摘要:

AbstractAn experimental program was carried out to study the dynamics of parison swell and development in extrusion‐blow molding. Two commercial blow molding grade polyethylene resins were employed in conjunction with an Impco, Model A13‐R12 reciprocating screw blow molding machine equipped with a cylindrical bottle mold. Parison weight swell was measured with the aid of a parison pinch‐off mold. In order to obtain more reliable and useful information regarding diameter and thickness swell of the parison and the dynamics of parison formation and development, high speed cinematography was employed. Data obtained by this technique are more reliable than results obtained with the pinch‐off mold alone. They also give further insight into the phenomena of swell, sag, and parison spring back or r

ISSN:0032-3888    

DOI:10.1002/pen.760201202

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe rheology of polystyrene powder beds was examined by two kinds of experiments. From stress relaxation measurements during powder compaction, it was found that relaxation at the shorter times could be attributed to sliding between particles. This is followed by a relaxation attributed to the deformation of the polystyrene particles themselves. From dynamic mechanical measurements, an increase was found in the value of vibrational absorption coefficient (Q−1value) at a temperature below that of the main relaxation dispersion of bulk polystyrene, attributed to the slipping around tight particle junctions. These phenomena appear characteristic of powder‐like materi

ISSN:0032-3888    

DOI:10.1002/pen.760201203

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractMelt viscosity and dynamic‐mechanical data are reported for samples obtained by anionic polymerization of caprolactam, in the presence of LiCl. The full body of results is essentially in line with those previously reported relative to mixtures of inorganic salts and commercial nylon 6, In particular a drastic‐decrease of the melting point and of the rate of crystallization is confirmed as well as an increase of the glass transition temperature and of the melt viscosity. Some quantitative differences exist, which may be attributed to the different molecular weight distribution in the polymers employed in the present w

ISSN:0032-3888    

DOI:10.1002/pen.760201204

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractIn a process for production of aligned short fiber pre‐pregs, fiber suspension passes through a converging channel to emerge as a thin free‐surf ace sheet which is laid down onto a reciprocating horizontal filter surface. Following our previous work on fiber alignment in the channel, detailed studies are reported of the suspension sheet falling under gravity, and of the deposition stage. Close agreement is found between computed and experimental velocity profiles for sheets of fiber‐free liquid. Modification of the velocities resulting from the presence of fibers aligned in the flow direction is taken into account using an increased extensional viscosity. This is evaluated using pre‐existing theory which is tested experimentally and found satisfactory. A simple relationship between velocity and fiber alignment change in the falling sheet is derived and tested experimentally. Alignment is marred by surface disturbances to the sheet. Comments are made on the stability of the free‐surface sheet. An experimental study is made of alignment changes as fibers are deposited on the filter, and the results related qualitatively to operating conditions. In general there is little difference in alignment before and after deposition, except close to the leading edge of the filter where alignment loss occurs. Previous work is reviewed and recommendations made on optimum operating c

ISSN:0032-3888    

DOI:10.1002/pen.760201205

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractAn experimental study of sandwich injection molding is reported which involves sequential injection of polymer melts with differing melt viscosity into a mold. In isothermal injection molding the relative viscosity of the two melts is the primary variable determining the phase distribution in the mold. Generally the most uniform skin‐core structure occurs when the second melt entering the mold has a slightly higher viscosity than the first melt injected. Large viscosity inequalities lead to nonuniform skin thicknesses. The influence of blowing agents and non‐uniform temperature fields on the extent of encapsulation is described. Temperature fields are very important especially if the first polymer melt injected has a greater activation energy of viscous flow (or a greater temperature dependence of the viscosity functi

ISSN:0032-3888    

DOI:10.1002/pen.760201206

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractInfrared (IR) spectroscopy was used to study molecular deformation processes in polymers as a function of stress, strain, time and temperature. Stress‐induced frequency shifts were found to depend on temperature and morphology. Deformation of viscoelastic polypropylene was examined in terms of time dependent molecular stress distributions, orientation changes, conformational variations, and chain fracture. A tie chain length distribution model was used to quantitatively interpret the IR data. Molecular deformation processes of creep and stress relaxation were found to be opposite in nature, Observed long lifetimes of highly stressed chains suggest a reappraisal of existing fracture theorie

ISSN:0032-3888    

DOI:10.1002/pen.760201207

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThermal bulk polymerization of styrene in the plate and frame batch reactor i.s simulated with a mathematical model which accounts for chain transfer to monomer and gel effect. The design parameters are: the frame thickness, the temperature policy, and the level of prepolymerization in the feed. The recommended frame thickness with 27% prepolymerization is 5 in. The resulting polydispersities and number average chain lengths range from 2.2–2.3 and 2000–2100 respectively. The implementation of temperature policy, particularly the timing of the application of the coolant, is critical to obtain satisfactory polymer quality. When pure styrene feed is used the reactor displays thermal ignition unless the frame thickness is less then 2 in. For a 5 in. frame prepolymerization should be at least 25 percent to permit adequate temperature cont

ISSN:0032-3888    

DOI:10.1002/pen.760201208

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractDynamic mechanical and differential scanning calorimetric studies of cured blends of alcohol soluble nylon with up to 40 percent epoxy resin indicate that the blends contain three phases: crystalline nylon phase, crosslinked nylon‐epoxy resin phase, and crosslinked epoxy resin phase. There are unreacted nylon chains distributed in the former two phases. The crystalline nylon phase is composed of partially reacted nylon chains and a small amount of unreacted nylon chains. Degree of ordering in this phase, both unreacted and partially reacted nylon chains, decreases with increasing epoxy resin content. Stress‐strain studies show that stress‐induced crystallization in partially reacted nylon chains in the crystalline nylon phase does occur during elongation resulting in the occurrence of a maximum tensile strength (at 5 percent epoxy resin content) as in the case of crosslinked rubber. Lap shear studies using the blend as an adhesive indicate a maximum strength at 30 percent epoxy resin content, implying that adhesion and crosslinking effects due to incorporation of epoxy resin play a major role in the adhesion perfor

ISSN:0032-3888    

DOI:10.1002/pen.760201209

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractIsothermal bulk density data measured for a number of commercially important plastics are presented for practical ranges of uniform hydrostatic pressure. Regression fitted polynomials are given for each plastic to facilitate the use of the data in computer‐aided lumped‐parameter, extrusion screw feed‐zone design methods. The cylindrical pressure‐test cell used for determining the data is described together with the theory governing its reliable op

ISSN:0032-3888    

DOI:10.1002/pen.760201210

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760201201

出版商:Society of Plastics Engineers, Inc.    

年代:1980

数据来源: WILEY