Abstract: The combination of organophillised montmorillonite (MMT), synthetic hydromagnesite and Al(OH)3 as flame retardant system for polyethylene-based materials was studied and compared with a similar system with Mg(OH)2, Al(OH)3 and MMT. The thermal stability and the flame retardant properties were evaluated by thermogravimetric anal. (TGA), DTA, limiting oxygen index (LOI) and cone calorimeter tests. The addn. of MMT can reduce the total filler content to achieve the flame retardant requirements. The thermal stability of filled LDPE/EVA blends increases to a higher extent for the samples contg. MMT. In the cone calorimeter tests we obsd. a redn. of the peak heat release rate for the sample contg. MMT in comparison with a sample with higher filler loading without this nanoclay. An increase in the stability of the char formed could be responsible for this favorable behavior when montmorillonite is added. In addn., mech. properties significantly improved for the composites contg. MMT both for the filler loading redn. and the reinforcement effect of the nanoclay. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: Novel polymer nanocomposite foams made by a two step compression molding method are analyzed in this article. Nanocomposites of low d. polyethylene and an organo-modified hectorite were first melt compounded and then foamed using a compression molding method. To study the influence of the presence and the amt. of hectorite in both mech. and thermal properties, samples with 3% and 7% content of hectorite were prepd. Polyethylene cryst. characteristics and thermal stability of the samples were studied by differential scanning calorimetry (DSC) and thermogravimetric anal. (TGA), resp. Mech. properties of foams and solid nanocomposites were analyzed by using dynamical mech. anal. (DMA). Thermal expansion of the samples was analyzed by thermomech. anal. The results indicate that the exfoliation of hectorite platelets was achieved after the foaming process, but not during the melt mixing step. Foams with hectorite nanoparticles exhibit improved thermal stability and mech. properties when compared with neat polymeric foams. Indexing -- Section 38-3 (Plastics Fabrication and Uses)

Abstract: The fracture behavior of glass microsphere-filled polypropylene/poly(ethylene terephthalate-co-isophthalate) blend-matrix composites was investigated in comparison with that of the glass microsphere-filled PP composites. Depending on the deformability displayed by the composite, it was carried out through the linear-elastic fracture mechanics or by applying the J-integral concept. The matrix ductility was regulated in the composite through the glass bead surface treatment applied with different silane-coupling agents, as well as with the addn. of maleated PP as polymer compatibilizer. Whereas all the composites failed in a brittle manner at moderate impact speed, quasi-brittle fracture behavior was only obsd. at low strain rate in composites having high and medium interfacial adhesion level. Results showed that composites contg. both aminosilane-treated glass microspheres and maleated PP showed the highest values of fracture toughness. In composites with low adhesion level between matrix and glass beads, the crit. J-integral value diminished due to the presence of PET. Indexing -- Section 38-3 (Plastics Fabrication and Uses)

Abstract: Hydromagnesite is a basic magnesium carbonate that undergoes an endothermic decompn. with water and carbon dioxide release in the temp. range of 200-550 C. Due to this thermal behavior it has been studied as flame retardant filler for polymers in cable applications. For this purpose the particle size distribution should be optimized, as it is in most cases responsible for decrease in final composite mech. properties. This work describes the variations found in the thermal behavior of hydromagnesite assocd. with the process of particle size redn. Air jet micronization was compared with mech. milling. Thermogravimetry and differential scanning calorimetry were used to study thermal decompn. FTIR spectroscopy and XRD anal. of the solid residue after heating were used to follow structural changes. Decompn. behavior of synthetic hydromagnesite was shown to be dependent of the applied particle size redn. process. A remarkable increase in the decompn. rate was obsd. for the milled sample, which was attributed to the introduction of defects in the cryst. structure during the mech. milling. Therefore, it was concluded that the mech. milling process may affect the thermal decompn. of hydromagnesite and therefore its characteristics as flame retardant. Indexing -- Section 37 (Plastics Manufacture and Processing)

Abstract: The authors present the compared anal. of the foaming behavior and cellular structure of LDPE/hectorite nanocomposites and resp. neat LDPE foams. To assess the influence of hectorite on the foaming behavior and final foam morphol., nanocomposites contg. 3 and 7% of a modified hectorite were first melt-compounded in a twin-screw extruder. Variables such as temp., pressure and time were optimized to prep. foams in a second stage by a two-step compression-molding process. Crystallinity and crystal structure of the polymer matrix were detd. using x-ray scattering (WAXS) and differential scanning calorimetry (DSC). Clay intercalation/exfoliation was analyzed by WAXS and transmission electron microscopy (TEM), with the results indicating that partial exfoliation of the particles was only reached with foaming but not during melt mixing. A quant. characterization of the cellular structure and morphol. of the foamed nanocomposites was done using both scanning (SEM) and transmission electron microscopies. The nanocomposite foams exhibited differences in the crosslinking degree, showing lower gel content values (from 35% of the neat LDPE to as low as 28% for the 7% hectorite foam), expansion behavior, cell aspect ratio, with the foamed nanocomposites showing more isometric type of cells, and cell wall texture with regard to the neat LDPE foams. All these differences, analyzed and compared for the three composites, directly affect both the thermal and mech. responses of the foams and due to that fact are of extreme importance. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: Recycled PET/organoclay nanocomposites were prepd. by melt intercalation process with several amts. (1, 3, and 5 wt %) of clay modified with quaternary ammonium salt (DELLITE 67G) dispersed in a recycled poly ethylene terephthalate (rPET) matrix. The resultant mech. properties (modulus and yield strength) of the nanocomposites were found to be different from those of rPET. Wide angle X-ray scattering and transmission electron microscopy measurements have shown that although complete exfoliation was not achieved, delaminated clay platelets could be obsd. Thermal anal. did not show significant changes in the thermal properties from those of recycled PET. Mech. testing showed that nanocomposite properties were superior to the recycled PET in terms of strength and elasticity modulus. This improvement was attributed to nanoscale effects and strong interaction between the rPET matrix and the clay interface. Indexing -- Section 37-6 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: The essential work of fracture (EWF) concept was successfully applied to the fracture toughness characterization of ductile glass microsphere-filled polypropylene (PP)-matrix composites. Injection-molded PP and PP/poly(ethylene terephthalate-co-isophthalate) (PET) blend-matrix composites filled with both untreated and silane-treated glass beads (50 wt%) were studied to ascertain the influence of the material compn. on the EWF parameters. In addn., the effect of the specimen thickness was also studied on deeply double-edge notched (DDENT) specimens of nominal thickness 1, 2 and 3 mm. The results indicated that the EWF methodol. could be applied to this kind of particulate-filled composites whenever high plasticity is developed in the crack tip front before the fracture propagation. PET addn. markedly reduced both fracture toughness and plastic work of fracture in untreated and mercaptosilane-treated glass beads, attributed to glass embedding by PET. Concerning specimen dimensions, a noticeable drop in fracture toughness was found in thicker samples, whereas plastic work of fracture showed the opposite trend. Indexing -- Section 37 (Plastics Manufacture and Processing)

