Wetting kinetics and adhesion strength between polypropylene melt and glass fibre: influence of chemical reactivity and fibre roughness

A systematic experimental investigation with the purpose of quantifying the effect of the interactions between non-polar (unmodified) and polar (modified) polypropylene melts and treated fibre surfaces during wetting has been performed. The glass fibres were sized by aminosilane (γ-APS), γ-APS/polyurethane film former (γ-APS/PU) and γ-APS/polypropylene film former (γ-APS/ PP). Unsized fibres were used for comparison and were also coated with an azidosilane layer. Zeta potential and contact angle measurements were employed to investigate the surface properties of the treated glass fibres. The surface roughness was characterised using both atomic force microscopy and scanning electron microscopy. A method based on axisymmetric drop shape analysis was employed to determine the surface tension of the polymer melt. The wetting of the fibres by the polymer melt was investigated using the Wilhelmy balance technique. The wetting kinetics was different for different fibre surface treatments. The chemically reactive system based on azidosilane showed a better wetting than the other systems. The aminosilane/polypropylene film former (γ-APS/PP) treated fibre was also characterised by a fast wetting, most probably due to the physical similarity between the polymer and the fibre sizing and, thus, probable compatibility. In the receding case the differences between the reactive systems were smaller than they were for the advancing case. Higher adhesion tension calculated from the wetting measurements correlated well with higher adhesion strength determined from single fibre pull-out tests.     

Effect of fibre length and chemical modifications on the tensile properties of intimately mixed short sisal/glass hybrid fibre reinforced low density polyethylene composites

Hybrid composites prepared by the incorporation of two or more different types of fibres into a single polymer matrix deserve much attention. This method of hybridisation of composites offers a profitable procedure for the fabrication of products while the resulting materials are noted for their high specific strength, modulus and thermal stability. The influence of the relative composition of short sisal/glass fibres, their length and distribution on the tensile properties of short sisal/glass intimately mixed polyethylene composites (SGRP) was examined. Different compositions of sisal and glass such as 70/30, 50/50 and 30/70 have been prepared with varying fibre lengths in the range of 1–10 mm. Emphasis has also been given to the variation of fibre–matrix adhesion with several fibre chemical modifications. Chemical surface modifications such as alkali, acetic anhydride, stearic acid, permanganate, maleic anhydride, silane and peroxides given to the fibres and matrix were found to be successful in improving the interfacial adhesion and compatibility between the fibre and matrix. The nature and extent of chemical modifications were analysed by infrared spectroscopy while improvement in fibre–matrix adhesion was checked by studying the fractography of composite samples using a scanning electron microscope. Assessment of water retention values has been found to be a successful tool to characterize the surface of the stearic acid modified fibres. It was found that the extent of improvement in tensile properties of SGRP varied with respect to the nature of chemical modifications between fibre and matrix. Improved mechanical anchoring and physical and chemical bonding between fibre and polyethylene matrix are supposed to be the reasons for superior tensile strength and Young's modulus in treated composites. Several secondary reasons such as high degree of fibre dispersion and reduced hydrophilicity in chemically modified fibres also are believed to play a role. Among the various chemical modifications, the best tensile strength and modulus was exhibited by the SGRP with benzoyl peroxide treated fibres. This is attributed to the peroxide‐initiated grafting of polyethylene on to the fibres. Copyright © 2004 Society of Chemical Industry     

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     

EAA-g-PEOX对PBT/PP共混体系增容作用的研究

利用ＳＥＭ、ＤＳＣ及力学测试等分析方法,研究了增容剂ＥＡＡ－ｇ－ＰＥＯＸ及扩链剂ＰＢＯ对ＰＢＴ／ＰＰ共混物的形态结构和力学性能的影响。结果表明,ＥＡＡ－ｇ－ＰＥＯＸ明显改善了ＰＰ与ＰＢＴ的相容性,使ＰＰ较均匀地分配在基体中。     

Mechanical properties of maleic anhydride treated jute fibre/polypropylene composites

Abstract

The effect of maleic anhydride (MA) modification of jute fibre on the mechanical properties of jute/polypropylene (PP) composites was studied. Jute fibre, an environmental friendly, low-density renewable material was chemically modified with MA before the incorporation with PP to improve interfacial adhesion between them. Fourier transform infrared (FTIR) study showed that the C=C groups of MA attached to jute cellulose reacted with the PP matrix. Jute fibre/PP composite treated with MA displayed higher Young's modulus and dynamic storage modulus owing to the enhanced interfacial adhesion between the fibre and PP matrix. A scanning electron microscopy (SEM) study showed evidence of the enhanced adhesion and bridging in the interfacial region of the composite as the result of MA modification of jute fibre.     

