摘要:

AbstractMorphological studies have been carried out on a thermotropic liquid crystalline copolyester based on poly(ethylene terephthalate) (PET) and para hydroxybenzoate (PHB) that has been subjected to different types of flow histories. Wide angle X‐ray scattering investigations and chemical etching (n‐propylamine is the etchant) in conjunction with electron microscopy studies conducted on end gated injection molded plaques of the 60 percent PHB and 80 percent PHB copolyesters indicate that a highly oriented skin region and a less oriented core region is present. Chemical etching studies performed on microtomed layers of end gated and center gated plaques show that the etching is less pronounced in the skin region and is more pronounced in the core. The microtomed layers of the end gated injection molded plaques when analyzed by ESCA indicate the presence of a “PHB rich” skin region and a “PET” rich core region. Biaxial orientation, as denoted by WAXS measurements, is observed when the 60 percent PHB copolyester is squeezed between lubricated para

ISSN:0032-3888    

DOI:10.1002/pen.760250702

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractMolecular weight determination in poly(butylene terephthalate) (PBT) is hindered by the inherent difficulties of intrinsic viscosity (IV) determination in general and toxic solvents used in particular. In any case molecular weight does not include information as to the identity of end‐groups in the polymer chain. This report shows how the Fourier Transform Infrared method of Ward for PET can be adapted for alcoholic and acidic end‐group determinations in poly(butylene terephthalate) (PBT) and consequently for the number averaged molecular weight of PBT. A statistical analysis was performed on comparative IR‐ and IV‐derived molecular weight which revealed a correlation coefficient of better than 90 percent. The method is, therefore, recommended as an alternative to the standard IV technique, especially if simultaneous end‐group analyses are also

ISSN:0032-3888    

DOI:10.1002/pen.760250703

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractDumb‐bell specimens and rectangular boxes were used to study phase separation effects occurring in injection molding of glass‐bead and glass‐fiber‐filled thermoplastics. The separation effects were more pronounced with beads than with fibers and they increase with increasing bead diameter. The filler distribution is further influenced by mold geometry, filler concentration, matrix material, and processing conditions. If the use of fillers, which promote inhomogeneity, is unavoidable it is possible to improve the distribution of the rigid phase by a favorable choice of injection speed and melt temperature. With the theories available at present a qualitative interpretation of the origin of the observed separation phenomena is f

ISSN:0032-3888    

DOI:10.1002/pen.760250704

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractTest results are presented for a matrix type phase change thermal storage tile module with no surface covering, intended to transfer heat directly to and from room air at small temperature differences. Heat is stored and released by melting and freezing mixtures of fatty acids, which constitute up to half the weight of the tile. The polymeric matrices tested were powders or granules of poly(vinyl chloride) (PVC), poly (vinyl acetate) (PVAc), poly(vinyl alcohol) (PVA), vinyl acetate‐vinyl chloride copolymer (VAc‐VC), and high density polyethylene (HDPE). The tiles keep their shape and dimensions without any weeping of liquid fatty acid, up to 37 or 51°C, depending on their composition. In the case of PVC and PVA, infrared spectra and differential scanning calorimetry indicate interactions between the polymer and the fatty acids, which may increase the surface tension and allow larger matrix pores before weeping begins. Some of the tiles were reinforced with glass fibers, and others with cellulose fibers. The best mechanical properties were obtained with 5 percent of long (85 to110 mm) glass fibers. Paraffin chloride and antimony trioxide served as satisfactory fire retard

ISSN:0032-3888    

DOI:10.1002/pen.760250705

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA new comprehensive mathematical model has been developed for the melting zone of a single‐screw extruder processing a (semi) crystalline polymer. It has been demonstrated that the cross‐channel flow plays an important role in the melting mechanism. When incorporated into a non‐Newtonian fluid model combined with the rigid solid bed concept, the present analysis leads to significantly improved predictions of the melting rate and axial pressure profile. This conclusion is supported by experimental data and by a quantitative examination of the flow and thermal patterns prevailing in the melting zone.It is suggested that under the constraints of the commonly accepted assumptions concerning the physico‐chemical properties of the polymeric system the transport analysis of the Maddock mechanism is virtually c

