Surface modification of spruce wood flour and effects on the dynamic fragility of PLA/wood composites

Poly (lactic acid) (PLA), a biodegradable aliphatic semicrystalline polyester was filled with 40 wt% spruce wood flour (WF), to produce composite materials. Hydrothermal treatment, as well as maleic anhydride, vinyltrimethoxysilane, and stearic acid surface treatments were applied. The influence of surface modifications for WF was tested in terms of thermal, mechanical, and viscoelastic properties. The recorded results show that in both, the untreated and treated PLA/WF composites, the rigid amorphous phase content has been enhanced. The presence of WF causes a stiffness increase of the PLA/WF composites, while damping factor was decreased. The effect of wood surface modifications on interfacial compatibility with PLA was estimated by dynamic fragility parameter m calculated according the Williams‐Landel‐Ferry equation. The incorporation of untreated WF increased dynamic fragility of PLA/WF composites markedly, whereas used silane, maleic anhydride and hydrothermal treatments lead to lower values of parameter m. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Morphological,mechanical, and physical properties of composites made with wood flour‐reinforced polypropylene/recycled poly(ethylene terephthalate) blends

Wood flour (WF)‐filled composites based on a polypropylene (PP)/recycled polyethylene terephthalate (r‐PET) matrix were prepared using two‐step extrusion. Maleic anhydride grafted polypropylene (MAPP) was added to improve the compatibility between polymer matrices and WF. The effects of filler and MAPP compatibilization on the water absorption, mechanical properties, and morphological features of PP/r‐PET/WF composites were investigated. The addition of MAPP significantly improved mechanical properties such as tensile strength, flexural strength, tensile modulus, and flexural modulus compared with uncompatibilized composites, but decreased elongation at break. Scanning electron microscopic images of fracture surface specimens revealed better interfacial interaction between WF and polymer matrix for MAPP‐compatibilized PP/r‐PET/WF composites. MAPP‐compatibilized PP/r‐PET/WF composites also showed reduced water absorption due to improved interfacial bonding, which limited the amount of absorbable water molecules. These results indicated that MAPP acts as an effective compatibilizer in PP/r‐PET/WF composites. POLYM. COMPOS., 38:1749–1755, 2017. © 2015 Society of Plastics Engineers     

Effects of alkali treatment on the properties of WF/PLA composites

In this study, composites of thermoplastic poly (lactic acid) filled with wood flour (WF) were prepared via melt extrusion. Before that, alkali treatment was performed on WF to improve the properties of the WF/PLA composite materials. The effect of the solution concentrations of NaOH, namely 0.5, 1.0, 5.0, and 10.0%, on mechanical properties of the composites was evaluated. The results showed that the properties of the composites with treated WF were enhanced greatly compared with that of the untreated composites. The composites had a best improvement in its compatibility and mechanical strength when the concentration of NaOH solution was 5.0%. The brittle fracture of composites showed that the chemical modification of WFs improved the compatibility between the filler and matrix.     

Study on the mechanical and thermal properties of poly(lactic acid)/office waste paper fiber composites

Environment friendly composites with favorable mechanical properties and low water absorption performance were successfully produced from poly(lactic acid) (PLA), office waste paper fiber (OWF), and coupling agents. The perfect sample was easily manufactured by melting–blending and injection molding. The PLA/OWF composites were comparable with other PLA/plant fiber composites, and the results indicated that the PLA/OWF composites show better performance than PLA/wheat straw fiber composites and PLA/bamboo fiber composites. On this basis, influence of modification of OWF on the properties of composites was investigated. The infrared results show that the OWF modification by different coupling agents was successful, and the scanning electron microscopy indicates that prepared composites exhibit good interfacial compatibility due to preferable binding force between fiber and matrix. With addition of 2 wt% γ-(2,3-propylene oxides)propyl trimethylsilane, the composite exhibits high tensile strength of 58.96 MPa, reflecting increase of 14% than the pure PLA. According to the crystallization and melting performance table, OWF can act as nucleating agent to promote the crystallization properties on composites, while the coupling agents have little effect on thermal stability. This article confirmed that the OWF has appropriate properties and is suitable for preparing composite materials and this work provides a novel idea for the utilization of office waste paper.     

