Mechanical Properties Of Isotactic Polypropylene Research Articles

Influence of benzoic acid on thermal, crystallization and mechanical properties of isotactic polypropylene under irradiation

Degree of super-cooling is denoted by the temperature difference between the melting temperature of the polymer T m, and peak crystallization temperature T p. Upon addition of progressively increasing amounts of benzoic acid (BA) to isotactic polypropylene {(is)-PP}, the degree of super-cooling was found to decrease, which leads to considerable reduction in moulding cycle time and savings in production cost. Haze % was found to progressively decrease with the corresponding increase in the amount of benzoic acid in (is)-PP, resulting in much improved transparency of the (is)-PP-benzoic acid blends. Irradiation to an absorbed dose of 25 kGy affected the transparency of blends slightly. Thermogravimetric analysis of (is)-PP-BA blends showed that there is no adverse effect on thermal stability of the polypropylene. Also, the irradiation of (is)-PP-BA blends did not bring about any significant changes in their thermal stability. (is)-PP-BA blends demonstrated, in general, improved tensile strength when compared to pure (is)-PP. Moreover, no significant detrimental influence of irradiation was observed on the tensile strength of (is)-PP-BA blends.

Thermal and dynamic mechanical investigations on fiber-reinforced polypropylene composites

The thermal behavior and dynamic mechanical properties of isotactic polypropylene (PP) and reactor blend PP/ethylene-propylene copolymer (EPM), reinforced with different amounts of short glass fibers (GF) and/or polyester fibers (PETF), were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermoanalysis (DMTA) of imposed tensile load on rectangular film specimens. DSC measurements exhibited an increase of the crystallization temperature of PP in the presence of fibers, but indicated no change in its percentage of crystallinity. DMTA spectra revealed an increase in the stiffness and a decrease of the damping with increasing GF content. The positions of the primary relaxations of PP and EPM did not change, but a significant broadening of the α-relaxation in the crystalline phase was observed, due to the induced reinforcement and interfacial interactions. The addition of PETF to PP enhanced its damping values at low temperatures and promoted the α-transition. The DMTA behavior was studied in dependence on the preconditioning and the frequency excitation. Heat treatment changed the characteristics of the β-relaxation of PP, due to enhanced molecular motion of the polymer segments. The variation of frequency affected the secondary relaxations considerably and, in the presence of GF, the glass transitions. For the different relaxations, activation energies from peak shift and loss peak areas were determined. Experimental data of loss peaks were fitted to phenomenological equations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1143–1154, 1997

Influence of mechanical properties in carbon black (CB) filled isotactic polypropylene (iPP) and propylene‐ethylene block copolymer

The mechanical properties of isotactic polypropylene (iPP) and propylene-ethylene block copolymer (Co-PP) with carbon black (CB) were added as a filler. By mixing appropriate amounts of the two components through melt-blending in a twin-screw extruder, the blended pellets were prepared to a series of test specimens by injection molding. A scanning electron microscopic study was performed of the morphologies of the impact fractured surfaces. The blending of CB in Co-PP not only improves the impact strength, but also improves the flexural modulus and tensile strength; however, the heat distortion temperature (HDT) of the Co-PP/CB blends decreased with greater filler content. Furthermore, the filler of CB improves the tensile yield strength only at low filler content in iPP/CB blends, and the heat distortion temperature (HDT) and flexural modulus of the iPP/CB blends increased with greater filler content. The impact behavior is not good for the iPP/CB blends. Overall, Co-PP/CB has better interaction of molecules than iPP/CB. © 1996 John Wiley & Sons, Inc.

Influence of mechanical properties in carbon black (CB) filled isotactic polypropylene (iPP) and propylene-ethylene block copolymer

The mechanical properties of isotactic polypropylene (iPP) and propylene-ethylene block copolymer (Co-PP) with carbon black (CB) were added as a filler. By mixing appropriate amounts of the two components through melt-blending in a twin-screw extruder, the blended pellets were prepared to a series of test specimens by injection molding. A scanning electron microscopic study was performed of the morphologies of the impact fractured surfaces. The blending of CB in Co-PP not only improves the impact strength, but also improves the flexural modulus and tensile strength; however, the heat distortion temperature (HDT) of the Co-PP/CB blends decreased with greater filler content. Furthermore, the filler of CB improves the tensile yield strength only at low filler content in iPP/CB blends, and the heat distortion temperature (HDT) and flexural modulus of the iPP/CB blends increased with greater filler content. The impact behavior is not good for the iPP/CB blends. Overall, Co-PP/CB has better interaction of molecules than iPP/CB. © 1996 John Wiley & Sons, Inc.

Relationship between morphology and mechanical properties of binary and compatibilized ternary blends of polypropylene and nylon 6

The effect of compatibilization on the morphology, mechanical properties, and dynamic mechanical properties of isotactic polypropylene (IPP)/nylon-6 (Ny-6) binary blends was investigated. Maleic anhydride (MAH) functionalized IPP was used as a compatibilizer in binary blends. The morphological, mechanical, and dynamic mechanical properties of binary and ternary blends were compared. The blends containing IPP-g-MAH showed more regular and finer dispersion of phases, different dynamic properties, and improved mechanical properties due to better adhesion between the two phases. The blends were also characterized for their flow properties and extent of water absorption. The melting peak temperature and percent crystallinity of IPP and Ny-6 phases were decreased in compatibilized blends. © 1996 John Wiley & Sons, Inc.

