The effect of fertilizer nitrogen input to grass-clover swards and calving date on the productivity of pasture-based dairy production

The objective of this systems-scale study was to investigate grazing season timeframes on pasture and milk production and on milk processability of dairy systems with compact spring-calving dairy cows grazing white clover (Trifolium repens L.) based grassland. Fifty-four primiparous and multiparous Holstein-Friesian dairy cows were used in a one-factor study with 3 systems (n = 18) and repeated over 2 yr (2008/09 and 2009/10). The 3 systems were: early spring calving with annual fertilizer N input of 100 kg·ha^?1 applied in spring (ES100N; 2.1 cows·ha^?1; grazing February to November), early spring calving without fertilizer N (ES0N; 1.6 cows·ha^?1; grazing February to November) and late spring calving without fertilizer N (LS0N; 1.53 cows·ha^?1; grazing April to January). Annual pasture production was affected by an interaction between grazing system and year: Mean annual pasture yields for 2008 and 2009 were ES100N; 10.35 and 9.88, ES0N; 8.88 and 8.63, LS0N; 9.18 and 10.31 t of dry matter (DM)·ha^?1 (SEM 0.39). LS0N had higher pasture DM yield in 2009 due to higher clover DM production and biological N fixation compared with the other systems. Clover stolon and root mass in the following February was correlated with stolon and root mass in the previous November with 64% of stolon mass present on LS0N in February (R² = 0.84). There were no detectable differences in per-lactation milk yield (6,335 kg·cow^?1), fat, protein and lactose yields (271, 226, 297 kg·cow^?1, respectively), cow liveweight (585 kg) or body condition score (3.02). Although winter grazing favored subsequent clover DM production, biological N fixation and pasture DM production, delaying calving date in spring and extending lactation into the following winter led to inefficient use of this pasture by the grazing herd and lowered the quality of late-lactation milk for processing purposes. Hence, a mean calving date in mid- to late-February is recommended for zero-fertilizer N input clover-based grassland.     

钛酸钾对PVC性能的影响

研究了PVC(聚氯乙烯)/PTW(钛酸钾晶须),PVC/CPE(氯化聚乙烯)、PVC/PTW/CPE复合体系的力学性能,讨论了CPE和PTW的加入对硬质PVC加工性能的影响。结果表明:加入PTW将导致体系的力学性能降低;在一定的比例范围内同时加入PTW与CPE,二者具有协同增韧的作用;PTW的加入增大了体系加工时的粘度,缩短了塑化时间.     

季铵盐在工程机械轮胎胎面胶中的应用

研究季铵盐在工程机械轮胎胎面胶中的应用.结果表明：随着季铵盐用量的增大,胶料的硫化速度提高,交联密度增大,硫化胶的硬度和定伸应力增大,拉断伸长率减小,耐磨性能提高,撕裂强度和抗切割性能先提高后降低,季铵盐的最佳用量为0.1份;成品轮胎的工艺性能良好,质量优异,解决了常见的花纹圆角和胎面缺胶问题.     

多功能橡胶硫化活性剂ZH-73对全钢载重子午线轮胎胎面胶性能的影响

研究多功能橡胶硫化活性剂ZH-73对子午线轮胎胎面胶硫化特性、加工性能、物理性能和动态力学性能等的影响。结果表明:加入2份硫化活性剂ZH-73,混炼胶的门尼焦烧时间略缩短,t90延长,流动性提高,加工性能改善;硫化胶老化前后物理性能相当,60℃的损耗因子明显减小;成品轮胎耐久性能提高,滚动阻力系数降低。     

