Polypropylene Content Research Articles

Fabrication of Fine-celled PP/Ground Tire Rubber Powder Composites Using Supercritical Carbon Dioxide

PP/Ground Rubber Tire (GRT) powder microcellular blend foams were prepared by supercritical carbon dioxide. The effects of blend composition like the content of GRT and maleic anhydride-grafted polypropylene (PP-g-MA) on crystallinity, solubility, diffusivity, morphology and mechanical properties of PP/GRT microcellular composites were studied. The results showed that the PP/GRT composite foams with a unique bimodal (large and small) cellular structure, in which the large-cells embrace a GRT powder. Depending on the composition, generally, the higher content of GRT results in the smaller cell sizes, higher cell densities and relative densities, whereas the 20 wt% GRT composite shows the lowest relative density. The mechanical properties of the microcellular PP/GRT composite foams are directly related to the blend composition and the processing conditions. The PP-g-MA/GRT (50/50) produced microcellular foams with a very fine and uniform cell structure, lower relative densities and improved mechanical properties.

PP-SEBS/실리케이트 복합체의 유변학적 특성 연구

폴리프로필렌(polypropylene, PP)-SEBS(styrene-ethylene/butylene-styrene triblock copolymer)/실리케이트 복합체를 PP의 조성을 35, 40 그리고 45wt%로 변화시키며 실험실 규모의 Brabender Mixer를 이용하여 <TEX>$200^{\circ}C$</TEX>에서 용융상태에서 제조하였다. 실리케이트 조성은 5wt%로 고정하였다. PP-SEBS/실리케이트 복합체의 열적특성을 DSC와 TGA를 이용하여 분석하였다. PP-SEBS 콤파운드의 용융온도는 SEBS 함량에 따라 <TEX>$141^{\circ}C$</TEX>까지 감소하였다. 실리케이트가 PP-SEBS에 첨가되었을 때 분해온도가 증가하는 것을 TGA 결과로부터 확인할 수 있었다. 콤파운드의 유변학적 특성을 동적유변측정기를 이용하여 측정하였다. PP-SEBS/실리케이트 복합체는 PP-SEBS 콤파운드보다 shear thinning과 탄성특성이 증가하였다. 탄성특성 증가를 확인하기 위해 Van Gurp-Palmen 분석을 이용하였다. Polypropylene (PP)-SEBS/silicate composites with PP content of 35, 40, and 45wt% were fabricated by melt compounding at <TEX>$200^{\circ}C$</TEX>, using lab scale Brabender mixer. The content of silicate was fixed at 5wt%. The thermal properties of the PP-SEBS/silicate composites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). The melting temperature of PP-SEBS compound decreased up to <TEX>$141^{\circ}C$</TEX> with SEBS content. TGA result indicates an increase in degradation temperature when the silicate was added in the PP-SEBS compound. The rheological properties of the compounds were measured by dynamic Rheometer. PP-SEBS/silicate composite indicates higher shear thinning and elastic property than PP-SEBS compound. Van Gurp-Palmen analysis was applied in order to certify an increase in elasticity.

Rheology and Thermal Properties of Polypropylene/Poly(phenylene Sulfide) Microfibrillar Composites

The polypropylene (PP)/ poly(phenylene sulfide) (PPS) in-situ microfibrillar composites were prepared by the melt blending technology using a single screw extruder. Maleic anhydride grafted polypropylene (PP-g-MAH) is used as the compatibilizer. The rheology was characterized on capillary rheometer, and thermal behaviors of the PP/PPS were investigated by DSC. The experiment results reveal that the melting PP/PPS composites conform to the law of Non-Newton and show typical shear-thinning behavior. The viscosity of PP/PPS composites is nearly independent of the PPS concentration at 270°С and 280°С , respectively. However, the contents of PPS have an influence on shear viscosity of the PP/PPS at 290С and 300°С . The DSC results exhibit that the crystallization temperatures (TC) of PP in the composites are higher than that of the pure PP, and the TC of PP increases slightly with increasing PP content in the composites. Moreover, the melting temperature of PPS in the composites decreases slightly with increasing PP content.

Quantification of polypropylene (PP) in wood plastic composites (WPCs) by analytical pyrolysis (Py) and differential scanning calorimetry (DSC)

Abstract The common use of wood together with traditional chemical polymers opens new possibilities in the field of sustainable product development. Wood plastic composites (WPCs) are an ideal combination of these raw materials, which can be produced with standard plastic technology such as extrusion or injection moulding. Wood to plastic ratio in a WPC influences quality and price, thus adaptation of analytical tools for material testing and quality assurance is required. In this study, the suitability of analytical pyrolysis (Py) and differential scanning calorimetry (DSC) was investigated to quantify the amount of polypropylene (PP) in WPCs. The reliability of these methods was tested by analysing WPCs with different ratios of wood and PP. The amount of PP can be determined with DSC based on its melting point as the influence of wood is negligible in this context. The increment of typical PP markers and decrement of wood markers was observed and quantified in the pyrograms if the PP content in WPCs was elevated. Thus, the ratio of PP and wood can be reliably quantified by means of online and offline analytical pyrolysis.

