摘要:

AbstractThe conventional sheet metal forming technique known as Deep Drawing was used to investigate the formability of self‐reinforced thermoplastic sheets. The materials studied included uniaxially roll‐drawn oriented polypropylene (OPP), cross‐rolled biaxially oriented polypropylene (BOPP), and cross‐ply laminated OPP (LOPP). OPP exhibits poor room temperature formability as determined by its Limiting Drawing Ratio (LDR). Its formability is improved at elevated temperatures, but samples suffer from non‐uniform material flow, temperature sensitivity during forming, and a loss of mechanical properties due to the relaxation of orientation caused by the need for forming temperatures above the normal melting point. Although BOPP attains only moderate Improvements in mechanical properties compared to the machine direction of OPP, it exhibits much better room temperature formability. This difference in drawability between uniaxial and biaxial orientation states is a consequence of the difference in planar anisotropy between these two materials. LOPP has the potential of producing a material with superior performance compared to BOPP while still possessing the desirable formability of BOPP. The formed parts, however, undergo cracking in the outer ply parallel to the orientation direction as a consequence of the OPP small elongation to break in the transverse direction. In addition to forming problems, ordered polypropylene exhibits large shrinkage stresses at elevated temperatures. This may preclude its use in applications requiring a high level of dimensional stability. Classical plasticity theory for metals was appropriately modified to model the radial drawing stress for planar isotropic thermoplastic sheet

ISSN:0032-3888    

DOI:10.1002/pen.760301902

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA study of melting a polymer pellet immersed in a hot silicone oil bath was conducted. The temperature rise at the center of the pellet was recorded. This experiment simulates the conduction melting mechanism of polymer solid pieces mixed in the hot melt inside an extruder screw channel. The pellets immersed in the silicone oil melted quite slowly, taking around one minute to melt a spherical pellet of about 4.5 mm diameter. The heating time could be greatly decreased by stirring the silicone oil to increase the heat transfer from the silicone oil to the pellet. Analysis of the conduction melting mechanism showed that the size reduction of the solid would be most effective in decreasing the heating time.

ISSN:0032-3888    

DOI:10.1002/pen.760301903

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe extrusion of blown film polyethylene is a complex process characterized by a large number of interdependent process variables. In order to derive the set of process conditions necessary for a desired film solid state property, the processor normally utilizes a laborious trial‐and‐error method. In this work, a technique is described to establish more directly the set of extruder settings for producing film with an optimum value of a given property. Biaxial toughness was optimized in the present work, but the technique is applicable to any quantifiable film prope

ISSN:0032-3888    

DOI:10.1002/pen.760301904

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe theory of optimal control is used to analyze the performance of a batch PMMA (poly(methylmethacrylate)) polymerization reactor. Optimal dynamic profiles of temperature, initiator feed rate, and initiator concentration in the reactor are generated in order for specified conversion of monomer, number molecular weight, and polydispersity of the final product to be obtained. Based on tae physical limitations of the system, some restrictions are imposed to the control variable variations. The application of Pontryagin's Minimum Principle leads to a mixed initial/final value problem, which is solved by discretizing the control law in the state‐space, with the usage of a first order holder. A gradient method is used to minimize the Hamiltonian. The simulation results show that the gel‐effect equation and restrictions imposed on the system are of primary importance to the analysis of the reactor performa

ISSN:0032-3888    

DOI:10.1002/pen.760301905

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of cavity shapes, particularly the expansion and contraction angles, and the Theological properties of polymeric liquids on vortex formation in the cuter cavity of a dual‐cavity coat‐hanger die have been examined. For power‐law fluids, a vortex may appear in the expansion side of the outer cavity, and the size of the vortex is influenced by the expansion angle, the power‐law index, and the Reynolds number. Two viscoelastic fluids were used in the flow visualization experiment; for an aqueous polyacrylamide solution, a vortex may appear in the contraction side of the outer cavity and this vortex is influenced by the contraction angle and the fluid elasticity, but no vortex was observed for a Boge

