Comparative study of maleated polypropylene as a coupling agent for recycled low‐density polyethylene/wood flour composites

The effects of the type of coupling agent and virgin polypropylene (PP) content on the mechanical properties and water absorption behavior of recycled low‐density polyethylene/wood flour (WF) composites were investigated. The fractured surfaces of these recycled wood/plastic composites (rWPCs) were examined to gain insight into the distribution and dispersion of WF within the polymer matrix. The results indicate that the use of 100% recycled polymer led to inferior mechanical properties and to a greater degree of moisture absorption and swelling when compared to recycled polymer–virgin PP wood/plastic composites. This could have been related to the poor melt strength and inferior processability of the recycled polymer. The extent of improvement of the mechanical properties depended not only on the virgin PP content in the matrix but also on the presence of maleic anhydride (MA) modified PP as the coupling agent. Higher concentrations of MA group were beneficial; this improvement was attributed to increased chemical bonding (ester linkages) between hydroxyl moieties in WF and anhydride moieties in the coupling agent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Comonomer effect on the mechanical and morphological behavior on the calcite‐filled PP,CoPP, and TerPP

Comonomer effect on the mechanical and morphological behavior of the calcite (stearic acid coated calcium carbonate)‐filled polypropylene (PP), poly(propylene‐random‐ethylene) copolymer (CoPP), and poly(propylene‐co‐ethylene‐co‐1‐butene) terpolymer (TerPP) composites were investigated by using dumbbell bar and film specimens. The tensile properties of the calcite‐filled PP, CoPP, and TerPP composites exhibited lower values than those of the pure polymers (calcite‐unfilled polymers), whereas the complex viscosity of the calcite‐filled polymers exhibited slightly higher values than that of the pure polymers. Mechanical properties studied by using various strain rates and draw ratios rationalized in terms of comonomer units and contents in various PP systems. Morphological behavior of the specimens stretched at various strain rates and draw ratios was investigated by using SEM microphotographs and the mechanism of the formation of air holes was proposed. The air hole initiated from crack propagation and followed by dewetting between the calcite surface and the polymer interface in the weakened region. The crack propagated along the transverse direction; then the air hole developed parallel to the machine direction with fibril structure of the resin in PP and CoPP systems. However, TerPP composite exhibited no cracks in the beginning of the elongation, but the air hole was initiated due to dewetting; then its enlargement was exhibited by broken fibril structure of the resin. In the final stage of stretching, the air hole was dominated by merging of the neighboring air holes. Thus, different comonomer units, which are the small content of ethylene and 1‐butene in CoPP and TepPP, are responsible for these systems behaving in a different manner on the mechanical and morphological properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2041–2053, 2002     

Enhanced fracture energy during deformation through the construction of an alternating multilayered structure for polyolefin blends

The effects of polymer blend components on the phase morphology, crystallization behavior and mechanical performance of materials processed by high speed thin‐wall injection molding (HSTWIM) and compression molding (CM) processes were investigated. High density polyethylene (HDPE) and polypropylene (PP) containing different ratios of rubber phase (0%, 18% and 21%) were selected to construct different blends. HSTWIM is shown to trigger the formation of a multilayered structure for these blends with oriented polymer crystals and epitaxial growth of HDPE crystals on PP. Such a layered structure is thought to provide a good template for morphological control of various functional polymer composites. Moreover, the addition of rubber in the multilayered structure with the rubber phase partially distributed between layers is observed. These issues are thought to be responsible for the much enhanced fracture energy compared with specimens from CM. The structural details and formation mechanism of these layered structures consisting of different compositions were investigated. Such a study could provide some guidelines for the preparation of high performance bio‐mimic materials or various functional polymer composites with alternating multilayered structure. © 2018 Society of Chemical Industry     

Phase modification of SEBS block copolymer by different additives and its effect on morphology,mechanical and dynamic mechanical properties