Abstract: The effect of modifying the particle/matrix interfacial region on the morphol. and tensile behavior of glass bead-filled polypropylene (PP) composites was studied. The interface modification was promoted by blending PP with a small concn. (5% by wt.) of poly(ethylene terephthalate-co-isophthalate) (co-PET). Ten different PP/co-PET/glass beads ternary composites were prepd., characterized and compared with the homologous PP/glass beads binary ones. Maleic anhydride-grafted PP was added as a compatibilizing agent for PP and co-PET in some of the studied formulations, and its effect studied. Furthermore, four different silane-treated glass beads were used to prep. the composites (50 wt.%). Results showed that three different interfaces, corresponding to three different levels (low, middle and high) of particle/matrix adhesion, could be obtained in these composites by varying the matrix compn. and the silane coupling agent on the glass bead surface, which resulted in a wide range of tensile properties, from ductile composites with low tensile strength and high elongation to brittle ones with high tensile strength. It was found that co-PET embeds glass bead surface independently of the silane coupling agent employed. Finally, the adhesion degree differences between the different composite phases seemed to be the main cause to explain the differences found in the sensitivity of the composite tensile characteristics to the strain rate. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: Combined effects of clay treatment and compatibilizer polymers on the structure and properties of polypropylene (PP)/clay nanocomposites were studied. Dynamic mech. anal. was used to analyze comparatively the dynamic mech. response of different nanocomposites prepd. from polypropylene and montmorillonite-rich bentonite, and to relate such response with the material microstructure. Two different bentonites were used: a purified Spanish natural bentonite was organophillized by means of 11-undecyl-ammonium ion and a com. bentonite organophillized with di-Me dehydrogenated tallow ammonium ion. Three different polar copolymers were employed as compatibilizer agents in some of the formulations: maleic anhydride-grafted polypropylene, maleic anhydride-grafted poly(styrene-co-ethylenebutylene-co-styrene) (SEBS), and poly(ethylene terephthalate-co-isophthalate) (PET). To ascertain the microstructure characteristics in the nanocomposites, wide angle X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry techniques were used. The nanocomposites contg. both bentonite organophilized with 11-undecyl-ammonium ion and PET, and maleated PP as compatibilizer system, were found to have the highest storage modulus and the smallest loss factor values, which was mainly due to the better clay platelets dispersion. The dynamic mech. response of nanocomposites prepd. with bentonite organophillized with di-Me dehydrogenated tallow ammonium ion and maleated SEBS was strongly affected by the presence of this compatibilizer. The temp. of PP and .alpha., .beta., and .gamma. relaxations strongly depended on the interactions between the different phases in the nanocomposites. Indexing -- Section 37-6 (Plastics Manufacture and Processing)

Abstract: A new flame retardant (FR) system for ethylene-vinyl acetate, mainly based on the combination of hydromagnesite (HM, obtained from an industrial byproduct) and organo-modified montmorillonite (oMMT) has been compared with a magnesium hydroxide (MDH) and oMMT flame retardant system. The presence of oMMT in assocn. with both hydrated minerals gave a strong decrease of heat release rate in cone calorimeter tests. Moreover, the HM/oMMT combination leads to a better improvement of resistance to ignition and self-extinguishability in comparison with the MDH/oMMT one. The study of residues formed during thermal decompn. revealed the formation of forsterite (Mg2SiO4) when either MDH or HM was used in combination with oMMT. SEM observations of residues showed sintering of the mineral particles at high temp. particularly in the case of HM/oMMT compn. Indexing -- Section 37-6 (Plastics Manufacture and Processing)

Abstract: Synthetic hydromagnesite obtained from an industrial byproduct was evaluated as a non-halogenated flame retardant. It was used in combination with aluminum hydroxide (ATH) and compared with com. flame retardants like magnesium hydroxide (MH) and natural hydromagnesite-huntite (U) in a polyolefin system of low-d. polyethylene/poly(ethylene-co-vinyl acetate) (LDPE/EVA). The thermal stability and flame behavior of the halogen free flame retarded composites were studied by thermogravimetric and DTA (TG-DTA), limiting oxygen index (LOI), epiradiateur and cone calorimeter. It has been shown that synthetic hydromagnesite could be an alternative soln. to the use of MH in non-halogenated flame retardant systems in EVA. Indexing -- Section 37-6 (Plastics Manufacture and Processing)

