P. Järvelä

Melt rheological properties of polypropylene-maleated polypropylene blends. I. Steady flow by capillary

Melt rheological properties of blends of polypropylene (PP) and PP grafted with maleic anhydride (PP-g-MA) are studied using a capillary rheometer. A pseudoplastic flow behavior is observed. The pseudoplasticity of the melt reduces with an increase of PP-g-MA content and/or temperature. The PP-g-MA component in the blend acts as decreasing melt viscosity, especially in the lower shear rate region, while the addition of PP-g-MA to PP does not cause obvious increase of die swell ratio.

The three-fibre method for measuring glass fibre to resin bond strength

Abstract This paper presents a method developed to measure the bond strength of a fibre/resin bond. Equipment has been developed to enable the test to be carried out in a normal tensile testing machine, and the results to be followed by scanning electron microscopy. Bond strengths obtained by this method are in agreement with earlier results. There are, however, some problems related to the method, including reproductivity of the test, determination of the degree of polymerization of the resin and the use of very thin fibres. However, the method has been proved a very quick and relatively accurate indicator of the strengths of fibre/resin bonds.

Dynamic mechanical and mechanical properties of polypropylene/poly(vinyl butyral)/mica composites

Three-component composites consisting of polypropylene (PP) matrix, poly(vinyl butyral) (PVB) modifier, and mica filler at various ratios of matrix to modifies and a constant mica content (30 wt %) were prepared by using two different kinds of PVB, viz., PVB and PVB-P. By correlating with the morphology, the dynamic mechanical and mechanical properties of the composites are studied in detail. PVB component in PP/PVB/mica composites cannot display a reinforcing effect to PP/mica binary composites, while impact strength of the composites are reduced further. It associates with incompatibility between PP and PVB, and as well as higher glass transition temperature of PVB. For PP/PVB-P/mica composites, stiffness decreases and, meanwhile, impact strength increases when PVB-P content is 7 wt %. The improvement of impact strength on PP/mica binary composites at the composition is due to a little affinity between the PP matrix and the plasticizer of PVB-P. Moreover, a minor amount of PP-g-MA in the 63/7/30 PP/PVB/mica composites only acts as an adhesion promoter.

Mechanical and tribological property comparison of melt-compounded nanocomposites of atomic-layer-deposition-coated polyamide particles and commercial nanofillers

Mechanical and tribological properties of melt-compounded titanium dioxide nanocomposites of atomic-layer-deposition (ALD)-coated polyamide particles and commercial nanofillers were compared. The nanofiller dispersion in the polyamide matrix was studied using transmission electron microscopy showing very different morphology for the ALD-created and the traditional nanocomposites: former appearing as ribbons in the matrix whereas latter composing from spherical clusters. The effect of such morphology change on the specimen’s mechanical response subjected to tensile and impact loading was investigated. The results demonstrated that ALD-created nanocomposites possess significantly higher Young’s modulus than pure and traditionally filled polyamide matrix. However, transition from ductile to brittle behavior occurs especially for the ALD-created nanocomposites. Notched impact strength experiments supported this, suggesting that the impact strength of ALD-created composites decreased significantly compared to ...

Coating plywood with a thermoplastic

This work presents a method for the surfacing of wood sheets such as plywood with melt processable thermoplastic using extrusion coating. The method uses a direct coating of the plywood with a very hot low-viscosity coating. During the coating, the pressure of the melt is kept as low as possible. These factors produce a very high mechanical adhesion between the coating and the wood. In addition, the coating method uses a tool for preventing the formation of holes in the surface by the penetration of air expanding and water evaporating from the wood pores through the coating. In this work the method was applied to coating plywood with a copolymer of polypropylene. The adhesion between the wood and the polypropylene was improved by blending the polypropylene with maleated polypropylene wax. The experiments showed that the method produces sound and smooth polypropylene coated plywood. Addition of a modifying agent improves the adhesion between the polypropylene and the wood.

