Reinforced Polypropylene Research Articles

Flammability of Bamboo Fabric Reinforced Polypropylene Composites and their Hybrids

Hybridisation is introduced as one way to use bamboo fabric as natural fibre reinforced composites (NFRCs). The research intends to determine the extent to which bamboo fabric can replace glass fibre in glass polypropylene (GPP) composites and whether the proposed hybrids are capable of competing, particularly in comparison to the flammability of GPP composites. This study evaluates the effect of hybridization on the flammability properties of bamboo fabric reinforced polypropylene composites and their hybrids. Flammability tests using cone calorimeter show that the peak Heat Release Rate (HRR) was reduced up to 39% for BPP50%, at 511.8 kW/m2, in comparison with that of neat PP, based on maximum peak values of 842 kW/m2. Interestingly, in the hybrid composites, the peak HRR reduced as glass fibre was replaced with bamboo fibre. These composites demonstrate a significant decrease in peak HRR, over 30% less than the neat PP and GPP composites respectively. These results indicate that a significant portion of the glass in GPP may be replaced with bamboo fabric, with a positive effect on fire resistance. This reduction in flammability and the improved properties obtained demonstrate promise for these hybrid materials in future applications.

Reinforcement of polypropylene with lignocellulose nanofibrils and compatibilization with biobased polymers

ABSTRACTFreeze‐dried and milled lignocellulose nanofibrils (LCNF) were used to reinforce polypropylene (PP) nanocomposites. The LCNF, containing up to 9% lignin, was obtained from residual Empty Palm Fruit Bunch (EPFB) fibers. Soy protein isolate (SPI) and hydroxypropyl cellulose (HPC) were tested as coupling agents as well as maleic anhydride grafted polypropylene (MAPP), which was used as a reference. A good level of dispersion of LCNF in the PP matrix while mechanical testing and thermal analyses indicated an improvement of the thermo‐mechanical behavior of the nanocomposites was revealed upon loading of the lignin‐containing nanofibrils. The tensile modulus of PP was increased by 15% upon the addition of 1% LCNF with SPI as a compatibilizer. Likewise, the thermal stability of the composites was most markedly enhanced. Overall, LCNF and SPI, two important bioresources, are introduced here for the development of novel and cost‐effective PP‐based composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43854.

Semichemical fibres of Leucaena collinsii reinforced polypropylene composites: Flexural characterisation, impact behaviour and water uptake properties

Abstract Leucaena collinsii is a legume genus with interesting properties for soil recovering. This study uses it as reinforcement in polypropylene reinforced composites. Composites from 20 to 50% w/w composites with a 6% of coupling agent (over the weight of fibre) were produced and injected. Flexural, impact and water uptake behaviour was studied. The flexural strength and stiffness increased as the reinforcement was increased. The impact strength decreased for un-notched samples, but increased for notched samples. The sample's fracture was observed by SEM. Both fibrilar and granular fibre fractures could be recognized. Regarding the water uptake, despite observing no influence on the diffusion coefficient, the maximum water uptake capacity enhanced when the L. collinsii was increased.

Mechanical properties and biocompatibility of functionalized carbon nanotubes/polypropylene composites

This study investigates the efficiency of carbon nanotubes (CNTs) as reinforcement for polypropylene (PP) for biocompatible application as a function of different surface functionalization of CNTs. PP composites were reinforced using various CNTs: single- and multi-walled carbon nanotubes (SWCNTs, MWCNTs), SWCNTs were covalently functionalized by plasma, for comparison, the MWCNTs were functionalized noncovalently. Different CNTs were incorporated into PP by solution blending. The type of CNTs and surface functionalization affects the mechanical and biocompatibility results significantly. Differences in nanostructure and the chemical compositions, number of functional groups, and structural defects for the CNTs may be the key factors affecting the mechanical properties and biocompatibility of PP nanocomposites compared to the neat PP. Finally, suitable CNTs and surface functionalization of CNTs were selected for making the PP/CNTs composites.

