Interfacial interactions and the properties of filled polymers: I. Dynamic-mechanical responses

The dynamic mechanical responses of rutile-filled, chlorinated polyethylene (CPE) were studied as a function of temperature, of filler loading, and of filler surface condition. An objective was to establish the influence of matrix-filler interactions on mechanical properties. Necessary information on potential interactions between matrix and filler was obtained from inverse gas chromatographic data, in the form of an acid-base interaction parameter, Ω. The damping peak in filled CPE compounds was depressed by the pigment, as called for by theoretical models. The magnitude of the effect exceeded expectations, however, and clearly depended on the strength of interfacial interactions. These were consistent with the acid-base ranking of CPE and the various rutiles, as given by Ω. It has been postulated that in the presence of acid-base interactions, an immobilized layer of polymer in the vicinity of solid particles increases the effective particle dimension, thereby accounting for the observed variations in relative damping. Additional effects of matrix-filler interaction were noted in the variation of storage moduli with loading and temperature. Again, the effects tend to be more pronounced when significant specific interactions between matrix and solid are operative. These observations point to the inadequacy of existing models as interpretative bases for dynamic mechanical properties in systems with significant specifie interactions among their components.     

Surface interactions and some properties of filled polymers

Inverse chromatography was applied to evaluate interaction parameters for polyethylene (PE), polyvinyl chloride (PVC), and CaCO₃, these parameters being based on retention volumes of proton-donor, -acceptor, and neutral vapors. The acid/base characteristics of CaCO₃ were controllably altered by exposing the particulate to microwave plasmas sustained by acidic and basic vapors. It was shown that the ease-of-dispersion of fillers in the polymer matrixes related with the acid–base interaction balance in the polymer-filler pair, and varied widely with the surface treatment given to the filler. Mechanical properties at large deformation of the filled polymers and their durability also were shown to depend on surface interactions. Optimization of properties in PVC compounds was favored when strong acid-base interactions could take place with the plasma-modified filler. In the case of PE, properties were superior when unmodified filler was used; imparting strongly acidic or basic surface properties to the filler diminished its “compatibility” and usefulness with this nonpolar matrix.     

Hysteresis temperature dependence in filled rubbers. II. Mechanical mixing,filler microdispersion,and polymer–filler interactions

The effects of mechanical mixing and filler–filler (F–F) and polymer–filler (P–F) interactions on the normalized state of a filler microdispersion [d(x)] and the viscoelastic properties of silica‐filled rubbers were studied. The rubbers were prepared with or without the addition of n‐octyl‐triethoxysilane (OTES) to modify F–F interactions or coupling agents such as 3‐mercaptopropyl‐trimethoxysilane and 3‐mercaptopropyl‐triethoxysilane (MPTES) to increase P–F interactions. Increased mixing improved d(x) and enhanced the hysteresis temperature dependence (HTD) by giving a higher tan δ value near the compound glass‐transition temperature (T_g) but lowered tan δ at elevated temperatures for stocks containing a coupling agent. The changes in P–F and F–F interactions in rubbers with mixing and subsequent thermal treatment were shown to be responsible for the property differences observed among stocks containing different silanes. Attempts were made to quantify the efficiency for improving d(x) with various silanes. The increased P–F interactions in compounds containing MPTES showed better efficiency for improving d(x) and enhancing HTD in comparison with OTES. It was also demonstrated that the change in hysteresis near T_g was mainly governed by the degree of filler networking, whereas elevated‐temperature hysteresis was strongly influenced by the P–F interactions in compounds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Model filled polymers. XIV: Effect of modifications of filler composition on rheology

Steady shear vxiscosity, dynamic moduli and the appearance of fracture surfaces of model composites, consisting of monodisperse crosslinked polymeric spheres of varied composition in a polymethyl-methacrylate matrix, depend on the compatibility of filler particle and matrix. After intensive mixing, “compatible” systems form uniform and stable dispersions. Filler particles cluster in incompatible composites producing a highly non-Newtonian response. At 40 w% filler, yield behavior results, with a yield stress of 3100 Pa for polystyrene particles and 1900 Pa for copolystyrene-acetoxystyrene particles. The flow properties of compositionally complex particles from seeding are determined by particle surface composition.     

