Stability of Shells of Revolution Made of Fibrous Composite with Damageable Matrix

The bifurcation-stability problem for shells of revolution made of fibrous composite with damageable matrix is formulated and solved. Increase in the damage of the matrix under loading is taken into account __________ Translated from Prikladnaya Mekhanika, Vol. 41, No. 10, pp. 75–83, October 2005.     

Fuming nitric acid treatment of isotactic polypropylene film

Fuming nitric acid treatment has been made on a melt-quenched and an annealed isotactic polypropylene film. The treated samples were characterized by measurements of weight loss, density, molecular weight, spin-lattice,T ₁, and spin-spin,T ₂, relaxation times. Concurrent with the increases in weight loss, density and a decrease in molecular weight, increases inT _1l andF _c , a fraction of crystalline region, and decreases inT _2a andF _a , a fraction of amorphous region, were observed as a consequence of the decrease in an amount of noncrystalline portions. However, unexpected fall inT _1l was also observed after about 2–3 hr of treatment time. These observations were discussed by the structural changes that took place during acid etching.     

Opto-thermal behavior of polypropylene fibres using a modified hot-stage attached to the interference microscope

The influence of temperature on the optical and structural properties of three samples of polypropylene fibres (having different deniers) has been studied over the temperature range (28–67^oC). A hot-stage attached with the Pluta microscope has been modified for this purpose. The effect of temperature on the refractive indices (n, n), the mean polarizabilities per unit volume (P^ll, P) and the optical orientation function f(θ) have been investigated for each sample. The thermal coefficients of the refractive indices were determined. The refractive index profiles are also provided at different temperatures for each of the three tested samples. Microinterferograms are given for illustration.     

Design of the bandpass width, the spectral resolution and the diffraction efficiency of a non-collinear acousto-optic tunable filter of TeO2

The spectral dependencies of the bandpass width, the spectral resolution and the diffraction efficiency of a non-collinear acousto-optic tunable filter of TeO₂ are designed by the method proposed by Chang. The effect of four parameters (the directions of propagation of the acoustic and optic waves, the length of acousto-optic interaction and the power density of the controlling RF-signal) on the filter spectral characteristics is discussed and illustrated from the point of view of practical application. An example of filter design using these dependencies is presented.     

The effect of p-tert-butylcalix[n]arene on γ-radiation degradation of polypropylene

The γ-radiation effect of polypropylene was investigated in the presence of three kinds of p-tert-butylcalix[n]arene (n=4, 6, 8) in air at ambient temperature. The influence of radiation dose and store time upon the mechanical properties of the irradiated PP sheets were measured. The results showed that the radiation stabilization was reduced with the increase of the ring size of calixarenes. Based on the mass spectra and the analysis of post-irradiated product, the mechanism of radiation degradation of p-tert-butylcalix[4]arene has been proposed.     

Photo-oxidation of thick isotactic polypropylene films I. Characterisation of the heterogeneous degradation kinetics

Photo-oxidation kinetics of thick isotactic polypropylene films have been compared to thermal-oxidation kinetics of thin films, and noticeable differences have been found. The non-classical kinetic trend of the former can be described as a three step evolution: a typical induction/autoacceleration POOH build-up at the beginning, an intermediate slower POOH content increase and, finally, a gentler POOH increase, which can be better described by quadratic functions of the oxidation time than by a linear dependence. In addition, a series of oscillations appearing from the beginning of the photo-oxidation are found. This kinetic heterogeneity is suggested to be related to the progression of the oxidation to the inside of the strips. However, the FTIR analysis of the evolution of the POOH band position in both photo and thermal oxidation, enables the observed shape changes to be associated to kinetic stages.     

Transverse superresolution with extended depth of focus using binary phase filters for optical storage system

This paper reports the study of superresolution and extension of depth of focus (DOF) of three-zone binary phase filters (BPFs) under high numerical aperture (NA) focusing. Two three-zone BPFs (BPF1 and BPF2) are specially designed to achieve transverse superresolution and extension of DOF simultaneously for the optical disc system with an objective lens of NA = 0.65. Numerical simulations based on the vectorial diffraction theory indicate that the transverse focal spot size of this system can be as small as that of NA = 0.85 and its DOF is as large as that of NA = 0.6 with acceptable Strehl ratios (> 0.4 for BPF1 and > 0.35 for BPF2) and low side-lobe intensity ratios (< 10%) by using these BPFs. It suggests that the storage capacity of this optical storage system may be improved to the same as that of a system with an objective lens of NA = 0.85. Moreover, the strict requirement of the focusing servo system caused by decreasing wavelength or employing higher NA objective lens can be mitigated. Therefore, these BPFs presented in this paper should be highly interesting for applications of high density optical data storage.     

RHEOLOGY AS A QUALITY CONTROL INSTRUMENT

Quality control in polymer production is a decisive success factor today, growing in importance with the steadily increasing demands regarding the performance of polymeric materials. Rhe-ological methods are ideal for application in quality control, as they allow to draw conclusions regarding both molecular structure and processability from their results. This is especially true for the linear viscoelastic parameters of a polymer melt. Using several examples from industrial practice, the capacity of rheological measurements to clarify quality problems like degradation effects or non-homogeneity is demonstrated. The question of precision and reliability is finally addressed, based on the results of two round-robin tests.     

The Synthesis of Isotactic Polypropylene with Spherical Morphology via Supported Metallocene Catalyst

Tile morphology control of polypropylene products is one of the technological obstaclesto the industrial polymerization of propylene via metallocene catalyst. One efficient wayto solve this problem had been proposed that the metallocene catalyst should besupported on suitable carrier. Although lots of work has been reported'-', up to date, nobreakthrough has been got yet. The stUdies on morphology control of supportedmetallocene catalysts will be of great value in either scientific or practice…     

Structure and properties of composites of highly crystalline cellulose with polypropylene: Effects of polypropylene molecular weight

Composite of highly crystalline fibrous cellulose (CE) and polypropylene (PP) of different molecular weights () was prepared via melting-mixing, maleic anhydride grafted polypropylene (MAPP) was used as a compatibilizer. And the effects of molecular weight of PP on the properties of the composites were investigated. Through the studying of mechanical properties, dynamic mechanical properties, melting and crystallization behaviors, thermo-oxidative properties, water absorption behaviors, and the morphology of the composites, it was found that PP with higher molecular weight revealed stronger interfacial interaction with cellulose in the composites. Compared with the lower molecular weight, the composites derived from higher molecular weight of PP exhibited stronger tensile strength at the same cellulose content.