硅胶件的生物学与物理性能考察

结论：硅胶的优点明确，但有几个特有的关注点

硅胶在医疗器械上用得很多——密封圈、导管、面罩、按键、防护套、乳垫。 它的优点是生物相容性记录良好、温度适用范围宽、柔软有弹性、可反复灭菌。

但它有几个特有的关注点：

低分子硅氧烷的残留。 交联不完全或未做后处理时，低分子组分可能迁移。

压缩永久变形。 密封件长期受压后的回弹能力。

交联体系的差异。 不同交联方式的残留物不同。

表面特性。 发粘、吸附、以及与其他材料的相容。

这几点在选材和评价中都要考虑。

硅胶的类型

「加成型」是医疗应用的常见选择，因为它不产生副产物，残留相对可控。但加成型对某些物质（硫、氮、磷化合物）敏感，接触后可能中毒不固化。

物理性能的考察

硬度。 邵氏硬度，影响手感和功能。

拉伸强度与伸长率。 基础力学性能。

撕裂强度。 硅胶的撕裂强度相对较低，是常见的失效模式。

压缩永久变形。 密封件的关键指标 ——长期受压后能回弹多少。

回弹性。 变形后的恢复。

耐温性能。 高低温下的性能保持。

耐老化。 长期性能。

「撕裂强度」在薄壁件和有缺口的件上是关键 ——硅胶一旦起裂，扩展较快。

「压缩永久变形」决定密封件的寿命 ——永久变形大意味着密封力下降快。

挥发分与低分子组分

来源。 未交联的低分子硅氧烷、交联副产物、加工助剂。

影响。 迁移到接触介质、造成表面发粘、影响粘接、以及生物相容性方面的关注。

后处理。 高温烘烤能显著降低挥发分含量，这是医疗级硅胶件的常见工序。

检测。 挥发分含量的测定、化学表征。

「后处理烘烤」是降低残留的有效措施，而是否做后处理、做多久，直接影响残留水平，这一点在验证时要确认。

交联相关的考察

交联度。 交联是否充分，影响力学性能和残留。

交联抑制。 加成型硅胶接触某些物质会抑制固化，表现为表面不固化或发粘。

残留的催化剂。 交联体系的组分残留。

副产物。 缩合型硅胶的副产物。

「交联抑制」在生产中是实际问题 ——模具上的脱模剂、手套上的物质、某些塑料件的助剂，都可能导致局部不固化。这部分未固化的硅胶残留量高。

生物学方面的关注

基础项目。 细胞毒性、刺激、致敏。

长期接触的额外项目。 按接触时间确定。

化学表征。 释放物质的识别与定量，低分子硅氧烷是主要的关注对象。

试样状态。 完成交联和后处理、经过灭菌。

颜色与填料。 着色剂和补强填料也要纳入评价。

「补强填料」在硅胶中用量不小，它影响力学性能，也可能是释放物质的来源。

工艺相关的问题

脱模剂的残留。 影响后续的粘接和生物相容性。

飞边与毛刺。 影响外观和使用。

粘接。 硅胶与其他材料的粘接较困难，需要特定的底涂或工艺。

印刷与标识。 硅胶表面的标识附着困难。

清洁。 硅胶表面易吸附灰尘和颗粒。

「硅胶与其他材料的粘接」是工艺上的难点，因为硅胶表面能低，需要等离子处理、底涂或者机械互锁的结构设计。

灭菌相关

耐受性好。 硅胶对多数灭菌方式耐受。

辐照的影响。 可能影响交联程度和力学性能。

反复灭菌。 可重复使用件的多次灭菌耐受。

灭菌后的性能复测。 建议做，特别是压缩永久变形和力学性能。

常见的准备不足

信息不全。 材料、工艺、使用环境的信息缺失，导致方案设计缺乏依据。

样品不具代表性。 试制样品或挑选样品，与量产状态有差距。

条件未明确。 测试条件没说清楚，数据的适用范围就不明确。

只看初始值。 忽略了环境和时间作用后的性能变化。

项目不完整。 遗漏了必要的项目，提交时才发现。

这五项在实际委托中出现频率较高，建议在项目启动时逐项确认，因为它们造成的返工成本远高于事前确认所花的时间。

数据的组织与保存

记录的完整性。 条件、方法、设备、样品状态、实测值。

可追溯性。 数据与样品批次、生产批次的关联。

保存期限。 覆盖产品的生命周期。

检索的便利。 需要时能快速定位。

版本的管理。 数据更新时的版本控制。

建议建立统一的数据台账，记录每组数据的来源、条件、适用范围和有效期。数据积累起来之后，后续的产品开发和变更评估都能受益。

与整体工作的衔接

这部分工作不是孤立的，它与几项内容相关：

与设计的衔接。 数据是设计决策的依据，也是设计验证的证据。

与风险管理的衔接。 识别出的风险点应当有对应的验证。

与变更管理的衔接。 变更时判断是否需要重新验证。

与生产控制的衔接。 关键参数的控制限值来自验证数据。

与售后的衔接。 失效分析需要原始数据作为对照。

建议在项目规划时就把这些衔接关系理清楚，避免各环节各做各的、数据无法互相支撑。

我们的做法

做硅胶件测试时，压缩永久变形是我们建议必测的项目，特别是密封类件——因为它直接决定密封力随时间的保持，而这在新品的密封测试中看不出来。

化学表征的样品要求完成后处理，因为后处理对低分子组分的去除效果明显，未做后处理的样品数据不代表实际产品。

对于加成型硅胶，我们会关注是否存在局部不固化的情况，因为这部分区域的残留水平与正常区域差别很大。

如果你有硅胶件需要做性能或生物学相关的检测，可以把材料类型、工艺和应用发过来一起讨论，或者直接联系：132 4819 8029。能力范围见服务介绍，送检要求见送检要求，其他问题见常见问题。

English version

Conclusion. Silicone is widely used in medical devices: seals, catheters, masks, keypads, protective covers and cushioning. Its advantages are a good biocompatibility record, a wide service temperature range, softness and elasticity, and tolerance of repeated sterilisation. It carries several specific concerns. Residual low molecular weight siloxanes may migrate where crosslinking is incomplete or post-curing has not been performed. Compression set determines recovery in seals under sustained load. Crosslinking systems differ in the residues they leave. And surface characteristics include tackiness, adsorption and compatibility with other materials. All of these matter in selection and evaluation.

Types of silicone. Addition cure, platinum catalysed, produces no by-products and shrinks little, suiting medical components and catheters. Condensation cure produces by-products and suits general sealing. Liquid silicone rubber suits precision moulding of small parts. Solid silicone is compression moulded for seals and larger parts. And foamed silicone is soft and cushioning for padding. Addition cure is the common medical choice, producing no by-products with relatively controllable residues, though it is sensitive to certain substances containing sulphur, nitrogen and phosphorus, contact with which can poison the catalyst and prevent curing.

