KEY WORDSPoly(4-methyl-1-pentene) / Ultradrawing / Unusual StressStrain Behavior / Crystal Transformation / New Crystal Form / Recently, ultradrawing of flexible chain polymers has been extensively studied to achieve the maximum mechanical properties.1 -3 Among many polymers studied, only ultrahigh molecular weight (UHMW) polyethylene4-7 and polypropylene 8 -10 have been ultradrawn to the limits in terms of mechanical and physical properties approaching limits.In our current study of ultradrawing of poly(4-methyl-l-pentene) (P4MlP), it was found that single crystal mats of UHMW-P4M 1P could also be drawn to a high draw ratio (DR) of 80 by a two-stage drawing technique. 5 · 8 The ultradrawn films exhibited unusual stress-strain curves for ambient tensile testing. The curve was characterized by three distinct regions consisting of an initial elastic region, a yield region, and finally, a post-yield region. A similar stress-strain curve has been reported only in a few polymers such as wool 11 • 12 and oriented polypivalolactone 13 and poly(butylene terephthalate) 14 where the alpha-beta (helix-planar zigzag or gauchetrans) transformation occurred ·on extension. In contrast to these polymers, however, ultradrawn UHMW-P4MlP showed tensile moduli of 7.5-9.1 GPa in the post-yield region, which were significantly higher than the crystal modulus of 2.9-6.7 GPa 15 ' 16 reported for the ordinary tetragonal form of P4MlP. 17 · 18 In this communication, we report unusual stress-strain behavior observed in ultradrawn films of UHMW-P4MIP and studied in relation to the specific morphology and the crystal structural or conformational changes that occurred during extension at room temperature. EXPERIMENT ALThe UHMW-P4MlP used was a highly isotactic polymer with viscosity average MW of 1.5 x 10 6 • Solution-grown crystals (SGC) were isothermally precipitated from a 0.2 wt% solution in xylene kept at 50°C over 20 h. SGC mats were obtained by slowly filtering the crystal suspension followed by drying at 50°C.A two-stage drawing technique 5 · 8 was utilized for uniaxial drawing of SGC mats of UHMW-P4MlP. For the first-stage drawing, a solid-state coextrusion technique developed by Porter et al. 19 was used. For the secondstage, a conventional tensile drawing technique was used. Extrudates having an extrusion DR (EDR) of 6 prepared at 180cc were drawn at 180-200°C in an air oven equipped with a Tensilon tensile tester HTM-100. The total DR was defined by DR 1 = EDRxDR.179
The patient was a 15-month-old girl with Down's syndrome. She had a heart murmur on the first day after birth. The echocardiogram revealed that she had the tetralogy of Fallot (TOF) and mitral insufficiency (MI). She was observed because she had no heart failure or cyanosis. However, she developed heart failure with progressive MI. Then, she was admitted to our medical center for surgical treatment. During the operation, it was confirmed that the primary septum was intact and a large ventricular septal defect was located at the inlet to outlet portion with anterior malalignment. Each leaflet of the atrioventricular valve were attached to the same level and the ventricular septum was scooped out. TOF with endocardial cushion defect (ECD) without primary septal defect was diagnosed based on the operative findings. Surgical repair was performed through the right atrium and pulmonary artery. She was discharged 17 days after operation without any complications. This was a very rare combination of TOF with ECD without a primary septal defect. We discussed this rare condition with a review of the literature.
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