Degradation of linear low-density polyethylene/poly(vinyl alcohol)/kenaf composites

The interest of this study was to examine various kenaf (KNF) loadings and burial time, and their effects on degradability behavior of linear low-density polyethylene/poly(vinyl alcohol)/kenaf (LLDPE/PVOH/KNF) composites in soil. The LLDPE/PVOH/KNF composites with various KNF loadings were melt-mixed in a Thermo Haake internal mixer. The composites were buried in soil and their extent of degradability was assessed by tensile properties, morphological study, and weight loss and crystallinity measurements of the degraded composites. Fourier transform infrared spectroscopy was utilized to monitor the changes in chemical structure of the composites before and after degradation in soil. The results showed that with increase in KNF loading, the tensile modulus increased; meanwhile, the tensile strength and elongation-at-break of the degraded composites were dropped. Tensile properties of the degraded composites were decreased with prolonging soil burial time. The formation of cracks and pores was observed in field emission scanning electron microscope micrographs. By measuring the weight loss in LLDPE/PVOH/KNF composite samples before and after the soil burial testing and differential scanning calorimetry measurements, it was found that the weight loss and crystallinity of the composites increased with soil burial time. The degradation of the composites was confirmed by the formation of a strong absorption band assigned to carbonyl groups.     

三种植物纤维填充聚乳酸复合材料性能对比

为充分利用农作物植物资源,以稻秸秆、麦秸秆、稻壳三种植物纤维为填充相,聚乳酸(PLA)为基体,制备了PLA/植物纤维复合材料。对三种植物纤维的成分进行了对比分析,并对制备的复合材料的力学性能和吸水性能进行了比较,分析了三种复合材料的热重曲线、差示扫描量热曲线与红外光谱,并用扫描电子显微镜观察了复合材料的断面微观结构。结果表明,三种植物纤维材料中稻秸秆的纤维素与半纤维素总含量最高,稻秸秆制备的PLA复合材料力学性能与界面结合性最好,其弯曲强度为28 MPa,分别比麦秸秆和稻壳制备的PLA复合材料高75%和47%;PLA/稻壳复合材料的吸水率最小,比PLA/稻秸秆和PLA/麦秸秆分别小10%与25%;三种植物纤维改性PLA复合材料的热分解曲线基本相同,PLA/稻壳复合材料的热稳定性相对最好。     

Thermal degradation and biodegradability of poly (lactic acid)/corn starch biocomposites

Thermal degradation and biodegradability of poly (lactic acid) (PLA) and poly (lactic acid)/corn starch (PLA/CS) composites with and without lysine diisocyanate (LDI) were evaluated by thermogravimetric analysis measurement and enzymatic degradation using Proteinase K and burial tests, respectively. Thermal stability was decreased by addition of CS and the composites with LDI showed higher thermal degradation temperature than those without LDI. In enzymatic biodegradation, the weight remaining of all samples decreased almost linearly with time. The addition of CS resulted in a faster rate of degradation and the composites with LDI were more difficult to degrade than those without it. In the composite without LDI, the degradation was faster at the interface between PLA and CS, showing deep and wide clearance, but degradation starting at the interface was not clearly observed in the composite with LDI. There was no considerable difference in molecular weight and distribution of the samples after enzymatic degradation. The lactic acid content of the water‐soluble product obtained after enzymatic degradation increased with degradation time. In burial tests, pure PLA was little degraded but the composites gradually degraded. The degradation of the composite without LDI was faster than that of the composite with LDI. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3009–3017, 2006     

聚磷酸铵对聚乳酸/麦秸秆复合材料阻燃和力学性能的影响

用聚磷酸铵(APP)对聚乳酸(PLA)/秸秆粉复合材料进行阻燃处理,对复合材料的阻燃性能、力学性能和热降解行为进行了分析。结果表明,APP添加量达到20份时,极限氧指数提高了33 %,成炭率提高了330 %,而且达到UL 94 V-0级,表现出显著的阻燃作用;APP的加入降低了复合材料的冲击性能,但能改善其刚性,对弯曲强度和密度影响不大;此外APP的添加还改变了复合材料的热降解行为,使其分解温度提前,稳定了PLA基体;材料燃烧后膨胀成多孔炭层,起到了隔热和阻氧的作用。     

Thermal properties and characterization of surface-treated RSF-reinforced polylactide composites

