Influence of fillers and bonding agents on the viscoelasticity of highly filled elastomers

Highly filled elastomers such as solid propellants exhibit a complex nonlinear viscoelastic behavior. This work aimed at determining the influence of binder–filler and filler–filler interactions on the microstructure and the viscoelastic properties of the propellant using a design of experiments method. The influences of the filler fraction and of the filler–binder bonding agents (FBBA) were measured by swelling experiments and prestrained dynamic mechanical analyses. The results showed that FBBA react on the filler surface and concentrate the curing agents in the vicinity of the fillers. The nonlinearity of the viscoelastic behavior originated from filler–filler interactions that created high stress zones between fillers and therefore constrained the movements of the macromolecules of the binder. Filler–binder interactions induced by the FBBA increased the filler effective volume as well as the heterogeneous stress distribution in the microstructure. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40664.     

Influence of chlorinated paraffin on properties of silica filled polychloroprene

Abstract

Roles of the two widely used chlorinated paraffins, namely Cereclor S45 and Cereclor 48, in properties of silica filled polychloroprene were investigated. The results reveal that chlorinated paraffin significantly improves the processability. The improvement is more pronounced for Cereclor S45 due to its lower viscosity. However, the addition of chlorinated paraffin has a negative effect on cure. Owing to the reduction of crosslink density and the plasticising effect of chlorinated paraffin, several mechanical properties are impaired, e.g. tensile strength, modulus, hardness, abrasion resistance as well as rebound resilience. However, the deterioration of both tensile strength and modulus is not pronounced at low loading of chlorinated paraffin (≤8·0 parts per hundred of rubber, phr). Although chlorinated paraffin has little influence on the relative tensile strength, the relative 100% modulus is affected to a greater extent due to the combination of post curing retardation and evaporation of chlorinated paraffin during thermal aging.     

Mechanical properties of recycled polyethylene ecocomposites filled with natural organic fillers

The use of natural organic fillers in addition to postconsumer recycled polymers is getting a growing interest during the last years; this is due to many advantages they can provide in terms of cost, aesthetic properties, environmental impact. In this work, several types of wood flour (differing each other with regard to production source and particle size) were added to a recycled polyethylene coming from films for greenhouses and the effects of filler type, content, and size were investigated. Investigation was then focused on the improvement of mechanical properties, through the addition of polar copolymers (ethylene‐co‐acrylic acid, ethylene‐vinyl acetate) and a maleic anhydride‐grafted‐grafted polyethylene (Licocene® PE MA 4351 TP), in order to try to overcome the poor adhesion between polar filler particles and nonpolar polymer chains. Investigation was also based on SEM micrographs. An overall positive influence of these additives was observed. Polym. Eng. Sci. 46:1131–1139, 2006. © 2006 Society of Plastics Engineers.     

The effects of degree of mixing on the properties of filled elastomers

A new technique has been established for improving the degree of mixing of the filler in an elastomer matrix. This technique includes a unique heating and colling mixing procedure in conjunction with surface modification of the carbon black and proper choices of polymers. The heating cycle is for decreasing the microvoid concentration and for enhancing polymer–filler adhesion. The cooling cycle is for improving the degree of mixing of the filler. Experimental data obtained from several polychloroprene systems strongly substantiate the new mixing technique. The results clearly show that a good degree of mixing obtained using the foregoing mixing technique can indeed enhance the mechanical and permeability properties of filled elastomers.     

Effect of water on the strength of filled polychloroprene vulcanizates

Three commercial rubber compounds used in marine applications were immersed in water or in 3.5% NaCl solution for up to 250 days. Tear strengths, measured with the “trousers” test piece, decreased in the order dry > salt water exposed > fresh water exposed, and changes of up to 50% were seen. Tensile strengths also decreased, but not always in the same proportion, suggesting a possible change in structure of the voids which initiate fracture. Results are discussed in terms of osmotic swelling and extraction of rubber components.     