高聚物共混纤维

共混技术是改善合成纤维性能的有效方法。介绍了共混纤维的分类和制造方法，讨论了高聚物的相容性及其对共混纤维的相态结构的影响，对影响基体－微纤型共混纤维的结构和性能的因素作了探讨，并给出了几个有代表性的共混纤维的实例。     

Processing and properties of mineral‐interfaced cellulose fibre composites

Polypropylene (PP) or, in some cases, poly (lactic acid) (PLA) were compounded with cellulosic fibres. The amount of fibres used was in the range 10–30 vol % and, in case of PP, a series of compounds was prepared with a minor amount of maleated PP as a compatibiliser. This matrix was denoted MAPP. Before compounding the polymers and the fibres, undelaminated bentonite (industrial scale) or delaminated clay (nanoclay) was deposited on the fibres in different amounts to improve the dispersion of the fibres in the polymer matrix, i. e., to avoid detrimental fibre bundles. The PP‐based compounds were either extruded or injection moulded, whereas the PLA‐compounds were only injection moulded. The mechanical properties were primarily evaluated for the injection moulded specimens. In general, the fibres had a strong effect on the mechanical behaviour of the materials, especially in the case of PLA and MAPP. Treating the fibres with undelaminated clay or nanoclay improved to some extent the dispersion of the fibres and the mechanical performance of the composites, but further optimization of the function of the mineral in this respect is probably required. The combination of the mineral treatment with a debonding agent appeared to be an interesting route here. With such a combination, a visually very good dispersion of the fibres in the PP‐based matrix could be obtained, partly at the expense of the mechanical performance. The compounding of the cellulosic fibres with PP led in this case to a marked decrease in the fibre length. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Tensile properties and creep response of polypropylene fibre composites with variation of fibre diameter

The mechanical properties and morphology of polypropylene (PP) long‐fibre reinforced random poly(propylene‐co‐ethylene) (PPE) composites (50/50 % vol/vol) have been investigated with reference to the fibre diameter with constant length. There is an improvement in the mechanical properties of PPE matrix by incorporation of long PP fibres into the matrix. The elastic modulus of the composite increased with decrease in the fibre diameter to 50 µm, to 0.91 GPa, which was 5 times higher than for pure PPE. However, composite stiffness decreased with decreasing fibre diameter of less than 50 µm and this is discussed in term of the fibre stiffness, packing, stress concentration and aspect ratio. Creep resistance of the composites showed the same behaviour. Morphology of the composites was investigated using scanning electron microscopy. This showed that there was a thin layer of matrix on the reinforcement, which was attributed to good impregnation and wetting of the fibres. Moreover, prediction of tensile modulus using the Cox model correlated well with experimental data. Copyright © 2004 Society of Chemical Industry     

Basic characterization of polypropene‐block‐poly(methylene‐1,3‐cyclopentane‐co‐propene) synthesized from propene and 1,5‐hexadiene with modified stopped‐flow method

Block copolymerization of propene and 1,5‐hexadiene was carried out by a modified stopped‐flow polymerization method with an MgCl₂‐supported Ziegler catalyst. The resulting polymer, polypropene‐block‐poly(methylene‐1,3‐cyclopentane‐co‐propene) (PP‐b‐(PMCP‐co‐PP)), in which the crystallizable PP part was linked with the non‐crystallizable PMCP‐co‐PP part, was characterized by optical microscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and tensile testing. The block copolymer having a chemical linkage between PP and PMCP‐co‐PP showed properties different from those of homopolymer, random copolymer and blend polymer. © 2001 Society of Chemical Industry     

In‐situ reinforcement of PBT/ABS blends with liquid crystalline polymer

Ternary in‐situ poly(butylene terephthalate) (PBT)/poly(acrylonitrile‐butadienestyrene) (ABS)/liquid crystalline polymer(LCP) blends were prepared by injection molding. The LCP used was a versatile Vectra A950, and the matrix material was PBT/ABS 60/40 by weight. Maleic anhydride (MA) copolymer and solid epoxy resin (bisphenol type‐A) were used as compatibilizers for these blends. The tensile, dynamic mechanical, impact, morphology and thermal properties of the blends were studied. Tensile tests showed that the tensile stregth of PBT/ABS/LCP blend in the longitudinal direction increased markedly with increasing LCP content. However, it decreased sharply with increasing LCP content up to 5 wt%; thereafter it decreased slowly with increasing LCP content in the transverse direction. The modulus of this blend in the longitudinal direction appeared to increase considerably with increasing LCP content, whereas the incorporation of LCP into PBT/ABS blends had little effect on the modulus in the transverse direction. The impact tests revealed that the Izod impact strength of the blends in longitudinal direction decreased with increasing LCP content up to 10 wt%; thereafter it increased slowly with increasing LCP. Dynamic mechanical analyses (DMA) and thermogravimetric measurements showed that the heat resistance and heat stability of the blends tended to increase with increasing LCP content. SEM observation, DMA, and tensile measurement indicated that the additions of epoxy and MA copolymer to PBT/ABS matrix appeared to enhance the compatibility between PBT/ABS and LCP.     

Valorization of poly(butylene terephthalate) wastes by blending with virgin polypropylene: Effect of the composition and the compatibilization

Blends of recycled poly(butylene terephthalate) (PBT) parts obtained from scrapped cars, and virgin polypropylene (PP), were prepared in a twin‐screw extruder at different compositions. Selected compositions were also prepared with the presence of ethylene‐co‐glycidyl methacrylate copolymer (E‐GMA) and ethylene/methyl acrylate/glycidyl methacrylate terpolymer (E‐MA‐GMA) compatibilizers. The effect of the composition and the type of compatibilizer, as well as the mixing conditions, on the morphology phase, thermal, viscoelastic behavior, and mechanical properties of the blends has been investigated. Blends PP/PBT of various composition exhibit a coarse morphology and a poor adherence between both phases, resulting in the decrease of ductility, whereas at weak deformation, PBT reinforced the tensile properties of PP. Addition of E‐GMA and E‐MA‐GMA to the PP/PBT blend exhibited a significant change in morphology and improved ductility because of interfacial reactions between PBT end chains and epoxy groups of GMA that generate EG‐g‐PBT copolymer. Moreover, thermal and viscoelastic study indicated that the miscibility of PP and PBT has been improved further and the reactions were identified. The E‐MA‐GMA results in the best improvement of ductility. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Influence of compatibilizers on the rheological,mechanical, and morphological properties of epoxidized natural rubber/polypropylene thermoplastic vulcanizates

In polymeric materials combining desirable properties, compatibility between constituent components of incompatible blends is necessary. The influence of two types of blend compatibilizers, a graft copolymer of maleic anhydride and polypropylene (PP) and phenolic‐modified PP, on the rheological, mechanical, and morphological properties of epoxidized natural rubber/PP thermoplastic vulcanizates was investigated at varied concentrations. All properties improved in a range of loading levels of compatibilizers at 0–7.5 wt % of PP. This was attributed to a chemical interaction between the different phases caused by the functionalized compatibilizers. Increasing chemical interaction between interfaces improved the interfacial tension and led to a microscale size of the dispersion. A decreasing trend in the properties was observed at compatibilizer levels higher than 7.5 wt % of PP because of segregation, which led to a third blend component dispersed in the PP matrix. The compatibilizers behaved as lubricants in the polymer melt flow. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Ultrathin Polypropylene Fibres from Polymer Blend Melts

The physicochemical characteristics of production of ultrathin polypropylene fibres from polymer blend melts by use of specific fibre-formation are examined. The determining role of thermodynamic compatibility in fibre formation of one polymer in another is demonstrated and a method is proposed for improving it by adding special substances — compatibilizers — to the binary mixture. The copolymer of ethylene and vinyl acetate and sodium oleate are recommended as compatibilizers for PP/CPA blends. The types of specific reaction between the copolyamide macromolecules and the additives were established by IR spectroscopy. These include dipole-dipole and ion-dipole bonds that alter the rheological properties and improve the spinnability of the blend melts. Specific fibre formation for a PP/CPA ratio corresponding to the phase shift region appeared for the first time due to compatibilization. Complex fibres are obtained from polypropylene microfibres in spinning through one opening.     

