Biodegradable materials have garnered significant attention due to their environmental friendliness and renewability. However, inadequate crystallization properties may occur during the molding process, affecting product appearance, mechanical properties, thermal stability, and shelf life, thereby limiting their industrial development and application. Nucleating agents, as crucial polymer additives, can significantly alter the crystallization behavior of polymer materials. This study provides an exhaustive review of the properties, impacts on material properties, and mechanisms of action of various nucleating agents. It also describes upcoming development trends and examines difficulties that arise in real-world applications. The goal is to provide more reference for researchers.

The crystallization control of poly(glycolic acid) (PGA) remains challenging due to the limited availability of effective nucleating agents. For the first time, this work found that N,N '-dicyclohexylterephthalamide (DCHT) could serve as a highly efficient nucleating agent for PGA and further self-assemble into different morphologies by changing the concentration and final heating temperature (T-f). At lower T-f of 250 degrees C, the crystallization of PGA is governed by self-nucleating effect due to the incompletely melted crystals, while at a higher T-f of 270 degrees C, the nucleating agent works and could self-assemble into dendritic, needle-like and agglomerates crystals depending on different DCHT concentrations (0.3 similar to 0.8 wt%). At the optimum concentration of 0.3 wt%, the dendritic crystals of DCHT could provide highly efficient nucleation sites inducing refining PGA spherulites; while at higher concentration of 0.5 wt%, the larger needle-like aggregates of DCHT results in lower nucleation efficiency and less effective refinement. As the concentration reaches 0.8 wt%, excessive DCHT cannot fully sublime and the crystal agglomerates creates an exceptionally high nucleation density, causing PGA crystallizes into numerous small spherulites. FTIR analysis confirms that the hydrogen-bonding interactions between DCHT and PGA govern this concentration-dependent self-assembly and the subsequent nucleation behavior. It also demonstrates that the addition of DCHT does not compromise the thermal stability of PGA. This study not only identifies DCHT as a novel and effective nucleating agent for PGA, but also elucidates its unique, concentration-dependent self-assembly mechanism, offering a practical strategy to tailor crystallization and develop high-performance PGA materials.

In this study, an inorganic multilayer barrier film was fabricated on the polyethylene naphthalate (PEN) substrate, which was composed of a SiO2 layer prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD) and a Al2O3/ZnO nanolaminate produced by plasma-enhanced atomic layer deposition (PEALD). The multilayer composite film with a structure of 50 nm SiO2 + (4.5 nm Al2O3/6 nm ZnO) × 4 has excellent optical transmittance (88.1%) and extremely low water vapor permeability (3.3 × 10−5 g/m2/day, 38 °C, 90% RH), indicating the cooperation of the two advanced film growth methods. The results suggest that the defects of the SiO2 layer prepared by ICP-CVD were effectively repaired by the PEALD layer, which has excellent defect coverage. And Al2O3/ZnO nanolaminates have advantages over single-layer Al2O3 due to their complex diffusion pathways. The multilayer barrier film offers potential for encapsulating organic electronic devices that require a longer lifespan.

We prepared polymer-based encapsulation films by plasma-enhanced atomic layer deposition (PEALD) of Al2O3 film on a polycarbonate (PC) substrate at 80-160 °C to fabricate Al2O3/PC barrier films. The thermal and dynamic mechanical properties of the PC substrate, the structural evolution of PEALD Al2O3 films, the optical transmission, surface morphology, and gas-barrier properties of Al2O3/PC film are all studied in this work as a function of temperature. The glass transition temperature Tg of the PC substrate is about 140 °C, and the coefficient of thermal expansion increases significantly when the temperature exceeds Tg. Increasing the deposition temperature from 80 to 160 °C for Al2O3 film deposited over 300 cycles increases the density from 3.24 to 3.45 g cm-3, decreases the thickness from 44 to 40 nm, and decreases the O/Al content ratio from 1.525 to 1.406. Al2O3/PC films deposited at 80-120 °C have no surface cracks, whereas surface cracks appear in samples deposited near or above 140 °C. Upon increasing the deposition temperature, the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of Al2O3/PC films decrease significantly at temperatures below Tg, and then increase at temperatures near to or above Tg due to cracks in the films. The optimal deposition temperature is 120 °C, and the minimum WVTR and OTR of Al2O3/PC film are 0.00132 g per (m2 24 h) and 0.11 cm3 per (m2 24 h 0.1 MPa), respectively. The gas-barrier properties of the Al2O3/PC films are attributed to both the densification of the Al2O3 film and the cracks, which are caused by the shrinkage of the PC substrate.

利用等离子体增强原子层沉积技术(PE-ALD)在涂覆聚丙烯酸酯多元醇树脂有机涂膜的 PET基底上沉积一层无机薄膜得到功能性 PET复合膜.通过水蒸气透过率测试仪和紫外可见近红外分光光度计研究了有机涂膜厚度、PE-ALD 镀膜种类和 PE-ALD 镀膜温度对 PET 复合膜水蒸气阻隔性和透光性能的影响.结果表明:聚丙烯酸酯多元醇有机涂膜厚度对 PET复合膜的水汽阻隔性和透光率基本无影响;PE-ALD 沉积的 Al2O3 薄膜可大幅提高 PET复合膜的水蒸气阻隔性,且 PE-ALD镀膜温度为 100℃时,水蒸气阻隔性能最优,可达 0.17g·m-2·d-1.

Biodegradable polyglycolic acid (PGA) shows great potential to substitute engineering petrochemical-based polymers because of its high mechanical strength, stiffness, and gas barrier. However, drawbacks such as low melt strength, poor thermal stability, and rapid degradation limited its practical applications. In this paper, PGA was modified by reactive extrusion using chain extender (CE) and anti-hydrolysis agent (AHA). The effects of the modification on the flow properties, melt viscosity and long-term hydrolysis behaviors of PGA were studied. Compared with the unmodified but one-pass processed PGA (C-PGA), the melt mass flow rate of modified PGA (M-PGA) decreased, while the complex viscosity (omega = 0.1 rad/s) dramatically increased, attributable to the realization of effective chain extension. The accelerated hydrolysis aging test indicated that the hydrolysis rate constant of C-PGA at 30 degrees C was 0.06183 day(-1), and that of M-PGA was 0.01332 day(-1), which exhibited a 78% reduction. Correspondingly, the service life of M-PGA was significantly prolonged. This may expand the potential applications of PGA, such as packaging film, agriculture, or textiles.

Biodegradable polyglycolic acid (PGA) has attracted wide interest as environmentally friendly polymer. However, poor melt properties and thermal instability limit its widespread applications, wherever processing technologies such as extrusion, blown film, thermoforming, are required. In order to enhance the melt strength of pure PGA material and enlarge its processing window, two reactive chain extenders (CEs), 4, 4 '-methylenebis (phenyl isocyanate) and styrene-acrylic multifunctional-epoxide oligomeric agent were incorporated concurrently into PGA using the twin-screw extruder. The PGA molecular structures were tailored by introducing CEs. Melt flow rate of the modified PGA gradually decreased with increasing CEs contents, due to chain extension. The shear rheology data showed a remarkable increase in modulus and complex viscosity together with longer relaxation time, which can be an indication of the existence of long chain branches in the molecular structure. Dynamic time sweep tests showed that the melt stability of the modified PGA improved significantly, with a loss of about 2% of the normalized storage modulus after 15 min, while the value of pure PGA was about 17%. Besides, changes of elongational melt properties can also be found, where strain hardening occurred for the modified PGA.

采用熔融共混和反应挤出技术制备聚乙醇酸/聚丁二酸丁二酯(PGA/PBS)共混物,研究PBS含量对PGA/PBS的热变形温度、拉伸性能、冲击性能、微观形貌以及结晶行为的影响.结果表明:随着PBS含量的增加,PGA/PBS热变形温度降低.当PBS添加量为20％,PBS在体系中分散均匀,分散相尺寸为纳米级,共混体系韧性明显增强.相比PGA,PGA/PBS的冲击强度从2.9 kJ/m2提高至8.7 kJ/m2,弯曲模量大于4000 MPa.而当PBS含量升至30％和40％,PBS出现熔融合并,逐渐呈现双连续相,导致弯曲模量和断裂伸长率明显下降.