Influences of Ternary Graft Copolymers on the Morphology and Properties of Polypropylene/Calcium Carbonate Composites

The ternary graft copolymers were synthesized by solid-phase grafting maleic anhydride (MAH), methyl methacrylate (MMA), and butyl acrylate (BA) onto polypropylene (PP), and applied in the interfacial modification of the PP/Calcium carbonate (CaCO₃) composites. Fourier transform infrared (FTIR) spectroscopy was used to analyze the structure of the ternary graft copolymers. Scanning electron microscopy (SEM), thermogravimetry (TG), differential scanning calorimetry (DSC), and dynamic rheological testing were used to investigate the morphology and the properties of the composites. FTIR results confirmed the occurrence of the solid-phase graft copolymerization, and SEM exhibited the improvement of the compatibility between PP and CaCO₃ by PPTM. The properties testing showed that PPTM significantly contributed to the reinforcement of the composites in terms of mechanical properties, thermal properties, and rheological properties by acting as interfacial modifiers and plasticizers. The preferable loadings of PPTM for the properties improvement of the PP/CaCO₃ composites were between 7 and 9 phr.     

Enhancing the durability of poly(lactic acid) composites by nucleated modification

Biodegradable poly(lactic acid) (PLA) composites were prepared using an innovative combination of wood fiber (WF) and 1,3,2,4‐bis(3,4‐dimethylobenzylideno)sorbitol (DMDBS). DMDBS acted as an effective nucleating agent, which improved the mechanical properties and slowed down the degradation of the WF/PLA composites. The enzymatic degradation of the composites was examined by immersing in proteinase K or cellulase buffer. The presence of DMDBS resulted in a 26.7% increase of the crystallinity compared to the WF/PLA composites. The increase in crystallinity enhanced the thermal stability and tensile strength of the WF/DMDBS/PLA composites by 8.5%. The durability of the WF/DMDBS/PLA composites after nucleated modification was enhanced after enzymolysis. After nucleated modification, the surface of the WF/PLA composites showed clear cracks due to degradation, while these appeared about 2 weeks later in the case of the WF/DMDBS/PLA composites. The results revealed that the introduction of cellulase degraded WF in the composites, which increased hydrolysis or enzymolysis sites. The combination of nucleated modification and enzyme buffer gave an expanded downstream application of WF/PLA composites in packaging and agricultural materials. © 2019 Society of Chemical Industry     

Preparation and properties of L‐lactide‐grafted sisal fiber–reinforced poly(lactic acid) composites

Pretreatment of the sisal fiber (SF) grafting with L‐lactide (LA) monomer via a ring‐opening polymerization catalyzed by a Sn(II)‐based catalyst was performed to improve the interfacial adhesion between SF and poly (lactic acid) (PLA). Biocomposites from LA‐grafted SF (SF‐g‐LA) and PLA were prepared by compression molding with fiber weight fraction of 10, 20, 30, and 40%, and then were investigated in contrast with alkali‐treated sisal fiber (ASF) reinforced PLA composites and untreated SF reinforced PLA composites. PLA composites reinforced by half‐and‐half SF‐g‐LA/untreated SF (half SF‐g‐LA) were prepared and studied as well, considering the disadvantages of SF‐g‐LA. The results showed that both the tensile properties and flexural properties of the SF‐g‐LA reinforced PLA composites were improved noticeably as the introduction of SF‐g‐LA, compared with pure PLA, untreated SF reinforced PLA composites and ASF reinforced PLA composites. The mechanical properties of the half SF‐g‐LA reinforced PLA composites were not worse, even better in some aspects, than the SF‐g‐LA reinforced PLA composites. Fourier transform infrared analysis and differential scanning calorimetry analysis exhibited that both the chemical composition and crystal structure of the SFs changed after LA grafting. In addition, the fracture surface morphology of the composites was studied by scanning electron microscopy. The morphological studies demonstrated that a better adhesion between LA‐grafted SF and PLA matrix was achieved. POLYM. COMPOS., 37:802–809, 2016. © 2014 Society of Plastics Engineers     

Physical,mechanical, and thermal properties of micronized organo‐montmorillonite suspension modified wood flour/poly(lactic acid) composites

