聚丙烯酸酯乳液在水泥砂浆中的应用

为了提高水泥砂浆的韧性,选用了能形成柔性薄膜结构的聚合物--聚丙烯酸酯乳液对水泥砂浆进行改性.研究了聚丙烯酸酯乳液对水泥砂浆体积密度、抗压强度、抗折强度、韧性、动弹模量和黏结抗拉强度的影响.结果表明:聚丙烯酸酯乳液在一定程度上降低了水泥砂浆体积密度和抗压强度,对抗折强度影响较小,改善了水泥砂浆的韧性,并且可提高黏结抗拉强度.当乳液掺量(质量分数)大于5%时,28 d混合养护聚丙烯酸酯乳液水泥砂浆的压折比降低到3以下,只有当乳液掺量大于10%时,水泥砂浆的黏结抗拉强度才明显提高.     

Improvement in impact property of continuous glass mat reinforced polypropylene composites

The toughened polypropylene (PP) was obtained by the blending of PP with ethylene‐propylene diene monomer (EPDM). The impact property of continuous glass mat‐reinforced polypropylene was adjusted through three ways: different toughness PPs and their blends were used as matrices, the functionalized polypropylene was added into the matrix to control the interfacial adhesion; the ductile interlayer was introduced at the fiber/matrix interphase by the grafting and crosslinking of rubber chains on fiber surface. The effect of PP toughness, interfacial adhesion, and ductile interlayer on the mechanical properties of composite systems was studied. The impact toughness of GMT increased with increasing the matrix toughness, whereas the flexural strength and modulus decreased. The good interfacial adhesion resulted in the low impact toughness. However, GMT composite with high strength, modulus, and impact toughness could be obtained by the introduction of a ductile interlayer at fiber/matrix interphase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2680–2688, 2002     

Effect of polymer cement modifiers on mechanical and physical properties of polymer-modified mortar using recycled artificial marble waste fine aggregate

Various polymer-modified mortars using recycled artificial marble waste fine aggregate (AMWFA) were prepared and investigated for the purpose of feasibility of recycling. Styrene–butadiene rubber (SBR) latex and polyacrylic ester (PAE) emulsion were employed as polymer modifier, and compared each other. The replacement ratio of AMWFA was also changed to investigate the effect of it on physical properties. Adding polymer cement modifier into mortar reduced water–cement ratio, and PAE was the more effective polymer cement modifier to reduce water–cement ratio than SBR. PAE emulsion-modified mortar increased the air content entrained as the proportion of PAE was increased. There was little difference in water absorption between SBR latex and PAE emulsion. The compressive strength decreased in the presence of polymer cement modifiers compared to that of no polymer cement modifiers, but the compressive strength of 20% of polymer–cement ratio was higher than that of 10%. After the hot water resistance test, both compressive strength and flexural strength were decreased.     

Physicomechanical properties of irradiated SBR latex polymer‐modified cement mortar composites

This study investigated the effect of styrene–butadiene‐rubber (SBR) latex/cement ratio as well as γ‐irradiation dose on physicomechanical properties of cement mortar. Specimens were prepared with a different SBR/cement mass ratio of 2.5, 5, 10, 15, and 20. Two curing methods were used: wet cure and dry cure. The best specimens were irradiated to doses of 10, 30, and 50 kGy. The compressive strength, total porosity, and bulk density were studied. The result indicated that the compressive strength, total porosity, and the bulk densities of the composites decrease with increase in the polymer cement ratios. In addition, it was observed that the compressive strength of irradiated polymer‐modified cement mortar composites was improved with the increase in the γ‐irradiation dose, and the compressive strength of mix‐cured samples was higher than those wet‐cured samples at any irradiation dose. X‐ray diffraction, thermogravimetric analysis, acid attack, and microstructure of SBR‐modified cement mortar were characterized. J. VINYL ADDIT. TECHNOL., 26:144–154, 2020. © 2019 Society of Plastics Engineers     

