Effect of nanoclay on shrinkage control of low profile unsaturated polyester (UP) resin cured at room temperature

The addition of a small amount of nanoclay (1-3 wt%) can provide excellent volume shrinkage control of unsaturated polyester (UP)/styrene (St)/poly(vinyl acetate) (PVAc) systems cured at room temperature. PVAc serves as the low profile additive (LPA). In this study, both temperature-induced phase separation of the uncured resin mixture and transmission electron microscopy (TEM) of the cured sample revealed that nanoclay resided in the LPA-rich phase, leading to a higher reaction rate and earlier onset of micro-cracking in the LPA-rich phase or at the interface of the LPA-rich and UP-rich phases. Consequently, an earlier volume expansion during curing was observed in reactive dilatometry, resulting in better shrinkage control. On-line measurement of the composite thickness change during vacuum-infusion liquid composite molding [e.g. the Seemann Composite Resin Infusion Molding Process (SCRIMP)] further proved excellent volume shrinkage control of nanoclay filled systems, leading to a smoother composite surface.     

Kinetic analysis and mechanical properties of nanoclay reinforced unsaturated polyester (UP) resins cured at low temperatures

The reaction between unsaturated polyester (UP) resin and styrene (St) is a heterogeneous free‐radical chain‐growth cross‐linking copolymerization. Curing of the UP/St system in the presence of organically‐modified nanoclay was studied by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. A mechanistic kinetic model based on the free radical copolymerization mechanism was developed to simulate the reaction rate and conversion profiles of UP/St resin mixtures with various nanoclay contents cured at low temperatures. The model parameters were determined from several DSC experiments under isothermal conditions. The model, in conjunction with heat transfer analysis, was able to successfully predict the temperature and conversion profiles during curing in two vacuum‐infusion liquid composite molding (e.g., the Seemann composite resin infusion molding process [SCRIMP]) experiments. The presence of nanoclay particles enhanced the tensile modulus, but reduced the tensile strength of the UP nanocomposites. The fracture toughness parameter K_IC was improved by 30% with the addition of 5 wt% nanoclay. The system with mixed nanoclay and calcium carbonate was found to possess the highest K_IC without sacrificing the tensile strength. POLYM. ENG. SCI., 45:496–509, 2005. © 2005 Society of Plastics Engineers     

Extruded starch–nanoclay nanocomposites: Effects of glycerol and nanoclay concentration

Wheat starch‐Cloisite Na+ nanoclay composites containing different glycerol and nanoclay concentrations were extruded using a twin‐screw extruder. X‐ray diffraction and transmission electron microscopy were used to determine the extent of nanoclay dispersion and thermogravimetric analysis was used to characterize thermal stability of composites. Also, water absorbance was measured for each sample. The extent of nanoclay dispersion in samples containing 47 wt% total plasticizer concentration depended on glycerol concentration. For these samples, adding 5 wt% glycerol produced mostly exfoliated nanoclay, whereas adding 10 or 15 wt% glycerol produced intercalated nanoclay. Also, nanoclay composites exhibited improved thermal stability and reduced water uptake compared to samples with no nanoclay. However, thermal stability and water absorbance were not affected by the extent of nanoclay dispersion. POLYM. ENG. SCI., 47:1898–1904, 2007. © 2007 Society of Plastics Engineers     

Mechanical properties and fracture behaviors of epoxy composites with phase‐separation formed liquid rubber and preformed powdered rubber nanoparticles: A comparative study

Epoxy composites filled with phase‐separation formed submicron liquid rubber (LR) and preformed nanoscale powdered rubber (PR) particles were prepared at different filler loading levels. The effect of filler loading and type on the rheological properties of liquid epoxy resin suspensions and the thermal and mechanical properties of the cured composites as well as the relative fracture behaviors are systematically investigated. Almost unchanged tensile yield strength of the cured epoxy/PR composites is observed in the tensile test compared with that of the neat epoxy; while the strength of the cured epoxy/LR composites shows a maximum value at ∼4.5 wt% and significantly decreases with increasing LR content. The glass transition temperature (T_g) of the cured PR/epoxy has shifted to the higher temperature in the dynamic mechanical thermal analysis compared with that of the cured pure epoxy and epoxy/LR composites. Furthermore, the presence of LR results in highly improved critical stress intensity factor (K_IC) of epoxy resin compared with the corresponding PR nanoparticles. In particular, the PR and LR particles at 9.2 wt% loading produce about 69 and 118% improvement in K_IC of the epoxy composites, respectively. The fracture surface and damage zone analysis demonstrate that these two types of rubber particles induce different degrees of local plastic deformation of matrix initiated by their debonding/cavitation, which was also quantified and correlated with the fracture toughness of the two epoxy/rubber systems. POLYM. COMPOS., 36:785–799, 2015. © 2014 Society of Plastics Engineers     

