Search results for "plastic"

Polymerization of vinylidene fluoride with perfluoropolyether surfactants in supercritical carbon dioxide as a dispersing medium

2006

The heterogeneous polymerization of vinylidene fluoride (VDF) was investigated at 50 °C with supercritical carbon dioxide (scCO 2 ) as a dispersing medium and diethylperoxidicarbonate as an initiator in the presence of different perfluoropolyether surfactants. When FLK 7004A ammonium carboxylate salts were used at a 5% (w/w) concentration with respect to VDF, with an initial pressure of 31-45 MPa and with an olefin concentration of about 5.5 mol/L, monomer conversions up to 63% were obtained, corresponding to a final solid content higher than 200 g/L, and the polymer was collected at the end of the process in the form of a white powder completely composed of microspheres. The effects of the…

Performance-based characterization of recycled polymer modified asphalt mixture

2021

Due to the introduction of secondary materials, the asphalt mixtures to be designed and tested in our laboratories are constantly becoming much more complex than traditional asphalt mixtures making difficult to use conventional laboratory procedure and/or predict expected results. This study proposes a comprehensive characterization of asphalt mixture modified with recycled polymer compound by using both wet and dry process proposing adjustments to laboratory mixing and sample compaction procedure. Accordingly, three AC20 Hot Asphalt Mixture (HMA) were designed and their conventional and performance related properties were assessed by looking at a) Indirect Tensile test (ITS) a) moisture da…

Limiting concepts in extensional flow

1975

A characteristic feature of extensional flows is their potential capability of determining a stable, oriented structure in liquid materials containing elongated particles. With reference to flexible linear macromolecules, either in solution or as polymer melts, the limiting conditions under which such an oriented structure is actually possible are critically reviewed. It is seen that orientation can be obtained either when entanglements are present, i.e. when the polymer molecules form some sort of network, or, if the molecules behave entirely individually, only under very special circumstances. Further, if the objective is the “freezing” of the oriented structure in a partly crystalline, h…

Statistical Mechanics of Polymers: New Developments - International Workshop

2007

Rheological Behaviour, Mechanical Properties and Processability of Biodegradable Polymer Systems for Film Blowing

2017

Films for agricultural or packaging applications are typically made of low density polyethylene (LDPE). They are produced through the film blowing process, which requires the use of polymers with suitable rheological properties. Furthermore, the short shelf-life which is often related to many packed products leads to huge amounts of plastic-based wastes. This suggests the use of biodegradable and/or compostable polymers in replacement for traditional ones. To this regard, only few data exist on the rheological properties of biodegradable polymers undergoing film blowing processing. In this work, a detailed investigation on the rheological, mechanical and processability behaviour of some bio…

Rheological Behavior Under Shear and Non-Isothermal Elongational Flow of Biodegradable Polymers for Foam Extrusion

2013

The production of many items, in particular for food packaging applications, is based on foam extrusion and thermoforming. These operations require the use of polymers which can grant some specific rheological properties, both under shear and elongational flow. In this work, the behavior of some biodegradable polymers [Mater-Bi® and poly(lactic acid)] under shear and non-isothermal elongational flow was investigated and compared with a traditional, non-biodegradable polymer, in order to assess their suitability for industrial-scale foam extrusion and thermoforming. The rheological characterization evidenced the differences between the different biodegradable polymers and the reference polys…

Organocatalytic synthesis of new telechelic polycarbonates and study of their chemical reactivity

2015

Abstract A two-step versatile process for telechelic polycarbonates synthesis is described. 1-n-butyl-3-methylimidazolium-2-carboxylate (BMIM-2-CO2) was used as thermolabile precursor of N-heterocyclic carbene (NHC) organocatalyst. In a first step, synthesized branched fatty diols or commercially available linear diols were reacted with an excess of dimethylcarbonate (DMC) to afford oligocarbonates with methylcarbonate end-groups. Then, the methylcarbonate groups were reacted with hydroxyl groups of 9-decen-1-ol, 4-hexyn-1-ol and 4-hydroxybenzene ethanol leading to telechelic oligomers with alkene, alkyne and phenol functionalities. Reactivity of these end-groups towards polymerization was …

Competition between degradation and chain extension during processing of reclaimed poly(ethylene terephthalate)

1998

During processing of poly(ethylene terephthalate) (PET) hydrolytic chain scission, induced by the presence of small amounts of water, is the main cause of degradation. During repeated reprocessing chain scission can also occur because of the presence of other polymeric contaminants like PVC. In order to avoid or to limit hydrolytic chain cleavage adequate drying of PET before melt processing is necessary. Of course this practice is even more recommended when repeated processing steps are used, as for PET recycling. The behavior of recycling PET obtained from post-consumer water bottles when treated in a melt mixer under different conditions has been investigated in order to better understan…

Titanium isodicyclopentadienide hemimetallocenes for ethylene/styrene copolymerization

2004

Abstract The syndiotactic polymerization of styrene with exo-[(η5-isodiCp)TiCl3] 1/methylalumoxane (MAO; isodiCp=isodicyclopentadienyl) was studied as well as the ethylene/styrene copolymerization with exo-[{η5:η1(N)-isodiCp(SiMe2Nt-Bu)}TiCl2] 2/MAO. These two catalytic systems are stable during polymerization. The half-sandwich titanocene 1 exhibits good syndiospecificity and average activity. The bridged half-sandwich amino complex 2 was found to incorporate styrene into polymer chains at 70 °C. Activity results decrease with increasing styrene concentrations.

Biphasic ethylene polymerisation using ionic liquid over a titanocene catalyst activated by an alkyl aluminium compound

2007

Abstract 1-n-Butyl-3-methylimidazolium tetrachloroaluminate ([BMIM]+[AlCl4]−) was applied to biphasic ionic liquid/hexane ethylene polymerisation as a medium of the Cp2TiCl2 titanocene catalyst activated by alkylaluminium compounds (MAO, AlEt2Cl, AlEt3). The best results were obtained using AlEt2Cl. The results show that catalyst recycling, higher ethylene pressure, and greater Al/Ti molar ratio along with a greater volume of the ionic liquid phase enhance catalyst activity. The polyethylene gathered from the hexane phase is characterised primarily by its high purity. Its physical properties remain polyethylene obtained over a heterogeneous metallocene catalyst. Thus, biphasic ionic liquid …