Polypropylene Resin Research Articles

Effect of processing conditions on the microstructure of microcellular PP/WF composites prepared by the continuous extrusion molding technology

The polypropylene (PP) and wood flour (WF) were mixed first and then extruded by a single-screw extruder foaming system to prepare the microcellular wood-polymer composites (WPCs) in this article. In addition to PP and WF, polyolefin elastomer (POE), talc powders and other fillers were also added to improve the cell structures of the samples. And two types of PP resins were introduced to the formulation of the composites to study the effect of the molecular chain structure on the rheological properties of the samples. Besides, the effects of processing conditions, such as die temperature and screw speed, on the properties of the samples were also investigated. The experimental results indicate that compared with PP1, the complex viscosity of PP2 decreased faster with the shear rate because of the linear molecular chain structure. Besides, the maximum impact strength of PP2/WF composites was 138.5 % higher than that of PP1/WF composites, while the tensile and flexural strength of PP2/WF composites were much lower. In addition, the best microcellular structure and the maximum impact strength were also obtained with the die temperature of 190 °C and the screw speed of 2 rpm.

Cellulose modified by citric acid reinforced polypropylene resin as fillers

The greatest challenge hindering the use of cellulose as a reinforcing filler in polymeric composites is its poor compatibility due to the inherent hydrophilicity of cellulose and the hydrophobic nature of polymeric matrices. To solve this issue, we demonstrate an effective water-based method to render the cellulose surface with high carboxyl content through the esterification of hydroxyl groups with citric acid in a solid phase reaction without the use of noxious solvents. The modified cellulose was then further hydrophobized by grafting magnesium stearate to the surface. Consequently, the flexural properties of PP composites reinforced by the hydrophobized cellulose fillers were greatly improved compared to those of composites containing hydrophilic cellulose and pure PP resin. The surface modification conditions and filler proportions in composites were optimized. Because of the innocuity and cost-efficiency of citric acid, we believe that citric acid-modified cellulose has immense potential as a sustainable and cost-effective reinforcing filler.

Study of the surfactants role in natural fibres reinforced composites for structural applications

In this study, hemp fibres were used as reinforcements in polypropylene (PP) resin to form composite materials for structural applications. Adhesion between the fillers and holding matrix was enhanced using alkalisation, KMnO4treatments respectively on the fibre surface thus developed. Spectroscopic analysis such as Fourier transforms infrared (FTIR) and scanning electron microscope (SEM) was carried out to determine interferential adhesion and homogeneous distribution of fibres in the holding matrix. Based on the results obtained fibres treated with both NaOH and KMnO4 treatment showed better mechanical properties than the treatments done in isolation. Among the results obtained fibres specifically treated with specific co mposition of 5% NaOH an d 0.6% KMnO4 exh ibited better mechanical properties compared to those with treated and untreated fibre composite samples.

Effect of Talc Size on Surface Roughness and Glossiness of Polypropylene Injection Molding Application to Automotive Plastics

Talc‐containing polypropylene (PP) resin is extensively employed in automobiles. Herein, considering the microstructure transfer process in injection molding, the effect of the talc's dispersibility and particle size on this process and its impact on the gloss level of the product were investigated. Results show that a fine unevenness of about several micrometers was self‐formed by the shrinkage of PP in nontransferred areas due to the blending of talc. Additionally, the amount of self‐formed unevenness tended with an increase in the average particle size of talc. Furthermore, due to PP shrinkage and different densities of talc, it was observed that a fine tiger‐stripe pattern was self‐formed using special molds with modified microstructure. This self‐formed fine unevenness changes the gloss level owing to the diffused light reflection effect. This study proposes controlling this change by controlling the average particle size of talc and structure of the mold. POLYM. ENG. SCI., 60:132–139, 2020. © 2019 Society of Plastics Engineers

Preparation of a new high-efficiency resin deodorant from coal gasification fine slag and its application in the removal of volatile organic compounds in polypropylene composites

Deodorizing materials are often restricted from large-scale industrial production due to the high preparation cost. By utilizing the simple acid leaching technology, this study made use of the coal gasification fine slag (FS) as raw material to prepare a cost effective FS-based deodorant (FSD) with a specific surface area of 393 m2 g−1 and a pore volume of 0.405 cm3 g−1. The propane adsorption test on FSD showed the maximum adsorption capacity to be as high as 121.61 mg g−1 at 273 K. The partition coefficient values at 10% and 100% breakthrough (BT) for FSD to adsorb propane were 1.5 × 10−3 and 3.2 × 10−4 mol kg−1 Pa−1, respectively. Furthermore, the FSD was applied in the removal of volatile organic compounds (VOCs) pollutants from polypropylene resin (PP). It showed that the deodorizing effect of the FSD was nearly three times as good as the commonly used zeolite deodorants, which was able to decrease 50 percent of the VOCs volatilization amount in PP resin. Moreover, the FSD can better strengthen the mechanical properties of PP resin. This work provides a new method for the industrial production of deodorants as well as a new direction for the recycle of coal gasification wastes.