Dynamically cured PP/MAH-g-SEBS/epoxy blends

Abstract

A new method concerning the simultaneous reinforcing and toughening of polypropylene (PP) is reported. Dynamic cure of the epoxy resin with 2-ethylene-4-methane-imidazole was successfully applied in the PP/maleic anhydride grafted styrene–ethylene–butylene–styrene (MAH-g-SEBS) triblock co-polymer, and the obtained blends were named as dynamically cured PP/MAH-g-SEBS/epoxy blends. The stiffness and toughness of the blends are in a good balance, and the smaller size of the epoxy particle in the PP/MAH-g-SEBS/epoxy blends shows that MAH-g-SEBS was also used as a compatibiliser. The structure of the dynamically cured PP/MAH-g-SEBS/epoxy blends is the embedding of the epoxy particles by MAH-g-SEBS. The cured epoxy particles as organic filler increase the stiffness of the PP/MAH-g-SEBS blends, and the improvement in the toughness is attributed to the embedded structure. The tensile strength and flexural modulus of the blends increase with increasing epoxy resin content, and the impact strength reaches a maximum of 342 J m^?1 at the epoxy resin content of 10wt-%. Differential scanning calorimetry analysis shows that the epoxy particles in the dynamically cured PP/MAH-g-SEBS/epoxy blends could have contained embedded MAH-g-SEBS, decreasing the nucleating effect of the epoxy resin. Wide angle X-ray diffraction analysis shows that the dynamical cure and compatibilisation do not disturb the crystalline structure of PP in the blends.     

Effect of nanoclay on the properties of rosin derivative cross-linked green composite based on chicken feather fiber and modified vegetable oil

Fully biodegradable composites based on waste chicken feather fiber (CF), functionalized epoxidized soybean oil (ESO), rosin derivative and various nanoclay percentages were prepared via compression molding. Rosin derivative was synthesized as a substitute of styrene/divinylbenzene. Nuclear magnetic resonance and Fourier transform infrared spectroscopy confirmed the synthesized rosin derivatives structures. Delamination and distribution of silicate layers were studied by X-ray diffraction and transmission electron microscopy. Scanning electron microscopy was used to analyse compatibility among modified ESO and rosin. FTIR study revealed the interaction between resin, CF, rosin derivative, and nanoclay. The nanoclay loaded composites showed better mechanical properties than the nanoclay free composite. The thermal stability of nanoclay loaded composites were also found to be enhanced. Composites loaded with nanoclay (3 wt%) revealed the least chemical resistance, volumetric swelling and water vapor uptake capacity.     

Control of volume shrinkage and residual styrene of unsaturated polyester resins cured at low temperatures. II. Effect of comonomer

The effect of a comonomer, methyl methacrylate (MMA), on volume shrinkage and residual styrene content of an unsaturated polyester (UP) resin with low profile additives (LPAs) cured at low temperature was investigated by an integrated reaction kinetics-morphology-property analysis. MMA affects the volume shrinkage and residual styrene content differently depending on MMA to styrene (St) CC bond molar ratio. At low MMA/St ratio, residual styrene decreases and the volume shrinkage of the resin system remains unchanged. At high MMA/St ratio, residual styrene can be substantially reduced, but the resin system suffers poor volume shrinkage control. Reactivity of the comonomer MMA and its compatibility to other components in the resin system can explain the observed results. A series of Seemann composites resin infusion molding process (SCRIMP) were conducted to study the relationship among materials, processing, and properties of molded composites in low temperature curing processes.     

The effect of alkali treatment and filler size on the properties of sawdust/UPR composites based on recycled PET wastes

In this study, natural sawdust fillers from acacia were mixed with unsaturated polyester resin (UPR), which was prepared by recycling of polyethylene terephthalate (PET) waste bottles to prepare sawdust/UPR composite. PET wastes were recycled through glycolysis and depolymerized to produce a formulation for the resin. The effects of alkali treatment, filler content, and filler size on the tensile, flexural, hardness, and water absorption of the composites were investigated. The results show that the modulus of both tensile and flexural increased with increasing filler contents, but the tensile and flexural strength of composites decreased. The size of sawdust also played a significant role in the mechanical properties, with smaller size sawdust producing higher strength and modulus. This is due to the greater surface area for filler–matrix interaction. The results also show that alkali treatment causes a better adhesion between sawdust and UPR matrix and improves the mechanical properties of the composites. Furthermore, surface treatment reduced the water absorption of composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Improving glass transition temperature of unsaturated polyester thermosets: Conventional unsaturated polyester resins