ISSN:0032-3888    

DOI:10.1002/pen.760250706

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractSorption isotherms show that epoxide prepolymers sorb water in increasing amounts as the temperature decreases and the water vapor concentration increases. BelowTgthe behavior is typical of a Fickian transport combined with a relaxation process. Diffusion coefficients as function of sorption rates provide temperature shift factors from which the activation energy for diffusion is 35.3 KJ/mol. Combined effect of temperature and water concentration is described by a second order polynomial.

ISSN:0032-3888    

DOI:10.1002/pen.760250707

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe kinetics of the activated anionic polymerization of caprolactam to nylon 6 was studied by the adiabatic temperature rise technique. This allowed very rapid reaction conditions to be studied. The polymerization was activated by diisocyanate and catalyzed by sodium caprolactamate, produced in situ by the addition of sodium hydride. The temperature rise measurements were used to generate Arrhenius curves of the rate data. Several isocyanates were investigated, all giving similar rate curves. The reaction rate was reduced, however, when the activator concentration exceeded the catalyst concentration. To model the actual rapid molding conditions, timevs. temperature reaction profiles were measured for thin plaque castings. In these reaction profiles, two successive exotherms were observed. The first was the polymerization exotherm, and the second was determined to be the crystallization peak. This second exotherm allowed the direct observation of crystallization times within the closed molds. The crystallization times were found to depend strongly on the mold temperature and to a lesser extent on the monomer temperature. The crystallization times were minimized at a 150°C mold temperature. At higher temperatures, the crystallization rate was significantly slower, while at lower temperatures, the slow rate of polymer formation delayed the onset of crystallization. This study has demonstrated the value of using temperature monitoring as a means of studying the polymerization and crystallization behavior of nylon

ISSN:0032-3888    

DOI:10.1002/pen.760250708

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractOrientation‐induced crystallization of crystallizable polymer melts can occur, under certain conditions, during flow through converging channels. Attempts have been made to achieve this phenomenon in a two‐phase system, i.e., during simultaneous extrusion of a continuous concentric core of polypropylene within a polystyrene matrix through a conical duct. On one occasion, using Carlona P SY6100 (MFI = 11.0) with Hostyren N2000‐V‐01 (MFI = 25.0), a highly oriented polypropylene thread with a modulus of 14.6 GPa and a melting point of 178°C was extruded at a die temperature of approximately 170°C and a pressure lower than 40 MPa. It is, in principle, possible to form highly oriented, fiber‐like structures as reinforcing elements in a pol

ISSN:0032-3888    

DOI:10.1002/pen.760250709

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractFlame retardation of polypropylene was accomplished by blending with antimony compounds (Sb2O3and SbPO4) in conjunction with polyvinyl chloride (PVC) or ferric oxide. The compatibility and dispersion of antimony compounds in the polymer matrix was enhanced by using silane coupling agents, viz., vinyltriethoxysilane (A‐151) and γ‐aminopropyltriethoxysilane (A‐1100). Rheological properties of filled polypropylene were studied in the temperature range 180 to 220°C at shear rates of 29.5 to 119.5 sec−1. An increase in the melt viscosity was found in the filled polypropylene as compared to virgin polymer. Silanation of antimony compounds also influenced the melt rheology of flame retardant polypropylene. Incorporation of 6 phr Sb2O3and 19 phr PVC raised the oxygen index of polypropylene to 22.9 and this sample was found to be self extinguishing in 65 s with a burning rate of 0.06 mm/s as compared to 1.1 mm/s for unfilled polypropylene. Though silanation of antimony compounds slightly reduced the oxygen index of flame retardant polypropylene, yield strain and flexural rigidity of injection molded samples was improved over unsilanated flame retardan

ISSN:0032-3888    

DOI:10.1002/pen.760250710

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760250701

出版商:Society of Plastics Engineers, Inc.    

年代:1985

数据来源: WILEY