硅烷偶联剂对复合水泥砂浆性能的影响

通过红外光谱分析及砂浆强度测试，研究了硅烷偶联剂对不同种类复合水泥砂浆的稠度、分层度、抗折强度及抗压强度的影响。结果表明，加入硅烷偶联剂能提高普通水泥砂浆、苯丙胶乳改性水泥砂浆的抗折强度和抗压强度；当硅烷偶联剂质量分数为0．5％时，普通水泥砂浆的抗折强度和抗压强度达到极大值，提高约10％；当硅烷偶联剂质量分数为1％时，苯丙胶乳改性水泥砂浆的抗折强度和抗压强度达到极大值，提高约20％；同时，硅烷偶联剂还能增大普通水泥砂浆和苯丙胶乳改性水泥砂浆的稠度，但砂浆的分层度略有增大。加入经硅烷偶联剂处理的钢纤维，能够提高普通水泥砂浆及苯丙胶乳改性水泥砂浆的抗折强度和抗压强度；当钢纤维用硅烷偶联剂质量分数为1％的硅烷偶联剂水溶液处理时，钢纤维增强砂浆的抗折、抗压强度达到极大值，提高10％以上。     

Deformation mechanisms and mechanical properties of modified polypropylene/wood fiber composites

Mechanical properties and deformation mechanisms of polypropylene (PP)/wood fiber (WFb) composites modified with maleated polypropylene as compatibilizer and styrene-butadiene rubber (SBR) as impact modifier have been studied. The addition of maleated polypropylene to the unmodified polypropylene/wood fiber composite enhances the tensile modulus and yield stress as well as the Charpy impact strength. SBR does not cause a drop in the tensile modulus and yield strength because of the interplay between decreasing stiffness and strength by rubber modification and increasing stiffness and strength by good interfacial adhesion between the matrix and fibers. The addition of both maleated polypropylene and rubber to the polypropylene/wood fiber composite does not result in an improvement of effects based on maleated polypropylene and rubber, which includes possible synergism. The deformation mechanisms in unmodified polypropylene/wood fiber composite are matrix brittle fracture, fiber debonding and pullout. A polymeric layer around the fibers created from maleated polypropylene may undergo debonding, initiating local plasticity. Rubber particle cavitation, fiber pullout and debonding were the basic failure mechanisms of rubber-toughened polypropylene/wood fiber composite. When maleated polypropylene was added to this composite, fiber breakage and matrix plastic deformation took place. Polym. Compos. 25:521–526, 2004. © 2004 Society of Plastics Engineers.     

Effect of dynamic crosslinking on impact strength and other mechanical properties of polypropylene/ethylene‐propylene‐diene rubber blends

The deformation and fracture behavior of several dynamic vulcanizate blends of isotactic polypropylene with ethylene‐propylene‐diene rubber (EPDM) was examined and compared with those of uncrosslinked blends of PP/EPDM. These blends were prepared by melt mixing in an internal mixer at 190°C in a composition range of 10–40 wt % EPDM rubber. The variation in yield stress, the strength of fibrils of the craze, and the number density of the EPDM rubber domains (morphology fixation) that are dominant factors for enhancing interfacial adhesion and toughness in dynamic vulcanizate blends were evaluated. The ductility and toughness of these materials were explained in light of the composition between crack formation and the degree of plastic deformation through crazing and shear yielding. The physicomechanical properties including the hardness, yield stress, Young's modulus, percentage elongation, impact strength, flexural strength, and flexural modulus of dynamic vulcanized blends were found to be consistent and displayed higher values compared with uncrosslinked blends. The nucleation effect of the crosslinked particles and the decrease of crystallinity of the EPDM rubber were also considered to contribute to the improvement in the impact strength. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2089–2103, 2000     

Impact modification of polypropylene‐based composites using surface‐coated waste rubber crumbs