In this study, micronized organo‐montmorillonite (OMMT) suspension was prepared with sodium‐montmorillonite (Na‐MMT), didecyl dimethyl ammonium chloride, and dispersant polyethylene glycol 1000 by a ball‐milling process. Then, wood flours (WFs) were impregnated with prepared OMMT suspension at a concentration of 0.5, 1.0, 2.0, or 4.0%. WFs were characterized by X‐ray diffraction and scanning electron microscopy. The hygroscopicity of WF was investigated by a vapor adsorption method. WFs were, respectively, blended with poly (lactic acid) (PLA) to produce WF/PLA composites. Thereafter, physical, mechanical, and thermal properties of the composites were tested. The results showed that a great amount of OMMT attached on the surface of WF, partly penetrating into the microstructure of WF. Owing to the hydrophobicity of OMMT, the vapor adsorption of OMMT‐modified WF decreased. The composite which was produced by WF treated with 0.5% OMMT suspension, showing an increment in the physical, mechanical, and thermal properties. However, OMMT should not be overloaded. Otherwise, the accumulation of OMMT might cause poor interfacial adhesion between WF and PLA matrix. POLYM. COMPOS., 36:731–738, 2015. © 2014 Society of Plastics Engineers     

Effects of two types of clay on physical and mechanical properties of poly(lactic acid)/wood flour composites at various wood flour contents

To investigate the effects of two types of clay, namely, Na‐montmorillonite (Na‐MMT) and organic‐montmorillonite (OMMT), on poly(lactic acid) (PLA)/wood flour (WF) composites, some physical and mechanical properties including the water sorption, thickness swelling, flexural modulus of rupture (MOR), and modulus of elasticity (MOE) of PLA/WF composites at different WF contents of 0, 20, 40, and 60 wt% were tested in this study. The results showed that: (1) the 24 h water uptake and thickness swelling increased and the flexural MOR and crystallinity decreased with the increasing WF content, whereas the flexural MOE of the composites increased with WF content up to 40 wt% but decreased sharply at WF content of 60 wt%; (2) the addition of Na‐MMT slightly increased the 24 h water uptake as well as the thickness swelling rate below 40 wt%, whereas OMMT reduced the thickness swelling at higher WF contents (40, 60 wt%) although it showed little effect on 24 h water uptake; (3) both Na‐MMT and OMMT could improve the flexural MOR and MOE of PLA/WF composite at WF contents below 40 wt%, and OMMT resulted in more obvious improvement than Na‐MMT. However, they both showed negative effect at WF content of 60 wt%; (4) XRD and FT‐Raman analysis suggested that clays would be attached more on the surface of the WF rather than diffused in the PLA matrix at a higher WF content (60 wt%); (5) SEM analysis proved that the interfacial adhesion of PLA and WF became poorer at WF content above 40 wt%, whereas it could be improved by OMMT modified. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of polyamide 6 reinforcement on the compatibility of high-density polyethylene/environmental-friendly modified wood fiber composites

In order to develop excellent comprehensive mechanical strength and stability in high-density polyethylene (HDPE)/wood fiber (WF) composites, polyamide 6 (PA 6), and WF modified by environmental-friendly high temperature vapor (WF-HTV) were utilized to reinforce the compound system. The properties relating to interfacial compatibility in HDPE/WF-HTV composites were characterized and evaluated by electron universal mechanical instrument, water absorption testing, thermogravimetry, scanning electron microscope, Fourier transfer infrared spectroscopy, and differential scanning calorimetry. The results reveal that this novel compounding system can engender a synergistic effect for interfacial interactions among PA 6, HDPE, and WF-HTV only when the ratio of HDPE to PA 6 is at an optimum level (HDPE:PA 6 = 6:4). The maximum values for flexural strength, modulus, tensile strength, and impact strength can be increased by 82.05, 64.08, 93.47, and 120.45%, respectively, compared with those of HDPE/WF-HTV composites. Additionally, maximum decomposition temperatures for the first and second thermal degradation stages can be increased by 7.17and 8.99 °C, respectively. Water absorption can be effectively controlled at a relatively low level (approximately 1.50%). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47984.     

Compatibilization of poly(lactic acid)/high impact polystyrene interface using copolymer poly(stylene‐ran‐methyl acrylate)

In this work, a surfactant‐free emulsion polymerization method was utilized to synthesize poly(styrene‐ran‐methyl acrylate) (PSMA) at a styrene/(methyl acrylate) mole ratio of 75/25 with the aim to compatibilize high impact polystyrene (HIPS)/poly(lactic acid) (PLA) interface. HIPS/PLA blends with different PSMA contents were prepared. Their phase morphologies, mechanical properties, and rheological and crystallization behaviors were investigated using scanning electron microscopy, tensile tests, rotational rheometry, and differential scanning calorimetry. The rheological results showed that the complex viscosity, storage moduli, and loss moduli of PLA/HIPS blends were enhanced with increasing PSMA content. A decrease in the degree of crystallinity of PLA in PLA/HIPS blends with the addition of PSMA was observed in the differential scanning calorimetry results. It was also revealed that the addition of a small amount of PSMA can effectively improve the compatibility and thus the interfacial adhesion of the PLA/HIPS blends, thereby reducing the size of the HIPS dispersion phase. When 1 wt % of PSMA was used, compared with the PLA/HIPS blends without PSMA, the tensile strength and notched Charpy impact strength of PLA/HIPS blends were improved by 95.3% and 104.8%, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45799.     

