Phenol-formaldehyde Oligomers Research Articles

The preparation and properties of free films based on epoxydiane and phenol-formaldehyde oligomers

It has been shown by GPC that no chemical reaction occurs between epoxydiane and Bakelite-type (resole) phenol-formaldehyde oligomers when they are heated in ethylcellosolve solution at 120° for 5 hr. Curing the compositions at 200° is accompanied by changes in the infrared spectra in the vibration regions of aliphatic alcohol CO bonds, ester bridges and benzene C = C bonds, related to crosslinking of the oligomers. Using attenuated total internal reflection IR spectroscopy, it was shown that the chemical compositions and the structure of the surface and bulk layers of the polymer are identical. The original oligomers and the films based on them are amorphous to X-rays. The supermolecular structure of the films is globular and the globule size is somewhat increased when the MM of the oligomers increases.

Structure and physical and mechanical properties of three-dimensional polymers based on epoxy and phenol-formaldehyde oligomers

Structure and physical and mechanical properties of three-dimensional polymers based on epoxy and phenol-formaldehyde oligomers

Mechanical and dielectrical properties of the cured epoxide-dianephenol-formaldehyde oligomers

Deformation-strength properties have been investigated for network polymers based on epoxide-diane oligomers of different MW, and on resole phenol-formaldehyde (PF) oligomers in the glassy and the rubber like states. It was found that tensile properties of the network polymers depend neither on the thermal prehistory of solutions of the starting oligomers in ethylcellosolve, nor on the thickness of samples in the interval 20–250 μm. Density values of the crosslinked network polymers increase with increasing MW of the oligomers at the expense of curing both via functional endgroups, and via functional groups in the middle of the oligomer chains. Methods of dielectric relaxation and of differential scanning calorimetry were used to determine glass-transition temperatures of the polymers: where M c is high, T g is not a function of M c ; T g rises as M c decreases and as M c values approximate to the length of statistical Kuhn segments of epoxide-diane oligomers.

Influence of diffusion and of phase equilibrium in elastomer-phenol-formaldehyde oligomer systems on the strength of adhesive bonds

Mutual diffusion processes and phase transitions in phenol-formaldehyde oligomer (PFO)-elastomer systems have been investigated at various stages of cure of PFO during the formation of adhesive bonds. The distribution of components in the adhesion contact zone has been determined. It is shown that the cure of the PFO fixes the concentrational distribution at the stage of diffusion mixing of the components. The results of electron-probe X-ray microanalysis of the adhesion contact zone between PFO and butadiene-nitrile elastomers show that phase transitions occur in this zone, and result in formation of structure that provides the bond strength. A mechanism of formation of adhesive bonds is proposed for partially compatible components.

オリゴマーの合成と反応

Oligomers are the low-molecular-weight members of polymeric compounds in the molecular weight range from a few hundred to several thousand. Because of their unique physical properties, clearly differing from those of conventional low-molecular-weight compounds and high polymers, oligomers are currently used in many practical fields. This review summarizes methods for oligomer synthesis, primarily by addition oligomerization, and ralated reactions.The scope of this review encompasses (i) the principle and examples of the synthesis of “telechelic” oligomers with a functional group at both chain-ends by addition (radical, cationic, anionic, and group-transfer) oligomerizations ; and the preparation of telechelic oligomers with ethynyl terminals and linear phenol-formaldehyde oligomers; (ii) the synthesis of “macromers” (oligomers having a polymerizable end-group) by ionic and radical mechanisms and their polymerization reactivity ; and (iii) the synthesis of cyclic or cyclic unit-containing oligomers. Problems in these oligomer syntheses are also discussed briefly.

Mechanism of formation of adhesion bonds between an elastomer and phenolformaldehyde oligomer

A novolac phenolformaldehyde oligomer was used as adhesive for attaching to metal butadiene-nitrile rubber during vulcanisation. It was shown that the formation of an adhesion bond with rubber takes place as a result of the diffusion of the oligomer into the surface layer of rubber with the formation of a transition layer some dozen μm thick. The formation mechanism of the adhesion bond was described using results of diffusion and solubility of the oligomer in SKN-18, SKN-26 and SKN-40 rubbers.