ISSN:0032-3888    

DOI:10.1002/pen.760301906

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA double bubble tubular film process to produce biaxially oriented poly(p‐phenylene sulfide) (PPS) film is described. Operating windows were developed for stable operation of both the first and second bubbles. Films produced from single bubble tubular film extrusion were largely amorphous having only seven to nine percent crystallinity. Double bubble PPS tubular film had up to 20 percent crystallinity which was increased to 30 percent by further annealing. The first and second bubble films had surface roughness standard deviation heights of 0.01 to 0.04 μm. Orientation was characterized by birefringence and wide angle X‐ray diffraction pole figures of the 110 and 112 reflections. Biaxial orientation factors were computed. The double bubble films had higher Young's modulus and tensile strength but lower elongation to break than the single bubble films. Annealing further increases Young's modulus and tensile strength but decreases elongation to break. Double bubble and annealed films with roughly equal second bubble drawdown ratio and second blow up ratio tend to have balanced properties in the plane of the

ISSN:0032-3888    

DOI:10.1002/pen.760301907

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper presents an experimentally‐based analysis of the continuous filament regime of the melt‐blowing process. The experiments were performed with a versatile air‐polymer die, several die operating temperatures, and three different polymer feed resins. The measurements discern the effects upon the final fiber diameter of the following input parameters: die dimensions, die temperature, polymer feed resin, and both the air and polymer mass flow rates. An empirical model equation is developed which relates these input parameters to the final fiber diameter. In addition, the conditions which result in a transition of the filament from continuous (or stable) to discontinuous (or unstable) are quantified. The model equation and the transition or stability information are then used to predict the behavior of the melt‐blowing process for a wide range of case studies involving the input parameters noted above. The data and empirical model are of considerable utility for developing new die designs, for comparison with theoretical models, for predicting fiber stability, and for explaining the behavior of current industrial melt‐blowing

ISSN:0032-3888    

DOI:10.1002/pen.760301908

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe drawing characteristics of poly(ethylene terephthalate) (PET) yarns spun at 1000 and 3000 m/min and film cast at 10 m/min have been studied as functions of drawing temperature up to 200°C and drawing rate up to 50 min−1. The fiber spun at 1000 m/min and the film had very low degrees of pre‐orientation and flow‐drawing occurred 20 to 30°C above their respective glass transition temperatures, for which the drawing tension dropped to almost zero and the resulting drawn samples were found to be amorphous and isotropic. In these samples, flow‐drawing could be prevented if they were drawn at relatively low temperatures or high strain rates. The partially‐oriented yarn spun at 3000 m/min, which had higher pre‐orientation, did not exhibit flow‐drawing under the conditions used. Flow‐drawing apparently occurs due to molecular relaxation processes, which predominate if the drawing temperatures are high, the strain rates are low, and the PET precursor has a low degr

ISSN:0032-3888    

DOI:10.1002/pen.760301909

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractIn biaxial blown film technology of isotactic polypropylene, PP, the film tube drawn over the mandrel contains considerable morphological disorder. This disorder changes on further treatment to greater order i.e. the para‐crystallinity and the metastable crystal forms diminish as the monoclinic crystal form increases. The morphology change in PP was stimulated by further treatment of the drawn film tube over a mandrel corresponding to conditions of biaxial bubble forming. Analyses were by SEM, Wide‐angle X‐ray diffraction (reflection), DSC, and IR Dichroic measurements. A condenser quality PP,Mw/Mn= 7 and MFI = 3.7, shows a tensile yield at 110°C of 11.4 MPa. A tensile stress of 17.7 MPa was obtained at a blow up ratio of 7; the morphology of PP corresponds to deforming spherulites. The fraction of “perfectly” oriented molecul

ISSN:0032-3888    

DOI:10.1002/pen.760301910

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760301901

出版商:Society of Plastics Engineers    

年代:1990

数据来源: WILEY