The objective of this study is to examine the phase modification of styrene–ethylene butylene–styrene (SEBS) block copolymer by different additives and its influence on morphology and mechanical, and dynamic mechanical properties. The additives chosen are the coumarone–indene (CI), phenol–formaldehyde (PF), paraffin hydrocarbon (PAHY) resins, as well as aromatic oil (AO), polystyrene (PS), polypropylene (PP), ethylene vinyl acetate (EVA) (VA 28 and 45%), and ethylene propylene diene monomer (EPDM) rubber. It is interesting to note that of all the additives, PP has the most prominent effect. The mechanical properties of SEBS polymer are enhanced to a large extent by PP. The value of tan δ maximum of SEBS at both the low and the high temperature transitions is decreased. All the resins and PS increase the storage modulus and the tensile modulus of the SEBS polymer. CI resin and AO modify the hard and soft phases of SEBS polymer. AO, EPDM rubber, and EVA lower the mechanical strength of the SEBS polymer. The results are explained on the basis of morphologystudied with the help of scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2015–2025, 1998     

Roles of additives in scratch resistance of high crystallinity polypropylene copolymers

Scratch behavior in neat and talc‐filled high crystallinity polypropylene (PP) copolymers containing various additives is investigated using a cosntant load scratch test and two types of indentation tests (Rockwell and Shore D). The talcfilled PP copolymer exhibits high scratch visibilityand scratch depth. The addition of a nucleating agent or lubricant improves the scratch resistance of the talc‐filled PP copolymer. Differential scanning calorimetry, scanning electron microscopy and attenuated total reflectance Fourier transform infrared spectroscopy are used to characterize crystallinity morphology and scratch mechanisms in PP systems. It is found that the scratch resistance of the PP copolymer systems investigated, in terms of scratch depth and scratch visibility, depends mainly on the fracture features generated during the scratch process. The influences of talc, nucleating agent and lubricant on the scratch behavior of PP are discussed.     

Study of the morphology and mechanical properties of polypropylene composites with silica or rice‐husk

The mechanical, morphological behavior and water absorption characteristics of polypropylene (PP) and silica, or PP and rice‐husk, composites have been studied. The silica used in this study as filler was a commercial type produced from soluble glass or rice husks. The compatibilizing effect of PP grafted with monomethyl itaconate (PP‐g‐MMI) and/or with vinyltriethoxysilane (PP‐g‐VTES) as polar monomers on the mechanical properties and water absorption was also investigated. In general, a high loading of the studied fillers in the polymer matrix increases the stiffness and the water absorption capacity. This effect is more noticeable in the tensile modulus of the PP/silica composite with PP‐g‐VTES as compatibilizer. However, the increase of the rice‐husk charge as a natural filler in the PP matrix decreases the stiffness, and in the presence of PP‐g‐MMI as compatibilizer in PP/rice‐husk, the tensile modulus and water absorption of the composite were improved. The better adhesion and phase continuity in the PP/silica and PP/rice‐husk composites with different compatibilizers was confirmed by the morphological study. Copyright © 2004 Society of Chemical Industry     

Preparation of polypropylene and polystyrene with NCO and NH2 functional groups and their applications in polypropylene/polystyrene blends

Isocyanate‐ and amine‐functionalized polypropylene (PP) and polystyrene (PS) were prepared through grafting and copolymerization method. These compounds are used as precursors for PP‐graft‐PS (PP‐g‐PS) copolymers and reacted at the matrix interface of PP/PS blends. Functionalized polymer structures were characterized by ¹H NMR and FTIR spectroscopy. The effects of the synthesized compatibilizer on the rheological and morphological behavior of PP/PS blends were investigated systematically. Results showed that the functional polymer was successfully synthesized, and the additional two different compatibilizer systems dramatically decreased the size of the dispersed phase domains in PP/PS blends. Compared with the uncompatibilized blends, compatibilized blends exhibited a slightly higher crystallization temperature because the melting points of the blend components were not evidently affected by the addition of compatibilizer, as revealed by differential scanning calorimetry. The compatibilizer effect on the PP/PS blends was reflected through rheological property and dynamic mechanical analysis. POLYM. ENG. SCI., 55:614–623, 2015. © 2014 Society of Plastics Engineers     