Increase in elastic modulus of polyamide yarns modified with phenol-formaldehyde oligomers

Increase in elastic modulus of polyamide yarns modified with phenol-formaldehyde oligomers

Some structure‐property relationships in polymer flammability: Studies of phenolic‐derived polymers

AbstractThe investigation of the thermal degradation of the char‐formaing phenol–formaldehyde resins is conducted to provide information for the systematic design of high temperature flame‐resistant phenolics. Three different processes of curing are used: (1) Formaldehyde or s‐trioxane is reacted with m‐substituted phenol–formaldehyde oligomers under acidic conditions to give the methylene bridged‐novolac resins. (2) Phenol and m‐substituted phenols are reacted with CH2O under basic conditions and then heated to give the methylene bridged resol resins. (3) p‐Terephthaloyl chloride and m‐and p‐substituted novolac oligomers are reacted to give cured resins with ester linkages. The evaluation of the effect of various substituents indicates that the oxygen index (OI) increases from about 33 for unsubstituted phenolics to about 75 for meta‐halogen substituted phenolics. The evaluation of the effect of various crosslinking agents shows that the OI for CH2O‐cured phenolics is 75 as compared to 50 for the trioxane cured phenolics and to 40 for the terephthaloyl chloride cured phenolics. A set of phenolic copolymers with different weight percentage content of halogen substituted phenols are synthesized as novolacs and resols. The results surprisingly indicate no increase of OI for the cured novolac copolymers, whereas the increase is observed for the cured resol copolymers. The activation energy for the thermooxidative degradation of the cured novolacs is about 12–15 kJ/mol lower as compared to that of the curd resols.

Study of the heterogeneous reaction of formation of primary products of addition in the synthesis of phenol-formaldehyde and naphthalene-phenol-formaldehyde oligomers

A novel method has been developed for the synthesis of novolac type phenol formaldehyde oligomers based on crystalline phenol and gaseous formaldehyde, as well as a method for synthesizing modified phenol-formaldehyde oligomers, using a eutectic mixture of phenol and naphthalene instead of pure phenol. Optimal conditions for the polycondensation process have been investigated as well as some kinetic features of the formation of phenol alcohols. It is shown that a cooling regime (25±3°) provides optimal temperature conditions for the first stage of the polycondensation.

Effect of the structure of phenolformaldehyde oligomers on their interaction with aluminium γ-oxide

When forming adhesive compounds of rubber with metal during vulcanization adsorption of adhesive on the metal surface may be of considerable significance; this process precedes adhesive interaction. The type of adsorption determines to a large extent the strength of the adhesive bond of the polymer with the substratum and the structure of boundary layers. Novolac and resole type phenolformaldehyde oligomers of different structures were synthesized and their adsorption properties examined on aluminium γ-oxide powder, which simulates the surface of the aluminium substrate.

Weak donor-acceptor complexes of o-quinone diazides with phenol-formaldehyde oligomers

It has been shown by low-temperature photolysis and ESR that mixtures of o-naphthoquinone diazides with phenol-formaldehyde oligomers in solutions and dry films form weak donor-acceptor complexes in which the intramolecular photoreduction of the o-naphthoquinone diazide can take place.

Reverse-Phase Liquid Chromatography of Phenol-Formaldehyde All-Ortho Oligomers

Abstract High Performance Liquid Chromatography was proven to be a powerful method for the separation and quantitation of ortho-linked Phenol-Formaldehyde oligomers. A homologous series of oligo [(2-hydroxyl-1, 3-phenylene) methylenes] (dinuclear to octanuclear compounds) was analyzed. The samples were separated by reverse-phase chromatography and monitored at 280 nm. Optimum conditions were obtained on a μ-Bondapack C18 column employing isocratic ambient elution with a metanol/water 80:20 (v/v) mixture. Four reference mixtures of oligomers of known composition were used to assure the reliability of the method. Subsequent analysis of two samples of all-ortho novolac resins was performed in order to substantiate further the validity of the technique.

Properties of polycaproamide yarns modified with Novolak phenol formaldehyde oligomer

Properties of polycaproamide yarns modified with Novolak phenol formaldehyde oligomer

Radiation curing of phenolformaldehyde oligomers

Information about the chemical reactions which take place during the exposure of phenolformaldehyde oligomers (PFO) to high energy radiation has been sought in the radiation curing studies by IR spectroscopy, ESR and by quantitative determinations of the gel fractions. The mechanism of the radiation curing was found not to differ substantially from that of the thermochemical process. The progress of the process has been found to be more intense in the presence of sensitizing agents, but there was no change in its character.

