改性PP用在注射器外套与手术托盘上，门槛是两道：生物学评价决定能不能接触人体，灭菌方式决定灭完还合不合格——后者常被漏掉。这篇讲清 ISO 10993 的接触分类与化学表征路径，并把 EO、辐照、蒸汽三种灭菌对 PP 的材料后果做成一张可查对照。
有客户问过一句话："我们一直用一款医用级 PP 做注射器外套，换了家灭菌厂走辐照之后，整批怎么又黄又脆？"
这句话里藏着一个被反复验证的判断：医用件的门槛是两道——生物学评价（能不能接触人体）与灭菌方式（灭完还合不合格），而第二道更常被漏掉。
很多团队把精力全压在生物相容性上，灭菌方式临到量产才定，结果料是同一款，换一种灭菌，外观和力学全变了。下面把这两条线、三套灭菌、八项判据，按顺序讲透。
一、工况六维拆解：注射器外套与手术托盘的六个数，先报齐再选型
核心结论：医用 PP 属于改性PP里对洁净与析出要求最严的一档，六维工况里温度和外观两维直接卡死配方方向。
把这两个件的工况拆成六维，每项报出具体数，材料方向才立得住。
| 维度 | 注射器外套的实际工况 | 手术托盘的实际工况 | 对材料的要求 |
|---|
| 温度 | 灭菌温度：EO 常温、辐照常温、蒸汽常到 134℃；储存常温 | 同左，且反复蒸汽循环时长期贴近耐热上限 | 耐热与耐辐照是硬线 |
| 载荷 | 与芯杆滑动配合，控制推注阻力；壁薄但不能被捏瘪 | 承重、堆叠、器械码放时的静载 | 尺寸精度、环刚度 |
| 介质 | 接触注射剂药液；外表面擦拭消毒 | 接触器械、擦拭与浸泡消毒 | 耐药液相容、耐消毒剂 |
| 寿命 | 一次性使用，但货架期以年计 | 一次性或复用清洗后复用，按注册类别定 | 析出与性能不得随货架期漂移 |
| 外观 | 雾度 ≤15%（YY/T 0242）；辐射后（25 kGy）黄变指数 ≤20 | 本色或半透，色度稳定、不脱屑 | 透明可视、洁净 |
| 合规 | 医疗器械；ISO 10993 / GB/T 16886 系列 | 同左，复用类另看清洗验证 | 生物学评价 + 化学表征 |
六维里温度和外观是"一票否决"性质的两维：温度决定 PP 要往耐辐照还是耐蒸汽两个完全不同的方向配，外观里的雾度与黄变直接决定注射器能不能看清药液与气泡。
一个内行细节：辐照剂量不是越高越保险。公开资料（A 级）给出的常见做法是把剂量由 25 kGy 降至 15 kGy 来压低黄变与脆化；电子束替代 γ 射线氧化更少，氮气氛围也能减缓氧化。同一款料，25 kGy 与 15 kGy 出来的色差和保留强度可能差出一大截——这一点灭菌工艺文件里要写死。
二、材料路线对比：医用PP、PVC、PETG 与 PC/玻璃，各管哪类件
核心结论：医用透明件不是"谁更好"的题，是"谁能避开哪条短板"的分工题，PP 的强项是合规与可回收，短板是天然半透与辐照略黄。
医用件的材料路线，PP 只在其中一块，和 PVC、PETG、PC、COC/COP、玻璃各有分工，只做陈述不排优劣。
| 路线 | 透明与灭菌特点 | 主要顾虑 | 典型用途 |
|---|
| 医用 PP | 半透（透明牌号雾度 ≤15%）；γ / EO / 蒸汽均可 | 辐照略黄变、刚性靠填充 | 注射器、硬质容器、托盘 |
| 医用 PVC | 透明度优；γ / EO / 蒸汽 | 含增塑剂，DEHP 析出争议 | 导管、血袋、管路 |
| PETG | 透明度优，耐辐照不黄变 | 耐热有限，高温灭菌受限 | 包装、诊断件 |
| PC | 透明、强度高 | 耐水解与某些介质相容性受限 | 部分需强度的器械 |
| COC/COP | 高透明、低析出、耐辐照 | 成本与韧性的平衡 | 诊断、高端包装 |
| 玻璃 | inert、可视 | 重量与破损 | 注射液瓶、高端 |
第三行是 PP 的位置。它的合规优势与可回收属性，是它在医用场景持续被讨论的原因；短板也很明确——PP 天生不完全透明，靠成核剂把球晶细化到光波长以下才能做透明，而医用对成核剂本身的可选范围收得更紧。
文字版结论：三条主流透明路线里，PVC 因成本与透明度仍占输注管最大份额，PETG 耐辐照不黄变但耐热有限，PP 合规好但辐照略黄。选哪条，看这个件最怕的是"黄变""耐热"还是"增塑剂析出"，而不是看谁更"高级"。
三、★ 选型判据表：注射器外套与手术托盘的八项门限，每项带验证方法
核心结论：医用 PP 的判据不是一条，是八项，而且每一项都必须带着"怎么测、测到多少算过"一起看，否则选型等于没选。
下面这张表是全篇最该收藏的部分，注意第四列"验证方法·标准号"。
| 指标 | 门限值（典型） | 验证方法 · 标准号 | 常见失效 | 通行解法 |
|---|
| 雾度 / 透明度 | 透明牌号雾度 ≤15% | YY/T 0242-2007；实测按实际壁厚与成型条件 | 看不清药液与气泡 | 成核体系细化球晶 |
| 尺寸精度与同心度 | 与芯杆配合的公差稳定 | 全尺寸测量；按产品标准 | 推注阻力漂移、密封下降 | 控收缩、稳结晶 |
| 滑动性能 | 与硅化匹配，阻力稳定 | 滑动阻力试验；产品标准 | 过紧卡滞或过松泄漏 | 硅油残留与相容管控 |
| 环刚度 / 耐捏瘪 | 薄壁不被捏瘪、不变形 | 环刚度 / 压瘪试验 | 握持变形、装配失效 | 适度填充保刚性 |
| 辐射后黄变 | 辐射后（25 kGy）黄变指数 ≤20 | YY/T 0242-2007 | 辐照后发黄发脆 | 耐辐照稳定体系 |
| 生物相容性 | 细胞毒性 / 致敏 / 刺激等按分类做 | ISO 10993 / GB/T 16886 系列 | 评价项目不全被退评 | 先定接触分类 |
| 化学表征 / 可萃取物 | 先表征再定生物学范围 | ISO 10993-18 / GB/T 16886.18 | 未知析出被漏检 | 萃取 + 毒理评估 |
| 耐化学消毒剂 | 擦拭 / 浸泡后无开裂发白 | 消毒剂接触试验 | 表面发白、应力开裂 | 耐介质体系 |
文字版结论：八项里辐射后黄变和滑动性能是最容易被临时补、却最该先定的两项——前者跟着灭菌方式走，后者跟着硅化工艺走，都必须在选型阶段就锁定，而不是试产时才发现。把这张表当体检单，缺一项不判合格，比样件试出来再回头找原因省钱得多。
四、灭菌方式决定配方：EO、辐照、蒸汽三路，对 PP 的材料后果完全不同
核心结论：PP 的配方必须跟着灭菌方式走——同一款料换一种灭菌，结果可能完全不同，"选个医用级牌号就行"是误解。
这是本篇的核心对照。三种主流灭菌对 PP 的材料后果，列成一张可查表。
| 灭菌方式 | 温度与原理 | 对 PP 的材料后果（代价） | 对配方的要求 | 何时不宜 |
|---|
| 环氧乙烷 EO | 常温气相，对材料温和 | 残留解析周期长；EO 及 2-氯乙醇、乙二醇等残留须落在 ISO 10993-7（GB/T 16886.7）容许限量内 | 几乎不挑 PP 基体，但透气包装与解析工艺要稳 | 急交付、解析场地受限 |
| 辐照（γ / 电子束） | 常温，效率高、无残留 | PP 在辐照下断链与氧化，表现为黄变与变脆 | 必须上耐辐照稳定体系 | 要求高透明又高剂量辐照 |
| 蒸汽高温（高压蒸汽） | 常到 134℃、多次循环 | 尺寸变化、雾化、变形，对 PP 耐热上限是硬考验 | 按高耐热、低析出配 | 长期 120℃ 以上反复蒸汽 |
先把辐照黄变的机理讲清（素材库核心专题）：高能射线优先打断 PP 主链 C–C 键，分子量下降 → 断裂伸长率与冲击强度下降；氧化生成共轭双键发色团 → 黄变。通用 PP 的断链速率远高于交联，所以表现就是又黄又脆。
四条对策（可直接落地）：
1. 配方：主抗氧剂（受阻酚）+ 辅助抗氧剂（亚磷酸酯）+ HALS；⚠️ 避免酚类抗氧剂与 HALS 并用——会产生深黄，这是反直觉的点。
2. 结构：无规共聚引入 2–3% 乙烯降低结晶度，促进自由基复合；选窄分子量分布树脂。
3. 工艺：电子束替代 γ 射线（氧化更少）、氮气氛围、剂量由 25 kGy 降至 15 kGy。
4. 耐受水平参考：未稳定 PP 约 20 kGy；辐射稳定 PP 可达 20–50 kGy；公开资料（A 级）以燕山石化 K4912R 为例，50 kGy 后拉伸强度保留率 >90%。
文字版结论：灭菌方式与配方是绑定的。选辐照就要按辐照稳定体系配，选蒸汽就要按高耐热配，选 EO 则几乎不挑基体但要管住残留与解析。把"灭菌方式"当成最后一步来定，是医用 PP 件最常见、也最贵的返工来源。
五、常见失效与根因：黄变、脆化、不脱屑，三条根因与一处必须否定的做法
核心结论：医用 PP 件三大失效——辐照黄变脆化、滑动阻力漂移、不脱屑——根因几乎都不在"料差了"，而在灭菌方式与配方没对齐。
失效一：辐照后发黄发脆。 根因是配方没按辐照稳定体系配，或酚类抗氧剂与 HALS 并用产生了深黄；剂量偏高又放大了断链。先查灭菌剂量与稳定体系，再查料。
失效二：滑动阻力漂移、漏液。 根因在外筒内径公差与硅化处理不一致——硅油残留量、喷涂均匀度、与 PP 的相容性都影响推注手感。这不是"料够不够滑"，是尺寸与硅化两件事没对齐。
失效三：表面脱屑、擦拭发白。 根因在析出物与耐消毒剂介质不足，或填料分布不均。洁净件上，脱屑与析出是独立的合规判据，不能拿"粒子洁净"当挡箭牌。
★ 必须否定的一处常见做法：很多人以为"医用 PP 都一样，选个医用级牌号就行"。错。医用级牌号解决的是基材洁净与可追溯，不解决"灭菌方式对应的配方后果"——同一款医用级 PP，走 EO 没问题，走 25 kGy 辐照可能整批发黄，走 134℃ 反复蒸汽可能变形。牌号相同，灭菌方式不同，结果可以完全两样。
六、验证顺序：先定灭菌与接触分类，再定体系，灭菌后必须复测
核心结论：验证顺序最该先定的是"灭菌方式 + 接触分类"，而灭菌后的性能复测是不可省略的一步——只测灭菌前，等于没测。
这一段同行几乎没人写，但它是换料能不能省钱、能不能过注册的关键。顺序错了，问题会在最后一步集中爆出来。
`
① 定灭菌方式与接触分类 表面/外部接入/植入 × 短期/长期/持久
↓ 这两步不定，后面全是猜
② 定材料体系 耐辐照 or 高耐热；透明/刚性取向
↓ 体系不对，后面全返工
③ 灭菌后性能复测 外观黄变、力学、尺寸——必须灭后再测
↓ 这一步不过，前面白做
④ 化学表征与可萃取物 先表征，再定生物学试验范围
↓
⑤ 生物学评价 细胞毒性/致敏/刺激/急性毒性等按分类
↓
⑥ 装配与滑动性能 硅化、配合、阻力
↓
⑦ 整机与临床前验证
`
每一步都有"不过就退回上一级"的判据。最常见的错误是跳过 ③——只测灭菌前的粒料典型值，拿去量产，灭菌后整批发黄或变形才暴露。灭菌后的复测，是医用 PP 件和工业件最本质的区别之一。
文字版结论：验证顺序是 分类 → 体系 → 灭菌后复测 → 表征 → 生物学 → 装配 → 整机。灭菌后复测这关必须放在生物学评价之前，因为它最可能一票否决，过了它再做合规侧的事，才不会白花验证费。
七、反向诚实：长期 120℃ 以上反复蒸汽、高剂量辐照且要透明，这类件不该用改性PP
核心结论：遇到"长期高温反复蒸汽""高剂量辐照且必须高透明""极高阻隔"三件事之一，这个件就不该硬撑改性 PP，要换路线。
讲完能做的，必须讲不能做的。这一段对选型判断的价值最高。
| 出现的情况 | 为什么改性PP不合适 | 该往哪走 |
|---|
