ISSN:0032-3888    

DOI:10.1002/pen.760140502

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractCopolymers of vinyl chloride with 2‐chloropropene were prepared as models for tertiary‐chlorine branching in PVC. Rates of thermal dehydrochlorination of copolymers containing up to 2 mol percent 2‐chloropropene were found to be a linear function of composition. By comparing the decomposition rates of the copolymers with that of PVC prepared under similar conditions, we estimate the maximum tertiary‐chlorine content of PVC at 0.1 to 0.2 mol percent. This figure is of the same magnitude as estimates of the content of tertiary‐chlorine, random unsaturation, and long‐chain branching obtained in previously published studies of PVC. Possible mechanisms for tertiary‐chlorine branch formation include chain‐transfer to polymer and copolymerization with unsaturated chain‐ends. By applying the conventional copolymerization equation, using the reactivity ratios of the vinyl chloride/2‐chloropropene system, it is shown that the copolymerization mechanism predicts a tertiary‐chlorine branch content close to the estimated value. Both mechanisms also agree qualitatively with reported effects of polymerization temperature and conversion on branching

ISSN:0032-3888    

DOI:10.1002/pen.760140503

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractIt was theorized that the heat stability of PVC may be improved by exchanging the “weak” (allylic and tertiary) chlorines by groups of higher bond strength, e.g., phenyl. Thus PVC was phenylated by ϕ3Al in carbon disulfide slurry for various times (1 to 5 hrs) and temperatures (from −30 to +45°C). The ϕ3Al concentration, temperature and time of ϕ3Al treatment greatly affect the ultimate heat stability of PVC. Significant improvement in the heat stability was obtained by treating PVC in carbon disulfide at 25°C for 1 hr. The mechanism of phenylation was studied by model experiments in which the possible structural irregularities in PVC were simulated by small molecule chlorine compounds, i.e., 3‐chloro‐1‐butene, 1,3‐dichloro‐1‐butene, 4‐choro‐2‐pentene were models for terminal and inchain allylic chlorines, t‐butyl chloride was the model for tertiary chlorine at branch site, and isopropyl chloride simulated regular secondary chlorines. The reactions between ϕ3Al and these chlorides were carried out at 35°C for various times and the NMR spectra were analyzed. The ϕ3Al + tBuCl reaction in carbon disulfide gives t‐butylbenzene (Wurtz coupling) and isobutylene oligomers. Evidently ϕ3Al (or the ϕ2AlCl formed) dehydrochlorinates tBuCl to isobutylene which rapidly oligomerizes in the presence of Lewis acids. In aromatic diluents, i.e., benzene, chlorobenzene, and o‐chlorotoluene, Friedel‐Crafts t‐butylation of the diluent occurs; in mesitylene t‐butylation is absent presumably because of steric hindrance and small amounts of t‐butylbenzene are formed by Wurtz coupling. All the allyl chlorides examined are rapidly phenylated by ϕ3Al in carbon disulfide at 35°C and yield the expected products: 3‐chloro‐1‐butene → 1‐phenyl‐2‐butene; 1,3‐dichloro‐1‐butene → 1‐chloro‐3‐phenyl‐1‐butene; 4‐chloro‐2‐pentene → 4‐phenyl‐2‐pentene. The kinetics of phenylation by ϕ3Al of model compounds have been studied and the following rate constants were obtained:kallyl= too fast to measure,ktBuCl= 1.0, andkiPrCl= 9 × 10−4l/mole min. Evidently the rate of the ϕ3Al + RCl reaction is m

ISSN:0032-3888    

DOI:10.1002/pen.760140504

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA new particle size analysis of latexes has been developed using a disc centrifuge allowing a very fast zonal sedimentation of particles followed by an automatic optical device. This method, which involves 5‐10 minutes, permits the routine control of fabrication for emulsions of PVC. Linked to a computer, it permits accurate determinations of particle sizes in terms of weight, surface or number averages. The complete operation for one latex requires less than 15 minutes. This technique has been used to follow the growth of particles in seeding operations, i.e., monosized seed latex and the competitive growth of 2 populations of seed particles. Some results have also been obtained by comparing accurate particle size analyses of latexes with rheological properties of plastisols obtained from these latexe

