In situ examination of water diffusion to the polypropylene-silane interface using FTIR-ATR

This study investigated the effect of moisture on a model silane coupling agent modified adhesive bond. Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy was used to characterize the transport of moisture to a polypropylene-silane interphase and monitor the resulting chemical changes. The FTIR-ATR method offers the advantage of in-situ examination of the diffusion process, as well as the ability to characterize chemical changes that occur due to the presence of moisture. Experiments were conducted at ambient and elevated temperatures. The results of the real-time measurements demonstrated that moisture will migrate through the polypropylene to the silane interphase. The diffusion behavior was described well by a Fickian model. The apparent diffusion coefficients for water in the polypropylene-silane bilayer were on the order of the diffusion coefficients for water in polypropylene at both test temperatures. Furthermore, changes in the spectra were observed during the diffusion experiments. These changes were indicative of hydrolysis of the siloxane backbone in the silane layer while buried beneath the polypropylene film. This finding is significant as it presents direct evidence of a degradation mechanism in silane-modified adhesive bonds. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1971–1985, 1997     

Bio-based thermosetting bismaleimide resins using eugenol,bieugenol and eugenol novolac

5,5′-Bieugenol (BEG) and eugenol novolac (EGN) were synthesized by the oxidative coupling reaction of eugenol (EG) and the addition–condensation reaction of EG with formaldehyde, respectively. The EG, BEG and EGN were prepolymerized with 4,4′-bismaleimidediphenylmethane (BMI) at 180 °C and then compression-molded at finally 250 °C for 6 h to produce cured EG/BMI (EB), BEG/BMI (BB) and EGN/BMI (NB) resins with eugenol/maleimide unit ratios of 1/1, 1/2 and 1/3. The FT-IR analysis of EBs and ¹³C NMR analysis of the model reaction product of EG/N-phenylmaleimide (PMI) 1/3 at 200 °C for 12 h suggested that the ene reaction and subsequent Diels-Alder/ene reactions mainly occurred for EBs. The FT-IR analyses of BBs and NBs supported the occurrence of ene reaction and subsequent thermal addition copolymerization in a similar manner to the well-known curing reaction of 2,2′-diallylbisphenol A and BMI. The glass transition temperature (T_g) and 5% weight loss temperature (T₅) of the cured resin increased with increasing BMI content, and EB 1/3 showed the highest T_g 377 °C and T₅ 475 °C. The flexural strengths and moduli of EBs and NBs were higher than those of BBs, and EB 1/2 showed the most balanced flexural strength and modulus (84.5 MPa and 2.75 GPa). The FE-SEM analysis revealed that there is no phase separation for all the cured resins.     

Realizing the simultaneously improved toughness and strength of ultra-thin LLDPE parts through annealing

Ultra-thin LLDPE parts were prepared by microinjection molding. Mechanical properties and microstructure of samples before and after annealing at different temperatures (60, 80, 100 °C) were analyzed. Tensile test indicates that toughness has been enhanced at least 7 times after being annealed in parallel with significant increase of tensile strength. Microstructure characterizations, including differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), scanning electronic microscope (SEM) and polarized Fourier transform infrared spectroscopy (FTIR) were performed to investigate the variations of microstructure and to further establish the relationship between microstructure and mechanical properties. It is suggested that the increased crystallinity and perfection of crystals upon annealing are beneficial to the reinforcement. Formation of a stronger physical cross-linking network due to the increase of connecting points is in favor of the enhanced strength as well. Moreover, the notable improvement of toughness in the annealed ultra-thin LLDPE parts is ascribed to combined effects of microvoids developed in both the annealing and deformation process. This work offers a simple approach to prepare ultra-thin LLDPE parts with excellent toughness and strength.     