Modification of pineapple leaf fiber surfaces with silane and isocyanate for reinforcing thermoplastic

Pineapple leaf fiber (PALF) was treated by silane and isocyanate treatments at 0–20% prior to being used as reinforcement in low-density polyethylene (LDPE) and polypropylene (PP) composites. The reactive groups of silane and isocyanate on PALF surface were confirmed by Fourier transform infrared spectroscopy. Scanning electron micrographs also showed the fiber surface coated with layers of treated chemicals as compared with the untreated one. These surface treatments reduced the water absorption of PALF. The physical properties of the PALF-reinforced composites were investigated. The resulting composites possessed higher tensile strength and lower crystallinity than the untreated composites. Silane treatment gave better PALF/LDPE composites in terms of composite strength as compared to isocyanate treatment. For treated PALF/PP composites, fiber pullout was reduced both silane and isocyanate treatments.

Realizing simultaneous reinforcement and toughening in polypropylene based on polypropylene/elastomer via control of the crystalline structure and dispersed phase morphology

Realizing simultaneous reinforcement and toughening in polypropylene based on polypropylene/elastomer via controlling crystalline structure and dispersed phase morphology.

Irradiated Jute Reinforced Polypropylene Composites: Effect of Mercerization and SEM Analysis

Jute fibres (Corchorus olitorious L.), an environmentally and ecologically friendly product, were chemically modified and treated as surface treatment which was carried out by mercerizing jute fabrics with aqueous solutions of NaOH (5,10 and 20%) at different soaking times (30, 60 and 90 minutes) and temperatures (0, 25 and 50°C). These mercerized jute fabric reinforced polypropylene composites were fabricated by composition molding technique and equated with virgin jute fabric reinforced polypropylene composites, fabricated by same technique. The above composite samples ware compared by evaluating the mechanical parameters such as tensile strength, tensile modulus, bending strength, bending modulus. The effect of mercerization on weight and dimension of jute fabrics was studied. Mechanical properties of mercerized jute-PP composites ware measured and found highest at 20% NaOH at 0°C for 60 min soaking time. Alkali treatment helped in the development of hydrophobicity and reduction in volume fraction of the porosity. This may be due to the better fibre matrix interface adhesion caused due to the fibre surface treatment by alkali. The optimized formulation was irradiated by γ radiation at different dosage (100, 150, 200, 250 & 500 Krad). Among them 250 Krad showed highest mechanical properties

Surface Treatment of Coconut Fiber and its Application in Composite Materials for Reinforcement of Polypropylene

This work describes the surface treatment of coconut fiber and its application in composite materials for reinforcement of polypropylene. Before testing coconut fiber in composite materials, its susceptibility to chemical treatment was characterized by exposure to the following: (1) hot water; (2) aqueous NaOH 2% (w/v); and (3) a sequence of chemical treatments in hot water, extran 20% (v/v), acetone/water 1:1 (v/v), and aqueous NaOH 10% (w/v).The efficiency of each treatment was evaluated by Fourier transform infrared spectrometry analysis, indicating a reduction in the C=O peak. Besides that the scanning electron microscope revealed that treatment changed the morphology of the fibers. Thermogravimetric analysis showed that the insertion of fibers into PP caused a decrease in the thermal stability and differential scanning calorimetry exhibited that crystallization of PP was favored in the presence of fibers.