The effect of surface properties on the adhesion of modified polychloroprene used as adhesive

The adhesion properties of polychloroprene can be improved by addition of such materials as piperylene–styrene co-polymer (PSC), VeoVa-10 polymer, VeoVa-11/methyl methacrylate/2ethylhexyl acrylate co-polymer (VeoVa-11/MMA/2EHA) and poly(vinyl acetate) waste (wPVAc). Here, the relationship between adhesion properties and surface tension of polychloroprene was investigated. Contact angle measurements have been used to study the effects of nature and content of polymeric additives on the adhesion and surface properties of polychloroprene. Low-surface-tension VeoVa-10 polymer has the tendency to migrate to the surface of polychloroprene; thus, adhesion is determined mainly by this additive property. Enrichment of polychloroprene film bottom layer by the additive was observed using high-surface-tension PSC and wPVAc. In this case, the adhesion properties of polychloroprene depend on the interactions at the interface. Adhesion properties of polychloroprene were found to depend not only on compatibility between adhesive components, but also on compatibility between the adherend and the adhesive.     

Effect of synthesis variables on viscoelastic properties of elastomers filled with carbonyl iron powder

This work studies the influence of synthesis variables on the lineal viscoelastic properties of elastomers filled with soft magnetic particles. Three matrices [natural rubber (NR), high-temperature vulcanising silicone rubber (HTV-SR), and room-temperature vulcanising (RTV-SR)] and three volumetric particle contents (0%, 15%, and 30%) were studied. Anisotropic samples were synthesised with a softer matrix to obtain a larger magnetorheological (MR) effect, and the variation of their properties under an external magnetic field was examined. All samples were characterised within the lineal viscoelastic (LVE) region using a rheometer, because the MR effect is larger within this region. The influence of the matrix, particle content, and pre-structure on the viscoelastic properties of the synthesised samples was studied. The storage and loss modulus increased with the frequency owing to the viscoelastic behaviour of an elastomer in the rubbery phase. Both moduli also increased with the filler content. The influence of the filler is dependent on the matrix, and the maximum variation was seen in the NR-based samples. However, the maximum MR effect was seen in the samples with a softer matrix, and the effect was enhanced in the anisotropic samples. In this work, the MR effect on the loss modulus was studied, and the tendencies were found to be similar to those of the storage modulus. The main contribution of this work is that all dynamic behaviour results were comparable because all synthesis variables and characterisation conditions were identical. Therefore, how the particle content, frequency, and magnetic field affects each matrix can be studied.     

Improvement of properties of silica‐filled natural rubber compounds using polychloroprene

Because silica has strong filler–filler interactions, a silica‐filled rubber compound is characterized by a poor dispersion of the filler. Properties of silica‐filled natural rubber (NR) compounds were improved using polychloroprene (chloroprene rubber [CR]). The bound rubber content of the compound increases and the filler dispersion is also improved by adding CR to the compound. Physical properties such as modulus, tensile strength, abrasion, and crack resistance are improved by adding CR. Elongation at break of the vulcanizates containing CR is longer than that of the vulcanizate without CR, although crosslink density of the former is higher than that of the latter. The improved physical properties are attributed to the good dispersion of silica by adding CR. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2609–2616, 2002     

Stabilization of filled polysiloxane elastomers to cyclic stress at elevated temperature through use of zinc oxide fillers

The susceptibility of filled polysiloxane elastomers to cyclic stress at elevated temperatures is investigated. It is shown that zinc oxide fillers, unlike other fillers examined previously, can produce filled elastomers with remarkable stability to combined mechanical and thermal stresses. The influences of filler concentration, diphenylsiloxane incorporation, and molecular weight between network crosslinks are examined. The data demonstrate that the elastomer stability to cyclic stress at elevated temperature increases with increasing filler content and does not correlate with diphenylsiloxane content. It is suggested that chemical interactions between the polysiloxane network and the filler surfaces control the response to cyclic stress at elevated temperature and that the response strongly depends on the type of filler selected. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1499–1509, 1997     

增强相对热塑性聚酰亚胺复合材料性能的影响

采用热模压成型的方法,在热塑性聚酰亚胺(TPI)中添加玻璃微珠(GB)、玻璃纤维粉(GFP)和短切玻璃纤维(SGF)进行复合增强,研究了3种不同形态填充材料及其含量对复合材料力学、摩擦磨损及热性能的影响。结果表明,随着填充物填充量的增加,所制得复合材料的刚性明显提高;并且填充物长径比越大,其作用效果越明显,由此制得的复合材料同时具有较低的体积磨损率及线膨胀系数。采用SGF增强复合材料的力学强度也随其填充量的增加显著增大,而采用GB及GFP填充的材料则呈下降趋势。采用SEM观察了复合材料断裂面的结构形貌,初步分析了其增强机理。     