Structural characteristics of phenol-formaldehyde novolak oligomers

The results of the composition and structural determinations for phenol-formaldehyde Novolak oligomers have been compared by means of theoretical and experimental methods. The former is based on the probability theory in a combination with the Monte Carlo method, the latter on 13C-NMR spectroscopy. Both these methods were found to give similar results.

Structural changes in elastomers during their reactions with alkylated phenolformaldehyde oligomer and ϵ-caprolactam

The structural changes have been studied in elastomer compositions based on butadiene-styrene and polyisoprene rubbers modified with ϵ-caprolactam and the alkylated phenolformaldehyde oligomer. The reaction of the elastomer with the oligomer in the presence of ϵ-caprolactam is thought to have a radical mechanism. IR spectroscopy and high resolution NMR have shown chroman structures of polycaproamide, cis- trans-isomerization and cyclizations. The presence of all these products in the studied systems indicates that complex heterogeneous processes take place in the elastomer matrix and that an amide-type vulcanization system with good physico-mechanical properties forms, as a result of these.

Stress Relaxation of SBR Vulcanizates with Various Crosslinking and Modifying Agents

Abstract From the results of the investigation on stress relaxation in air of vulcanizates based on SBR containing ε-caprolactam and alkylated phenol formaldehyde oligomer, the following conclusions can be made : 1. ε-caprolactam has an effective action as an accelerating and modifying agent leading to vulcanizates of improved behavior in stress relaxation at temperatures up to 120°C. The characteristics of the vulcanizates deteriorate at higher temperatures because of the strong temperature dependence of the rate constants of thermo-oxidative aging processes. 2. ε-caprolactam in combinations with Vulkacit CZ or Captax added in recipes of SBR leads to improved relaxation properties of the vulcanizates at low temperatures and to a lower resistance to aging at higher temperatures. 3. The vulcanizate containing the crosslinking and modifying group of alkylated phenol formaldehyde oligomer with ε-caprolactam is characterized by its highest thermostability at high temperatures in comparison with all tested compositions, and by relaxation properties at low temperatures comparable to those of the compound with Captax (Table II). 4. The relaxation curves are comparatively well described by the Berry equation for simultaneous occurrence of breakdown processes for several kinds of crosslinks by first-order reaction. 5. The slow stage of physical relaxation is described by a sum of several exponential processes with relaxation times characteristic of each composition, i.e., the various accelerators and modifying additives have a strong effect on the supermolecular arrangement of the network of vulcanizates made of SBR (Bulex).

Effect of powdered mineral fillers on the crosslinking of phenol-formaldehyde oligomers and the mechanical properties of the molding materials

By investigating the effect of various powdered oxides on network formation in phenolformaldehyde oligomers, it has been established that nonionogenic oxides increase the number of network defects in proportion to the surface energy of the powder. Small amounts of ionogenic oxides with a divalent cation cause the formation of new ionic or ionic-coordination linkages in the polymer network. The effect of mineral powders on polymer network formation is correlated with the mechanical properties of molding materials based on phenol-formaldehyde polymers with different network densities.

Thermal decomposition of phenol formaldehyde resins modified with cyanuric acid

AbstractThe thermal decomposition of cured cyanurophenol—formaldehyde oligomers (CPFR) was studied by derivatography, IR, spectra and EPR spectra. During the heating of CPFR, processes of restructuring and decomposition take place. Up to 330°C the weight losses of CPFR are smaller compared to those of phenol–formaldehyde oligomers (PFR), while above 330°C the opposite is true. Under these conditions the isocyanuric ring is destroyed. The carbonyl absorption sharply decreases at 400°C, and at 500°C there is practically no absorption. This reduction is probably a result of rearrangement of the isocyanuric rings to a secondary polymer in which nitrogen is combined in the form of cyanic links. The energy of decomposition as determined from the thermogravimetric curve is 17 to 24 kcal/mole. On the basis of the EPR sepctra and the low activation energy of destruction, we propose that radical processes play an important part during the process of curing and thermal decomposition of CPFR.

Formation of network polymers by the polycondensation of phenolformaldehyde oligomers

Formation of network polymers by the polycondensation of phenolformaldehyde oligomers