Papers by Keyword: Polyethylene (PE)

Abstract: It focused on how the low carbon steel surface was pretreated by hydrolyzed KH-560 silane solution and the polyethylene (PE) coatings were prepared on the pretreated surface in the paper. Moreover, the comparison of the adhesive strengths of PE coatings has been made between the coating and the steel substrate surfaces pretreated by silane agents and other various conventional pretreatment methods. The results show that the highest adhesive strength between coatings and steel surface could be acquired on the condition that the concentration of KH-560 was about 5% and the hydrolytic time was 48 hours, and the adhesive strength of coatings coated on the steel substrate surfaces pretreated by silane agents was more or less higher than those pretreated by conventional processes such as sandpaper grinding, acid etching, phosphating and sandblasting by 40.3%, 46%, 17.6% and 13.2%, respectively. The fracture morphology of the coatings coated on silane agent pretreated substrate surface showed cohesive failure, which was also different from the ones coated on the conventional process pretreated substrate surfaces.

Abstract: The mechanical behaviour of single lap adhesive joints was characterized, using two commercial acrylic adhesives. For this purpose the surfaces were cleaned and abraded using fine grit abrasives. The effect of temperature and moisture in the mechanical strength was, also, evaluated. For this characterization, mechanical tests were carried out according procedure and geometry foreseen by ASTM D3163-01 [1] and ASTM D4501-01 [2] standards. The results show that it is possible to get good strengths without great surface preparation. The temperature and moisture effect observed don’t seem to be relevant for the mechanical behaviour.

Abstract: Here we report about the microstructure of a metal-polymer composite that was processed by severe plastic deformation. The composite was prepared by compaction of a sandwich made of Al foils and polyethylene films. This aluminum-polyethylene composite was processed by high pressure torsion and the microstructure was characterized by optical microscopy and scanning electron microscopy. Our experimental data clearly show that in the early stage, the deformation is not homogeneous within the sample, indicating that significant softening occurred. However, at larger number of revolution the deformation progressively reaches the sample centre and the final material exhibits an ultrafine grained composite structure.

Abstract: By mimicking the microstructure of human cortical bone, a variety of bioactive particle reinforced polymer composites have been developed for hard tissue repair. Apart from biological assessments, these composites must be fully evaluated in terms of their mechanical performance before they can be used in patients. The bioactive particles in these composites are normally hard (relative to matrix materials) and brittle bioceramics such as hydroxyapatite (HA), tricalcium phosphate (TCP), Bioglass, etc. The matrices can be either “biostable” polymers such as high density polyethylene (HDPE) and polysulfone (PSU) or biodegradable polymers such as polyhydroxybutyrate (PHB) and poly(L-lactide) (PLLA). These polymers on their own possess different mechanical properties and display different deformation behaviours. With the incorporation of various amounts of particulate HA, TCP or Bioglass, the bone analogue polymeric composites exhibit a spectrum of deformation and fracture characteristics. In our systematic studies of HA/HDPE, Bioglass/HDPE, HA/PSU, HA/PHB, TCP/PHB and a few other bone analogues biomaterials over the past fifteen years, mechanical tests were conducted under a variety of loading conditions (tension, compression, bending, torsion, etc.). Comparisons of deformation and fracture behaviours of these composites were made and presented. The insights that have been gained are important for developing other bioactive ceramic-polymer composites.

Abstract: The conductivity and mechanical properties of carbon black (CB) filled polyethylene (PE) composites depend on the conductive filler, molecular structure of polymer matrix, and the processing methods which are applied. CB filled high density polyethylene without and with glass fibre (GF) composites have been manufactured using single and twin screws extruder. The composite made from the single screw extruder showed a much higher conductivity than that made from twin screws extruder for CB/PE composites with and without glass fibre. The conductive paths are formed at very low CB content (1wt% CB for GF/CB/PE) when using single screw extruder to manufacture. The microstructure of these composites were analysed using SEM.

