摘要:

AbstractControl over final part thickness distributions in extrusion blow molding would be very useful in resin optimization. An on‐line measurement is essential for process monitoring and control of the part dimensions. Excessive resin usage results in material waste and increased cycle times because of increased cooling requirements. An inadequate thickness results in decreased mechanical strength, especially in regions along the part where large blow ratios or complex geometries exist. Neural networks are investigated as a method for the on‐line prediction of the final part distribution from the parison dimensions. The purpose of this work is to demonstrate the feasibility, for preliminary use, of neural networks for this application. The network inputs include the initial parison thickness and tempera‐ture profiles, the bottle mold geometry and a rheological parameter representative of the material. Varying blow‐up ratios are obtained from the bottle mold geome‐try. The network accesses data from a pool of eighty data sets for the training sequence. The data sets are broadly distributed with regard to the operating conditions, so as to give the network a wide range of applicability. The simulations are performed on data sets not present in the access pool used for

ISSN:0032-3888    

DOI:10.1002/pen.760331102

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThe packing stage starts at the end of mold filling. During this stage, additional material is forced into the mold to compensate for the shrinkage during subse‐quent cooling. Underpacking results in molded parts with dimensional variation. Overpacking causes flash at the parting lines, stick during ejection, and excess residual stresses resulting in warpage. The packing stage is thus extremely important in the determination of the final quality of the product. Despite its importance, analysis of the packing stage has been relatively ignored, particularly the viscoelastic effect. In this work, the analysis of the isothermal packing stage is presented for a Maxwell fluid. A set of governing equations is derived for a two‐dimensional mold and solved using the Galerkin finite element method. In addition to the distribution of velocity and pressure, the model predicts the stresses in the planar direction, which could be used for subsequent calculation of the residual stres

ISSN:0032-3888    

DOI:10.1002/pen.760331103

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThe objective this work was to determine the effects of selected polyester catalysts on the reaction of a polyester with epoxy functional polymers. Polyesters containing various catalyst metals were melt blended with either an ethylene‐co‐glycidyl methacrylate or a styrene‐co‐glycidyl methacrylate copolymer. The viscosities of the blends were monitored as a function of mixing time using torque rheometry. In addition, the molecular weight distributions of selected samples were analyzed using gel permeation chromatography. Both the torque rheometry and the gel permeation chromatography results indicate that the polyester reacts with epoxy functional polymers. This reaction occurs under conditions and at processing times which are readily obtainable in conventional melt processing equipment. Furthermore, the reaction kinetics of polyesters with glycidyl methacrylate copolymers are dramatically affected by the nature of the catalyst system used to prepare the polyester. Under the conditions used, antimony catalysts are particularly effective at promoting the reaction between polyesters and the epoxy functionality and the activity of the catalysts studied appears to decrease in the following order: antimony>gallium>tin ≃ titanium>germanium. Manipulation of the polyester catalyst system may offer a method to control the extent of reaction obtained in reactive processing of polyesters with epoxy functional

ISSN:0032-3888    

DOI:10.1002/pen.760331104

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractBlends of polybutene‐ 1 (PB‐1) and polypropylene (PP) have been injection and compression molded. A synergism appears in the ultimate elongation and the tensile strength for the injection moldings. The maximum point of the synergism at the composition of 25 wt% PB‐1 shifts to 50 wt% PB‐1 after annealing at 145° C for 1 h. A linear relation and negative deviation from the additivity rule for these two properties are observed for the compression moldings with quick cooling and slow cooling, respectively. Thermal analysis, polarized optical microscopy, and scanning electron microscopy (SEM) are used to study the occurrence of the synergism. The mutual interference between the two components on the crystal formation and the plasticization effect of PB‐ 1 on PP result in the synergism. An increased phase separation probably occurs during the compression molding with slow cooling. So, the blends compression‐molded with slow cooling having a higher amount of PP have brittle breaks, simila

ISSN:0032-3888    

DOI:10.1002/pen.760331105

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this paper, a model for the conveying of solid polymer in the feeding zone of intermeshing co‐rotating twin screw extruders is proposed. The theoretical model uses an approach that is similar to that commonly used in single screw extruders; however, it takes into account the particular geometry of the screw channel, the partially filled channel, and the special configuration of the two self‐wiping screws. The model thus considers two conveying mechanisms: the first one in the channel, which is analyzed in terms of polymer‐metal friction, and the second one, which is mainly an axial transport in the intermeshing zone. The theoretical predictions of the model are compared with the experimental results obtained on a laboratory extruder with a polymer in powder form, and satisfactory agreement is observed. The model enables the prediction of the evolution of the filling of the screws towards the geometry and the operating conditions. This is an important key to analyzing the thermal aspects in this zone, which can lead to a prediction of the melting capacity of the extruder. Indeed, the filling of the feeding zone defines the heat transport that occurs between the hot barrel and the solid po

ISSN:0032-3888    

DOI:10.1002/pen.760331106

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractThe flow kinematics of power‐law fluids in fishtail dies is studied. A general isothermal three‐dimensional finite element code developed by the authors is used for the flow analysis purpose. The basic geometry of the fishtail die is defined by simple super‐elliptical curves, which allows a smooth transition from a circle to a slit. The three‐dimensional path line and the residence time distribution (RTD) are calculated from the velocity field obtained from the finite element solution of the conservation equations. The effects of the rheological properties and the die geometry on the path line pattern and the residence time distribution are investigated. The results indicate that as both the length of the transition zone and the fishtail angle increases, the residence time distribution becomes more uniform. However, the power‐law index does not affect the residence time distribution sign

ISSN:0032-3888    

DOI:10.1002/pen.760331107

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

摘要:

AbstractA numerical model of the reaction injection molding process was developed to test front shape and flow approximations employed in previous models. The model was two‐dimensional and simulated the flow, reaction, and heat transfer in the typically long axial dimension and the typically small thickness dimension of a mold. The filling front shape and the velocity profiles in the filling fluid were determined by numerical solution of the momentum equation with the appropriate stress boundary conditions using the method of Patankar (1980). The predicted temperature and conversion results agreed with calculations assuming that the front was flat perpendicular to the flow and that a parabolic velocity profile existed behind the fountain flow region at the front. Thus, simple assumptions about front shape and velocity in the thin dimension of a reaction injection mold can be employed without significant loss of accuracy in modeling reaction injection moldin

ISSN:0032-3888    

DOI:10.1002/pen.760331108

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760331101

出版商:Society of Plastics Engineers    

年代:1993

数据来源: WILEY