Highly crosslinkable unsaturated polyester resins (UPR) have attracted many interests in the application as reinforced matrix materials. Here, we present a systematical study of the influence of different curing conditions and styrene concentrations on resin viscosity and dynamic-mechanical properties of the thermoset. The pure maleic Palapreg® P18-03 was selected as model UPR because of its broad industrial use. By applying newly developed thermal curing profiles (without thermal initiators) and by raising the styrene content, the T_g of the network could be increased up to 206/215°C (1/10 Hz). For the first time, a fast curable UPR based on propylene glycol and neopentyl glycol with a T_g of up to 215°C is described. A partial substitution of problematic styrene with methylmethacrylate, tert-butylacrylate, and maleic anhydride (MA) was studied as well. MA leads to significantly improved resin reactivity. A resin containing 42 wt% styrene and 8 wt% MA yields thermosets with remarkably improved mechanical properties and with a narrower glass transition range compared to the original P18-03.     

腰果酚接枝黄麻纤维不饱和聚酯复合材料的力学性能及界面调控

用甲苯二异氰酸酯与腰果酚(CNSL)合成大分子偶联剂接枝黄麻纤维。以接枝的黄麻纤维为增强体,通用的不饱和聚酯树脂为基体,采用热压方式制备复合材料。比较了纯饱和聚酯树脂、5 %CNSL增韧的不饱和聚酯树脂、25 %碱处理的黄麻纤维不饱和聚酯树脂复合材料和25 %的CNSL接枝黄麻纤维不饱和聚酯树脂复合材料的拉伸强度和冲击强度。结果表明,CNSL接枝于黄麻纤维上;CNSL的加入能提高材料的韧性,黄麻纤维能提高材料的拉伸强度而不能提高材料韧性;25 %CNSL接枝的黄麻纤维不饱和聚酯树脂能提高材料的拉伸强度和韧性,25 %CNSL接枝的黄麻纤维增强含5 %CNSL的不饱和聚酯复合材料,其冲击强度为12.10 kJ/m^2。     

Improvement of UF/fiberglass mat properties used in roofing shingles through emulsion polymers and nanoclay addition

Modification of urea–formaldehyde (UF) resin binder for making fiberglass mats was aimed as a route to enhance its brittleness and improve its mechanical properties. The UF resin modifiers were chosen among pure acrylate emulsion polymers having different glass transition temperatures (T _g). Blends of 10% w/w based on dry modifiers and UF resin were prepared. The most effective modifier was chosen and 4 wt% of nanoclay was added to the UF resin for improvement of its mechanical properties. Morphologies of the fractured surface of the UF-modified films were investigated by scanning electron microscopy (SEM). Coarser texture of the fractured surface was regarded as an increased toughness of the modified UF resin. Investigation of gel time at 100 °C on various modified urea–formaldehyde resins showed that the gel time of the modified UF resins generally decreases with adding polymeric emulsions. It is decreased further when less film forming latex (higher T _g) is used in UF resin. Less film formation on the other hand, promotes easier water release during UF resin curing. Tensile and tear strength of the fiberglass mat composites have been increased up to 300 and 50%, respectively, while additional increase of 33% in tensile strength was obtained when nanoclay was incorporated into the composites. X-ray diffraction (XRD) analysis and Si-mapping through SEM were employed in order to show the dispersion and the distribution of nanoclay in the composites, respectively. The disappearance of the peak at 2θ = 7.22 confirmed the exfoliation of the employed nanoclay.     

高导热苯乙烯丙烯酸树脂复合材料制备及导热性能

苯乙烯丙烯酸树脂为墨粉主要组分,其导热性能提升可显著提高墨粉导热性能,进而延长打印、复印机使用寿命。通过在苯乙烯丙烯酸树脂中添加碳纳米管、石墨烯高导热单一或复合填料,在苯乙烯丙烯酸树脂构建连通导热网络以提高其导热性能。当苯乙烯丙烯酸树脂中添加0.75wt%多壁碳纳米管时,其导热系数可提高至0.1644 W/(m?K),增幅为31.31%;添加1.0wt%羧基改性多壁碳纳米管时,苯乙烯丙烯酸树脂导热系数可提高至0.1751 W/(m?K),增幅为39.86%;在苯乙烯丙烯酸树脂添加多壁羧基改性碳纳米管和石墨烯混合填料时,苯乙烯丙烯酸树脂导热系数可提升至0.2093 W/(m?K),增幅达到67.17%。表明碳纳米管和石墨烯混合填料可在苯乙烯丙烯酸树脂中形成有效的导热网络,从而显著提高苯乙烯丙烯酸树脂导热性能。     