Blends of maleated polypropylene (MAPP) with high contents of waste rubber powder, namely ground tire rubber and waste ethylene propylene diene monomer (EPDM) powder, were used as impact modifiers for polypropylene (PP) based composites with different reinforcements (hemp, talc, and milled glass fiber). Adding reinforcements led to increase in modulus (tensile, flexural, and torsion moduli) of PP, while its impact strength decreased noticeably. Impact modification of PP‐based composites was successfully performed via inclusion of MAPP/waste rubber compounds, especially compounds containing waste EPDM powder. Inclusion of such impact modifiers increased impact strength of composites over 80%. The effects of impact modification were more significant for hemp‐ and glass‐filled composites compared to composites containing talc. However, slight decrease in tensile, flexural, and torsion moduli (up to 30%) of the composites was also observed after inclusion of impact modifiers. POLYM. COMPOS., 35:2280–2289, 2014. © 2014 Society of Plastics Engineers     

Mechanical properties of wood-fiber/toughened isotactic polypropylene composites

This study investigates the mechanical properties of wood-fiber/toughened PP composite modified by physical blending with an EPDM rubber to improve impact toughness. Wood-fiber thermoplastic composites were prepared with a modified PP matrix resin, employing high shear thermokinetic compounding aided with maleated PP for the fiber dispersion. The addition of EPDM improved the impact toughness, while it reduced stiffness and strength properties. To compensate the non-plane strain fracture toughness, the specimen strength ratio (R_sb) was adopted as a comparative measure of fracture toughness. The strength ratio increased with the addition of EPDM, while it decreased with increasing wood-fiber concentration. The work of fracture increased with EPDM level except at large wood-fiber concentration. The effectiveness of the impact modification was assessed with the balance between tensile modulus and unnotched impact energy as a function of wood-fiber concentration. EPDM rubber modification was moderately effective for wood-fiber PP composites. The examination of fracture surfaces showed twisted fibers, fiber breakage, and fiber pull-out from the matrix resin.     

Fracture toughness of particle filled fiber reinforced polyester composites

Fracture behavior of polyester composite systems, polyester mortar and glass fiber reinforced polyester mortar, was investigated in mode I fracture using single edge notched beams with varying notch depth. The beams were loaded in four-point bending. Influence of polymer content on the flexural and fracture behavior of polyester composites at room temperature was studied using a uniform Ottawa 20–30 sand. The polymer content was varied between 10 and 18% of the total weight of the composite. The flexural strength of the polyester mortar systems increase with increase in polymer content while the flexural modulus goes through a maximum. The critical stress intensity factor (K_IC) for the optimum polyester mortar (14%) was determined by two methods including a method based on crack mouth opening displacement. The K_IC for polyester mortar is linearly related to the flexural strength. Polyester mortar (18%) reinforced with 4% glass fibers was also investigated, and crack growth resistance curve (K_R) was developed with crack extension (Δa). A model has been proposed to represent the fracture toughness with change in crack length, K_R - Δa relationship, of fiber reinforced polyester composite.     

The comparison of properties of (rubber tree seed shell flour)‐filled polypropylene and high‐density polyethylene composites

The effect of varied rubber tree seed shell flour (RSSF) filler loadings on processing torque, mechanical, thermal, water absorption, and morphological properties of polypropylene (PP) and high‐density polyethylene (HDPE) composites has been studied. The addition of RSSF in the composites increased the stabilization torque in both PP‐ and HDPE‐based composites. Tensile strength, elongation at break, flexural strength, and impact strength show significant reduction when higher loading of RSSF was incorporated, while tensile modulus and flexural modulus were improved. The phenomenon was noted for both matrices, PP and HDPE, but HDPE‐based composites showed clear effects on the reduction of the mechanical properties compared with RSSF‐filled PP. Scanning electron microscopy of tensile fracture specimens revealed the degree of dispersion of RSSF filler in the matrices. At higher filler loadings, agglomerations and poor dispersion of RSSF particles were spotted, which induce the debonding mechanism of the system. Thermogravimetric analysis thermograms showed that both PP‐ and HDPE‐based composite systems with higher RSSF content have higher thermal stability, initial degradation temperature, degradation temperature, and total weight loss. Water absorption ability of the composites increases as the filler loading increases for both matrices. J. VINYL ADDIT. TECHNOL., 22:91–99, 2016. © 2014 Society of Plastics Engineers     