Solar spectral properties of PVC plastisol‐based films filled with various fillers

Plastisol is mostly a suspension of PVC particles in a liquid plasticizer that flows as a liquid and can be poured into a heated mold. For PVC plastisol applications, in addition to liquid dispersion performance and post‐dispersion flocculation resistance, outdoor durability is an important end use requirement. Spectral properties of PVC plastisol‐based films with or without additional near infrared (NIR) rays barrier fillers have been investigated. Both spherical and lamellar fillers have been incorporated in PVC plastisol at a weight content of 2% to 10% and results show a high impact on the reflectance in the NIR region and on the transmittance in the visible (Vis) region. Experimental results showed that the incorporation of nacre lamellar‐based filler in PVC plastisol did not permit favorably change its spectral properties while TiO₂‐based particles ensured a decrease of the transmittance in the Vis and an increase of the reflectance in the NIR. J. VINYL ADDIT. TECHNOL., 25:E188–E194, 2019. © 2018 Society of Plastics Engineers     

Cavity formation on elongation in filled elastomers

Experiments were conducted on samples of crosslinked rubbers filled with poly(tetrafluoroethylene) powder or small glass beads. Volume changes on elongation were measured in a dilatometer. Slow deformation cycles showed considerable hysteresis, the volume on elongation being smaller than on contraction. There is much less hysteresis if the sample is degassed before the experiment. These observations suggest that, to a large extent, the volume of the cavities is determined by the availability of gases dissolved in the elastomer matrix. When the samples were saturated with carbon dioxide, nitrogen, and helium, it was indeed found that the degree of cavitation increased in order with the solubility of these gases. The initial rate of cavitation is high. After about 1 min, dilatation is proportional to the logarithm of time. This rate is inversely related to the solubility of the gas present. When a sample is subjected to a constant tensile stress under vacuum and the external pressure is suddenly brought to atmospheric, the elongation at first decreases due to compression of the cavities and then increases slowly as gas diffuses into them. Even unfilled compounds mixed mechanically contain submicroscopic holes. These enlarge on deformation thus causing dilatation. Only for samples prepared by evaporation from solution is there no pressure dependence of the apparent modulus. It is demonstrated that the relation between the volume of vacuum cavities and the external pressure resembles that of volume and inflation pressure of a spherical hole in an infinite elastic medium.     

Improvement of thermo-electrical properties of polymer composites filled with multiwall carbon nanotubes decorated carbon fillers

To enhance the thermo-electrical properties of liquid silicone rubber (LSR) in applications, the carbon fibres (CFs) modified by multiwall carbon nanotubes (MWCNT) on the surfaces were used as the fillers. The MWCNT-modified CFs (MPCFs) were analysed by Fourier transform infrared spectra, thermogravimetric analysis, scanning electron micrograph and energy dispersive X-ray spectroscopy. It was found that MWCNT were successfully adsorbed onto the surface of CFs. The MPCFs functioned as conductive fillers in LSR for thermal and electrical conductivity application and exhibited significant enhancement. The effects of MPCFs loading on thermal conductivity and volume resistivity of LSR composites were investigated in detail. Results of this work revealed that the MPCFs/LSR composites possessed a thermal conductivity of 0.73?W?m^?1?K^?1 with 14?vol.-% filler loading, approximately 3.48-fold higher than that of pure LSR substrate. And with the increase of MPCFs loading, the least volume resistivity of MPCFs/LSR composites is 10?Ω?cm. Besides, compared with that of neat LSR, the tensile strength of MPCFs/LSR composites increased 0.913?MPa.     