高岭土与膨润土复配填充丁苯橡胶复合材料的性能

以高岭土与不同类型的膨润土JZ-PRT、Na-PRT和Ca-PRT复配,用硅烷偶联剂Si-69进行球磨改性,得到复配黏土K-JZPRT、K-Na PRT和K-Ca PRT,将其作为增强剂填充到丁苯橡胶(SBR)中,制备了复配黏土/SBR复合材料,用X射线衍射仪、傅里叶变换红外光谱仪以及冷场发射扫描电子显微镜对复配黏土及复合材料进行了表征,并考察了复合材料的加工性能、力学性能和气阻隔性能。结果表明,复配黏土中膨润土的特征衍射峰强度都有所降低,高岭土除d001衍射峰外,其他特征衍射峰强度都有不同程度的弱化。与填充K-JZPRT的SBR复合材料相比,填充K-Na PRT和K-Ca PRT的复合材料的硫化速率更快,门尼黏度更低,因而加工性能也更好。填充复配黏土的复合材料的力学性能和气阻隔性能较SBR均有明显改善,其中K-Na PRT的填充效果最好,拉伸强度增加了652%,透气率降低了43%。复配黏土在SBR基体中分散比较均匀,与橡胶分子的结合良好。     

Adhesive Properties of Cured Phenylethynyl-Containing Imides

As part of a program to develop structural adhesives for high-performance aerospace applications, work has continued on phenylethynyl-containing imides. Initial work on linear phenylethynyl-terminated imides (PETI), led to a material called LaRC? PETI-5, which is now commercially available and was selected as the composite matrix resin and adhesive on the High Speed Research Program. In this report, the preparation and evaluation of a series of modified phenylethynyl-containing imides, which are being developed as secondary bonding adhesives, will be discussed. The modification of these materials compared with the linear material involves the use of a small amount of trifunctional monomer to introduce branching. These adhesives exhibit excellent processability at pressures as low as 15 psi and temperatures as low as 288°C. The cured polymers exhibit excellent solvent resistance and high mechanical properties. Polymer properties can be controlled by varying the molecular weight, the amount of branching, and the phenylethynyl content. This research involves changing the flexibility in the copolyimide backbone of the branched, phenylethynyl-terminated adhesives and determining the effect on properties.     

三氯环硼氮烷改性聚碳硅烷的合成及陶瓷转化

为研究三氯环硼氮烷(TCB)对聚碳硅烷(PCS)性能及陶瓷转化的影响,将一定量的TCB加入PCS中制备TCB改性PCS聚合物,分析了TCB与PCS的反应性及TCB用量对改性PCS结构、陶瓷收率、可加工性和SiC产物微结构的影响,并采用红外光谱、热重、X射线衍射等测试技术对相应产物进行表征.结果表明,PCS中的Si-H键可部分地与TCB中的-Cl反应生成HCl;随着TCB质量分数的增加,PCS中Si—H键相对于Si-CH3的浓度比呈下降趋势.TCB的加入可显著提高PCS的陶瓷收率,TCB质量分数大于8%时,陶瓷收率质量分数约增加10%.TCB质量分数为5%～8%时,可在提高PCS收率的同时使其保持较好的可加工性能,TCB质量分数大于8%时,可加工性能变差.B、N的引入对SiC的微结构有影响:在氩气保护下,经1000℃热处理时,TCB的加入促进SiC晶粒的生长;经1400℃热处理时,TCB的加入抑制SiC晶粒的长大.     

洗衣机内桶专用料HHP1的生产

分析了聚丙烯洗衣机内桶专用料ＨＨＰ１的性能及其与通用料的区别；介绍了ＨＨＰ１生产工艺，从化验分析数据找出了影响性能的因素加以优化控制，生产合格的洗衣机内桶专用料。     

Sheet molding compound characterization using spiral flow

Sheet molding compound (SMC) is a fiber‐reinforced polymeric composite. It is often used in automotive, marine, and industrial applications over other materials because of its high strength to density ratio, resistance to corrosion, and low cost. There is a demand in the SMC industry to be able to characterize SMC processability. This is particularly true for heavy truck body panels, one of the fastest growing applications of SMC. Because of their large size and high strength requirement, the molding forces have a major influence in the molding cycle. Also because of the long flow paths involved, the ability of the paste to carry glass needs to be properly characterized when developing new SMC materials. In this article, we demonstrate the benefits of using spiral flow as a processability tester. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008