The size of the minor phase in an immiscible polymer blend can have a significant effect on properties such as the impact strength Few studies, however, have quantitatively considered the parameters controlling the size of the dispersed phase In this paper, light and scanning electron microscopy have been used to examine the size of the minor phase in polypropylene/polycarbonate blends after melt processing The size was examined as a function of both the viscosity ratio (p) and the torque ratio (TR) The viscosity ratio is studied in the regions of p > 1 and p < 1 p has a marked effect on the morphology of the dispersed phase with the phase size increasing by a factor of 3 to 4 times from p = 45 to p = 173 Reduction in the size of the minor phase was achieved below p = 1 with the minimum particle size occurring at p ≃ 015 The results for these systems indicate the presence of upper and lower limits of p beyond which deformation becomes difficult This is shown to be similar in some respects to the behavior of Newtonian fluids in shear flow, although the upper limit extends beyond that observed in the Newtonian fluid studies

The effect of viscosity ratio on the morphology of polypropylene/polycarbonate blends during processing

Influence of composition on the morphology of polypropylene/polycarbonate blends

Taille et distribution de taille de la phase mineure dans les melanges prepares a l'etat fondu

Blends of isotactic polypropylene and ethylene-propylene rubbers: rheology, morphology and mechanics

Objectives To identify and synthesise studies of diagnostic processes of urinary incontinence and to construct an economic model to examine the cost-effectiveness of simple, commonly used primary care tests. Data sources The electronic databases MEDLINE (1966--2002), CINAHL (1982--2002) and EMBASE (1980--2002). Review methods Studies were selected and assessed using the Quality Assessment of Diagnostic Studies (QUADAS) tool. Studies that reported the results of applying the same diagnostic procedure using the same threshold value (cut-off) were pooled using a random effects meta-analysis model to produce pooled estimates of sensitivity, specificity and diagnostic odds ratio together with 95% confidence intervals. Results In total, 6009 papers were identified from the literature search, of which 129 were deemed relevant for inclusion in the review, and these papers compared two or more diagnostic techniques. The gold-standard diagnostic test for urinary incontinence with which each reference test was compared was multichannel urodynamics. In general, reporting in the primary studies was poor; there was a lack of literature in the key clinical areas and minimal literature dealing with diagnosis in men. Only a limited number of studies could be combined or synthesised, providing the following results when compared with multichannel urodynamics. A clinical history for diagnosing urodynamic stress incontinence (USI) in women was found to have a sensitivity of 0.92 and specificity of 0.56 and for detrusor overactivity (DO) a sensitivity of 0.61 and specificity of 0.87. For validated scales, question 3 of the Urogenital Distress Inventory was found to have a sensitivity of 0.88 and specificity of 0.60. Seven studies compared a pad test with multichannel urodynamics; however, four different pad tests were studied and therefore it was difficult to draw any conclusions about diagnostic accuracy. Of the four studies comparing urinary diary with multichannel urodynamics, only one presented data in a format that allowed sensitivity and specificity to be calculated. Their reported values of 0.88 and 0.83 suggest that a urinary diary may be effective in the diagnosis of DO in women. Examination of the incremental cost-effectiveness of three primary care tests used in addition to history found that the diary had the lowest cost-effectiveness ratio of between pound 35 and pound 77 per extra unit of effectiveness (or case diagnosed). Imaging by ultrasound to determine leakage was found to be effective in the diagnosis of USI in women, with a sensitivity of 0.94 and specificity of 0.83. Conclusions This is the first systematic review of methods for diagnosing urinary incontinence. As reporting of the primary studies was poor, clinical interpretation was often difficult because few studies could be synthesised and conclusions made. The report found that a large proportion of women with USI can be correctly diagnosed in primary care from clinical history alone. On the basis of diagnosis the diary appears to be the most cost-effective of the three primary care tests (diary, pad test and validated scales) used in addition to clinical history. Ultrasound imaging may offer a valuable alternative to urodynamic investigation. The clinical stress test is effective in the diagnosis of USI. Adaptation of such a test so that it could be performed in primary care with a naturally filled bladder may prove clinically useful. If a patient is to undergo an invasive urodynamic procedure, multichannel urodynamics is likely to give the most accurate result in a secondary care setting. There is a dearth of literature on the diagnosis of urinary incontinence in men, with no studies meeting the study criteria for data extraction in the diagnosis of bladder outlet obstruction. There is a need for large-scale, high-quality primary studies evaluating the use of a number of diagnostic methods in a primary care setting to be undertaken so that the results of this systematic review can be verified or not. Such studies should include not only an assessment of clinical effectiveness, in this case diagnostic accuracy, but also an assessment of costs and quality of life/satisfaction to inform future health policy decisions. Studies carried out should be reported to a better standard. The recommendations of the Standards for Reporting Diagnostic Accuracy (STARD) initiative should be followed to ensure the accuracy and completeness of reporting design and results.

