Brittle-ductile transition of particle toughened polymers: influence of the matrix properties

It was theoretically pointed out that the product of the yield stress and yield strain of matrix polymer that determined the brittle-ductile transition (BDT) of particle toughened polymers. For given particle and test condition, the higher the product of the yield stress and the yield strain of the matrix polymer, the smaller the critical interparticle distance (ID_c) of the blends was. This was why the ID_c (0.15 μm) of the polypropylene (PP)/rubber blends was smaller than that (0.30 μm) of the nylon 66/rubber blends, and the ID_c of the nylon 66/rubber blends was smaller than that (0.60 μm) of the high density polyethylene (HDPE)/rubber blends.     

纳米级CaCO3填充HDPE复合材料的研制

研究了纳米级ＣａＣＯ３填充ＨＤＰＥ体系的力学性能和流变性能,发现这种填充体系的脆韧变消失,且具有良好的加工性能和优良和综合性能。     

Polyethylene toughened by caco3 particles—percolation model of brittle-ductile transition in hdpe/caco3 blends

The percolation model is used to interpret the brittle-ductile transition of HDPE/CaCO₃ blends. The percolation threshold (θ_sc) for HDPE/CaCO₃ blends is found to be 0.52, which is equal to π/6. The critical exponent (g) is found to be 0.83 for HDPE/CaCO₃ blends. The toughening efficiency of blends which have monodisperse, highly asymmetrical particles, strong interphase adhesion and high matrix toughness is greater. The brittle-ductile transition in polymer blends seems to be a universal percolation phenomenon.     

Polyethylene toughened by rigid inorganic particles

High density polyethylene (HDPE) is toughened by particles of rigid inorganic filler CaCO₃, which is treated with phosphate. The stress-strain curve of the HDPE/modified-CaCO₃ (80/20) composite covers a greater area than that of HDPE, and the impact strength of HDPE is greatly improved by modified CaCO₃ from 230 J/m to 580 J/m as CaCO₃ content is increased to 50 wt%. Morphological observation indicates a finer dispersion of the modified-CaCO₃ particles and a large plastic deformation of HDPE. The cavitation and stress field interaction around the particles are considered to explain the toughening mechanism.     

Brittle-ductile transition of polymer blends

Based on the Ludwik-Davidenkov-Orowan theory, a new criterion of BDT for polymer blends is proposed. In this approach fracture stress (_b) and shear yielding stress (_y) governing the brittle-ductile transition (BDT) of polymer blends is combined into a dimensionless group as D_a = _b ²/_y ². The theory dictates that BDT occurs at a critical condition D_ac = 1, brittle fracture occurs when D_a < 1, and ductile fracture occurs when D_a > 1. It can be shown that D_a = F_g · L_ym/L_D, where L_ym measures the length of shear band of the matrix, L_D is a parameter determined by the morphology and interfacial adhesion of dispersed phase, and F_g is related to specimen geometry and other extrinsic parameters. It is suggested that the onset of BDT depends on the competition between the L_ym and L_D. With due consideration to blend morphology, interfacial adhesion and matrix properties, existing experimental evidence supports the applicability of the proposed criterion.The project supported by FORD and NSFC No. 09415312     

Studies on fast functionalization of HDPE by ultraviolet irradiation and functionalized HDPE/CaCO3 composites

High density polyethylene (HDPE) was functionalized quickly by ultraviolet irradiated in ozone atmosphere. The oxygen-containing groups in the functionalized HDPE were C=O and C–O, and their content increased with increasing the irradiation time. The molecular weight of the functionalized HDPE decreased and its distribution became wider with increasing the irradiation time. The gel was not found in the functionalized HDPE. Compared with those of HDPE, the melting temperature and crystallinity of the functionalized HDPE decreased. With increasing the irradiation time, the hydrophilicity of the functionalized HDPE was enhanced, while its temperature of thermal decomposition decreased. The functionalized HDPE/CaCO₃ composites were prepared. Compared with those of HDPE/CaCO₃ composites, the compatibility and dispersion of the functionalized HDPE/CaCO₃ composites were enhanced observably. The tensile strength and notch impact strength of the functionalized HDPE/CaCO₃ composites increased with increasing the irradiation time.     

Effect of cavitations on brittle-ductile transition of particle toughened thermoplastics

In this study, we established a correlation between cavitations volume and the brittle-ductile transition (BDT) for particle toughened thermoplastics. The brittle-ductile transition temperature (T_BD) was calculated as a function of T^∗ and interparticle distance (ID), respectively, where T^∗ was a parameter related to the volume of cavitations. The results showed that the smaller the cavitations volume, the higher the brittle-ductile transition temperature. The calculations correlated well with the experimental data. With respect to rubber particle, the rigid particle was too hard to be voided during deformation, thereby the T_BD of the blend was much higher than that of rubber particle toughened thermoplastic. This was a main reason that rubber particle could toughen thermoplastics effectively, whereas rigid particle could not.     