Processability and mechanical properties of ternary composites PP/EPDM/GF

The enhancement of the mechanical properties of neat PP is achieved by the addition of glass fibers and EPDM rubber. The Young's modulus and notched Charpy impact strength of the composites obtained are improved with respect to the original polymer, leading to a new composite material with a very good balance of toughness and rigidity properties. The tensile behavior of these multiphase systems is successfully compared with theoretical predictions using the Halpin‐Tsai/Nielsen theory for uniaxially short fiber composites, which considers the matrix as a blend with spherical particles and can predict the tensile modulus considering an average fiber orientation angle. An accurate morphological study performed by scanning electron microscopy (SEM) shows a very good dispersion of the rubbery phase into the neat matrix. No special affinity between the rubber and the fibers is reported. The good dispersion and the small particle diameter indicate the good processability of the ternary systems studied.     

Critical stress intensity factor of epoxy mortar

Fracture behavior of epoxy mortar was investigated in Mode I fracture using single edge notched beams with varying notch depth and beam thickness. The beams were loaded in both 3-point and 4-point bending. Influence of polymer content and temperature on the fracture behavior of epoxy mortar was studied using uniform Ottawa 20–30 sand. The polymer content was varied between 10 percent and 18 percent of the total weight of the composite. The temperature was varied between 22°C and 120°C. The flexural strength of the polymer mortar increases with increase in polymer content while the flexural modulus goes through a maximum. The critical stress intensity factor (K_IC) was determined by several methods including compliance method (based on crack mouth opening displacement) and finite element analysis. The K_IC for epoxy mortar increases with increase in polymer content and epoxy mortar strength but decreases with increase in temperature. The critical stress intensity factor of epoxy mortar is represented in terms of polymer content and polymer strength or stiffness. Numerical tests based on random sampling and stratified sampling procedures were performed to substantiate the experimentally observed fracture toughness values of epoxy mortar.     

Physicochemical characterization of the filler–matrix interface in elastomer‐encapsulated fly ash/polyester particulate composites

An attempt was made to improve the toughness of fly ash (FA)/general‐purpose unsaturated polyester resin (GPR) composites. Elastomer [styrene–butadiene rubber (SBR) or acrylic copolymer (AC)]‐encapsulated fillers (FA or CaCO₃) were made through the coagulation of the emulsified elastomer containing the filler with constant stirring. The elastomer‐encapsulated fillers were added to GPR at concentrations as high as 15 wt % to make FA/SBR or AC/GPR composites. The mechanical properties (i.e., the tensile strength, tensile modulus, tensile elongation, flexural strength, flexural modulus, impact strength, and hardness) of FA/GPR, FA/SBR/GPR, and FA/AC/GPR composites were studied. The tensile‐fractured surfaces of all the composites were studied with scanning electron microscopy. The thermal stability was studied with thermogravimetric analysis. An analysis of the results indicate that this modification technique is rather easy and more economical than the chemical modification of filler surfaces with functional silane coupling agents. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 171–184, 2005     

Mechanical,thermal and dynamic‐mechanical behavior of banana fiber reinforced polypropylene nanocomposites

