我国流延聚丙烯膜(CPP)及其专用料的开发进展

CPP膜以其独特、优异的性能在包装领域占有一席之地,应用面广。随着PP树脂专用料质量的改善、设备性能的改进和加工能力的提高,CPP膜的竞争优势将越来越明显,市场份额也将进一步提升。文章对国内流延聚丙烯膜(CPP)的生产开发情况以及CPP专用料的开发进展进行了总结和展望。

流延聚丙烯(CPP)薄膜专用树脂结构与性能分析

通过Ⅹ线广角衍射和傅里叶变换红外光谱等表征方法,从常规物性、熔体流动速率、熔融结晶、相对分子质量以及分子量分布影响因素等方面对国产A和B流延聚丙烯(CPP)薄膜专用料与国外牌号C和D薄膜专用料的结构与性能进行对比分析。结果表明:国产A专用料熔融指数较高(0.85 g/min),易于加工;国外牌号专用料的弯曲和冲击性能较好,更有韧性;国产A专用料结晶速度更快,能提高设备的生产能力和生产效率,国外牌号C专用料有相对较高的结晶度,制作成膜料后可提高挺括度;4种专用料的主要晶型都是α晶型,聚丙烯链段中存在嵌段全同立构,是头尾相接的聚丙烯链段结构;4种专用料的分子量分布都在3.8以上,其中国外牌号D专用料的重均相对分子质量(M_(w))较高,分子量分布相对较宽,聚合物热性能和流动性能较好。4种CPP薄膜专用料的基础物性和微观结构较为相近,国产专用料还需在力学性能方面有所提升。

Microstructural characteristics of Al-20Si-2Cu-0.4Mg-1Ni alloy formed by rheo-squeeze casting after ultrasonic vibration treatment

A swash plate for air conditioning compressor of cars was formed by rheo-squeeze casting with semi-solid Al-Si alloy slurry prepared by ultrasonic vibration process, and the microstructure of this alloy was investigated. Besides the microstructures of primary Si particles and α(Al)+β-Si eutectic phases, non-equilibrium α(Al) particles or dendrites are discovered in the microstructure of the Al-20Si-2Cu-0.4Mg-1Ni alloy. Rapid cooling generated by squeeze casting process rather than the pressure is considered as the main reason for the formation of non-equilibrium α(Al) phase. The sound pressurizing effect of ultrasonic vibration also enables the non-equilibrium α(Al) phases to form above eutectic temperature and grow into non-dendritic spheroids in the process of semi-solid slurry preparation. Non-equilibrium α(Al) phases formed in the hypereutectic Al-Si alloy with ultrasonic vibration treatment, consist of round α(Al) grains formed above the eutectic temperature and a small amount of fine α(Al) dendrites formed under the eutectic temperature. The volume fraction of primary Si particles is decreased significantly by the effect of ultrasonic vibration through increasing the solid solubility of Si atoms in α(Al) matrix and decreasing the forming temperature range of primary Si particles. The average particle diameter and the volume fraction of primary Si particles in microstructure of the swash-plate by rheo-squeeze casting are 24.3 μm and 11.1%, respectively.

走向成熟的国产流延薄膜设备

流延膜是通过熔体流延骤冷生产的一种无拉伸、非定向的平挤薄膜，有单层流延和多层共挤流延两种方式。与吹膜相比，其特点是生产速度快，产量高，薄膜的透明性，光泽性、厚度均匀性等都很出色。同时，由于流延膜是平挤薄膜，其后续工序，如印刷，复合等都极为方便，因而被广泛应用于食品，医药用品，纺织品、鲜花，日用品的包装。

Microstructure and properties of Al-0.70Fe-0.24Cu alloy conductor prepared by horizontal continuous casting and subsequent continuous extrusion forming