Neurofuzzy modelling of moisture absorption kinetics and its effect on the mechanical properties of pineapple fibre-reinforced polypropylene composite

Natural fibres possess low density, less abrasiveness, good strength and sound absorption capacity and its significance lies in being renewable and biodegradable. The mechanical characteristics and moisture absorption of pineapple fibres reinforced with polypropylene resin are focused in this study. Chopped fibres and unidirectional fibre mats of pineapple were reinforced with polypropylene resin to make pineapple fibre/polypropylene composites. The length of the pineapple fibres and the orientation of the layup of the fibre mats are varied to make composite specimens and the mechanical properties are tested. Moisture absorption studies were carried out and it was confirmed to follow Fickian diffusion. A total of 384 samples were tested and it was observed that all the samples reached its saturation in moisture absorption before 720 h and the strength was inversely proportional to the moisture absorbed. Specimens reinforced with unidirectional fibre mats of alternate orientation possessed high strength irrespective of the moisture absorbed when compared to the specimens reinforced with chopped fibres of random orientation. Neuro fuzzy modelling using ANFIS tool box in MATLAB was used to correlate the static mechanical properties of pineapple fibre-reinforced polymer under different moisture conditions, fibre orientations, fibre volume percentage, fibre size, etc.

Investigation on the interface modification of PET/PP composites

In this study, surface modifications and manufacturing processes for polyethylene terephthalate (PET)/polypropylene (PP) composites were developed. When non-polar PP resin is combined with polar polyester fiber, its compatibility and wettability are the key technologies. Maleic anhydride-grafted PP (MAPP) was blended with PP to improve the polarity of the PP resin and react with PET fibers. In addition, a primer was applied to the PET fabric to improve the bonding and reactivity of PET fiber and MAPP. PET/PP composites that imitated the texture and appearance of carbon fabric were prepared by thin film stacking method. The effect of MAPP and primer on interfacial bonding was evaluated by single-fiber pullout test. The mechanical properties of the PET/PP composites such as impact, and open-hole tensile strength (OHT), were studied.

Structure and Properties of a Metallocene Polypropylene Resin with Low Melting Temperature for Melt Spinning Fiber Application

An isotactic polypropylene (iPP-1) resin with low melting temperature (Tm) is synthesized by a metallocene catalyst and investigated for melt-spun fiber applications. The structure, thermal and mechanical properties, and feasibility of producing fibers of a commercial metallocene iPP (iPP-2) and a conventional Ziegler–Natta iPP (iPP-3) are carefully examined for comparison. Tm of iPP-1 is about 10 °C lower than the other two samples, which is well addressed both in the resin and the fiber products. Besides, the newly developed iPP-1 possesses higher isotacticity and crystallinity than the commercial ones, which assures the mechanical properties of the fiber products. Thanks to the addition of calcium stearate, its crystal grain size is smaller than those of the two other commercial iPPs. iPP-1 shows a similar rheological behavior as the commercial ones and good spinnability within a wide range of take-up speeds (1200–2750 m/min). The tensile property of fibers from iPP-1 is better than commercial ones, which can fulfill the application requirement. The formation of the mesomorphic phase in iPP-1 during melt spinning is confirmed by the orientation and crystallization investigation with wide angle X-ray diffraction (WAXD), which is responsible for its excellent processing capability and the mechanical properties of the resultant fibers. The work may provide not only a promising candidate for the high-performance PP fiber but also a deep understanding of the formation mechanism of the mesomorphic phase during fiber spinning.

