Polyethylene

In this paper, a study on the batch processing and characterization of microcellular foamed high-density polyethylene (HDPE/iPP) blends is reported. A microcellular plastic is a foamed polymer with a cell density greater than 109 cells/cm3 and fully grown cells smaller than 10 µm. Recent studies have shown that the morphology and crystallinity of semicrystalline polymers have a great influence on the solubility and diffusivity of the blowing agent and on the cellular structure of the resulting foam in microcellular batch processing. In this research, blends of HDPE and iPP were used to produce materials with variety of crystalline and phase morphologies to enhance the subsequent microcellular foaming. It was possible to produce much finer and more uniform foams with the blends than with neat HDPE and iPP. Moreover, the mechanical properties and in particular the impact strength of the blends were significantly improved by foaming.
(citation # 293)

The present investigation was carried out to study the effect of different concentrations of calcium chloride (1%, 1.5%, 2%), paraffin wax coating and different wrapping materials (polyethylene, carton paper) inorder to increase the shelf life and to avoid the postharvest losses of Banky cultivars of apple. In physical characteristics general appearance (color and shape of fruit), weight loss percentage and

Results of long-term hydrostatic strength study of piping systems made from polyethylene with increased temperature resistance PERT type II of Hostalen 4731B without reinforcement are presented and discussed in this paper. The different approximations of durability curves and various equivalent stress measures are considered and compared. An analytical expression for the maximum allowable internal pressure as function of service life of pipes, temperature, geometrical parameters of pipe cross-section and material properties is given. Pipes without reinforcement with nominal outer diameters from 32 mm to 225 mm were analyzed to assess long-term hydrostatic strength using equivalent stress, provided that there is no change in mechanism of damage accumulation. This allowed us to use linear extrapolation into area of long service life. The results indicate possible use of pipes SDR7.4 in heating networks for 50 years with heat transfer fluid parameters of 95 °C and internal pressure of 1 MPa.

The Present work includes, degradation of polyethylene under different environmental conditions to know the effect of physical, chemical and biological factors prevailing in those conditions on degradation of polyethylene. Plastic films viz., Low density polyethylene (LDPE), High density polyethylene (HDPE) and High molecular weight high density polyethylene (HMHDPE) each were incubated in three different conditions viz., black soil, sandy soil and red soil for a period of 3 months. The changes in the properties of plastic films after incubation was studied by change in the weight of the plastic film and mechanical parameters like tensile strength, breaking load and percentage of elongation. Among all the plastic films HDPE was found to be highly susceptible with 33% weight loss and 40% reduction in percentage of elongation compared to LDPE with 26% weight loss and 34 % reduction in percentage of elongation in black soil. Whereas HMHDPE found to be highly resistant in all the soils with no significant weight loss and percentage of elongation (15%). None of the plastic films had shown degradation in sandy soil even after incubation for 3 months. FTIR spectroscopy results showed that HDPE film incubated in black soil had undergone extensive degradation when compared with un incubated HDPE film.

The objective of this study was to investigate the outcome of revision total knee arthroplasty (TKA) in relation to the cause of index failure, the characteristics of the index procedure, and the elapsed time between index TKA and revision. A retrospective review based on a prospective database was performed on 146 consecutive revision TKA's. Variables tested were the cause of index failure; the elapsed time between the index and revision procedure; patient age at time of revision; partial or total revision of the implants; the performance of a tibial tubercle osteotomy; the presence of radiolucent lines; postoperative patellar tracking; and coronal plane alignment. Outcomes were measured with the Knee Society Knee Score (KS), Function Score (FS), and X-ray evaluation. Mean KS improved from 27.6 (SD 21.6) to 71.5 (SD 24.2) after revision (P < 0.0001), mean FS from 27.5 (SD 22.7) to 53.3 (SD27.7), P < 0.0001. Overall survival rate was 90% at 5 years and 85% at 10 and 14 years. The cause of index failure had no significant influence on any of the outcome parameters. Significantly, better outcomes were noted for partial revisions and for revisions in older patients. Early revisions (<2 years) were mostly performed for infection and instability, whereas late revisions (>2 years) were mostly performed for polyethylene wear and loosening. The survival rate for late revisions was significantly better than for early revisions (P = 0.002). Revision TKA leads to a significant reduction in symptoms and improvement in function. The worst results can be expected for early revisions in young patients. Revision TKA is a demanding procedure with variable results and should therefore be performed by experienced surgeons. Therapeutic study-Level IV.