BIMS/filler interactions. II. Effects of filler concentration and BIMS structure

Brominated isobutylene para‐methylstyrene (BIMS) elastomer is a terpolymer of isobutylene, para‐methylstyrene (PMS), and para‐bromomethylstyrene (BrPMS). Viscoelastic measurements have been used to characterize the blends of this BIMS elastomer with different concentrations of a carbon black (CB) filler, N234. Data in the low temperature/high frequency region suggest that N234 at a concentration less than or equal to 15 vol % in BIMS appears not to affect the T_g of BIMS although a slight increase in relaxation time in the transition zone is observed. Also, the effects of BrPMS and PMS contents in BIMS on BIMS/N234 CB interactions have been qualitatively investigated by using the bound rubber measurements. To assess BIMS/CB interactions with reference to diene rubber/CB interactions, mixing of BIMS with various amounts of a polybutadiene rubber in the presence of CB has been performed. Atomic force microscopy and image processing have been employed to quantify filler phase distributions in these blends for a practical ranking of polymer/CB interactions. Preferential partition of CB in the BIMS or BR phase depends on the BrPMS content in BIMS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 659–667, 2006     

Effect of filler on the relaxation time spectra of filled polymers

The temperature and frequency dependences of the complex shear modulus G^* and tan δ of mechanical losses of epoxy compositions with various fillers were studied. The method of Ninomiya-Ferry applied to the reduced curves of frequency dependence of the effective part of the shear modulus was used to draw up relaxation time spectra for specimens with various concentrations of the filler. Regularities in the change of type and position of the spectral curves with increase in filler concentration were indicated. The findings make it possible to draw conclusions about the effect of the filler on the properties of the polymer matrix in the boundary layer and about changes in the conditions of the deformation of the polymer interlayers between the filler particles as compared with the deformations in bulk specimens.     

Mechanical properties of particulate filled polymers

The mechanical properties of several types of inorganic fillers were investigated in a number of different thermoplastic polymers. The fillers included minerals, such as talc and silicon carbide, and metals, such as aluminum flake and stainless steel fibers. The polymers included General Electric's Noryl, acrylonitrile-butadiene-styrene terpolymer, polypropylene, and modified polypropylene. The talc and some of the aluminum flake were treated with coupling agents to improve interfacial adhesion to the polymers. The results showed that the modulus of the filled polymers was a function only of the concentration of filler used up to 40 volume percent filler. The tensile strength of the filled compositions depended very strongly on the degree of interfacial bond developed between the polymer and the filler. The interfacial bond strength depended on the effectiveness of the coupling agents and the inherent wetting ability of the polymer. Of the polymers investigated in this study, Noryl showed the greatest degree of inherent wetting to inorganic fillers. Chemical modification of polypropylene also resulted in greater adhesion to fillers. The impact strength of filled compounds had an even more complex response, because, in addition to the concentration of the filler, and strength of the polymerfiller interface, it depends on the mechanism of crack propagation.     

Polymer-filler interactions in composites with grafted filler particles

PMMA grafts were grown from the surfaces of glass beads and the grafted beads were used to fill PMMA homopolymer using solvent casting procedures. Interactions between grafts and matrix chains were investigated by examination of scanning electron micrographs of fracture surfaces of composite materials. It was demonstrated that, while grafts on adjacent beads are mutually miscible, grafts are immiscible with homopolymer chains at equilibrium. Formation of entanglements between graft and homopolymer chains was achieved by forming homopolymer in situ and avoiding equilibrium conditions.     

Viscoelasticity of polymers filled by rigid or soft particles: Theory and experiment

An improved modeling for the viscoelasticity of polymers filled by rigid or soft inclusions is proposed. Such a self-consistent scheme can predict the strong increase in the reinforcement effect of the polymer matrix observed for large volume fractions of fillers. Then, it is based on both (i) the percolation concept and (ii) the definition of an original “representative morphological motif” accounting for local phase inversions due to the presence of clusters of particles. To illustrate the validity of such an approach, the predicted viscoelasticity of polystyrene filled either by glass beads or by rubbery inclusions is compared with experimental data and/or theoretical results that issue from other modelings.     