Comparison of olefin copolymers as compatibilizers for polypropylene and high‐density polyethylene

Some polyolefin elastomers were compared as compatibilizers for blends of polypropylene (PP) with 30 wt % high‐density polyethylene (HDPE). The compatibilizers included a multiblock ethylene–octene copolymer (OBC), two statistical ethylene–octene copolymers (EO), two propylene–ethylene copolymers (P/E), and a styrenic block copolymer (SBC). Examination of the blend morphology by AFM showed that the compatibilizer was preferentially located at the interface between the PP matrix and the dispersed HDPE particles. The brittle‐to‐ductile (BD) transition was determined from the temperature dependence of the blend toughness, which was taken as the area under the stress–strain curve. All the compatibilized blends had lower BD temperature than PP. However, the blend compatibilized with OBC had the best combination of low BD temperature and high toughness. Examination of the deformed blends by scanning electron microscopy revealed that in the best blends, the compatibilizer provided sufficient interfacial adhesion so that the HDPE domains were able to yield and draw along with the PP matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Short glass fibre reinforcedpoly(butylene terephthalate) Part 2 –Effect of hygrothermal aging onmechanical properties

Abstract

The mechanical properties of injection moulded poly(butylene terephthalate) (PBT) containing various loadings of short glass fibres (SGF) have been investigated. Properties studied include tensile, flexural, and impact. Effect of hygrothermal aging on the mechanical properties was investigated by immersing the respective specimens in distilled water at 30, 60, and 90°C. All the materials tested showed poor retention in mechanical properties upon exposure to hygrothermal aging. The effect became particularly pronounced at an immersion temperature of 90°C. Fractographic inspection of the fracture surfaces revealed that both PBT and SGF–PBT composites embrittled owing to a hydrolitic degradation process. Hydrolysis not only suppressed the matrix ductility but also reduced the bonding quality between PBT and SGF. Poor interfacial bonding was indicated by the absence of polymer matrix adhering to the fibre surfaces. The decrease in the impact strength of hygrothermally aged SGF–PBT composites provided further evidence that hygrothermal aging at high temperature reduces the contribution of fibre related toughening mechanisms. The residual mechanical properties of both PBT and its composites were not fully recovered after redrying. The permanent damage to these materials was attributed to severe hydrolytic degradation of PBT.     

Modification of surface properties of polypropylene films by blending with poly(ethylene-b-ethylene oxide) and its application

The possibility of improving the interfacial adhesion between polypropylene (PP) and polyamide layers (PA) has been investigated by means of addition of commercially available amphiphilic poly(ethylene-b-ethylene oxide) (P(E-b-EO)) block copolymers. These block copolymers were added to the PP matrix polymer in a twin screw extruder as integral additive. The change in surface properties of PP films upon incorporating P(E-b-EO) was investigated in model studies of blends prepared by casting PP/P(E-b-EO) solutions in 1,2-dichlorobenzene onto glass and Teflon Petri dishes, by melt pressing of PP/P(E-b-EO) blends between Teflon foils and glass substrates, or by melt extrusion of PP/P(E-b-EO) mixtures. The surfaces of the blend films were analyzed by attenuated total reflection Fourier transform infrared spectroscopy and water contact angle measurements. It was shown that an enrichment of the block copolymer at the surface of the blend depends highly on the conditions of film preparation and is driven by reducing the interfacial energy between the blend and the contacting medium. Effects of shear rate and residence time during normal processing conditions were also revealed. Blown film experiments with PP/P(E-b-EO) blends and PA were carried out for evaluating the effect of the integral P(E-b-EO) additive on the interfacial adhesion.     

The Use of Ethylene/Propylene Copolymers as Compatibilizers for Recycled Polyolefin Blends

Compatibilizing effects of ethylene/propylene (EPR) diblock copolymers on the morphology and mechanical properties of immiscible blends produced from recycled low‐density polyethylene (PE‐LD) and high‐density polyethylene (PE‐HD) with 20 wt.‐% of recycled poly(propylene) (PP) were investigated. Two different EPR block copolymers which differ in ethylene monomer unit content were applied to act as interfacial agents. The morphology of the studied blends was observed by scanning‐ (SEM) and transmission electron microscopy (TEM). It was found that both EPR copolymers were efficient in reducing the size of the dispersed phase and improving adhesion between PE and PP phases. Addition of 10 wt.‐% of EPR caused the formation of the interfacial layer surrounding dispersed PP particles with the occurrence of PE‐LD lamellae interpenetration into the layer. Tensile properties (elongation at yield, yield stress, elongation at break, Young's modulus) and notched impact strength were measured as a function of blend composition and chemical structure of EPR. It was found that the EPR with a higher content of ethylene monomer units was a more efficient compatibilizer, especially for the modification of PE‐LD/PP 80/20 blend. Notched impact strength and ductility were greatly improved due to the morphological changes and increased interfacial adhesion as a result of the EPR localization between the phases. No significant improvements of mechanical properties for recycled PE‐HD/PP 80/20 blend were observed by the addition of selected block copolymers.     

