Preparation,structure, and properties of the PTT/SGF composites

Short glass fiber reinforced poly(trimethylene terephthalate) composites (PTT/SGF) were prepared by twin screw extruder. The structural feature and physical properties of these composites were studied by scanning electron microscope, differential scanning calorimetry, thermalgravimetric analyzer, capillary rheometer, universal tester, etc. The glass fiber was modified by the silane coupling agent before being blended with the polymer. The results suggest that there is strong interaction between SGF and PTT matrix, which leads to an increasing on the tensile strength, Young's modulus, impact strength and thermal stability of the composites with proper contents of SGF. Rheological behavior of the PTT/SGF composites melt is complicated, combining a dilate fluid at lower shear rate and a pseudo-plastic fluid at higher shear rate. The melt apparent viscosity of composites decreases with increasing SGF content because of the rigid fibers improving the flow of the melt. Moreover, the flow activation energy of the composites suggests that the melt with more SGF has lower sensitivity to the processing temperature. In conclusion, the composite with 10–20 wt% content of SGF has better properties. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Structure and Mechanical Properties of Composites of Poly(6‐hexanelactam) Combining Solid Tribological Additives and Reinforcing Components

Summary: Three types of composites of polyamide 6 (PCL) with hybrid tribological additives were synthesized via anionic adiabatic “in situ” polymerization of 6‐hexanelactam (ε‐caprolactam) initiated with metallic sodium and activated with either cyclic trimer of phenyl isocyanate or diphenylmethane 4,4′‐diisocyanate. Combinations of the additives and their maximum applied concentrations (in wt.‐%) were the following: MoS₂/graphite(G)/oil(O) (5/16/9), short carbon fibers (CF)/G/O (5/20/10), and copper phthalocyanine (CPC) (7). Dynamic mechanical thermal analysis (DMTA) indicates a secondary (β) transition at about ?65 °C and the main (α) transition at temperatures close to 20 °C; the storage modulus passes through a shallow maximum as a function of the total content of additives. Tensile creep and indentation creep concurrently evidenced some increase in compliance with rising fraction of incorporated compounds. Stress‐strain tests in flexure show that flexural strength and toughness monotonically decreased with the content of MoS₂/G/O or CF/G/O, whereas the flexural modulus passed through a flat maximum. On the other hand, the strength and modulus were decreasing with CPC content, while toughness and Charpy impact tests showed some improvement.

Flexural toughness a_fU as a function of filler content C_ad in adiabatic anionic polymerization of 6‐hexanelactam.     

Gradient Composites of Alkaline Poly(6‐hexanelactam) with Graphite: One‐Step Synthesis,Structure, and Mechanical Properties

In a one‐step synthesis of gradient composites, molten monomer of 6‐hexanelactam was mixed with graphite (5 wt.‐%) and alkaline polymerization was performed under quasi‐isothermal conditions at about 170°C. The following initiator/activator system insensitive to traces of water and other low‐molecular‐weight compounds adsorbed on filler surface was used: the sodium salt was prepared through the reaction of sodium dicaprolactamobis(2‐methoxyethoxo)aluminate with 6‐hexanelactam; N‐acyllactam was formed in situ in molten monomer by solving flexible or rigid polyurethane foam consisting of either toluene diisocyanate or diphenylmethane‐4,4′‐diisocyanate, and a poly(propylene oxide) based polyol. To obtain gradient composites with a compositional variation between plane‐parallel surfaces, the incorporated filler underwent sedimentation due to gravity during initial stages of polymerization. The graphite‐free surface is suitable for treatment with adhesives, while the graphite‐rich surface layer (containing about 11 wt.‐% of graphite) possesses improved friction characteristics. Graphite slightly (i) reduces the polymer yield and the mean spherulite diameter; (ii) increases the crystallinity due to its nucleation activity; (iii) decreases the compliance, but does not affect its time dependence given by the matrix and (iv) reduces the yield strength, tensile strength and elongation at break. The friction coefficient of the graphite‐rich surface is reduced to almost 50% of that found for the graphite‐free surface; composites with cross‐linked matrix also show better wear properties.     