Optimization of flame retardant content with respect to mechanical properties of natural fiber polymer composites: Case study of polypropylene/flax/aluminum trihydroxide

Flammability behavior of natural fiber polymer composites (NFPC) is an essential factor to define their scope of application. It was of great importance to quantitatively optimize the quantities of the flame retardants (FR) with respect to the corresponding mechanical properties as well as the flame retardance behavior. Flax/polypropylene (PP) system was selected in this study due to its diverse applications. Aluminum trihydroxide (ATH) which was an inorganic hydrate was used as a FR and smoke suppresser because of its environmentally–friendly nature. Flax and PP in the presence of a coupling agent were extruded together. Flax loading with respect to the host polymer was studied at 30% and 50%. Afterward, the compounds were mixed with three grades of ATH namely Apyral 32, 40CD, and 60CD which were loaded at different amounts ranging from 30 to 60 wt%. The synergetic effect of zinc borate (ZB) and ammonium polyphosphate Exolit AP‐422 was also investigated. Both mechanical and flammability behavior were assessed with respect to ATH and its synergists. It was found that 40 wt% of Apyral 60CD was enough to reach V‐0 level with a marginal loss of tensile strength namely 12.5% and 7% for samples of 30% and 50% flax, respectively. Higher loading of ATH at 60% results in strength reduction by 37%–40%. Cone calorimetry results proved the reduction of both heat release rate (HRR) and smoke release. Synergism with both additives improved the UL94 rating and decreased the HRR as well. POLYM. COMPOS., 37:3310–3325, 2016. © 2015 Society of Plastics Engineers     

Abrasive water jet machining and mechanical behavior of banyan tree saw dust powder loaded polypropylene green composites

Banyan tree saw dust powder (BSD) filled Polypropylene (PP) green composites have been fabricated with varying amounts viz., 0%, 20%, and 40% of BSD particulate filler by using a co‐rotating twin screw extruder followed by injection molding. The mechanical properties such as surface hardness, tensile behavior, and impact strength of the fabricated PP/BSD green composites have been studied in order to standardize the composites. Abrasive water jet (AWJ) machining has been reported mainly for ceramics, concrete, and glass but not much literature is available on AWJ machining of polymer composites. This research is aimed at examining the AWJ machining of green polymer composites. The effect of BSD loading on the AWJ machining behavior of the PP/BSD green composites has been investigated. Furthermore, the effect of addition of 4% maleic anhydride grafted PP (coupling agent) and 4% talc (mineral filler) on the machining behavior of PP/BSD composites has also been evaluated. Surface roughness and optical micrographs of the AWJ cut composite specimens were examined to assess the effect of BSD content, AWJ traverse speed and pressure on the machining behavior of the composites. In order to probe the mechanism of AWJ machining behavior of PP/BSD composites, the kerf width and taper have been measured and results are correlated. POLYM. COMPOS., 37:1754–1764, 2016. © 2014 Society of Plastics Engineers     

改性聚磷酸铵对三嗪类膨胀阻燃聚丙烯性能的影响

由改性聚磷酸铵(APP)、自制的三嗪类成炭发泡剂(CFA)等复配制成膨胀型阻燃剂(IFR),以二氧化硅、二氧化钛等为协效剂阻燃聚丙烯(PP)。研究了不同组分的IFR及协效剂对阻燃PP复合材料阻燃性能、力学性能和耐水性能的影响。结果表明:改性APP的亲水性下降;由改性APP/CFA(4/1)、二氧化硅协效剂复配的PP复合材料阻燃性能、力学性能优良,助剂在PP基体中分散性好,热水浸泡后氧指数为32.5%,仍能达到UL94V—1级,失重率为2.92%。     