Effect of Compatibilizer on Mechanical, Morphological, and Thermal Properties of Chemimechanical Pulp-reinforced PP Composites

Mechanical, morphological, and thermal properties of injection molded, chemimechanical pulp (CMP)-reinforced polypropylene (PP) composites were investigated as a function of different concentrations of maleic anhydride-grafted PP. It was found that tensile strength and failure strain and the notched impact strength increased progressively with increasing compatibilizer content, whereas the addition of any concentration of compatibilizer did not alter the tensile modulus. Scanning electron microscopy — micrographs of tensile fracture surfaces of composites with 2% compatibilizer indicated very little fiber pullout and many fractured fibers. The thermal stability of pure PP was found to be higher than that of CMP-reinforced PP composites. With addition of compatibilizer, the thermal stability of the composites was slightly increased. The activation energy was determined to describe the energy consumption of the initiation of the thermal degradation process. The activation energy of the composites was found to depend on the dispersion and interfacial adhesion of CMP and PP matrix.

Effects of nanoclay and coupling agent on the physico‐mechanical, morphological, and thermal properties of wood flour/polypropylene composites

AbstractThis article presents the effects of coupling agent and nanoclay (NC) on some properties of wood flour/polypropylene composites. The composites with different NC and maleic anhydride grafted polypropylene (MAPP) contents were fabricated by melt compounding in a twin‐screw extruder and then by injection molding. The mass ratio of the wood flour to polymer was 40/60 (w/w). Results showed that applying MAPP on the surface of the wood flour can promote filler polymer interaction, which, in turn, would improve mechanical properties of the composite as well as its water uptake and thermal stability. Composite voids and the lumens of the fibers were filled with NC, which prevented the penetration of water by the capillary action into the deeper parts of composite. Therefore, the water absorption in composites fabricated using NC was significantly reduced. Scanning electron microscopy has shown that the treatment of composites with 5 wt% MAPP, promotes better fiber–matrix interaction, resulting in a few numbers of pull‐out traces. In all cases, the degradation temperatures shifted to higher values after using MAPP. The largest improvement on the thermal stability of composites was achieved when NC was added. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Influence of maleic anhydride grafted polypropylene on the dispersion of clay in polypropylene/clay nanocomposites

This paper investigates the specific effect of the maleic anhydride (MA) grafting content of MA-grafted polypropylene (PP-g-MA) compatibilizer on the morphology of PP/clay nanocomposites (PPCNs) without the interference of molecular weight (MW) changes of the compatibilizer. To do this, PP-g-MA with different grafting contents and approximately the same MW was prepared using MA and styrene by melt extrusion on a twin-screw extruder. The two prepared series of PP-g-MA were used, respectively, in two series of PPCN based on PP homopolymer and impact copolymer to match the melt flow rate of the compatibilizer with that of the PP matrix. The morphology observations from X-ray diffraction and transmission electron microscopy, as well as rheological measurements, showed that the grafting content of PP-g-MA in the range of 0.2–1.4wt% has no appreciable influence on the dispersion of organoclay, whereas the loading of PP-g-MA can effectively influence the intercalation and delamination of clay. The intercalation and exfoliation mechanism of prepared PP-g-MA is discussed and compared with that of PP-g-MA oligomer. Maleic anhydride grafted polypropylene (PP-g-MA) with different grafting contents and approximately the same molecular weight was prepared. The grafting content of PP-g-MA in the range of 0.2–1.4 wt% shows no appreciable influence on the dispersion of organoclay, whereas the loading of PP-g-MA can effectively influence the intercalation and delamination of clay. The intercalation and exfoliation mechanism of prepared PP-g-MA is discussed and compared with that of PP-g-MA oligomer.