Characterization of Potential Exposures to Nanoparticles and Fibers during Manufacturing and Recycling of Carbon Nanotube Reinforced Polypropylene Composites

Carbon nanotube (CNT) polymer composites are widely used as raw materials in multiple industries because of their excellent properties. This expansion, however, is accompanied by realistic concerns over potential release of CNTs and associated nanoparticles during the manufacturing, recycling, use, and disposal of CNT composite products. Such data continue to be limited, especially with regards to post-processing of CNT-enabled products, recycling and handling of nanowaste, and end-of-life disposal. This study investigated for the first time airborne nanoparticle and fibers exposures during injection molding and recycling of CNT polypropylene composites (CNT-PP) relative to that of PP. Exposure characterization focused on source emissions during loading, melting, molding, grinding, and recycling of scrap material over 20 cycles and included real-time characterization of total particle number concentration and size distribution, nanoparticle and fiber morphology, and fiber concentrations near the operator. Total airborne nanoparticle concentration emitted during loading, melting, molding, and grinding of CNT-PP had geometric mean ranging from 1.2 × 10(3) to 4.3 × 10(5) particles cm(-3), with the highest exposures being up to 2.9 and 300.7 times above the background for injection molding and grinding, respectively. Most of these emissions were similar to PP synthesis. Melting and molding of CNT-PP and PP produced exclusively nanoparticles. Grinding of CNT-PP but not PP generated larger particles with encapsulated CNTs, particles with CNT extrusions, and respirable fiber (up to 0.2 fibers cm(-3)). No free CNTs were found in any of the processes. The number of recycling runs had no significant impact on exposures. Further research into the chemical composition of the emitted nanoparticles is warranted. In the meanwhile, exposure controls should be instituted during processing and recycling of CNT-PP.

Deconsolidation and Its Interdependent Mechanisms of Fibre Reinforced Polypropylene

Thermoplastic composites offer the possibility of post processing by re-melting of the polymer, but this can lead to a loss of consolidation. The aim of this study is to investigate and quantify the mechanisms leading to deconsolidation. A model is introduced based on the first law of thermodynamics including the following mechanisms: decompaction of the fibre reinforcement network affected by the stored energy during compaction, void evolution due to the surface tension and the gas expansion, moisture in the polymer, and external pressure. These deconsolidation mechanisms are interdependent and have a significant effect on deconsolidation. The modeling approach predicts the deconsolidated state with good agreement to physical measurements.

English

English

Effect of alkali treatment on Alfa fibre as reinforcement for polypropylene based eco-composites: Mechanical behaviour and water ageing

This paper aims at investigating the effect of alkali treatment and water ageing on several short Alfa fibre reinforced polypropylene composites. For this purpose, different composites with untreated and treated fibres were elaborated by extrusion and injection moulding processes and subjected to water ageing. The obtained results showed that the alkali treatment enhances significantly the Young’s modulus and tensile strength of the Alfa fibre reinforced polypropylene composites and reduces their loss during water ageing. The acoustic emission analysis showed that the use of alkali treatment plays a major role in the improvement of the fibre-matrix interface of both unaged and aged composites.

Molecular level analysis of carbon nanofiber reinforced polymer composites

The present study focuses on modeling of carbon nanofibers (CNFs) and evaluating the effect of their reinforcement in polypropylene (PP) matrix. A novel approach for modeling of CNF has been explained in this study. Molecular dynamics (MD) simulation has been used to study the effect of CNF volume fraction ( Vf) and aspect ratio ( l/d) on mechanical properties of CNF–PP composites. Materials Studio 5.5 has been used as a tool for finding the modulus and damping in composites. CNF composition in PP was varied by volume from 0 to 16%. Aspect ratio of CNF was varied from l/d = 5 to l/d = 100. Results have also been obtained for longitudinal loss factor ( η11). To the best of the knowledge of the authors, till date there is no study, either experimental or analytical, which predicts η11 for CNF–PP composites at nanoscale. Hence, this will be a valuable addition in the area of nanocomposites. Results show that with only 2% addition by volume of CNF in PP, E11 increases by 748%. Thereafter, the increase is at a lower rate. Increase in E22 is very less in comparison to the increase in E11. With increase in CNF aspect ratio ( l/d) till l/d = 60, the longitudinal loss factor ( η11) decreases rapidly. Thereafter, the decrease is smaller. Results of this study are in agreement with those predicted by Shinichi et al.