ISSN:0032-3888    

DOI:10.1002/pen.760140505

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760140506

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe aggregates found in dilute solutions of nearly atactic PVC have been shown to consist of 10 to 15 single molecules held together by a crystalline nucleus. Based on the postulate that the last crystallites in a PVC melt have the same structure as found in dilute solution, a relation between the melting temperature in shear (Tdyn), the static melting temperature (Tm) and the shear stress (τ) is found:\documentclass{article}\pagestyle{empty}\begin{document}$$ {1 \mathord{\left/ {\vphantom {1 {T_{{\rm dyn}} }}} \right. \kern-\nulldelimiterspace} {T_{{\rm dyn}} }} - {1 \mathord{\left/ {\vphantom {1 {T_m }}} \right. \kern-\nulldelimiterspace} {T_m }} = \frac{{\tau ^2 }}{{Q \cdot T_{{\rm dyn}} ^2 }} $$\end{document}whereQis a constant. The model predictions are in accordance with data from a Brabender rheometer and a Rheometrics mechanical spectrometer.Qis found to be a constant for samples with weight average molecular weights in the interval between 70,000 and 160,000 corresponding to polymerization temperatures between 40 and 70°

ISSN:0032-3888    

DOI:10.1002/pen.760140507

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effect of insoluble gel material, crystalline aggregates, and suspension particle membranes on the physical and mechanical properties of solution cast films of suspension PVC has been studied. The chemical structure and morphology of the insoluble gel material was also studied. The suspension particle membranes are found to contain significant amounts of hydroxyl and carbonyl groups but are still predominately PVC. These particles affect the transparency of cast films as well as the surface topography by forming discrete clusters upon drying which are uniformly distributed throughout the films. Finally, insoluble gel material is found to have no significant effect on the low and high speed mechanical properties of the films.

ISSN:0032-3888    

DOI:10.1002/pen.760140508

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effect of polymerization temperature on the melt flow behavior of PVC of varying molecular weights has been studied over a wide shear rate range. For the same molecular weight, higher melt viscosities are observed for polymers prepared at lower temperatures. The shear rate dependence of the viscosity vs molecular weight plot is shown to be nonlinear over the shear rates examined. The inability to achieve a limiting zero‐shear viscosity is discusse

ISSN:0032-3888    

DOI:10.1002/pen.760140509

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effect of changes in crystallinity on the β‐transition in poly(vinyl chloride) was studied by dynamic mechanical measurements of loss tangent (tan δ) and storage modulus (E′) over the temperature range −160° to 85°C. Four frequencies were covered, 3.5, 11, 35, and 110 Hz. The data presented demonstrate that crystallinity has a significant influence on the relaxation processes involved in the β‐transition. The restrictions on segmental mobility imposed by crystallinity are most pronounced in the region betweenTβandTg, withTβtending to shift to lower temperatures,Tgshifting to slightly higher temperatures, the magnitude of tan δ decreasing, and engineering tensile strength increasing. Our data also show that individual PVC resins have mechanical and physical properties which differ enough so that comparisons which are often made between them may be inconclusive. Moreover, the properties of one resin may be more sensitive to thermal treatment than those of another. We are continuing this study to establish correlations between the observed trends and other important mechanical properties such as impact strength, toughness, tensile, and compr

ISSN:0032-3888    

DOI:10.1002/pen.760140510

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractIt is known that the fusion rate of rigid PVC in an extruder partly depends upon the lubricants that are used. In the present study it is shown that different stabilizers have a great influence upon the rate of fusion of rigid PVC. Results from extrusion experiments and the Brabender Plastograph strongly indicate that a correlation exists between rapid melting in the extruder and the melt viscosity‐temperature relation of the polymer blend. The reason why certain stabilizers cause a more rapid fusion of the PVC is attributed to the chemical structure of the stabilizer

ISSN:0032-3888    

DOI:10.1002/pen.760140511

出版商:Society of Plastics Engineers, Inc.    

年代:1974

数据来源: WILEY