The thermal, mechanical, and biodegradation properties of composite materials made from polylactide (PLA) and rice straw fibre (RSF) were evaluated. To improve the properties of PLA/RSF composites, glycidyl methacrylate (GMA)-grafted polylactide (PLA-g-GMA) and treated (crosslinked) rice straw fibre (TRSF) were used to prepare the composites. The result showed that PLA-g-GMA/TRSF had noticeably superior mechanical properties compared with PLA/RSF because of greater compatibility between the polymer and TRSF. The dispersion of TRSF in the PLA-g-GMA matrix was more homogeneous, because branched and crosslinked macromolecules formed via condensation of the glycidyl methacrylate groups of PLA-g-GMA and the hydroxyl groups in TRSF. In addition, the PLA-g-GMA/TRSF composites were more easily processed because of their lower melt viscosities. The water resistance of PLA-g-GMA/TRSF was higher than that of PLA/RSF, although the weight loss of composites buried in soil compost indicated that both were biodegradable, especially at high levels of RSF substitution. The PLA/RSF and PLA-g-GMA/TRSF composites were more biodegradable than was pure PLA.     

In vitro degradation behavior of carbon fiber-reinforced PLA composites and influence of interfacial adhesion strength

In the present study, carbon fiber-reinforced polylactide (C/PLA) composites with different interfacial conditions were prepared to determine the influence of interfacial adhesion strength (IAS) on in vitro degradation behavior of the C/PLA composites. Pure PLA and untreated and treated C/PLA composite samples were immersed in phosphate buffered saline (PBS; pH 7.4, 37 ± 0.5^°C) for predetermined time periods. These samples were removed at each degradation time, measured to analyze molecular weight loss, weighed to assess water uptake and mass loss, and mechanically tested to obtain bending strength, modulus, and IAS. The matrixes in the C/PLA composites showed higher water uptake and lower mass loss in comparison with the pure PLA. Further, the PLA matrix in the treated composite absorbed less water and lost less mass and molecular weight than its counterpart in the untreated composite. Mechanical tests confirmed that the treated C/PLA composite exhibited a slower rate of decrease in bending strength, modulus, and IAS than the untreated one. The differences in degradation behavior between two composites can only be attributed to the difference in interfacial conditions because all other parameters were kept constant. The loss of bending strength and modulus was mainly caused by the interface degradation of the C/PLA composites. It can be concluded from our in vitro observations that the IAS had an obvious influence on the degradation characteristics of the C/PLA composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 150–158, 2001     

Degradation of PLA and PLA in composites with triacetin and buriti fiber after 600 days in a simulated marine environment

Poly(lactic acid) (PLA), the polymer object of this study, degrades by a biotic process after an abiotic hydrolysis process. Its degradation was evaluated after 600 days of exposure in a simulated marine environment (SME), as buriti fiber‐reinforced composites having triacetin as coupling agent. Composites were obtained by extrusion and films were produced by compression molding. After between 60 and 600 days of exposure, PLA had a weight loss of 2.5%, PLA/T of 1.5%, and 10–12% of weight loss for PLA/B and PLA/B/T, respectively. PLA intercalates reduction, increase, and decrease of its crystallinity attributed to hydrolysis (up to 15 days), impairment of amorphous segments (45 days), and loss of integrity of the matrix (100–600 days), respectively. In the PLA/T composites, triacetin inhibited the diatom colonization process, having its crystallinity values increased after nearly 100 days of exposure with subsequent reduction. For samples with buriti fiber, changes in crystallinity were attributed to absorption of water and exposure of matrix amorphous segments. PLA degradation in a SME is evidently favored by the use of natural fibers since they make easier water access to the matrix and colonization by the protists group, diatoms, showing that the polymer can have reduced post‐use shelf life as composites, with benefits while in use and at the same time post‐use environmental benefits. Triacetin inhibits PLA colonization and degradation up to 45 days after exposure, after which it no longer influences the degradation process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43290.     

