You can bind it to a variable using v-bind:disabled="foo"
or :disabled="foo"
for short:
<textfield label="Name" value.sync="el.name" :disabled="myVar">
Then in Vue you can just set this.myVar = true
and it will disable the input.
Edit: add this to your template:
<template>
<input type="text" :disabled="disabled" :placeholder="placeholder" v-model="value">
</template>