Effect of polymer-filler interactions on PTC behaviors of LDPE/EPDM blends filled with carbon blacks

The dependence of electrical resistivities on the temperature of different polymer systems (including rubbers and plastic/rubber blends) loaded with carbon blacks (including oxidized and normal carbon blacks) were studied. We found that polymer-carbon black interactions could greatly influence the electrical resistivity and temperature relations of the polymer composites. The polymer blends filled with oxidized carbon black, or the elastomer which has polar functional groups filled with carbon black, have a very weak negative temperature coefficient (NTC) effect, which is due to the strong polymer-filler interactions. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1885–1890, 1997     

Linear viscoelasticity of polymer melts filled with nano-sized fillers

The linear dynamic rheology of polymer melts filled with nano-sized fillers is investigated in relation to a proposed two phase model. A common principle is disclosed for nanofilled polymers exhibiting either fluid- or solid-like behaviors with increasing filler volume fraction. The bulky polymer phase far away from the filler inclusions in the nanocomposites behaves the same as in the unfilled case while its contribution to the composite modulus is enlarged due to strain amplification effect. The filler forms aggregates together with polymer chains absorbed on the filler surface, which is termed as the “filler phase” in the proposed model. The dynamics of the “filler phase” slow down with increasing filler concentration. The applicability of the proposed two phase model is discussed in relation to the well-known structural inhomogeneity of nanofilled polymers as well as the strain amplification and the filler clustering effects.     

填料对沥青胶浆/集料黏附性能的影响

为研究填料对沥青混合料黏附特性的影响,以沥青胶浆为研究对象,采用改进水煮法、光电比色法和表面能法研究了水泥、粉煤灰以及水泥混凝土再生粉等体积取代矿粉(0,20%,60%,100%)对沥青胶浆/集料黏附性能的影响,并通过沥青混合料冻融劈裂试验进一步验证了其性能影响。结果表明,水泥取代矿粉能提高沥青胶浆黏附等级,降低剥落率,提高黏附功且其增幅随着取代率的增加而降低;粉煤灰同样能改善沥青胶浆黏附性,其改善效果略优于水泥;水泥混凝土再生粉取代矿粉会明显降低黏附功,对沥青胶浆黏附性不利;沥青混合料冻融劈裂实验与沥青胶浆黏附性实验具有较强一致性,引入水泥与粉煤灰可提高混合料冻融劈裂强度比,而再生粉会降低该值。     

填料对丁腈橡胶热降解性能的影响

采用热重-差式扫描量热分析（TGA-DSC）技术和热重-红外（TGA-FTIR）联用技术,研究了炭黑对丁腈橡胶（NBR）热降解性能及热降解过程和产物的影响。研究结果表明,炭黑对NBR具有热稳定作用,降解温度提高9℃,TiO2不影响NBR的降解温度。炭黑对NBR降解过程分子结构的变化没有产生本质的改变,但因减弱了分子链问的作用力,不利于-C≡N键的分子间交联,促进了其环化反应。     

Influence of interfacial adhesion on stress-strain properties of highly filled polyethylene

This paper studied the structure and properties of highly filled polyethylene/magnesium hydroxide composite. A third additive component was introduced to alter interfacial adhesion. Scanning electronic microscopy proved that the filler particles were totally surrounded by additive material. Interfacial adhesion played an essential role in determining the fracture mechanism and, consequently, the mechanical properties of the composites. The composites with good interfacial adhesion had high tensile strength and relatively low elongation at break. Conversely, a poor interfacial adhesion led to a composite with low tensile strength and high elongation.     

无机填料对淀粉胶性能的影响

以斯坦霍尔2步法制备的玉米淀粉胶为研究对象,试验了3种无机填料对淀粉胶稳定性、黏度以及制备的瓦楞纸板在普通环境和潮湿环境中的边压强度和粘合强度的影响。结果表明,加入无机填料可以大幅度提高淀粉胶稳定性;以加入适当无机填料A的淀粉胶制作的瓦楞纸板的边压强度有较大提高。     

稀土掺杂炭黑填充型非硫调节型粉末氯丁橡胶的性能与结构

利用镧系稀土（Ln）对炭黑表面有特殊的活化作用,采用化学沉积法制备了稀土掺杂炭黑（HAF—Ln）,并将HAF—Ln与非硫调节型氯丁胶乳（CR232胶乳）进行共混,采用凝聚共沉法制备了稀土掺杂炭黑填充型非硫调节型粉末氟丁橡胶[P（CR232／HAF—Ln）]。研究了稀土类型及用量对P（CR232／HAF—Ln）硫化胶力学性能的影响,发现采用稀土La、Sm和Tm掺杂的P（CR232／HAF—Ln）具有较好的力学性能。通过P（CR232／HAF—Ln）硫化胶拉伸断面的SEM分析,发现稀土La、Sm和Tm可有效改善炭黑在橡胶基体中的分散。