Temperature Dependence of Structural and Mechanical Properties of Isotactic Polypropylene

Finite-temperature simulations of crystalline isotactic polypropylene are carried out self-consistently using a molecular mechanics force field for the interatomic potential and quasi-harmonic lattice dynamics for the vibrational free energy. Negative axial thermal expansion is observed, in agreement with experiment, and is attributed to elastic coupling to the transverse thermal stresses. The axial elastic modulus decreases with temperature, due to entropic effects and as a consequence of transverse thermal expansion, which acts to increase the unstrained volume and move the system to a region of the potential energy surface with lower curvature. The transverse and off-diagonal elastic moduli decrease with temperature, due to a decrease in the curvature of the potential energy surface as the chains move apart with thermal expansion.

The production and properties of oriented polypropylene laminates

AbstractThe mechanical properties of isotactic polypropylene can be enhanced in one direction by a combination of rolling and drawing in a rolling mill. The longitudinal strength and modulus of the oriented polypropylene (OPP) increases with an increase in draw ratio; however, the transverse properties remain relatively unchanged. In this study, multidirectional OPP laminates [with (0)2, (0/90)s and (0/±45)s lay‐ups] were made to obtain sheet materials with improved properties in more than one direction in the plane. A hot‐plate welding technique was used to produce these translucent and recyclable laminates. The in‐plane properties of the laminates were successfully predicted with classical laminate theory (CLT), which is commonly used to predict the properties of fiber reinforced materials. These laminates can be quasi‐isotropic and were found to have improved modulus [up to 6 GPa for (0/90)s laminates] and strength [up to 150 MPa for (0/90)s laminates] as well as exceptionally good impact toughness.

Polyolefin blends: effect of EPDM rubber on crystallization, morphology and mechanical properties of polypropylene/EPDM blends. 1

Morphology, thermal behaviour and mechanical and dynamic mechanical properties of isotactic polypropylene (PP) blended with different amounts of ethylene-propylene-diene (EPDM) terpolymer were investigated. Addition of 10% (w/w) EPDM to PP resulted in an increase in spherulite size. Optical micrographs showed that the rubber was distributed both in the intra- and interspherulitic regions. The heat of fusion ( ΔH f) and percentage crystallinity (wide angle X-ray scattering) of PP/EPDM blends decreased on increasing EPDM content. Scanning electron micrographs revealed a skin-core morphology in injection-moulded specimens. Melt viscosity of the PP/EPDM blends determined at 200°C using a capillary rheometer showed an increase with increasing rubber content. A non-Newtonian flow behaviour was observed in the shear rate range 40–1600 s −1. Dynamic mechanical analysis results also supported the incompatibility of PP/EPDM blends. An improvement in impact strength of PP was observed upon incorporation of EPDM elastomer.

Some physical properties of polypropylene-phenolic microsphere blends

The effects of phenolic microspheres (PFM) on crystallinity and mechanical properties of isotactic polypropylene were studied. Isotactic polypropylene-PFM blends were formed by injection or moulding methods. The addition of PFM influences neither the degree of crystallinity of the polypropylene matrix nor the elastic properties of the composites. The specific work of deformation to yield decreases rapidly when the volume fraction of PFM exceeds 0.01.

Thermal history effects on the structure and mechanical properties of isotactic polypropylene of the J-400g rade. Part II

Thermal history effects on the structure and mechanical properties of isotactic polypropylene of the J-400g rade. Part II

Mechanism of the effect of a liquid medium on the mechanical properties of isotactic polypropylene

Mechanism of the effect of a liquid medium on the mechanical properties of isotactic polypropylene

Effect of liquids on type of failure and mechanical properties of isotactic polypropylene

Effect of liquids on type of failure and mechanical properties of isotactic polypropylene

Reversible change in the mechanical properties of isotactic polypropylene during large deformations and recovery

Reversible change in the mechanical properties of isotactic polypropylene during large deformations and recovery

Quantitative structural characterization of the mechanical properties of isotactic polypropylene

Abstract This investigation introduces quantitative morphological criteria for defining the structural state of a polymer sample and develops a general structural state deformation model for characterizing mechanical behavior. This general model discards the present fragmented view of the autonomy of observed mechanical processes (yielding, fracture, recovery, etc.) and brings the fabrication process, the mechanical tests, and even the construction of the sample (fiber or film) into focus as simply different aspects of a single process of deformation. The fabrication, fracture, yielding, and recovery behavior of two series of uniaxially drawn isotactic polypropylene films and two series of drawn isotactic polypropylene fibers, totaling thirty different structural states, have been deter-mined. The structural state of each of these samples is known quantitatively. The measurements were made over a range of strain rates from 1 to 1,000,000%/min and temperatures from 23° to -196°C. This study has resulted in...

Effect on the character of the breakdown of the spherulite structure on the mechanical properties of isotactic polypropylene over a wide temperature range

The mechanical properties of polymers are known to vary widely as a function of temperature. Since the supramolecular structures exert an influence over the mechanical properties of crystalline polymers, it has become desirable to study the variations in the spherulite structure during the deformation and rupture of a specimen over a wide temperature range, and compare these with the mechanical properties of a crystalline polymer.