Natural fiber‐reinforced nanocomposites based on polypropylene/nanoclay/banana fibers were fabricated by melt mixing in a twin‐screw extruder followed by compression molding in this current study. Maleic anhydride polypropylene copolymer (MA‐g‐PP) was used as a compatibilizer to increase the compatibility between the PP matrix, clay, and banana fiber to enhance exfoliation of organoclay and dispersion of fibers into the polymer matrix. Variation in mechanical, thermal, and physico‐mechanical properties with the addition of banana fiber into the PP nanocomposites was investigated. It was observed that 3 wt% of nanoclay and 5 wt% of MA‐g‐PP within PP matrix resulted in an increase in tensile and flexural strength by 41.3% and 45.6% as compared with virgin PP. Further, incorporation of 30 wt% banana fiber in PP nanocomposites system increases the tensile and flexural strength to the tune of 27.1% and 15.8%, respectively. The morphology of fiber reinforced PP nanocomposites has been examined by using scanning electron microscopy and transmission electron microscopy. Significant enhancement in the thermal stability of nanocomposites was also observed due to the presence of nanoclay under thermogravimetric analysis. Dynamic mechanical analysis tests revealed an increase in storage modulus (E′) and damping factor (tan δ), conforming the strong interaction between nanoclay/banana fiberand MA‐g‐PP in the fiber‐reinforced nanocomposites systems. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Rubber‐toughened polypropylene nanocomposite: Effect of polyethylene octene copolymer on mechanical properties and phase morphology

Rubber‐toughened polypropylene (PP)/org‐Montmorillonite (org‐MMT) nanocomposite with polyethylene octene (POE) copolymer were compounded in a twin‐screw extruder at 230°C and injection‐molded. The POE used had 25 wt % 1‐octene content and the weight fraction of POE in the blend was varied in the range of 0–20 wt %. X‐ray diffraction analysis (XRD) revealed that an intercalation org‐MMT silicate layer structure was formed in rubber‐toughened polypropylene nanocomposites (RTPPNC). Izod impact measurements indicated that the addition of POE led to a significant improvement in the impact strength of the RTPPNC, from 6.2 kJ/m² in untoughened PP nanocomposites to 17.8 kJ/m² in RTPPNC containing 20 wt % POE. This shows that the POE elastomer was very effective in converting brittle PP nanocomposites into tough nanocomposites. However, the Young's modulus, tensile strength, flexural modulus, and flexural strength of the blends decreased with respect to the PP nanocomposites, as the weight fraction of POE was increased to 20 wt %. Scanning electron microscopy (SEM) was used for the investigation of the phase morphology and rubber particles size. SEM study revealed a two‐phase morphology where POE, as droplets was dispersed finely and uniformly in the PP matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3441–3450, 2006     

Influence of steel and PP fibers on mechanical and microstructural properties of fly ash-GGBFS based geopolymer composites

In this study, experimental investigations were carried out to estimate the mechanical and microstructural properties of polypropylene (PP) and steel fiber reinforced geopolymer mortar. Two industrial by-products are used as binders to produce the geopolymer composites, i.e., fly ash (FA) and ground granulated blast furnace slag (GGBFS). Different percentages of PP and steel fibers are used in geopolymer mortars to find the mechanical properties such as compressive, splitting tensile and flexural strengths were investigated to understand the strength behavior. However, the compressive elastic modulus values were estimated through the proposed equation based on the compressive strength of the fiber reinforced geopolymer composite samples. Moreover, to understand the geopolymeic reaction, microstructural studies, i.e., scanning electron microscopy (SEM), were conducted. The experimental results revealed that the addition of PP fibers up to 2.0% (volume fraction) enhanced the flexural properties of geopolymer mortar samples. The compressive strength of the steel fiber-reinforced geopolymer composite reached a maximum of 2.5% volume fraction, being a 13.26% improvement over the control mix. The flexural toughness index of the PP and steel fiber reinforced composites improved with increasing the fraction. However, steel fiber reinforced geopolymer samples are shown better flexural toughness compared to PP fibers. The SEM analysis of the geopolymer control mix achieved a good degree of geopolymerization and both the fibers yielded a considerable interfacial bonding with the geopolymer paste.     

