Showing papers in "International Journal of Polymeric Materials in 1987"
TL;DR: The main feature of prehydrolyzed cellulose fibres is a high degree of brittleness, permitting the fibres to be finely comminuted in the shear field of normal compounding and processing machinery as discussed by the authors.
Abstract: This paper presents the results of an experimental study of the mechanical properties of composites consisting of prehydrolyzed cellulose and thermoplastic matrices. The main feature of prehydrolyzed cellulose fibres is a high degree of brittleness, permitting the fibres to be finely comminuted in the shear field of normal compounding and processing machinery. Such an effect can be anticipated to improve the homogeneity and the mechanical parameters of the moulded samples. In the present work, this has been demonstrated with PP, HDPE and PS containing varying amounts of prehydrolyzed cellulose of different origin (bleached pulps). The tests were done on injection moulded samples. The compounding method (Buss-Kneader vs. twin-screw extruder) had only minor influence on the results. Theoretical assessment of the modulus values using the Tsai–Halpin equation gave somewhat lower values than those recorded on experimental samples. This was interpreted in terms of the disintegration of the cellulose co...
143 citations
ARCO1
TL;DR: In this paper, the formation of polyester-rubber-polyester block copolymer is of determining importance, together with a very intimate dispersion of the rubbery domains, in the improvement of toughness.
Abstract: Thermosetting polyester resins obtained by polymerization of an unsaturated polyester and a vinyl monomer are known to suffer from certain disadvantages: for example, the impact strength of such materials is rather low. The impact behaviour of such resins may be significantly improved by the addition of suitable liquid rubbers bearing certain terminal chemical groups able to react with the base resin. We have found that the formation of polyester-rubber-polyester block copolymer is of determining importance, together with a very intimate dispersion of the rubbery domains, in the improvement of toughness. An investigation on the influence of formulation and composition, molecular mass of the rubber component, type of functional terminal groups, on the chemistry, morphology and curing behaviour of the prepared blends is reported.
14 citations
TL;DR: In this paper, the effect of a small amount of coupling agent (1.5phr) along with the filler reduces the viscosity of the system, and the coupling agent marginally increases the physical properties such as tear resistance, tensile strength, elongation at break and impact strength of filled systems.
Abstract: Mechanical properties and failure modes of blends of plasticized poly (vinyl chlroide) and copolyester thermoplastic elastomer have been studied with special reference to the effect of blend ratio, addition of silica filler and coupling agent. Incorporation of silica filler increases the hardness, modulus and tear strength of the blends. Tensile strength, elongation at break, impact strength and tensile set decrease with the addition of silica filler. Addition of small amount of coupling agent (1.5phr) along with the filler reduces the viscosity of the system. This enables economic processability. Moreover, the coupling agent marginally increases the physical properties such as tear resistance, tensile strength, elongation at break and impact strength of the filled systems. The effect of silica on the crystallinity of the samples has been investigated by X-ray diffraction studies. In order to study the mechanism of failure, tensile and tear failure surfaces have been examined by scanning electron...
12 citations
TL;DR: In this paper, the Flory-Rehner equation was used to calculate polymer-solvent interaction parameters for the blends of natural rubber (NR) with SBR and polybutadiene rubber (BR) by equating the network density of the vulcanizates in two solvents.
Abstract: Polymer-solvent interaction parameters for the blends of natural rubber (NR) with styrene-butadiene rubber (SBR) and polybutadiene rubber (BR) are calculated using the Flory-Rehner equation by equating the network density of the vulcanizates in two solvents.
11 citations
TL;DR: In this paper, the conductivity of polyphenylene sulfide sulphide sulphonic acid (PSS acid) was evaluated in the 20-160°C range with the following results: conductivity (ohm−1 cm−1) = 10−1 in 30% KOH aq., 10−2 in 5 atm steam pressure and 10−5 in air; transport number in KCl (t +) ∼ 1.
Abstract: Polyphenylene sulfide sulphonic acid is an amorphous, non melting solid which dissolves only in SOCl2, dehydrates at 40–180°C and degrades with heavy weight loss starting from 270°C. The polymer has been tested as solid state component of electrochemical devices in the 20–160°C range with the following results: conductivity (ohm−1 cm−1) = 10−1 in 30% KOH aq., 10−2 in 5 atm steam pressure and 10−5 in air; transport number in KCl (t +) ∼ 1. Possible applications are discussed in relation to the performance of other established material.
9 citations
TL;DR: In this article, the effects of two treatments, mercerization (NaOH-immersion) and benzylation, on the mechanical properties of a rubber-cellulose composite are reported.