Interfacial adhesion of recycled carbon fibers to polypropylene resin: Effect of superheated steam on the surface chemical state of carbon fiber

The interfacial adhesion between polypropylene resin and recycled carbon fibers (RCFs) subjected to superheated steam (SHS) treatment was examined by performing microdroplet tests on the recovered single fibers. As-received virgin carbon fibers were selected as reference material for the evaluation. The interfacial shear strength (IFSS) was calculated to quantify the interfacial adhesion between the fiber and matrix. By comparing the IFSS of RCFs to those of corresponding virgin fibers, we found that 1 h SHS treatment at 650 °C improved the interfacial adhesion. X-ray photoelectron spectroscopy was employed to characterize the element composition and the content of functional groups on fiber surface. The SHS introduced extrinsic oxygen-containing functional groups on the fiber surface during the treatment. The increase in the IFSS value after SHS treatment is considered to be due to the chemical interaction at the interface between these functional groups and the resin.

Effect of Compatibility on the Foaming Behavior of Injection Molded Polypropylene and Polycarbonate Blend Parts.

To improve the foaming behavior of a common linear polypropylene (PP) resin, polycarbonate (PC) was blended with PP, and three different grafted polymers were used as the compatibilizers. The solid and foamed samples of the PP/PC 3:1 blend with different compatibilizers were first fabricated by melt extrusion followed by injection molding (IM) with and without a blowing agent. The mechanical properties, thermal features, morphological structure, and relative rheological characterizations of these samples were studied using a tensile test, dynamic mechanical analyzer (DMA), scanning electron microscope (SEM), and torque rheometer. It can be found from the experimental results that the influence of the compatibility between the PP and PC phases on the foaming behavior of PP/PC blends is substantial. The results suggest that PC coupling with an appropriate compatibilizer is a potential method to improve the foamability of PP resin. The comprehensive effect of PC and a suitable compatibilizer on the foamability of PP can be attributed to two possible mechanisms, i.e., the partial compatibility between phases that facilitates cell nucleation and the improved gas-melt viscosity that helps to form a fine foaming structure.

Exploring the Effects of Stereo-Defect Distribution on Nonisothermal Crystallization and Melting Behavior of β-Nucleated Isotactic Polypropylene/Graphene Oxide Composites.

In this work, using two isotactic polypropylene (iPP) resins with similar average isotacticity and molecular weight but different uniformities of stereo-defect distribution, the β-nucleated iPP/graphene oxide (β-iPP/GO) composites (NPP-A and NPP-B) were prepared to investigate the effect of stereo-defect distribution on the nonisothermal crystallization kinetics and polymorphic melting behavior of the composites by means of scanning electron microscopy, wide-angle X-ray diffraction, and differential scanning calorimetry. The results showed that more uniform stereo-defect distribution led to a slight increase of the crystallization rate and decrease of the crystallization activation energy Ec. NPP-B with more uniform stereo-defect was more favorable for the formation of a large amount of β-phase. Moreover, the role of the cooling rate was also discussed and it was found that the higher the cooling rate, the higher the β-phase content and the smaller the crystalline sizes, meanwhile, the higher the amount of β-phase with relatively lower thermal stability that will take part in β–α recrystallization during the subsequent melting process. For β-iPP/GO composites, although the cooling rate greatly influences the polymorphic behavior and crystalline structures of the composites, the uniformity of stereo-defect distribution was found to be the first factor determining the formation of the β-phase.

Development of non-fluorine superhydrophobic textiles using polypropylene resins

This study aims to develop environment-friendly superhydrophobic textiles forming nanoparticles of polypropylene that have intrinsically low surface energy, and thus achieving the requirements for superhydrophobicity, such as hierarchical roughness and low surface energy at once. This work mainly studies the influences of tacticity (isotactic, atactic), concentration (10, 20, 30 and 40 mg/ml), drying temperature (30℃ and 70℃) and the mixing ratio of the solvent/non-solvent (9:1, 8:2, 7:3 and 6:4) on the coating morphology and wettability. In the case of isotactic polypropylene, the optimal condition showing the water contact angle of 173° and the water shedding angle of 4° was at 70℃ drying temperature, 30 mg/ml concentration and 6:4 solvent/non-solvent mixing ratio. Amorphous polypropylene showed the water contact angle of 163° and the water shedding angle of 9° at the condition of 30℃ drying temperature, 40 mg/ml concentration and 8:2 solvent/non-solvent mixing ratio. It was revealed that superhydrophobicity by amorphous polypropylene was exhibited at lower drying temperature and lower mixing ratio for the non-solvent. This is attributed to the different evaporation temperature or speed of the solvent/non-solvent mixing according to the tacticity of polypropylene. This study demonstrated that environmental-friendliness was improved in that superhydrophobic textiles were developed without fluorine compounds, maintaining vapor permeability. This study also developed a finishing method using amorphous polypropylene under a mild condition in terms of drying temperature and solvent toxicity, which is expected to be applicable not only to polyester but also to various fabrics.