HDPE/CaCO3纳米复合材料的制备及性能

通过熔融共混法制备HDPE/纳米CaCO3复合材料,并通过TEM观察复合材料的微观结构.结果表明:纳米CaCO3基本以纳米级均匀分散在HDPE基体中,HDPE/纳米CaCO3复合材料的熔体指数比纯HDPE有所下降,并且当纳米CaCO3含量为5份时,复合材料的冲击强度提高约26.2%;而纳米CaCO3含量为3份时,复合材料的拉伸强度提高约2%,同时热分解温度比纯HDPE提高了49.8℃;热失重残余量在纳米CaCO3含量为8份时提高到了6.98%.     

Mechanical properties and interfacial interaction of CaCO3 filled HDPE compatibilized with HDPE functionalized by ultraviolet irradiation

The mechanical properties of CaCO₃ filled high density polyethylene (HDPE) compatibilized with ultraviolet (UV) irradiated HDPE (uHDPE) were studied and the interfacial interactions between CaCO₃ and the polymers were evaluated by SEM, the Molau test, and ESCA. UV irradiation in air introduces the following functional groups on HDPE: >COOH, >C?O, ? OOH and ? OH. The concentration of these groups increases with irradiation time. The addition of a small amount (<10% by wt) of uHDPE to the HDPE/CaCO₃ improves the tensile and impact strength. For example, the addition of 3% HDPE irradiated for 500 hours (u500HDPE) increases the tensile and impact strength of HDPE/CaCO₃ from 16.7 MPa and 210 J/m to 25.2 MPa and 430 J/m, respectively. Chemical reactions between uHDPE and CaCO₃ promote interactions between HDPE and CaCO₃. The morphology of the compatibilized compound is nearly homogenous, and no CaCO₃ sediment was observed in a hot xylene solution of HDPE/u500HDPE/CaCO₃ when the content of u500HDPE exceeded 30% (wt).     

HDPE／CaCO3复合材料片材制品的力学性能

通过制备不同含量的微米级和纳米级碳酸钙(CaCO3)填充的高密度聚乙烯(HDPE)片材制品,对其力学性能进行分析。研究了微米级和纳米级CaCO3对HDPECaCO3复合材料片材制品的力学性能的影响规律,并对此影响规律进行了合理的解释。     

HDPE/POE/CaCO3三元体系薄膜研究

采用聚烯烃弹性体（POE）和重质碳酸钙对HDPE薄膜进行改性,研究了POE和重质碳酸钙的用量对共混体系薄膜力学性能、流变性能的影响。结果表明,POE的加入,使HDPE／POE薄膜的单位落镖冲击破损质量增加,而拉伸强度则有所下降。当POE的质量分数为10％时,薄膜的单位落镖冲击破损质量提高了51．1％,但薄膜的拉伸强度下降了20．5％。在HDPE／POE／CaC03体系中,当POE、重质碳酸钙的质量分数分别为10％和5％时,薄膜的单位落镖冲击强度比纯HDPE提高95．6％,且拉伸强度不降低。     

HDPE/UHMWPE/CaCO3复合材料流变学行为研究

利用高级流变扩展系统仪(ARES)分别对碳酸钙(CaCO3)填充高密度聚乙烯(HDPE),碳酸钙填充高密度聚乙烯(HDPE)/超高摩尔质量聚乙烯(UHMWPE)复合材料的流变学行为进行了研究.结果表明,不同的加工条件下,CaCO3对HDPE流变行为基本没有影响,而对HDPE/UHMWPE复合体系影响明显.随着转矩流变仪剪切速率的提高,HDPE/UHMWPE/CaCO3三元复合体系融体黏弹性参数发生改变.其中低频储能模量(G′)、损耗模量(G″)和零切黏度(η0)逐渐升高,损耗因子(tanδ)逐渐降低,表明体系融体流变行为由liquid-like行为向solid-like 行为转变,融体分子链作用加强.加工条件的改变引起了融体结构的转变,从而导致等温结晶过程加快.熔体黏弹性转变与CaCO3刚性颗粒与UHMWPE颗粒之间的相互作用密切相关.     

滑石粉及CaCO3对HDPE的共复合研究

在反应性偶联剂及助偶联剂存在下,将CaCO3或滑石粉对高密度聚乙烯（HDPE）进行复合时,随复合粉体含量的增加,CaCO3复合体系表现为拉伸强度下降但冲击强度大幅度增加,滑石粉复合体系则表现为拉伸强度有较大的增加但冲击强度有较大的下降;将滑石粉和CaCO3进行共复合时,可以同时发挥片状滑石粉的增强作用和近球状CaCO3的增韧作用,得到综合力学性能较好的复合材料,但其配合比、粉体总添加量及助偶联剂添加量将对体系的力学性能产生较大的影响;各体系冲击断面的扫描电子显微镜照片所显示的微观形状和其力学物性有较好的对应,证明在共复合体系中,CaCO3既能通过偶联剂及助偶联剂的作用对HDPE产生较好的增韧效果,又能对滑石粉的分散起到一定的促进作用,使体系的拉伸强度有所提高。     