Abstract: Both native and regenerated (rayon) cellulosic fibers are potential reinforcing elements in rubbers due to their relatively good mechanical properties, suitable aspect ratio, low cost and low density. The properties of the cellulosic fibers can also be changed fairly easily by chemical treatment. The effects of two treatments, mercerization (NaOH-immersion) and benzylation, on the mechanical properties of a rubber-cellulose composite are here reported. The rubber matrix was isoprene and the fiber content 20% by volume (27% by weight). Mercerization of bleached kraft fibers gave a composite with a higher modulus and strength than was attained when untreated kraft fibers were used, whereas benzylation of both kraft fibers and rayon fibers caused a reduction in the strength and stiffness of the rubber composites. This is interpreted as being due to a decrease in the degree of interaction between the cellulose fiber and the matrix due to the benzylation. The effect of these treatments on the mechanic...
9 citations
ARCO1
TL;DR: In this paper, the linear elastic fracture mechanism (LEFM) was applied to the prepared systems, to study their fracture behaviour, and interesting results were obtained when using a rubbery phase able to react with the base polyester leading to the formation of an A-B-A type block copolymer.
Abstract: Brittle thermosetting polyester resins are blended with low molecular weight liquid polybutadiene rubbers. The morphology of the rubber modified resins was investigated as function of the nature of terminal groups of the polybutadiene, either hydroxyl or isocyanate and as function of composition. The concepts of the linear elastic fracture mechanism (LEFM) were applied to the prepared systems, to study their fracture behaviour. Interesting results were obtained when using a rubbery phase able to react with the base polyester leading to the formation of an A-B-A type block copolymer.
7 citations
TL;DR: A carbon black filled 50/50 Natural Rubber (NR)/Polybutadiene Rubber (BR) blend is vulcanized using several conventional systems designed by varying the amounts of sulphur and accelerator as mentioned in this paper.
Abstract: A carbon black filled 50/50 Natural Rubber (NR)/Polybutadiene Rubber (BR) blend is vulcanized using several conventional systems designed by varying the amounts of sulphur and accelerator. The cure characteristics and the vulcanizate properties are compared. The quality and quantity of crosslinks in each case are deciphered by chemical probes to correlate them with the vulcanizate properties.
7 citations
TL;DR: In this article, the polyurethane/poly(n-butyl acrylate) interpenetrating polymer networks (IPNs) were obtained as tough films by transfer molding.
Abstract: Castor oil—a naturally occurring triglyceride of ricinoleic acid containing a special functionality of —OH group was reacted with hexamethylene diisocyanate to obtain liquid polyurethanes under different stoichiometric conditions varying NCO/OH ratio. These polyurethanes were then individually interpenetrated with n-butyl acrylate and ethylene glycol dimethacrylate as crosslinker by radical polymerization using benzoyl peroxide as initiator. The polyurethane/poly(n-butyl acrylate) interpenetrating polymer networks (IPNs) were obtained as tough films by transfer molding. These IPNs were characterized by their chemical resistance, thermal behavior (TGA, DSC), mechanical properties namely tensile strength, Young' s modulus, elongation at break (%) and Shore A hardness. The morphological behavior was analyzed by scanning electron microscopy and dielectrical properties namely, electrical conductivity (σ), dielectric constant (e′), dielectric loss (e″) and loss tangent (tan δ) at different temperature ...
5 citations
TL;DR: In this paper, it is realized that the rheological or stress deformation properties constitute the most important single factor for the failure of a polyblend system and that the distribution of fillers in the polyblender system exert a great influence on the Rheological properties.
Abstract: Processing is in large part simply flow and forming of compounds and thus the frequent breakdown in production line can be traced to causes like high viscosity or elastic memory of the compounds. Efficient and quality production require reproducibility in the processing stages and it is realised that the rheological or stress deformation properties constitute the most important single factor. Moreover distribution of fillers in the polyblend system exert a great influence on the rheological properties.1
4 citations
TL;DR: In this paper, structural investigations have been carried out in powder processed polyvinylidene fluoride containing various amounts of titanium dioxide and lead monoxide as fillers, and the crystallinity was found to increase significantly at very low filler concentration (< 3 percent, while it decreased monotonically with increasing filler concentrations above 5 percent.
Abstract: Structural investigations have been carried out in powder processed polyvinylidene fluoride containing various amounts of titanium dioxide and lead monoxide as fillers. The crystallinity was found to increase significantly at very low filler concentration (<3 percent) while it decreased monotonically with increasing filler concentrations above 5 percent. The phase transformation in the crystal structure was also noticed especially after sintering and the formation of beta phase was favourable in samples containing lead oxide. These various findings were also confirmed by infrared absorption studies and explained on the basis of deformation of the polymer during compaction together with preferential nucleation by the filler during the sintering step of the powder processing technique.
TL;DR: The effect of flame retardant compounds on the depression of glass transition temperature, cold crystallization temperature, and crystalline melting temperature (Tm) was examined by thermal analysis.
Abstract: The effect of five flame retardant compounds on the depression of glass-transition temperature (Tg), cold crystallization temperature (Tc), and crystalline melting temperature (Tm) was examined by thermal analysis. The depression of Tg by four of the compounds was linear. The depression of Tg by the fifth compound gave a plateau-type minimum which could be due to ‘super-saturation’ theory or a modification of Kovacs' theory.5