A study of LLDPE functionalized through ultraviolet irradiation and interfacial interaction of PA66/functionalized LLDPE blends

Some oxygen‐containing groups, such as C? O? C, C? OH, C?O, C(?O)O, and C(?O)OH, were introduced onto linear low‐density polyethylene (LLDPE) chains during ultraviolet irradiation under air, without adding any monomers and auxiliaries and without environmental pollution. After ultraviolet irradiation, the molecular weight of LLDPE decreased and its distribution became wider. The melting temperature and crystallinity of irradiated LLDPE decreased with irradiation time. The copolymer LLDPE‐g‐PA66 was formed by reaction between oxygen‐containing groups of irradiated LLDPE and amine or carboxyl end groups and amide linkage of polyamide 66 (PA66) during preparation of PA66/irradiated LLDPE blends. Compared with PA66/LLDPE blend, the mechanical properties of PA66/irradiated LLDPE blends were improved greatly because of the improved interface interaction and dispersion. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

用双毛细管流变仪对 HDPE与LLDPE挤出压力振荡的研究

用RH2000恒速型双毛细管流变仪研究了3种HDPE和3种LLDPE的挤出压力振荡现象。通过压力振荡图、流动曲线和挤出物表观3方面,对两种类型聚乙烯压力振荡的差异进行了分析。发现HDPE的压力振荡很明显,振幅在2~3MPa,而LLDPE的振幅很小,甚至在压力-时间图上看不出来。6种聚合物的流动曲线都发生了断裂。在柱塞下降速度恒定下发生压力振荡时,流速并不恒定,粘界面条件下流速较小,滑界面条件下流速较大,并通过计算获得了3种HDPE发生压力振荡时对应于粘界面与滑界面的流速。HDPE和LLDPE在粘界面条件下挤出物都是鲨鱼皮,而滑界面条件下HDPE的挤出物类似于无规破裂,LLDPE挤出物表观较光滑,且没有鲨鱼皮。     

LLDPE吹塑薄膜加工助剂的研究与应用

本文介绍了LLDPE的加工特性,考察了助剂对LLDPE加工性的影响及加工助剂的协同效果,使用多组分助剂母料在LDPE吹膜机上可高效低耗生产LLDPE农用薄膜。     

Covulcanization of LLDPE/EMA blends using dicumyl peroxide

The effect of dicumyl peroxide (DCP) content on the gel fraction, mechanical, dynamic mechanical, and thermal properties of linear low‐density polyethylene (LLDPE)/ethylene‐co‐methyl acrylate (EMA) blends were studied. Gel content of the blends increases with increasing DCP content, and EMA is more prone to crosslinking than LLDPE. Wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to study the effect of DCP crosslinking on percent crystallinity and crystalline structure of the blends and individual components. At lower level of DCP loading, crosslinking process does not have significant effect on the crystalline structure of the LLDPE, which was confirmed from the percent crystallinity and lattice distance value. However, at higher DCP content, percent crystallinity decreases significantly. At lower EMA concentration (<50%), percent crystallinity and lattice distance remain unchanged up to 2 wt % of DCP. For EMA contents of more than 50 wt %, increasing DCP content reduces the crystallinity of the blends and increases the lattice distance. The highest level of mechanical and dynamic mechanical properties was observed for 60/40 LLDPE/EMA blends at 2 wt % DCP. Addition of LLDPE‐g‐MA (3 wt %) as a compatibilizer enhances the properties of the vulcanizates. Blends crosslinked with DCP up to 0.3 wt % can easily be reprocessed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

基于热分析的LLDPE与LDPE鉴别方法研究

海关进出口税则中规定线性低密度聚乙烯关税税率为6．5％;低密度聚乙烯关税税率为10．3％。两者外观相似而价格和税率都相差较大。用通常的红外分析方法很难区分二者,本文从差热分析方法入手,对二者进行了研究,制定了适合海关实际操作的鉴别方法。结果表明,该方法简便、准确,在实际应用中能获得满意的效果。     

