ISSN:1083-5601    

DOI:10.1002/vnl.730010402.n

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

ISSN:1083-5601    

DOI:10.1002/vnl.730010403.n

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractWhen flexible polyvinyl chloride (PVC) is used in food contact applications, there is potential for plasticizer migration. Concern over this migration has led to the development of a novel plasticizer. Eastman EPZ plasticizer is a distilled acetylated monoglyceride (DACM). EPZ is a fraction from the molecular distillation of the reaction mixture prepared by the interesterfication of fully hydrogenated coconut oil and glyceryl triacetate. It is lawful for both direct and indirect food contact according to U.S. Food&Drug Administration regulation 29 CFR 172.828. The performance of EPZ plasticizer compared with adipate and citrate plasticizers confirms its usefulness in flexible PVC. This performance, combined with its clearance as a direct and indirect food additive, offers vinyl formulators a new tool to expand the flexible vinyl market.

ISSN:1083-5601    

DOI:10.1002/vnl.730010404.n

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of elemental sulfur (S8) and tetramethyl thiuram disulfide (TMTD) on the chemical crosslinking of PVC is studied. The tensile strength, elongation at break, and gel content of crosslinked and uncrosslinked PVC molded samples, cured at different times in hot air, are evaluated. It was found that crosslinking PVC with TMTD improves its mechanical properties, and adding S8produces a slight improvement. Also, the S8presence accelerated the PVC/TMTD crosslinking reaction when the crosslinking reaction was carried out under shear forces, but not when the curing was done in hot air, where the S8retards the process.

ISSN:1083-5601    

DOI:10.1002/vnl.730010405.n

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractPoly(vinyl chloride) was post‐polymerization copolymerized with a highly basic amine, piperazine, using an aprotic solvent, dimethyl sulfoxide. By using this highly dipolar solvent, a more dilute nucleophile concentration and a lower reaction temperature were possible than in methanol‐moderated reactions. The linear substitutional reaction dominated over both the crosslinked substitutional reaction and the elimination reaction. From the nitrogen assays, pH response curves, and colorimetric results, the evidence suggests that this route may be more promising for fabricating electrode membranes or other components in which an ionically conductive film is desira

ISSN:1083-5601    

DOI:10.1002/vnl.730010406.n

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractRelative rates are given for the reaction of a model compound, phenacyl chloride, with simple lead carboxylates and actual lead stabilizers. The data suggest that lead stabilization is more complex than previously indicated, with reaction products that are lead double salts, rather than simply lead dichloride. This is rationalized in terms of reactive site coordination to the extended lead stabilizer structure, as opposed to the stabilizer being merely a carrier of PbO.

ISSN:1083-5601    

DOI:10.1002/vnl.730010407.n

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractLead replacement heat stabilizers have made considerable inroads in areas where water resistance is not significant, primarily in wire jackets and insulations not for wet locations. In areas where short‐term moisture resistance is required, such as with flexible cord insulation and electrical tapes, nonlead products are either in use or under development. In those areas where long‐term water resistance is needed, as with geomembranes and many wire insulations, despite much experimentation, commercial products are not in use as yet in the United States. The factors involved are discus

ISSN:1083-5601    

DOI:10.1002/vnl.730010408.n

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractThe kinetics of the thermal degradation of solid powdered poly(vinyl chloride) (PVC) under nitrogen was studied by thermogravimetry, rate of hydrogen chloride evolution, and rate of polyene sequence formation. These results are accommodated by a chain mechanism involving initiation by random dehydrochlorination at normal monomer residues of PVC, and a series of intermediates, each leaking to a stable conjugated polyene sequence. Structural irregularities such as allylic and tertiary chlorine are responsible for a fast initiation process at the very beginning of the degradation. Mean rate constants and activation parameters for random initiation, propagation, and termination reactions of the PVC degradation chain were calculated by simulation. Activation enthalpy/entropy correlations for the experimental data available for dehydrochlorination of chloroalkanes and chloroalkenes in the gas and in the liquid phase or nonpolar solvents and elementary reactions of PVC degradation show that initiation is an HCl elimination through a transition state of four centers requiring a synperiplanar conformation of the>CH–CCl

ISSN:1083-5601    

DOI:10.1002/vnl.730010409

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractSemiempirical Molecular Orbital Calculations (MNDO AM1) support kinetic results concerning the molecular mechanism of thermal degradation of PVC and show that under special conditions radical and ionic mechanisms are also possible. The degradation of poly(vinyl chloride) is a complex chain dehydrochlorination that consists of an initiation process to generate an active intermediate followed by chain reactions that generate additional active intermediates with progressively increased numbers of double bonds. Each intermediate partitions between an intermediate with one more double bond and a stable conjugated polyene with the same number of double bonds. At low and moderate temperatures thermal degradation of PVC in an inert atmosphere is a succession of molecular concerted reactions. The initiation process is a 1,2‐elimination through a four center transition state requiring a synperiplanar conformation. There are two main chain reactions: the first is a 1,4‐elimination from allylic chlorine atoms and methylenescisto a double bond through a transition state of six centers; the second is a 1,3‐rearrangement of hydrogen atoms catalyzed by hydrogen chloride. The chain reaction is interrupted when a relatively stabletransdouble bond is formed and no hydrogen chloride is present to catalyzetrans‐cisisomerization or 1,3‐rearrangement. Macro carbocations formed by heterolysis of carbon‐halogen bonds in the presence of strong Lewis acids react much faster than does the original PVC in concerted elimination by 1,2‐synor 1,4‐cismechanisms, promoting a so‐called catastrophic, very fast degradation. Macro radicals formed by thermal homolysis, irradiation or reaction with promoters can also promote very fast hydrogen chloride elimination because of a special mechanism consisting of a 1,2‐rearrangement of a chlorine atom followed by a concerted 1,3‐elimination through a five ce

ISSN:1083-5601    

DOI:10.1002/vnl.730010410

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY

摘要:

AbstractMolecular modeling software is employed to correlate the thermal stability of an organotin molecule in PVC and molecular structure. Synthesizing model organotin compounds, measuring dynamic properties in PVC, and calculating structural and electronic properties yield an empirical relationship between the stabilizing ability of the tin molecule and electron density of the heteroatom.

ISSN:1083-5601    

DOI:10.1002/vnl.730010411

出版商:Society of Plastics Engineers    

年代:1995

数据来源: WILEY