Systematic review and evaluation of methods of assessing urinary incontinence.

An experimental study was carried out to investigate the effect of mixing on the state of dispersion and rheological properties in the two-phase flow of polymer blends. For the study, blends of polystyrene and polypropylene were used, and two mixing devices were employed: a single-screw extruder combined with a “static mixer,” and a twin-screw compounding machine. Materials of various blending ratios were extruded at a constant temperature (200°C) through a capillary die having an L/D ratio of 20 (D = 0.125 in.). The state of dispersion in the two-phase system was investigated from pictures taken of the microstructure of the extrudate samples. It was found that different mixing devices have a profound influence on the state of dispersion of one polymer in another. Also determined were the rheological properties of the two-phase system investigated, from wall normal stress measurements. Our results show that, when shear stress is used as a parameter, the melt viscosity goes through a minimum, whereas the melt elasticity goes through a maximum. This is regardless of the type of mixing device employed, although the shapes of the curves are affected by the type employed. It is suggested that shear stress, instead of shear rate, be used in correlating the viscoelastic properties of two-phase polymer systems.

The effect of mixing on the modes of dispersion and rheological properties of two‐phase polymer blends in extrusion

Voiding dysfunction following transurethral resection of the prostate: symptoms and urodynamic findings

An experimental study of foam extrusion was carried out to determine the effect of processing variables on the quality of the foam produced. For the study, the chemical blowing agent azodicarbonamide was used, together with an activator and a nucleating agent, to produce thermoplastic foams of low-density polyethylenes. The quality of foam was determined from photomicrographs and the tensile properties of extrudate samples. It was found that the percent elongation correlates with the foam density and that the cell structure (cell size and its distribution) correlates with the ultimate tensile properties of the foam produced. Also, an experimental study was carried out to observe the growth of gas bubbles as the polymer melt containing a blowing agent flows through a rectangular channel constructed of quartz. This experiment helped us to interpret the curved pressure profile of the polymer melt containing a blowing agent as the melt approaches the die exit, whereas the polymer without a blowing agent shows a linear pressure profile.

A study of foam extrusion using a chemical blowing agent

Studies on melt spinning. V. Elongational viscosity and spinnability of two‐phase systems

An experimental study was carried out to investigate the moldability of polymer blends which form two phases in the molten state and the effect of mixing on the morphology and mechanical porperties of molded specimens. Blends of polystyrene with polypropylene and blends of polystyrene with high-density polyethylene were used for this study. A plunger-type injection molding machine (Van Dorn) was employed for molding specimens. To improve the mixing performance of the plunger machine, a Static Mixer (Kenics Corp., Super Nozzle) was installed between the heating cylinder and the sprue. A number of different molding conditions (injection pressure, temperature, injection time, cooling time) were varied, and molded specimens were collected under each molding condition. The specimens were used for studying the degree of dispersion in the blends and for determining the mechanical properties. A differential thermal analysis (DTA) experiment was also carried out to determine the degree of dispersion of the blends in molded specimens. It was found that a linear correlation exists between the blend composition and thermal spectra area of the blends tested.

Young Woo Kim

Papers

The effect of mixing on the modes of dispersion and rheological properties of two‐phase polymer blends in extrusion

Voiding dysfunction following transurethral resection of the prostate: symptoms and urodynamic findings

A study of foam extrusion using a chemical blowing agent

Studies on melt spinning. V. Elongational viscosity and spinnability of two‐phase systems

Morphology and mechanical properties of injection‐molded specimens of two‐phase polymer blends