Search results for "Ionomer"

Ex vivo study of bacterial coronal leakage in indirect pulp treatment

2012

Objective: The aim of this study was to evaluate, ex vivo, bacterial coronal leakage with different antimicrobial agents applied to the dentine for indirect pulp treatment (IPT). Study Design: Sixty extracted teeth were prepared and randomly distributed into 5 groups (n=10): Group 1: no antimicrobial dentine treatment; group 2: 1% chlorhexidine (CHX)+1% thymol varnish (Cervitec®); group 3: 2 % CHX solution; group 4: 40% CHX varnish (EC40™) and group 5: Clearfil™ Protect Bond (CPB). Ten teeth served as controls. The teeth were restored using a resin-modified glass ionomer cement (GIC) and then mounted in a two-chamber device. The coronal access was exposed to Streptococcus mutans for 45 days…

Effect of thermocycling with or without 1 year of water storage on retentive strengths of luting cements for zirconia crowns

2015

Abstract Statement of problem Bond stability between zirconia crowns and luting cement and between cement and dentin is a main concern; however, only limited evidence is available as to its longevity. Purpose The purpose of this in vitro study was to measure the retentive strengths of 7 self-adhesive cements (RelyX Unicem Aplicap, RelyX Unicem Clicker, RelyX Unicem 2 Automix, iCEM, Maxcem Elite, Bifix SE, SpeedCem), 2 adhesive cements with self-etch primers (Panavia 21, SEcure), 1 glass ionomer cement (Ketac Cem), 1 resin-modified glass ionomer cement (Meron Plus), and 1 zinc phosphate cement for luting zirconia crowns (LAVA) to extracted teeth after thermocycling with or without 1 year of …

Liquid-crystalline ionomers

1997

Liquid-crystalline (LC) ionomers combine the properties of ionomers (cluster formation of the ionic groups) with LC phases. They can be prepared with LC main-chain and LC side-chain polymers.

Films from styrene–butyl acrylate lattices using maleic or succinic surfactants: mechanical properties, water rebound and grafting of the surfactants

2000

Abstract A series of anionic and zwitterionic maleic surfactants have been synthesized and engaged in styrene–butyl acrylate emulsion polymerization. Some non-reactive succinic analogs have been synthesized in order to perform their comparison with the maleic surfactants in polymerization experiments. Films from the obtained lattices were cast, and their mechanical properties and the water rebound were tested. The results of water rebound demonstrate significant difference between the films prepared with maleic or succinic surfactants. Water rebound of the films after 34 days in the case of succinic surfactants was found to be between 51 and 95%, while for maleic surfactants it is only 25–4…

LC Ionomers with Phosphonate Groups and Their Multilayer Build-Up

2002

This paper describes the synthesis of new liquid-crystalline (LC) ionomers (semiflexible LC mainchain polymers with ionic groups as side groups) by polycondensation of substituted malonates with mesogenic diols. Phosphonic acids were used as negative groups, and phosphonium and ammonium ions as positive groups. The presence of these ionic groups leads to gelation (physical crosslinking) of the polymers, which display a rubbery consistency. As expected from the reference polymers without an ionic group, all polymers show smectic phases. These phases are destabilized by bulky side groups (e.g., phosphonium ions or phosphonic acid esters). They are, however, stabilized by phosphonic acid group…

Reactive dual-component compatibilizers for polycarbonate/high-density polyethylene blends

1995

Enhanced compatibility for blends of polycarbonate with high-density polyethylene has been achieved with the addition of 5 wt% compatibilizers composed of 1 : 1 mixtures of phenoxy and the sodium ionomer of an ethylene methacrylic acid copolymer at two different levels of neutralization. Both components of the compatibilizer have been found to be capable of reacting with the polycarbonate phase to produce branched polymer chains. These impart a degree of compatibilization in polycarbonate/high-density polyethylene blends, however at higher levels of sodium in the compatibilizer the polycarbonate phase undergoes crosslinking reactions, causing severe embrittlement. Compatibilization effects …

Functional Liquid Crystalline Polymers: Ferroelectric Polymers and Liquid Crystalline Elastomers and Ionomers

1994

Abstract The incorporation of different functional groups in liquid crystalline polymers opens the way to a variety of interesting new materials, which may be used for non-linear optics, as piezo-elements or as two-phasic composite materials.

Radiation grafting functionalization of poly (vinylidene fluoride) to compatibilize its blends with polyolefin ionomers

1998

Blends of a crystalline vinylidene fluoride copolymer (PVDF) and a polyolefin ionomer were produced by melt mixing and characterized by a variety of techniques to examine the effect of increasing the level of salt formation on morphology. The PVDF component was also grafted with methacrylic acid by irradiating the polymer powder and subsequently treating it with an aqueous monomer solution. The effect of neutralizing the acid in both polymer components to produce the corresponding zinc salt was also investigated. Compatibilization was accomplished by the addition of zinc acetyl acetonate (ZnAcAc) to the mixture. This increased the viscosity of the polyolefin ionomer phase, comparable to tha…

1995

Redoxactive liquid crystalline (LC) side group polymers were prepared by copolymerization of liquid crystalline acrylates and ferrocene-containing acrylates. The corresponding liquid crystalline ionomers were synthesized by a reversible redox reaction. The incorporation of tetra-alkylated ferrocene derivatives leads to LC polymers with reduced redox potential. These polymers can be oxidized under mild conditions to the corresponding ionomers, which are much more stable in solution than LC ionomers containing monoalkylated ferrocenium ions. Dynamic mechanical measurements and small angle X-ray scattering (SAXS) perfomed on LC ionomers prove the existence of ionic superstructures (clusters) w…

Organoclay Nanocomposites from Ethylene-Acrylic Acid Copolymers

2006

A study of the structure–property relationships for nanocomposites prepared by melt compounding from ethylene–acrylic acid copolymers of varied composition and molecular architecture, and organoclays modified with different ammonium ions has been made by DSC, POM, SEM, TEM, WAXD, and rheological and mechanical tests. Within the series of clays investigated, the best levels of dispersion were displayed by those organically modified with quaternary ammonium ions containing two long alkyl tails. The relevant nanocomposites were shown to possess mixed exfoliated and intercalated morphology. The spacing of the intercalated clay stacks, most of which comprise few silicate layers, was found to be …