Polypropylene Layers Research Articles

Assessment of the damage zone in a glass mat-reinforced thermoplastic polypropylene (GMT-PP) by infrared thermography

Hot stampable glass mat-reinforced thermoplastics (GMT) with polypropylene (PP) matrices are widely used in different structural applications. Reports about their mechanical characteristics have appeared recently [1-3]. Less work has been devoted to the failure behaviour of GMT-PP [4-6]. The assessment of the size of the damage zone in notched GMTs is an important topic at present [6, 7]. The attention shown to this matter can be attributed to two facts. Firstly, there is a strong need to provide designers with reliable mechanical values of GMTs. This task can only be achieved after clarifying how the specimen size affects the related mechanical response. On the other hand, the size requirements of the specimens obviously depend on the extent of the damage zone that arises during the loading. Secondly, the size of the damage zone reflects the load distribution and transfer in the material. Thus, it is believed that assessment of the damage zone is a very useful tool for checking the efficiency of different upgrading methods, such as needlepunching of the reinforcement, surface-treatment of the glass fibre (GF) mat, use of polymeric coupling agents in the matrix and the like. It is assumed that investigations on the damage growth and failure characteristics involved can strongly contribute to the development of GMT-PPs with tailored mechanical performance (e.g. stiffnesstoughness balance). The aim of the present work is to estimate the size of the damage zone and follow its change by infrared thermography (IT) in GMT-PP. The GMT-PP investigated was produced by pressing a needle-punched, unconsolidated textile preform consisting of continuous GF swirl mat and non-woven PP layers. The volume fraction (Vf) of the GF mat and PP layers were approximately 20 and 30 vol %, set by stacking the reinforcing mat and PP matrix non-woven layers. Consolidations of this textile preform occurred by hot pressing at different conditions (temperature, pressure). Further details about the material and its consolidation are given in [7, 8]. Single-edge notched (SEN) specimens, cut from the pressed plates, were loaded in tensile mode at v = 1 mmmin -1 crosshead speed at room temperature (RT) on a Zwick 1445 machine. The width (W) and clamping length of the specimens were 60 and 100 mm, respectively; the depth of the notch (a) was set at a/W = 1/3. Fracture of the specimens was studied in situ, i.e. during loading, by IT using a Hughes thermal video system. Its spectral wave-

Laminated polypropylene material ? A new form of floor covering

-- An efficient technological process has been developed for preparing an ecologically clean floor covering, which is a nonwoven polypropylene needle-punched material laminated with polypropylene film. In the preparation process, an extrusion method is used for applying a face layer of thermoplastic polypropylene using a slot-like spinneret. The nonwoven needle-punched material is produced from a melt of granulated polypropylene with aerodynamic stretching of the fibers on an LPP-2400GT line. The floor covering can be made with a design applied on the base (nonwoven material) or with coloring the face layer in bulk.

鋼板とポリプロピレンの接着における分子量の効果

This study is concerned with the peel strength of laminated steel plates constituted of two steel plates and a plastic sheet. Sufficient bonding between steel plate and polypropylene is required for application of this material. In this paper, the effect of molecular weight of polypropylene on adhesion was mainly investigated on the laminated steel plate.Two steel plates were adhered with a polypropylene sheet by using a mixed adhesive which composed of a silane coupling agent and peroxide, and adhesion strength was determined by T-peel test. The fracture surface created by peeling was observed by scanning electron microscopy (SEM), and its elemental composition was determined by electron spectroscopy for chemical analysis (ESCA).The extent of deformation of peeled surface in the polypropylene side increased with peel strength. It was concluded by ESCA analysis that failure occured within the oxidized polypropylene layer, namely, by cohesive failure. T-peel strength became larger with increasing molecular weight of polypropylene. This result suggests that the peel strength depends on the force of drawing out of polymer chains.

The Interlaminar Bond Strength of Flexible Polymer-Metal Laminates

Abstract An alternative test method to the traditional 180° “T” peel test has been developed for the measurement of interlaminar bonding in three-ply (polyester/aluminium/polypropylene) flexible-packaging, laminate materials. The new test is thought to involve mixed mode I (opening) and mode II (shearing) failure, and takes into account the yielding of the polypropylene layer during testing. The method allows more direct comparisons between materials to be made, and allows the measurement of strong bonds, where a peel test would result in yield or fracture of the substrate arms before debonding.

