PVC门窗型材抽查中常见质量问题及其对策

1抽查中常见质量问题近几年,国家塑料制品质量监督检验中心(福州)对PVC门窗型材进行了抽查,抽查结果表明:产品质量比较稳定,大中型企业生产管理较规范,合格率较高;检验不合格项目主要集中在加热后尺寸变化率、拉伸冲击强度以及落锤冲击强度3个项目。尺寸变化率反映了材料残留内应力大小,同时表征     

PVC门窗型材抽查中常见质量问题及其对策

1抽查中常见质量问题近几年,国家塑料制品质量监督检验中心(福州)对PVC门窗型材进行了抽查,抽查结果表明:产品质量比较稳定,大中型企业生产管理较规范,合格率较高;检验不合格项目主要集中在加热后尺寸变化率、拉伸冲击强度以及落锤冲击强度3个项目。尺寸变化率反映了材料残留内应力大小,同时表征     

影响PVC异型材加热后尺寸变化率的三个因素

通过一系列对比试验，分析PC异型材加热后尺寸变化率的影响因素，提出改善异型材尺寸变化率的看法。     

沈橡四厂高压钢丝胶管质量上乘

沈橡四厂高压钢丝胶管质量上乘在３月１５日“人民日报”公布的１９９３年第４季度国家监督抽查合格产品中，沈阳第四橡胶厂高压钢丝编织胶管榜上有名。在全国１９家生产该产品的厂家抽查中，经过耐油性、低温弯曲、静压试验、长度变化率、爆破试验等项目检验，沈橡四厂质...     

减震器油封胶料的配方设计

根据汽车、摩托车筒式减震器的工作原理，在筒式减震器中，减震液是实现阻尼、减震的主体。只有贮油缸和工作缸中的减震液，在不断地压缩、复原循环中保持恒定的数量，才能实现减震功能的可项目指标硬度（邵尔A）／度８０５５断裂强度／MPa＞１２扯断伸长率／％＞２００１００％定伸应力／MPa＞６磨耗量（DIN５３５１６）＜２００耐寒性（－４０℃×２２h）不得有裂纹１２０℃×９４h热空气老化后硬度（邵尔A）变化／度０～５断裂强度变化率／％０～６扯断伸长率变化率／％－１０～０１００℃×９４h减震器油浸泡后硬度（邵尔A）变化／…     

基于弹性模量属性的AVO交汇分析方法及应用

文中针对C区一条地震测线的PP波资料,将运算出的P波阻抗变化率、S波阻抗变化率、泊松比变化率等叠前属性,通过使用交汇分析等技术,检测出含气异常区。本文以—属性对为例进行AVO交汇分析。     

利用声发射技术预报采场冒顶的新方法

提出了评价岩体稳定性的三个有效指标，即ＡＥ事件Ｃ，ＡＥ能量Ｅ和ｍ值的变化率。应用灰色理论方法预测采场冒顶时刻的声发射参数值，从而方便地确定了各ＡＥ参数变化率的临界值。据此，可预报采场冒顶的发生。     

不同聚乙烯基塑木复合材料的性能

采用注塑工艺制备高密度聚乙烯(HDPE)基、低密度聚乙烯(LDPE)基及HDPE、LDPE混合基塑木复合材料(WPC),同时制备了纯HDPE及LDPE试样，对比研究了不同试样的吸水率、吸水尺寸稳定性、受热尺寸稳定性、耐冷热循环性、抗低温冻融性及抗冲击性能。结果表明，纯塑料的吸水率及吸水后尺寸变化率均较低，但是，受热后正反面尺寸变化相差较大，冷热循环后尺寸变化较大；当形成WPC后，试样的吸水率及吸水后尺寸变化率显著升高，其中，HDPE与LDPE混合基体的WPC的吸水率最高，其值为1.57%,宽度和厚度尺寸变化率分别为0.11%和1.08%;受热后，正反面尺寸变化率差值减小，耐冷热循环能力得到显著提升；HDPE及其WPC的弯曲强度与LDPE及其WPC相比较高，但是，后者的抗冻融性能及抗冲击性能与前者相比较好。     

2种方式干燥的天然橡胶干燥特性之研究

为探讨微波干燥天然橡胶新技术，分别在温度115℃下，采用电热烘箱产生热空气和微波干燥装置干燥湿天然橡胶胶粒，对二者的干燥特性及硫化胶性能进行对比分析研究。结果表明，微波干燥只需13．467min就可使胶料含水量降至0．791％，热空气干燥则需211min。天然橡胶微波干燥和热空气干燥主要包含失水率加速期、失水率减速期、失水率相对恒速期3个失水阶段。整个干燥过程中，微波干燥失水率较大，而热空气干燥失水率比较小。微波干燥天然橡胶硫化胶的耐热氧老化性能得到显著提高：其老化前后拉断伸长率变化率（-35％）和拉伸强度变化率（-59％）明显高于热风干燥天然橡胶硫化胶的拉断伸长率变化率（-62％）和拉伸强度变化率（-89％）。     

