This article investigates the effect of swelling temperature on palmitic acid-based shape memory natural rubber (SMNR). SMNR has high storage modulus and excellent energy absorption capability which is suitable to replace the electronic parts in the lightweight machine. Although the swelling process increased the trigger temperature of palmitic acid-based SMNR, high thermal energy in swelling process might accelerate the degradation of the SMNR. To verify the swelling effect, two rubber sources were adopted in the sample preparation and immersed into molten palmitic acid. A custom-made elongation device which is introduced in the methodology section was used to measure the shape memory parameters under different deformation strains (100%, 200% and 300%). It was found that both swollen rubber sources stood their own beneficial shape memory parameters. For example, high shape fixation (\(>90\%\)) was found in natural rubber latex film (NRLF) specimen, while natural rubber (NR) specimens had outstanding shape recovery (100%). Swelling experiment revealed that the solvent diffusion rate was increased in higher swelling temperature, but crosslink density of rubber specimen limited the penetration of palmitic acid and maximum solvent uptake amount. Strain control mode test indicated that the swelling temperature accelerated the chain scission process which decreased the crosslink density of rubber specimens, but shape fixation was increased by high void formation. The DSC test clearly showed that trigger temperature varied with the solvent contents in the rubber specimens. Scanning electron microscopy images illustrated that the precoated palmitic acid was formed on the rubber molecules. The relationship between the swelling temperature and shape memory parameters of SMNR was established and the trigger temperature of SMNR was successfully increased near the melting temperature of fatty acid.

中文翻译：

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棕榈酸基形状记忆天然橡胶的溶胀温度与形状记忆性能之间的关系

本文研究膨胀温度对基于棕榈酸的形状记忆天然橡胶（SMNR）的影响。SMNR具有较高的储能模量和出色的能量吸收能力，适合替代轻型机器中的电子零件。尽管溶胀过程增加了基于棕榈酸的SMNR的触发温度，但溶胀过程中的高热能可能会加速SMNR的降解。为了验证溶胀效果，在样品制备中采用了两种橡胶源并将其浸入熔融的棕榈酸中。方法部分介绍的定制伸长设备用于测量不同变形应变（100％，200％和300％）下的形状记忆参数。发现两个溶胀的橡胶源均具有其自身有益的形状记忆参数。例如，高形状固定（\（> 90 \％\）在天然橡胶胶乳薄膜（NRLF）标本中发现），而天然橡胶（NR）标本具有出色的形状回复性（100％）。溶胀实验表明，在较高的溶胀温度下，溶剂的扩散速率增加，但橡胶样品的交联密度限制了棕榈酸的渗透和最大的溶剂吸收量。应变控制模式试验表明，溶胀温度加快了断链过程，从而降低了橡胶样品的交联密度，但由于高空洞形成而增加了形状固定。DSC测试清楚地表明，触发温度随橡胶样品中溶剂含量的变化而变化。扫描电子显微镜图像表明，预涂的棕榈酸在橡胶分子上形成。