A novel process for manufacturing A1-0.70Fe-0.24Cu alloy conductor was proposed, which includes horizontal continuous casting and subsequent continuous extrusion forming （Conform）. The mechanical properties, electrical conductivity and the compressed creep behaviour of the alloy were studied. The results indicate that the Conform process induces obvious grain refinement, strain-induced precipitation of AI7CuzFe phase and the transformation of crystal orientation distribution. The processed alloy has good comprehensive mechanical properties and electrical conductivity. Moreover, a better creep resistance under the conditions of 90 ~C and 76 MPa is shown compared with pure A1 and annealed copper, and the relationship between primary creep strain and time may comply with the logarithmic law. The enhanced properties are attributed to the grain refinement as well as the fine and homogeneously distributed thermally stable A1Fe and A17Cu2Fe precipitation phases.

Multi-objective particle swarm optimization by fusing multiple strategies

To improve the convergence and distributivity of multi-objective particle swarm optimization,we propose a method for multi-objective particle swarm optimization by fusing multiple strategies(MOPSO-MS),which includes three strategies.Firstly,the average crowding distance method is proposed,which takes into account the influence of individuals on the crowding distance and reduces the algorithm’s time complexity and computational cost,ensuring efficient external archive maintenance and improving the algorithm’s distribution.Secondly,the algorithm utilizes particle difference to guide adaptive inertia weights.In this way,the degree of disparity between a particle’s historical optimum and the population’s global optimum is used to determine the value of w.With different degrees of disparity,the size of w is adjusted nonlinearly,improving the algorithm’s convergence.Finally,the algorithm is designed to control the search direction by hierarchically selecting the globally optimal policy,which can avoid a single search direction and eliminate the lack of a random search direction,making the selection of the global optimal position more objective and comprehensive,and further improving the convergence of the algorithm.The MOPSO-MS is tested against seven other algorithms on the ZDT and DTLZ test functions,and the results show that the MOPSO-MS has significant advantages in terms of convergence and distributivity.

Lubrication performance of rapeseed oil-based nano-lubricants in parallel tubular channel angular pressing process

Due to the biological risks of using the conventional lubricants,the vegetable oils have been considered nowadays.Besides,to improve the tribological properties of the vegetable oils in various applications like metal forming processes,nanoparticles have been used as additives.This research evaluated the lubrication performance of the Al2O3 and TiO2 nanoparticles dispersed in rapeseed oil during the parallel tubular channel angular pressing (PTCAP) process.The experimental PTCAP tests have been fulfilled under three lubrication conditions and the comparison between the PTCAP processed tubes has been performed in terms of the maximum forming force,surface roughness,and microhardness.The experimental results indicate that adding the mentioned nanoparticles has caused at least a 50% reduction in the maximum deformation load.Moreover,a remarkable decrement in the surface roughness of the formed tubes has been obtained.

Isothermal extrusion speed curve design for porthole die of hollow aluminium profile based on PID algorithm and finite element simulations

The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative(PID)control algorithm and finite element simulations.The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency.By taking the optimal solution temperature of the secondary phase as the target temperature,the extrusion speed–stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained.Results show that in the traditional constant extrusion speed process,the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement.As the extrusion speed increases,the temperature difference at the die exit of the profile along the extrusion direction increases.The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9℃.Furthermore,the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container,porthole die and external environment.

High temperature tensile behaviors of extruded and rolled AZ31 Mg alloy

High temperature tensile ductilities and deformation mechanisms of an extruded and rolled AZ31 Mg alloy were investigated.Elongation-to-failure tests were conducted under constant T-head velocity and constant temperatures ranging from 300℃ to 450℃.Strain-rate-change tests were conducted under varying strain rate from 5×10-5s-1to 2×10-2s-1and constant temperature from 300℃ to 450℃.Experimental results show that the maximum elongation of the AZ31 alloy with an average grain size of about 19μm is 117%at strain rate of 10- 3s-1 and temperature of 450℃.Stress exponent and activation energy were characterized to clarify the deformation mechanisms.The enhanced ductility is dominated by solute drag dislocation creep,and the major failure mechanism is cavity growth and interlinkage.