| 要求长期 120℃ 以上反复蒸汽灭菌 | PP 耐热上限就在那条线附近，反复循环的尺寸变化与雾化难压住 | 换更高耐热的工程塑料或金属器械 |
| 要求必须耐高剂量辐照且要求透明 | 辐照黄变与透明是反方向，耐辐照体系也要牺牲部分透明 | 走 PETG、COC/COP 等耐辐照不黄变路线 |
| 要求极高阻隔（如长期避光避氧药液） | PP 本征阻隔有限，靠改性提升幅度有限 | 走多层共挤、铝箔/PA 复合或玻璃 |
| 复用件要求频繁高温清洗消毒 | 反复热循环下尺寸与刚性衰减明显 | 按复用类别走更高耐温材料 |
规律是一致的：只要出现"两个方向相反的要求同时要"，就说明这个件不该用 PP 硬撑。 遇到这种情况，我们的做法是先把这条讲清楚，再谈有没有折中空间——硬接下来的单子，最后都要用返工和索赔还回去。
八、换料风险清单：从模具收缩率到灭菌后复测，七项先看再动
核心结论：决定试医用改性PP之前，要动的不是性能，是模具、工艺与验证顺序三块，其中最该先谈的是灭菌后复测。
| 要动的项 | 需要确认什么 | 不做会怎样 |
|---|
| 模具收缩率 | 新料收缩率与原方案差，薄壁件尤其敏感 | 尺寸超差，与芯杆配合失效 |
| 浇口与排气 | 透明料对浇口、排气更敏感 | 熔接线、气痕、透明件发雾 |
| 料温与模温 | 透明/成核体系工艺窗口不同 | 结晶不均、雾度超标 |
| 干燥 | 按具体体系定 | 银丝、气泡 |
| 保压与脱模 | 薄壁件顶出易拉伤 | 变形、顶白 |
| 色差 | 医用件色板先确认 | 批次色差争议 |
| 验证顺序 | 先小样 → 灭菌后复测 → 短射 → 批量 | 风险全部压到最后一步集中爆发 |
文字版结论：换料要动的是模具、工艺、色差三块，其中最该先谈的是验证顺序里的"灭菌后复测"。跳过小样直接试模，等于把成本提前花出去；跳过灭菌后复测直接批量，一次失败就是整批报废——医用件上这比工业件贵得多。
九、一页纸汇报表：注射器外套与手术托盘，直接贴进技术评审
核心结论：这张表让技术员能把结论直接往上报，不必重新组织语言——判断标准只有一条，客户拿它能不能在一次会里把材料方向定下来。
| 场景 | 推荐路线 | 关键指标 | 验证标准 | 需先确认的条件 |
|---|
| 注射器外套（辐照灭菌） | 医用无规共聚 PP + 耐辐照稳定体系 + 成核透明 | 雾度 ≤15%；辐射后黄变指数 ≤20（25 kGy） | YY/T 0242-2007；ISO 10993-5/10 | 灭菌剂量、硅化工艺 |
| 注射器外套（EO 灭菌） | 医用透明 PP，几乎不挑基体 | 雾度 ≤15%；EO 残留限量 | YY/T 0242；ISO 10993-7 | 解析周期与场地 |
| 注射器外套（蒸汽灭菌） | 高耐热、低析出 PP 体系 | 134℃ 循环后尺寸/外观稳定 | 产品标准 + 蒸汽循环试验 | 是否反复循环 |
| 手术托盘（一次性） | 医用均聚/共聚 PP，洁净低析出 | 尺寸稳定、不脱屑、耐消毒剂 | ISO 10993 系列；消毒剂接触 | 接触分类（表面/短期） |
| 手术托盘（复用清洗） | 更高耐温 PP 或换材料 | 反复热循环后不变形 | 复用清洗验证 | 清洗温度与次数 |
文字版结论：这张表的作用是让技术员把"灭菌方式 + 接触分类"两个前提一次性报齐，再往下推材料方向。前提没报齐就定料，是医用件选型返工率最高的动作。
十、这个件上最容易出问题的，往往不是料：科隆现场与三个问题
医用 PP 件上行业最常见的早期失效是辐照黄变与滑动阻力漂移，而这两类问题里，由材料本身引起的比例并不高。辐照黄变的判据在标准里写得很清楚：辐射后（25 kGy）黄变指数要落在 YY/T 0242-2007 的门限内，机理是射线打断主链、氧化生成发色团；通行解法是耐辐照稳定体系 + 成核 + 控制剂量与氛围。滑动阻力漂移则多半要从尺寸公差与硅化工艺上找原因。
行业通行的做法，是把"灭菌方式"和"接触分类"这两件前提先定下来，再定基材档位、透明体系与稳定剂方向——顺序反了，问题会一直漂。
这里要讲清一个责任边界：材料供应商能做的是提供配方层面的低析出与批次一致性，生物学评价的主体责任在器械企业。 我们做的是材料侧的方案建议与数据支持，把边界条件讲清楚，方便你们与检测方对接。
宁波市科隆新材料有限公司在这个方向上常供的是医用方向的 PP 基材与改性粒子，覆盖透明化、耐辐照稳定、低析出等方向，按客户的产品标准与灭菌方式给出基材档与助剂方向的建议，主要用来解决上面说的"灭菌方式与配方没对齐"这一类问题；配方按件的工况调，可以配合做小样比对与试模。
常见问答
问：辐照后的注射器外套发黄，是不是料不行？
答：多半是配方没按辐照稳定体系配，或者酚类抗氧剂与 HALS 并用产生了深黄。先查灭菌剂量和稳定体系，再看料的耐辐照档位——这是配方问题，不是"料变差了"。
问：EO 灭菌和辐照怎么选更省心？
答：EO 对材料温和、几乎不挑 PP 基体，但残留解析周期长、要管住限量；辐照效率高无残留，但必须上耐辐照配方。选哪个，看你的交付节奏和件对透明的容忍度，不是看哪个"更先进"。
问：生物相容性评价过了，是不是合规工作就完成了？
答：不是。生物相容性只是其中一环，化学表征/可萃取物、灭菌后的状态、脱模剂与批次追溯都要一并覆盖。把一环当成全部，是医用选材里最常见的简化。
| 工况 | 关键判据 | 科隆常规供应 |
|---|
| 注射器外套（辐照） | 辐射后黄变指数 ≤20（25 kGy）；雾度 ≤15% | 医用无规共聚 PP + 耐辐照稳定体系方向 |
| 注射器外套（EO/蒸汽） | EO 残留限量 / 134℃ 循环稳定 | 医用透明 PP，按灭菌方式调体系 |