Abstract: Abstract Reused tyres powder was used as reinforcement in HDPE-reused tyre composites. In order to improve the compatibility between both components, several pre-treatments performed over the rubber tyres were applied: sulfuric acid etching, use of a silane coupling agent and chlorination with trichloroisocyanuric acid (TCI). Mech. properties of the resulting materials (e.g. tensile strength, Young's Modulus, toughness and elongation at break) were studied and compared. Chem. modifications on the surface of reused tyres were monitored by FTIR and phys. modifications and behavior to fracture were followed by means of SEM. The influence of rubber pre-treatment was assessed by comparing the results of treated and untreated composites with those for neat HDPE. Reused tyre rubber, added to the HDPE in small quantities, acts as a filler, improving the stiffness and providing a more brittle behavior. Pre-treatment with TCI gave poor results in terms of mech. properties obtaining lower values than neat HDPE in some cases and always worst properties than sulfuric or silane coupling agent. Treatments with H2SO4 and silane coupling agent improve the ability of rubber to interact with the HDPE, increasing the material's stiffness and its tensile strength. Sulfuric acid modificates chem. and phys. the particles' surface improving mainly mech. adhesion, whereas silane acts as a compatibilizer developing chem. matrix-reinforcement interactions. Indexing -- Section 39-13 (Synthetic Elastomers and Natural Rubber)

Abstract: polypropylene blends were filled with 50 wt. % glass beads. The orientation of the PP cryst. phase, the crystn. behavior and the dynamic mech. response of these materials were analyzed. The dynamic mech. response is strongly affected by the presence of the glass beads, being possible to detect the effect of PET and MAPP on the storage modulus and loss factor values. Moreover, the alpha-relaxation of the composites is visibly affected by thermal treatments. Indexing -- Section 37-6 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: The availability of scrap poly(ethylene terephthalate) (PET) from post-consumer bottles is increasing as the post-consumer collecting systems are becoming more usual in daily life. PET is well known as a high-performance engineering thermoplastic because of its good thermal stability, chem. resistance, and excellent mech. properties. Many efforts have been carried out to use this material in housings of electronic applications. However, the flammability of PET is a shortcoming in some of these applications. In this study, our attempt is to incorporate a non-halogenated flame retardant, in form of a phosphorus-contg. compd., together with a com. glass fiber grade to achieve UL94 test V-0 rating for PET. An investigation of thermal stability and flammability (HDT, UL94 V-test) and mech. (tensile, flexural and impact tests) properties of glass fiber filled PET samples is reported as a function of fraction of flame retardant. This work shows the influence of the filler content and the interfacial filler/matrix adhesion on the flame retardant and the mech. properties. Indexing -- Section 37-6 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: A natural bentonite rich in calcium montmorillonite (CaMMT) was initially purified and ion-exchanged to obtain sodium montmorillonite (NaMMT). Both clays were organophillized by cationic exchange reaction with undecylammonium chloride, and characterized. Isotactic polypropylene (PP) was melt-compounded with both the unmodified and the organophilic montmorillonites. The hybrids produced have been characterized structurally, thermally and mech. Maleic anhydride-grafted PP (MAH-g-PP) was used as compatibilizer in some of the formulations. Homologous series of hybrids were also synthesized employing blends of PP/PET and compared with those of the pure PP to investigate possible beneficial effects due to the presence of small amts. of PET on the microstructure and properties of this kind of materials. The anal. of the results indicates some extension of both macromols. intercalation and clay particles exfoliation in the hybrids prepd. with the organophilic montmorillonite. The hybrids prepd. with compatibilized PET/PP blends were found to have a better nanostructure. Indexing -- Section 37-6 (Plastics Manufacture and Processing)

Abstract: Investigations of thermal and mech. properties of recycled poly(ethylene terephthalate) (PET) reinforced with glass fiber have been carried out, focusing on the influence of two variables involved in the extrusion process: screw speed and torque. A Factorial Exptl. Design of the processing conditions during extrusion (screw speed and torque) was done to get the best thermomech. properties vs. processing conditions. Mech. properties such as Young's modulus and impact resistance increased after the addn. of glass fiber in recycled PET matrix. Indexing -- Section 37-5 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: The study of polymer and composite behavior under high strain rates is of fundamental relevance to det. the material suitability for a selected application. However, the impact phenomenon is a very complicated event, mainly due to the short duration, large deformation, and high stresses developed in the sample. Impact tests were performed on a carbon fiber-reinforced epoxy using low-energy in the striker. A nonconservative and nonlineal spring-dashpot series model was proposed to reproduce the material behavior. The model considers simultaneously both flexural and indentation phenomena accounting for energy losses by means of the restitution coeff. Using this model, an excellent fit between the predicted and the exptl. force-time trace was obtained below the composite failure point, which was recognized by a sepn. of both mentioned curves. As the epoxy-fiber laminate has a very low viscoelasticity, the high strain rate Young's modulus obtained from the model was compared with that extd. from a conventional three point bending test, finding a very good match between the values. The study of the dashpot coeffs. indicated that the dominant mechanism is the composite flexion, while the indentation effects contribution takes on importance at low impact velocities. Indexing -- Section 38-3 (Plastics Fabrication and Uses)

