Influence ofβ-nucleating Compound Agents on the Mechanical Properties and Crystallization Behavior of Polypropylene Random Copolymer

A novel polypropylene random(PPR)composite materials with optimized properties was developed by addingβ-nucleating compound agents(rare earth complex WBG-2 and aryl amide derivative TMB-5)and ternary compound modifier(TPE/WBG-2/CaCO_(3)).The effects of differentβ-nucleating agents and ternary compound modifier on the mechanical properties and crystallization behavior of PPR were analyzed.The results show that,compared with pure PPR materials,both WBG-2 and TMB-5 could significantly improve the impact strength of PPR.The crystallization temperature of PPR increased with the addition ofβ-nucleating agent.The modified PPR prepared with ternary compound modifier showed the most excellent comprehensive properties.

CRYSTALLIZATION KINETICS OF ETHYLENE-PROPYLENE COPOLYMERS PREPARED BY LIVING COORDINATION POLYMERIZATION

In this paper,crystallization kinetics of a series of ethylene-propylene copolymers prepared by living polymerization coordination catalyzed by a fluorinated bis(phenoxyimine)Ti catalyst(FI-EP copolymers)was studied,and was compared with that of ethylene-propylene copolymers prepared by a conventional Ziegler-Natta catalyst(ZN-EP copolymers).It is found that,the Avrami exponent and the crystallization rate constant of the FI-EP and ZN-EP copolymer show similar dependence on crystallization temperature,but t...

Rapid synthesis of biodegradable poly(epsilon-caprolactone-co-p-dioxanone) random copolymers under microwave irradiation

Biodegradable poly(epsilon-caprolactone-co-p-dioxanone)(PCDO) random copolymers have been synthesized by ring-opening polymerization of epsilon-caprolactone(CL) and p-dioxanone(PDO) under microwave irradiation.The effects of irradiation time and different CL/PDO molar feed ratios on the microwave-assisted ring-opening polymerization(MROP) of PCDO have been discussed.The resultant products were characterized by ~1H NMR,GPC and DSC.It was found that the polymerization was completed within 20 min at 140℃.In th...

Critical Role of Ethylene-Propylene Block Copolymer in Impact Polypropylene Copolymer

Ethylene-propylene block copolymer(EbP) is a vital component in impact polypropylene copolymer(IPC), yet its distribution in the multiphase composite material and how it influences the phase structure and the mechanical properties are not well understood. In this work,four IPCs were investigated by atomic force microscopy-infrared(AFM-IR) to assess the phase compositions in situ, based on which in conjunction with the chain microstructure information obtained ex situ the distributions of the copolymer components were derived for each alloy. For the IPCs whose EbP comprises long P and long E segments, the EbP fraction was found to phase separate from the rubber and the PP matrix to form the cores of the disperse particles with the E-P segmented copolymer(EsP). In contrast, in the IPC with EbP composed of long P and short E segments, the EbP fraction formed an outer shell for the rubber particles with the cores comprising the EsP alone, and this IPC, containing a lower E comonomer content than its counterpart, exhibited both better impact resistance and higher flexural modulus. These results clarify how the chain structure of EbP governs the phase morphology in IPC, which in turn impacts the properties of the composite material.

QUANTITATIVE EVALUATION OF ARRANGEMENT OF MONOMERS IN LINEAR BINARY COPOLYMERS USING A MONTE CARLO SIMULATION METHOD

A Monte Carlo method was used to take thorough account of the influences of different reactivity ratios and initial feed compositions on copolymer microstructure.The model proves the lack of azeotropic behavior in systems in which r_A>1 and r_B<1 or vice versa;it is also able to calculate the drift in the copolymer properties:copolymer composition,and randomness parameter.Moreover,for each reactivity ratio pair given,there is a unique reaction conversion,at which macromolecules produced inherit their ...

Synthesis and Characterization of Poly(L-lactide-co-ε-caprolactone) Copolymers

A series of random and block poly（ L-lactide-co-e-caprolactone ） （ PCLA ） copolymers whh different composition are prepared using stannous octaoate as catalyst.The effects of the amount of initiator on the intrinsic viscosity have been investigated. The structure of the PCLA copolymers is characterized by means of nuclear magnetic resonance（ NMR ）, Fourier transform infrared spectrum （ FTIR ）, differential scanning calorimetry （ DSC ） and X- ray diffraction （ XRD ） methods. It is shown that the synthesis condition and the composition of copolymers obrious influence on the structure of PCLA copolymers. Hydrolytic degradation of the copolymers in a PBS solution of pH 7.4 at 37.0℃ shows that the copolymers of different composhions degrade at different rates.