Thermal and biodegradation properties of poly(lactic acid)/fertilizer/oil palm fibers blends biocomposites

Poly(lactic acid) (PLA) and NPK fertilizer with empty fruit bunch (EFB) fibers were blends to produced bioplastic fertlizer (BpF) composites for slow release fertilizer. Thermal properties of BpF composites were investigated by thermogavimteric analysis (TGA), differential scanning calorimetry (DSC), and morphological and degradation properties were anlayzed by scanning electron microscopy (SEM), soil burial test, respectively. TGA themogram display that neat PLA, PLA/NPK, and BpF composites degradate at different temperatures. DSC curves of PLA and other composites exhibited same glass transition temperature (T_g) value indicating that both major blend components are miscible. The T_g, crystallization temperature (T_c), melting temperature (T_m) values also decreased with increased amount of fertilizer and fibers. The T_m of BpF composites did not change with an increase in fertilizer content because thermal stability of PLA and PLA/NPK composites was not affected. Soil burial and fungal degradation test of PLA, PLA/NPK, and BpF composites were also carried out. Soil burial studies indicated that BpF composites display better biodegradation as compared with neat NPK. Fungal degradation study indicated that fungi exposure times of BpF composites show higher value of degradation as compared with PLA/NPK. We attribute that developed BpF composites will help oil palm plantation industry to use it as slow release fertilizer. POLYM. COMPOS. 36:576–583, 2015. © 2014 Society of Plastics Engineers     

Influences of degradability,bioactivity, and biocompatibility of the calcium sulfate content on a calcium sulfate/poly(amino acid) biocomposite for orthopedic reconstruction

The inorganic content in a bioceramic/polymer composite is considered to play an important role in promoting bone healing after implantation in vivo. In this study, two calcium sulfate/poly(amino acid) (CS/PAA) composites with CS content proportions of 50% (mass fraction, 50CS/PAA) and 65% (65CS/PAA) were synthesized via the in situ melting polymerization method, and the degradability, bioactivity, and biocompatibility of the composites were evaluated. The results indicated that 41.5% of weight loss of the 50CS/PAA was observed after soaking in simulated body fluid (SBF) for 16 weeks, whereas 56.2% of weight loss of the 65CS/PAA was observed. These results suggested that the CS content in the composite affected the degradability of the composite. After being soaked in SBF for 1 week, formation of an apatite layer was observed on the surfaces of both composites without obvious differences. The co‐culture results of the composites and the MG‐63 cells confirmed that 65CS/PAA exhibited higher proliferation and a higher alkaline phosphatase (ALP) activity than did 50CS/PAA. The implantations in bone defects of rabbits for 3 months revealed that both composites had good biocompatibility and were capable of guiding new bone formation without causing any inflammation. However, faster degradability of the 65CS/PAA composite was observed in vivo, indicating that the higher CS content in the composite results in higher degradability. In conclusion, the CS content in the composite for orthopedic reconstruction has distinct effects on the degradability, OD value, and ALP activity of the composites, whereas it has little effect on the bioactivity and bone formation. POLYM. COMPOS., 37:1886–1894, 2016. © 2015 Society of Plastics Engineers     

Thermal properties of extruded injection‐molded poly(lactic acid) and milkweed composites: Degradation kinetics and enthalpic relaxation

To determine the degree of compatibility between poly(lactic acid) (PLA) and different biomaterials, PLA was compounded with milkweed fiber, a new crop oil seed. After oil extraction, milkweed remaining cake retained approximately 10% residual oil, 47% protein, and 10% moisture. The fiber (300 μm) was added at 85 : 15 and 70 : 30 PLA : Fiber and blended by extrusion (EX) followed by injection molding (IM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used for testing the composites. After melting in the DSC sealed pans, composites were cooled by immersion in liquid nitrogen and aged (stored) at room temperature for 0, 7, 15, and 30 days. After storage, samples were heated from room temperature to 180°C at 10°C/min. The pure PLA showed a glass transition (T_g) at 60.3°C and the corresponding ΔCp was 0.464 J/g/°C followed by crystallization and melting transitions. The enthalpic relaxation (ER) of neat PLA and composites steadily increased as a function of storage time. Although the presence of fiber had little effect on ER, IM reduced it. The percentage crystallinity of neat unprocessed PLA dropped by 95 and 80% for the EX and IM, respectively. The degradation activation energy (E_a) of neat PLA exhibited a significant drop in nitrogen environment, whereas increased in air, indicating PLA resistant to heat degradation in the presence of oxygen. Overall, IM appeared to decrease E_a of the composites, whereas milkweed significantly reduced E_a values in nitrogen environment. Enzymatic degradation of the composites revealed higher degradation rate for the EX samples versus IM, whereas 30% milkweed exhibited higher weight loss compared to the 15%. The degradation mechanism was observed by looking at the percent conversion as a function of E_a from the TGA data, where multisteps degradation occurred mostly in air. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of K+ and Na+ ions on the degradation of wet‐spun alginate fibers for tissue engineering

A synthetic type of wet‐spun alginate fibers were immersed in simulated body fluid(SBF) composed of K⁺, Na⁺, and Ca²⁺ cations with various concentrations. Experimental measurements revealed that Na⁺ had a greater impact on degradability than that of K⁺ ion. The finding was further confirmed by the characterization of mass loss, ICP, XRD, and theoretical analyses. The degradation process and mechanism were demonstrated through the research on swelling behavior and mass loss. Besides, the wet‐spun alginate fibers were characterized by FT‐IR, XRD, and SEM. The results showed that the degradation mechanism could be attributed to the ion‐exchange between Ca²⁺ of the synthetic alginate fibers and Na⁺, K⁺ of the solutions under the osmotic pressure. The synthetic fibers were swelled and then degraded faster with the presence of Na⁺ ion presented greater influence on degradability compared with K⁺ ion. The degradation results of a mechanical rupture of fibers due to excessive water uptake without the occurrence of any chemical changes in the spun alginates structure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44396.     

Surface‐modified halloysite nanotubes reinforced poly(lactic acid) for use in biodegradable coronary stents

Poly(lactic acid) (PLA) was reinforced halloysite nanotubes (HNTs) in this study. To improve dispersion and interfacial adhesion of HNTs within the PLA matrix, HNTs were surface modified with 3‐aminopropyltriethoxysilane (ASP) prior to compounding with PLA. PLA/ASP‐HNTs nanocomposites were characterized by differential scanning calorimetry (DSC), Fourier transfer infrared spectroscopy (FTIR), surface wettability, thermogravimetric analysis, transmission electron microscopy (TEM), and tensile testing. The hemocompatibility and cytocompatibility of PLA and PLA composites were investigated and the in vitro degradation process of PLA/ASP‐HNTs composites was investigated for a period of 6 months by gel permeation chromatography, FTIR, weight loss measurement, DSC, and tensile testing. PLA and all PLA composites were blood compatibile and non‐cytotoxic. TEM analysis revealed that HNTs agglomeration in PLA matrix was reduced by surface treatment with ASP. ASP‐HNTs had better reinforcing effect than unmodified HNTs evidenced by tensile testing. ASP‐HNTs appeared to increase the hydrolytic degradation process as measured by weight measurement. PLA/ASP‐HNTs composites displayed 12.1% weight loss and 30.6% average molecular weight reduction while retaining 74% of Young's modulus by the 24th week of degradation. Based on this data, the reinforcement of PLA using ASP‐HNTs may prove beneficial for applications such as biodegradable stents. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46521.     

聚乳酸/蒙脱石复合材料的溶液插层法制备及其性能表征

的界面相容性良好.聚乳酸/蒙脱石复合材料的热失重曲线移向高温端,其热分解温度提高,表明其热稳定性比PLA基材提高.聚乳酸及聚乳酸/蒙脱石复合材料在不同环境中的初步降解实验结果表明该复合材料具有较好的生物可降解性.     

海藻酸钠纳米复合材料的研究应用进展

海藻酸钠纳米复合材料是将海藻酸钠与纳米材料通过相应的技术制备得到的聚合物纳米复合材料,由于其具有良好的理化性质、功能特性、生物相容性及特殊的纳米效应,因而受到国内外学者的广泛关注。本文简介了海藻酸钠纳米复合材料的理化特性及功能特性,综述了其在生物医药、食品及工业中的应用研究进展,主要介绍了该类材料在药物载体、组织工程支架、抗菌材料及创伤敷料、食品包装、工业生产及污水处理等方面的研究及进展,并指出该复合材料具有光明的应用前景,但仍需要从制备工艺的优化、安全性能的科学评价等方面解决其在应用商业化面临的问题以加速其发展。     

Roles of Calcium,Zinc, Copper and Titanium Compounds on the Degradation of Polymers

In this article, the influences of the metallic filler content upon the thermal degradability of polymer composites such as initial degradation temperature, maximum degradation temperature and char content have been critically reviewed using thermogravimetric analysis. Besides that, the review on the relationship between activation energies of polymer/metal composites, which was obtained from various degrade models, and the content of metallic fillers have also been defined. Other thermal properties such as glass transition temperature (T_g) and melting temperature (T_m) have also been reviewed based on the evaluation of differential scanning calorimetry (DSC) analysis.     