Effects of polyamide 6 incorporation to the short glass fiber reinforced ABS composites: an interfacial approach

The properties of 30 wt% short glass fiber (SGF) reinforced acrylonitrile-butadiene-styrene (ABS) terpolymer and polyamide 6 (PA6) blends prepared with extrusion were studied using the interfacial adhesion approach. Work of adhesion and interlaminar shear strength values were calculated respectively from experimentally determined interfacial tensions and short beam flexural tests. The adhesion capacities of glass fibers with different surface treatments of organosilanes were evaluated. Among the different silanes tested, γ-aminopropyltrimethoxysilane (APS) was found to be the best coupling agent for the glass fibers, possibly, because of its chemical compatibility with PA6. Tensile test results indicated that increasing amount of PA6 in the polymer matrix improved the strength and stiffness of the composites due to a strong acid–base interaction at the interface. Incorporation of PA6 to the SGF reinforced ABS reduced the melt viscosity, broadened the fiber length distributions and increased the toughness of the composites. Fractographic analysis showed that the incorporation of PA6 enhanced the interactions between glass fibers and the polymeric matrix.     

Study on morphological,rheological, and mechanical properties of PP/SEBS‐MA/SGF hybrid composites

Hybrid composite samples composed of polypropylene as matrix, 20% short glass fibers (SGF) as reinforcement and varying amount of maleic anhydride (MA) grafted SEBS as compatibilizer and impact modifier were prepared by melt mixing in a modular twin screw extruder. The SEM examination performed on cryogenically fractured surfaces of hybrid samples showed a three‐phase type morphology in which SGF and rubber phase finely distributed in the PP matrix. SEM results also revealed that in the hybrid samples containing SEBS‐MA, the surface of the SGF are coated with a thin layer of SEBS‐MA, indicating a strong adhesion between SGF and matrix materials. The results of rheological studies showed nearly equal viscosity for compatible and incompatible hybrid samples. Tensile yield strength enhanced with increasing rubber content up to 10% above which it decreased and highest impact strength enhancement was obtained for sample containing 20% rubber. The impact strength of composites was found to be increased with increasing the SGF content. In final, it was shown that a good balance between stiffness and toughness could be achieved by adjusting the SGF and rubber content in this ternary system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2704–2710, 2007     

Effect of functionalized elastomer addition on mechanical and interfacial properties of poly (butylene terephthalate)/glass fiber composites

In this study the effect of incorporation of ethylene‐co‐glycidylmethacrylate (GMA)‐co‐n‐butyl acrylate (nBA) terpolymer with an epoxy functional group, on the mechanical performance of short glass fiber (SGF)/Poly (butylene terephthalate) (PBT) composites has been investigated. Tensile test showed that incorporation of rubber phase in PBT/SGF composites results in loss of strength. However impact measurement exhibited an increase in impact strength with an increase in rubber content. Tensile and impact properties are discussed in terms of interfacial shear strength and morphology of composites. Morphological observation by SEM revealed a thin layer of polymer adhering to the surface of glass fibers indicating that epoxy functional group in the modifier reacts with fiber surface and PBT matrix. This reactivity of epoxy functional group is also supported by FTIR observations. The composites are also analyzed for % crystallinity using DSC and a strong correlation is found to exist between interfacial shear strength and % crystallinity. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Short glass fiber reinforced ABS and ABS/PA6 composites: Processing and characterization