Elastic properties of polypropylene/ethylene–octene copolymer blends

Blends of polypropylene (PP) and ethylene–octene copolymer (EOC) across the whole composition range (10, 20, …, 80, 90 wt.%) were investigated with focus on mechanical properties. Samples (0–50% of PP) were stretched in a tensile machine to given elongations (100, 200 and 300%) and then the crosshead returned to the initial position. The residual strain values were obtained from the hysteresis curves. These residual strain values were plotted as a function of applied strain and PP content. Stress at given elongation (M100 and M300) was also plotted as a function of PP content. At low PP content (0–20%), residual strain and stress at given elongation are close to those of pure EOC. A steeper increase in these values was observed for concentrations 20–50% of PP. Another set of experiments involved tensile testing to break (full range of concentrations). From these experiments, tensile modulus and stress at break were evaluated and plotted as a function of PP content. Modulus values were close to that of pure EOC in the range of 0–25% of PP. Then, the values start to increase almost linearly with increasing PP content. The mechanical properties of the blends were correlated with the structure observed by transmission electron microscopy (TEM). At 20% PP, there are PP particles with round shape uniformly dispersed in the EOC matrix. When the PP content increased to 30%, the shape of the PP particles changed to elongated. In the case of 40% of PP, the structure resembles a co-continuous one. Differential scanning calorimetry (DSC) revealed the nature of the excellent elastic behavior of EOC. EOC crystals at 7 wt% act as tie points for amorphous chains (physical cross-linking).

Experimental and statistical study of the effects of material properties, curing agents, and process variables on the production of thermoplastic vulcanizates

AbstractA comprehensive experimental study together with statistical analysis was performed to identify the optimal process conditions, materials selection, and curing system for the production of thermoplastic vulcanizates (TPVs) based on EPDM rubber and polypropylene. Two types of curing systems were studied together with five different types of EPDM rubber. The TPV products were assessed according to elastic modulus and degree of swelling (indicators of crosslink density), ultimate tensile strength, ultimate elongation, tear strength, and compression set. A design of experiments method was applied to minimize the number of experiments and to obtain response surface and regression models for this complex and highly interactive system. From the modeling results, optimum values for the influential factors were obtained to achieve the target end product properties. It was found that a phenolic resin‐based curing system gave the best product properties and that the most influential factors were the rubber characteristics (ethylene content, ethylidene norbornene content, and molecular weight) and the polypropylene content in the formulation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Impact of Polypropylene Application Method on Long-Term Aging of Polypropylene-Modified HMA

The effect of polypropylene application method on long-term aging of hot mix asphalt (HMA) was investigated. Three different application methods were considered within this paper, namely, the coating method (where aggregate surface was coated with polypropylene), the dry method, and the wet method. Constant polypropylene content of 0.7% by weight of total mix was adapted. Laboratory aging program was set up to simulate the aging process of asphalt pavement occurred in the field. The mechanical properties of aged and unaged mixtures prepared using the three different polypropylene application methods were evaluated based on Marshall quotient, the indirect tensile strength, fracture energy, and unconfined compressive strength. Experimental testing has revealed the enhancement in the mechanical properties of HMA when polypropylene was added. The polypropylene additive has managed to counteract the effect caused by long-term aging of HMA. A comparison between the three polypropylene application methods indicated that the coating method has caused a considerable improvement in the indirect tensile strength and fracture energy of HMA under aged and unaged conditions. Marshall quotient and compressive strength of tested mixtures have shown less dependency on the polypropylene application method.

Effects of Formulation Design on Thermal Properties of Wood/Thermoplastic Composites

In this study, thermal properties of wood/HDPE composites were measured by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The composites comprised of different wood (45%, 55%, and 65%) and maleic anhydride grafted polypropylene (MAPP) contents (0%, 1.5%, and 3%), and particle size (20, 40, and 80 mesh) were produced by extrusion method. TGA measurements showed that wood content is the most important factor affecting the thermal stability, initial mass loss, and ash content of the composites. Any increase in wood content led to increase in ash content and less thermally stable composites. MAPP and particle size were found to have less impact on thermal stability. By retarding the formation of charcoal MAPP influenced thermal stability of composites adversely in composites consisting of bigger particle. Composites made of 65% wood content with 20 mesh size and 0% MAPP were more thermally stable than composites made of 65% wood content with 80 mesh size and 3% MAPP, in the temperature range of 270-500°C. Melting point measurements by DSC showed that melting point had no relationship with wood and MAPP contents, and particle size.