Influence of polymeric flame retardants based on phosphorus‐containing polyesters on morphology and material characteristics of poly(butylene terephthalate)

Flame retarded poly(butylene terephthalate) (PBT) is required for electronic applications and is mostly achieved by low molar mass additives so far. Three phosphorus‐containing polyesters are suggested as halogen‐free and polymeric flame retardants for PBT. Flame retardancy was achieved according to cone calorimeter experiments showing that the peak heat release rate and total heat evolved were reduced because of flame inhibition and condensed‐phase activity. The presented polymers containing derivatives of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide form immiscible blend systems with PBT. Shear‐rheology shows an increase in storage moduli at low frequencies. This is proposed as quantitative measure for the degree of phase interaction. The phase structure of the blends depends on the chemical structure of the phosphorus polyester and was quite different, depending also on the viscosity ratio between matrix and second phase. A lower viscosity ratio leads to two types of phases with spherical and additionally continuous droplets. Addition of the flame retardants showed no influence on the dielectric properties but on the mechanical behavior. The polymeric flame retardants significantly diminish the impact strength because of several reasons: (1) high brittleness of the phosphorus polyesters themselves, (2) thermodynamic immiscibility, and (3) weak phase adhesion. By adding a copolymer consisting of the two base polymers to the blend, an improvement of impact strength was obtained. The copolymer particularly acts as compatibilizer between the phases and therefore leads to a smaller phase size and to a stronger phase adhesion due to the formation of fibrils. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

In situ reinforcement of poly(butylene terephthalate) and butyl rubber by liquid crystalline polymer

Ternary in situ butyl rubber (IIR)/poly(butylene terephthalate) (PBT) and liquid crystalline polymer (LCP) blends were prepared by compression molding. The LCP used was a versatile Vectra A950, and the matrix material was IIR/PBT 50/50 by weight. Morphological, thermal, and mechanical properties of blends were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry, and thermogravimetric analysis (TGA). Microscopy study (SEM) showed that formation of fibers is increasing with the increasing amount of LCP A950. Microscopic examination of the fractured surface confirmed the presence of a polymer coating on LCP fibrils. This can be attributed to some interactions including both chemical and physical one. The increased compatibility in polymer blends, consisting of IIR/PBT, by the presence of LCP A950 may be explained by the adsorption phenomena of the polymer chains onto the LCP fibrils. SEM and AFM images provided the evidence of the interaction between IIR/PBT and the LCP. Dynamic mechanical analyses (DMA) and TGA measurements showed that the composites possessed a remarkably higher modulus and heat stability than the unfilled system. Storage modulus for the ternary blend containing 50 wt% of LCP exhibits about 94% increment compared with binary blend of IIR/PBT. From the above results, it is suggested that the LCP A950 can act as reinforcement agent in the blends. Moreover, the fine dispersion of LCP was observed with no extensional forces applied during mixing, indicating the importance of interfacial adhesion for the fibril formation. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

SBS and SEBS block copolymers as impact modifiers for polypropylene compounds

Blends of polypropylene (PP) and thermoplastic elastomers (TPE), namely SBS (styrene‐butadiene‐styrene) and SEBS (styrene‐ethylene/1‐butene‐styrene) block copolymers, were prepared to evaluate the effectiveness of the TPE type as an impact modifier for PP and influence of the concentration of elastomer on the polymer properties. Polypropylene homopolymer (PP‐H) and ethylene–propylene random copolymer (PP‐R) were evaluated as the PP matrix. Results showed that TPEs had a nucleating effect that caused the PP crystallization temperature to increase, with SBS being more effective than SEBS. Microstructure characterization tests showed that in most cases PP/SEBS blends showed the smallest rubber droplets regardless of the matrix used. It was seen that SEBS is a more effective toughening agent for PP than SBS. At 0°C the Izod impact strength of the PP‐H/SEBS 30% b/w blend was twofold higher than the SBS strength, with the PP‐R/SEBS 30% b/w blend showing no break. A similar behavior on tensile properties and flexural modulus were observed in both PP/TPE blends. Yield stress and tensile strength decreased and elongation at break increased by expanding the dispersed elastomeric phase in the PP matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 254–263, 2005