In this study acrylonitrile‐butadiene‐styrene (ABS) terpolymer was reinforced with 3‐aminopropyltrimethoxysilane (APS)‐treated short glass fibers (SGFs). The effects of SGF concentration and extrusion process conditions, such as the screw speed and barrel temperature profile, on the mechanical properties of the composites were examined. Increasing the SGF concentration in the ABS matrix from 10 wt% to 30 wt% resulted in improved tensile strength, tensile modulus and flexural modulus, but drastically lowered the strain‐at‐break and the impact strength. The average fiber length decreased when the concentration of glass fibers increased. The increase in screw speed decreased the average fiber length, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength were affected negatively and the strain‐at‐break was affected positively. The increase in extrusion temperature decreased the fiber length degradation, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength increased. At higher temperatures the ABS matrix degraded and the mechanical strength of the composites decreased. To obtain a strong interaction at the interface, polyamide‐6 (PA6) at varying concentrations was introduced into the ABS/30 wt% SGF composite. The incorporation and increasing amount of PA6 in the composites broadened the fiber length distribution (FLD) owing to the low melt viscosity of PA6. Tensile strength, tensile modulus, flexural modulus, and impact strength values increased with an increase in the PA6 content of the ABS/PA6/SGF systems due to the improved adhesion at the interface, which was confirmed by the ratio of tensile strength to flexural strength as an adhesion parameter. These results were also supported by scanning electron micrographs of the ABS/PA6/SGF composites, which exhibited an improved adhesion between the SGFs and the ABS/PA6 matrix. POLYM. COMPOS. 26:745–755, 2005. © 2005 Society of Plastics Engineers     

Effects of styrene-isoprene copolymer glass fiber coatings on woven glass cloth epoxy composite performance

Woven glass-epoxy composites were prepared from mats that had been treated in a variety of ways. Fibers were coated with a commercial sizing, no sizing, and a surfactant coating. In addition, fibers were coated with styrene-isoprene copolymers at varying molar ratios using a novel technique termed admicellar polymerization. Dynamic contact angle measurements were used to quantify the effect of the different coating techniques on the fiber, while dynamic mechanical analysis (DMA) and flexural testing were used to characterize the cured composites. Wetting studies conducted with EPON 828 resin revealed no difference in wetting for the polymer-treated fiber compared to the commercially-treated fiber. Aqueous wetting results were consistent with a surfactant layer adsorbed on the polymer treated and surfactant treated fiber surface. DMA established that both the polymer and surfactant treatment depressed the alpha transition temperature of the composite and suggested an interpenetrating network existed at the fiber-matrix interface. Flexural strength testing showed the properties of the composites made from surfactant-treated and polymer-treated glass fibers were comparable to composites made from commercially-sized fibers and exceeded the flexural strength of the composite made from glass fibers without sizing.     

EOC-g-MAH共混增韧SGF/PP泡沫复合材料的制备及力学性能

采用型内二次发泡工艺制备了马来酸酐接枝乙烯-1-辛烯共聚物(EOC-g-MAH)共混增韧短玻璃纤维(SGF)/聚丙烯(PP)泡沫复合材料,考察了EOC-g-MAH含量对复合材料的泡孔形貌、微观结构和力学性能的影响。结果表明,EOC-g-MAH的引入改善了泡沫体的发泡效果,平均孔径减小约35%,泡孔密度提高近4倍且分布均匀。SGF与基体间的界面结合得到显著增强,且EOC-g-MAH在SGF表面形成了颗粒黏附结构,大幅提高了SGF/PP泡沫复合材料的冲击韧度,并在质量分数为8%时达到最大值,增幅为77%。随着EOC-g-MAH质量分数的增加,SGF/PP泡沫复合材料的抗弯强度先增加后降低,而压缩强度则呈近似线性下降的变化趋势。     

One‐Step Synthesis of Hybrid Composites of Poly(6‐hexanelactam) Combining Solid Tribological Additives and Reinforcing Components