Tensile Properties of Polypropylene Composites Reinforced with Mechanical, Thermomechanical, and Chemi-Thermomechanical Pulps from Orange Pruning

This paper explores the evolution in the tensile strength of orange pruning fiber-reinforced polypropylene composites. The exploitation of these pruning’s can effectively avoid incineration, with the consequence of CO2 emissions and fire risk, while extending the value chain of the agricultural industry. This biomass was subjected to three different treatments yielding mechanical, thermomechanical, and chemi-thermomechanical pulps. It was found that 20 to 50% of these pulps, together with a coupling agent, were used as polypropylene reinforcement. The evolution in the tensile strength and morphological properties of the fibers, and the effect of treatments on these properties were analyzed. A modified rule of mixtures (mROM) was used to analyze the micromechanical properties of the interface. In addition, the mechanical properties were weighted against the fiber treatment yields. Finally, factors to compute the net contribution of the fibers to the final strength of the composite materials were proposed.

Tensile and Impact Strength of Coir Fibre Reinforced Polypropylene Composites: Effect of Different Temperature Conditions

This study focuses on tensile properties and impact strength of coir fibre reinforced polypropylene composites under influences of fibre loading and various temperatures conditions. All samples were fabricated by using hot-press technique. Tensile and izod impact samples were prepared in accordance to the standard specifications as closely as possible. Three different ratios of fibre with matrix which were 10%, 20% and 30% were studied. The results revealed that 20% volume fraction of coir fibre demonstrated optimum tensile and impact properties. Significance reduction of impact strength under low temperature condition had been shown for all composites due to the brittleness of both fibre and matrix.

Effect of chemical treatments on flax fibre reinforced polypropylene composites on tensile and dome forming behaviour.

Tensile tests were performed on two different natural fibre composites (same constituent material, similar fibre fraction and thickness but different weave structure) to determine changes in mechanical properties caused by various aqueous chemical treatments and whether any permanent changes remain on drying. Scanning electronic microscopic examinations suggested that flax fibres and the flax/polypropylene interface were affected by the treatments resulting in tensile property variations. The ductility of natural fibre composites was improved significantly under wet condition and mechanical properties (elongation-to-failure, stiffness and strength) can almost retain back to pre-treated levels when dried from wet condition. Preheating is usually required to improve the formability of material in rapid forming, and the chemical treatments performed in this study were far more effective than preheating. The major breakthrough in improving the formability of natural fibre composites can aid in rapid forming of this class of material system.

Chemical surface modification of wheat straw fibers for polypropylene reinforcement

The use of natural materials has grown in the last years in the plastics industry. Natural lignocellulose fibers derived from agricultural waste present potential to be used as a replacement for glass fibers for polymer reinforcement, leading to lower CO2 footprint products. However, cellulose fibers are hydrophilic and polar and as a result of that, incompatible with hydrophobic polymers such as polypropylene. For this reason, a surface modification on the cellulose fiber is required. This work focuses on the modification of the cellulose fibers to improve the compatibility with polypropylene. Wheat straw fibers derived from agricultural waste were scoured with the purpose to remove lignin, hemicellulose and pectin to facilitate the defibrillation. The fibers were then esterified using acetic anhydride. Thermal gravimetric tests have shown an increase in the thermal stability of the scoured and esterified cellulose fibers, from 246°C for untreated fibers to 292°C and 316°C, respectively. From mechanical tests results it could be seen that the tensile modulus of the composites with esterified cellulose fibers increased 57% compared with the neat PP. Flexural strength increased by 31% and flexural modulus by 70%. The use of esterified fibers led to an improvement of 79% in the impact strength compared with the neat PP. A better compatibilization between fibers and matrix could be seen using maleic anhydride modified polypropylene copolymer as compatibilizer, even with esterified fibers, probably due to residual hydroxyl groups still available on modified cellulose. POLYM. COMPOS., 37:2133–2141, 2016. © 2015 Society of Plastics Engineers