Growth and osmotic potential of calli induced from leaf- and root-derived tissues of six tepary bean lines (Phaseolus acutifolius) varying in drought resistance were assessed in vitro after polyethylene glycol-induced (10%, PEG-10,000) dehydration. Calli of resistant teparies were characterized by low initial osmotic potential (ψs) and relative growth rate (RGR) on medium lacking PEG (−0.30 MPa). However, calli of both resistant and sensitive lines were similar in dry matter percent (DM). Presence of PEG in the medium (−0.58 MPa) elevated DM in all teparies except one resistant line. Both leaf- and root-derived calli of sensitive teparies exhibited osmotic adjustment (OA) but reduced RGR that remained after rehydration in one line. We concluded that preexisting force of low cellular ψs rather than induced OA plays an important role in buffering adverse effects of dehydration and conditioning drought resistance of tepary beans. This information may aid Phaseolus breeders in screening for drought resistance among large number of accessions.

Degenerative disc disease is one of the most frequently encountered spinal disorders. The intervertebral disc is a complex anatomic and functional structure, which makes the development of an efficient and reliable artificial disc a complex challenge. Not only is the disc function arduous to reproduce, but there are important consequences associated with the conception and the choice of materials that will have to bear the loads. Biochemical problems have complicated things even more. Two different principles have been applied in the realisation of a discal replacement: a metallic and/or polyethylene prosthesis allowing mainly mobility or a prosthesis enabling the reproduction of viscoelastic properties. Of course some devices attempt to combine both principles. In this paper we will try to present, in chronological order, an overview of the designs published in the literature as well as in the patents granted in this field. The very fact that such a long list of implants, based on ...

Reverse total shoulder arthroplasty (RTSA) is widely used; however, the effects of RTSA geometric parameters on joint and muscle loading, which strongly influence implant survivorship and long-term function, are not well understood. By investigating these parameters, it should be possible to objectively optimize RTSA design and implantation technique. The purposes of this study were to evaluate the effect of RTSA implant design parameters on (1) the deltoid muscle forces required to produce abduction, and (2) the magnitude of joint load and (3) the loading angle throughout this motion. We also sought to determine how these parameters interacted. Seven cadaveric shoulders were tested using a muscle load-driven in vitro simulator to achieve repeatable motions. The effects of three implant parameters-humeral lateralization (0, 5, 10 mm), polyethylene thickness (3, 6, 9 mm), and glenosphere lateralization (0, 5, 10 mm)-were assessed for the three outcomes: deltoid muscle force required ...

Electro-Fusion (EF) joint is a technique to join Polyethylene pipes (PE) pipes which carry gas or water medium. Generally it is assumed that the PE pipe has a 50 year life. But PE pipes get failed before its natural lifetime due to environmental load and conditions. PE joining is unavoidable in PE gas distribution pipe network. Failure of EF joint is a fundamental reason for the decrease in service life. This paper includes principles of Electro-fusion joint, temperature distribution, stress distribution due to thermal and structural loading. Due to this loading condition, inner cold region of EF joint has highly stress concentrated area. This paper analyzed using finite element analysis and found that the inner pressure causes to increase the gap between pipe and fitting while thermal load and external pressure tries to counteract the peeling effect. Due to this peeling effect, inner cold region acts as a crack initiation region. Weld joint strength depends upon the procedure adopted during EF joint which includes heating-cooling cycle, scrapping and contamination on joining surface are significant for the strength and life of the joint.