摘要:

AbstractThe synthesis of poly(3,3‐phthalidylidene‐4,4′ ‐biphenylylene) (PPB) by precipitative Friedel‐Crafts homopolycondensation of 3‐(4‐biphenylyl)‐3‐chlorophthalide was studied. The polymer‐catalyst complex precipitated from the initially homogeneous reaction mixture was shown to be active and providing the growth of macromolecular chains. The polymer obtained in the form of smooth, transparent glass‐like particles, depending on the reaction parameters, may have either uni‐ or bimodal molecular weight distribution. Molecular characteristics were not found to depend on the size of the polymer particles. “Precipitative” PPB shows improved properties and higher crystallinity in com

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120101

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe electrical conductivity, σ, of cellulose HYPHAN® and its complexes with Cr3+, Mn2+, Mo5+or Hg2+was measured from room temperature to 510°C. The activation energy, ΔE, of the samples was calculated from log σ against 1/T curves. The results show that the electrical conductivity increases by temperature with two maximum peaks. The first peak is attributed to the moisture content, while the second one is attributed to the thermal degradation of the cellulose chain. The values of the activation energy indicate that the samples change from low semiconductor to high semiconductor property with hea

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120102

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper presents the influence of glass fibres on crystallization kinetics and on matrix morphology for poly(ethylene terephthalate) (PET)/glass fibre composites. The following parameters are also considered: fusion‐crystallization conditions, thermal stability and the addition of nucleating agents in the matrix (talc or sodium benzoate). It clearly appears that the influence of those additives on the crystallization of PET is predominant compared to the effect of stiffening fibres. Moreover, the application of shear stresses at the PET/glass fibre interface promotes the growth of a different crystalline superstructur

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120103

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractPhotodegradation and loss of UV stabilizer resulting from natural and accelerated exposure in stabilized linear low density polyethylene (LLDPE) are investigated by spectroscopic techniques. It is found that the processes governing the loss of UV stabilizer are quite different under the two modes of UV exposure. This result clearly demonstrates that predictions concerning polymer lifetime based on the disappearance of additives must be avoided. For a large number of stabilized samples, acceleration factors according to different criteria have been estimated. Examination of the natural photodegradation process of stabilized LLDPE through mechanical property changes establishes that stabilized LLDPE undergoes catastrophic breakdown of the elongation at break the instant the carbonyl IR band begins to develop.

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120104

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractInfluences of nitrile rubber (NBR, acrylonitrile content 33.5 – 36.5 wt.‐%) on the structure and mechanical properties of poly(vinyl chloride) (PVC)/low density polyethylene (LDPE) blends and its synergism with crosslinking agent have been studied. The addition of NBR to the blend is accompanied by a decrease in domain size and improvements in mechanical properties of the blend. When dicumyl peroxide (DCP) is added to the blend together with NBR, good synergism is caused and mechanical properties will improve dramatically. It is concluded that NBR can promote the phase dispersion of PVC and LDPE and their interfacial adhesion. Then, the probability of DCP existing at the interface will increase and more co‐crosslinked products will form. Therefore, compatibilization and crosslinking are both exerted suffici

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120105

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractNovel photocrosslinkable polymethacrylate systems with enhanced thermal stability and solvent resistance were synthesized. Copolymers of methyl methacrylate (MMA) or butyl acrylate (BuA) with 4‐maleimido benzoic acid (MBA) were synthesized and photocrosslinkable methacrylic functions were incorporated through the pendent COOH groups. Photofunctional groups were introduced by the acid chloride route and by the epoxy‐carboxy reaction. Photocrosslinking was performed using UV radiation of 350 nm in the presence of a photo‐initiator. The kinetics of photocuring was studied with a model multiacrylate. The imide‐modified photocured acrylate polymer exhibited enhanced solvent resistance and thermal stability, compared with the unmodified

