Search results for "COMPOSITE"
showing 10 items of 4584 documents
Bio-inspired surface modification of iron oxide nanoparticles for active stabilization in hydrogels
2020
Biological materials employ a variety of dynamic interactions in sophisticated composite structures to function adaptively on different time and length scales. Inspired by such designs we develop a novel surface modification approach to promote dynamic interactions between nanoparticles and polymer chains in physical and double network hydrogels. Physical hydrogels are formed via reversible complexation of borate ions with poly(vinyl alcohol) (PVA) and chemical crosslinks are introduced by electron beam irradiation. Dopamine is used for surface modification of magnetic iron oxide nanoparticles (MNPs) in two different ways: the direct treatment results in anchoring via catechol groups, where…
An investigation on using pre-treated tyre rubber as a replacement of synthetic polymers for bitumen modification
2015
Rubberized bitumen obtained through a swelling process, has widely proven to be a successful technology for asphalt pavement applications and a solution to reduce the dismantling of tyre rubber on landfills. However, this technology presents two main operative issues which needs the adoption of costly special equipment. Firstly, significant high value of High Temperature Viscosity (HTV) which imposes mixing and compaction difficulties and leads to increased energy consumption and emissions. Furthermore, during the hot storage period, phase separation between rubber particles and the base bitumen could occur. Developing Recycled Tyre Rubber Modified Bitumen (RTR-MBs) with improved storage st…
LARGE DEFORMATION CREEP BEHAVIOR OF A SOLID POLYMER.
1981
Abstract The effect of loading rate and strain on the creep behavior after sample yielding has been studied in previous communications (14–15) for Mylar in tension and for Lexan in compression. In this work the creep behavior of Lexan samples previously elongated is considered both in tension and in compression. A procedure which collects all the data independently of both loading rate and initial creep strain is proposed.
Influence of“controlled processing conditions” on the solidification of iPP, PET and PA6
2002
In this work reliable experimental data for three semicrystalline polymers (iPP, PA6, PET) crystallised under pressure and high cooling rates are supplied. These results were achieved on the basis of a model experiment where drastic controlled solidification conditions are applied. The final objective was to quantify the effect of two typical operating conditions (pressure and cooling rate) on the final properties and morphology of the obtained product. The influence of processing conditions on some macroscopically relevant properties, such as density and micro hardness is stressed, together with the influence of processing conditions on the product morphology, investigated by means of Wide…
The use of the indentation test for studying the solidification behaviour of different semicrystalline polymers during injection moulding
2005
Summary: An in-line method for monitoring the solid-ificationprocess during injection molding of semicrystallinepolymers (demonstrated previously in J. Appl. Polym. Sci.2003, 89, 3713) is based on a simple device, where anadditional ejector pin is pushed on the injection molded partatdifferenttimesduringthesolidificationphase.The‘inden-tation depth profile’, i.e., residual deformation as a functionoftime,wasobtainedandallowedtodeterminetheevolutionof the solidification front in the mold as a function of thecooling time. The present work shows the reliability andthe powerfulness of the aforementioned method for a largevariety of different semicrystalline polymers (PET, PBT,polyamide-6 PA6, isota…
Deformation recovery behavior of a solid polymer after tensile yielding
1984
In this work the deformation recovery behavior of an amorphous polymer after large tensile deformation is studied at different temperatures. The effect of three parameters other than temperature has been pointed out in previous works (1–3).
Deformation recovery behaviour of a solid polymer after tensile yielding
1987
In this work the deformation recovery behavior of an amorphous polymer after large tensile deformation is studied at different temperatures. The effect of three parameters other than temperature has been pointed out in previous works (1–3). The data here presented indicate that the influence of all parameters, including temperature, on recovery behavior can be related to the residual stress, σ *, at the beginning of recovery test. This suggests to plot the recovery versus time curves, relative to different sets of parameters including temperature, by means of the same normalizing groups which were adopted in (2), thus shifting all curves towards a single master curve.
A new equipment to measure the combined effect of humidity, temperature, mechanical stress and UV exposure on the creep behaviour of polymers
2008
To be able to study and predict the physical properties of a polymeric material under different environmental conditions is very important. Moisture, UV irradiation, thermal and mechanical stresses can dramatically change the characteristics of the material and hinder some specific applications. In this work, a new equipment able to perform creep tests under different environmental conditions (temperature, humidity, stress) is presented. Some preliminary results are also presented using a sample of polyamide 6. As this polymer is sensitive to all these variables, it is appropriate to verify the effectiveness of the new instrument.
Viscoelastic recovery behavior following Atomic Force Microscope nanoindentation of semi-crystalline poly(ethylene)
2007
The residual imprint left behind by the AFM nanoindentation of polymers has been seldom studied in the past. In this work, the evolution of indentations at room temperature performed on a semicrystalline poly- (ethylene) in a broad range of experimental conditions is presented. The study shows that the recovery after 24 h is substantial, although not complete. Moreover, the dynamics of the recovery process is not seen to depend on the magnitude of the applied load for the nanoindentation, but instead on the rate of the indentation used. This points out that viscoelastic processes are minimized when performing fast nanoindentations, while at low loading rates there seems to be a residual vis…
The use of master curves to describe the simultaneous effect of cooling rate and pressure on polymer crystallization
2003
In a previous work a master-curve approach was applied to experimental density data to explain isotactic polypropylene (iPP) behaviour under pressure and high cooling rates. Suitable samples were prepared by solidification from the melt under various cooling rate and pressure conditions with the help of a special apparatus based on a modified injection moulding machine. The approach here reported is more general than the case study previously shown, and is suitable to be applied to several materials and for different measures related to crystalline content. The proposed simple model is able to predict successfully the final polymer properties (density, micro-hardness, crystallinity) by supe…