摘要:

Professor Guyot asked me to highlight the advances in the area of PVC physics described at this meeting and to predict the future- a most formidable task. First, however, I feel i t i s not only my duty a s a representative attendee, but a distinct honor and with the greatest personal pleasure, to express on behalf of all of the participants our deepest appreciation to Professors Guyot and Michel, and to all of the associated personnel, appreciation for arranging a most memorable scientific and social program, one with numerous highlights I am sure we will all long remember. The work involved in arranging a program such a s this and overseeing all of the details can only be known by one who has been involved. Unfortunately, our hosts' work really is not yet over, since they intend to read and edit all of the discussion sections in order to permit a complete permanent record of the entire conference. For this, also, we express both our appreciation and best wishes.

ISSN:0022-2348    

DOI:10.1080/00222347708212217

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Since the first International Symposium in 1970, studies on the characterization of PVC have mainly dealt with three topics: existence of supermolecular aggregates which a r e considered responsible for numerous thermornechanical and rheological properties of PVC; tacticity and chain defects which could alter the thermal sensitivity of PVC to processing conditions; morphology of the powder which is of paramount importance for the processability of the polymer.

ISSN:0022-2348    

DOI:10.1080/00222347708212218

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Observation of the diffusion of quinoline inside PVC grains by microscopy represents a very sensitive method of PVC powder differentiation. The kinetics of microdiffusion is measured as a function of time and temperature (exponential function) by the fraction of impregnated grains of the powder which varies, on a broad range, as a function of resin properties, which are mainly influenced by the conversion factor. Gaussologarithmic representation of the phenomenon gives a Galton's straight line, the slope of which is related, more or less, to the homogeneous character of microdiffusion in the powder. That aspect is described in relation to the problem of formation of “fish eyes.”

ISSN:0022-2348    

DOI:10.1080/00222347708212219

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Hitherto it has not been possible to produce a microscopic image with adequate resolution of the high-impact two-phase system poly(vinyl chloride) (PVC)/chlorinated polyethylene (CPE) due to inadequate phase contrast. With the aid of various chemical staining methods and through ion etching, a way has been found for studying the microstructure of the PVC/CPE system by light microscopy and electron microscopy. These independent visualization techniques and scanning electron micrographs of fracture surfaces show, as the morphology with optimal mechanical and rheological properties, networklike distribution of the rubber phase and, imbedded in this, a PVC phase consisting of primary particles.

ISSN:0022-2348    

DOI:10.1080/00222347708212220

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Electron microscopy indicates that PVC contains aggregates on three size scales: 100 to 500 Å, 0.1 to 0.5 μm, and 1 to 10 μm. The effects of plasticizers and processing conditions on this morphology and its effect on mechanical properties are discussed.

ISSN:0022-2348    

DOI:10.1080/00222347708212221

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Raman spectroscopy has been used to obtain two types of structural information for poly(vinyl chloride) samples. The first is a more complete assignment of the carbon-chlorine stretching modes. The prediction of Moore and Krimm that the frequencies of the B1 mode of longsyndiotactic sequences in crystalline regions should differ because of correlation splitting in the infrared and Raman spectra has been verified. The problems involved in the quantitative interpretation of the Raman spectrum by use of computer resolution of overlapping bands to give information on the proportion of the various conformers of the syndiotactic and isotactic configurations, have been examined critically. The second application is the use of resonance Raman spectroscopy to characterize polyene sequences containing between 9 and 17 conjugated double bands in degraded PVC samples. Measurements on a commercial polymer degraded at 160 and 190°C show that the concentration of a conjugated polyene of a particular sequence length is a function both of the temperature and the overall degree of degradation. Preliminary results for thermally degraded samples of higher tacticity and for γ-irradiated specimens suggest that resonance Raman spectroscopy will be equally useful in these cases. The current limitations of the technique are discussed briefly.

ISSN:0022-2348    

DOI:10.1080/00222347708212222

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The characterization of a set of reference materials of PVC for molecular weight measurement is described. Aspects of measurements by membrane osmometry, light scattering photometry, and gel-permeation chromatography in 1,2-dichlorobenzene at 135°C are discussed.

ISSN:0022-2348    

DOI:10.1080/00222347708212223

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Anomalies during precipitation fractionation of PVC from THF solution with H20 as nonsolvent were investigated by using GPC and solution infrared techniques. The data indicate that separation during the fractionation takes place by both stereoregularity and molecular weight because of the formation of molecular aggregates during the precipitation and collection of fractions. The separation by stereoregularity dominates at the beginning of the fractionation. The aggregates formed at this point are comprised of highly syndiotactic molecular segments which tend to precipitate before segments of lower stereo-regularity but higher molecular weight. For the first few fractions, molecular weights recorded may be seriously overestimated unless care is taken to disperse the aggregates by appropriate heating of the solutions used for GPC characterizations. After 25-30% of the polymer precipitates, the fractionation becomes independent of stereoregularity and proceeds according to molecular weight. While the tendency for aggregation may be great for highly syndiotactic and/or high molecular weight chain segments, the data for low molecular weight fractions having low stereoregularities also show evidence of molecular aggregation. This suggests that factors such as syndiotactic sequence length and degree of branching may be quite important in determining aggregation tendencies. Typical GPC chromatograms indicate that the fractions which contain highly aggregated molecules have bimodal GPC curves. Complete resolution of the aggregate peak from the soluble portion can be achieved by operating the GPC in the recycle mode. Aggregation may not be apparent from GPC curves obtained for PVC whole polymers, particularly atactic commercial grade samples. Among samples with similar average molecular weights anomalies in fractionation increase with polymer stereoregularity. Because separation by stereoregularity dominates at the beginning of a fractionation a “molecular weight inversion” may occur where successive fractions have higher molecular weights than the initial fraction. The syndiotacticity (S values) of the fractions vary indicating that each polymer has a unique syndiotacticity distribution. The observations reported have been verified in many fractionations with several different PVC whole polymers.

ISSN:0022-2348    

DOI:10.1080/00222347708212224

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

Prof. P. H. Geil(Case Western Reserve University, Cleveland, Ohio): portant role in all of the sessions of the symposium. In discussing with the panel members how we could best use the discussion time available to us today, we were fortunate to have preprints of Dr. Carrega's lecture, He has done an excellent job of reviewing the entire area of characterization so that it was not really fitting for each of us, initially, to pick out one or two areas, saying a few more words about them, but rather we felt that what we should do is to open up the session for questions now. At the end, some members of the panel will make a few comments. There will be a rather broader review of certain selected areas of the topic which will be given during the panel discussion part of the individual session on Characterization. We feel it is of more value to have reasonable time for general discussion of the papers this morning than for each of us to present further papers.

ISSN:0022-2348    

DOI:10.1080/00222347708212225

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The development of our belief that the branches in PVC are CH2Cl groups and a further mechanism for their production are given. Published IR figures for these branches are likely to be 2.5 times too large.

ISSN:0022-2348    

DOI:10.1080/00222347708212226

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor