ISSN:0730-6679    

DOI:10.1002/adv.1983.060030301

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe mechanics of energy conversion in an extruder is extremely complex. Generally speaking, the extrusion process utilizes two sources of energy: (1) mechanical energy which is imparted to the polymer by the rotational motion of the screw, and (2) thermal energy (heat) which flows between the polymer and surfaces of the barrel by conduction and convection.Modern extrusion processes are relatively wasteful of energy because, operating at high speeds, they often dissipate an excess of mechanical energy as heat that has to be transferred (by barrel cooling) from the polymer and discharged into the surroundings as waste energy.Until recently, little attention was paid to this wasted energy. Energy was relatively cheap and the process economics favored was high speed operation despite its associated energy wastage. With the recent introduction of gear pumps for extruders, low pressure extruder operation becomes a possibility. It appears that this type of operation may result in a significant improvement in energy efficiency.This paper attempts to analyze the energy economy of extrusion processes and to understand where and how energy savings can result from the use of gear pumps. It shows that if substantial energy savings are to result from the use of gear pumps, these savings will come about not because of increased pumping efficiencies, but because low pressure operation has made a fundamental change in the energy conversion processes occurring in the screw.

ISSN:0730-6679    

DOI:10.1002/adv.1983.060030302

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

年代:1983

数据来源: WILEY

摘要:

AbstractIn single screw melt extruders there is a continuous flow of polymer melt over the flight clearance. The melt flowing over the clearance experiences high shear rate and may also experience very high temperature. This, in turn, may affect polymer structure and properties. The melt that flows over the flight is mixed with the bulk of the melt flowing in the channel. In the extrudate there are fluid elements that have not passed over the flights and there are fluid elements that passed over the flight once, twice, or many times. In this paper, a theoretical model is proposed for calculating the number of pass distribution function of a melt stream emerging from a melt extruder.

ISSN:0730-6679    

DOI:10.1002/adv.1983.060030303

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

年代:1983

数据来源: WILEY

摘要:

AbstractHigh molecular weight polymers have become well established as packaging or container materials. Unlike metallic and ceramic barriers, however, polymer films are known for their semipermeable nature; that is, they permit small gaseous and vapor molecules to migrate through their atomic/molecular structures. Since the intrusion of oxygen/water from the surrounding air or the loss of water/carbon dioxide from a packaged product can be detrimental to the shelf life of the product, the steady state transmission rate of a polymer film has become an important property characteristic of polymers to be used for packaging.An attempt has been made in this study to review the transmission data of commercially available polymer films. The three molecular species O2, CO2, and H2O were of particular interest. Since these permeability data vary over five orders of magnitude, several log‐log plots were constructed in order to assist decision making in film selections. Data for 34 different polymers are given. The effects of order or crystallinity, the presence of plasticizers, and the effects of laminated layering are discernible. It is the latter modification (laminating) that possesses demonstrable potential for improving the barrier properties of polymer films used for packaging purpose

ISSN:0730-6679    

DOI:10.1002/adv.1983.060030304

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

年代:1983

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1983.060030305

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe long‐term behavior of a glass mat‐reinforced polypropylene has been characterized by accelerated flexural creep tests on samples of the laminate. Considerable data were collected for stress levels ranging from 200 to 7500 psi at six temperatures from room temperature to 140 °C. The material was found to behave in accordance with the linear theory of viscoelasticity except at the longer times where the creep rate increases dramatically and the specimen ruptures. The stress and temperature dependence of this “terminal creep” zone was treated by means of a slightly modified version of Schapery's thermodynamic theory of nonlinear viscoelasticity, which involves the superposition of double logarithmic plots of creep compliance versus time. The stress and temperature dependence of both the free energy function and the entropy production emerge from this treatment. A comparison of nonisothermal creep data with a prediction from the isothermal master curve is marginally acceptable. A statistical synthesis of the data discloses that the incidence of terminal creep is log‐normally distributed. Moreover, the standard deviation associated with the distribution is independent of temperature. It is therefore possible to assess the probability of failure for any constant stress at any constant t

ISSN:0730-6679    

DOI:10.1002/adv.1983.060030306

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

年代:1983

数据来源: WILEY

摘要:

AbstractLinear low density polyethylene (LLDPE) has been produced for about 20 years; however, the commerical potential of the product was not fully appreciated until Union Carbide developed its vapor phase process. Now many companies throughout the world are producing LLDPE. The following paper reviews some of the different processes to produce LLDPE.

ISSN:0730-6679    

DOI:10.1002/adv.1983.060030307

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe outlook for rubber processing equipment in the 1980s is good, as is the future for rubber compounding processing. A significant number of changes have occurred in the rubber industry and, subsequently, in rubber processing equipment. Compound processing machinery reflects the awareness of energy costs and the need for conservation. There is a slow but growing trend toward continuous processing. The elastomers are more readily available in particle form. The machinery reflects a far greater understanding of the nature of the material to be processed, and the need for the processing equipment to be able to operate with this in mind. The processing machinery of the 1980s is not necessarily bigger, but it is better because it is smarter. The old magic and mysterious art of rubber compounding and compound processing is being completely replaced by machinery systems that scientifically process rubber compounds.

ISSN:0730-6679    

DOI:10.1002/adv.1983.060030308

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

年代:1983

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1983.060030309

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

年代:1983

数据来源: WILEY