Thermal,morphological, and mechanical characteristics of polypropylene/polybutylene terephthalate blends with a liquid crystalline polymer or ionomer

Thermotropic side‐chain liquid crystalline polymer (SLCP) and corresponding side‐chain liquid crystalline ionomer (SLCI) containing sulfonate acid were used in the blends of polypropylene (PP) and polybutylene terephthalate (PBT) by melt‐mixing respectively, and thermal behavior, morphological, and mechanical properties of two series of blends were investigated by differential scanning calorimetry, Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy, and tensile measurement. Compared with the immiscible phase behavior of PP/PBT/SLCP blends, SLCI containing sulfonate acid groups act as a physical compatibilizer along the interface and compatibilize PP/PBT blends. FTIR analyses identify specific intermolecular interaction between sulfonate acid groups and PBT, and then result in stronger interfacial adhesion between these phases and much finer dispersion of minor PBT phase in PP matrix. The mechanical property of the blend containing 4.0 wt % SLCI was better than that of the other blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4712–4719, 2006     

Comparison of calibration with poly(propylene glycol) and poly(styrene) standards in size exclusion chromatography measurements for characterization of oligo(lactone) macromonomers

A series of polypropylene (PP) blends were toughened by various impact modifiers with different mechanical characteristics. The impact, tensile dilatometry and dynamic mechanical behavior of these PP/high impact polypropylene (HIPP) blends was studied. The results showed that the impact strength of PP improves significantly with the addition of a higher content of HIPP which has the lowest flexural modulus and yield strength. This was due to the formation of shear yielding bands in the slow crack growth zone ahead of the notch tip. However, the PP blends modified with HIPP of higher flexural modulus exhibited much lower impact strength owing to these dispersed particles initiate crazes in the slow crack growth zone. Received: 27 January 1997/Revised: 31 March 1997/Accepted: 2 April 1997     

Structural,thermal, morphological and dynamic mechanical characteristics of waste‐reinforced polypropylene composites: A novel approach for recycling electronic waste

An in‐depth investigation has been carried toward utilizing polymer‐rich nonmetallic fraction of printed circuit boards (PCBs) as reinforcing fillers in polypropylene (PP) composites. The influence of waste additions (up to 25 wt %) on structural, thermal, morphological, and dynamic mechanical behavior of PP composites was investigated using a range of analytical techniques. The incorporation of PCB waste was found to affect the crystalline morphology resulting in the formation of smaller spherulites. The presence of glass fibers in PCB waste promoted the formation of β‐crystal enhancing the mechanical properties of composites. Thermal analysis showed a maximum increase of ～15 °C in the crystallization onset temperature (T_co) suggesting the nucleating effect of the filler, a feature also supported by structural investigations. Polarized microscopy revealed a reduction in the spherulite size after 5 wt % PCB waste loading owing to the presence of large number of nucleation sites. The incorporation of waste also increased the thermal stability of composites increasing the final degradation temperature by up to 14 °C. Dynamic mechanical properties of PP/PCB waste composites were determined in the temperature range ?20 to 155 °C; a significant increase in the storage modulus further confirmed the reinforcing effect of waste additives. This investigation has shown that the nonmetallic fraction of PCB waste could be used as a cost‐effective reinforcing filler for PP, providing an environmental friendly route to utilize electronic waste in value‐added products. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43389.     

Toughening and reinforcing of polypropylene

To improve the mechanical properties of polypropylene (PP), some elastomers and fillers are used. The impact properties and tensile strength are affected by both the mineral additives and the polymer additives. There are also some changes in the thermal properties. To improve the interfacial adhesion, some low molecular polymers are added to assist the dispersion of the fillers and the uniformity of the various polymers with PP. The addition of low-density polyethylene (LDPE), high-density polyethylene (HDPE), or the styrene–butylene–styrene block copolymer (SBS) can improve the impact properties of PP. The propylene–ethylene copolymer has a more pronounced effect than does the physical blending of PP with PE. Calcium carbonate can reinforce PP resin. The ethylene–vinyl acetate copolymer (EVA) has an effect on the printing properties of the PP. © 1996 John Wiley & Sons, Inc.     