Effect of nanoclay on the mechanical and damping properties of aramid short fibre‐filled styrene butadiene rubber composites

The effect of nanoclay loading on the alteration of tensile and dynamic mechanical properties of aramid short fibre‐filled styrene butadiene rubber composites was investigated. In all the composites, 20 phr of N330 black was used. Dynamic mechanical thermal analysis was used to investigate the viscoelastic damping at lower dynamic strains. Compressive hysteresis was evaluated to characterize higher strain static damping properties. Matrix–fibre interaction and filler distribution were investigated using morphological analyses. Matrix–filler interface, estimated by the half height width of the tan δ peak, plays a major role in energy dissipation. The matrix–fibre interaction parameter shows a similar trend with low strain tensile stress values. Nanoclay addition to the composites leads to improved elongation at break and frequency damping properties. Compressive hysteresis reflects no improvement of hysteresis with nanoclay loading. Dynamic storage moduli, matrix–fibre interaction parameter and energy dissipation properties of the short fibre‐filled composites are negatively affected by nanoclay addition. However, ultimate elongation is improved markedly on nanoclay addition. In respect of tensile strength and elongation at break values, two composite samples (KF5NC10 and KF10NC10) offer optimum properties. Copyright © 2009 Society of Chemical Industry     

碳纳米管/纤维素在不饱和聚酯树脂中的分散性及力学性能研究

在超声改善MWCNT在不饱和聚酯树脂的分散性的基础上,通过非共价官能团化的方法引入处理过的天然填料柠檬酸化纤维素(CNFCA)来增强不饱和聚酯树脂,并采用偏光显微镜、旋转流变仪、透射电子显微镜、扫描电子显微镜、万能试验机等对不饱和聚酯树脂纳米复合材料的结构和性能进行了研究.结果表明,MWCNT的加入可以使不饱和聚酯复合...     

Preparation and properties of multiwalled carbon nanotube/epoxy‐amine composites

Different amounts of multiwalled carbon tubes (MWCNTs) were incorporated into an epoxy resin based on diglycidyl ether of bisphenol A and both epoxy precursor and composite were cured with 4,4′‐diamino diphenyl sulfone. Transmission and scanning electron microscopy demonstrated that the carbon nanotubes are dispersed well in the epoxy matrix. Differential scanning calorimetry measurements confirmed the decrease in overall cure by the addition of MWCNTs. A decrease in volume shrinkage of the epoxy matrix caused by the addition of MWCNTs was observed by pressure–volume–temperature measurements. Thermomechanical and dynamic mechanical analysis were performed for the MWCNT/epoxy composites, showing that the T_g was slightly affected, whereas the dimensional stability and stiffness are improved by the addition of MWCNTs. Electrical conductivity measurements of the composite samples showed that an insulator to conductor transition takes place between 0.019 and 0.037 wt % MWCNTs. The addition of MWCNTs induces an increase in both impact strength (18%) and fracture toughness (38%) of the epoxy matrix with very low filler content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization of nanocomposite laminates fabricated from aqueous dispersion of nanoclay

Preparation of E‐glass/waterborne epoxy prepregs containing natural nanoclay and properties of their composites are presented. Prepregs were prepared by wetting randomly oriented, chopped glass fiber preforms with aqueous dispersion of EpiRez 3522‐W‐60 resin, dicyandiamide, 2‐methylimidazole and natural nanoclay (Cloisite® Na⁺). The nanoclay content of the aqueous dispersion was adjusted to yield final nanoclay contents of 0, 1, 2, and 4 wt%, whereas the glass fiber content is kept constant at 47 wt%. These prepregs were then used to fabricate disk‐shaped composite samples by APA2000 rheometer. Composite samples were tested for interlaminar shear strength, flexural stiffness, and glass transition temperature. The flexural stiffness was observed to increase by more than 26% over the range of nanoclay loading, despite a 13% decrease in interlaminar shear strength. Similarly, glass transition temperature increased from 89°C to above 94°C for the samples comprising 4 wt% nanoclay. X‐ray diffraction analyses indicated 48% increase in the gallery spacing suggesting strong intercalation of the nanoclay platelets by the epoxy matrix. Microstructural observations of the fracture surfaces and polished surfaces show significant differences in the matrix topology and fiber to matrix adhesion. The composites with higher nanoclay content depict uniform and submicron surface features implying homogenous dispersion of nanoclay. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