The effect of particles on failure modes of filled polymers

The effect of rigid particles on the fracture mode of polymers that yield with necking was analyzed theoretically with a model of regularly arrayed spherical particles. The adhesion between a polymer and particles was assumed to be weak, and particles were assumed to debond from the polymer before necking. A linear decrease in engineering draw stress with an increase in the filler content was derived. An increase in filler content leads to a transition in deformation mechanism. The transition depends on the ability of the polymer to strain-harden. If the ability to strain-harden is insignificant and the engineering fracture stress (strenght) of the polymer is lower than its yield stress, the transition is from ductile to brittle fracture. If the ability to strain-harden is essential and the strength of the unfilled polymer is higher than its yield stress, the transition (ductile-to-ductile) is from neck propagation to uniform ductile yield. The critical filler contents were determined for both transitions from the properties of an unfilled polymer. The ductile-to-ductile transition without embrittlement is possible if the strength of the unfilled polymer is higher than its yield stress. Results for polymers filled by weakly bonded particles were compared with polymers filled by particles that debond after the yield stress.     

Pinecone particles filled polybenzoxazine composites: Thermomechanical and mechanical properties

In the current study, 1 wt%, NaOH treated pine cone (ATPC) particles composites with bisphenol-A aniline based benzoxazine (BA-a) matrix were prepared by isothermal compression method. Ultimate impacts of ATPC reinforcement on the thermomechanical, tensile, flexural, and impact properties of the composites were studied by using a dynamic mechanical analyzer (DMA), a Universal testing machine, and a Tinius-Olsen impact device, respectively. The thermal stability of ATPC particles was remarkably increased, TGA confirmed that particles will not be degraded during the curing. The DMA results of 30 wt% ATPC reinforced composites confirmed that the glass transition temperature, storage modulus, and loss modulus were 22 ° C, 2510, and 250 MPa higher than the neat matrix, respectively. In addition, the impact strength of the 30 wt% ATPC reinforced composites was nearly 3 times higher than the neat matrix, which confirmed that the matrix's brittleness is reduced, similar observation was confirmed by the Brostow and coworkers empirical model. Moreover, a gradual rise in the tensile and flexural properties was also recorded. We can easily conclude from the studied parameters that the ATPC particles can be used as a sustainable agro-waste in polymeric composites.     

Simple theory of stress-strain properties of filled polymers

By the use of simple models of filled plastics, approximate equations are derived for the elongation to break in the case of perfect adhesion between the phases and for the tensile strength in the case of no adhesion between the polymer and filler phases. By combining these equations with equations for the modulus (assuming Hookean behavior) all the stress–strain properties can be derived, including rough estimates of the impact strength, as a function of filler concentration. Among other things, the theory predicts a very rapid decrease in elongation to break as filler concentration increases, especially for the case of good adhesion. It is also predicted for the case of good adhesion that the tensile strength of a filled polymer can be greater than that of an unfilled polymer.     

Model filled polymers. XV: The effects of chemical interactions and matrix molecular weight on rheology

In order to explore the effects of chemical composition on the rheological behavior o filled polymeric systems, we prepared polystyrene (9PS) and poly(methyl methacrylate) (PMMA) particles crosslinked with either ethylene glycol dimethacrylate (EGDMA) or divinyl benzene (DVB), and mixed these particles in a PMMA matrix. PS particles crosslinked with 10% EGDMA are better dispersed in a PMMA matrix, compared to PS particles, crosslinked with 10% DVB, due to the compatibilizing effect of EGDMA. For PMMA particles crosslinked with DVB, particle-matrix interactions in a PMMA matrix are smaller than in EGDMA-PMMA filled PMMA. Therefore, particles tend to agglomerate in PMMA composites filled with DVB-PMMA particles, especially in a low molecular weight matrix. We compared PMMA matrices of molecular weights 35,000 and 75,000. Higher particle-matrix interaction in the higher molecular weight matrix resulted in lower relative viscosities for DVB-PS filled systems, due to better dispersion of the particles. Composites filled with EGDMA-PS particles behave similarly to those filled with DVB-PS particles. PMMA composites filled with DVB-PMMA particles have a lower relative viscosity in the higher molecular weight PMMA matrix at low shear rates, due to better dispersion in the higher molecular weight matrix. However at high shear rates, particles are well dispersed in both PMMA matrices and, then, the relative viscosity is higher due to better bonding in the higher molecular weight matrix.     