Abstract: 1 mm sheets of polypropylene and ethylene-propylene block copolymers (EPBC) have been obtained using different processing methods in order to study the influence of processing induced morphol. in the fracture properties of these materials. The processing methods employed were compression molding (CM), extrusion-calendering (EC) and injection molding (IM). Addnl., the sheets obtained by extrusion and injection were submitted to an annealing process with the aim to obtain more homogeneous morphologies that would ease their characterization. The morphol. has been characterized by different techniques: polarizing light microscopy (MLP), differential scanning calorimetry (DSC), wide-angle x-ray diffraction scattering (WAXS), and SEM. The fracture properties were detd. by the essential work of fracture (EWF) method for deeply double edge notched specimens (DDENT), since these materials show ductile and post-yielding fracture behavior. The EWF technique was applied in both the melt flow (MD) and the transversal (TD) directions in the sheets obtained by extrusion and injection molding. Results show that the sensitivity of the technique allows examg. the effect of morphol. variations of thin sheets, as well as a better characterization of the orientation level (vs. other parameters like yielding stress or elastic modulus obtained by tensile test). Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: A synthetic hydromagnesite obtained from an industrial byproduct rich in magnesium oxide was employed and evaluated as a non-halogenated flame retardant for poly(ethylene-co-vinyl acetate). The filler was characterized with different techniques (such as sp. surface area, TGA, particle morphol. and size measurements, WAXS). Significant differences were found between the synthetic hydromagnesite and the natural one. Synthetic hydromagnesite was coated with stearic acid and the effectiveness of the coating process was studied by the dye adsorption method and sedimentation vol. measurements. The amt. of coating agent ranged from 1 to 4.5%. This factor was found to have a significant effect on the thermal decompn. behavior of the filler. A poly(ethylene-co-vinyl acetate) (27% of VA) was filled with the coated synthetic grades of hydromagnesite as well as with two com. flame retardants and different physicochem. properties were evaluated, including their flame retardant effect. Indexing -- Section 37-6 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: The mech. properties of polymers and composites were studied using low energy impact techniques in flexure plate configuration with semi-spherical indenter projectiles. A nonlinear and non-conservative model was used that includes permanent deformations due to impact flexure and indentation. Two systems arrayed in serial configuration, a flexion spring-dashpot and an indentation hertzian spring-dashpot, conform to this model. A 4th order Runge-Kutta math. model was used to solve the system and the data were compared with exptl. measurements of the global energy lost and the recovery coeff. Different polystyrene (PS, Lacqrene 1541 and Lacqrene 7240) composites with elastomeric and rigid dispersed phases, i.e., Sovitec glass microspheres, were tested. The model data are in agreement with expts.; the model allows for calcn. of the elastic modulus at high impact velocities and for detn. of the energy at the start of damage. Indexing -- Section 37-5 (Plastics Manufacture and Processing) Section cross-reference(s): 38, 57

Abstract: Blends of isotactic polypropylene (PP) and poly(ethylene terephthalate-co-isophthalate) (co-PET) (95/5) with and without compatibilizing agent (maleated PP, MAPP), as well as composites of these blends with glass microbeads (50 wt.%) with and without silane coupling agent surface-treatment, were prepd. and studied in regard to micro-structure and thermomech. properties. IR and Raman spectroscopy, as well as transmission electron microscopy, displayed evidence of MAPP compatibilizing action for the blend. Differential scanning calorimetry showed a remarkable effect of nucleation rate increase exerted by co-PET on the PP crystn. Moreover, glass beads were found to increase the PP nucleation rate slightly. PP crystallinity hardly varied with the compn. Wide angle X-ray diffraction allowed detn. of differences in the orientation of the PP b-axis, with more homogeneous orientations in the presence of both co-PET and glass beads. MAPP promoted the PP b-axis orientation. Differences in PP .alpha.'-relaxation could be analyzed through dynamic-mech. thermal anal. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: Fracture and thermal behavior of injection-molded poly(ethylene terephthalate-co-isophthalate) filled with milled glass fiber was studied as a function of fiber content in the range 0-40% by wt. Composite Young's modulus and tensile strength increased with fiber percentage, and good agreement was found with theor. predictions. Low rate fracture tests were carried out on injection-molded SENB specimens. Fracture toughness (KIC) and fracture energy (GIC) could be obtained by applying Linear Elastic Fracture Mechanics (LEFM). Results seemed to indicate improved fracture toughness if compared with homopolymer poly(ethylene terephthalate) composites. The reason was attributed to a lower crystallinity developed in the matrix, which promoted higher plastic strain. Indexing -- Section 37-5 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: Isotactic polypropylene (PP)/PET blends (95/5) filled with 50% by wt. of glass beads were prepd. and studied at morphol. and mech. level, and compared with its analogous samples of glass bead-filled PP. The influence of a compatibilizing agent (maleic anhydride-grafted polypropylene) and different silane coupling agents was analyzed. It has been found that PET embeds glass bead surface independently on the silane coupling agent employed. Addn. of the compatibilizer in PP/PET blends leaded to tensile strength values similar to those of unfilled PP, but rupture takes place in a brittle manner. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: In this paper an investigation of thermal, mech. (tensile, flexural, and impact), and rheol. properties of a sample of recycled and filled nylon 6 is reported as a function of the no. of reprocessing operations (3 times) and of the fraction of recycled material (15, 30, and 50%) added to the virgin material. The recycled polyamide used in this study comes from fiber grade prodn. waste. The material was filled with 20% glass beads and 10% glass fiber, according to the specifications of the application, mainly to obtain a lower-shrinkage end product, and injection molded into test samples. This work also shows that the mineral fraction, not being degraded during the injection process, allows better recyclability to the filled material. The properties of the recycled material remain below the virgin, and the best combination of both appears to be a mixt. with 30% recycled fraction, which shows a loss of properties similar to 3 reprocessing operations. Indexing -- Section 38-3 (Plastics Fabrication and Uses) Section cross-reference(s): 37

Abstract: The morphol. and fracture behavior of polystyrene/glass bead composites was investigated. Fracture parameters were calcd. at high and low strain rate as a function of bead content. The max. reinforcement occurred at 6-15 wt% glass bead content. The composite fracture behavior at low strain rate was always brittle, although the beads tend to stabilize propagation. At high strain rate, the particle reinforcement effect is lower. Indexing -- Section 37-6 (Plastics Manufacture and Processing)

Abstract: The process parameters during injection molding of polypropylene Hostalen PPN 1060, affect the crystallinity and morphol. of crystal phases; as crystallinity increases, the rigidity, tensile strength, and flexural strength increase but the tenacity and impact strength decrease. The level of crystallinity is detd. by how effectively the pressure is applied and maintained across the process and is in turn dependent on the temp. at the point of injection.