| 手术托盘 | 不脱屑、耐消毒剂、尺寸稳定 | 医用均聚/共聚 PP，低析出方向 |
想提醒一句：件出问题，最常见的错法是先换料。黄变、滑动漂移、脱屑——每一条的原因都不止一个。先定位，再换料；顺序反了，往往换了几轮还在原地。
最后说三句
第一，医用件的门槛是两道，不是一道。 生物学评价决定能不能接触人体，灭菌方式决定灭完还合不合格，后者更常被漏掉。
第二，PP 的配方必须跟着灭菌方式走。 同一款医用级料，换一种灭菌可能结果完全不同——选辐照就按耐辐照配，选蒸汽就按高耐热配。
第三，灭菌后必须复测，只测灭菌前等于没测。 外观黄变、力学、尺寸，灭完再测一遍，这一关要放在生物学评价之前。
下一篇讲输液容器——那个件更怕的不是黄变，是透明度与耐灭菌的再平衡。
关于我们
一颗 PP 粒子出厂时，只是一颗粒子。
它变成注射器外套、手术托盘、输液瓶，中间隔着一整套方案——基材选哪档、成核怎么加、稳定体系怎么配、灭菌方式跟着怎么走、析出与批次一致性怎么压住。
宁波市科隆新材料有限公司，自产改性聚丙烯（PP）造粒，覆盖均聚 / 无规共聚 / 抗冲共聚三档基材，以及透明化、耐辐照稳定、低析出、填充、玻纤增强、增韧、阻燃、低气味低 VOC、耐候、免喷涂耐划伤等改性方向；兼营各大石化厂 PP 树脂、副牌料与大包料。
Modified PP is used in syringe barrels and surgical trays, with two main thresholds: biological evaluation determines whether it can come into contact with the human body, and the sterilization method determines whether it is still qualified after sterilization — the latter is often overlooked. This article explains the contact classification and chemical characterization path according to ISO 10993, and provides a reference table comparing the effects of EO, radiation, and steam sterilization on PP materials.
A customer once asked a question: 'We have always used a medical-grade PP for syringe barrels. After switching to another sterilization factory and using irradiation, why does the entire batch turn yellow and brittle?'
This sentence contains a repeatedly verified judgment: there are two thresholds for medical devices—the biological evaluation (whether it can come into contact with the human body) and the sterilization method (whether it still meets standards after sterilization), and the second one is more often overlooked.
Many teams put all their energy into biocompatibility, and the sterilization method is only decided when approaching mass production. As a result, even though the material is the same, changing the sterilization method completely alters the appearance and mechanical properties. Below, I will explain these two lines, three sterilization methods, and eight criteria in order.
1. Analysis of six operational dimensions: The six numbers for the syringe outer casing and the surgical tray should be reported together first before selecting the model.
Core conclusion: Medical PP belongs to the category of modified PP with the strictest requirements for cleanliness and extractables, and in the six-dimensional working conditions, the temperature and appearance dimensions directly determine the direction of the formulation.
Break the operating conditions of these two parts into six dimensions, and report the specific numbers for each item; only then can the material direction hold.
| Dimension | Actual operating conditions of the syringe cover | Actual working conditions of the surgical tray | Requirements for the materials |
|---|
| Temperature | Sterilization temperature: EO at room temperature, irradiation at room temperature, steam usually up to 134°C; storage at room temperature | Same as the left, and repeatedly close to the heat-resistant limit during long-term steam cycles | Heat resistance and radiation resistance are hard lines |
| Load | Slides with the core rod, controlling the injection resistance; the wall is thin but should not be pinched flat | Static load during bearing, stacking, and equipment stacking | Dimensional accuracy, ring stiffness |
| Medium | Contact injectable solution; wipe the outer surface for disinfection | Handling equipment, wiping and soaking disinfection | Resistant to drugs in liquid form, resistant to disinfectants |
| Lifespan | For single use, but the shelf life is measured in years | Single-use or reusable after cleaning and reuse, according to the registered category | Precipitation and performance must not drift during shelf life |
| Appearance | Haze ≤ 15% (YY/T 0242); yellowness index after irradiation (25 kGy) ≤ 20 | Natural color or semi-transparent, color stability, does not flake | Transparent and clean |
| Compliance | Medical devices; ISO 10993 / GB/T 16886 series | Same as the left, for reusable classes see cleaning and verification | Biological Evaluation Chemical Characterization |
In six dimensions, temperature and appearance are two dimensions with a 'veto' nature: temperature determines whether PP should be formulated in the completely different directions of radiation resistance or steam resistance, and the haze and yellowing in appearance directly determine whether the syringe can clearly see the liquid and bubbles.
An insider detail: a higher irradiation dose is not necessarily safer. According to publicly available information (Class A), a common practice is to reduce the dose from 25 kGy to 15 kGy to lessen yellowing and embrittlement; using an electron beam instead of γ-rays results in less oxidation, and a nitrogen atmosphere can also slow down oxidation. For the same material, the color difference and retained strength between 25 kGy and 15 kGy can be significant — this must be explicitly documented in the sterilization process files.
2. Material route comparison: medical PP, PVC, PETG, and PC/glass, which type of components for each tube
Core conclusion: Medical transparent components are not a matter of 'who is better,' but a matter of 'who can avoid which shortcomings.' PP's strengths are compliance and recyclability, while its shortcomings are natural semi-transparency and slight yellowing after irradiation.
The material route for medical parts: PP is only used in one part, while PVC, PETG, PC, COC/COP, and glass each have their respective roles. This is just a statement without ranking their pros or cons.
| Route | Transparency and Sterilization Features | Main concern | Typical uses |
|---|
| Medical PP | Semi-transparent (transparency grade haze ≤15%); γ / EO / steam all acceptable | Irradiation slightly yellowed, rigidity relies on filling | Syringes, rigid containers, trays |
| Medical PVC | Good transparency; γ / EO / vapor | Contains plasticizers, DEHP leaching controversy | Catheters, blood bags, tubing |
| PETG | Excellent transparency, resistant to radiation without yellowing | Limited heat resistance, high-temperature sterilization is restricted | Packaging, diagnostic parts |
| PC | Transparent, high strength | Limited hydrolysis resistance and compatibility with certain media | Equipment that requires partial strength |
| COC/COP | High transparency, low precipitation, radiation resistant | Balance between cost and resilience | Diagnosis, high-end packaging |
| Glass | inert, visible | Weight and Damage | Injection vial, high-end |
The third row is the position of PP. Its compliance advantages and recyclability are the reasons why it continues to be discussed in medical scenarios; its shortcomings are also very clear — PP is inherently not completely transparent, and it can only be made transparent by refining the spherulites below the wavelength of light with nucleating agents, while the range of nucleating agents that can be chosen for medical use is more restricted.
Text version conclusion: Among the three mainstream transparent options, PVC still occupies the largest share in infusion tubing due to cost and transparency, PETG resists radiation and yellowing but has limited heat resistance, and PP is compliant but turns slightly yellow under radiation. Which one to choose depends on whether the part is most concerned with 'yellowing,' 'heat resistance,' or 'plasticizer migration,' rather than which is more 'premium.'
3. ★ Selection Criteria Table: Eight thresholds for the syringe sleeve and surgical tray, each with a validation method
Core conclusion: The criteria for medical PP are not just one item, but eight, and each one must be considered along with 'how to test it and how much counts as passing'; otherwise, selecting a type is equivalent to not selecting at all.
The table below is the part of the whole text most worth saving; pay attention to the fourth column 'Verification Method · Standard Number'.
| Indicator | Threshold Value (Typical) | Verification Method · Standard Number | Common Failures | Common solution |
|---|
| Fog density / Transparency | Haze of transparent grade ≤15% | YY/T 0242-2007; actually measured according to the actual wall thickness and forming conditions | Cannot clearly see the medicine and bubbles | Refined spheroidal crystals in the nucleation system |
| Dimensional Accuracy and Concentricity | Tolerance stable when matched with the mandrel | Full-size measurement; according to product standards | Thrust resistance drift, seal drop | Control shrinkage, stabilize crystallization |
| Sliding performance | Matched with silicification, resistance is stable | Sliding resistance test; product standards | Too tight causing jamming or too loose causing leakage | Silicone oil residue and compatibility control |
| Ring stiffness / Crush resistance | Thin-walled does not get pinched or deformed | Ring Stiffness / Flattening Test | Grip deformation, assembly failure | Moderate filling ensures rigidity |
| Yellowing after radiation | After irradiation (25 kGy) yellowness index ≤20 | YY/T 0242-2007 | Yellowing and becoming brittle after irradiation | Radiation-resistant stable system |
| Biocompatibility | Cytotoxicity / Sensitization / Stimulation, etc., categorized accordingly | ISO 10993 / GB/T 16886 series | Returned for review due to incomplete evaluation items | First, determine the contact classification |
| Chemical Characterization / Extractables | Characterize first, then define the biological scope | ISO 10993-18 / GB/T 16886.18 | Unknown precipitate was missed | Extraction Toxicological Evaluation |
| Resistant to chemical disinfectants | No cracking or whitening after wiping/soaking | Disinfectant Contact Test | Surface whitening, stress cracking | Media-resistant system |
Text version conclusion: Among the eight items, post-irradiation yellowing and sliding performance are the two that are most easily patched temporarily but should be determined first—the former follows the sterilization method, the latter follows the silicification process. Both must be locked in during the selection phase, not discovered during trial production. Treat this table like a medical checkup report; missing any item means failing. This is much more cost-effective than producing a sample first and then going back to find the cause.
4. Sterilization method determines the formulation: EO, irradiation, and steam have completely different effects on PP material.
Key conclusion: The formulation of PP must follow the sterilization method—using the same material with a different sterilization method can yield completely different results. The idea of 'just choosing a medical-grade grade is enough' is a misunderstanding.
This is the core comparison of this article. The consequences of three mainstream sterilization methods on PP material are listed in a reference table.
| Sterilization method | Temperature and Principle | Material consequences (cost) for PP | Requirements for the formula | When not suitable |
|---|
| Ethylene Oxide (EO) | Room temperature gas phase, gentle on materials | The residue degradation cycle is long; residues of EO, 2-chloroethanol, ethylene glycol, etc. must be within the permissible limits of ISO 10993-7 (GB/T 16886.7). | Almost not picky about the PP substrate, but the breathable packaging and parsing process need to be stable | Urgent delivery, limited site for analysis |
| Irradiation (γ / electron beam) | Room temperature, high efficiency, no residue | PP undergoes chain scission and oxidation under irradiation, resulting in yellowing and embrittlement. | Must use radiation-resistant stable system | Requires high transparency and high-dose irradiation |
| Steam at high temperature (high-pressure steam) | Frequently reaches 134°C, multiple cycles | Changes in size, atomization, and deformation are a tough test for the heat resistance limit of PP. | Matched for high heat resistance and low precipitation | Repeated steam above 120°C for long periods |
First, clarify the mechanism of radiation-induced yellowing (core topic of the material library): high-energy rays preferentially break the C–C bonds in the PP main chain, resulting in decreased molecular weight → reduced elongation at break and impact strength; oxidation generates conjugated double bonds that form chromophores → yellowing. The chain scission rate of general PP is much higher than crosslinking, so it appears both yellow and brittle.
Four countermeasures (can be implemented directly):
1. Formulation: Primary antioxidant (hindered phenol) Secondary antioxidant (phosphite) HALS; ⚠️ Avoid using phenolic antioxidants together with HALS — it will cause deep yellowing, which is a counterintuitive point.
2. Structure: Introducing 2–3% ethylene through random copolymerization reduces crystallinity and promotes free radical recombination; select resins with a narrow molecular weight distribution.
3. Process: Electron beam replacing γ rays (less oxidation), nitrogen atmosphere, dose reduced from 25 kGy to 15 kGy.
4. Reference for tolerance levels: Unstabilized PP about 20 kGy; radiation-stabilized PP can reach 20–50 kGy; according to public information (Class A), taking Yanshan Petrochemical K4912R as an example, the tensile strength retention rate after 50 kGy is >90%.
Textual conclusion: The sterilization method is linked to the formulation. If you choose irradiation, you have to match it with an irradiation-stable system; if you choose steam, you need a high heat-resistant formulation; if you choose EO, it is almost indifferent to the substrate but you must control residues and decomposition. Treating 'sterilization method' as the final step is the most common and also the most expensive source of rework for medical PP parts.
5. Common failures and root causes: yellowing, embrittlement, no flaking; three root causes and one practice that must be ruled out
Core conclusion: The three major failures of medical PP components—radiation yellowing and embrittlement, drift in sliding resistance, and no flaking—are almost never due to 'poor material quality,' but rather due to misalignment between sterilization methods and formulation.
Failure 1: Yellowing and becoming brittle after irradiation. The root cause is that the formulation was not designed according to the radiation-stable system, or combining phenolic antioxidants with HALS produced a deep yellow color; a high dose further amplified chain scission. First, check the sterilization dose and the stabilizing system, then check the materials.
Failure 2: Sliding resistance drift and leakage. The root cause lies in the inconsistency between the inner diameter tolerance of the outer cylinder and the silicification treatment—the amount of silicone oil residue, the uniformity of spraying, and compatibility with PP all affect the pushing feel. This is not about 'whether the material is slippery enough'; it is that the dimensions and silicification are not aligned.
Failure 3: Surface flaking and whitening upon wiping. The root cause lies in insufficient interaction between precipitates and disinfectant-resistant medium, or uneven distribution of fillers. On clean parts, flaking and precipitation are independent compliance criteria and cannot be shielded by claiming 'particle cleanliness'.
★ A common misconception that must be rejected: Many people think, 'All medical-grade PP is the same, just pick a medical-grade specification.' Wrong. Medical-grade specifications ensure the purity of the base material and traceability, but they do not address 'the consequences of the formulation under different sterilization methods'—the same medical-grade PP can be fine with EO sterilization, may turn yellow when exposed to 25 kGy irradiation, and may deform under repeated steam at 134℃. The specification may be the same, but different sterilization methods can result in completely different outcomes.
