EFFECT OF TRIAXIAL STRESS CONSTRAINT ON THE DEFORMATION AND FRACTURE OF POLYMERS

One purpose of this paper is to give a brief overview on the research status of deformation,fracture and toughening mechanisms of polymers,including experimental,theoretical and numerical studies.Emphasis is on the more recent progresses of micromechanics of rubber particle cavitation and crazing,and the de- velopment of fracture criteria for ductile polymers. The other purpose is to study the effect of triaxial stress constraint on the deforma- tion and fracture behavior of polymers.Polycarbonate(PC),acrylonitrile-butadiene- styrene(ABS)and PC/ABS alloy are considered in this investigation.A series of circumferentially blunt-notched bars are used to experimentally generate different tri- axial stress fields.The fracture surfaces of specimens with different notch radius are examined by scanning electron microscope(SEM)to study the fracture and tough- ening mechanisms of polymer alloy.It is shown that the triaxial stress constraint has a significant effect on the deformation,fracture and toughening of PC,ABS and PC/ABS alloy.We will also discuss the extent to which a micromechanies criterion proposed by the first author can serve as a fracture criterion for ductile polymers. A new ductile fracture parameter is emphasized,which can be employed to evaluate the fracture ductility of polymers.Stress state independence of the parameter for the PC,ABS and PC/ABS alloy has been experimentally verified.

A Review on Utilization of Light Weight Fly Ash Cenosphere as Filler in both Polymer and Alloy-Based Composites

Fly Ash Cenospheres(FACs)are obtained from the coal power plants in the form of hollow spherical particles by burning the coal.FAC was started to use in early 1980-1985 as lightweight filler material in producing composites of cementitious and at present many researchers are focusing on use of FAC as filler in polymer and metals.In this paper,the systematic review on research activities and application of FAC in manufacturing light weight products are done.The influence of FAC on the physical and mechanical properties of incorporated polymer and alloy-based composites were summarized.Prospects of future for its use were also suggested and summarized in this paper.

In-situ constructed polymer/alloy composite with high ionic conductivity as an artificial solid electrolyte interphase to stabilize lithium metal anode

Lithium(Li)metal is regarded as the best anode material for lithium metal batteries(LMBs)due to its high theoretical specific capacity and low redox potential.However,the notorious dendrites growth and extreme instability of the solid electrolyte interphase(SEI)layers have severely retarded the commercialization process of LMBs.Herein,a double-layered polymer/alloy composite artificial SEI composed of a robust poly(1,3-dioxolane)(PDOL)protective layer,Sn and LiCl nanoparticles,denoted as PDOL@Sn-LiCl,is fabricated by the combination of in-situ substitution and polymerization processes on the surface of Li metal anode.The lithiophilic Sn-LiCl multiphase can supply plenty of Li-ion transport channels,contributing to the homogeneous nucleation and dense accumulation of Li metal.The mechanically tough PDOL layer can maintain the stability and compact structure of the inorganic layer in the long-term cycling,and suppress the volume fluctuation and dendrites formation of the Li metal anode.As a result,the symmetrical cell under the double-layered artificial SEI protection shows excellent cycling stability of 300 h at 5.0 mA·cm^(−2)for 1 mAh·cm^(−2).Notably,the Li||LiFePO_(4)full cell also exhibits enhanced capacity retention of 150.1 mAh·g^(−1)after 600 cycles at 1.0 C.Additionally,the protected Li foil can effectively resist the air and water corrosion,signifying the safe operation of Li metal in practical applications.This present finding proposed a different tactic to achieve safe and dendrite-free Li metal anodes with excellent cycling stability.

PREPARATION AND CHARACTERIZATION OF SPHERICAL PP/PB ALLOYS WITH MgCl_2-SUPPORTED ZIEGLER-NATTA CATALYST

Polypropylene （PP）/polybutene-1 （PB） alloys within reactor were prepared by MgCl2-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology. First, propylene homo-polymerizations were carried out to form isotactic polypropylene （iPP） particles containing active catalyst. Then, butene-1 was subsequently polymerized to form polybutene-1 phase inside the iPP particles. Finally, iPP/PB alloys with spherical shape and adjustable PB content were synthesized. The catalytic activity and catalytic stereospecificity of the Z-N catalyst in the two-stage polymerization process are discussed. The composition and physical properties of the PP alloys were characterized by FT-IR, 13C-NMR, SEM, DSC and XRD. It was found that the in-reactor PP alloys are mainly composed of PP and PB with a little amount of poly（butene- co-propylene） random copolymers and poly（butene-block-propylene） block copolymers. SEM measurements verified that the PB phases with size in the range of 300-400 nm dispersed in the PP matrix uniformly. The incorporation of PB upon the PP matrix affects the properties of final products greatly.

Investigations on Structure and Properties of Blends of Polypropylene with Polyamide 1010 by Rayleigh Scattering

The phase structure and morphology of polypropylene （iPP） blends with poly（decamethylene sebacamide （polyamide 1010, PA 1010） and the part-compatible alloys （iPP/PA 1010/iPP-g-MAH） are investigated by Rayleigh scattering, i.e. small angle light scattering （SALS）. The structure parameters of SALS, i.e. correlation distance, ac and average chord lengths, /, are calculated. Their variation with the composition of the blends and alloys is discussed. The morphology and structure of fracture surfaces in the blends and alloys are studied by SEM images. The average diameter of dispersed phase in the blends and alloys is calculated by graph processing. The variation of average diameter is similar as that of average chord lengths of dispersed phases. The mechanical properties of the blends and alloys are analyzed and the relation of modulus and yield stress with the composition is studied. It is confirmed that the correlation between the modulus and the structure parameters is non-linear, while the correlation between the yield stress and the composition or structure parameters is linear.