Abstract: Thermal and dynamic mech. characteristics of injection-molded disks of polypropylene (PP) filled with 40% of Mg(OH)2 and Al(OH)3 were studied by means of differential scanning calorimetry and dynamic mech. thermal anal., and were related to the anisotropy and microstructure heterogeneity of the disks. The effect of filler type, particle morphol., and surface coating was analyzed. The nucleation activity of filler particles on PP was quantified and found to be reduced in coated grades of magnesium hydroxide. The employed coatings worked isolating and preserving particles surface from direct interaction with polymer chains. The different orientations of both filler particles and PP .alpha. crystals were found to be the main cause of the differences obsd. in mech. properties. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: The influence of aluminum hydroxide particle morphol. and magnesium hydroxide surface coating on the anisotropy and microstructure heterogeneity of injection-molded disks of polypropylene (PP) filled with 40% of these fillers was studied through wide-angle x-ray diffraction measures. In general, the disks displayed an anisotropic structure due to different orientations of both filler particles and PP crystals through the part thickness. The samples also exhibited some degree of heterogeneity due to different levels of particle orientations in specimens far away and close to the disk mold entrance. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: The normalization method is applied to different magnesium hydroxide-filled polypropylenes. As the load sepn. principle is the basis of the method, its validity is checked using the load sepn. criterion developed by Sharobeam and Landes. Load separability is checked for all the materials when the condition of stationary crack length is fulfilled. During the detn. of the deformation function using the normalization method, the large decrease of the load value of highly filled materials makes it impossible to describe the load normalization variation with plastic displacement by a power law equation. Nevertheless, for the lower-filled materials, i.e. up to 40 wt.% with copolymer PP and 20 wt.% with homopolymer PP, the J-R curve can be detd. and high concordance is found with the J-R curve obtained by multiple specimen method. The applicability of the normalization method is discussed in terms of the geometry of the plastic deformation zone. It is found that the materials that are not suitable for normalization method application are characterized by a very small plastic zone, due to the restriction of plastic flow caused by mineral filler. Indexing -- Section 37-5 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: Investigation of thermal and mech. characteristics of short glass fiber-reinforced poly(ethylene terephthalate) (PET) was carried out, focusing on the influence of three of the variables involved in the injection-molding process: mold temp., holding pressure time, and closed mold time. Mold temp. plays a decisive role in controlling crystallinity development of PET matrix, which is directly correlated with the values of tensile strength and elongation at rupture. Holding pressure time acts improving piece compaction. Longer closed mold times lead to the highest values of developed crystallinity. Sodium benzoate, titanium dioxide and an ionomer were evaluated as nucleating agents for the composite. Indexing -- Section 38-2 (Plastics Fabrication and Uses) Section cross-reference(s): 37

Abstract: The influence of processing-induced morphol., thickness, and ethylene content (EC) of different ethylene-propylene block copolymers on fracture properties has been studied using the essential work of fracture (EWF) method. To analyze the influence of EC, samples with 5.5, 7.8, and 8.4 wt.% EC were used. Each material was injected in three different thicknesses (1, 2, and 3 mm). The plaques were tested using the EWF method in both main orientations, the melt flow direction and transverse to this direction. Different fracture behaviors have been obsd., some of them preventing the applicability of the EWF method. Polarized light microscopy observations have revealed the existence of a skin/core structure, which is reduced with an increase in thickness and EC. Indexing -- Section 37-5 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: The anisotropy and microstructure heterogeneity of injection-molded polypropylene (PP) disks filled with uncoated platy magnesium hydroxide (concn. 0-60 wt.%) were studied. Differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and SEM were used to identify the microscopic structure and justify properties measured by dynamic mech. thermal anal. (DMTA). The anisotropy was analyzed by measuring samples in the parallel and perpendicular directions to the disk surface. The heterogeneity was characterized by testing samples cut from different zones of the disks. It was found that the nucleation activity of magnesium hydroxide on the .alpha.-phase of PP increased with the filler concn. up to the max. level. The polymer cryst. .beta.-phase was only detected in unfilled PP and in samples contg. less than 20 wt.% of magnesium hydroxide. Remarkable differences in the polymer (.alpha.-phase) and particle orientation degrees were obsd. in the composites depending on the filler concn., the disk zone, and on whether the anal. was carried out over the disk skin or core. The anisotropy degree of PP crystals in the composites was independent of that of the filler particles up to 10 wt.% of Mg(OH)2 concn. However, from 20 wt.% of filler, the orientation of magnesium hydroxide particles clearly influenced the orientation and anisotropy of the polymer. The differences of orientation in the specimen skin were mainly responsible for the heterogeneity of the disks. Composites with lower magnesium hydroxide concn. exhibited the higher heterogeneity. These factors caused the different dynamic mech. properties obtained for the materials when the expts. were performed in different zones and/or through different directions in the injection-molded disks. Indexing -- Section 37-5 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: The activity of inorg. substrates in the catalyzed nucleation of polymer melts was studied using a nonisothermal differential scanning calorimetry technique (DSC). The anal. of the results was made by using the method developed by Dobreva-Veleva et al. In this method the kinetics of nonisothermal overall crystn. of polymers was analyzed in terms of the general non steady state nucleation theory at small undercoolings. Two examples of the applicability of this method are presented. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: Two grades of isotactic polypropylene (homopolymer and block copolymer) were filled with magnesium and aluminum hydroxides, and the mech. and fracture characteristics of the composites were studied. As expected, dispersion of such fillers in PP improved stiffness and reduced tensile yield strength. The composites fracture resistance was characterized at low strain rate applying the J-integral concept; the resistance to crack growth initiation (JIC) was decreasing as the Mg(OH)2 concn. was raised in the copolymer PP matrix. The linear-elastic fracture mechanics (LEFM) parameters were detd. by means of instrumented impact tests at 1 m/s on the homopolymer PP filled with uncoated Al(OH)3 particles. The higher the Al(OH)3 mean particle size, the lower the composite fracture energy (GIC). With com. surface-coated filler grades it was not possible to achieve LEFM conditions to characterize the fracture toughness of filled PP at 1 m/s, because the Mg(OH)2 surface coating, which is applied in practice to improve the melt processing, acts increasing the composite plasticity and reducing the tensile yield strength. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: In this paper the applicability of the load normalization method to det. crack growth resistance (J-R) curves of polypropylene copolymers (PP) is analyzed. This method allows the detn. of resistance curves ideally from a single fracture test, and it is based on the load sepn. principle, which assumes that load can be sepd. in two multiplicative functions, the geometry function, G(a/W), and the deformation function, H(.nu.pl/W), which depend of the crack depth and the plastic displacement, resp. The load sepn. validity has been checked for two different PP copolymers (block and random copolymers) and the load normalization method has been applied in order to det. and analyze the resistance curves, which have been compared, as a ref., with those obtained by the multiple specimen method. The applicability of the load normalization method to PP copolymers is analyzed by introducing some variations in the general procedure: Firstly, the deformation function is detd. using either a power law fit or the so-called LMN function. With the power law, two different fitting methods have been tested: the usual "6+1" method and a "6+6" method proposed here for giving more wt. to the final point of the curve. Secondly, the influence of the material crack tip blunting has been analyzed quantifying it through different values of the constriction factor (m) in the general expression of the blunting line. Finally, the effect of the separable blunting region extension on the J-R curve has been also analyzed by establishing different separable blunting zones. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: The essential work of fracture theory has been applied to study the fracture behavior of untreated and two silane-treated glass microbead-filled EPDM composites. The exptl. values of both Young's modulus and tensile strength have been compared with those predicted by the main theor. and semiempirical models, and the influence of the composite processing temp. on the tensile properties has been studied, showing a marked drop of stiffness and strength at a processing temp. of 200C. Good adhesion between the EPDM matrix and the beads was achieved with the silane Z-6032, resulting in higher tensile strength, and it has been obsd. that the presence of glass beads induces plasticity in the EPDM matrix. No differences of the specific essential work of fracture were found in the three filled samples, although results show that the the greater the adhesion degree between matrix and particles, the higher the value of the specific plastic work of fracture, and the higher the final instability in crack propagation are. Indexing -- Section 39-12 (Synthetic Elastomers and Natural Rubber)