6. Verification sequence: first determine sterilization and contact classification, then determine the system; re-testing is required after sterilization
Core conclusion: The verification sequence should prioritize determining the 'sterilization method and contact classification,' and re-testing performance after sterilization is an indispensable step—only testing before sterilization is equivalent to not testing at all.
Almost no peers write this section, but it is key to whether changing materials can save money and pass registration. If the order is wrong, problems will all come up at the final step.
`
① Determine sterilization method and contact classification: Surface/External access/Implant × Short-term/Long-term/Permanent
↓ These two steps are uncertain, everything that follows is just a guess
② Determine the material system: radiation-resistant or high heat-resistant; transparent/rigid orientation
↓ The system is wrong, everything will have to be redone later
③ Performance retesting after sterilization Appearance yellowing, mechanical properties, dimensions — must be measured again after sterilization
↓ If this step fails, the previous efforts were wasted
④ Chemical characterization and extractables Characterize first, then determine the scope of biological testing
↓
⑤ Biological Evaluation: Cytotoxicity/sensitization/irritation/acute toxicity, etc., according to classification
↓
⑥ Assembly and sliding performance Siliciding, fitting, resistance
↓
⑦ Whole machine and preclinical validation
`
Every step has the criterion of 'just return to the previous level.' The most common mistake is skipping ③—only testing the typical values of the granules before sterilization, then taking them to mass production, and it is only when the entire batch yellows or deforms after sterilization that the issue is exposed. Retesting after sterilization is one of the most fundamental differences between medical PP parts and industrial parts.
Text version conclusion: The verification sequence is Classification → System → Post-sterilization retest → Characterization → Biology → Assembly → Complete device. The post-sterilization retest must be done before the biological evaluation, because it is most likely to result in a total rejection. If it passes, then conducting compliance-related tasks will not waste verification costs.
7. Reverse honesty: Items that are repeatedly exposed to steam above 120°C for a long time, high-dose irradiation, and need to be transparent should not use modified PP.
Core conclusion: When encountering any one of the following three situations: 'long-term high temperature with repeated steam,' 'high-dose irradiation and must be highly transparent,' or 'extremely high barrier,' you should not forcefully modify PP; you need to change the route.
After explaining what can be done, you must explain what cannot be done. This part has the highest value for making selection judgments.
| The situation that occurred | Why is modified PP not suitable? | Which way should I go? |
|---|
| Requires repeated steam sterilization at above 120℃ for a long period | The heat resistance limit of PP is around that line, and the repeated cyclical dimensional changes and atomization are hard to suppress. | Switch to higher heat-resistant engineering plastics or metal instruments |
| It must withstand high-dose irradiation and be transparent. | Irradiation yellowing and transparency are in opposite directions, and radiation-resistant systems also have to sacrifice some transparency. | Pursue radiation-resistant, non-yellowing paths such as PETG and COC/COP |
| Requires extremely high barrier (such as long-term light- and oxygen-sensitive medicinal solution) | PP's intrinsic barrier is limited, and the improvement achieved through modification is also limited. | Multilayer co-extrusion, aluminum foil/PA composite, or glass |
| Reusable parts require frequent high-temperature cleaning and disinfection | Significant decay in size and rigidity under repeated thermal cycling | Use higher temperature-resistant materials according to reuse category |
The pattern is consistent: whenever 'two opposite requirements must be met at the same time' appear, it indicates that this part should not be forcibly made with PP. In such cases, our approach is to first clarify this point, and then discuss whether there is room for compromise—orders that are forcibly pushed through will eventually require rework and claims to be returned.
VIII. Material Change Risk List: From mold shrinkage rate to post-sterilization retesting, review all seven items before taking action
Core conclusion: Before deciding to try medical-grade modified PP, the aspects to address are not the performance, but the mold, process, and verification sequence; among these, the one that should be discussed first is retesting after sterilization.
| Items to move | What needs to be confirmed | What will happen if I don't do it? |
|---|
| Mold shrinkage rate | The shrinkage rate of the new material differs from the original plan, and thin-walled parts are particularly sensitive | Dimension out of tolerance, fails to fit with the mandrel |
| Gate and Venting | Transparent materials are more sensitive to gates and venting | Weld lines, air marks, fogging of transparent parts |
| Material Temperature and Mold Temperature | Different process windows for transparent/nucleation systems | Uneven crystallization, excessive haze |
| Dry | Decided according to the specific system | Silver threads, bubbles |
| Pressure Holding and Demolding | Thin-walled parts are easily scratched during ejection | Distortion, Overexposure |
| Color difference | Medical parts color chart to be confirmed first | Batch color difference dispute |
| Verification order | First sample → Retest after sterilization → Short run → Mass production | All the risks are concentrated to explode at the final step |
Text version conclusion: Changing materials affects three areas: molds, processes, and color difference, among which the first thing to discuss should be the 'retest after sterilization' in the verification sequence. Skipping small samples and going straight to mold testing is like spending the cost in advance; skipping the retest after sterilization and going directly to mass production means that a single failure will result in the entire batch being scrapped — for medical parts, this is much more costly than for industrial parts.