Renewable elastomers based on blends of maleated polypropylene and plasticized starch

AbstractMost recent developments in polymers from renewable resources have focused on thermoplastics, whereas there has been no comparable development of plastics with elastomeric properties. Here we evaluate the possibility of developing renewable elastomers based on starch. Potato starch plasticized with glycerol (called plasticized starch, or PLS) was melt‐blended with small quantities (5 wt % or 15 wt%) of maleated polypropylene (MAPP). The maleic anhydride groups of the polypropylene are expected to react with the hydroxy groups of starch under melt blending conditions. The resulting blends of MAPP and PLS were characterized by mechanical testing, SEM, DMA, and DSC. SEM, solubility and adhesion tests indicate that the blends are two‐phase materials, in which the continuous phase PLS is physically crosslinked by polypropylene domains. The materials showed rubbery properties as judged by a low glass transition temperature (∼−50°C independent of polypropylene content), and a wide rubbery plateau in DMA experiments that extended from room temperature to as high as 170°C. The tensile properties are also characteristic of elastomers. However, slow aging due to starch crystallization, and extraction of glycerol upon water exposure remain two challenges that must be overcome before the materials can be used as practical elastomers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Hypercrosslinked polystyrene microspheres with bimodal pore size distribution and controllable macroporosity

AbstractA combination of suspension polymerization and postcrosslinking was used to prepare hypercrosslinked polystyrene (H‐PS) microspheres with controllably bimodal pore size distribution in the presence of toluene and polypropylene (PP) as a coporogen. The proportion of PP in the coporogen was changed to investigate the influence of the coporogen composition on the pore structure of the H‐PS microspheres. The addition of a small amount of PP achieved the aim of a clearly bimodal pore size distribution and the control of the macroporosity of the H‐PS microspheres, which have potential application in the preparation of catalyst supports. The specific surface area of the H‐PS microspheres could be adjusted in the range 380–790 m2/g by changes in the concentration of PP in the coporogen. Moreover, the H‐PS microspheres displayed all the characteristics of Davankov‐type resins by their ability to be swollen in both thermodynamically poor solvents such as water and good solvents such as toluene. Finally, the possible mechanism of porosity formation during polymerization and postcrosslinking was also examined by a combination of pore structure data and the appearance of the microspheres before and after postcrosslinking. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Traditional polypropylene and lightweight meshes in totally extraperitoneal inguinal herniorrhaphy

Background Placement of a prosthetic mesh is integral to successful totally extraperitoneal (TEP) herniorrhaphy. Available meshes have supported the surgical efforts well but search for an ideal mesh continues. Post-herniorrhaphy pain is an index of patient reported outcomes (PRO). The pain is attributable to balloon dissection, cautery, sutures, tackers and prosthesis. Reducing polypropylene content of the mesh is associated with attenuated inflammatory response by the host and improved compliance and comfort. We report the difference in PROs in TEP herniorrhaphy with either heavy polypropylene (PPM) or light weight mesh (LWM) being used for the repair. Patients and methods From June 2004 to December 2005, consecutive candidates for TEP herniorrhaphy were enrolled for this prospective study with an informed consent and compliance to Ethics guidelines. They were operated under general anesthesia (GA) on a day care basis using either PPM or LWM meshes as per the patient's choice. Operative and postoperative PRO were statistically analyzed by an independent doctor using the Microsoft Office Excel 2003. Results One hundred fourteen (84 PPMs and 30 LWMs) TEP herniorrhaphies were performed under GA on 57 male patients without any exclusion, on a day care basis. There was no technical difficulty, operative complications, conversion or prolonged hospital stay in either group. Patients of LWM reported better outcome in regards to pain, NSAID usage, seroma and recurrence. All patients of LWM reported an earlier return to activity. Conclusion Light weight meshes result in comparatively better “patient reported outcomes” in TEP inguinal herniorrhaphy as compared to heavy polypropylene meshes.

Miscibility, Mechanical and Thermal Properties of Melt-Mixed Poly(trimethylene terephthalate)/Polypropylene Blends

This study examined the miscibility, mechanical and thermal properties of melt-mixed blends of PTT(poly(trimethylene terephthalate)) with PP(isotatic polypropylene). DMA and SEM results indicated that the PTT/PP blends are immiscible. Revealed from TGA analyses, the blends with a higher PP content showed a higher degradation temperature. A complex melting behavior was observed for the blends. The isothermal crystallization kinetics of the blends was analyzed from 200°C to 210°C using the Avrami equation. The WAXD results showed that the crystal structure of PTT remained unchanged in the blends. Nevertheless, the PP rich blends possessed lower tensile strength and higher elongation at break.

Fabrication optimization of polypropylene composites reinforced with steam-exploded wood flour by wet process

To take advantage of the unique characteristics of the wood flour by combining them with plastic in conventional panel pressing methods, a wet process was developed to make composites using polypropylene and steam-exploded (SE) flour from small-diameter loblolly pine. Wet-laid wood flour/polymer composites were fabricated using a standard TAPPI handsheet method followed by compression molding. The variables that may affect the product properties were investigated using an orthogonal test design. The results revealed that the modulus of elasticity (MOE) of composites increased, while modulus of rupture (MOR) decreased with increasing SE wood flour content. Both MOE and MOR of the composites increased with maleic anhydride grafted polypropylene content. Dynamic mechanical analyzer and differential scanning calorimetry measurement gave insight into the structure of these composites, and scanning electron microscope was used to characterize the interfacial adhesion.

