Study on biodegradable polymer materials based on poly(lactic acid). I. Chain extending of low molecular weight poly(lactic acid) with methylenediphenyl diisocyanate

Methylenediphenyl diisocyanate (MDI) was used as the chain extender for low molecular weight poly(lactic acid) (PLA) to produce high molecular weight biodegradable polymer material with a better heat resistance. PLA prepolymer with a number‐average molecular weight (M_n) of 5800 and a weight‐average molecular weight (M_w) of 9800 was produced by direct polycondensation using stannous octoate as the catalyst. After 40 min of chain extension at 175°C, the resulting polymer had a M_n of 15,000 and a M_w of 57,000. The glass transition temperature (T_g) of the low molecular weight PLA prepolymer was 48.6°C. After chain extension, the T_g of the resulting polymer was raised to 67.9°C, as determined by DSC. DMA results also indicate that the heat resistance was improved by the chain extension. The DSC spectrum and X‐ray diffraction pattern of annealed samples showed that both the crystallinity and rate of crystallization of PLA were lowered by chain‐extension reaction due to the formation of branched molecular structure. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2546–2551, 1999     

聚烯烃无卤阻燃剂研究进展与发展趋势

初步概括了无机阻燃剂和膨胀型阻燃剂的阻燃机理,综述了近10年聚烯烃无机阻燃剂和膨胀型阻燃剂的研究进展及发展趋势。     

Influence of phthalic anhydride and bioxazoline on the mechanical and morphological properties of biodegradable poly(lactic acid)/poly[(butylene adipate)‐co‐terephthalate] blends

Poly(lactic acid) (PLA)/poly[(butylene adipate)‐co‐terephthalate] (PBAT) blends were fabricated by melt blending, with 2,2′‐(1,3‐phenylene)bis(2‐oxazoline) (BOZ) and phthalic anhydride (PA) used as compatibilizers. It was found that a small amount of BOZ or PA greatly increased the elongation at break of the PLA/PBAT blends without sacrificing their high tensile strength. Scanning electron microscopy results revealed that the PBAT particles became finer and were uniformly dispersed in the matrix when the compatibilizers were incorporated, which indicated that the interfacial bonding and compatibilization between PLA and PBAT were improved in the presence of the compatibilizers. Compared with PLA/PBAT blends, the molecular weight of PLA/PBAT/PA/BOZ blends was increased due to chain‐extending reactions. Differential scanning calorimetry results suggested PBAT decreased the crystallization rate and crystallinity of PLA in the blends. Moreover, the glass transition temperature of PBAT was further decreased when the compatibilizers were used. © 2013 Society of Chemical Industry     

Crystallization,Morphological, and Mechanical Response of Poly(Lactic Acid)/Lignin-Based Biodegradable Composites

Green/bio-based composites of poly(lactic acid) and lignin were prepared by melt blending in a twin-screw extruder. Thermal and mechanical properties, phase interaction, and morphology of the composites have been investigated. Fourier transform infrared studies elucidated the existence of intermolecular hydrogen bonding between poly(lactic acid) and lignin. Scanning electron microscopy studies revealed an extent of diffused phase boundaries between poly(lactic acid) and lignin which also indicated significant interaction between them. Tensile properties showed significant increase over neat poly(lactic acid) with lignin loading (0–0.28 volume fraction) which further justified using theoretical models. Izod impact strength decreased with lignin content.     

L-乳酸低聚物的异氰酸酯扩链反应工艺研究

采用直接熔融缩聚法制备L-乳酸低聚物。在氮气氛围下,使用六亚甲基二异氰酸酯(HDI)、二苯基甲烷二异氰酸酯(MDI)作扩链剂,研究了反应时间、温度、反应官能团配比、低聚物粘均相对分子质量(Mη)等对扩链反应的影响,对扩链产物进行了红外光谱表征及差示扫描量热分析。结果表明:HDI和MDI对L-乳酸低聚物均有较好的扩链效果,扩链反应规律基本相同;HDI的扩链效果优于MDI,扩链反应速率快,扩链时间短,扩链产物Mη高、熔点高、热性能好;较佳扩链反应工艺参数:nNOC∶nOH为1:1,反应温度165℃,HDI扩链时间20 min、MDI扩链时间30 min,L-乳酸低聚物M越高,扩链产物M越高。     

不同膨胀型阻燃剂改性聚丙烯/聚乳酸复合材料

用两种不同的膨胀型氮磷阻燃剂(IFR1和IFR2)阻燃改性聚丙烯(PP)/聚乳酸(PLA)复合材料。结果表明:两种阻燃剂在PP/PLA基体中都具有良好的分散性和界面粘合性。阻燃剂的加入降低了材料的力学性能,而含有25%阻燃剂的PP/PLA复合材料就能到达垂直燃烧试验(UL-94)的V0等级。燃烧过程中阻燃剂通过在材料表面形成致密的炭层来提高材料的阻燃性,其中IFR1对PP/PLA体系的阻燃改性效果更好。从力学性能和阻燃效果的双重考虑,质量含量25%的阻燃剂适合于PP/PLA材料的阻燃改性。     

基于异氰酸酯衍生物的聚乳酸熔融扩链工艺、动力学及结构表征

以微波法氧化锌（ZnO）柱撑有机皂石催化丙交酯开环聚合的聚乳酸(PLA)为原料,分别采用二苯基甲烷二异氰酸酯 (MDI)和六亚甲基二异氰酸酯(HDI)进行熔融扩链反应,研究了扩链剂的用量和反应时间对PLA相对分子质量的影响,并对PLA的扩链动力学进行了研究。结果表明,最优的扩链反应工艺参数为：反应温度180 ℃,nNCO：nOH为2.5：1,MDI扩链时间为45 min,HDI扩链时间为30 min;MDI和HDI扩链反应的表观速率常数分别为6.081×10^3、6.98×10^3 g/(mol·min)。     

Preparation and characterization of double-layered microencapsulated red phosphorus and its flame retardance in poly(lactic acid)

A novel double-layered microencapsulated red phosphorus (DMRP) has been prepared through chemical precipitation of aluminum trihydrate (ATH) and in situ polymerization of melamine formaldehyde (MF) resin on the red phosphorus (RP) powder surface, and its structure was characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The influence of DMRP on flame retardance and thermal stability of poly(lactic acid) (PLA) was thoroughly investigated by means of X-ray diffractometry (XRD), limiting oxygen index (LOI), vertical burning test, and thermogravimetric analysis (TGA). With an optimum mass ratio of RP/ATH/MF = 72.25%/12.75%/15%, it has been found that PLA with the addition of DMRP at 25 wt % loading level shows good flame retardance compared to plain RP as well as the conventional microencapsulated red phosphorus (CMRP), and can achieve UL94 V-0 rating along with an LOI increase from 20.5 to 29.3. The TGA and XRD studies indicate that the interaction occurs among all three components: RP, ATH, and MF resin. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

新型聚氨酯酰亚胺的合成及其性能

以4,4′-二氨基二苯醚、偏苯三酸酐和过量的一缩二乙二醇为原料合成了一种含有酰亚胺基团的二醇,用NCO封端的聚氨酯预聚物和含有酰亚胺基团的二醇通过溶液聚合反应合成了一种新型的聚氨酯酰亚胺弹性材料。利用红外光谱（FT-IR）、差示扫描量热分析（DSC）、热失重分析（TGA）等方法对产物进行了表征。研究表明：酰亚胺基团的引入能够明显改善该共聚物的热分解性能,初始分解温度提高了近12%,在600 ℃时的分解剩余量提高了18%;两种嵌段共聚物均出现两个玻璃态转变温度T_g,它们在N₂中均呈现出两个失重台阶;聚合物能较好地溶解在强极性非质子有机溶剂中,且对无机稀酸具有一定的抗腐蚀性能。     

Effect of surface acetylated‐chitin nanocrystals on structure and mechanical properties of poly(lactic acid)

In this work, the miscibility between chitin nanocrystals (ChNs) and poly(lactic acid) (PLA) was expected to be improved by surface acetylation of ChN. The reaction of acetic anhydride onto the ChN surface was confirmed by FTIR and ¹³C NMR, while XRD and TEM proved the crystalline structure and rod‐like morphology were maintained. The acetylated ChN (AChN) was incorporated into a PLA matrix by solution blending, and resulted in an increase of tensile strength and Young's modulus and they reached to the maximum value as 45 and 37% higher than neat PLA film, respectively, with the loading level of AChN reaching to 4 wt %. The enhancement could be attributed to that acetylation improved dispersion of AChN in the PLA matrix and interfacial adhesion between AChN and PLA. The performances of the nanocomposites based on PLA and chitin nanocrystals derived from renewable resources have good potential for industrial applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39809.     

Viscoelastic,thermo-mechanical and environmental properties of composites based on polypropylene/poly(lactic acid) blend and copper modified nanoclay

Poly(lactic acid) (PLA)/polypropylene (PP) blends composites were prepared by incorporating 3 wt.% of copper modified montmorillonite (MMT-Cu²⁺), obtained using cation exchange in a CuSO₄ solution, and 10 wt.% of polypropylene-graft-maleic anhydride (PP-g-MA) as a compatibilizer then varying the PLA content until 50 wt.%. These materials were subjected to several investigations such as X-rays diffraction, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile and environmental tests. The DMTA analysis showed that the glassy PLA high stiffness and the PP crystalline phase compensate the decrease in the storage modulus occurring during the PP and PLA glass transitions, respectively. The variations of tan δ revealed no changes on the PP and PLA phases glass transitions temperatures which indicate the immiscibility of the two polymers, as supported by DSC analysis. Blends composites SEM micrographs stated the immiscibility of the system resulting in the poor adhesion of the PLA droplets to the PP matrix. Also, the blends composites exhibited intermediate tensile properties between those of PP and PLA. The incorporation of MMT-Cu²⁺ to the (50/50) PP/PLA blend accentuated its aptitude to water absorption and ensured an efficient antimicrobial activity over a satisfactorily long period of around six months.     

二氯苯基膦(BPD)的合成和应用

介绍了二氯苯基膦(BPD)的合成方法及其应用。BPD可用于制备苯基膦酰二氯等中间体、聚酯纤维的反应型阻燃剂2-羧乙基(苯基)次膦酸(CEPPA)、特殊反应的催化剂和对阔叶杂草有很好选择性的农药。     

聚乳酸的阻燃改性研究进展

综述了近年来国内外聚乳酸（PLA）阻燃改性的研究进展,对磷系、磷氮系、硅系、膨胀型、无机纳米粉体等各种环境友好型阻燃体系在PLA树脂中的应用现状进行了概述,探讨了各自的阻燃机理,并展望了PLA阻燃改性的发展前景。     

橡实淀粉/聚乳酸复合材料的制备与结构性能研究

采用熔融挤出法制备了橡实淀粉 (AS)/聚乳酸 (PLA)二元复合材料。通过对复合材料力学性能、吸水性、熔融指数 (MIR)、扫描电镜 (SEM)、动态机械热分析 (DMA)和热稳定性 (TG)的测试,研究了橡实淀粉含量对复合材料的力学性能、疏水性能和热性能的影响。研究表明,随着AS加入量的增加,复合材料的刚性逐渐增强,在AS质量分散50%的情况下,拉伸强度仍达47.19 MPa。熔融流动性能、拉伸和弯曲强度则略微有所下降,其玻璃化转变温度略向高温偏移,保持在57 ℃。制备的复合材料具有优异的疏水性能,即使在AS加入量高达50%的情况下,接触角可达63.26°,吸水率仅为2.68%。     

Flammability and mechanical properties of wood flour‐filled polypropylene composites

Polypropylene (PP) composites filled with wood flour (WF) were prepared with a twin‐screw extruder and an injection‐molding machine. Three types of ecologically friendly flame retardants (FRs) based on ammonium polyphosphate were used to improve the FR properties of the composites. The flame retardancy of the PP/WF composites was characterized with thermogravimetric analysis (TGA), vertical burn testing (UL94‐V), and limiting oxygen index (LOI) measurements. The TGA data showed that all three types of FRs could enhance the thermal stability of the PP/WF/FR systems at high temperatures and effectively increase the char residue formation. The FRs could effectively reduce the flammability of the PP/WF/FR composites by achieving V‐0 UL94‐V classification. The increased LOI also showed that the flammability of the PP/WF/FR composites was reduced with the addition of FRs. The mechanical property study revealed that, with the incorporation of FRs, the tensile strength and flexural strength were decreased, but the tensile and flexural moduli were increased in all cases. The presence of maleic anhydride grafted polypropylene (MAPP) resulted in an improvement of the filler–matrix bonding between the WF/intumescent FR and PP, and this consequently enhanced the overall mechanical properties of the composites. Morphological studies carried out with scanning electron microscopy revealed clear evidence that the adhesion at the interfacial region was enhanced with the addition of MAPP to the PP/WF/FR composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical and thermal properties of biocomposites from poly(lactic acid) and DDGS

Distillers dried grains with solubles (DDGS), an ethanol industry coproduct, is used mainly as a low‐value feedstuff. Poly(lactic acid) (PLA) is a leading biodegradable polymer, but its applications are limited by its relatively high cost. In this study, low‐cost, high‐performance biodegradable composites were prepared through thermal compounding of DDGS and PLA with methylene diphenyl diisocyanate (MDI) as a coupling agent. Mechanical, morphological, and thermal properties of the composites were studied. The coupling mechanism of MDI in the PLA/DDGS system was confirmed via Fourier‐transform infrared spectra. The PLA/20% DDGS composite with 1% MDI showed tensile strength (77 MPa) similar to that of pure PLA, but its Young's modulus was 25% higher than that of pure PLA. With MDI, strong interfacial adhesion was established between the PLA matrix and DDGS particles, and the porosity of the composites decreased dramatically. Crystallinity of PLA in the composites was higher than that in pure PLA. Composites with MDI had higher storage moduli at room temperature than pure PLA. This novel application of DDGS for biocomposites has significantly higher economic value than its traditional use as a feedstuff. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

生物基阻燃剂阻燃聚乳酸的研究进展

针对生物基阻燃剂在绿色阻燃聚乳酸（PLA）领域的应用,简要介绍了生物基阻燃剂的阻燃改性技术,重点分析和综述了近5年含纤维素、木质素、壳聚糖、植酸、环糊精以及淀粉等生物基阻燃剂阻燃PLA的研究进展。最后,指出目前生物基阻燃剂应用和发展存在的问题,并对生物基阻燃剂在PLA阻燃领域发展的趋势进行了展望。