聚苯基硅氧烷微球对聚丙烯结构与性能的影响

以无规共聚聚丙烯(PPR)树脂为基体,聚苯基硅氧烷微球(PPSQ)为改性剂,采用注塑成型工艺制备PPSQ/PPR复合材料。通过傅里叶变换红外光谱(FTIR)、差示扫描量热法(DSC)、扫描电镜(SEM)等表征技术,考察PPSQ微球对PPSQ/PPR复合材料化学组成、力学性能、耐热性能、熔融行为及微观结构的影响。结果表明,当PPSQ改性剂添加量为6%时,相较于纯PPR,复合材料弯曲模量提高14.08%、冲击强度降低0.80%、热变形温度提高7.80℃以及结晶度提高8.70%。PPSQ微球可在不基本影响PPR冲击性能基础上,有效改善PPR的耐热性能和刚性。

无规共聚聚丙烯管材料的微观结构研究

研究了四种无规共聚聚丙烯(PPR)管材料的熔融结晶性能、非等温结晶行为、等规聚丙烯链段分布、结晶形貌,确认了α晶型与γ晶型的存在。结果表明:PPR-1的乙烯含量为4.2wt%,分子量分布(Mw/Mn)为最宽,γ晶型含量为57.6wt%,含有成核剂,结晶较为细密;PPR-2的乙烯含量为3.9wt%,重均分子量(Mw)为最高,γ晶型含量为47.9wt%,含有成核剂,结晶最为细密;PPR-3的乙烯含量为3.6wt%,长等规聚丙烯链段含量最高,γ晶型含量为14.7wt%,不含成核剂;PPR-4的乙烯含量为4.0wt%,γ晶型含量为16.7wt%,不含成核剂。它们具有相近的力学性能;聚丙烯工艺路线、乙烯含量和成核剂等是造成微观结构差异的关键因素。

Engineering Antibacterial Activities and Biocompatibility of Hyperbranched Lysine-based Random Copolymers

Antimicrobial peptides(AMPs)have been considered as an alternative to small molecule antibiotics since they are difficult to develop antimicrobial resistance.Hyperbranched polylysine(HPL),an AMP mimics,has gained attention due to its broad-spectrum antibacterial activities,but it also suffers from high toxicity.Here we report a facile strategy to engineer the toxicity of HPL by copolymerizing lysine(K)with a hydrophobic amino acid,e.g.,alanine(A),tryptophan(W)or phenylalanine(F),to afford hyperbranched random copolymers.These copolymers have comparable antibacterial activities to HPL while their cytotoxicities and in vivo toxicities are lowered when the type and content of hydrophobic amino acid and the size of copolymers are optimized.The G.mellonella infection model demonstrates that the copolymers are effective against the S.aureus infection in vivo.The copolymers kill the bacteria through the disruption of cell membranes and the bacteria do not develop resistance to the copolymers.

Micelle-crosslinked hydrogels with stretchable,self-healing,and selectively adhesive properties:Random copolymers work as dynamic yet self-sorting domains

The design of crosslinking domains is a vital factor to create functional hydrogels with controlled physical,mechanical,and adhesive properties.This paper demonstrates versatile synthetic systems of micelle-crosslinked hydrogels with highly stretchable,self-healing,and selectively adhesive properties.For this,methacrylate-bearing random copolymer micelles are designed as physical and covalent crosslink domains via the self-assembly of amphiphilic random copolymers carrying hydrophilic poly(ethylene glycol)(PEG),hydrophobic butyl or dodecyl groups,and methacrylate-terminal PEG in water.The size,aggregation number,and pendant methacrylate number of the micelles are controlled by the composition and degree of polymerization.Hydrogels are efficiently obtained from the free radical polymerization of hydrophilic monomers such as PEG acrylate and acrylamide in the presence of the micelle crosslinkers in water.Owing to the dynamic yet selective chain exchange properties of the micelle domains,the hydrogels are highly stretchable up to over 1000%and show self-healing and selectively adhesive properties.The self-healing of hydrogels is promoted upon heating due to the fast chain exchange of the micelle domains,whereas hydrogels consisting of micelles with different alkyl groups are never adhesive because of their self-sorting properties.