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120106

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe curing behaviour of bismethacryloyl derivative of diglycidyl ether of bisphenol A (vinyl ester VE resin) containing styrene and α‐methyl styrene (MS) as reactive diluents was studied. Delayed curing was observed in samples containing increasing proportions of MS. Interfacial shear stress of untreated as well as γ‐methacryloyloxy‐propyl trimethoxy silane (MTS) treated, glass fibre‐reinforced VE resin composites were measured by single fibre technique. In comparison to untreated glass fibres, a 30 – 50% increase in interfacial shear stress was observed in composites based on MTS treated glass fibres. Addition of up to 5 wt.‐% MS to VE resin did not affect the interfacial shear strength (ILSS). This behaviour was observed by using ILSS measurement of both glass fabric‐reinforced composites as well as single fibre specimens. Further increase in MS to 15 wt.‐% resulted in an increase in ILSS and bending stiffness as well as

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120107

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractModifications of ethylene/vinyl acetate copolymers (EVA) by saponification and graft polymerization with various acids were studied. The greater the degree of saponification, the higher is the melting temperature, the crystallinity and the melt viscosity of poly(ethylene‐co‐vinyl alcohol‐co‐vinylacetate). Tensile tests display that the flexibility of EVA decreases gradually as the degree of saponification increases. This effect may be caused by the interaction of hydrogen bridges after saponification. Graft copolymers of EVA with various acids were studied. The greater the portion of vinyl acetate of EVA, the greater is the graft ratio with various acids decreases in the order acrylic acid>fumaric acid>itaconic acid>maleic anhydride; this order may reflect a steric effect.Relationships between peel strength and the degree of saponification of EVA show that the adhesive strength increases initially and reaches a maximum value at a degree of saponification in the range of 20 ∼ 30%. The adhesive strength of EVA grafted with acid increases remarkably at low acid contents (less than 0.5 wt.‐%) and then remains constant even at greater acid content in the graf

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120108

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractDurch Photopolymerisation von 4,4′‐Dibenzoyldiphenylmethan und 4,4′‐Bis(aαhydroxybenzy1)‐diphenylmethan mit UV‐Licht in benzolischer Löisung lassen sich Polybenzpinakole herstellen. Die Polymeren können durch Fällungsfraktionierung in Fraktionen mit Molekulargewichten bis etwa 20000 aufgetrennt werden. Polybenzpinakole zerfallen ebenso wie Benzpinakol thermisch in Diarylhydroxymethyl‐Radikale. Diese initiieren bei 60 bis 100°C die radikalische Polymerisation von Styrol direkt und teilweise auch durch Wasserstoffübertragung von den Initiatorradikalen auf das Monomere. Mit steigender Temperatur nimmt dabei der Anteil der Wasserstoffübertragung an der Initiierung ab, was aus den Reaktionsordnungen bezüglich der Monomerkonzentration geschlossen werden kann. Soweit die Polymerisation von Styrol mit Oligo‐Benzpinakol direkt durch Diarylhydroxymethyl‐Radikale ausgelöst wird, entstehen Polystyrolketten mit eingebauten Oligo‐Benzpinakol‐Segmenten, die thermisch spaltbar sind, was durch die Abnahme der Molekulargewichte beim Erhitzen in toluol

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120109

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe correlation between different methods of measuring thermo‐oxidative stability of polypropylene has been studied. The oxidation induction times were measured using differential scanning calorimetry (DSC) in the temperature range from 160°C to 240°C up to 10000 min. The same samples were oven‐aged in the temperature range from 130°C to 160°C up to 13000 h.The dynamic experiments performed by DSC show different results for differently stabilized samples. At slow heating rates the results of the dynamic experiments corresponded best to the results of the isothermal experiments.The straight‐line Arrhenius plots of the isothermal DSC measurements do not correlate with the straight‐line Arrhenius plots of the oven‐aging tests. The Arrhenius plots obtained by these two methods either intersect close to the melting temperature of polypropylene or show jumps towards longer times when switching from DSC to oven‐aging. It was found that the apparent activation energies obtained from the oven‐aging tests are much lower than these obtained by DSC measurements. Almost the same activation energies were obtained for all the samples in oven‐aging, while for the differently stabilized samples the activation energies from DSC measurements showed different results.Antistatic additives and colour pigments influence the thermal stability of polypropylene. Especially red pigment acts like a stabilizer for polypropylene, which is noticed at oven‐aging testing, but at higher temperatures it loses th

ISSN:0003-3146    

DOI:10.1002/apmc.1993.052120110

出版商:Hüthig&Wepf Verlag    

年代:1993

数据来源: WILEY