基于二聚脂肪酸改性苯乙烯聚酯树脂的合成及性能

以C₃₆二聚脂肪酸、邻苯二甲酸酐、顺丁烯二酸酐和1,2-丙二醇为原料合成不饱和聚酯树脂（UPR）。以苯乙烯为交联剂、过氧化苯甲酰为引发剂,固化后得到C₃₆二聚脂肪酸（DFA）改性苯乙烯聚酯树脂。采用FT-IR和SEM表征树脂结构及拉伸断面形貌,研究发现DFA引入树脂主链且发生反应,树脂断裂方式由脆性断裂转变为韧性断裂。通过TG、DSC、拉伸、弯曲、硬度和耐溶剂实验研究了DFA用量对树脂热稳定性、力学性能和耐溶剂性能的影响。当DFA含量为6%（摩尔分数）时,改性UPR材料的综合性能最佳,初始热分解温度由147℃增加到201℃,玻璃化转变温度由146.6℃降低到120.7℃,拉伸强度、断裂伸长率、弹性模量、邵氏硬度、弯曲强度分别是未改性树脂的7.23、2.90、7.84、1.63、5.12倍,而且耐溶剂损失率均降低70%以上。DFA可以改善苯乙烯聚酯树脂的柔韧性,是一种有效的增韧改性剂。     

Polyisobutylene-based modifiers for glass fiber reinforced unsaturated polyesters composites

In order to improve the toughness of glass fiber (GF) reinforced unsaturated polyester resin (UPR), low molecular weight polyisobutylene (LPIB) was selected as the toughening agent. Considering its poor thermal compatibility with UPR matrix, LPIB was first grafted by two small molecular compounds, named maleic anhydride (MAH) and glycidyl methacrylate (GMA) through the novel solvothermal method which was developed in our laboratory. And then, all of these three kinds of low modulus elastomers, including LPIB, MAH grafted polyisobutylene (LPIB-g-MAH) and GMA grafted polyisobutylene (LPIB-g-GMA) were selected to modify GF reinforced UPR (GFRUP) composites. According to the results, incorporation of small amounts of grafted LPIB contributed greatly to the improvement of the toughness of GFRUP composites because of the high flexibility of the molecular chain without obviously influencing other primary properties. Moreover, 4?wt% of elastomer was an optimal amount for promoting the mechanical properties of GFRUP composite. Compared to other liquid rubbers, LPIB-g-GMA had the best toughening effect due to its stronger effect of GMA on UPRGF system. In addition, the impact strength of the modified GFRUP composite was improved up to 2.3 order of that of the unmodified GFRUP composites when 4?wt% LPIB-g-GMA was added. Consequently, LPIB-g-GMA could be employed as an effective toughening agent to GFRUP system. The toughening mechanism, thermal behavior, thermal stability and morphology of GFRUP composite are also discussed. The morphology analysis further proved the increase in toughness through the addition of grafted LPIB.     

Effects of nanoclay on the properties of cardanol‐modified‐resol‐epoxy‐novolac composite material

A nanocomposite based on nanoclay and resol that was modified with cardanol, a natural alkyl phenol, shows improvement for the glass‐fiber‐reinforced epoxy‐composite system. Dispersion of the nanocomposite was investigated by X‐ray, showing good results obtained by the in situ polymerization method. The mechanical properties of the final composites were improved by doping a 6 wt% of nanoclay in cardanol‐modified‐resol (CMR) into the epoxy matrix. The results show that a 15 wt% of CMR in epoxy is a most suitable ratio. Using polyamide as a curing agent instead of other traditional systems, such as anhydrides or amines for epoxy resin, overcame important limitations, further allowing for improved processability. The overall composite performance was enhanced. Additionally, the thermal stability of the system was investigated by thermal gravimetric analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3238–3242, 2007     

空心玻璃微珠/环氧复合材料的制备及性能研究

制备了空心玻璃微珠/环氧复合材料。通过力学性能、固化收缩率、热性能等测试考察了空心玻璃微珠粒径、填充量、硅烷偶联剂处理对树脂及固化物性能的影响。结果表明,硅烷偶联剂改善了空心玻璃微珠与树脂基体的相容性。复合材料的力学性能随着空心微珠粒径减小而增大。随着空心微珠填充量的加大,固化物拉伸强度有所降低,冲击强度和弯曲强度在空心玻璃微珠质量分数为2%时达到最大值,比纯树脂分别提高了30%和34.2%,同时材料的固化收缩率和密度降低,玻璃化转变温度升高。