铝电极对PTC陶瓷老化的影响

在各种不同的表面温度Ts=130～300℃的PTC陶瓷上烧渗铝电极。并进行通电热老化实验，结果表明：表面温度Ts越高其电阻变化率增大越快，当Ts小于200℃时电阻变化率比较小。并指出了电极是影响PTC陶瓷老化的主要因素。     

聚乙烯热收缩片材挤出拉伸一次成型工艺研究

利用高分子材料“取向—解取向”原理,实现了聚乙烯（PE）片材挤出拉伸一次成型,并探讨了通过三辊压光机对聚乙烯片材进行拉伸定型的方法,研究了辊筒温度、拉伸率、拉伸距离和拉伸速度对PE片材收缩率和截面厚度的影响。结果表明,拉伸率、拉伸距离对PE片材收缩率影响较大,提高拉伸率,降低拉伸距离均可提高片材收缩率,辊筒温度和拉伸速度对收缩率影响较小,提高辊筒温度、拉伸速度,能小幅增加收缩率;在辊筒温度60 ℃、拉伸率45 %、辊筒距离1.5 mm、拉伸速度2.4 m/min情况下,PE片材收缩率可达78 %（10 min,120 ℃）。     

电缆燃烧烟气释放速率的实验研究

为系统地了解电缆在燃烧过程中烟气释放速率以及其与其他参数间的关系,利用锥形量热仪对YJV 4 6电缆的燃烧行为进行了分析。结果表明,电缆在不同外界热流强度下的燃烧行为是不同的。随着热辐射强度的增大,电缆燃烧时的烟气释放速率也随之增大。电缆燃烧时热量的释放滞后于烟气的释放,烟气释放速率随质量损失速率增加而增大。稳定燃烧状态下则表现为烟气释放速率降低,热释放速率增大。     

Drying of Suspensions in a Fluidized Bed of Inert Particles Under Reduced Pressure

A drying method in which a heat-sensitive material is immersed in a fluidized bed under reduced pressure was used to continuously obtain dispersed, dry, fine powders of that material from a dilute suspension or solution at a low temperature with a high drying rate. The mass velocities of the drying gas, sample flow rate, and chamber pressure were varied, and the effects of these variations on the corresponding drying characteristics were examined.

The fluidization state of a fluidized bed of inert particles strongly affects the drying rate in the bed and has a greater effect than the chamber pressure on the corresponding drying characteristics. In other words, it is important to maintain a vigorous fluidization state to achieve a high drying rate. Although the maximum drying rate is independent of the chamber pressure, it can be achieved at a low mass velocity of the drying gas under reduced pressure. That is, at a low chamber pressure a high drying rate can be achieved, even at a relatively low mass velocity of the drying gas. The bed temperature at the time of drying is strongly influenced by the drying rate and decreases linearly with an increase in the maximum drying rate when the sample flow rate is equal to the drying rate.     

DRYINC RATES DURING HIGH TEMPERATURE DRYING OF YELLOW POPLAR

Experimental drying rates during high temperature drying of Yellow Poplar is analyzed to determine types of drying mechanism. Drying rate during the constant rate period and effective diffusivity during the falling rate periods were obtained at dryer temperatures ranging from 100°C to 150°C.

The drying curve shows three drying regimes: a constant-rate period, and two falling rate periods. The constant rate period, where the drying rate is a linear function of time, is controlled by the rate of heat transfer to the wood surface. Both falling rate periods show a drying rate which is a linear function of the square root of time. Floisture migration during the first falling rate is by simultaneous capillary action and liquid diffusion. while moisture'migration takes place by vapor diffusion during the second falling rate period. This occurs when the moisture content of the wood falls below the fiber saturation point. The effective diffusion coefficient during both periods is found to be constant.     

Solids flow characteristics in loop-seal of a circulating fluidized bed

The hydrodynamics of solids (FCC) recycle in a loop-seal (0.08 m) at the bottom of the downcomer (0.08 m-I.D.x4.0 m-high) in a circulating fluidized bed (0.1 m-I.D.x 5.3 m-high) have been determined. Solid flow rate through the loop-seal increases linearly with increasing aeration rate. At the same aeration rate, the maximum solid flow rate can be obtained at a loop-seal height-to-diameter ratio of 2.5. The effects of solid inventory, solid circulation rate and gas velocity on pressure balance around the CFB have been determined. At a given gas velocity and solid circulation rate, pressure drops across the downcomer and loop-seal increase linearly with increasing solids inventory in the bed. At a constant solid inventory, pressure drops across the riser and the downcomer increase with increasing solid circulation rate but decrease with increasing gas velocity in the riser. The obtained solid flow rate has been correlated with pressure drop across the loop-seal.     