9. One-page report form: syringe covers and surgical trays, directly included in the technical review
Core conclusion: This table allows technicians to report conclusions directly without having to reorganize their wording—the only criterion is whether the client can use it to finalize the material direction in a single meeting.
| Scene | Recommended Route | Key indicators | Verification Standard | Conditions that need to be confirmed first |
|---|
| Syringe cover (irradiation sterilization) | Medical random copolymer PP, radiation-resistant stable system, nucleated and transparent | Haze ≤15%; yellowness index after radiation ≤20 (25 kGy) | YY/T 0242-2007; ISO 10993-5/10 | Sterilization dose, silicidation process |
| Syringe cover (EO sterilized) | Medical-grade transparent PP, hardly selective of substrates | Fog density ≤15%; EO residue limit | YY/T 0242; ISO 10993-7 | Analysis Period and Site |
| Syringe cover (steam sterilization) | High heat-resistant, low-exudation PP system | Dimensions/appearance stable after 134℃ cycle | Product Standard Steam Circulation Test | Whether to repeat the cycle |
| Surgical tray (disposable) | Medical homopolymer/copolymer PP, clean with low extractables | Dimensionally stable, does not flake, resistant to disinfectants | ISO 10993 series; contact with disinfectants | Contact classification (surface/short-term) |
| Surgical tray (reuse cleaning) | Higher temperature-resistant PP or material replacement | No deformation after repeated heat cycling | Reuse cleaning verification | Cleaning temperature and frequency |
Text version Conclusion: The purpose of this table is to have technicians report all two prerequisites of "sterilization method + contact classification" at once, then push down the material direction. Placing materials without all prerequisites is the highest rework rate in medical component selection.
10. The most common problem with this part is often not the material: Cologne site and three issues
Medical PP The most common early failures in the industry are irradiation yellowing and sliding resistance drift, and among these two types of issues, the proportion caused by the material itself is not high. The criteria for irradiation yellowing are clearly stated in the standard: the yellowing index after radiation (25 kGy) must fall within the YY/T 0242-2007 threshold, with the mechanism being rays breaking the main chain and oxidizing to form chromophores; The common solution is irradiation-resistant stabilization system + nucleation + controlling dosage and atmosphere. Sliding resistance drift mostly depends on dimensional tolerances and siliconization processes.
The industry's common approach is to first define the two prerequisites of "sterilization method" and "contact classification," then set the substrate level, transparent system, and stabilizer direction—if the order is reversed, the problem will keep drifting.
Here, a clear responsibility boundary is clarified: what material suppliers can do is provide low precipitation and batch consistency at the formulation level; the main responsibility for biological evaluation lies with device companies. What we do is provide solution recommendations and data support on the material side, clarifying boundary conditions to facilitate liaison between you and testing parties.
Ningbo Kelong New Materials Co., Ltd. commonly supplies medical-grade PP substrates and modified particles in this direction, covering transparency, radiation stability, low precipitation, and other directions. Based on customer product standards and sterilization methods, we provide recommendations on substrate grades and additives, mainly to solve the problem of "mismatch between sterilization method and formulation"; Formulas can be adjusted according to the working conditions of the parts and can be used for sample comparison and mold trials.
FAQ
Q: If the injection casing turns yellow after irradiation, is it due to poor material?
Answer: Most often, the formula is not formulated according to the irradiation stabilization system, or phenolic antioxidants combined with HALS produce deep yellow. First, check the sterilization dose and stable system, then check the radiation tolerance level of the material—this is a formulation issue, not a "material deterioration ."
Question: How to choose between EO sterilization and irradiation for a more worry-free solution?
A: EO is gentle with materials and almost unpicky about PP substrates, but the residue analysis cycle is long and limits must be controlled; Irradiation efficiency is high and residue-free, but you must use a radiation-resistant formula. Which one to choose depends on your delivery pace and tolerance for transparency, not which is "more advanced."
Question: If the biocompatibility evaluation has passed, does compliance work mean the work is done?
A: No. Biocompatibility is just one link; chemical characterization/extractables, post-sterilization status, release agents, and batch traceability must all be covered together. Treating one link as the whole is the most common simplification in medical material selection.
| Operating Conditions | Key Criteria | Cologne Conventional Supply |
|---|
| Syringe Jacket (Irradiation) | Post-Radiation Yellowing Index ≤20 (25 kGy); Hagginess ≤15% | Medical random copolymer PP + irradiation-resistant stabilized system direction |
| Syringe jacket (EO/steam) | EO Residual limit / 134°C circulation stable | Medical transparent PP, adjust the system according to sterilization |
| surgical tray | non-flaking, resistant to disinfectants, dimensional stable | Medical homopolymer/copolymer PP, low precipitation direction |
Just a reminder: when there are issues, the most common mistake is to change the material first. Yellowing, sliding drift, flaking—each has more than one cause. Position first, then change the material; If the order is reversed, you often end up in the same spot after several rounds.
Finally, three words
First, the threshold for medical parts is two, not one. Biological evaluation determines whether they can contact the human body; sterilization determines whether the product passes after sterilization, and the latter is often overlooked.
Second, PP formulas must follow the sterilization method. For the same medical-grade material, switching to one sterilization method can yield completely different results—if you choose irradiation, mix according to irradiation tolerance; if you choose steam, mix with high heat resistance.
Third, after sterilization, retesting is required; testing only before sterilization is equivalent to not testing at all. Appearance yellowing, mechanics, dimensions—test again after sterilization. This step should be taken before biological evaluation.
Next article will talk about infusion containers—what that unit fears more isn't yellowing, but the rebalancing of transparency and sterilization resistance.
About Us
A PP granule leaves the factory as just a particle.
It becomes a syringe cover, surgical tray, infusion bottle, with a whole set of solutions in between—which substrate to choose, how to add nucleation, how to stabilize the system, how to follow sterilization methods, how to ensure consistency between precipitation and batch.
Ningbo Kelong New Materials Co., Ltd. produces modified polypropylene (PP) pelletizing in-house, covering three grades of substrates: homopolymer, random copolymer, and impact-resistant copolymer, as well as modification directions such as transparency, irradiation stability, low precipitation, filling, glass fiber reinforcement, toughening, flame retardancy, low odor and low VOC, weather resistance, no spraying and scratch resistance; Also engaged in PP resin, sub-brand materials, and large package materials for major petrochemical plants