Improvement of mechanical properties of polypropylene resin by addition of cellulose microfibers

Improvement of mechanical properties of polypropylene resin by addition of cellulose microfibers

Influence of talc and rubber contents on surface replication of polypropylene injection molding application to automotive plastics

Abstract The influence of talc and rubber contents included in polypropylene (PP) on surface replication properties for microstructure was analyzed. By increasing the talc and rubber contents, surface replication on the injection-molded parts has been reduced. From the surface observation, an uneven microstructure surface was formed for a material containing talc during the shrinkage process. It was confirmed that if the PP resin contains talc, then the correlation between glossiness of the mold and glossiness of the molded product was lost and glossiness was decreased. On the contrary, as the rubber content increased, the replication properties improved. At the same time, generation of the streak pattern in the transferred area, which was generated in the base PP, decreased and glossiness increased. Moreover, the fine uneven structure of the nontransferred area, as observed in the talc-containing material, was not observed in the rubber-containing material.

Brenntag collaborates with Umicore to distribute PU and polyester-based catalysts

A novel charring foaming agent N-methyl triazine-ethylenediamine copolymer defined as MTEC was synthesized from cyanuric chloride, methylamine and ethylenediamine through nucleophilic reaction. Its chemical structure was well characterized by Fourier transform infrared spectroscopy, elemental analysis and 13C solid-state nuclear magnetic resonance. The wettability of flame retardant was evaluated by water contact angle (CA) tests, and the synthesized MTEC present excellent hydrophobic property with the water CA of 117°. Meanwhile, the water CA of the prepared intumescent flame retardant (IFR) system containing MTEC, ammonium polyphosphate and silica reached 104° and also presented hydrophobic property. The obtained IFR was incorporated into polypropylene (PP) resin to prepare flame retardant PP composites, and the flame retardancy, thermal degradation behavior, water resistance and flammability behavior for IFR-PP were investigated by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimeter and thermogravimetric analysis (TGA) tests. Water resistant properties of IFR-PP composites were evaluated by soaking the samples into distilled water at 70 °C for 168 h. The results demonstrated that IFR-PP samples both passed UL-94 V-0 flammability rating before water treated and after hot water soaking and drying when the loading amount of IFR was 22 wt %, the LOI value of IFR-PP only decreased from 29.6 to 29.3% and the mass loss percent was only 0.17 and 0.69% for 3.2 and 1.6 mm samples after water soaking and drying. The TGA results indicated that the incorporation of IFR promoted PP matrix decomposition and charring at a relative low temperature, and then enhanced the char yield and thermal stability for IFR-PP composites at high temperature. The cone calorimeter tests revealed that the introduction of IFR greatly decreased the combustion parameters, such as heat release rate (HRR), smoke production rate (SPR) and so on. After water resistance test, the combustion parameter for IFR-PP was slightly increased. The scanning electron microscopy (SEM) tests indicated the introduction of IFR benefited to the formation of a sufficient, intumescent and homogeneous char layer on the materials surface during burning, which effectively prevented the underlying materials from further degradation and combustion. The structure and morphology of char layer for IFR-PP remained very well after water treated, consequently the water-treated IFR-PP presented excellent flame retardancy.

Effect of Processing Conditions on Flexural Strength Properties of Chicken Feather Fibre (CFF) and Its Hybrid Composites with Polypropylene Resin

ABSTRACT This study discusses the effect of molding temperature, pressure and time on the final compression-molded hybrid composites with polypropylene resin for its flexural strength. The results of tests conducted to characterize the hybrid composites developed with different proportion of fibers and processing conditions are discussed in this study. When comparing the overall results on the flexural strength of the composites, 25:75 Chicken Feather Fiber (CFF)/Jute composite showed highest flexural strength by keeping minimum temperature, maximum pressure and medium time. The influence of pressure on flexural strength is significant compared to temperature and time. As time increases the flexural strength decreases.

