Search results for "Polypropylene"
showing 10 items of 177 documents
Polypropylene-based melt mixed composites with singlewalled carbon nanotubes for thermoelectric applications: Switching from p-type to n-type by the …
2017
Abstract The thermoelectric properties of melt processed conductive nanocomposites consisting of an insulating polypropylene (PP) matrix filled with singlewalled carbon nanotubes (CNTs) and copper oxide (CuO) were evaluated. An easy and cheap route to switch p-type composites into n-type was developed by adding polyethylene glycol (PEG) during melt mixing. At the investigated CNT concentrations of 0.8 wt% and 2 wt% (each above the electrical percolation threshold of ∼0.1 wt%), and a fixed CuO content of 5 wt%, the PEG addition converted p-type composites (positive Seebeck coefficient (S)) into n-type (negative S). PEG was also found to improve the filler dispersion inside the matrix. Two co…
Thermoanalytical study of nucleating effects in polypropylene composites
1996
Interfacial structure plays an important role in the performance of polypropylene composites. Transcrystalline interfacial layer were determined in talc filled polypropylene. The crystallization and melting behaviour of talc and CaCC3 filled polypropylene could be modified with smaller amount of additives like elastomer and surfactants. Through the effect of these additives the structure of interface and the degree of crystallinity could be controlled in filled polypropylene.
Recovery of dissolved methane through a flat sheet module with PDMS, PP, and PVDF membranes
2022
Abstract A degassing contactor using a flat sheet membrane module (FM) was operated in sweep gas mode to study the performance of several commercial polymer membranes, both dense (polydimethylsiloxane, PDMS) and microporous (polypropylene, PP, and polyvinylidenefluoride, PVDF), for the recovery of dissolved methane from water. Non-steady state experiments were conducted at different liquid (QL, 3.5–40.5 L h-1) and gas flow rates (QN2, 0.05–15.00 L h-1). In the case of PDMS, PP, and when PVDF was operated at moderate high QL (≥ 21 L h-1), similar methane removal efficiencies (RE) were obtained. In the case of PVDF operated at relatively low QL (3.5 L h-1), a lower RE was observed. A model fo…
Structure and Mechanical Properties of Melt Intercalated Po1lypropylene–Organomontmorillonite Nanocomposites
2010
The preparation and properties of polymer nanocomposites, obtained by melt-compounding of polypropylene (PP) and organomontmorillonite (OMMT) modified by different alkyl ammonium salts, are described. A copolymer of maleic anhydride and PP was used as a compatibilizing additive. Nanocomposites with OMMT content of 1, 5 and 10 wt% were prepared and tested. The influence of OMMT content on the tensile stress–strain curves, elastic modulus, yield and tensile strength, and ultimate elongation of the nanocomposites is determined. The results of measuring the microhardness and impact strength of polymer nanocomposites are presented. Long-term creep tests were performed to predict the long-term de…
Volatile compounds extracted from polypropylene sheets by hot water :influence of the temperature of sheets injection
1993
A study was made on polypropylene (PP) pellets degraded and not degraded and pointed out the presence and olfactive importance of volatile components extracted from PP pellets by hot water. Plastic packaging materials correspond to a further step of manufacturing: the injection step, and this is often conducted at high temperature. PP (not degraded) and PP-CR (degraded) were transformed into sheets at several temperatures; Lickens-Nickerson extracts were made and allowed the quantification of volatile compounds already identified. A statistical analysis showed that temperature was a very significant parameter. An increasing injection temperature (275 or 300°C° creates increasing quantities …
Functionalized siloxane‐silsesquioxane resins and polypropylene‐based composites: Morphological, structural, thermal, and mechanical properties
2018
Non‐functionalized and n‐alkyl‐functionalized siloxane‐silsesquioxane resins (S4SQ) were synthesized and characterized to confirm their structure and properties. Polypropylene (PP) composites with S4SQ resins as fillers were prepared by the melt blending. The influence of the kinds and amounts of fillers on the structural, morphological and thermal properties as well as mechanical characteristics and processability was determined. High compatibility of composites with functionalized resins resulted in more homogenous dispersion of filler particles in comparison with the composites which contained a non‐functionalized resin. Moreover, the introduction of S4SQ resins into PP strongly affected…
Accelerated weathering of polypropylene/wood flour composites
2008
Abstract Wood–plastic composites (WPCs) have received increasing attention during the last decades, because of many advantages related to their use. Some of their main applications are represented by outdoor furnishing and decking; therefore, it is important to assess their behaviour under UV exposure. In this work, polypropylene/wood flour composites were prepared and their resistance to photooxidation investigated. The composites were prepared by extrusion and compression moulding, and were subjected to mechanical tests, FTIR analysis and molecular weight measurements. The results showed that the composites retained a higher fraction of the original mechanical properties after accelerated…
Improved experimental characterization of crystallization kinetics
2005
Polymer solidification occurring in many processes, like for instance injection molding, compression molding and extrusion, is a complex phenomenon, strongly influenced by the thermo-mechanical history experienced by the material during processing. From this point of view, characterization of polymer crystallization in the range of processing con- ditions, i.e. including high cooling rate, is of great technological and academic interest. Quiescent, non-isothermal crys- tallization kinetics of two polypropylene resins were investigated using a new method, based on fast cooling of thin samples with air/water sprays and optical detection of the crystallization phenomenon. The range of cooling …
Thermal stability of PP with acetylated sisal fiber: Romero Garc�a kinetic method
2003
This work deals the effect of acetylated and non-acetylated sisal fiber 011 thermal degradation of polypropylene. Applying the R-G method at constant conversion levels of 0.1, 0.3, 0.5, 0.7 and 0.9 to thermograms of the ”PP/untreated sisal fiber” blend, E, values of 99, 213, 224, 187, and 145 kJ/mol were obtained, whereas they were 99, 299, 255, 205, 154 kJ/mol for the “PP/treated sisal fiber” blend. On the other hand, with the R-G method at constant temperature, activation energies within the range of 156-417 kJ/mol were obtained for the “PP/treated sisal fiber” blend and within the range of 126-344 kJ/mol for the “PP/untreated sisal fiber” blend. Additionally, the method establishes as do…