Abstract: The aim of this work is to study the influence of the glass bead filler fraction and that of the filler/matrix interfacial adhesion on the mech. properties and on the fracture behavior of a poly(Me methacrylate). The variation of the tensile and flexural mech. properties with the filler vol. fraction was detd. The changes in the fracture behavior produced by the fillers were studied by evaluating the crit. stress intensity fracture and crit. energy release rate parameters of linear elastic fracture mechanics by carrying out tests with single edge notched bend geometry samples at room temp. and low strain rates. After fracture surface examn. by SEM, it was found that silane surface treatment had been rather effective and that the fracture toughening mechanism was multiple crazing. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: The essential work of fracture concept (EWF) was applied to EPDM (Dutral TER4038) compds. with untreated and silane-treated glass beads. The silane coupling agents used are silane Z-6032, Dow Corning [(N-(2-vinylbenzylamine)-ethyl)-3-aminopropyl-trimethoxysilane], and a mixt. of vinyl silanes Ucarsil PC-1A and PC-1B, Union Carbide. The theory is not applicable to pure EPDM due to its high elasticity, but it is adequate when compounded with glass beads that confer certain plasticity. Improved adhesion between EPDM and glass beads, higher plastic work of fracture, and higher final instability of crack propagation were obsd. A marked drop in stiffness was obsd. when processing the compds. at 200. The improved adhesion between EPDM and glass beads achieved through surface treatment was confirmed by SEM. Indexing -- Section 39-14 (Synthetic Elastomers and Natural Rubber)

Abstract: Low-energy instrumented falling dart impact techniques have been applied to characterize the rigidity of several series of polyolefinic flexible foams, at relatively high strain rates. Rebound tests were specially designed in order to det. the elastic modulus of the foams by application of a theor. model that describes the indentation phenomena of a hemispherical element on a sample. A potential relationship between values of the detd. elastic modulus and foam d. was found and, as expected, the foams based in HDPE showed the higher values of the elastic modulus of all the studied foams, whereas the samples contg. EVA resulted in the lower values. Moreover, the elastic modulus detd. using hemispherical dart headstocks (indenters) with different diam. resulted in a const. value, as the indentation model applied establishes. The results presented in this paper show the utility of this test to characterize mech. flexible foams, because it is sensible to identify small differences of rigidity due to variable d., foaming process and chem. compn. Indexing -- Section 38-3 (Plastics Fabrication and Uses) Section cross-reference(s): 37

Abstract: This paper presents the fracture behavior of films of biaxially oriented poly(ethylene terephthalate) studied by the essential work of fracture method. The influence of specimen thickness and mol. orientation was investigated. The results show that this method is a useful alternative for studying the plane-stress fracture of this material, finding that the specific essential work of fracture is strongly affected by the orientation [we was smaller in the direction of extrusion (MD) than in the perpendicular one (TD)], but independent of the specimen thickness in a range from 50 to 250 .mu.m. On the other hand, the plastic work item is sensitive to variations of thickness but does not depend on orientation. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: The anisotropy and heterogeneity of injection-molded disks of polypropylene, talc-filled polypropylene, and silane-treated talc-filled polypropylene were studied using dynamic mech. anal. and thermo-mech. anal. The aim was to discover the relationship between the structure of the composite, the anisotropic properties and the heterogeneity of the molded disks. The results show that, although the disks are almost homogeneous, they present a high degree of anisotropy. Indexing -- Section 38-3 (Plastics Fabrication and Uses)