Examining physical properties. Hardness, expressed in Shore units, affects feel and function. Tensile strength and elongation cover basic mechanical properties. Tear strength matters because silicone's tear strength is comparatively low and tearing is a common failure mode. Compression set is the key measure for seals, covering how much recovery remains after sustained compression. Resilience covers recovery after deformation. Temperature performance covers property retention hot and cold. And ageing resistance covers long-term behaviour. Tear strength is critical in thin-walled and notched parts, since once silicone starts to tear it propagates quickly. Compression set determines seal life, since high permanent set means sealing force falls quickly.

Volatiles and low molecular weight species. Sources include uncrosslinked low molecular weight siloxanes, crosslinking by-products and processing aids. Effects include migration into contacting media, surface tackiness, impaired bonding and biocompatibility concerns. Post-curing at elevated temperature markedly reduces volatile content and is a common operation for medical-grade silicone parts. And testing covers volatile content determination and chemical characterisation. Post-curing is an effective measure for reducing residues, and whether and for how long it is performed affects residue levels directly, which should be confirmed during verification.

Crosslinking. Degree of crosslinking affects both mechanical properties and residues. Cure inhibition occurs when addition cure silicone contacts certain substances, appearing as an uncured or tacky surface. Catalyst residues remain from the crosslinking system. And by-products arise with condensation cure. Cure inhibition is a real production problem: mould release agents, substances on gloves and additives in certain plastics can all cause local uncured areas, and uncured silicone carries high residue levels.

Biological considerations. Basic items cover cytotoxicity, irritation and sensitisation. Additional items follow contact duration for prolonged contact. Chemical characterisation identifies and quantifies released substances, low molecular weight siloxanes being the principal concern. Specimen condition must include completed crosslinking, post-curing and sterilisation. And colourants and fillers must be included in the evaluation. Reinforcing fillers are used in substantial quantity in silicone, affecting mechanical properties and potentially contributing released substances.

Process-related issues. Release agent residues affect subsequent bonding and biocompatibility. Flash and burrs affect appearance and use. Bonding silicone to other materials is difficult and requires specific primers or processes. Printing and marking adhere poorly to silicone surfaces. And cleaning is complicated by silicone's tendency to attract dust and particles. Bonding silicone to other materials is the process difficulty, since silicone has low surface energy, requiring plasma treatment, priming or mechanical interlocking design.

Sterilisation. Tolerance is generally good across methods. Irradiation may affect crosslinking and mechanical properties. Repeated sterilisation must be tolerated by reusable parts. And performance should be re-measured after sterilisation, compression set and mechanical properties especially.

How we handle it. For silicone testing we suggest compression set as a standing item, sealing components especially, since it determines directly how sealing force holds over time, which new-product sealing testing cannot reveal. For chemical characterisation we require specimens that have been post-cured, since post-curing removes low molecular weight species effectively and data from specimens without it do not represent the actual product. For addition cure silicone we attend to whether local uncured areas exist, since residue levels there differ greatly from normal areas.

Send us the material type, process and application and we will discuss the testing. Phone or WeChat: +86 132 4819 8029.