Four types of composites of polyamide 6 with hybrid tribological additives were synthesized via anionic adiabatic “in situ” polymerization of 6‐hexanelactam (ε‐caprolactam) initiated with metallic sodium and activated with cyclic trimer of phenyl isocyanate or diphenylmethane 4,4′‐diisocyanate. The optimization of the initiator/activator systems in the range of 0.3 to 1.2 mol‐% and of the initial polymerization temperatures from 125 to 150 °C preceded the composite preparation. Combinations of fillers and their maximum applied concentrations (in wt.‐%) were the following: MoS₂/graphite/oil (5/16/9), carbon fibers/graphite/oil (5/20/10), copper phthalocyanine (7), and B₂O₃ (11). Analysis of selected composites encompassed water extraction, DSC, and DMTA measurements. All tested fillers decreased the polymerization rate, polymer yield, melting temperature and crystalline fraction. Polymerization rate constants of the neat polyamide 6 obtained for various initial temperatures obeyed the Arrhenius plot giving an average activation energy value of 78.6 kJ · mol^?1.

Rate of polymerization as a function of the total fillers content in adiabatic anionic polymerization of 6‐hexanelactam (A: MoS₂ + G/O, Na/PIC, B: CPC, Na/MDI, C: MoS₂ + G/O, Na/MDI, D: CF + G/O Na/MDI).     

Preparation and performance characteristics of short‐glass‐fiber/maleated styrene–ethylene–butylene–styrene/polypropylene hybrid composites

Eighty/twenty polypropylene (PP)/styrene–ethylene–butylene–styrene (SEBS) and 80/20 PP/maleated styrene–ethylene–butylene–styrene (SEBS‐g‐MA) blends reinforced with 30 wt % short glass fibers (SGFs) were prepared by extrusion and subsequent injection molding. The influence of the maleic anhydride (MA) functional group grafted to SEBS on the properties of SGF/SEBS/PP hybrid composites was studied. Tensile and impact tests showed that the SEBS‐g‐MA copolymer improved the yield strength and impact toughness of the hybrid composites. Extensive plastic deformation occurred at the matrix interface layer next to the fibers of the SGF/SEBS‐g‐MA/PP composites during impact testing. This was attributed to the MA functional group, which enhanced the adhesion between SEBS and SGF. Differential scanning calorimetry measurements indicated that SEBS promoted the crystallization of PP spherulites by acting as active nucleation sites. However, the MA functional group grafted to SEBS retarded the crystallization of PP. Finally, polarized optical microscopy observations confirmed the absence of transcrystallinity at the glass‐fiber surfaces of both SGF/SEBS/PP and SGF/SEBS‐g‐MA/PP hybrid composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1303–1311, 2002     

Synthesis and characterization of short Grewia optiva fiber‐based polymer composites

Natural fibers, such as Flax, Sisal, Hibiscus Sabdariffa, and Grewia optiva (GO) possess good reinforcing capability when properly compounded with polymers. These fibers are relatively inexpensive, easily available from renewable resources, and possess favorable values of specific strength and specific modulus. The mechanical performance of natural fiber‐reinforced polymers (FRPs) is often limited owing to a weak fiber‐ matrix interface. In contrast, urea–formaldehyde (UF) resins are well known to have a strong adhesion to most cellulose‐containing materials. This article deals with the synthesis of short G. optiva fiber‐reinforced UF polymer matrix‐based composites. G. optiva fiber‐reinforced UF composites processed by compression molding have been studied by evaluating their mechanical, physical, and chemical properties. This work reveals that mechanical properties such as: tensile strength, compressive strength, flexural strength, and wear resistance of the UF matrix increase up to 30% fiber loading and then decreases for higher loading when fibers are incorporated into the polymer matrix. Morphological and thermal studies of the matrix, fiber, and short FRP composites have also been carried out. The swelling, moisture absorbance, chemical resistance, and water uptake behavior of these composites have also been carried out at different intervals. The results obtained lay emphasis on the utilization of these fibers, as potential reinforcing materials in bio‐based polymer composites. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Thermoplastic composties of polystyrene: Effect of different wood species on mechanical properties