Structural performance of dry-cast rubberized concrete pipes with steel and synthetic fibers

A study was conducted to address the enhancement of the structural performance of concrete pipes through the use of crumb rubber, steel, and synthetic (polypropylene) fibers. Based on the three-edge bearing (3EB) test according to ASTM standard C497, pipes with five different dry-cast concrete mixtures were produced and tested: (1) reinforced concrete pipe (RCP), (2) crumb rubberized concrete pipe (CRP), (3 and 4) steel or polypropylene fiber reinforced rubberized concrete pipe (SFP or PFP), and (5) hybrid fiber reinforced rubberized concrete pipe (HYP). This study investigates how the variation of the fiber volume fraction and crumb rubber content in the dry cast concrete mix affects the behavior of pipes with diameters of 600mm (24in.) and 900mm (36in.). The crumb rubber particles replaced from 3% to 20% (by volume) of fine aggregate in the mixture used for concrete pipes. A series of rubberized concrete mixes were employed with a variation in the fiber volume fraction (Vf) (steel: 0.17% and 0.33%, polypropylene: 0.13%, 0.33%, 0.52% and 0.65%). Thirty-one rubberized concrete pipes were developed by incorporating different dosages of steel and polypropylene fibers and their combinations. Test results revealed that hybrid fiber reinforcements (both steel and polypropylene fibers) were more effective than single type fiber reinforcement (steel or polypropylene fibers) in enhancing the rubberized concrete pipe strength and ductility. In order to reach the strength requirement for Class III (96kN/m/m) and Class II (72kN/m/m) according to ASTM C76, fine aggregates can be replaced with an equal volume of crumb rubber up to 3% and 5% in HYPs, respectively, for the rubberized concrete pipes produced with zero-slump concrete.

Physical and Thermal Characterization of Alkali Treated Rice Husk Reinforced Polypropylene Composites

Rice husk (RH) reinforced polypropylene- (PP-) based composites were prepared by compression molding. The RH was treated with sodium hydroxide solution (1 wt%); then composites were prepared using varying percentages of RH (5 to 20 wt%). The thermomechanical, spectroscopic, and morphological properties of the prepared composites (RH-PP) were investigated. The scanning electron microscopic (SEM) analysis showed better interfacial adhesion between alkali treated RH and the matrix PP. The Fourier Transform Infrared (FTIR) spectra confirmed the chemical bonding.The results revealed that physical properties as well as thermal stability of the composites improved significantly with the addition of alkali treated RH in PP matrix.

Effect of High Impact Loading on Nanoclay Reinforced Polypropylene

Except for few attempts to show the high impact load effect, the difference in level of contribution of nanoclay on polymers at their quasi-static and dynamic mechanical behaviors is a lacuna in the available literature. Quasistatic and dynamic responses of a high impact copolymer polypropylene (PP) in its neat and nanoclay-filled forms are presented in this study. The study helped in percentage quantification of differences in nanoclay effect, imposed by the very nature of loadings. The PP-nanoclay nanocomposite (PP+5 wt%nc) is prepared by melt compounding of 5 wt% nanoclay (nc) with PP using twin screw extruder. Tensile specimens for UTM (Universal Testing Machine) were prepared using injection molding machine. Dynamic loading specimens were made for SHPB (Split Hopkinson Pressure Bar) using an extruded sheet. The experiments were performed at strain rates of 10-2 s-1 and 2.2*104 s-1 for quasi-static and dynamic loadings respectively. As a result, the contribution of 5 wt% nanoclay on PP at quasi-static loading is shown to be 2.6%, 10.8% and 13% on Yield stress, Young’s modulus and toughness, respectively. However, significantly different results are observed after dynamic loading experiments. Intense improving contributions of 506% and 53% in impact modulus and impact toughness respectively are observed. While, minor reduction (3.5%) in plateau (Yield) stress is experienced in the case of dynamic impact loading.