Influence of grafted polypropylene on the mechanical properties of mineral‐filled polypropylene composites

The purpose of this work was to study how mineral fillers would behave in a polypropylene (PP) matrix when PP modified with maleic anhydride (MA) and/or itaconic acid (IA) was used as a coupling agent in the preparation of mineral‐filled PP composites. The composites were characterized with tensile mechanical measurements and morphological analysis. The optimum amount of the coupling agent to be used to obtain composites with improved mechanical properties was established. The results indicated that these coupling agents enhanced the tensile strength of the composites significantly, and the extent of the coupling effect depended on the nature of the interface that formed. The incorporation of coupling agents enhanced the resistance to deformation of the composite. The behavior of IA‐modified PP as a coupling agent was similar to that of a commercial MA‐modified PP for the filled PP composites. Evidence of improved interfacial bonding was revealed by scanning electron microscopy studies, which examined the surfaces of fractured tensile test specimens; their microstructures confirmed the mechanical results with respect to the observed homogeneous or optimized dispersion of the mineral‐filler phase in these composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2343–2350, 2007     

Mechanical properties,morphological structure,and thermal behavior of dynamically photocrosslinked PP/EPDM blends

A dynamically photocrosslinked polypropylene (PP)/ethylene–propylene–diene (EPDM) rubber thermoplastic elastomer was prepared by simultaneously exposing the elastomer to UV light while melt‐mixing in the presence of a photoinitiator as well as a crosslinking agent. The effects of dynamic photocrosslinking and blend composition on the mechanical properties, morphological structure, and thermal behavior of PP/EPDM blends were investigated. The results showed that after photocrosslinking, tensile strength, modulus of elasticity, and elongation at break were improved greatly. Moreover, the notched Izod impact strength was obviously enhanced compared with corresponding uncrosslinked blend. Scanning electron microscopy (SEM) morphological analysis showed that for uncrosslinked PP/EPDM blends, the cavitation of EPDM particles was the main toughening mechanism; whereas for dynamically photocrosslinked blends, shear yielding of matrix became the main energy absorption mechanism. The DSC curves showed that for each dynamically photocrosslinked PP/EPDM blend, there was a new smaller melting peak at about 152°C together with a main melting peak at about 166°C. Dynamic mechanical thermal analysis (DMTA) indicated that the compatibility between EPDM and PP was improved by dynamic photocrosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3371–3380, 2004     

Rheological,mechanical, thermal,and morphological properties of polypropylene/ethylene‐octene copolymer blends

Rheological and morphological studies were performed on polymer blends of ethylene‐octene copolymer [polyethylene elastomer (PEE)] and polypropylene (PP). The viscosities of PEE, PP, and PEE/PP blends were analyzed using an Instron capillary rheometer and a Rheometrics Dynamic Stress Rheometer, SR 200. A non‐Newtonian flow behavior was observed in all samples in the shear rate range from 27 to 2700 s⁻¹, whereas at shear rates in the range from 0.01 to 0.04 s⁻¹, a Newtonian flow behavior was verified. The scanning electron micrographs showed that dual‐phase continuity may occur between 50 and 60 (wt %) of PEE. This result is consistent with the Sperling's model. The mechanical analysis showed that PEE/PP, with 5 wt % of PEE, presented an increase on the mechanical properties and as the PEE content increased, a negative deviation in relation to an empirical equation was observed. Thermal analysis showed that there were no change in the crystallization behavior of the matrix when different elastomer contents were added. Dynamic mechanical thermal analysis showed that samples with low PEE contents presented only one peak, indicating a certain degree of miscibility between the components of these blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 692–704, 2000     

