摘要:

AbstractA new method to obtain a rubber‐modified polyamide 6 (PA6) directly during the polymerization of the caprolactam (CL) is described. Binary and ternary blends containing ethylene‐propylene random copolymers (EPM) and/or a fictionalized EPM rubber (EPM‐g‐SA) were prepared and their morphology as well as their mechanical properties were investigated as function of composition and reaction conditions. It was found that the morphology of the blends is strongly dependent on the method of preparation. More complex structures are observed in blends obtained with the “Solution” preparation. For a better resolution of the morphology, the smooth ultramicrotomed surfaces were exposed to boiling xylene before SEM (scanning electron microscopy) examination. The rubbery phases are selectively dissolved whereas the PA6 matrix is left. The tensile mechanical properties and the Izod impact behavior are related to the mode and state of dispersion of the rubbery components. The impact properties of ternary PA6/EPM/EPMg‐SA (80/18/2) and (80/15/5) blends, prepared during the CL polymerization are comparable to those of similar blends obtained by usual melt mixi

ISSN:0032-3888    

DOI:10.1002/pen.760250402

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760250403

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe embrittlement of ductile polymers resulting from outdoor weathering or aging or from the application of brittle surface coatings is explained using fracture mechanics principles. It is shown that in order for surface embrittlement to occur, the brittle surface should have a dynamic stress intensity factor at the brittle/ductile interface that exceeds the arrest toughness of the ductile polymer. This phenomenon is modeled using duplex tensile specimens fabricated from poly(methylmethacrylate) (brittle layer) and polycarbonate (ductile substrate) as well as from styrene‐acrylonitrile and acrylonitrile‐butadiene‐styrene copol

ISSN:0032-3888    

DOI:10.1002/pen.760250404

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractMathematical modeling and experimental studies of the freeradical polymerization of methylmethacrylate in tubular reactors have been performed to ascertain the operating constraints, reactor behavior, and product quality of this process. This paper focuses on reactions at a temperature below the glass transition of poly(methyl methacrylate). This class of experiments is here referred to as low‐temperature runs, in contrast to above‐Tgpolymerization. Reactor temperature and conversion histories of these low‐temperature experiments are successfully described by a rheokinetic model, incorporating both detailed considerations of velocity profile development in the reactor and conversion‐dependent kinetics. The limitations of this process are discussed in light of the complex fluid flow and heat transfer problems encountered in the

ISSN:0032-3888    

DOI:10.1002/pen.760250405

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractFree‐radical polymerization of methyl methacrylate in a tubular reactor has been conducted at above‐Tgtemperatures. A salient feature of these experiments is the very efficient control of reactor temperature by vapor‐liquid equilibrium of the polymerizing mixtureviamonomer evaporation. The system pressure thus provides a powerful control variable, restricting the temperature in the entire reactor by changing the monomer evaporation rate. In the range of our experimental conditions, the temperature and pressure in the reactor follow the Antoine equation closely. High temperature runs also reduce the length requirement of the reactor. However, molecular weight averages of the products are not impressive, unless slow‐burning initiators are used. Modeling of above‐Tgreactions has been attempted at two‐levels of sophistication. A plug‐flow model gives predictions in good agreement with our experimental temperatures and conversion data. The predicted molecular weights are also consistent with the experimentally observed values. However, the more elaborate rheokinctic model suggests that the superficial agreement between model and experiment is due to initiator burn‐out, which limits the final conversion to within 40 percent. The liquid layer next to the reactor wall can never be so viscous as to form a stagnant deposit, due to this conversion limitation. The velocity profiles are thus not very much distorted, and a plug‐flow model is adequate. With a slow‐burning initiator and a sufficiently long reactor, skewing of velocity profile and reactor channeling will eventually emerge. Hence, the rheokinetic model must be evoked to model the system un

ISSN:0032-3888    

DOI:10.1002/pen.760250406

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractCopoly(carbonate imides) with varying amounts of carbonate in the backbone were prepared by reacting 4,4′‐diaminodiphenyl carbonate and 4,4′‐diaminodiphenyl ether with benzophenonetetracarboxylic acid dianhydride in dimethylacetamide at room temperature. Homopolymers of the two diamines as well as of 3,4′‐ and 3,3′‐diaminodiphenyl carbonate were prepared in a similar procedure and their properties compared with those of

ISSN:0032-3888    

DOI:10.1002/pen.760250407

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe deformation behavior that results from falling weight impact testing with flat‐headed darts is analyzed in terms of elasticity and plasticity. From a comparison of the time and temperature dependence of the yield stress that is observed during a falling weight test with the same dependences of the yield stress during simple shear tests, it is concluded that the use of flat‐headed darts results in strong shear loading. Consequently most of the plastic deformation takes place by shear flow. Of practical interest is that this leads to a simple dependence of the yield stress during the impact test and the impact energy on the plate thickness. Furthermore, for a number of cases this result allows a direct conversion of temperature effects to time effects. In practice this means that it is possible to simulate the impact behavior at very high impact rates simply by performing impact tests at lower temperatu

ISSN:0032-3888    

DOI:10.1002/pen.760250408

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760250401

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY