Effects of UV irradiation on physico‐mechanical properties of EPDM/buckminsterfullerene composite

Ethylene propylene diene rubber‐fullerene (EPDM/C60) composite, partially crosslinked by ultraviolet (UV) radiation, was prepared and characterized for crosslink density, mechanical properties and thermal behavior. FT‐IR analysis showed peak disappearance at 1688 cm^?1, corresponding to the unsaturation of EPDM, and the appearance of new peaks relating to the formation of oxidation products of C60, such as epoxide, keto, aldehyde and carboxylic groups. Solubility studies demonstrated the dissolution of pristine EPDM in toluene even after a longer period of UV exposure, whereas EPDM/C60 composite became insoluble and/or swollen after 6 hr of UV exposure, indicating the formation of partial crosslinking between EPDM and C60. Differential scanning calorimetry (DSC) measurements revealed an increase in the glass transition temperature peak of UV‐cured EPDM. Thermogravimetric analysis (TGA) showed that UV exposure reduced the thermal decomposition temperature of EPDM/C60, pristine EPDM and dicumyl peroxide (DCP)‐cured EPDM. The modulus, tensile stress and elongation at break of EPDM/C60 composites were greatly influenced by the duration of UV irradiation. Comparison of UV‐cured EPDM/C60 composite with DCP‐cured EPDM confirmed the superior strength properties of the former system. Copyright © 2004 John Wiley & Sons, Ltd.     

New double negative and positive temperature coefficients of conductive EPDM rubber TiC ceramic composites

In this paper, we have successfully prepared ethylene-propylene-diene monomer (EPDM)/TiC composites as thermistors, with new double negative and positive temperature coefficients of conductivity (NTCC/PTCC). EPDM composites loaded with 50 phr HAF carbon black and different concentrations of TiC were prepared. This study focuses on the effect of TiC content on the vulcanization process, the network structure and the electrical and thermal properties of EPDM/TiC composites. The effect of TiC on the network structure was evaluated e.g. the curing process, the characteristic time constant during vulcanization, the volume fraction of rubber, gel fraction, interparticle distance between conductive particles, the extent of TiC reinforcement in the rubber matrix and molecular weight between cross-linking through experimental and affine-phantom models. The effects of TiC content on the percolation theory, electrical conductivity, conducting mechanism of conductivity, conducting hysteresis and I-V characteristics were also studied, as well as its TiC on the (NTCC/PTCC), thermoelectric power, dielectric constant and thermal conductivity. Stability and reproducibility of the thermal cycles for heating element applications was tested. Specific heat and the amount of heat transfer by radiation and convection as a function of TiC content was calculated using both the calorimetric technique and a theoretical model. It was proved that TiC improves the network structure, electrical and thermal properties of EPDM composites for practical applications.     

In situ growth of TiO2 in interlayers of expanded graphite for the fabrication of TiO2-graphene with enhanced photocatalytic activity

We present a facile route for the preparation of TiO₂–graphene composites by in situ growth of TiO₂ in the interlayer of inexpensive expanded graphite (EG) under solvothermal conditions. A vacuum‐assisted technique combined with the use of a surfactant (cetyltrimethylammonium bromide) plays a key role in the fabrication of such composites. Firstly, the vacuum environment promotes full infusion of the initial solution containing Ti(OBu)₄ and the surfactant into the interlayers of EG. Subsequently, numerous TiO₂ nanoparticles uniformly grow in situ in the interlayers with the help of the surfactant, which facilitates the exfoliation of EG under the solvothermal conditions in ethanol, eventually forming TiO₂–graphene composites. The as‐prepared samples have been characterized by Raman and FTIR spectroscopies, SEM, TEM, AFM, and thermogravimetic analysis. It is shown that a large number of TiO₂ nanoparticles homogeneously cover the surface of high‐quality graphene sheets. The graphene exhibits a multi‐layered structure (5–7 layers). Notably, the TiO₂–graphene composite (only 30 wt % of which is TiO₂) synthesized by subsequent thermal treatment at high temperature under nitrogen shows high photocatalytic activity in the degradation of phenol under visible and UV lights in comparison with bare Degussa P25. The enhanced photocatalytic performance is attributed to increased charge separation, improved light absorbance and light absorption width, and high adsorptivity for pollutants.     

Comparison of cure,mechanical, electric properties of EPDM filled with Sm2O3 treated by different coupling agents

Composites based on ethylene–propylene–diene rubber (EPDM) were prepared. EPDM was reinforced with 100 phr Sm₂O₃ treated with coupling agents: stearic acid (SA), isopropyl tri(dioctylphosphate) titanate (NDZ102), bis-[-3-(triethoxysilyl)propyl]tetrasulfide (KH845-4), and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (SG-Si602), respectively. Cure, mechanical and electrical properties of the composites were investigated. It was found that carboxyl in coupling agents could retard EPDM cure while amino groups, PO bonds and S atoms could accelerate EPDM cure. Amino groups enhanced composite mechanical properties by forming additional rigid C–C linkages, whilst S atoms boosted composite mechanical properties by generating flexible S–C linkages. PO bonds might be subject to cleavage during vulcanization and form flexible P–C linkage. Thus, composites with NDZ102 and KH845-4 treated filler exhibited better mechanical properties than that with SG-Si602 treated filler. In addition, treatment of filler could reduce composite electrical properties due to interfacial improvement.     

Combined effect of pH level and surface treatment of Sm2O3, SmBO3 and ATO particles on cure,mechanical and electric properties of EPDM composites

The aim of this study is to investigate the effect of pH level and surface treatment of samarium oxide (Sm₂O₃), samarium borate (SmBO₃) and Sb-doped SnO₂ (ATO) particles on properties of peroxide-cured ethylene–propylene–diene rubber (EPDM) composites. The bis-(-3-(triethoxysilyl)propyl)tetra-sulfide (KH845-4) treated particles were added to EPDM at various filler contents. The pH values of particles, and cure, mechanical and electric properties of the EPDM composites were evaluated. It was found that alkaline SmBO₃ particles would accelerate cure by producing more radicals from dicumyl peroxide (DCP), but acidic ATO particles would retard vulcanization because of making DCP generate less radicals, and neutral Sm₂O₃ particles did not affect the cure process. Moreover, sulfuric linkages from KH845-4 on the filler surface would provide sulfuric radicals to form S–C linkages. Therefore, composites with SmBO₃ exhibited excellent mechanical properties. Additionally, polar fillers could reduce electrical properties of composites due to increased composite polarity.     

Morphology,structure, and photoactivity of two types of graphene oxide-TiO<Subscript>2</Subscript> composites

Two types of graphene oxide-TiO₂ composites were prepared: one by including graphene oxide flakes in the TiO₂ sol, followed by thermal treatment (GI composite) at 300°C, and the second by including graphene oxide flakes in the calcined (at 500°C) TiO₂ xerogel (GII composite). The composites were characterized by SEM, TEM-EDS, TEM-SADP, STEM-HAADF, HRTEM coupled with FT, XRD, and XPS. Photocatalysis results were fitted to different kinetic models (pseudo-first and pseudo-second kinetics, intraparticle Weber-Morris diffusion, film diffusion, and external mass transfer). The results showed that by introducing graphene oxide flakes in the TiO₂ sol, followed by thermal treatment at 300°C (GI composite), an efficient graphene oxide-TiO₂ catalyst with high specific surface area, heterogeneity, and many graphitized areas can be obtained. Complete crystallization of the composite is not the key issue for the best photoactivity achievement. The rate limiting step in the photocatalytic process is the photooxidation of SA molecules on the TiO₂ surface.     

Facile Preparation and Lithium Storage Properties of TiO2@Graphene Composite Electrodes with Low Carbon Content

Over the past decade, TiO₂/graphene composites as electrodes for lithium ion batteries have attracted a great deal of attention for reasons of safety and environmental friendliness. However, most of the TiO₂/graphene electrodes have large graphene content (9–40 %), which is bound to increase the cost of the battery. Logically, reducing the amount of graphene is a necessary part to achieve a green battery. The synthesis of TiO₂ nanosheets under solvothermal conditions without additives is now demonstrated. Through mechanical mixing TiO₂ nanosheets with different amount of reduced graphene (rGO), a series of TiO₂@graphene composites was prepared with low graphene content (rGO content 1, 2, 3, and 5 wt %). When these composites were evaluated as anodes for lithium ion batteries, it was found that TiO₂+3 wt % rGO manifested excellent cycling stability and a high specific capacity (243.7 mAh g^?1 at 1 C; 1 C=167.5 mA g^?1), and demonstrated superior high‐rate discharge/charge capability at 20 C.     

Studies on the properties of EPDM–CSE blend containing HTPB for case‐bonded solid rocket motor insulation

Elastomeric blends based on ethylene propylene diene (EPDM) rubber as a primary polymer have been investigated for the thermal insulation of case‐bonded solid rocket motors (SRMs) cast with composite propellant containing hydroxy terminated polybutadiene (HTPB) as a polymeric binder. EPDM rubber found as an attractive candidate for the thermal insulation of case‐bonded SRM due to the advantages such as low specific gravity, improved ageing properties, and longer shelf life. In spite of these advantages, EPDM, a non‐polar rubber, lacks sufficient bonding with the propellant matrix. Bonding properties are found to improve when EPDM is blended with other polar rubbers like polychloroprene, chlorosulphonated polyethylene (CSE), etc. This type of polar polymer when blended with EPDM rubber enhances the insulator‐to‐propellant interface bonding. In the present work, an attempt has been made to study the properties of EPDM–CSE based insulator by incorporating HTPB, a polar polymer as well as a polymeric binder, as an additive to the EPDM–CSE blend by varying the HTPB concentration. Blends prepared were cured and characterized for rheological, mechanical, interface, and thermal properties to study the effect of HTPB addition. This paper reports the preliminary investigation of the properties of EPDM–CSE blend containing HTPB, as a novel and futuristic elastomeric insulation for case‐bonded SRM containing HTPB as propellant binder. Copyright © 2007 John Wiley & Sons, Ltd.     

Radiation effect on properties of carbon black filled NBR/EPDM rubber blends

Rubber blend of acrylonitrile butadiene rubber (NBR) and ethylene-propylene diene monomer (EPDM) rubber (50/50) has been loaded with increasing contents, up to 100 phr, of reinforcing filler, namely, high abrasion furnace (HAF) carbon black. Prepared composites have been subjected to gamma radiation doses up to 250 kGy to induce radiation vulcanization under atmospheric conditions. Mechanical properties, namely, tensile strength (TS), tensile modulus at 100% elongation (M₁₀₀), and hardness have been followed up as a function of irradiation dose and degree of loading with filler. On the other hand, variation of the swelling number as a physical property, as a function of same parameters, however, in car oil as well as brake oil has been undertaken. In addition, the electrical properties of prepared composites, namely, their electrical conductivity, were also evaluated. The thermal behavior of the prepared composites was also investigated. The results obtained indicate that improvement has been attained in different properties of loaded NBR/EPDM composites with respect to unloaded ones.     

Effect of polyphenylsilsesquioxane on the ablative and flame-retardation properties of ethylene propylene diene monomer (EPDM) composite

Polyphenylsilsesquioxane (PPSQ) microspheres with ladder structure synthesized in the laboratory have been incorporated into ethylene propylene diene monomer (EPDM) composite in order to study the effect of PPSQ on the ablative and flame-retardation properties of EPDM composites. The results showed that PPSQ microspheres serve as an effective ablative additive and flame retardant for EPDM composites. Thus, PPSQ greatly improved the ablative properties of EPDM composites, with a 4.8 wt% loading leading to a remarkable reduction in the linear ablation rate of EPDM by about 50%. Moreover, this loading of PPSQ improved the flame retardancy and smoke suppression, and significantly reduced the PHRR of EPDM composite from 504 kW/m² to 278 kW/m². Moderate tensile strength could be obtained and the breaking elongation was improved for the EPDM/PPSQ composites. TGA results showed that PPSQ had little influence on the thermal decomposition of EPDM. SEM, CONE, and TG-FTIR tests showed that the char structure of EPDM composites was the primary factor through which PPSQ affected the ablative and flame-retardation properties of EPDM. The chars formed during the ablation of EPDM composites containing PPSQ had better structural stability and thermal stability, owing to the fact that they were denser, remained intact, and had an ordered arrangement of holes.     

Enhancement of photovoltaic performance of polyaniline/graphene composite-based dye-sensitized solar cells by adding TiO2 nanoparticles

Polyaniline (PANi)-graphene composites and polyaniline-graphene/TiO₂ composites were prepared by ex-situ approach. Systematic investigation was carried out to explore photovoltaic (PV) properties of PANi-graphene and PANi-graphene/TiO₂ composite. The prepared composites were characterized using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Raman Spectroscopy and Ultraviolet–Visible (UV–Vis) Spectroscopy. The PV properties of dye-sensitized solar cells (DSSCs) prepared composites investigated by assembling materials in ITO/PANi-graphene/Al and ITO/PANi-graphene/TiO₂/Al architecture. Different PV parameters such as short circuit current, open circuit voltage, fill factor and power conversion efficiency were determined from the (Current-Voltage) IV characteristics of PV cell. The 15 wt% PANi loaded graphene composite based PV cell shows optimized power conversion efficiency of the order 6.47%. The main accomplishment of present work is that efficiency associated with 15 wt% PANi loaded graphene composite, improved further by addition of TiO₂ nanoparticles. The composite system between PANi-graphene/TiO₂ for 1 wt% of TiO₂ nanoparticles shows optimized power conversion efficiency of the order 8.63%.     

Mechanical properties and morphological structures of short glass fiber reinforced PP/EPDM composite

The mechanical properties and crystal morphological structures of short glass fiber (SGF) reinforced dynamically photo-irradiated polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM) composites were studied by mechanical tests, wide-angle X-ray diffraction (WAXD), optical microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). The mechanical properties of PP/EPDM composites, especially the tensile strength were greatly strengthened by dynamically photo-irradiation and the incorporation of SGF. The results from the WAXD, SEM, DSC, and TGA measurements reveal: (i) the formation of β-type crystal of PP in the PP/EPDM/SGF composite; (ii) the fiber length in dynamically photo-irradiated PP/EPDM/SGF composites are general longer than that in corresponding unirradiated samples. The size of EPDM phase in the photo-irradiated composites reduces obviously whereas the droplet number increases; (iii) photo-irradiation improves the interface adhesion between SGF and polymer matrix; (iv) the melting and crystallization temperatures of the photo-irradiated composites are not affected greatly by increasing the SGF content; (v) the thermal analysis results show that the incorporation of SGF into PP/EPDM plays an important role for increasing its thermal stability.     

Effect of Ionizing Radiation on the Characteristics of EPDM/UHMW-PE Composites

Ultra high molecular weight polyethylene (UHMW-PE) fibers were used in a chopped form and at different concentrations as a reinforcing material in ethylene–propylene–diene terpolymers (EPDM). The effect of radiation dose and fiber concentration on the mechanical properties of the vulcanized rubber composites obtained was measured. It was found that γ-irradiation improves the interfacial adhesion between UHMW-PE fiber (Spectra 1000) and EPDM matrix which was detected by scanning electron microscopy (SEM). In addition, the Young modulus of the composites increases as the irradiation dose increases. Increasing the concentration of the fibers up to 40 phr leads to an enhancement in mechanical properties and swelling resistance of obtained composites, especially in the absence of carbon black. The absolute value of the modulus increased by a factor of at least two with the addition of carbon black. Moreover the tear strength of reinforced and filled EPDM was improved with respect to reinforced rubber. © 1997 John Wiley & Sons, Ltd.     

Structure and mechanical properties of SRP/HDPE/POE (EPR or EPDM) composites

The effects of dicumyl peroxide (DCP) and ethylene-octylene copolymer (POE), ethylene-propylene copolymer (EPR) or ethylene-propylene-diene terpolymer (EPDM) on the structure and properties of scrap rubber powder (SRP)/high-density polyethylene (HDPE) composites were studied. Torque and gel content results show that DCP promotes crosslinking of the SRP/HDPE/POE (EPR or EPDM) composites. The SRP/HDPE/POE (EPR or EPDM) composites containing a small amount of DCP have better mechanical properties than their corresponding composites without DCP. Highest tensile strength and elongation at break are found in the dynamically vulcanized SRP/HDPE/POE composite. Scanning electron microscopy (SEM) results show that good bonding between SRP and matrix is formed in the SRP/HDPE/POE (EPR or EPDM) composites with DCP.     

Comparative study on the effect of partial replacement of silica or calcium carbonate by bentonite on the properties of EPDM composites

The effects of the partial replacement of silica or calcium carbonate (CaCO₃) by bentonite (Bt) on the curing behaviour, tensile and dynamic mechanical properties and morphological characteristics of ethylene propylene diene monomer (EPDM) composites were studied. EPDM/silica/Bt and EPDM/CaCO₃/Bt composites containing five different EPDM/filler/Bt loadings (i.e., 100/30/0, 100/25/5, 100/15/15, 100/5/25 and 100/0/30 parts per hundred rubber (phr)) were prepared using a laboratory scale two-roll mill. Results show that the optimum cure (t₉₀) and scorch (t_S2) time decreased, while the cure rate index (CRI) increased for both composites with increasing Bt loading. The tensile properties of EPDM/CaCO₃/Bt composites increased with the replacement of CaCO₃ by Bt from 0 to 30 phr of Bt. For EPDM/silica/Bt composites, the maximum tensile strength and E_b were obtained at a Bt loading of 15 phr, with enhanced tensile modulus on further increase of Bt loading. The dynamic mechanical studies revealed a strong rubber-filler interaction with increasing Bt loading in both composites, which is manifested by the lowering of tan δ at the glass transition temperature (Tg) for EPDM/CaCO₃/Bt composites and tan δ at 40 °C for EPDM/silica/Bt composites. Scanning electron microscopy (SEM) micrographs proved that incorporation of 15 phr Bt improves the dispersion of silica and enhances the interaction between silica and the EPDM matrix.     

Enhanced thermal conductivity and mechanical properties of polymeric composites through formation of covalent bonds between boron nitride and rubber chains

Hexagonal boron nitride (BN) platelets, also known as white graphite, are often used to improve the thermal conductivities of polymeric matrices. Due to the poor interfacial compatibility between BN platelets and polymeric matrices, in this study, polyrhodanine (PRd) was used to modify BN platelets and prepared functionalized BN-PRd platelets, thereby enhancing the interfacial interaction between the thermal conductive filler and polymeric matrix. Then, BN-PRd platelets were dispersed into the nitrile butadiene rubber (NBR) matrix to yield high thermally conductive composites. The presence of N? C═S groups in PRd allowed the combination of PRd and NBR chains containing stable covalent bonds via vulcanization reaction. The thermal conductivity of the as-prepared 30 vol% BN-PRd/NBR composite reached 0.40 W/mK, representing an increment of 135% over pure NBR (0.17 W/mK). In addition, the largest tensile strength of NBR composite containing 30 vol% BN-PRd platelets was 880% times of pure NBR. The 30 vol% BN-PRd/NBR composite also displayed a relatively high dielectric constant (9.35 at 100 Hz) and a low dielectric loss tangent value (0.07 at 100 Hz), indicating their usefulness as dielectric flexible materials of microelectronics. In sum, the simplicity and good efficiency of formation of covalent bonds between boron nitride and rubber chains look very promising for large-scale industrial production of high thermally conductive composites.     

Preparation of nanoalumina/EPDM composites with good performance in thermal conductivity and mechanical properties

In this paper, nanoalumina (Al₂O₃) highly filled ethylene propylene diene monomer (EPDM) composites are prepared, and the mechanical (static and dynamic) properties and thermal conductivity are investigated systemically through various characterization methods. Furthermore, influences of in situ modification (mixing operation assisted by silane at high temperature for a certain time) with the silane‐coupling agent bis‐(3‐triethoxy silylpropyl)‐tetrasulfide (Si69) and stearic acid (SA) pretreatment on the nano‐Al₂O₃ filled composites are as well investigated. The results indicate that nano‐Al₂O₃ particles can not only perform well in reinforcing EPDM, but also improve the thermal conductivity significantly. Assisted by in situ modification with Si69, the mechanical properties (especially dynamic mechanical properties) of the nano‐Al₂O₃ filled composites are improved obviously, without influencing the thermal conductivity. By comparing to the traditional reinforcing fillers, such as carbon black (grade N330) and silica, in situ modified nano‐Al₂O₃ filled composites exhibit excellent performance in mechanical (static and dynamic) properties as well as better thermal conductivity, especially lower compression heat build‐up and better fatigue resistance. In general, our work indicates that nano‐Al₂O₃, as the novel thermal conductive reinforcing filler, is suitable to prepare rubber products serving in dynamic conditions, with the longer expected service life. Copyright © 2010 John Wiley & Sons, Ltd.     

Radiation effects on SBR–EPDM blends: A correlation with blend morphology

The effect of γ radiation on the morphological and physical properties of Styrene–butadiene rubber (SBR) and Ethylene–propylene–diene monomer (EPDM) blends has been investigated. An attempt has been made to establish a correlation between various parameters like Gordon–Taylor parameter (k), hydrodynamic interaction parameter (Δ[η]_mix), chemical shift factor (b), Charlesby–Pinner parameter (p₀/q₀) and polymer–polymer interaction parameter (χ). The results showed a close dependence of mechanical and physical properties of irradiated blends on these parameters. The probability of spur overlap has been found to increase with the increase in EPDM content in the blends, which in turn results in significant improvement in the mechanical properties of the irradiated SBR–EPDM blends with higher EPDM fraction. The efficiency of four multifunctional acrylates as crosslinking aid for the radiation‐induced vulcanization of SBR–EPDM blend was also studied. The results established lower efficiency of methacrylates over acrylates in the process and indicated that among the crosslinking agents studied trimethylolpropane triacrylate is the most efficient one. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1676–1689, 2006     

Synergistic flame retardant effects of nano-kaolin and nano-HAO on LDPE/EPDM composites

A novel flame retardant system composed of nano-kaolin and nano-HAO (nano-sized hydroxyl aluminum oxalate) was used for flame retarding the low density polyethylene (LDPE)/ethylene propylene diene rubber (EPDM) blends. Results of fire testing showed that nano-kaolin and nano-HAO exhibited excellent synergistic effects on the flame retardancy of the LDPE/EPDM composites. When 12 wt% nano-kaolin took the place of 12 wt% nano-HAO in the composites, the LOI of the composites increased from 31.0% to 35.5% and the composites could meet the UL94V-0 standard. Through thermogravimetric and differential thermal analysis (TG-DTA) it was found that nano-HAO mainly affected the degradation of the experimental composites chemically. Meanwhile, results of scanning electronic microscope (SEM) and Fourier transformation infrared spectra (FTIR) of the composites on the char layer revealed that nano-kaolin mainly affected the transfer process physically by aggregating with nano-HAO and thus the synergistic effect on flame retardancy appeared.     

Investigations on the structural,mechanical, thermal,and electrical properties of Ce-doped TiO2/poly(n-butyl methacrylate) nanocomposites

This study focused on the fabrication of poly(n-butyl methacrylate) (PBMA) nanocomposites with various concentrations of cerium-doped titanium dioxide (Ce–TiO₂) nanoparticles via in situ polymerization technique. The structural characterization and the material properties of all the composites were analyzed by UV–visible, FTIR, XRD, SEM, DSC, TG, and tensile strength measurements. The UV–visible and FTIR studies confirmed the effective inclusion of Ce–TiO₂ nanoparticles into the PBMA matrix. The change in amorphous morphology of PBMA to a crystalline structure was observed from the XRD pattern. The SEM morphology revealed the attachment of nanoparticles in the polymer matrix. The inclusion of Ce–TiO₂ nanoparticles enhanced the glass transition temperature, and thermal stability of the PBMA matrix was revealed from DSC and TG, respectively. The tensile strength of PBMA was greatly enhanced by the addition of Ce–TiO₂ nanoparticles. The AC conductivity, dielectric constant, and dielectric loss studies were also performed in the frequency range 10²–10⁶ Hz, and it was observed that addition of Ce–TiO₂ nanoparticles greatly enhanced the electrical properties of PBMA. The change in dielectric constant with the addition of nanoparticles was correlated with a theoretical modeling study. This work also extended to study the role of Ce–TiO₂ nanoparticles in the reinforcing mechanism of the nanocomposite by comparing the actual tensile strength of the composite with different theoretical modeling. The high dielectric constant and tensile strength of composite are beneficial in designing lightweight and highly efficient nanoelectronic materials based on the family of polybutyl acrylates.