Mechanical properties of ultrahigh molecular weight polyethylene-polypropylene blend films produced by gelation/crystallization from solution

Films of a polyethylene-polypropylene blend were prepared by gelation/crystallization from semidilute solutions using ultrahigh molecular weight polyethylene ( M v = 6 × 10 6 and polypropylene ( M v = 4.4 × 10 6). The polyethylene/polypropylene (PE/PP) compositions chosen were 75 25 , 50 50 and 25 75 . The elongation was carried out in a hot poly(ethylene glycol) oil bath at 140°C. The mechanical properties of the resultant gel films were dependent upon the PE/PP compositions at each draw ratio. This interesting phenomenon is discussed using the second-order orientation factors of the c axes of polyethylene and polypropylene within the blend films. It turns out that the orientation factors of the polyethylene and polypropylene phases within the blend films at each draw ratio are different from those of their individual homopolymers with the corresponding draw ratio and this tendency is pronounced for blend films with a draw ratio of 20. Therefore, it is insufficient to explain the dependence of PE/PP composition on the storage and loss moduli by a composite law based on a simple model system in which polyethylene layers lie adjacent to polypropylene layers with the interfaces parallel and perpendicular to the stretching direction and the morphological properties of the two phases within the blend films are equivalent to those of their individual homopolymers at each draw ratio.

The mechanical properties of glass/polypropylene multilayer laminates

Multilayer laminates have been fabricated from thin sheets of glass and polypropylene. By the use of a special surface treatment applied to the glass surfaces, fully transcrystalline polypropylene layers could be formed. This facilitated the interpretation of the mechanical properties of the laminates in terms of the microstructure of the polymeric layers. It was found that the presence of transcrystalline layers leads to modest increases in flexural modulus and strength, and strain energy release rateGc. These laminates can be valuable models for the mechanical properties of fibre-reinforced thermoplastics.

DESTRUCTION OF MICROORGANISMS AND DEFORMATION OF PLASTIC JARS BY HOT SORGHUM SYRUP

ABSTRACT Sweet sorghum syrup was heated at 49° to 71°C and filled into glass jars of 200 mL capacity that contained each of four microorganisms (Bacillus subtilis; Byssochlamys nivea; Saccharomyces rouxii; and Aspergillus niger) at 0, 1,000 or 10,000 CFU/mL syrup. Counts were determined on syrup immediately after filling into the jars and after four months storage. The heated syrup at all temperatures significantly reduced the survival of bacteria and fungi at the time of filling. After four months, no bacteria could be detected in syrup at each temperature, and no fungi could be detected at 66° and 71°C. The heat of syrup at 71°C or lower did not cause single layer polypropylene jars to become deformed; however, at 77° and 82°C deformation occurred such that the jars were unsatisfactory for the packaging of syrup. Therefore, syrup can be filled at 66° and 71° into single layer polypropylene jars. At these temperatures, common spoilage microflora were destroyed or inactivated during storage, and the plastic jars did not become deformed.

Coextruded Microlayer Film and Sheet

Multilayer coextrusion can be used to produce microlayer films which can be designed to provide unique characteristics. Based on the optical theory for the wave length of reflected light from the normal incidence, 400 alternating layers of poly carbonate (PC) and polypropylene were coextruded with the expected result that the 25 μm film blocked over 80% of the UV light while transmitting 80% of the visible light. Ultrathin PC films (2 μm thick), made by delaminating multilayer extrusions, had DC breakdown voltages similar to solution cast films of the same thickness. Increase of the number of microlayers of PC/styrene-acrylonitrile composites resulted in improved tensile and impact strength—with a notable reduction in notch sensitivity for the latter property.

COALESCENCE OF SECONDARY DISPERSIONS IN COMPOSITE PACKED BEDS

ABSTRACT Oil water dispersions have been separated efficiently using composite beds made up of several materials. Selection of these materials was based on their wetting properties and fibre size. A bed composed of three layers: two fibre glass layers of different sizes followed by woven layer of polypropylene and stainless steel was found to give the best results.

Skin‐Core morphology and failure of injection‐molded specimens of impact‐modified polypropylene blends

AbstractThe structure‐property relationship as well as the failure phenomena of injection molded polypropylene (PP) blends modified with ethylene/propylene/diene terpolymer (EPDM) and thermoplastic polyolefinic rubber (TPO) were investigated. Single and double‐gated tensile bars were injection molded by different Injection speeds. Microscopic studies on the failure behavior of knit lines were carried out using microtomed sections taken from the doublegated specimens. It was found that during injection molding, a skin‐core morphology is formed in both the continuous PP matrix as well as in the modified PP blends containing rubber particles of various deformation. The characteristics of the latter are in agreement with those described by the Tadmor flow model. The skin consists of a thin pure PP layer, whereas the subsurface layer contains more or less elongated rubbery particles due to the elongational flow at the wall. The deformation of the rubbery particles decreases, but their concentration increases with increasing distance from the skin towards the core. The deformed particles are oriented tengentionally to the flow front profile. Failure during tensile and tensile impact loading is initiated in the shear zone along the skin‐core boundary. This zone has a transcrystalline character and favors the formation of crazing. Final fracture of the bars depends, however, on how crazing and shear yielding simultaneously interact. Their interaction is a function of the average particle size of the dispersed phase. Above an average particle size of 0.6 μm, crazing is prevented by shear bands. For injection molding of PP/rubber blends a moderate injection speed is recommended, if the melt viscosities of the components are closely matched. In this way a pronounced dispersion gradient of the rubber particles across the plaque thickness is avoided. However, for the blends modified with rubber of high viscosity ratio and greater melt elasticity, use of higher injection speed is advantageous. Here, the higher shear stress field decreases the average particle size taken into the direction perpen dicular to the lead, since the cross section of the stronger deformed particle decreases.