硅烷接枝交联LDPE、LLDPE及其共混物的结构研究

利用红外光谱、凝胶渗透色谱、热延伸试验、差示扫描量热法、扫描电子显微镜等方法研究了低密度聚乙烯（LDPE）、线型低密度聚乙烯（LLDPE）及其共混物的乙烯基硅烷接枝及交联产物的分子结构、熔融行为和形态。结果表明：硅烷接枝后,LDPE、LLDPE的重均摩尔质量小幅增加;硅烷接枝交联能力为：LLDPE〉LDPE／LLDPE共混物〉LDPE;接枝和交联使LDPE、LLDPE及其共混物的结晶度降低,晶粒变得不均匀;硅烷接枝和交联能增加LDPE／LLDPE共混物的相容性;交联结构提高了LDPE、LLDPE及其共混物的抗冲性。     

长链支化LLDPE的制备及表征

利用预辐照线型低密度聚乙烯(rLLDPE)引发基体LLDPE的长链支化反应,制备出长链支化LLDPE。研究了辐照剂量、rLLDPE用量对长链支化反应的影响,并通过熔体流动速率测试、凝胶渗透色谱、13CNMR和扭矩试验对长链支化LLDPE进行了表征。结果表明:与基体LLDPE相比,长支链化LLDPE的熔体流动速率下降,加工扭矩下降,熔体流动速率比(M10/M2)明显增大;形成长链支化的最佳辐照剂量为15kGy、rLLDPE最佳用量为50%;由13CNMR方法计算的长链支化数达1.4/10000C。     

LLDPE薄膜性能影响因素及加工条件优选

研究了线型低密度聚乙烯(LLDPE)吹膜加工温度、吹胀比等对薄膜性能的影响,并对加工条件进行了优选。结果表明:适宜的吹膜加工温度在165～185℃之间;吹胀比不宜超过3.0。典型的工艺条件为:机筒165～185℃;口模155～175℃;法兰180～200℃。     

LLDPE/纳米ZnO复合材料的制备与性能研究

将改性纳米ZnO与线型低密度聚乙烯(LLDPE)熔融共混、制备了LLDPE/纳米ZnO复合材料。通过SEM观察纳米ZnO粒子在LLDPE基体中的分散情况;研究了复合材料的力学性能及维卡软化点。结果表明:改性纳米ZnO的加入可提高LLDPE的力学性能和维卡软化点。其中,复合材料的拉伸强度、断裂伸长率、冲击强度、弯曲强度的最大值分别比LLDPE提高了17.00%、13.42%、9.90%、7.04%。     

Investigation of the crystallization of m(LLDPE) under shear flow using rheo-optical techniques

Metallocene linear low density polyethylene (mLLDPE) crystallization under shear flow at different controlled shear rates was investigated experimentally between its quiescent crystallization temperature and its melting point temperature (T_m). The evolution of the material optical properties, including turbidity, birefringence and dichroism, was monitored following a temperature jump from a temperature much higher than T_m to a fixed crystallization temperature (T_c). These properties are discussed in terms of the evolution of the polymer semi-crystalline microstructure. In light of the optical properties evolution, the crystallization process can be split into three stages (i) incubation phase in which small (compared to the light wavelength) crystalline nuclei spread over the medium, (ii) isotropic crystallite growth phase and (iii) anisotropic crystallite growth phase. The optical properties evolution due the development of the crystallization is compared to that of the stress under the same thermo-mechanical conditions. It is observed that the optical properties are more sensitive than the stress to follow the crystalline development, in particular during the early stage of the process.     

LLDPE吹塑地膜力学性能及工艺技术

论述了近年来LLDPE吹塑地膜研究进展情况。重点阐述了选用不同牌号LLDPE混合树脂吹塑地膜能明显提高其力学性能与吹膜工艺性能及生产效率,并介绍了有关工艺技术要点。     

Ultrasonic improvement of rheological and processing behaviour of LLDPE during extrusion

