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%。     

Effect of Chain-Extenders on the Properties and Hydrolytic Degradation Behavior of the Poly(lactide)/Poly(butylene adipate-co-terephthalate) Blends

Biodegradable poly(lactide)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends were prepared by reactive blending in the presence of chain-extenders. Two chain-extenders with multi-epoxy groups were studied. The effect of chain-extenders on the morphology, mechanical properties, thermal behavior, and hydrolytic degradation of the blends was investigated. The compatibility between the PLA and PBAT was significantly improved by in situ formation of PLA-co-PBAT copolymers in the presence of the chain-extenders, results in an enhanced ductility of the blends, e.g., the elongation at break was increased to 500% without any decrease in the tensile strength. The differential scanning calorimeter (DSC) results reveal that cold crystallization of PLA was enhanced due to heterogeneous nucleation effect of the in situ compatibilized PBAT domains. As known before, PLA is sensitive to hydrolysis and in the presence of PBAT and the chain-extenders, the hydrolytic degradation of the blend was evident. A three-stage hydrolysis mechanism for the system is proposed based on a study of weight loss and molecular weight reduction of the samples and the pH variation of the degradation medium.     

Poly(Lactic Acid)-Based Blends With Tailored Physicochemical Properties for Tissue Engineering Applications: A Case Study

Binary blends of poly(L-lactic) acid (PLLA: 201790 Da) and poly(lactide-co-glycolide) (PLGA) (LA:GA = 50:50 mol:mol; 32030 Da) with various compositions were prepared. Physicochemical properties of PLLA/PLGA blends were analyzed. Blends showed a biphasic morphology, with distinct glass transition temperatures, which only slightly approximated compared to pure polymers. Analysis of tensile mechanical properties through the Kerner-Uemura-Takayanagi model showed compatibility for PLLA/PLGA 75/25 blend. Rapid degradation of PLGA phase (2–8 weeks) in PLLA/PLGA 75/25 blend led to porous samples, which appear promising for drug delivery and tissue engineering. A limited inflammatory reaction resulted from subcutaneous implantation of PLLA/PLGA 75/25 in Balb-c mice.     

聚乙二醇二酸(2-羟甲基-3,5,6-三甲基吡嗪)酯的合成及其体外降解性能

以1,1′ 羰基二咪唑(CDI)为缩合剂,用聚乙二醇(PEG) 10000 二酸来修饰2 羟甲基 3,5,6 三甲基吡嗪,产率为92%,通过熔点、IR和HNMR对产物进行了表征,熔点53～55℃,红外特征吸收为1747cm-1(CO),1254cm-1(C—O—C),1HNMR为1 9(—CH3,3H,s),2 2(—CH3,6H,s),4 2(—CH2—,2H,s),3 6(—OCH2—,multi-H,s),对其体外降解性能进行了研究,结果表明,其降解速率与溶液的pH有关(该工作已申请中国发明专利)。     

Comparison of Properties of Poly(Lactic Acid) Composites Prepared from Different Components of Corn Straw Fiber

In recent years, under the pressure of resource shortage and white pollution, the development and utilization of biodegradable wood-plastic composites (WPC) has become one of the hot spots for scholars’ research. Here, corn straw fiber (CSF) was chosen to reinforce a poly(lactic acid) (PLA) matrix with a mass ratio of 3:7, and the CSF/PLA composites were obtained by melt mixing. The results showed that the mechanical properties of the corn straw fiber core (CSFC) and corn straw fiber skin (CSFS) loaded PLA composites were stronger than those of the CSFS/PLA composites when the particle size of CSF was low. The tensile strength and bending strength of CSFS/CSFC/PLA are 54.08 MPa and 87.24 MPa, respectively, and the elongation at break is 4.60%. After soaking for 8 hours, the water absorption of CSF/PLA composite reached saturation. When the particle size of CSF is above 80 mesh, the saturated water absorption of the material is kept below 7%, and CSF/PLA composite has good hydrophobicity, which is mainly related to the interfacial compatibility between PLA and CSF. By observing the microstructure of the cross section of the CSF/PLA composite, the research found that the smaller the particle size of CSF, the smoother the cross section of the composite and the more unified the dispersion of CSF in PLA. Therefore, exploring the composites formed by different components of CSF and PLA can not only expand the application range of PLA, but also enhance the application value of CSF in the field of composites.     

The Preparation and Properties of Bioactive Composites Based on Modification Bioactive Glass and Poly(Lactide-Co-Glycolide)

PLGA/bioactive glass composites were prepared as promising bone-repairing materials. The bioactive glass was fabricated by Sol-gel method. Surface Modification was done to improve the phase compatibility between polymer and the inorganic phase. PLGA/bioactive glass composites were successfully prepared via solution dispersion method. Composites films with different content of bioactive glass were obtained. The mechanical properties of composites were characterized by the three-point-bending test and composites films were investigated by in vitro bioactive test. These results indicate that the fractions of bioactive glass in composites produce no significant influence on mechanical properties. Compared to pure PLGA film the PLGA/bioactive glass composites demonstrate greater capability to induce the formation of apatite particles on the film surface.     

Synthesis and Properties of Composite Biomaterials Based on Hydroxyapatite and Poly(L-Lactide)

Composite biomaterial composed of poly(L-lactide) (PLLA) and hydroxyapatite (HA) was obtained by using the combination of solvent evaporation technique and hot pressing. HA particles in the PLLA matrix were homogeneously dispersed. A typical morphology of brittle failure with a smooth fracture surface was observed. The addition of HA particles changed significantly the appearance of the impact fracture surface to a pattern of multiple cracks. With the increasing of the amount of the HA, the bending strength of composite decreases while the bending modulus increases. The PLLA/HA composite exhibits improved cell compatibility due to the good biocompatibility of the HA particles.     

Effect of Thermoplastic Elastomer on Melt Rheological and Fracture Behavior of Poly(Lactic Acid)

Poly(lactic acid) (PLA) was melt blended with thermoplastic elastomer, maleic anhydride grafted poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS-g-MA) copolymer with varied concentration (10–40?wt%) using twin screw extruder. Dynamic rheological behavior of PLA/SEBS-g-MA blends investigated a transition from liquid-like behavior to solid-like behavior in the composition range of 10–20?wt% of SEBS-g-MA. The capillary rheometer analysis showed enhanced shear viscosity with increase in SEBS-g-MA content. At 10?wt% of SEBS-g-MA, a maximum in the non-essential work of fracture was observed which reflects resistance to crack propagation. Scanning electron microscopy revealed a transition in deformation mechanisms from voids, to fibrillation and cavitation.     

Structure,Performance and Crystallization Behavior of Poly (Lactic Acid)/Humic Acid Amide Composites

Humic acid amide (HA-amide) was prepared by amidation of HA and dodecylamine (DDA) with carbonyl diimidazole (CDI) as coupling reagent. Furthermore, HA-amide was added to poly (lactic acid) (PLA) as a nucleating agent to prepare poly (lactic acid)/humic acid amide composites (PLA/HA-amide) by melt blending. The structure and performance of PLA/HA-amide composites were investigated by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), polarized optical microscopy (POM), and rheological analysis. Non-isothermal crystallization kinetics showed the HA-amide enhanced the crystallization rate of PLA. The results of crystallization behavior of PLA/HA-amide composites showed that HA-amide was an efficient nucleating agent of PLA.     

Effect of Poly(L-lactic acid) on Hydrolytic Degradation of Poly(glycolic acid)

The in-vitro degradation behavior of poly(glycolic acid) (PGA) rods and the composite rods containing poly(L-lactic acid) (PLLA) were investigated via mass loss, pH value change, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Since the degradation rate of PLLA is lower than that of PGA, PLLA/PGA composite rods exhibit a slower degradation rate in comparison with PGA. This finding indicated that it was possible to control the degradation rate of the composites by changing their composition. This result indicates that this kind of composite biomaterial may be applicable to devices for the need of prolonged degradation.     

Physical Properties,Crystallization, and Thermal/Hydrolytic Degradation of Poly(L‐lactide)/Nano/Micro‐Diamond Composites

The effects of incorporated nano/micro‐diamond (NMD) on the physical properties, crystallization, thermal/hydrolytic degradation of poly(L ‐lactic acid) (PLLA) were investigated for a wide NMD concentration range of 0–10 wt.‐%. Incorporated NMD increased the tensile modulus and strength of PLLA films but decreased the elongation at break of PLLA films. Incorporated NMD accelerated the crystallization of PLLA during heating and cooling and increased the absolute crystallization enthalpy of PLLA films (except for an NMD concentration of 10 wt.‐% during cooling) but did not alter the crystallization mechanism. Incorporated NMD increased and decreased the thermal stability of PLLA films for NMD concentrations of 1–5 and 10 wt.‐%, respectively, and increased the hydrolytic degradation resistance of PLLA films.

     

Study on Bulk and Surface Properties of Poly(Lactic Acid)/Fluorinated Polymer Blends

The easy hydrolysis of poly(lactic acid) (PLA) leads to very poor mechanical stability. In order to improve water-resistance of PLA, fluorinated polymer has been chosen for its extremely low surface energy. Besides, n-butyl acrylate (BA) has been introduced into fluorinated polymer by copolymerizing BA with dodecafluorheptylmethylacrylate (FA) to enhance the compatibility of fluorinated polymer and PLA. The bulk and surface properties of PLA/fluorinated polymers blends have been studied. The results show that the compatibility of PLA and fluorinate polymers has been improved by BA and, more importantly, the hydrophobicity of PLA has increased obviously by blending with the fluorinate polymers.     

不饱和聚酯酰胺树脂/聚磷酸钙纤维复合材料及性能研究

通过熔融缩聚法合成出一种低成本的不饱和聚酯酰胺树脂并表征了其性能,以此为基体,以聚磷酸钙纤维(CPPF)为增强体,引入20 %的交联剂乙酸乙烯酯、0.1%~0.3%的引发剂过氧化苯甲酰和0.1%~0.3%的促进剂N,N-二甲基苯胺室温交联后在195℃下深度交联成可完全降解不饱和聚酯酰胺树脂/CPPF复合材料,并研究了其力学和降解性能。结果表明, 随着CPPF含量的增加, 不饱和聚酯酰胺树脂/CPPF复合材料的力学性能尤其是冲击强度有大幅度的提高,但当CPPF含量超过60 %（质量分数,下同）时,复合材料的力学性能出现下降的趋势;复合材料在模拟体液环境中降解7周后,降解介质的pH和Ca2+浓度保持一个恒定值,降解3个月后含30 %和50 %CPPF的复合材料的弯曲强度分别能保持143、148 MPa。     

Analysis of Physical and Thermodynamic Properties of Poly(2-Phenyl-1,3-Dioxolane-4-Yl-Methyl-Methacrylate-Co-Styrene) Polymer with Inverse Gas Chromatography

In this study, physical and thermodynamic properties of poly(2-phenyl-1,3-dioxolane-4-yl-methyl-methacrylate-co-styrene) (PDMMA-ST) were investigated by using inverse gas chromatography. Two groups of solvents with different chemical natures and polarities were used to obtain information about PDMMA-ST-solvent interactions: alcohols and alkanes. The specific retention volume (V_g ⁰), the sorption enthalpy (ΔH₁ ^S), sorption free energy (ΔG₁ ^S), sorption entropy (ΔS₁ ^S), the weight fraction activity coefficients of solute probes at infinite dilution (Ω ₁ ^∞), and Flory-Huggins interaction parameters (χ ₁₂ ^∞) between polymer and solvents were determined for the interactions of PDMMA-ST with alcohols and alkanes by inverse gas chromatography in the temperature range of 333–473 K. Also, the solubility parameters of PDMMA-ST at infinite dilution were found by plotting the graph of [(δ ₁ ²/RT) - χ ₁₂ ^∞/V₁] versus solubility parameters, δ ₁, of probes.     