在低温80℃的沉积条件下,采用等离子体增强原子层沉积(PEALD)技术在柔性聚对苯二甲酸乙二醇酯(PET)基底上制备氧化铝(Al2O3)阻隔薄膜.通过X射线光电子能谱、椭圆偏振仪测试分析表明,制备的Al2O3薄膜纯度较高,均匀性好.同时,通过调节沉积循环周期制备了不同厚度的Al2O3薄膜,研究了薄膜厚度对其表面形貌、表面粗糙度、透光率以及水汽透过率的影响.结果表明,沉积循环周期为500cycles时制备的Al2O3薄膜性能最为优异,表面粗糙度为1.52nm,400～1200nm波长范围内平均透光率为90.4％,水汽透过率为3.15×10-3g·m-2·d-1.

将受阻酚类抗氧剂4,4'-硫代双(6-叔丁基间甲酚)与低密度聚乙烯(LDPE)、交联剂DCP(过氧化二异丙苯)进行熔融共混,制备了一系列不同抗氧剂含量的交联聚乙烯(XLPE).研究了抗氧剂含量对XLPE交联过程、凝胶含量、氧化诱导期(OIT)、热老化前后力学性能及热延伸特性的影响.研究结果表明,添加抗氧剂可以延迟交联反应,降低XLPE的交联度,提高材料的氧化诱导期及热老化后的拉伸强度,使材料的热延伸性能增加.与无抗氧剂的样品相比,当抗氧剂含量为0.3％时,XLPE起始交联反应温度从155.2℃延迟至160.3℃,OIT由2 min延长至40 min;当抗氧剂含量从0增加到0.8％时,XLPE交联度由90％降至76.4％;热延伸伸长率由40％增大至131％.

Biodegradable polyglycolic acid (PGA) has been attracting much attention recently. However, poor melt strength and thermal stability limit the processing of PGA by methods such as film blowing and injection molding. To improve melt strength and thermal stability, two reactive chain extenders, styrene-acrylonitrile-glycidyl methacrylate terpolymer (poly(St-AN-GMA)) and 4, 4 '-methylenebis(phenyl isocyanate) (MDI), were incorporated respectively into PGA using twin-screw extrusion. MDI was found to be more effective in chain extension and enhancing thermal stability than poly(St-AN-GMA). The T-5% (the temperature where the remaining weight percentage is 95%) of PGA modified with 3 wt% MDI increased to 334.5 degrees C from 310.8 degrees C for pure PGA. Melt flow rate for the same materials decreased from 47.2 g/10 min to 13 g/10 min. The activation energy of thermal degradations for MDI-modified PGA was twice that of the unmodified PGA as evaluated by the Flynn-Wall-Ozawa method.

在柔性产业的引领下,柔性超高阻隔膜由于可以使器件免受水汽侵蚀,延长使用寿命,广泛应用于有机发光二极管(OLED)柔性面板、量子点显示、柔性光伏等行业.原子层沉积(ALD)技术是一种原子尺度的薄膜制备技术,沉积的薄膜均匀性好、纯度高、而且厚度精确可控,是超高阻隔膜的理想制备方法.本文总结了ALD的基本原理,技术特点和沉积条件等.重点阐述了ALD技术制备单层、多层无机阻隔薄膜,以及有机/无机叠层阻隔薄膜的国内外研究进展及阻隔机理.同时提出有机/无机叠层结构是实现阻隔膜超低水汽透过率的有效手段.最后指出了原子层沉积技术制备柔性超高阻隔膜的未来发展趋势.