On the Mechanism of Aluminum Corrosion in Metallized Film AC Capacitors

Metallized film capacitors consist of alternating layers of polypropylene or other polymeric film dielectric and vapor deposited aluminum conductor. During operation above 250 V ac (RMS), circular islands of oxide develop in the aluminum conducting layers and reduce the capacitance. Increasing the aluminum layer thickness to more than the normal value of about 30 nm reduces the corrosion problem. The removal of moisture stops corrosion. Corrosion increases with temperature, ac voltage, and frequency to 3.5 kHz. A dc field, equivalent to the peak ac field, cannot initiate or sustain the corrosion process. These observations are consistent with a mechanism of anodic oxidation at the edge of defects in the aluminum layers. These discontinuities in the aluminum must be sufficiently large to enhance the local electric field and sustain ionic transport in the oxide. Fibrils on the polymer-film surface, and both electrical and electrochemical self-healing processes, are the most probable sources of corrosioninitiating conducting-layer defects.

Determination of the thermal diffusivity and thermal conductivity of layers of polypropylene and polyamide fibers

The proposed procedure for measuring and calculating coefficients of thermal diffusivity and thermal conductivity makes it possible to raise considerably the accuracy in determining these quantities for fibrous materials.

Transmission of woven scrim polypropylene laminate material between 2 and 500 μm: A low-cost, robust filter for solar FIR studies

A polypropylene scrim laminate material, Griffolyn GW24, consisting of a coarse weave of translucent polypropylene sandwiched between layers of white and black polypropylene, has been investigated as a filter for FIR solar studies. This combination has been shown to exhibit good FIR transmittance while rejecting near i.r. radiation. Filter heating in solar applications is reduced by the reflection of visible and near i.r. radiation by the white polypropylene layer. Its physical properties of durability over a wide temperature range, high tear resistance and strength and high u.v. tolerance further enhance its value as a primary filter for the above purpose.

A possible mechanism for the formation of polyolefin blends

IR spectroscopy by attenuated total internal reflection (ATR) electron microscopy and differential scanning calorimetry have been used to investigate the surface morphology of polymer powder obtained by the successive polymerization of propylene and ethylene in the presence of the catalyst Al(C 2H 5) 2ClTiCl 3. It has been shown that PE, during polymerization in the second stage, deforms the layer of polypropylene (PP) formed previously, disrupts it and penetrates to the particle surface. A similar phenomenon is also observed when PP is formed in the second stage, the PP penetrating through the layer of PP formed previously.

Physiological Responses and Thermal, Humidity, and Comfort Sensations in Wear Trials with Cotton and Polypropylene Vests

Relations were studied between skin temperature of the back as well as temperature and humidity inside clothing, and subjective estimates of thermal, humidity, and comfort sensations in 5 subjects wearing cross-country ski dress. The 2-h wear trials were performed in a climatic chamber at −2°C and simulated the actual circumstances under which such a dress is worn by alternating periods of intensive walking (20 min) on a treadmill with periods of resting (5–10 min). Each subject participated in 4 trials wearing alternately one of the 4 experimental, double-layer vests (double-cotton, cotton-polypropylene with cotton layer next to skin, same combination with polypropylene layer next to skin, double-polypropylene). Skin temperature of the back was during the experiments systematically lower ( P<0.05) by about 1°C with the double-layer cotton vest than with the double-layer polypropylene vest. Since the physical parameters of the two fabrics were not identical, the findings cannot be definitely attributed to the inherently different properties of the fibers. No significant differences were found in the 4 experimental series either in other objective measurements (temperature and humidity of the microclimate, energy output, total amount of sweat, amount of sweat trapped in the vests) or in subjective estimates of thermal, humidity, and comfort sensations. Gradual increase of skin temperature as well as of temperature and humidity (sweating) of the microclimate was recorded during walking periods. When walking was interrupted by a pause, both the temperature and humidity rose steeply, due to the cessation of bellows ventilation of the clothing, and fell again when walking was resumed. The thermal and humidity sensations on the back reported after the turning-points of the intermittent activity showed opposite direction of changes than those of the recorded parameters— i.e., decrease during pauses and increase after walking was resumed. It is possible that the perception of local sensations was affected by superimposed, central perception of changes in the amount of heat delivered from muscles to the brain receptors. The sensations of comfort seemed to be affected mostly by perception of “warmth” when walking and “cold” when resting.