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  • 1995-1999  (8)
  • Polymer and Materials Science  (7)
  • Chemical Engineering  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Influence of processing on quality of injection-compression-molded disks (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1206-1212 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A modified injection molding machine with a compression mechanism, and a mold with a movable wall and shut-off mechanism, were used to investigate the effects of processing parameters on the quality of injection-compression-molded polystyrene disks. The compression start-up time, compression force, melt temperature, and part thickness were selected processing parameters. The disk moldings were evaluated based on dimensional accuracy and birefringence. It is found that the compression start-up time affects packing time, and thus greatly affects the residual orientation. If the transition from packing to compression could start before peak cavity pressure, disks with low residual orientation could be obtained. High compression force improves part quality and reduces thickness. Since both compression-induced reduction and cooling-induced shrinkage are involved, the effects of temperature and thickness are not as straightforward as the trends in conventional injection molding.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760351503
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation of gradient-index (GRIN) polymer fibers for imaging applications (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 1379-1383 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A closed extrusion process combined with a core-shell separation die design is developed in this study for preparing gradient index (GRIN) polymer fibers with a quadratic distribution of the refractive index. The material system used in this investigation is methyl methacrylate (MMA, n = 1.49) and benzyl methacrylate (BzMA, n = 1.568). The refractive index differences between the center and the periphery (Δn) of the prepared polymer fibers increase from 0.0115 to 0.020 when BzMA in the reactant mixtures increases from 17 to 28%. This finding would suggest that increasing the high refractive index monomer in the reactant mixture increased Δn. The Δn values decrease from 0.018 to 0.0135 when the diffusion zone temperature increases from 70 to 90°C. The diffusion rates of the monomers increase with the temperature, thereby causing BzMA and MMA to distribute more uniformly at a higher temperature than at a lower one. This uniform distribution leads to the decrease of Δn with an increasing temperature. The prepared GRIN polymer fibers have potential applications as imaging lenses for scanners, fax machines, and copiers. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Solvent effect on the action of ethylene-vinyl acetate copolymer pour point depressant in waxy solutions (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 1575-1578 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The flowability and thermal behavior of waxy solutions with and without an ethylene-vinyl acetate copolymer (EVA) have been studied. The drastic changings of pour point depression (ΔTpp) and the crystallization in four waxy solutions were observed. These changes were linear with the U-interaction parameters between EVA and wax in different solvents, suggesting that the efficiency of EVA pour point depressent depends on its compatibility with wax, which is affected by solvent. © 1996 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Studies on the preparation of gradient-index polymeric rods by interfacial-gel copolymerization (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 1179-1182 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070560918
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Experimental study on the effects of adding compression to injection molding process (1995)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 14 (1995), S. 15-24 
    Details
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The quality of thermoplastic injection molded parts is mainly determined during the post-filling process. To enhance the control capacity over the post-filling process, adding compression to the conventional injection molding process opens a flexible channel for pressure control. This study experimentally investigated the effects of adding compression on the thermal-mechanical history and on the quality of molded parts. An instrumented molding machine with a compression mechanism was used. Molds for rectangular plate and circular disk were equipped with a movable cavity wall and shut-off mechanism. The thermomechanical history during the injection compression molding was identified with the aid of a PC-based data acquisition system. The quality of parts was evaluated by flatness, deviation from mold dimensions, and birefringence. It has been found that the thermomechanical history of the melt under injection compression molding follows a quadrilateral-shaped path over the p-v-T diagram. The control capacity over post-filling is enhanced. It thus can produce parts with better dimensional control with less frozen-in orientation than those from conventional injection molding. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adv.1995.060140102
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Development of moldability diagrams for gas-assisted injection molding (1995)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 14 (1995), S. 197-205 
    Details
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Gas-assisted injection molding (GAIM) has proven itself to be a breakthrough in molding technology. However, the process involves additional gas-related parameters to control the molding process. The interaction between melt and gas makes the gas-assisted process complicated. To make satisfactory parts, the material, the mold, and process parameters determine the “moldability” of a specific system. The concept of “molding areas” on the critical plane can be extended from thermoplastic injection molding to GAIM. This research is devoted to the development of a proper moldability diagram for GAIM. The first part of this study employs gas-related parameters to define the molding area. The second part is devoted to identifying the relative importance of process parameters. The results show that melt temperature and short shot are the two factors which most significantly affect the GAIM process. The third part of this study defines the moldability based on critical parameters. The application of the moldability concept is demonstrated in selecting the optimum rib geometry. These moldability studies are intended to give first guidelines for system optimization. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adv.1995.060140303
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of cooling time and mold temperature on quality of moldings with precision contour (1996)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 15 (1996), S. 289-295 
    Details
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Injection molding is now used to mold plastic parts with precision contours such as lenses. Cooling conditions have critical effects on the quality and productivity of such precision parts. This article is devoted to investigate the effects of mold temperature and cooling time on quality. A two-cavity mold for molding convex lenses with square-looped cooling channels was used. Samples molded with different mold temperatures and cooling times were collected, and their contour conformity to those of the cavity was evaluated. Contour errors were defined. The correlation between mold temperature and cooling time and contour errors was analyzed. It has been found that for a given mold temperature, two critical cooling times can be defined at which the thermal and rigidity states pass through a transition. Most dramatic improvements in part conformity occur around such critical points. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 8
    Electronic Resource
    Electronic Resource
    Experimental study on injection compression molding of cylindrical parts (1996)
    Hoboken, NJ : Wiley-Blackwell
    Advances in Polymer Technology 15 (1996), S. 205-213 
    Details
    ISSN: 0730-6679
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The control capacity and flexibility of the injection compression molding technique (ICM) is significantly greater than that for conventional injection molding. It thus has potential to produce parts with better dimensional control. This article is devoted to studying the technological application of ICM on the precision molding of cylindrical parts. A modified injection molding machine incorporating a compression mechanism, and a mold with movable wall and shut-off mechanism, are used to investigate the effects of packing and compression on quality in injection-compression-molded polystyrene hollow cylinders. The quality of injection-compression-molded parts is evaluated using roundness, straightness, and birefringence. It has been found that packing is the most effective densification mechanism for cylindrical parts with ring gates. Without proper packing, compression may collapse the frozen layer and degrade the part quality. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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