In the present work, the biodegradable blends of poly(glycolic acid) (PGA) and poly(butylene adipate-co-terephthalate) (PBAT) with in situ compatibilization using 4,4 '-methylenebis(phenyl isocyanate) (MDI) were prepared. The combined results of FTIR, DSC, SEM, DSC, POM, TGA and rheology demonstrated that the MDI was successfully reacted with PGA/PBAT, the complex viscosity and storage moduli (G ') of the blends were increased. Melt elasticity and viscosity of the blends were also increased on increasing the concentration of PBAT. SEM results indicated that the compatibility was improved by in situ compatibilization. Due to the apparent differences in melting temperature (T-m) between PGA and PBAT, the morphology of the dispersed phase evolved from a spherical structure to in situ microfiber when the content of PBAT was up to 60% during injection molding. The interfacial adhesion between PGA and PBAT was strengthened, consequently, the impact strength of the blend was sharply increased from 9.0 kJ m(-2) to 22.2 kJ m(-2). On account of the chain extension effect, the crystallinity, crystallization temperature and crystallization size were decreased, which was also of benefit for the improvement of toughness. Meanwhile, the thermal stability of the PGA was improved through blending with PBAT. A novel biodegradable blending material with enhanced toughness and thermal stability was prepared.

通过熔融共混方法,采用环氧类扩链剂对聚乙醇酸(PGA)进行反应挤出改性,同时添加亚磷酸酯类抗氧剂来降低熔融加工过程中的热降解.研究了扩链剂与抗氧剂联用对PGA熔体质量流动速率、热稳定性、熔体流变性能以及抗水解性能的影响.结果表明,扩链剂与抗氧剂复配,PGA改性料的熔体质量流动速率由原料的44.2 g/10min下降至11.2 g/10min;起始分解温度T-5％(质量剩余95％的温度点)提高22.1℃;熔体黏度提高6倍以上;在提高了熔体强度的同时,改性料热稳定性明显改善,同时抗水解稳定性也有一定程度提高.

Crosslinked high-density polyethylene (XL-HDPE) is a preferred material for chemical and fuel tanks due to its superior environmental stress crack resistance and impact strength. The impact performance of rotationally molded specimen is important for final products. In the research the drop weight impact strength (defined as ARM impact strength) of rotationally molded XL-HDPE is tested between -40 degrees C and 25 degrees C. The crosslinking content, crystallization characteristics, and dynamic mechanical properties (DMA) of different thickness gradients are examined to illustrate the relationships between the impact strength, brittle-ductile transition (BDT) and microstructures. The innermost surface layer (about 0.3 mm) has lower gel content, higher crystallinity, and average lamellar thickness compared with the body part. The ARM impact strength is about 1 J/mm at -40 degrees C and -30 degrees C, and about 29 J/mm at -20 degrees C similar to 25 degrees C. There is a BDT between -30 degrees C and - 20 degrees C. After removing the innermost surface layer, the sample breaks in ductile manner in the entire tested temperature range, and the ARM impact strength is about 24 similar to 26 J/mm. The DMA results show that the BDT is consistent with the structure transition of the innermost surface layer. The microstructures of rotationally molded XL-HDPE in the innermost surface layer dominate the low temperature impact performance.

利用过氧化物作为交联剂对高密度聚乙烯(HDPE)进行微交联改性,研究了交联剂含量对HDPE的动态流变与熔体拉伸流变行为的影响,并在此基础上探讨了HDPE的不同相对分子质量和其分布对微交联聚乙烯流变行为的影响.实验结果表明:随着交联剂含量的升高,HDPE 8007(H2)的相对分子质量和长支链含量均随之提高,聚合物的复数黏度(η*)提高70倍,松弛时间(τ)提高了63倍,拉伸黏度提高16倍.对于不同相对分子质量和分子量分布的HDPE,交联剂对于低重均分子量(Mw)且窄分子量分布的HDPE 2911(H1)的交联效果更加显著,在交联剂含量为0.15％时,H1-0.15％的η*、τ和拉伸黏度均高于H2-0.15％,能表现出更好的熔体增强效果.