Effect of Nanoclay on the Mechanical and Morphological Properties of Wood Polymer Nanocomposite

Polypropylene/wood flour composites with different nanoclay and maleic anhydride grafted polypropylene (PP-g-MA) contents were fabricated by melt compounding and then by injection molding. The mechanical properties, such as flexural modulus, tensile modulus, elongation at break, and impact strength, were evaluated. Results indicated that the flexural modulus, tensile modulus, and elongation at break increases with increase of nanoclay up to 3 phc at the same concentration of PP-g-MA, and then decreases. However, the impact strength of the composites decreases with increased nanoclay loading. Also, the effect of compatibilzer was positive in terms of enhancing the mechanical properties of the composites. The morphology of the nanocomposites has been examined by using X-ray diffraction and transmission electron microscopy. Morphological findings revealed that intercalation form, the sample with 3 phc concentration of clay, which implies the formation of the intercalation morphology and better dispersion than 6 phc, and the d-spacing of clay layers in the composite were improved in the presence of compatibilizer.

Polypropylene/natural rubber thermoplastic elastomer: Effect of phenolic resin as a vulcanizing agent on mechanical properties and morphology

AbstractThe aim of this study is to characterize thermoplastic elastomers (TPEs) from polypropylene and natural rubber with and without phenolic resin as a vulcanizing agent. The blends containing 40–60 wt % of polypropylene were mixed in an internal mixer and pressed with a compression molding machine. TPEs without rubber vulcanization, named as unvulcanized thermoplastic natural rubber (uTPNR) were compared to TPEs containing dynamic vulcanized rubber, referred as vulcanized thermoplastic natural rubber (vTPNR). The uTPNRs illustrated cocontinuous phase morphology, whereas the vTPNRs displayed dispersed phase of vulcanized natural rubber. Tensile properties, tear strength, thermal ageing resistance, ozone resistance, tension set, hardness and swelling test in toluene, IRM 903 oil and engine oil were carried out according to ASTM. It was found that tensile and tear strength, hardness and tension set of the uTPNRs increased with increasing polypropylene content. Dynamic vulcanization improved tensile strength, elongation at break, tension set and degree of swelling of the TPEs, whereas hardness and tear strength did not show significant change after dynamic vulcanization. The vTPNRs exhibited higher ozone resistance and swelling resistance than the uTPNRs. Reprocessability of the vTPNRs was investigated and showed that tensile strength decreased at 20 and 30% and elongation at break decreased at 13 and 27% for the first and the third reprocessing respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Dissolution mechanism of polymers in high pressure–high temperature n‐alkanes—Application to blends separation

AbstractThe use of a high temperature–high pressure near critical solvent is an interesting alternative to dissolve high‐molecular‐weight polyolefins with alkanes. This characteristic allows their separation from the blends with other polymers. In the present work, the polymer dissolution of commercial polypropylene (PP) and polystyrene (PS) in n‐alkanes at high pressure and high temperature is analyzed. The comprehension of the different polymer dissolution behaviors and solvent affinities clarifies the understanding of the mechanism of PP/PS physical blend separation under these conditions. The PP dissolution in n‐pentane and n‐heptane was interpreted in terms of chain disentanglement and solvent diffusion. A mathematical model is proposed to predict the experimental results and to calculate mass transfer coefficients in order to quantify the PS barrier effects. It is possible to assess the effect of the temperature on the pure PP solubilization using these coefficients. In blends separation, it was demonstrated that the PS, insoluble at the same conditions, hinders the PP diffusion. As the PS blend content increases, the separation efficiency decreases. Particularly, mass transfer coefficient increases with PP content while PS is the matrix (PS barrier decreases). Afterwards, PP has no ulterior barriers and mass coefficient remains constant. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Novel approach to textile design for barriers against electromagnetic radiation

Human-friendly barriers against microwave radiation are designed using non-woven multiple layers of natural (flax) fibres, as well as flax and polypropylene fibre blends, with the split-ring resonators implanted so as to allocate the barrier properties in the pre-determined frequency band (X-band is selected for its applications in traffic radars and telecommunication). Oscillator model is proposed for determining the ring resonance frequency. The band of non-transmission up to ∼40 dB is observed. The band is found to shift depending on the flax and polypropylene contents in the blend, the distance between the ring centres, and on the number of textile layers.