Post‐yield behavior of thermoplastics and the application to finite element analysis

This report delineates the rate sensitivity of three commodity thermoplastics and assesses the appropriateness of assuming simple rate dependence in finite element analysis. Polycarbonate does indeed show simple rate dependence in the plastic region with very rapid adjustment from one rate to the next; thus, a rate dependent model is an accurate representation. Acrylonitrile/Butadiene/Styrene (ABS) does not exhibit such large plastic strains and is a bit more complex with a process of craze formation leading to more variable necking and failure. It also shows a rapid transition from one rate to another, but superimposed failure processes impart considerable variability. Assuming simple rate dependence is a reasonable approximation and directionally correct. An impact‐modified polypropylene exhibits craze formation, a very low Poisson's ratio to large extensions and simple rate dependent behavior before failing. At elevated temperature, it draws and forms a stable neck and again shows simple rate dependence. However, the processes of failure and transition to necking are not simply rate dependent and this will keep this assumption from being generally valid.     

过滤方式及压力对速率影响的研究

介绍了相关过滤方式的优缺点,自主建立了过滤实验流程,设计出相应的膜滤器,通过实验,研究了横向终端过滤、竖向终端过滤、横向错流过滤和竖向错流过滤及过滤压力对过滤速率的影响等。结果表明:采用竖向流动错流过滤方式膜过滤速率大于其它方式的过滤速率,衰减最为缓慢,且一段时间后,速率趋于一定值;压力增大可以提高竖向流动错流过滤速率,但也加快了膜污染,使膜速率衰减加快。     

Estimation of the turbulent kinetic energy dissipation rate from 2D-PIV measurements in a vessel stirred by an axial Mixel TTP impeller

The turbulent dissipation rate is a key parameter in stirred tanks and its local values may have a strong influence on the performance of many processes. However, the local dissipation rate estimation is far from easy in a stirred tank, especially near the impeller discharge where maximum values are encountered. The aim of this work is to estimate the dissipation rate in a vessel used for animal-cell cultures and stirred with a down-pumping axial impeller (Mixel TTP) from velocity fields measured by 2D-PIV. Special attention is paid to the assumptions necessary to estimate the dissipation rate from 2D measurements and to the influence of measurement spatial resolution on the estimated values. The analysis of isotropy ratios measured on vertical, horizontal and tangential planes shows that the turbulence in the impeller discharge is far from isotropic. Isotropy assumptions classically used to estimate the dissipation rate from 2D measurements may thus lead to erroneous values. Based on the measured isotropy ratios, a new relationship is proposed to estimate the dissipation rate in the impeller discharge. This relationship is then used to estimate the dissipation rate on a vertical plane located in the impeller discharge zone. In order to analyze the influence of the measurement spatial resolution on the estimated values of the dissipation, a total of 12 spatial resolutions are tested. Results show that if the spatial resolution is divided by a factor 2, the dissipation rate increases by 220%. For the smallest spatial resolution value used, the maximum dissipation rate estimated is 50 times higher than the mean overall dissipation rate and the corresponding minimum value of the Kolmogorov scale is nearly 3 times smaller than the Kolmogorov scale computed from the mean overall dissipation rate.     

QUANTIFICATION OF THROUGH DRYING RATE DATA

ABSTRACT

For through drying there are three distinct drying rate periods, increasing rate, constant rate and falling rate. The increasing rate period is so important that nearly half of the drying is completed in this period only. A drying rate - moisture content relationship for this period was obtained based on theoretical analysis. It was verified with experimental data. A quantitative representation of the complete drying rate curve was established using this relationship and a modified power law equation for the falling rate period drying rate - moisture content relation. It needs five parameters to quantify the through drying from wet to dry: moisture content at the end of the increasing rate period; exponent for the drying rate - moisture relationship during the increasing rate period; constant drying rate; critical moisture content and the power-law exponent for the falling rate period.     

Effect of Segment Scale in a Pore Network of Porous Materials on Drying Periods

Drying periods of porous glass disks of nonhygroscopic MPG glass and hygroscopic Vycor glass were investigated. A simple model of dimensionless segment sizes is proposed where a dimensionless segment size is equal to the value of the tortuosity factor of gas diffusion. This model was applied to the estimation of the segment size and the drying periods of a porous Vycor glass disk. The drying rate curve of the Vycor glass disk showed that the first falling rate period appeared to be included in the constant rate period and that the second falling rate period started right after the constant rate period ended, whereas the drying rate curve of the MPG glass disk estimated from previous models showed that the first falling rate period and the second falling rate period were clearly distinguished. The difference in drying periods between two porous glass disks was caused by a large difference in the respective segment sizes.