(Invited) Designed Polymers for Antifouling Surfaces

There is a strong demand for antifouling surface. To create such antifouling surface, there are some approaches such as chemical reaction at the surface, coatings, internal additives, etc. We are developing polymers that can modify the surface property by easy treatments based on precise design and synthesis of the polymers. Biomedical synthetic materials, such as poly(ethylene terephthalate) (PET) and polypropylene (PP), are prone to adhesion of proteins, cells, and bacteria, causing functional failures in implants, artificial organs, catheters, and diagnostic devices, and increasing the risk of secondary infections. One of the promising answers is a hydrophilic polymer brush surface on which many polymer chains are connected in high density to inhibit adsorption of proteins and following adhesion of related biomolecules and cells. Such high density polymer brush is usually built by surface-initiated living radical polymerization through several chemical steps and polymers applied for medical devices are rather inert to chemical modification than inorganic materials. We thus created a new star shaped heteroarm polymer consisting of hydrophilic chains, as an antifouling block, and hydrophobic chains, as a substrate attaching block, for a biocompatible coating material, which is supposed to form polymer brush-like structure by simple coating procedure. The coating surface exhibited very good resistance to adhesion of platelets, bacteria, fibroblasts, and proteins although the corresponding linear polymer exhibited moderate resistance. This result indicates utilization of unique architecture of the star polymer is effective for building condensed polymer brush structure at the surface. Perfluoroalkyl group-containing polymer shows water/oil repellency. Although long perfluoroalkyl groups (longer than C8) exhibit high repellency, they can not be employed because of the environmental reason, nowadays. Shorter perfluoroalkyl groups (less than C8) give less effect to environment but they have less repellency. We thud designed block copolymers consisting of fluorine and non-fluorine containing monomers and evaluated the sequence effects as an internal additive to PP resin to improve oil repellency. By controlling fluorinated/non-fluorinated monomer sequence, the oil repellency of the fluorinated polymer-added polypropylene (PP) was dramatically improved compared to that modified with the randomly sequenced fluoropolymer. For instance, random copolymer consisting of 2-(perfluorohexyl)ethyl methacrylate (C6FMA) and stearyl methacrylate (StMA) gave slightly higher contact angle (13º) than that of non-additive PP (6º). Compared to the random copolymer, the diblock and triblock copolymer lead much higher contact angles (23º and 38º, respectively) when only 1wt% of the fluoropolymer was mixed into PP. This result indicates sequence regulation of fluorinated/non-fluorinated monomer in the fluoropolymer is effective to concentrate fluorine groups at the resin surface resulting in improvement of water/oil repellency.

Crystallization and mechanical properties of basalt fiber-reinforced polypropylene composites with different elastomers

In this study, composites based on polypropylene (PP), basalt fiber (BF), polypropylene-graft-maleic anhydride (MAPP) and different elastomers were manufactured by extrusion compounding and injection molding. The main focus of this study was to comparatively investigate the effect of three kinds of elastomers (ethylene–propylene–diene monomer (EPDM), polyethylene–octene (POE) and ethylene–vinyl–acetate (EVA)) on non-isothermal crystallization and mechanical properties of the composites with various BF contents. The tensile test results showed that BF had a reinforcing effect on PP resin, and the addition of MAPP further improved the tensile properties by the enhancement of PP/BF interfacial bonding. Among the elastomers, EPDM was more effective in improving the tensile strength and tensile modulus, while POE significantly toughened the impact strength. Micrographs of scanning electron microscope on the impact fracture surfaces indicated a good dispersion by the addition of POE and EPDM, while some agglomerations were observed in the presence of EVA. The non-isothermal crystallization kinetics were investigated based on Avrami and Mo equations at six different cooling rates by using differential scanning calorimetry. Micrographic images of polarized optical microscopy showed that the spherulite size of PP reduced in the presence of EPDM and EVA.

Improvement of toughness of polypropylene resin by addition of cellulose nanofibers

Improvement of toughness of polypropylene resin by addition of cellulose nanofibers

Curved Bistable Composite Slit Tubes with Positive Gaussian Curvature

An investigation into the bistability of positively curved laminated composite slit tubes is presented, establishing a natural extension in this area that has previously been focused on straight tubes. Curved slit tubes are modeled as the surface segments of a torus. The design space is explored through a parametric study to investigate the effect on the second stable state, representing a small coil. This includes the effects of longitudinal curvature, cross-section subtending angles, nonuniform transverse curvature, and spatially varying laminate properties. The second equilibrium state is determined through strain energy minimization using the Rayleigh–Ritz method. To verify the model, samples are manufactured from glass-fiber braid and polypropylene resin. This investigation finds 1) the initial curvature along the length of the tube has little effect on coil radius, however, the coil has a distinct barrel shape; 2) highly enclosed and 3) highly curved cross-sections result in higher edge strains of the second equilibrium, enabling identification of practical bistable tubes; and 4) conversely, the greater the initial curvature along the length of the tube, the lower the second equilibrium strain.