Abstract: The interaction of cells with polymers is important for their potential applications in medicine and various areas of biotechnology. Their physico-chemical surface properties strongly influence the cell morphology, adhesion and growth. Physical and chemical properties of pristine and modified polyethylene (PE) films were studied. PE was modified by Ar plasma (0–400 s, 2.0 W) and than grafted with amino acid (glycine). Structural and morphological changes of polymer were studied by goniometry and Rutherford back-scattering (RBS). The interaction of these samples with vascular smooth muscle cell (VSMC) from the rat aorta was studied. Number and morphology of the adhered and proliferated cell on the pristine and modified PE was studied in vitro method. It was found that wetting angle of the modified films decreased with exposure time. Experiments in vitro indicated that the adhesion and proliferation of VSMC is increasing function of degradation time and glycine grafting.

Abstract: The properties of polyethylene doped with Ca2+ salt of oxidized cellulose was studied by different techniques. FTIR spectroscopy was used for the determination of crystalline phase in polymer film, surface wettability was determined by standard goniometry and surface morphology was examined by SEM microscopy. Adhesion of mouse 3T3 fibroblasts on the doped polymer was studied in vitro. It was found that the polyethylene doped with the cellulose derivative can be sterilized in boiling water. The number and homogeneity of adhering cells were shown to depend on the surface wettability and morphology.

Abstract: Photo-oxidation of polyethylene (PE) has been studied thoroughly these years owing to its high output and various applications, which makes knowledge about its degradation of vital practical importance. Polyethylene products often suffer from service environment factors including ultraviolet, heat or chemicals, which may deteriorate their mechanical properties. The degradation behavior varies with the chain structure and morphology of polyethylene, e.g., branches, linear segments length and crystallization. Natural degradation of three kinds of polyethylene (HDPE, LDPE and LLDPE) has been examined in samples using different annealing conditions in this work. The extent of degradation, described as carbonyl index, was evaluated by Fourier transform infrared spectroscopy (FTIR). Crystallinity measurements were made using differential scanning calorimetry(DSC). The investigation indicates that the branch structure plays a dominant role in the photo-oxidation of polyethylene. Annealing will change the crystallinity of polyethylene before aging, but do not show obvious dependence on the oxidation.

Abstract: Fattiigue and ttensiille properttiies of speciimens cutt from palllletts made from wastte pllasttiics by usiing of newlly develloped recyclliing apparattus are presentted.. Testted matteriialls are pollypropyllene fiillm,, pollypropyllene pelllletts,, pollyetthyllene,, pollyetthyllene-20wtt%flly ash composiitte and pollyetthyllene -20wtt% callciium carbonatte composiitte.. Itt can be conclluded tthatt tthe newlly develloped recyclliing apparattus make possiiblle tto proviide palllletts made from wastte pollypropyllene and pollyetthyllene wiitth ullttiimatte ttensiille sttrengtths of more tthan niinetty percentt of tthose made from fresh pollypropyllene and pollyetthyllene.. Itt has become cllear tthatt carefull ttreattmentt of composiitte process for wastte pllasttiics enablle tto iimprove fattiigue sttrengtth of pollyetthyllene composiittes by sttrengttheniing tthe iintterface bettween an addiittiive and base matteriiall..

Abstract: For explaining the SCG behavior of polyethylene, the crack layer theory is applied based on the description of two driving forces: crack and PZ. The relations between the speed of SCG, crack length and elapsed time are the most important characteristics of polyethylene resistance to crack propagation, or long-term brittle fracture. The crack layer model of slow crack growth in polyethylene is designed in such a way that it qualitatively reproduces the main features of the process indicated above and makes it possible to quantitatively match any pattern of step-wise crack growth. In this paper, the behavior of SCG of polyethylene is developed for numerical simulation based on the crack layer theory. Some parametric study and applications are addressed based on the developed simulation program.