母料法制备HDPE/POE/CaCO3薄膜的性能研究

采用母料法(二次挤出法)制备HDPF/POE/CaCO3共混物薄膜.比较了母料法与一次挤出法制得薄膜的力学性能与透光率.结果表明,在工艺参数相同时,母料法制备的薄膜力学性能比一次挤出法要好,而薄膜透光率基本相同.当POE、重质碳酸钙质量分数均为10%时,母料法制备的薄膜拉伸强度、断裂伸长率、单位冲击破损质量比纯HDPE薄膜分别提高了24.8%、27.5%、121%,比二次挤出法制备的薄膜力学性能分别提高了36.8%、14.1%、52.5%.     

振动力场下HDPE/CaCO3复合材料的拉伸性能

使用电磁动态塑化挤出机,对HDPE／CaCO,复合材料的挤出片材做横向和纵向拉伸性能研究。振动力场能够有效地改善HDPE／CaCO,片材的拉伸强度和拉伸断裂伸长率,在本实验范围内,与稳态挤出制品相比,片材的横向和纵向拉伸强度分别提高了16．4％和15．6％,横向和纵向拉伸断裂伸长率分别提高了38．9％和44．0％;振动对材料横向的影响比对纵向更具有规律性。     

Toughening and reinforcement of HDPE/CaCO3 blends by interfacial modification—interfacial interaction

To improve the mechanical properties and structure of HDPE/CaCO₃ composites, a type of modifier, consisting mainly of carboxylated polyethylene (CPE), and a type of CaCO₃ grafted with acrylamide (CaCO₃(SINGLE BOND)A) were used. The carboxyl group content of CPE was from 1 to 10%. The amide group content on the surface of the modified CaCO₃ was from 0.2 to 1.8%. The interfacial structure and interaction of ternary blends of HDPE, CPE, and CaCO₃(SINGLE BOND)A were studied. The results indicate that the higher the amide group content and the carboxyl group content, the higher the tensile and impact strength. This behavior has been attributed to a series of chemical and physico-chemical interactions taking place between the two components during the blending process which were confirmed by FTIR and extraction experiments. The improvement of interfacial adhesion by the CPE and CaCO₃(SINGLE BOND)A was also clearly revealed in the SEM of the fracture surface. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1275–1281, 1997     

相容剂的制备及其在纳米碳酸钙填充高密度聚乙烯中的应用

通过熔融接枝的方法制备了高分子型界面相容剂HDPE-g-MAH，并将其应用于HDPE／CaCO3填充体系，考查了HDPE-g-MAH对HDPE／CaCO3填充体系的增容效果和增容机理。结果显示，HDPE-g-MAH有效提高了HDPE／CaCO3两相组分的界面黏结，使复合材料的力学性能有明显的改善。     

HDPE/LLDPE/CaCO3共混物注射成型收缩率的研究

研究了高密度聚乙烯（HDPE）／线性低密度聚乙烯（LLDPE）共混物及其碳酸钙（CaCO3）填充体系的注射成型收缩率,分别用示差扫描量热仪（DSC）和AR2000高级流变仪分析测定了共混物的结晶度和熔体黏度,并探讨了不同配比下共混物结晶度和熔体黏度与成型收缩率的关系。结果表明,在加工条件不变的情况下,HDPE／LLDPE共混物成型收缩率受结晶度和熔体黏度的显著影响。随LLDPE用量的增加,收缩率的变化明显分为三个阶段,先迅速增大,然后变化减缓,最后又逐渐减小。加入少量铝酸酯活化的CaCO3可以显著降低共混物的成型收缩率。     

纳米CaCO3增强增韧聚乙烯母粒的开发与应用

介绍了一种将纳米CaCO3填充到低密度聚乙烯中制成母粒,并应用到节水滴灌PE输水软管中的工艺.实验证明:纳米CaCO3对PE输水软管有着明显的增韧增强效果,当其添加量达到8%(质量分数)时,PE输水软管的缺口冲击强度、拉伸强度与断裂伸长率分别达到最大值:58.9 kJ/m2,43.62 MPa和824.8%,并且加工时可使树脂的流动速率增加,显著提高生产效率,降低生产成本,有很强的现实意义.     

针状纳米级碳酸钙工业制备新工艺

在复合结晶导向剂存在条件下，在碳化温度30～75℃、氢氧化钙初始质量分数8％～12％的高温高浓的工艺条件下，制备出了直径为20nm、长径比为10～15、粒径分布均匀的针状纳米碳酸钙。同时研究了结晶导向剂加入量、碳化温度、氢氧化钙初始浓度等对针状纳米碳酸钙的粒径和形貌的影响，并进行了工业化试验，取得良好结果。