摘要:

AbstractGraft copolymers and coionomeric mixtures produced by mixing a phenoxy polymer (polyhydroxyether of bisphenol A) respectively with ethylene–propylene copolymers, containing grafted maleic anhydride groups (EP‐g‐MA), and the sodium ionomers of the terpolymers of ethylene, an alkyl acrylate and a carboxylic acid, the ionomeric character of which being enhanced by the addition of either sodium benzoate (weak base) or sodium ethoxide (strong base), were used as compatibilizers for blends of PET and HDPE in different ratios and with varied molecular weight of the HDPE component. The preparation of the compatibilizer and the production of the blends were carried out on a twin‐screw extruder. Both types of compatibilizers acted as effective surfactants for the dispersion of the two polymers, at all weight ratios, and the blends exhibited a substantial increase in melt viscosity as a result of the addition of the compatibilizer. Only the coionomeric compatibilizers, however, produced substantial improvements in both tensile strength and elongation at break, irrespective of the ratio of the two polymers in the blends. This was attributed to the strong nucleating effects on the crystallization of the polymer components and to a strong interfacial adhesion between the two polymer phases. © 1994 John Wiley&S

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractCavity pressure is an important process parameter for injection molding control. However, the nonlinear and time‐varying behavior of cavity pressure cause some difficulties in implementing a control system based on commonly used linear, time‐invariant design strategies. In this work, the nonlinearity and time‐varying characteristics of cavity pressure are examined for the mold filling phase. A self‐tuning controller has been developed, implemented, and tested for both regulating and tracking purposes over a wide range of conditions. It is found that the proposed control system can automatically adapt itself to different operating conditions, yielding quite accurate control. © 1994 John Wiley&S

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe advantages of the Generalized Eulerian–Lagrangian (GEL) formulations in modeling and numerical solution of unsteady flow of fiber suspensions are discussed. This formulation offers the flexibility of selectively applying an Eulerian (Spatial), a Lagrangian (Material), and any combination of these two frames of reference in the same computational domain. This flexibility offered by the GEL formulation is exploited to exactly determine the shape and location of the free surfaces and moving boundaries in the numerical simulation of various manufacturing processes. The application of the GEL formulation to the solution for the flow field and fiber orientation in the unsteady flows of dilute and semiconcentrated fiber suspensions are presented. The flow field and fiber orientation predicted by this method agree well with the available theoretical and experimental results. © 1994 John Wiley&Sons, I

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn single‐screw extrusion it is not unusual to encounter large temperature variations within the screw channel, especially at high pumping rates. These temperature variations result in nonhomogeneities that affect the quality of the final product. Although there have been numerous efforts aiming at the simulation of the flow in the channel of a single‐screw extruder, and the prediction of important flow quantities, there is hardly any published work in which the temperature distribution in the screw channel was actually measured. Such measurements, if available, would provide data by which computer simulations could be validated. In the present study, a fast‐response, cam‐driven thermocouple system was developed and used to measure the radial temperature distribution in the screw channel. The measurements are carried out on a well‐controlled, custom‐built, single‐screw extruder. Temperature profiles in the centerline of the screw channel were obtained for various operating conditions of the machine. The data obtained revealed interesting features of the flow as well as the dominant heat transfer mechanisms. The system as developed here can be improved to accommodate larger industrial applications. © 1994 John W

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractRubber modified prepolymers were synthetized through a nucleophilic addition of diamines to aromatic bismaleimides, using N,N′bismaleimido‐4‐4′diphenylmethane (BMI), 1,4‐piperazine (PyP), and an amino‐terminated polydimethylsiloxane elastomer (PDMS). Thermal stability was investigated by thermogravimetric analysis (TGA) in order to elucidate the influence of diamines. Physical and rheological changes during the curing process were monitored by differential scanning calorimetry (DSC) and dynamic mechanical tests (DMA). The degree of cross‐linking of the sample with PDMS was higher than that of the sample without PDMS. This effect might be due to a larger chain mobility provided by the rubber during the cure. © 1994 John W

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe changes in the physical properties of three different commercial silicone sealants used in structural glazing applications were monitored as a function of various aging factors. The variables included, simultaneous exposure to ozone and moisture in which the pH of the moisture was maintained at discrete levels of 3 and 11. The extremes of the pH range represent recorded values for acid rain (pH = 3) and basic cleaning solutions (pH = 11), respectively. A second portion of the study involved studying the effect of loading on the sealant performance. The experimental coupons were cut from cast sheets of DC‐790, DC‐995, and DC‐983. An Instron tester was used to measure the changes in the engineering properties such as Young's modulus, relaxation time, and ultimate tensile stress of the test samples as a function of time of exposure to the different variables. Unexposed samples, kept at ambient laboratory conditions, were used as the control. Results of these tests indicate that the Young's modulus of the samples decreases during an initial period as a result of their exposure. After this initial decrease the sample moduli showed a steady increase with time. Surface cracking was observed during the initial period, even though the moduli continued to increase. Moreover, the acid and ozone appear to act synergistically in the deterioration of the sealant. Samples exposed to the higher pH level did not show this kind of behavior. The effect of tensile loading on the sealant was significant only for DC‐983, the high modulus formulation. This was perhaps because of the creation of high stress centers. The medium modulus material exhibited good resistance to the synergistic effects causing deterioration. Ozone resulted in discoloration, softening, and change in structure in the low modulus formulation. Although the ozone did not react aggressively with silicone, its slow attack or degradation should still be of concern. In spite of the use of inhibitors, severe and acute cracks appeared on the surface of the rubber material at angles of ninety degrees across the line of tension. It is hoped that these accelerated test results can lead to more informed decisions concerning silicone sealant life following their exposure to ozone and acid precipitation. © 1994 John Wiley&S

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis article is a review of developments published in the open literature during 1992 on subjects related to the injection molding of fiber reinforced thermoplastics. Topics discussed include high performance polymers, reinforcements, fiber–matrix adhesion, composite properties, data bases, factors involved in injection molding, product design, mold design and manufacture, product manufacture, and applications of fiber reinforced thermoplastic composites. The intent was to include information pertinent to improvements in the engineering, fabrication, and use of these materials. © 1994 John Wiley&Sons, I

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1994.060130208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY