intracycle strain stiffening of high-content LMPP blends were comparatively dominant at medium strain amplitudes.

Effects of ionic liquid on cellulosic nanofiller filled natural rubber bionanocomposites.

Cellulosic nanofillers are sustainable replacements of synthetic fillers while the agglomeration limits their potentials in high-performance rubber bionanocomposites. Herein, we investigate the effects of ionic liquid (IL) on cellulose nanocrystal and cellulose nanofibril filled natural rubber (NR) compounds and vulcanizates. The results indicate that IL improves the dispersion of cellulosic nanofillers, crosslinking density of NR matrix and mechanical strength of the vulcanizates. Invesigations of viscoelastic rheological behaviors show amplitude of Payne effect faints in compounds and raises relatively in vulcanizates with the increment of cellulosic nanofillers and IL.

Large amplitude oscillatory rheology of silica and cellulose nanocrystals filled natural rubber compounds.

Nanoparticles reinforce rubbers and enhance Payne effect for the compounds experiencing large amplitude oscillatory shear deformation. Herein the effects of silica and cellulose nanocrystals on the Payne effect of natural rubber compounds are investigated by stress decomposition methods for clarifying the elastic and viscous nonlinearities varying with filler content and composition. The Payne effect is in general characterized by intercycle strain softening and shear thinning behaviors and intracycle hardening and thinning behaviors at high strain (strain rate) amplitudes while the filler influences the behaviors markedly at intermediate strain (rate) amplitudes. Especially, the addition of cellulose nanocrystals in the silica filled compounds improves the elastic nonlinearity and greatly weakens the viscous nonlinearity, providing a perspective on understanding the Payne effect for manufacturing high-performance rubber materials.

Rheological and Mechanical Properties of Silica/Nitrile Butadiene Rubber Vulcanizates with Eco-Friendly Ionic Liquid.

In this paper we designed greener rubber nanocomposites exhibiting high crosslinking density, and excellent mechanical and thermal properties, with a potential application in technical fields including high-strength and heat-resistance products. Herein 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) ionic liquid was combined with silane coupling agent to formulate the nanocomposites. The impact of [EMIM]OAc on silica dispersion in a nitrile rubber (NBR) matrix was investigated by a transmission electron microscope and scanning electron microscopy. The combined use of the ionic liquid and silane in an NBR/silica system facilitates the homogeneous dispersion of the silica volume fraction (φ) from 0.041 to 0.177 and enhances crosslinking density of the matrix up to three-fold in comparison with neat NBR, and also it is beneficial for solving the risks of alcohol emission and ignition during the rubber manufacturing. The introduction of ionic liquid greatly improves the mechanical strength (9.7 MPa) with respect to neat NBR vulcanizate, especially at high temperatures e.g., 100 °C. Furthermore, it impacts on rheological behaviors of the nanocomposites and tends to reduce energy dissipation for the vulcanizates under large amplitude dynamic shear deformation.

Optimization of Mechanical and Thermal Properties of iPP and LMPP Blend Fibres by Surface Response Methodology.

Optimization of the mechanical and thermal properties of isotactic polypropylene (iPP) homopolymer blended with relatively new low molecular low modulus polypropylene (LMPP) at different blend ratios was carried out via surface response methodology (RSM). Regression equations for the prediction of optimal conditions were achieved considering eight individual parameters: naming, elongation at break, tensile strength and elastic modulus, crystallization temperature (TC), first melting temperatures (TM1), heat fusion (Hf), crystallinity, and melt flow rate (MFR), which were measured as responses for the design of experiment (DOE). The adjusted and predicted correlation coefficient (R²) shows good agreement between the actual and the predicted values. To confirm the optimal values from the response model, supplementary experiments as a performance evaluation were conducted, posing better operational conditions. It has been confirmed that the RSM model was adequate to reflect the predicted optimization. The results suggest that the addition of LMPP into iPP could effectively enhance the functionality and processability of blend fibres if correctly proportioned.