Polyamide 6/wollastonite composites: Strength properties and their dependence on humidity and temperature

The use of wollastonite as a reinforcement for polyamide 6 (PA 6) composites was evaluated using various mechanical test methods. The results suggest that wollastonite acts as a reinforcement for PA 6 at concentrations in the range 25 to 40 wt%, because it increases strength, stiffness and impact strength. Increases of 20 to 200% in these properties were obtained for these wollastonite concentrations. This reinforcing effect was observed when the composite was not exposed to any humidity or temperature treatment; such treatments were found to cause a deterioration in interfacial adhesion as concluded from scanning electron microscopy observations. In conclusion it seems that the present surface treatment system of the wollastonite may be improved and so better the long-term properties of PA 6/wollastonite composites in severe conditions. The short-term tests, however, show that the wollastonite reinforces PA 6, i.e. increases the strength, stiffness and impact strength when it is not exposed to any humidity or temperature treatments.

A method to measure the fusion strength between expanded polystyrene (EPS) beads

Cellular polystyrene (EPS) is the most commonly used cellular thermoplast whose main applications are insulation and packages. One of its new applications is core material in building elements, and this poses higher requirements for strength. This is particularly evident in self-supporting roof elements. This study presents a method for determining the fusion strength between beads in cellular polystyrene and the dependence of this strength on processing. This method has also enabled us to determine the adhesion of cellular polystyrene beads to other materials, such as glass fibre, and it allows measurement of the fusion strength between EPS beads without the influence of porosity. Fusion strength was found to have a characteristic behaviour. It has an absolute upper limit, and fusion forces approximate this limit asymptotically as heating time is prolonged (this increase is dependent on the energy content of the steam).

Mechanical strength and thermal stability of magnesium silicate filled polypropylenes

Mineral fillers are widely used to improve the mechanical properties of polypropylene, but at the same time they may cause some degradation of polymer, especially if the stabilization is insufficient. Two different kinds of silicate minerals, talc and serpentinite, were used as fillers for homo- and copolypropylene, and their influence on mechanical properties and degradation was investigated. The mechanical properties of filled polypropylene were tested at room temperature using tensile and impact tests. GC-MS technique was used to characterize the degradation of compounds. The results revealed differences in the mechanical properties: talc filled polypropylene had higher tensile strength, rigidity and impact strength properties than serpentinite filled. The oxidation stability of filled polypropylene measured by the oven method showed lower values in the case of serpentinite filled polypropylene. In the beginning of pyrolysis there was no significant difference between talc and serpentinite filled polypropylene in the formation of degradation products, as was observed by GC-MS. In a slightly higher temperature and longer incubation time PP-serpentinite compound started to form more small molecular weight degradation products than PP-talc due to stronger catalytical effects of the serpentinite surfaces. The characterization methods used here provided us new information to understand the role of mineral fillers in degradation processes. The results of DSC measurement yielded information on the effects of the filler crystallization and thermal degradation. Talc, for example, was shown to be better nucleation agent than serpentinite for PP.

The effect of moulding on the absorption of water in expanded polystyrene (EPS)

olystyrene foam is a common material, for instance, in the buildP ing industry. It is generally produced by two different methods. The most usual method is to expand polystyrene beads with blowing agent; expansion is completed in a mould where the beads are fused together into an integral piece. This material is generally known as expanded polystyrene (EPS) or moulded expanded polystyrene (MEPS). Another method to produce cellular polystyrene is extrusion. This material is known as extruded polystyrene foam (XPS) or extruded expanded polystyrene (XEPS). This article will concentrate on the material known as EPS (or MEPS). One typical application of expanded polystyrene (EPS) is thermal insulation. Moisture increases thermal conductivity markedly [1], which is an undesirable phenomenon. Expanded plastics are often used as

Determining the wetting properties of mica with LPR-90 equipment

Wetting and wetting rate measurements of a fine-grained mica were carried out by using the LPR-90 equipment. The mica samples had different kinds of surface treatment. It seemed that some significant differences could be observed as a function of the surface treatment agent and its concentration. According to the results, this equipment seems to be suitable for studying the success of surface treatments.