Abstract: Three different exptl. techniques [compression expts. at low strain rates, instrumented falling-wt. impact tests, and dynamic mech. anal. (DMA)] have been used for the mech. characterization of a collection of crosslinked closed-cell polyolefin foams of different chem. compns., densities, and type of cellular structure. The exptl. results that it is possible to obtain from each technique are shown, and related to the different applications of these materials. The relationships between the structure and the mech. properties are also presented. Indexing -- Section 38-3 (Plastics Fabrication and Uses) Section cross-reference(s): 37

Abstract: The applicability of instrumented falling wt. impact techniques in characterizing mech. thermoplastic foams at relatively high strain rates is presented in this paper. In order to try simulating impact loading of foams against sharp elements, an instrumented dart having a hemispherical headstock was employed in the tests. Failure strength and toughness values were obtained from high-energy impact expts., and the elastic modulus could be measured from both flexed plate and indentation low-energy impact tests. The results indicate a dependence of the failure strength, toughness, and the elastic modulus on the foam d., the foaming process, and the chem. compn. This influence was found to be similar to that of pure nonfoamed materials and also to that obsd. from low-rate compression tests. The results also indicate that the indentation low-energy impact tests were more accurate in obtaining right values of the elastic modulus than the flexed plate low-energy impact tests usually used to characterize rigid plastics. The foam indentation obsd. with this test configuration contributes to obtaining erroneous values of the elastic modulus if only a simple flexural anal. of plates is applied. Indexing -- Section 37-5 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: Dynamic mech. anal. (DMA) is used to study the dynamic mech. properties of injection-molded disks of polypropylene, talc-filled polypropylene composites and silane-treated talc-filled polypropylene composites. Silane addn. in a very low proportion improves the adhesion between the filler and the polymer and enables composites to be used where otherwise they could not. Therefore, on the one hand, the composites have different properties due to the filler and the coupling agent, and on the other hand the injection processing induces a structure, resulting in inhomogeneity and anisotropy for the molded disks. SEM, differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) techniques are used to help state the microscopic structure and justify the macroscopic properties measured with DMA. Indexing -- Section 37-5 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: A fracture mechanics anal. of polypropylene and magnesium hydroxide-filled polypropylene composites was carried out. The fracture mechanics anal., based on the J-integral concept and three-point flexion specimens (SENB) at room temp., and tensile tests were used. A decrease in fracture toughness occurs as the filler vol. fraction in the composite increases. Tensile tests show that magnesium hydroxide particles promote an increase of stiffness and a decrease of the yield stress. The results are analyzed in terms of plastic deformation mechanisms in the polymer matrix.

Abstract: The mech. properties and fracture behavior of composite materials of PMMA and glass beads were studied. Three-point flexion specimens (SENB) and double torsion methods were used, to det. fracture parameters. Mech. tensile and flexion tests were performed, and the effect of vol. fraction and surface treatment of the microspheres with a silane coupling agent was studied. The surface treatment used did not induce any changes in adhesion between components. In this material of non-adhered components an increase in glass bead content led to an increase in elastic modulus, while the flexural strength and tensile strength decrease. A stable crack propagation process was obsd. in fracture tests and the fracture resistance of PMMA improved by addn. of glass microspheres, independent of particle vol.

Abstract: The efficiency of several halogen-free flame retardants in polypropylene composites was detd., using vertical (UL 94) and horizontal (UL 94 HB) flammability tests. Poly(ethylene-b-propylene) composites were produced by twin screw extrusion and the mech. properties were evaluated as a function of agent content. The flame retardants evaluated were Al(OH)3, Mg(OH)2, Zn borate, and an intumescent additive. High concn. of flame retardant (over 50%) is required to obtain satisfactory flame retardation (V-O class). However, such high concns. of flame retardant affect the mech. properties of the material, decreasing the yield and bending strength of the composites. Indexing -- Section 37-2 (Plastics Manufacture and Processing)

Abstract: The reinforcing effect of talc particles on polypropylene was analyzed by measuring tensile characteristics of the composites as a function of mineral content (0-40%). The effect of surface treatment of talc particles with silane coupling agents was also taken into account, as was the strain rate. The Young's modulus and tensile strength were measured by tensile tests on injection-molded std. specimens. The values were compared with those predicted by the principal theor. and semi-empiric models for composites. The rigidity of polypropylene/talc composites increased with mineral content, and with silane surface treatment. The tensile strength is strongly dependent on the surface treatment of talc; the tensile strength could be adequately predicted by math. models for short-fiber composites where interface shearing mechanisms are present. Indexing -- Section 37-2 (Plastics Manufacture and Processing)

Abstract: The fracture mechanism and mech. properties were studied of composites of polystyrene (Lacqrene-1541, Elf-Atochem) contg. mineral oil as lubricant, and glass microspheres having median diam. of 27 .mu.m, Poisson coeff. 0.22, Young's modulus 69 Gpa, and sp. wt. of 2.46 g/cm3. The elastic modulus of the composites increased with glass microsphere content, while the flexural strength and tensile strength decreased slightly, compared to those of neat polystyrene. The fracture strength and deformation at break of the composites improved and the composites are pliable. A micro-deformation mechanism of multiple pseudo-cracking or multiple crazing is obsd., which result in multiple planes for crack propagation, thus increasing the toughness of the material. Indexing -- Section 37-5 (Plastics Manufacture and Processing) Section cross-reference(s): 57