AbstractThree kinds of ethylene‐octene copolymers (POE) were melt‐blended with high‐density polyethylene (PE‐HD) in different proportions. Detailed characterizations were conducted to analyze their structural differences of POE and its effects in toughening PE‐HD. The higher molecular weight POE can improve the toughness of PE‐HD. 60:40 PE‐HD/POE is elongated to break up to 700% while impact strength is 84.7 kJ/m2 at −30°C, which is 21‐fold of PE‐HD. In the brittle to ductile transition (BDT) during impact, the fracture mechanism changes from the crazing mode to the shear yield‐plastic deformation mode. The BDT temperature decreases as the POE molecular weight and its content increase. The interface strength in tension is estimated to access their effects. The Boltzmann‐type models were successfully extended to describe the typical S‐shaped curves in BDT of notched impact strength vs POE content or temperature. The supplementary decay model is suggested for the attenuation in toughening. Transition map in impact is proposed to select the use range of composition (c) and temperature (T) for high toughness. The curves are converted into 3D graph of T‐c‐impact strength for illustrating their coupling‐separate effects, and further into the contour map of impact strength in T‐c space for finding their partial equivalence.

Three kinds of ethylene-octene copolymers (POE) were melt-blended with high-density polyethylene (PE-HD) in different proportions. Detailed characterizations were conducted to analyze their structural differences of POE and its effects in toughening PE-HD. The higher molecular weight POE can improve the toughness of PE-HD. 60:40 PE-HD/POE is elongated to break up to 700% while impact strength is 84.7 kJ/m(2)at -30 degrees C, which is 21-fold of PE-HD. In the brittle to ductile transition (BDT) during impact, the fracture mechanism changes from the crazing mode to the shear yield-plastic deformation mode. The BDT temperature decreases as the POE molecular weight and its content increase. The interface strength in tension is estimated to access their effects. The Boltzmann-type models were successfully extended to describe the typical S-shaped curves in BDT of notched impact strength vs POE content or temperature. The supplementary decay model is suggested for the attenuation in toughening. Transition map in impact is proposed to select the use range of composition (c) and temperature (T) for high toughness. The curves are converted into 3D graph ofT-c-impact strength for illustrating their coupling-separate effects, and further into the contour map of impact strength inT-cspace for finding their partial equivalence.

利用十溴二苯乙烷(DBDPE)与三氧化二锑(Sb2O3)组成的卤锑阻燃剂对交联聚乙烯进行阻燃改性,研究了阻燃剂含量对交联聚乙烯材料阻燃性能的影响,材料含22.5％ DBDPE和7.5％Sb2O3在UL94阻燃测试达到Ⅴ-0等级.通过体系树脂熔体流动性的优化,可改善高填充量阻燃剂时材料的滚塑加工性能.实验室制备了滚塑用Ⅴ-0级阻燃交联聚乙烯,并测试了材料的机械性能包括拉伸强度、弯曲模量和缺口冲击强度等.所制材料缺口冲击强度达到43 kJ/m2.SEM和EDS表征显示阻燃剂在体系内分散较均匀.

制备了不同交联剂含量的交联聚乙烯(XLPE)材料及滚塑制品,比较了交联母料不同稀释比例下所得材料的流变特性、交联行为,研究了交联剂含量对样品力学性能(弯曲强度、缺口冲击强度)、不同温度时的落锤冲击强度以及厚度梯度方向的晶体尺寸、结晶度以及交联度等微观结构的影响.结果显示:随交联母料稀释比增大,交联反应略有延迟、交联反应程度降低,制品结晶度增加、缺口冲击强度降低、弯曲模量升高;交联母料稀释比在1:6～1:12时,测试温度25℃时样品落锤冲击强度均为25 J/mm以上,测试温度由25℃逐步下降至-40℃时,交联剂含量高的滚塑样品(M1-6)的落锤冲击强度可保持25 J/mm以上,稀释比例较大的滚塑样品出现韧性-脆性转变(-40℃落锤冲击为1 J/mm).