Heat Resistant and Mechanical Properties of Biodegradable Poly(Lactic Acid)/Poly(Butylene Succinate) Blends Crosslinked by Polyaryl Polymethylene Isocyanate

This work focus on improving the heat resistant and mechanical properties of poly(lactic acid)/poly(butylene succinate) (PLA/PBS) blends using appropriate contents of polyaryl polymethylene isocyanate (PAPI). Some crosslinked structures were formed according to the gel fraction and rheological results, and the crosslinked structures played the role of nucleation site for the blends. And the Vicat softening temperature of the blends gradually increased with increasing PAPI content. Moreover, the addition of PAPI in the PLA/PBS blends produced a few PLA-PBS copolymers which acted as a compatibilizer and enhanced the interfacial adhesion. Thus, the mechanical properties of PLA were significantly improved.     

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.     

凹凸棒石/聚乳酸纳米复合材料的力学性能和流变性能

采用熔融共混法制备凹凸棒石(ATT)质量分数分别为1%、3%和5%的ATT/聚乳酸(PLA)纳米复合材料,研究了ATT/PLA纳米复合材料的力学性能和流变性能。红外光谱分析结果表明:ATT与PLA基体之间存在较强的相互作用,使得二者之间具有较好的相容性。当ATT含量低于5%时,其可均匀分散在PLA基体中,而达到5%时,则会发生部分团聚。添加ATT后,PLA基体从脆性材料变为韧性材料,ATT起到增韧作用,并显著提高了复合材料的力学性能。当ATT含量为3%时,断裂伸长率达到26.36%,比纯PLA增加了297.6%,并且复合材料的冲击强度也比纯PLA增加了19.7%。ATT/PLA纳米复合材料的复数黏度、储能模量和损耗模量随ATT含量的增加呈先增大后减小趋势。由于ATT与PLA之间有良好的结合力,ATT的加入增大了复合材料的弹性和黏性,且低频区的变化明显高于高频区的变化。     

尼龙和聚酯短纤维的长度对其与天然橡胶氯丁橡胶复合材料性能的影响

本就尼龙，聚酯短纤维的长度对尼龙－天然橡胶以及聚酯－氯丁橡胶复合材料的物理性能和溶胀性能的影响进行了理论研究。实验结果表明：这两种短纤维橡胶复合材料的撕裂强度，２０％定伸应力随短纤维长度增加而增大，抗溶胀能力增强，拉伸强度则在短纤维最佳长径比条件下最好。尼龙，聚酯短纤维经Ｄ法预处理后，其复合材料的各基性能均有较大提高。     

超细滑石粉填充聚乳酸共混薄膜的制备及性能研究

采用双螺杆挤出共混法,将聚乳酸(PLA)、超细滑石粉(Talc)及乙酰柠檬酸三丁酯(ATBC)熔融共混制备生物降解粒料,并通过吹塑成型的方法制备了共混薄膜,研究了PLA共混薄膜材料的旋转扭矩、力学性能、稳定性及结晶形态。结果表明,随着超细Talc用量增加,PLA共混薄膜材料的旋转扭矩逐渐下降,拉伸强度和断裂伸长率均先增后降,直角撕裂强度基本不变;60℃体系增塑剂迁移率逐渐变小;125℃随Talc用量的增加,晶核数目增加、结晶速率增大且球晶尺寸变小。     

The Production of an Experimental Table Margarine Enriched with Conjugated Linoleic Acid (CLA): Physical Properties

Even though conjugated linoleic acid (CLA) is known to have some beneficial effects on the human body, its consumption has decreased over the past 20 years due to the replacement of animal fats by vegetable oils. In this study, using the structured lipid (SL) containing CLA, an experimental table margarine enriched with CLA was produced and stored for 3 months at two temperatures prior to performing the relevant analyses. The GC results showed that the margarine fat had 10.6% CLA. The solid fat content was the highest in week 0 in all samples, which then decreased during storage but the hardness increased. An increment in dropping point was also observed in the samples. In week 0, all the samples had the β′ crystal as the predominant crystal form but a crystal transformation from β′ to β was observed during storage.