无规共聚聚丙烯的非等温结晶动力学研究

研究了无规共聚聚丙烯(PPR)在不同降温速率下的非等温结晶行为,采用Jeziorny法、Ozawa法和莫志深法等模型分析了PPR的非等温结晶动力学。模拟结果表明,加入α成核剂的PPR力学性能优异,具有更高的结晶温度和结晶度;Jeziorny法和莫志深法的分析结果表明,加入α成核剂的PPR表现出更快的结晶速率,且两种不同的α成核剂对PPR结晶性能的改善效果相近;利用Kissinger公式计算PPR的非等温结晶活化能的结果表明,α成核剂改性的PPR具有较高的非等温结晶活化能;加入α成核剂可使PPR形成更小的球晶。

阳离子型抗静电剂的合成及其性能

针对PET材料的静电积聚问题,合成了无规共聚物结构的非离子与阳离子型抗静电剂,重点考察了阳离子型抗静电剂中的季铵盐组分对抗静电剂的热学性能、抗静电性能的影响,以及阳离子型抗静电剂的含量对PET基体的抗静电性能、表面亲水性能以及力学性能的影响。结果表明:阳离子型抗静电剂的热稳定性不如非离子型抗静电剂;阳离子型抗静电剂的抗静电效果优于非离子型抗静电剂,当季铵盐的添加量为14%时,阳离子型抗静电剂的抗静电效果相对最优;当阳离子型抗静电剂质量分数达到20%时,PET注塑样品的表面电阻率下降了4个数量级,表面接触角下降了63.03%,抗静电性能以及表面亲水性能得到显著提高,但力学性能有所下降。

Mechanism of Polymorph Selection during Crystallization of Random Butene-1/Ethylene Copolymer

Starting from an initial sample of butene-1/ethylene copolymer with stable form I＇, we examined the nucleation of different crystalline polymorphs （here metastable form II and stable form I＇） at different isothermal crystallization temperatures after being melted at different melt temperature （Tmelt）. When Tmelt was just above the melting temperature （Tm） of the crystallites, self-seeding took place. There, residue crystallites served as nuclei leading to the crystallization of the same crystalline phase. When Tmelt was a few degrees above the Tin, self-seeding was disabled due to complete melting of the initial crystals. Upon crystallization, the selection of the different polymorphs in this random copolymer was found to depend on an interplay between the domain size of segregated long crystallizable sequences and the size and energy barrier of the critical nucleus of the respective crystalline forms. Our results provide a clear understanding of the polymorphs selection during crystallization of a random copolymer as well as homo-polymers under confinement.

Effect of Long Chain Branching on the Rheological Behavior,Crystallization and Mechanical Properties of Polypropylene Random Copolymer

Long chain branched polypropylene random copolymers （LCB-PPRs） were prepared via reactive extrusion with the addition of dicumyl peroxide （DCP） and various amounts of 1,6-hexanediol diacrylate （HDDA） into PPR. Fourier transform infrared spectrometer （FTIR） was applied to confirm the existence of branching and（ investigate the grafting degree for the modified PPRs. Melt flow index （MFI） and oscillatory shear rheological properties including complex viscosity, storage modulus, loss tangent and the Cole-Cole plots were studied to differentiate the LCB-PPRs from linear PPR. Differential scanning calorimetry （DSC） and polarized light microscopy （PLM） were used to study the melting and crystallization behavior and the spherulite morphology, respectively. Qualitative and quantitative analyses of rheological curves demonstrated the existence of LCB. The effect of the LCB on crystalline morphology, crystallization behavior and molecular mobility, and, thereby, the mechanical properties were studied and analyzed. Due to the entanglements between molecular chains and the nucleating effect of LCB, LCB-PPRs showed higher crystallization temperature and crystallinity, higher crystallization rate, more uniformly dispersed and much smaller crystallite compared with virgin PPR, thus giving rise to significantly improve impact strength. Moreover, the LCB-PPRs exhibited the improved yield strength. The mobility of the molecular chain segments, as demonstrated by dynamic mechanical analysis （DMA）, was improved for the modified PPRs, which also contributed to the improvement of their mechanical properties.