3D打印PLA/麦秸粉复合材料的力学性能优化

将聚乳酸(PLA)作为基体,麦秸粉作为增强体,通过挤出成型工艺制备用于熔融沉积成型3D打印的木塑复合材料。采用正交试验设计的方法,通过对复合材料的力学性能进行测试,探索最佳的制备工艺。结果表明,随着麦秸粉平均粒径的增加,复合材料的弯曲强度与冲击强度出现先上升后下降的趋势,当平均粒径为120μm时,弯曲强度与冲击强度分别达到60.51 MPa,12.84 k J/m~2;麦秸粉的含量在1%时,复合材料的弯曲强度与冲击强度达到最大值,分别为62.87 MPa,12.72 k J/m~2;硅烷偶联剂KH550的加入会提高复合材料的力学性能,对冲击强度的作用效果强于弯曲强度,当KH550的添加量为8%时,冲击强度达到12.90 k J/m~2;马来酸酐接枝聚丙烯相容剂(MAPP)的添加会使复合材料的弯曲强度与冲击强度先上升后下降,当MAPP含量为1%时,复合材料的弯曲强度与冲击强度分别为62.68 MPa,11.91 k J/m~2,达到最大值。     

Degradation and bioavailability of dried alginate hydrocolloid capsules in simulated soil system

Hydrocolloid capsules are common chemical carriers used in many types of applications in foods, biotechnology, and agriculture. Alginate microbeads and macrobeads are some of the more prevalent types of hydrocolloid capsules. Most studies to date have focused on alginate carrier applications but only a few have looked at their bioavailability after use. In this study, alginate carriers were subjected to simulated field conditions and their biodegradation in the soil was evaluated by respiration measurements, visualization, and volatile solids reduction. Using respiration rate, the degradation rate was calculated at 32 ± 3.1% (w/w) after 2 months. The visually estimated volume and volatile solids reduction gave degradation rates of 40 ± 8.6% (v/v) and 22.5 ± 2.5% (w/w), respectively. Moreover, water-loss calculations suggested that the carriers can serve as a stand-alone soil amendment for water retention. These findings emphasize the importance of studying hydrocolloid bioavailability in the soil and alginate carrier suitability for future applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48142.     

PLA/SPI复合纤维的制备及性能研究

以氯仿和乙醇为共溶剂,静电纺丝制备不同比例的聚乳酸（PLA）/大豆分离蛋白（SPI）复合纤维。PLA/SPI复合纤维的平均直径介于108～304nm,并随着体系中SPI含量的增大而变细;相同SPI含量下,随PLA分子量的增大,纤维直径变粗。FT-IR和XRD分析结果显示,SPI的引入破坏了PLA的晶体结构,且复合纤维中SPI与PLA通过氢键缔合。吸水率和失重率分析结果表明,PLA/SPI复合纤维较纯PLA纤维的亲水性和降解性能随SPI含量的增大而提高更快。     

Retardation effect of nanohydroxyapatite on the hydrolytic degradation of poly (lactic acid)

Poly (lactic acid) (PLA) and PLA/nanohydroxyapatite (nHA) composites, containing 2 wt% and 5 wt% of nHA were subjected to in vitro hydrolytic degradation tests in saline phosphate solution at different temperatures (37°C, 48°C, 60°C, and 72°C) to accelerate degradation. Samples were characterized by water uptake, weight loss tests, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and visual analyses. Arrhenius equation was used to describe the behavior of weight loss as a function of time. The PLA activation energy of weight loss showed to be lower than that of the PLA/nHA composites, indicating that the incorporation of nHA retarded the hydrolytic degradation. The rate and percentage of weight loss increased with increasing temperature. All samples presented a decrease in T_g and an increase in degree of crystallinity as a function of time. Incorporation of nHA retarded this behavior that showed to be more expressive in PLA containing 5 wt% nHA.     

分子筛改性可降解材料聚乳酸的研究

将吸附有聚乳酸齐聚物的分子筛同工业级聚乳酸在双螺杆挤出机中造粒,制备了分子筛改性聚乳酸材料。研究了分子筛对聚乳酸力学性能的影响,添加量在7%~9%左右时可以起到最好的增强效果;复合材料可以在土壤中自然降解,增加分子筛添加量可以加快复合材料的降解。