Properties of latex blends and its modified cement mortars

In this paper, the mechanical properties of three latex blends and the mechanical properties and chloride diffusivity of the latex-modified mortars are studied. The relationships between the properties of polymer films formed from latex blends and the properties of the latex blend-modified mortars are illustrated. The test results showed that the modified mortar with the blend of styrene-acrylic ester (SAE) and styrene-butadiene rubber (SBR) showed synergistic effect; especially the flexural strength of the SAE/SBR blend-modified mortars was about 20-40% higher than that of monolatex-modified mortars. However, the vinyl chloride-vinylidene chloride copolymer (PVDC)/SBR and PVDC/SAE blends-modified mortars showed antisynergistic effect. The compressive strength of the modified mortars increased with the increasing of the tensile strength of the latex films, while the flexural strength of the modified mortars did not depend on the tensile strength of the latex films. When PVDC with the mass fraction of 0.2 or SAE copolymer emulsion with mass fraction of 0.4 was blended into SBR latex, the latex blend-modified mortars showed lower chloride diffusivity. The chloride diffusivity of the modified mortars increased approximately linear with the tensile strength of the latex blend films, and decreased with increase of the elongation at rupture of the latex blend films. When the elongation at rupture of the latex blend films increased from 200-300% to more than 800%, the chloride diffusivity of the modified mortars decreased from 10-15×10⁻¹² to 3-4×10⁻¹² m²/s.     

High performance PP/SEBS/CNF composites: Evaluation of mechanical,thermal degradation,and crystallization properties

Nanocomposites comprising carbon nanofibers (CNF) were prepared and evaluated in terms of morphology, mechanical performance, thermal stability and crystallization properties. It was found that addition of CNF reinforced polypropylene (PP) matrix by marginally increasing the strength and modulus, but at the expense of toughness and ductility. To improve the toughness of the composites, polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene (SEBS) was used. Presence of SEBS remarkably improved the toughness and ductility of the composites. The optimum level of reinforcement was observed at 0.1 wt% of CNF in the composites. Phase morphology studies revealed that at this concentration, CNF were well dispersed in polymer phases and beyond it, agglomeration occurred. PP/SEBS/CNF (0.1 wt%) nanocomposites exhibited good strength, excellent toughness and decent modulus, which make them suitable for cost effective, light‐weight, tough and stiff material for engineering applications. It was observed that thermal stability of composites is only marginally improved whereas crystallinity of PP drastically reduced by the addition of CNF. POLYM. COMPOS., 38:2440–2449, 2017. © 2015 Society of Plastics Engineers     

Applying vermiculite‐modified polypropylene film to flexible packaging material

This article presents a process for preparing organovermiculite by ball‐milling expanded vermiculite (EVMT) in water‐based ethylene vinyl acetate (EVA) latex. In this process, the vermiculite (VMT) is exfoliated to prepare a kind of EVMT/EVA modifying agent, in which EVA serves as both intercalating polymer into VMT and compatibilizer between VMT and polypropylene (PP). During melt blending between EVMT/EVA and PP, shear force exfoliates VMT sheets, dispersing them relatively well in the PP matrix. Compared with raw PP, EVMT‐modified cast polypropylene (CPP) are better when EVMT loading ranged from 0.5 to 1.0%, with improvement in both the strength and toughness of the EVMT/EVA‐modified CPP film. Specifically, tensile strength was increased by 44–54%, yield stress increased by 26%, stress at break increased by 37–43%, energy at break (toughness) increased by 29–34%, oxygen transmission rate decreased by 6.2–12.9%, the water vapor transmission rate was not significantly affected, the peel bond strength of laminated CPP film increased by 18–27%, and the processability and melt flow index (MFI) of EVMT/EVA/PP composites were improved as well. Increasing MFI attributes facilitated the processing and formation of EVMT/EVA/PP. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40954.