Understanding the viscoelastic properties of extruded polypropylene wood plastic composites

The main goal of this study was to analyze the effect of process additives, that is, maleated polypropylene (MAPP), and a nucleating agent on the viscoelastic properties of different types of extruded polypropylene (PP) wood plastic composites manufactured from either a PP homopolymer, a high crystallinity PP, or a PP impact copolymer using dynamic mechanical thermal analysis. The wood plastic composites were manufactured using 60% pine wood flour and 40% PP on a Davis‐Standard Woodtruder?. Dynamic mechanical thermal properties, polymer damping peaks (tan δ), storage modulus (E′), and loss modulus (E″) were measured using a dynamic mechanical thermal analyzer. To analyze the effect of the frequency on the dynamic mechanical properties of the various composites, DMA tests were performed over a temperature range of ?20 to 100°C, at four different frequencies (1, 5, 10, and 25 Hz) and at a heating rate of 5°C/min. From these results, the activation energy of the various composites was measured using an Arrhenius relationship to investigate the effect of MAPP and the nucleating agent on the measurement of the interphase between the wood and plastic of the extruded PP wood plastic composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1638–1644, 2003     

Numerical simulation of bubble growth in viscoelastic fluid with diffusion of dissolved foaming agent

Viscoelastic simulations of bubble growth in polypropylene (PP) physical foaming were performed. A multimode Phan‐Thien Tanner (PTT) model was used to analyze the dynamic growth behavior of spherically symmetric bubbles with the diffusion of a foaming agent (CO₂). Changes in the dissolved foaming agent concentration in the polymer and in the strain of the polymer melt surrounding the bubbles were simulated with the Lagrangian FEM method. The simulation technique was validated by comparison with the bubble growth data, which were experimentally obtained from visual observations of the PP/CO₂ batch foaming system. The simulation results demonstrated that the strain‐hardening characteristic of polymer does not strongly affect the bubble growth rate. The linear viscoelastic characteristic is more influential, and the relaxation mode around 0.01 s is the most important factor in determining the bubble growth rate during the early stage of foaming. A multivariate analysis for the simulation results was also carried out. This clarified that bubble nucleus population density, surrounding pressure, initial dissolved foaming agent concentration, and diffusion coefficient are more important factors than the viscoelastic characteristics. POLYM. ENG. SCI., 45:1277–1287, 2005. © 2005 Society of Plastics Engineers     

Structural properties and mechanical behavior of injection molded composites of polypropylene and sisal fiber

Composites based on isotactic polypropylene (PP) and sisal fiber (SF) were prepared by melt mixing and injection molding. The melt mixing characteristics, thermal properties, morphology, crystalline structure, and mechanical behavior of the PP/SF composites were systematically investigated. The results show that the PP/SF composites can be melt mixed and injection molded under similar conditions as the PP homo‐polymer. For the composites with low sisal fiber content, the fibers act as sites for the nucleation of PP spherulites, and accelerate the crystallization rate and enhance the degree of crystallinity of PP. On the other hand, when the sisal fiber content is high, the fibers hinder the molecular chain motion of PP, and retard the crystallization. The inclusion of sisal fiber induces the formation of β‐form PP crystals in the PP/SF composites and produces little change in the inter‐planar spacing corresponding to the various diffraction peaks of PP. The apparent crystal size as indicated by the several diffraction peaks such as L_(110)α, L_(040)α, L_(130)α and L_(300)β of the α and β‐form crystals tend to increase in the PP/SF composites considerably. These results lead to the increase in the melting temperature of PP. Moreover, the stiffness of the PP/SF composites is improved by the addition of sisal fibers, but their tensile strength decreases because of the poor interfacial bonding. The PP/SF composites are toughened by the sisal fibers due to the formation of β‐form PP crystals and the pull‐out of sisal fibers from the PP matrix, both factors retard crack growth.