A. N. Banerjee

Short jute fiber-reinforced polypropylene composites : Effect of compatibilizer

Jute fibers were chopped to approximately 100 mm in length and then processed through a granulator having an 8-mm screen. Final fiber lengths were up to 10 mm maximum. These fibers along with polypropylene granules and a compatibilizer were mixed in a K-mixer at a fixed rpm, 5500, and dumped at a fixed temperature, 390°F, following single-stage procedure. The fiber loadings were 30, 40, 50, and 60 wt %, and at each fiber loading, compatibilizer doses were 0, 1, 2, 3 and 4 wt %. The K-mix samples were pressed and granulated. Finally, ASTM test specimens were molded using a Cincinnati injection molding machine. At 60% by weight of fiber loading, the use of the compatibilizer improved the flexural strength as high as 100%, tensile strength to 120%, and impact strength (unnotched) by 175%. Remarkable improvements were attained even with 1% compatibilizer only. Interface studies were carried out by SEM to investigate the fiber surface morphology, fiber pull-out, and fiber–polymer interface.

Short jute fiber-reinforced polypropylene composites: Dynamic mechanical study

Short jute fiber-reinforced polypropylene (PP) composites were prepared using a high-speed thermokinetic mixer. A compatibilizer was used to improve the molecular interaction between jute and PP. Both the percent weight fraction of the jute fiber and compatibilizer were varied to study the dynamic mechanical thermal (DMT) properties. Dynamic parameters such as storage flexural modulus (E′), loss flexural modulus (E″), storage shear modulus (G′), loss shear modulus (G″), and loss factor or damping efficiency (tan δ) were determined in a resonant frequency mode. The transition peak nature, amplitude, and temperature of E′, E″, G′, G″, and tan δ of different compositions were shown to indicate possible improvements of molecular interaction in the presence of a compatibilizer. The modulus retention term, a plot of the reduced modulus with the weight fraction of the jute fiber, also indicate its improvement.

Jute sliver-LDPE composites: Effect of aqueous consolidation on mechanical and dynamic properties

The aqueous consolidation of jute slivers and its comparison with the control in the LDPE matrix were studied in this article. The increase in strength of the consolidated jute sliver–LDPE composite was noticed. Jute slivers were immersed in water, squeezed, air dried, and finally consolidated at 160°C for 5 min. These treated jute slivers with or without CSM (chopped strand mat) and LDPE films were compression molded to different boards and compared among themselves. The studies undertaken for characterization and analysis of the system were (a) flexural behavior, (b) tensile behavior, (c) impact behavior, (d) DMA study, and (e) SEM study. Among mechanical properties maximum gain was found in the impact strength. In the SEM study splitting of fibers were observed after consolidation.

Role of methods of blending on polymer–polymer compatibility

The role of methods of blend preparation on polymer-polymer compatibility was investigated. Three different types of methods of blending, such as solution-casting, melt-mixing, and coprecipitation, were applied for three types of blend systems, viz., poly(vinyl chloride-co-vinyl acetate) (VYHH)/polystyrene (PS), VYHH/poly(styrene-co-acrylonitrile) (SAN), and VYHH/poly(methyl methacrylate) (PMMA) by measuring their glass transition temperatures (Tg) by a differential scanning calorimeter (DSC). It has been found that compatibility of the polymers depends on the method of blending and compatibility also varies from one blend system to another. Among the various types of blending methods, the coprecipitation method of blending gives the best compatibility result.

Study of fire retardancy and thermal stability of vinyl acetate‐2‐ethylhexyl acrylate copolymer by blending with amino resin in aqueous medium

Trimethoxymethyl melamine (TMMM) and hexamethoxymethyl melamine (HMMM) were blended with the widely used acrylic medium, the copolymer of vinyl acetate and 2-ethylhexyl acrylate (VAc-EHA), for preparing water-based blends having improved fire retardancy. The weight fraction of the VAc-EHA copolymer was varied from 40 to 95%, at the pH value of 7 and a solid content of 50% was kept in all cases. The limiting oxygen index (LOI) and char yield of the blends were evaluated and the surface morphology of TMMM, HMMM, and the VAc-EHA copolymer at room temperature and at 110, 340, and 550°C was also studied to explain the improvement in the fire-retardancy behavior of the blends. The LOI and char yield of the VAc-EHA copolymer was found to improve substantially on incorporation of both TMMM and HMMM. But due to the limited stability of TMMM in aqueous medium, HMMM is more suitable for blending with VAc-EHA, to give a water-based coating having good fire-retardancy properties.

Heat-distortion temperature of unidirectional polyethylene–glass fiber–PMMA hybrid composite laminates

Unidirectional (UD) composite laminates based on high-performance polyethylene fibers (PEF) and glass fibers (GF) and their hybrids were prepared with partially polymerized methyl methacrylate (MMA) at room temperature, followed by heating at 55°C (well below the softening point of PEF, 147°C) for 2 h. The heat distortion temperatures (HDT) of the composites were measured and analyzed. The dependency of the HDT correlated with the wettability of the fibers, measured from the contact angle. The HDT of the composites increased with increasing GF content but decreased when PEF was used. An optimum combination of different properties was obtained by using PEF/GF/PMMA hybrid composites, with GF ply/plies on the lower tension side of the UD laminates.

Rheological studies of the poly(styrene-co-acrylonitrile and poly(vinyl chloride-co-vinyl acetate) blends

The rheological studies of the poly(vinyl chloride-co-vinyl acetate) and poly(styrene-co-vinyl acetate) and poly(styrene-co-acrylonitrile) blends were performed by a Brabender Rheotron at three different temperatures and also at different shear rates. Flow curves of the blends at different temperatures were drawn. The flow behavior index and, also, zero-shear viscosity of the blends at different temperatures were determined. From the flow curves, it has been found that as shear stress increases, melt viscosity decreases at all temperatures, indicating that pseudoplastic behavior and experimental values lies above the line of the log-additivity value and below the line of the additivity rule of mixture.

Fourier transform infrared spectroscopic studies of the poly(styrene‐co‐acrylonitrile) and poly (vinyl chloride‐co‐vinyl acetate) blends

The Fourier transform infrared (FTIR) spectroscopic studies of the poly-(styrene-co-acrylonitrile) (SAN) and poly(vinyl chloride-co-vinyl acetate) (VYHH) blends produced by different blending techniques, viz., solution blending, melt-blending, and also the co-precipitation methods of blending, were performed. In the case of miscible blend systems, substantial band shiftings took place, whereas immiscible blend systems showed slight or no band shifting. The miscible blends showed a substantial residual spectrum which was absent in the case of the immiscible system when a similar subtraction process was carried out.