Both softwood (spruce) and hardwood (aspen and birch) species in the form of different pulps (e.g., sawdust, chemithermomechanical pulp, explosion pulp and OPCO pulp) have been used (10–40 wt% composite) as reinforcing fillers for thermoplastic composites of polystyrene. Mechanical properties, are examined, e.g., tensile modulus, tensile strength at maximum point, and the corresponding elongation and energy as well as impact strength of compression molded composites. To improve the compatability of wood fibers which are hydrophilic and the polymer matrix which is hydrophobic, poly[methylene(polyphenyl isoeyanate)] (2 and 8 wt % of polymer) was used as a coupling agent. The mechanical properties of the treated composites are improved up to 30% in fiber content whereas a downward trend for untreated composites was observed when an increase in fiber content occurred. The overall improvements in mechanical properties due to the addition of isocyanate can be explained by the linkage of isocyanate molecules with fiber matrix through the chain of covalent bonds and the interaction of π-electrons of benzene rings of polystyrene as well as isocyanate. As a result, poly[methylene(polyphenyl isocyanate)] forms a bridge between fiber and polymer on the interfaces. This result is instrumental for efficient stress transfer between cellulose fibers and thermoplastics. The performance of different pulps of various wood species as reinforcing fillers for thermoplastic composites is also examined.     

Thermal and morphological behavior of irradiated composite materials based on injection‐moulded recycled polyethylene terephthalate

The effect of gamma irradiation and short glass fiber (SGF) on the thermal and morphological behavior of the recycled poly (ethylene terephthalate) (rPET) in the presence of reactive additive (epoxy resin, 2 wt %) has been investigated. Characterization of the resulted composites to evaluate the effect of incorporation the SGF and irradiation by means of differential scanning calorimetry, X‐ray diffraction, thermal gravimetric analysis, and scanning electron microscopy (SEM). The results show that the SGF and epoxy resin behave as nucleating agents for the crystallization of rPET. A noticeable increase in the rPET thermal stability in the presence of both SGF and epoxy resin has been observed. Furthermore, the rPET melting temperature (T_m) slightly decrease in the presence of the SGF and remains nearly constant with the incorporation of the epoxy resin. On the other hand, the rPET crystallinity percent (X%) decreases in the presence of SGF and gamma irradiation. The SEM showed that a layer of epoxy resin was coated onto the SGF in the rPET matrix. This coating layer raises the interfacial shear strength between the fiber and polymer matrix and also increases with gamma irradiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Improvement of interfacial interactions in CF/PEEK composites by an s-PSF/graphene oxide compound sizing agent

The interfacial interactions of carbon fiber (CF)-reinforced polymer composites is a key factor affecting the overall performance of the material. In this work, we prepared a sulfonated poly(ether sulfone)–graphene oxide mixed sizing agent to modify the interface of CF/PEEK composites and improve the interfacial properties between the PEEK matrix and CF. Results showed that the mechanical and interfacial properties of CF/PEEK composites are improved by the sizing agent. Specifically, the flexural strength, flexural modulus and interlaminar shear strength of the materials reached 847.29 MPa, 63.77 GPa, and 73.17 MPa, respectively. Scanning electron microscopy confirmed markedly improved adhesion between the resin matrix and fibers. This work provides a simple and effective method for the preparation of high-performance CF/PEEK composites, which can improve the performance of composites without degrading the mechanical property of pristine CF.     

Adhesion improvement in glass fiber reinforced polyethylene composite via admicellar polymerization

Admicellar polymerization (polymerization of monomer solubilized in adsorbed surfactant bilayers) has been used to form a thin film of polyethylene onto the surface of milled glass fibers using sodium dodecyl sulfate as the surfactant. The decrease in ethylene pressure was used to follow the solubilization and adsolubilization processes as well as the reaction processes. An increase in initiator (Na₂S₂O₈) to surfactant ratio gave thicker and more uniform coatings of polymer onto the glass fiber surface according to SEM micrographs. Although a substantial amount of ethylene polymerized in solution according to the pressure drop, the decrease in pressure attributed to admicelle polymerization corresponded to the amount of polymer formed on the glass fiber, indicating little, if any, solution polymer deposited on the fibers. The admicellar‐treated glass fiber was used to make composites with high‐density polyethylene. The composites showed an increase in tensile and flexural strength over composites made from as‐received glass fiber, indicating an improvement in the fiber‐matrix adhesion of the admicellar‐treated glass fiber.     