The effects of ultrasonic oscillations on die pressure, productivity of extrusion, melt viscosity and melt fracture of linear low density polyethylene (LLDPE) as well as their mechanism of action were studied in a special ultrasonic oscillation extrusion system developed in our Laboratory. The experimental results showed that, in the presence of ultrasonic oscillations, the melt fracture or surface distortion of LLDPE extrudate is inhibited or disappears. The surface appearance of the LLDPE extrudate was greatly improved. The productivity of LLDPE extrudate was increased in the presence of ultrasonic oscillations. The die pressure, melt viscosity and flow activation energy of LLDPE decreased with the rise in ultrasonic intensity. The shear sensitivity of LLDPE melt viscosity decreased due to the increase of its power law index in the presence of ultrasonic oscillations. Inducing ultrasonic oscillations into LLDPE melt greatly improved its processability. A possible mechanism for the improved processibility is proposed. © 2003 Society of Chemical Industry     

Characterization of LLDPE/LLDPE-g-AA Blends by Contact Angle and FT-IR Methods

Abstract

Blends of linear low density polyethylene (LLDPE) and linear low density polyethylene-grafted-acrylic acid (LLDPE-g-AA) were prepared by melt mixing. The surface of films with different content LLDPE-g-AA were characterized through contact angle measurements and FT-IR spectroscopy. The contact angles of water and glycerol on films surfaces of LLDPE/LLDPE-g-AA blends decrease with increase of LLDPE-g-AA. From FT-IR spectra of the blends, the carbonyl peak strength on the films surface was calculated. It was found that larger the carbonyl peak strength, the lower the value contact angle for LLDPE/LLDPE-g-AA blends.     

Tensile,flow, and thermal properties of CaCO3‐filled LDPE/LLDPE composites

Calcium carbonate (CaCO₃)‐filled low‐density polyethylene (LDPE)/linear low‐density polyethylene (LLDPE) composites were fabricated by means of a twin‐screw extruder, and the tensile mechanical properties of the tubing with thickness of 0.5 mm made from these composites were measured at room temperature to identify the effect of the filler concentration on the properties of these composites. The results showed that the tensile elastic modulus increased roughly linearly with increasing weight fraction (?_f) of the fillers. The tensile fracture strength (σ_b) along longitudinal direction was obviously higher than that along transverse direction under the same test conditions, especially at higher filler concentration. The values of σ_b of the specimens along both the two directions achieved minimum at ?_f = 20%. Furthermore, the melt flow rate (MFR) and heat enthalpy (ΔH) of the composite materials were measured. It was found that both the MFR and the ΔH decreased with the addition of ?_f. The ΔH for the composite with LDPE/LLDPE ratio of 70/30 was higher than that of the composite with LDPE/LLDPE ratio of 50/50 at the same filler concentration, but contrary to the MFR. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1692–1696, 2007     

PA6/LLDPE共混物的制备与增容作用研究

以乙烯-丙烯酸甲酯-甲基丙烯酸缩水甘油酯三元共聚物(E-MA-GMA)为相容剂,用熔融法在双螺杆挤出机上制备了聚酰胺6/线型低密度聚乙烯(PA6/LLDPE)共混物,并加入降解聚乙烯(DPE)来改变LLDPE的黏度。结果表明:加入10 phr E-MA-GMA可以有效降低PA6/LLDPE(80/20)共混物的分散相尺寸;当LLDPE/DPE=19/1时,共混物的复数黏度和储能模量达到最大值;DPE的加入对共混物的拉伸性能没有明显影响,但使其缺口冲击强度下降。     

木粉对LLDPE膨胀阻燃体系热降解和阻燃的影响

以木粉部分或完全代替季戊四醇作为膨胀型阻燃剂的碳源,研究木粉的加入对LLDPE膨胀阻燃体系热降解和阻燃性的影响.研究表明:木粉对膨胀体系的热降解行为影响不大,当木粉在成炭剂中的质量含量为20%时,膨胀体系的阻燃效果最好.     

淀粉接枝MA共混LLDPE可降解薄膜研究

将α-淀粉酶降解淀粉在引发剂硝酸铈铵的作用下与丙烯酸甲酯接枝生成共聚物,用该共聚物与线型低密度聚乙烯熔融混炼制成可降解薄膜,通过力学性能测试、扫描电镜、热失重分析和降解性能实验等对其进行表征。结果表明:该可降解薄膜具有较好的力学性能和热稳定性,在微生物作用下,具有较好的可降解性。