COMBINED EFFECT OF MODIFIED ZEOLITE 13X AND β-NUCLEATING AGENT ON IMPROVING β-CRYSTAL CONTENT AND TOUGHENING POLYPROPYLENE RANDOM COPOLYMER

Although addition of β-nucleating agent directly into homo-polypropylene （PPH） is a useful method to improve ,β-crystal content and toughen PPH, polypropylene random copolymer （PPR） makes this method powerless due to its random structure and low crystallinity. In this study, the β-nucleated PPR with high β-crystal content was prepared by a novel high effective β-nucleating system which consists of β-nucleation agent （TMB-5） and modified zeolite 13X （M13X）. It was found that M13X and TMB-5 had a synergistic influence on improving β-crystal content and toughening PPR. The content of β-crystal in PPR/M13X/TMB-5 was significantly larger than the sum of that in PPR/M13X and PPR/TMB-5. Besides, fracture behavior, phase morphology and relaxation of matrix chain segments were also investigated. The results showed that M13X and TMB-5 improved the mobility of amorphous chain segments at low temperature and contributed to much energy dissipation. This work provides a powerful method to modify PPR.

长径比对PPR/CNT复合体系流变性能的影响

采用熔融共混法制备了2种不同长径比的碳纳米管(CNT)填充聚丙烯无规共聚物(PPR)复合体系,研究了PPR/CNT复合体系的稳态以及动态流变性能。结果表明:CNT的加入使得PPR体系的剪切应力、剪切黏度以及入口压力降提高,损耗因子降低,且大长径比CNT的加入对PPR体系的影响程度更为明显。当大长径比CNT的质量分数大于1%时,PPR/CNT复合体系出现了明显的拉伸硬化现象,而小长径比CNT的质量分数为5%时,复合体系才出现了微弱的拉伸硬化现象。CNT的加入能使PPR体系的储能模量以及复数黏度增加,在大长径比的CNT填充PPR复合体系中效果更为明显。

SYNTHESIS AND CHARACTERIZATION OF RANDOM OR GRADIENT BUTADIENE-p-METHYLSTYRENE COPOLYMERS VIA ANIONIC POLYMERIZATION

Copolymers of 1,3-butadiene and p-methylstyrene （p-MS） were synthesized via anionic polymerization. A benzophenone-potassium complex was added to tune the reactivity ratio of the two monomers, leading to random and gradient composition alonglthe copolymer chain. The overall composition and microstructure could be controlled and well characterized by GPC and H-NMR. The p-MS was distributed from gradient to random with increasing the content of the benzophenone-potassium complex, and the 1,2-microstrucmre in the polybutadiene sequence increased at the same time. The hydrogenation of the copolymer of 1,3-butadiene and p-MS resulted in the corresponding saturated copolymer with well- defined structure and narrow molecular weight distribution.

Anionic synthesis of binary random in-chain multi-functionalized poly(styrene/butadiene/isoprene and dimethyl [4-phenylvinyl)-phenyl]silane)(PS-DPESiH,PB-DPESiH,PI-DPESiH) copolymers

The binary random in-chain silyl-hydride multi-functionalized poly（styrene/butadiene/isoprene and dimethyl[4-（1-phenylvinyl） phenyl]silane） （PS-DPESiH, PB-DPESiH, PI-DPESiH） copolymers were successfully synthesized. These functionalized copo- lymers were prepared in hexane with n-BuLi as the initiator at 50℃ for 4 h. The silyl-hydride groups were introduced into polymer backbones quantitatively by living anionic polymerization. The copolymers were determined through 1H NMR, size exclusion chromatography （SEC） and differential scanning calorimetry （DSC） techniques, while the number of silyl-hych-ide groups was calculated and discussed.

不同α成核剂调控对无规共聚聚丙烯B4801的影响

研究了不同α成核剂NX8000K、HB3988、WNA-108、WNA-21、WBQ-88对无规共聚聚丙烯B4801的结晶性能、力学性能、透光率、雾度及熔融指数等的影响。结果表明,5种成核剂均有效促进了聚丙烯B4801的结晶过程,表现出良好的聚丙烯诱导结晶性,其中WNA-21的效果最好。5种成核剂均可以明显提升聚丙烯B4801的拉伸性能、弯曲性能、热变形温度,并且在较低质量分数(1500μg/g)时提升作用基本达到最大,对收缩率和流动性也有一定的提高,但对缺口冲击强度都有不同程度的降低,其中添加WNA-108下降尤为明显。除了WNA-108外,其余4种成核剂的引入均明显提高了聚丙烯的透明性。