Studies of the effect of fiber surface and matrix rheological properties on nonwoven reinforced elastomer composites

The influence of fiber type and fiber-surface properties on matrix flow behavior was investigated using structural reaction injection-molding (SRIM). The influence of fiber type, fiber-surface properties, and matrix type on strength properties in elastomeric composites reinforced with nonwoven fibrous structures was investigated using tensile tests on elastomer composite samples from SRIM and latex coagulation (LC) fabrication methods and the microbond strength method on individual fibers. The fibers used were PET, LLDPE, and p-aramid. Fibers were treated with epoxy, styrene, and isocyanate derivatives, which make the surface chemically reactive. Treatments were also made with NaOH and a copolymer of polyester and polyol ether, causing a change in the fiber surface energy. The matrix types were polyurethane elastomer and natural rubber. The results show that the surface treatments which produced a change in the surface energy influenced the flow rate of the matrix polymer during the composite fabrication process. The treatments resulted in chemically reactive fiber surfaces which improved the fiber-matrix bond strength without affecting the Young's modulus of the composite material. Good correlation was found between bond strength and surface energy including the dispersive component of surface energy in the case of polyurethane elastomer and surface-modified PET fibers. The age of the polyurethane matrix has a marked influence on the bond strength. The fiber volume fraction in composites has a strong influence on the Young's modulus of the elastomer composite. © 1995 John Wiley & Sons, Inc.     

Studies on the isothermal crystallization kinetics and crystal morphology of PTT/SGF composites

The kinetics of isothermal crystallization and crystal morphology of poly(trimethylene terephthalate)/short glass fibers (PTT/SGF) composites were investigated by using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). DSC data was analyzed by the Avrami equation and Hoffman‐Lauritzen theory. The results show that SGF plays a role as the nucleating agent, which largely accelerates the crystallization rate of PTT. SGF below 20% will increase the crystallinity of the composites but 30% SGF will decrease the crystallinity, which is also verified by the crystallinity results calculated from the wide‐angle x‐ray diffraction (WAXD) experiments. The crystal morphology of the composites exhibits so much microcrystallites because of the fast crystallization rate and the strong interaction between SGF and polymers, which is consistent with the results analysized by the Avrami theory. The nuclei exponent K_g is increased sharply as the SGF added into polymer, and SGF makes PTT easier to crystallize during isothermal crystallization process. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Morphology/behavior relationship and recyclability of composites based on PP/EPDM blends and short aramid fibers

The effect of short aramid fibers on the mechanical behavior of polypropylene (PP) and ethylene‐propylene‐diene (EPDM) and their blends has been investigated by means of an experimental design. The results have shown that aramid fibers are very effective reinforcing agents for composites when the continuous phase of the matrix is constituted by PP, so sensible increments in tensile modulus and strength are obtained as fiber content in the composites increases. An optimal matrix composition and fiber content has been observed that produced high abrasion resistance compounds. However, the abrasion resistance of very rich EPDM matrices is hardly affected by fibers content. The addition of fibers to EPDM rich (>50%) matrices gives rise to a sensible decrease of the impact strength of this polymer. However, at PP contents above 50% in the polymer matrix, an increase of impact strength is observed at fiber percentages in the composites above 10%. The different behavior of the fibers depending on matrix type can be attributed to a better affinity of these fibers for PP matrix. Morphological studies of the composites have been carried out by scanning electron microscopy. Finally, the price and recyclability of these materials have been analyzed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2474–2484, 2002