超分散剂对聚丙烯复合材料性能的影响

以丙烯酸甲酯,二亚乙基三胺及硬脂酸等为原料,合成超支化分散剂(HBPL),采用傅立叶红外光谱(FT-IR)对其结构进行表征。结果表明:经HBPL改性后,聚丙烯/CaCO3复合材料的界面相容性得到很大的提高,冲击强度、弯曲强度分别比未经分散剂改性粉体的复合材料提高了50.2%和8.8%,复合材料的结晶形态基本保持不变,并采用扫描电镜(SEM)观察复合材料的冲击断面形貌。     

微孔发泡聚乳酸/木纤维复合材料的泡孔结构

引言聚乳酸(PLA)因具有环境友好性和降解性而被用于制备不同泡孔结构的泡沫制品[1],然而PLA呈现低的熔体强度和窄的加工窗口,这不利于以超临界流体(如超临界二氧化碳Sc-CO2)发泡制备微孔PLA材料[2-3]。加入填料(如二氧化硅[4]、羟基磷灰石[5]和蒙脱土[6]等)可改善PLA     

聚乳酸/麦秸秆纤维复合材料力学及吸水性能研究

以西北地区麦秸秆纤维（WSF）和聚乳酸（PLA）为原料,通过熔融共混的方式加工制备了PLA/WSF复合材料,研究了偶联剂γ—氨丙基三乙氧基硅烷（KH550）对PLA/WSF复合材料的力学性能、吸水性能及界面性能的影响。利用傅里叶变换红外光谱仪(FITR)对改性前后的WSF进行分析,采用扫描电子显微镜（SEM）研究了复合材料拉伸断面的形貌变化。结果表明,KH550与WSF中羟基的反应降低了WSF表面极性;随着WSF含量的增加,PLA/WSF复合材料的力学性能最终呈现下降的趋势;经KH550对WSF改性处理, PLA/WSF复合材料的力学性能得到提升,同时降低了复合材料的吸水性;KH550处理改善了WSF与PLA的界面相容性。     

Horseradish peroxidase-mediated functional hydrophobization of jute fabrics to enhance mechanical properties of jute/thermoplastic composites

In this study, nonpolar octyl gallate (OG), dodecyl gallate (DG), and octadecyl gallate (OCG) were grafted onto the surface of hydrophilic jute fabrics, which were mediated by horseradish peroxidase to improve the hydrophobicity of jute materials. The gallate-grafted jutes were characterized by infrared spectroscopy and grafting percentage (Gp), and the hydrophobic properties were evaluated by water contact angle and wetting time measurements. The Gps determined by saponification was 3.91%, 5.12%, and 4.58% for OG, DG, and OCG, respectively. The nonpolar chain length and the grafting rate of the monomers had a considerable effect on the hydrophobicity of the modified jute fabrics. The as-prepared hydrophobized jute fabrics had superior interfacial compatibility with nonpolar resins, such as polypropylene (PP) and polylactic acid (PLA) making them most suitable to be utilized in the development of jute fiber-reinforced thermoplastic composites. The tensile and dynamic mechanical properties of the grafted jute/PP or jute/PLA composites were improved compared with pure PP, PLA, and non-modified jute composites.     

聚乙二醇对聚乳酸/淀粉纳米晶复合材料性能的影响

以聚乳酸（PLA）和淀粉纳米晶（SNC）为主要原料,聚乙二醇（PEG）为增塑剂,采用溶剂蒸发法制备PLA/SNC和PLA/SNC/PEG复合材料,通过差示扫描量热仪（DSC）、热台偏光显微镜（PLM）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）等研究了PEG对复合材料结晶行为、力学性能及界面相容性的影响。结果表明,PEG能够与SNC协同促进PLA结晶,使PLA/SNC/PEG复合材料的结晶速率明显提高;PEG的添加未改变PLA/SNC复合材料的结晶结构;随着PEG含量的增加,PLA/4%（质量分数,下同）SNC复合材料的拉伸强度先升高后下降,断裂伸长率不断提高;当PEG含量为2%时,PLA/4%SNC/2%PEG复合材料的力学性能最佳,拉伸强度为47.86 MPa,断裂伸长率为10.20%,PLA与SNC间界面相容性得到改善。     