Abstract: The effect of filler particle size on the fracture behavior of PP/Al(OH)3 composites was investigated at a concn. level of 20 vol/vol% of filler. Two grades of Al(OH)3 having different av. particle sizes (1.5 and 60 .mu.m) were used as fillers in a polypropylene homopolymer, and the fracture characterization of the composites was based on LEFM anal. from impact data, which were obtained using an instrumented Charpy impact pendulum on injection-molded SENB specimens with a large range of initial crack lengths. It was shown that under the conditions applied the LEFM anal. seems to be valid to characterize the fracture toughness of these materials. The composite filled with the finest grade of Al(OH)3 showed higher stiffness, tensile strength, fracture toughness and fracture energy than the composite filled with coarser particles. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: Fracture behavior of injection-molded magnesium hydroxide-filled polypropylene block copolymer (PP) is presented as a function of the filler content, and it is compared to that of the unfilled PP. The J-integral concept was applied from tests carried out on SENB specimens according to the European Structural Integrity Society (ESIS) protocol for plastics. The results show lower fracture toughness (JIC) as the filler content increases in the composite, what is explained on the basis of morphol. details. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: Tensile fracture behavior of different thickness isotactic polypropylene (PP) films and sheets was studied using the essential work of fracture method following the ESIS protocol, as an alternative to LEFM and EPFM, which are not suitable for the characterization of ductile films. The specific essential work of fracture, we, and the plastic work of fracture, .beta.wp, were detd. The we value was considered as a toughness measurement, independent of the sample geometry. The influence of the thickness, t, and the rate of testing, v, on we and .beta.wp, was studied on PP films and sheets with a deep double edge notched tension geometry. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: In this work we have detd. the bending fracture parameters of polycarbonate (PC)/ABS resin blends in the PC-rich range, at low strain rate. The EPFM J-integral criterion standardized by ASTM and ESIS was applied following the Narisawa and Takemori methodol., and compared with an essential work of fracture (EWF) anal. with SENB geometry. An excellent correlation was obtained between the crit. J-value and the EWF crit. one. It was obsd. that the energy required to initiate crack growth increased up to 15 wt.% ABS in the blend, while the crack propagation resistance (dJ/da) rose until a level of 20% ABS was reached. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: Two different series of talc-polypropylene composites ranged between 0 and 40 wt % were prepd. by extrusion. In one of the series, the talc surface was modified with silane coupling agents in order to improve the affinity relation between the filler and the PP matrix. By means of X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) techniques, the configuration of the PP cryst. phase and the nucleating activity of the mineral have been stated in both series. Indexing -- Section 37-6 (Plastics Manufacture and Processing) Section cross-reference(s): 38

Abstract: Fracture behavior of injection-molded polypropylene filled with silane-treated talc was studied as a function of filler vol. fraction (0-20%) and compared to that of polypropylene filled with untreated talc. High-rate tests (0.57 m/s) on SENB specimens were carried out using an instrumented Charpy impact pendulum, and linear elastic fracture mechanics (LEFM) was applied to calc. the fracture parameters, Kc and Gc. It was found that moderate fractions of talc which were added to the polypropylene matrix increased the fracture toughness of the composite independent of the talc surface treatment. This general improvement seems to be due to the peculiar orientation of the talc platelets in the injection-molded specimens. The fracture behavior of the composites was also studied at low strain rate (1 mm/min) by tests on J-integral type specimens with the same SENB geometry. In this case, the composites with silane-treated talc presented poor J-integral values compared to those of the samples with untreated talc. This was attributed to a redn. of the plastic zone at the crack tip, since the improved coupling between the talc platelets and matrix increased the yield strength of the composite. All the results are explained on a basis of morphol. and microstructural details. Indexing -- Section 38-3 (Plastics Fabrication and Uses)

Abstract: To improve the affinity of talc and polypropylene matrix, the talc surface was modified with silane [Ucarsil PC-1A and PC-1B] coupling agents. DSC data of injection molded specimens showed a pronounced effect of talc content and surface modification on the crystn. behavior of filled PP composites. A talc content of 2% strongly affected nonisothermal crystn., specially when talc was silane-treated, by improving nucleation activity of talc. Indexing -- Section 37-2 (Plastics Manufacture and Processing)

Abstract: The fracture behavior of injection-molded talc-polypropylene (PP) was studied as a function of talc content and talc surface treatment. Untreated and silane-treated talc comprised up to 40% of the composites. The fracture toughness was measured by impact tests and linear elastic fracture mechanics was applied to calc. the fracture parameters. Moderate amts. of talc increased the fracture toughness of the composite, independently of surface treatment. This effect is attributed to the peculiar orientation of talc platelets in the injection-molded specimens. The fracture behavior of the composites was also studied at low strain rate by J-integral tests. Under conditions of ductile fracture, the composites with silane-treated talc presented poor fracture resistance, compared to that of PP filled with untreated talc. All tests were carried out according to the European structural integrity society (ESIS) testing protocols. The role of morphol. and microstructure on the fracture mechanisms is described in detail. Indexing -- Section 37-5 (Plastics Manufacture and Processing)

Abstract: Talc-filled polypropylene (PP) composites were prepd. by extrusion in a wide compn. range (0-40 wt.%). To improve the affinity relation between talc and PP matrix, we modified the talc surface with silane coupling agents. DSC investigations on test samples, prepd. by injection molding, revealing that the talc content and its surface modification had a pronounced effect on the crystn. behavior of the filled PP composites. The exptl. results indicate that a talc concn. of 2 wt.% strongly affects the nonisothermal crystn. process of the PP, esp. when talc is silane treated. Isothermal crystn. expts. on samples with min. amts. of talc (2 wt.%) revealed an improved nucleation activity with silane-treated talc. Indexing -- Section 37-5 (Plastics Manufacture and Processing)