Rheological analysis of highly loaded polymeric composites filled with non-agglomerating spherical filler particles

A non-agglomerating 15 μm diameter stainless steel spherical powder was used as a filler in a low-density polyethylene matrix. The factors investigated included volume loading, the use of surface treatments, and method of applying the surface treatments. The rheological parameters measured to analyze the effect of these factors on the melt behavior of the mixtures were the dynamic viscosity, η*, and the real component of the shear modulus, G′. These parameters showed clear differences in the response of the composites to volume loading, type of surface treatments, and method of surface treatment application.     

纳米聚合物填料的制备及其填充橡胶性能研究

采用乳液聚合法制备单分散交联聚苯乙烯(PS)和α-甲基苯乙烯-丙烯腈共聚物(α-Ms-AN)乳胶粒子,并研究其填充NBR和SBR胶料性能.结果表明,当引发刺KPS,乳化剂OP-10和SDS、交联剂DVB质量分别为单体质量的1%,3.3%,6.6%和20%时,可制备出平均粒径为43 nm、玻璃化温度(Tg)为125℃的PS纳米微球;当引发剂APS,乳化剂MS-1和交联剂DVB质量分别为单体质量的0.3%,2%～3%和15%时,可制备出平均粒径为47 nm,Tg为152℃的α-MS-AN纳米微球.两种填料在NBR和SBR胶料中的最佳用量均为30份;PS填充SBR胶料的物理性能优于其填充的NBR胶料;α-MS-AN填充的NBR胶料物理性能优于其填充的SBR胶料.     

氢氧化铝高填充聚乙烯材料的界面和力学性能

从Al(OH)3高填充线型低密度聚乙烯（LLDPE）材料的界面性质出发,研究了复合材料界面改性与硅烷交联方法对LLDPE/Al(OH)3复合材料的微观结构,加工流动性及力学性能的影响。钛酸酯和乙烯-醋酸乙烯共聚物能显著改善LLDPE/Al(OH)3复合材料的延伸性能,硅烷交联与界面改性对改善材料的力学性能具有协同作用。     

Model filled polymers. XIII: Mixing and time-dependent rheological behavior of polymer melts containing crosslinked polymeric particles

The rheological properties of polystyrene (PS) and poly(methyl methacrylate) (PMMA) composites filled with monodisperse sized crosslinked polymeric particles are sensitive to processing history and chemical composition. Particles compatible with the matrix, such as PMMA or copolystyrene-vinylphenol in a PMMA matrix, are randomly dispersed on mixing, yielding (almost) Newtonian fluids. Particles incompatible with the matrix, such as PS or copolystyrene-acetoxystyrene in PMMA, produce composites whose steady shear viscosities depend on shear rate and whose dynamic moduli are elevated at low frequency. Particles in incompatible composites tend to cluster, producing a structure that is destroyed at high shear rates and that reforms on aging at elevated temperatures.     

Interfacial physicochemical properties of functionalized conducting polypyrrole particles

Polypyrrole-coated polystyrene latex particles bearing reactive N-succinimidyl ester functional groups (PS-PPyNSE₇₅) were prepared by the in situ copolymerization of pyrrole 1 and the active N-succinimidyl ester-functionalized pyrrole 2 (pyrroleNSE), with initial 1:2 fractions of 25:75 (%) in the presence of sterically stabilized polystyrene (PS) latex particles. PS particles were prepared by dispersion polymerization leading to particles having a diameter of 600±10 nm. The PS-PPyNSE₇₅ particles were characterized in terms of surface morphology and chemical composition. Surface analysis of the colloidal materials by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) indicated a substantial coating of PS by the reactive conducting copolymer. Infrared spectroscopy permitted to detect pyrroleNSE repeat units at the surface of the particles indicating that 1 and 2 did indeed copolymerise.Reactivity of the PS-PPyNSE₇₅ particles has been investigated using 2-aminoethanol and 2-mercaptoethanol, two model molecules bearing functional groups borne by proteins. Incubation of the particles with these model molecules clearly showed that the particles are highly reactive towards amine and thiol groups. The functionalized particles were then tested as bioadsorbents. PS-PPyNSE₇₅ particles were found to be effective in attaching an aminated biotin. The Biotin-decorated PS-PPyNSE₇₅ latex particles were incubated with avidin with a result of a significant change in the surface composition that is in line with the attachment of the protein by specific binding to biotin.