Grafting of 3-chloro-2-hydroxypropyl acrylate onto chrome tanned collagen fibers

Grafting of 3-chloro-2-hydroxypropyl acrylate onto chrome tanned collagen fibers, initiated by the redox system bisulfite/persulfate, has been investigated. Using the method of statistical planning of experiments regression equations have been obtained, describing the effect of monomer concentration and of initiation system constituents concentrations on monomer conversion, degree of grafting of collagen, and on physical properties of resulting composites. The relationship between the content of poly(3-chloro-2-hydroxypropyl acrylate) in the composite and the swelling ability, water absorption, and tensile strength of the same is discussed. Moreover, results of morphology investigation of composites, prepared by grafting of various acrylic monomers onto collagen fibers, as obtained by electron microscopy, are presented and discussed.     

Interface compatibility and mechanisms of improved mechanical performance of starch/poly(lactic acid) blend reinforced by bamboo shoot shell fibers

Bamboo shoot shell fibers (BSSFs)/starch/poly(lactic acid) (PLA) ternary composites were prepared by blending BSSFs to starch/PLA matrices for the purpose of expanding BSSFs applications to enhance starch/PLA composites and creating a new low-cost biodegradable composite. The effects of BSSFs content (0–40 wt %) on the physical–mechanical properties were tested and interface compatibility and its mechanism to mechanical performance of BSSFs/starch/PLA composites were characterized by SEM-EDS, TG. The results showed that the mechanical strength, surface wettability, and water absorption of the composites continued improving when the BSSFs content increased from 0% to 20 wt %. However, mechanical modulus increased with increase in BSSFs content. The results of fracture microstructure and thermal property exhibited a good interfacial compatibility at low content of BSSFs and an interface debonding at high content of BSSFs. These investigations indicated that the BSSFs reinforcement to the composite is not consistent with interface compatibility of the ternary composites. The composites should be considered as a kind of green and low-cost biodegradable materials to replace traditional single-phase or multiphase materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47899.     

Reinforcement on the mechanical‐, thermal‐, and water‐resistance properties of the wood flour/chitosan/poly(vinyl chloride) composites by physical and chemical modification

In this study, we aimed to physically and chemically modify wood flour (WF)/chitosan (CS) mixtures to reinforce the mechanical‐, thermal‐, and water‐resistance properties of WF/CS/poly(vinyl chloride) (PVC) composites with a three‐step modification process. This was a vacuum‐pressure treatment of sodium montmorillonite, inner intercalation replacement of organically modified montmorillonite, and surface grafting of glycidyl methacrylate (GMA). The untreated and modified mixtures were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy–energy‐dispersive spectroscopy, thermogravimetric analysis, and contact angle measurement. Meanwhile, the mechanical strengths and water absorption of WF/CS/PVC were estimated. The results indicate that the samples had a better performance after they were modified by montmorillonite (MMT) + GMA than when they were modified by only MMT. MMT and GMA showed a very synergistic enhancement to the mechanical‐, thermal‐, and water‐resistance properties of the WF/CS/PVC composites. Specifically, the maximum flexural and tensile strengths were increased by 10.59 and 12.28%, respectively. The maximum water absorption rate was decreased by 61.99%, and the maximum degradation temperature was delayed to the higher value from 314.3 and 374.9°C in the untreated sample to 388.8 and 412.8°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40757.     

PVC/WF发泡材料的性能研究

采用NaOH溶液、丙烯酸丁酯、甲基丙烯酸甲酯和硅烷偶联剂KH-550分别对木粉(WF)进行表面处理,利用傅立叶变换红外光谱仪对其进行表征,并用处理过的WF增强聚氯乙烯(PVC)树脂,经一步模压法制备PVC/WF发泡材料.对其进行力学性能、物理性能测试,比较不同表面处理方法对该发泡材料各项性能的影响.结果表明,WF经表面处理后制备的PVC/WF发泡材料性能均有所提高,其中以NaOH处理后所得复合材料综合性能最优:拉伸强度提高112%,密度从205.4 kg/m3减小到102.3 kg/m3,吸水率、吸油率和线性收缩率均有大幅度改善.